Synthesis of Heterocyclic Dimers and Trimers Derived

SYNTHESIS OF HETEROCYCLIC DIMERS

DERIVED FROM

ISOFLAVONES AND FLAVONES

This thesis is submitted in fulfilment of the degree of

Doctor of Philosophy

MANDAR DEODHAR

Supervisors: Dr. Naresh Kumar

Prof. David StC. Black

School of Chemistry

The University of New South Wales

Kensington, Australia

July, 2007

i CERTIFICATE OF ORIGINALITY

I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person, nor material which to a substantial extent has been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis.

I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project’s design and conception or in style, presentation and linguistic expression is acknowledged.

Mandar Deodhar

ii ABSTRACT

The primary aim of this project was to synthesize new heterocyclic dimers of isoflavones and flavones, and investigate various methodologies for their synthesis.

The secondary aim of the project was to synthesize some flavonoid natural products.

Dimeric systems were synthesized using various methodologies including acid catalyzed arylation of isoflavanols and flavanols, acid catalyzed dimerization of flavenes, oxidative dimerization, Sonogashira coupling, Ullmann coupling and Suzuki-

Miyaura coupling reactions. The acid catalyzed arylation of isoflavanols was found to proceed in a very stereoselective fashion to give trans-4-arylisoflavans in good yield in a single step. However, related flavanols under similar conditions gave mixtures of cis and trans isomers of 4-arylflavans. Interestingly, it was found that appropriately substituted flavenes, upon treatment with acid undergo stereoselective rearrangement and dimerization to give benzopyranobenzopyrans in high yields. A rationale for the rearrangement is proposed and this dimerization was used for the stereoselective synthesis of the natural product dependensin. As part of the project, some polycyclic natural products such as octandrenolone, flemiculosin, 3-deoxy-MS-II and laxichalcone were also synthesized.

Oxidative dimerization of activated isoflavones was found to be very regioselective, and novel isoflavone dimeric systems were synthesized. Related flavones however, failed to undergo dimerization under similar conditions. A probable explanation for high regioselectivity in the case of isoflavones and unreactivity of flavones has been presented. Phenol oxidative coupling was used for the one-step synthesis of another natural product kudzuisoflavone-A from daidzein. Sonogashira coupling was utilized for the synthesis of dimeric systems linked via an acetylic linker. A variety of isoflavone- isoflavone, flavone-flavone and isoflavone-flavone dimers were synthesized in “one-

iii pot” by this methodology and in excellent yields. Although Ullmann coupling was found not to be suitable for the synthesis of isoflavone or flavone dimers, one-pot Suzuki-

Miyaura methodology gave flavone dimers and various other heterocyclic dimers in good yields.

iv ACKNOWLEDGEMENTS

This is by far the most important part of my thesis. I consider myself to be very fortunate to have had this opportunity to work with some of the most wonderful people in the world. It is with tremendous gratitude that I write these acknowledgements to show my appreciation to some of the most important people in my life.

First of all, I wish to express my deepest gratitude to my supervisor, Dr. Naresh Kumar.

I could not have imagined having a better advisor and mentor for my PhD. Thanks for giving me an opportunity to work on this exciting project, for giving me the freedom to develop my own ideas and for continuous guidance and help over the years. I will be indebted to him throughout my life.

I am exceptionally grateful to Prof. David StC Black for very helpful discussions, ideas and motivation throughout this project.

I cannot forget to mention the tremendous help from my supervisors at the time of visa application. Without their help it would have been impossible for me to come to

Australia.

I am thankful to all the academic staff of the School of Chemistry for constructive comments, good advice and encouragement. I would like to especially thank Dr.

Graham Ball and Dr. Jim Hook for their help with the NMR spectroscopy.

I want to express my heartfelt thanks to all the technical staff at UNSW. They do the behind the scenes work that makes it possible for us to conduct our research. Special thanks to Hilda Stender for all her cheerfulness and willingness to help with NMR spectrometer and Don Craig for the X-ray crystal structure. Thanks to Nick, Sarowar,

v Khaled, Lydia Morris and A/Prof. Gary Willet for mass spectrometry and to Marianne

Dick and Bob McAllister at the University of Otago for microanalysis determinations.

Thanks to Dr. Ron Haines for help with computers and to Ken McGuffin, Anne Jordan and Jodee Anning for help with the administrative matters.

I feel fortunate to have worked at UNSW and what made the time at the university so rewarding was the wonderful people I had a chance to work with. Most warmly I will remember Wade, Alam, Wai ching, Alex, Kittiya, Kasey, Taj, Frank, Rick, Daniel, Shari and seniors Dr. Able Salek, Dr. George Iskander, Dr. William Lao, Valentina Vignevich and Dr. Vi Nguyen. This is an amazing group of people, and I have benefited so much from all of our time together. Thanks to all, for your company and friendship, and for making my postgraduate time at UNSW enjoyable and memorable. Thanks to Dr.

Felicia Maharaj and Dr. Paulo Da Silva for helpful discussion about Palladium chemistry. Special thanks to Dr. Paulo Da Silva and Dr. Josephine Park for proof reading this thesis and thanks to Bradley, Douglas and Tamim for your friendship.

I cannot forget the time I spent at the Department of Chemistry, Maharaja Sayajirao

University, India. During this time, I was guided by some of the most inspiring people.

These are the people who helped me fall in love with chemistry. I am exceptionally grateful to all the academic staff at M. S. U. I would especially thank Prof. Surekha

Devi, Prof. S. M. Desai, Prof. K. B. Nair, Prof. R. H. Mehta, Prof. P. K. Bhattacharya and Prof. A.C. Shah. Thanks for making Chemistry very interesting and enjoyable.

Thanks to my previous supervisors in the pharmaceutical industry, Dr. R. C. Gupta for my first lessons in practical organic chemistry, Dr. Suhas Sohani for sharing his knowledge of stereochemistry and NMR spectroscopy, and Dr. Milind Gharpure for encouragement. I also thank my high school teachers and tutors most importantly, Mr.

vi Abhyankar, Mr. Kulkarni and Mr. Parekh for making chemistry the most interesting subject.

Many thanks to Dr. Andrew Heaton from Novogen for his support during the course of this project.

I owe a large debt of gratitude to my parents and my in-laws for their love, support, encouragement, patience and blessings. Special thanks to my best friend Dr. Vaibhav

Valodkar for being a source of inspiration and to Mr. Gadgil for his help and blessings.

Thanks to all the elders and well-wishers in the family for their blessings and support.

I cannot, however find words good enough to express my thanks and love to Medha, my best friend and wife, for all the love and support she has given me. I could not have finished this project without her.

IPRS scholarship from the Australian Government and UNSW during the three and half years is greatly acknowledged.

THANK YOU, to those who have helped with this thesis.

Finally, I dedicate this thesis to the most beautiful country on the planet AUSTRALIA.

vii TABLE OF CONTENTS

Page

Certificate of originality ii

Abstract iii

Acknowledgements v

Table of contents viii

Abbreviations xiv

Presentations and publications xvi

CHAPTER 1. INTRODUCTION

1.1. General introduction 2

1.1.1. Estrogens 2

1.1.2. Estrogen receptors (ERs) 3

1.1.3. Antiestrogens 4

1.1.3.1. Pure antiestrogens 4

1.1.3.2. Selective estrogen receptor 5

modulators (SERMs)

1.1.4. Phytoestrogens 7

1.1.5. Flavonoids 9

1.1.6. Biflavonoids 10

1.1.7. Biisoflavonoids 13

1.1.8. Limitations 15

viii 1.2.6 Aims of the present work 1

CHAPTER 2. SYNTHESIS OF 4-ARYLISOFLAVANS AND 4-ARYLFLAVANS

2.1.8 Introduction 1

2.1.1. Known synthetic methodologies 20

2.2.2 Results and discussion 2

2.2.1. Synthesis of 4-aryl and 4-heteroarylisoflavans 22

2.2.1.1. Synthesis of isoflavanol22

2.2.1.2. Synthesis of 4-arylisoflavans 23

2.2.1.3. Synthesis of 4-heteroarylisoflavans 2 9

2.2.2. Synthesis of 4-aryl and 4-heteroarylflavans 34

2.2.2.1. Synthesis of flavanol43

2.2.2.2. Synthesis of 4-arylflavans 37

2.2.2.3. Synthesis of 4-heteroarylflavans 40

2.3. Conclusion 41

CHAPTER 3. SYNTHESIS OF DIMERS BY ACID CATALYZED

DIMERIZATION OF FLAVENES

3.1.4 Introduction 4

3.2.5 Retrosynthesis of 4’,7-dihydroxyflav-3-ene 4

3.3.5 Results and discussion 4

ix 3.4.t Mechanism of the acid catalyzed rearrangemen 49

3.5.0 Synthesis of 4’,6-dihydroxyflav-3-ene and its attempted 5

dimerization

3.5.1. Retrosynthesis of 4’,6-dihydroxyflav-3-ene 50

3.5.2. Results and discussion 51

3.6.4 Synthesis of 4’,5-dihydroxyflav-3-ene 5

3.6.1. Retrosynthesis of 4’,5-dihydroxyflav-3-ene 54

3.6.2. Results and discussion 54

3.7. Conclusion 59

CHAPTER 4. SYNTHESIS OF SOME FLAVONOID NATURAL PRODUCTS

4.1.1 Synthesis of dependensin 6

4.1.1. Introduction 61

4.1.2. Retrosynthesis of dependensin 62

4.1.3. Results and discussion 63

4.1.4. Conclusion 65

4.2.6 Attempted synthesis of kamalachalcone-A 6

4.2.1. Introduction 66

4.2.2. Retrosynthesis of kamalachalcone-A 67

4.2.3. Results and discussion 68

4.2.4. Conclusion 78

x 4.3.9 Synthesis of flavonoid natural products 7

4.3.1. Introduction 79

4.3.2. Results and discussion 80

4.3.3. Conclusion 87

CHAPTER 5. SYNTHESIS OF DIMERS BY OXIDATIVE COUPLING REACTIONS

5.1.9 Introduction 8

5.2.9 General types of coupling mechanisms 8

5.2.1. Mechanisms involving free radical intermediates 90

5.2.2. Mechanisms involving non-radical intermediates 91

5.3.2 Results and discussion 9

5.3.1.2 Oxidative dimerization of daidzein 9

5.3.2.l Oxidative dimerization of phenoxodio 95

5.3.3. Oxidative dimerization of isoflavones 102

5.3.4.0 Oxidative dimerization of flavones 11

5.4. Conclusion 113

CHAPTER 6. SYNTHESIS OF DIMERS BY SONOGASHIRA COUPLING REACTIONS

6.1.6 Introduction 11

6.2.9 Results and discussion 11

xi 6.2.1. One-pot synthesis 120

6.2.2.2 Synthesis of isoflavone-isoflavone dimer 12

6.2.3.3 Synthesis of flavone-flavone dimers 12

6.2.4. Synthesis of heterocycle-heterocycle dimers 125

6.2.5.6 Synthesis of isoflavone-flavone dimers 12

6.3. Conclusion 128

CHAPTER 7. SYNTHESIS OF DIMERS BY ULLMANN AND SUZUKI-MIYAURA

COUPLING REACTIONS

7.1.0 Synthesis of dimers by Ullmann coupling reaction 13

7.1.1. Introduction 130

7.1.2.1 Known synthetic methodologies 13

7.1.3. Results and discussion 132

7.1.4. Conclusion 136

7.2. Synthesis of dimers by Suzuki-Miyaura coupling reactions 137

7.2.1. Introduction 137

7.2.2.0 One-pot Suzuki-Miyaura coupling reactions 14

7.2.3. Results and discussion 141

7.2.4. Conclusion 145

xii CHAPTER 8. EXPERIMENTAL

8.1.7 General information 14

8.2.9 Experimental details 14

CHAPTER 9. REFERENCES 257

APPENDIX X-ray crystallography data 276

Publications

xiii ABBREVIATIONS

Abs. absolute Ac acetyl

Ac2O acetic anhydride AcOH acetic acid AcONa sodium acetate a.m.u. atomic mass unit aq. aqueous Ar aryl

BF3·OEt2 boron trifluoride-diethyl etherate b.p. boiling point conc. concentrated CSA 10-camphorsulfonic acid DABCO 1,4-diazabicyclo[2.2.2]octane DBU 1,8-diazabicyclo[5.4.0]undec-7-ene DCM dichloromethane DIEA diisopropylethylamine DMA N,N-dimethylaniline DMF dimethylformamide DMSO dimethylsulfoxide DMTSF dimethyl(methylthio)sulfonium tetrafluoroborate EI electron impact ER estrogen receptor ERT estrogen replacement therapy ESI electrospray ionization Et ethyl

Et2O diethyl ether EtOH ethanol h hour(s) HCl hydrochloric acid HMBC heteronuclear multiple bond correlation HMQC heteronuclear multiple quantum correlation HRMS high resolution mass spectrometry IR infrared spectroscopy lit. literature M molar

xiv MALDI matrix assisted laser desorption ionization Me methyl MeI methyl iodide MEK methyl ethyl ketone MeO methoxy min minute mL milliliter(s) mmol milli mol MOM methoxymethyl NMP N-methylpyrrolidinone NMR nuclear magnetic resonance NOESY nuclear overhauser enhancement spectroscopy

Pd(PPh3)4 tetrakis(triphenylphosphene)palladium(0)

PdCl2(dppf) dichloro[1,1’-bis(diphenylphosphene)ferrocene]palladium(II)

PdCl2(PPh3)2 trans-dichlorobis(triphenylphosphene)palladium(II) PG protecting group Ph phenyl

PPh3 triphenylphosphene p-TSA p-toluenesulfonic acid r.t. room temperature SERMs selective estrogen receptor modulators TBAB tetrabutylammonium bromide TBAC tetrabutylammonium chloride TBAI tetrabutylammonium iodide TBDMSCl tert-butyldimethylsilyl chloride TEA triethylamine TFA trifluoroacetic acid TFAA trifluoroacetic anhydride THF tetrahydrofuran TLC thin layer chromatography TMS tetramethylsilane TMSCl trimethylsilyl chloride Triton-B benzyltrimethylammonium hydroxide Ts p-toluenesulfonyl TsCl p-toluenesulfonyl chloride TTFA thallium(III) trifluoroacetete UV ultraviolet spectroscopy

xv Presentations and publications

Deodhar, M.; Black, D. StC.; Kumar, N. Acid catalyzed stereoselective rearrangement and dimerization of flavenes: synthesis of dependensin. Tetrahedron 2007, 63, 5227-

5235.

Deodhar, M.; Black, D. StC.; Kumar, N. Synthesis of octandrenolone, flemiculosin, (±)-

3-deoxy-MS-II and laxichalcone. Org. Prep. Proced. Int. 2006, 38, 94-99.

Deodhar, M.; Black, D. StC.; Heaton A.; Kumar, N. Synthesis of dimeric flavonoids.

21st International Congress for Heterocyclic Chemistry, Sydney, NSW, 15-20 July,

2007. (Poster presentation)

Deodhar, M.; Black, D. StC.; Kumar, N. Synthesis of some flavonoid natural products.

RACI Natural Products Group Annual One-day Symposium, Sydney, NSW, 30

September 2005. (Oral presentation).

Deodhar, M.; Black, D. StC.; Kumar, N. Synthesis of dimeric flavonoids related to dependensin and its analogues. RACI Organic Chemistry Group Annual One-day

Symposium, Sydney, NSW, 30 November 2004. (Poster presentation).

xvi CHAPTER 1

INTRODUCTION

1 1.1. General introduction

Approximately 180,000 women are diagnosed with breast cancer each year in the US alone and most of these women are cured of their disease by surgery and local radiotherapy. However, nearly 60,000 women go on to develop metastatic breast cancer and 45,000 of these patients eventually die from their malignancies.1 Ovarian cancer is the fourth leading cause of cancer deaths among women and is responsible for more deaths than all other gynaecological malignancies combined. In the US, a woman’s lifetime risk of developing ovarian cancer is 1 in 70.2

Osteoporosis describes a group of diseases which are characterized by the loss of bone mineral density. There are estimated 25 million women in the US afflicted with this disease. Premenopausal women have less incidence of cardiovascular disease than the age-matched men. Following menopause, however, the rate of cardiovascular disease in women increases to match the rate seen in men.3

1.1.1. Estrogens

The increased incidences of cancer, osteoporosis and cardiovascular diseases have been linked to the loss of estrogens and in particular to the loss of estrogen’s ability to regulate the levels of serum lipids.

Me OH Me O Me OH OH

HO HO HO 1 2 3

Estrogens consisting of 17-estradiol 1, estrone 2 and estriol 3 are a family of naturally occurring steroid hormones that exert a physiological effect on the growth, development and maintenance of a diverse range of tissues. Estrone 2 and estriol 3 have

2 respectively one twelfth and one eightieth of estrogenic potency of estradiol 1. The major circulating estrogen in premenopausal women is estradiol 1, whereas in men and postmenopausal women it is estrone 2.

A mainstay of osteoporosis treatment to prevent bone loss in postmenopausal women is estrogen replacement therapy (ERT).4 Studies on the patients undertaking ERT suggest that estrogens such as 1 and 2 prevent bone loss and also possess a cardioprotective effect thereby reducing the risk of cardiovascular disease by about 50%.5

However, recent studies have suggested an increased risk of breast and uterine cancer associated with ERT and this has stimulated the search for alternative treatments.6-8

Thus, from a drug discovery point of view, there is a challenge to identify an estrogen mimetic that possesses the beneficial effects of estrogen and is devoid of the associated risks and negative side effects of ERT.4

1.1.2. Estrogen receptors (ERs)

The physiological effects of estrogens result from the binding of estrogens to the estrogen receptor (ER). The ER is a member of the nuclear hormone receptor (NR) superfamily and has multidomain architecture consisting minimally of N-terminal-DNA- binding domain (DBD), a ligand binding domain (LBD) and a C-terminal activation

9,10 domain. The ERs are further classified into two subtypes, ER and ER. These receptor subtypes are related in both structure and function but have somewhat

11-13 9 different tissue distribution. Several forms of human ER known as ER short, ER

14 14 long and ERCx have been identified. Upon ligand binding, ER experiences a conformational change to initiate a cascade of regulatory events with its target genes.15

The fact that ligands of remarkable structural diversity e.g. steroidal analogues, nonsteroidal compounds such as stilbenes, triarylethylenes, phenylindoles, phenylindenes and coumarins bind to the ER in many cases with good affinity has remained a curiosity for many years.16 From the comparative QSAR analysis of ER ligands, a phenolic

3 hydroxyl group which mimics the 3-OH on the ring-A of estrogens appears to be the most important factor in receptor-ligand interaction.16

1.1.3. Antiestrogens

Antiestrogens are compounds that are structurally analogous to estrogens and are capable of binding to the ER. They act by blocking the receptor and decreasing the estrogen activity associated with tumour growth.17 The blockade of estrogen action is a major approach for the treatment of hormone-dependent breast cancer.18

Antiestrogens are divided into two groups according to their mechanism of action:17,19 i) pure antiestrogens and ii) partial antiestrogens or selective estrogen receptor modulators (SERMs).

1.1.3.1. Pure antiestrogens

Pure antiestrogens in contrast to SERMs which show both antagonist and agonist actions, only produce estrogen antagonist action and no estrogen agonist action, and hence they do not induce hyperplasia of the endometrium. Therefore, these agents also do not possess the positive properties of SERMs such as the ability to preserve bone mineral density and reduced blood cholesterol levels.19-21 They are further subdivided into two categories: i) steroidal such as Faslodex 4, EM-139 5 and ICI 164384 6 and ii) non-steroidal such as EM-800 7 and EM-652 8.

Me OH Me OH

O O HO S CF2CF3 HO 9 10 N C H 4 3 4 9 5 R = Cl Me 6 R = H

OR Me

RO O N O

7 R = COC(CH3)3 8 R = H

Faslodex 4 is the only pure antiestrogen that has successfully passed the phase III clinical trials for hormone dependent breast cancer.

1.1.3.2. Selective estrogen receptor modulators (SERMs)

The acronym SERM was invented by Eli Lilly in the 1990s to describe the multiplicity of effects from molecules that interact with the ER at different sites. SERMs are synthetic compounds that bind to the ER protein and act like an estrogen antagonist on the ERs in the uterine and mammary tissue, while acting as agonists in receptor sites associated with bone and cardiovascular systems.22-26

Tamoxifen 9 was developed in the 1960s as an estrogen antagonist and showed 38% reduction in breast-cancer incidence.27 It was first used in clinical practice to inhibit the proliferative actions of estrogen on the breast,6,28-31 and was able to antagonise the growth of some hormone dependent tumours, particularly breast cancer.28,32-36

Tamoxifen 9 was also effective against menstrual disorders and found to display estrogen agonist effect on the bone37,38 and cardiovascular system.39 Its mode of action was thought to be mainly as a competitor against 17-estradiol 1 for the ER.28

N N O O 9 10

5 Tamoxifen 9 also reduces the risk of ER-positive28,40 breast cancers by 48%, however, new approaches are still needed to prevent ER-negative breast cancers27,28,40-42 and to minimise the side effects associated with its use. Tamoxifen 9 increases the risk of endometrial cancers due to its partial agonist activity in the uterus.43-45 Prolonged usage of tamoxifen 9 has been shown to result in the formation of tumours that are tamoxifen- resistant or tamoxifen stimulated, resulting in recurrence of this disease.42 However, it has also been shown that patients who have taken tamoxifen 9 for over a five-year period46-48 demonstrate a prolonged disease-free period with greater overall survival.48

(Z)-3-Hydroxytamoxifen (Droloxifene) 10 which is a metabolite of 9 is also a potent antiestrogen28,49,50 that binds to the ER with 100 times51 greater affinity than 9 and its binding affinity is comparable to 17-estradiol 1.52 It was developed for the treatment of osteoporosis in postmenopausal women.19,53

Some of the tamoxifen analogues obtained by introducing iodine, bromine, chlorine, ethyl, aryl, alkyl or amino groups into the tamoxifen skeleton show significant pharmacological activity.45

N N O O 11 12

Toremifene 11 exhibits antiestrogen and antitumour properties. It also reduces liver damage and has less pronounced carcinogenicity on the endometrium compared to tamoxifen 9.19,54,55

Iodoxifen 12 is a 4-iodophenyl derivative of tamoxifen 9 and was specifically developed for treatment of patients acquiring resistance to tamoxifen 9.19,53

6 O N

OH HO S 13

Reloxifene 13 prevented ovariectomy (OVX) induced bone loss in the rat and lowered serum cholesterol with no significant proliferative effects on the endometrium. In addition, it potentially inhibited56 estrogen’s proliferative actions on MCF-7 cells, a human breast cancer cell line. In clinical studies,57 it increased total body bone density and lowered levels of low density lipoproteins (LDL). However, due to extensive glucuronidation58 in animals59 and humans,60 the systemic bioavailability of reloxifene during oral administration is rather limited.

1.1.4. Phytoestrogens

Epidemiological studies have shown that people of Asian cultures consuming a diet rich in soy, have lower rates of osteoporosis, menopausal symptoms, cardiovascular diseases and select endocrine cancers compared to people of Western cultures.61,62

Phytoestrogens in soy are considered to be the reason for this difference.

Phytoestrogens are a diverse group of nonsteroidal plant compounds that can behave as estrogens due to the presence of a phenolic hydroxyl group which enables them to bind to the estrogen receptor. A short term study where patients were given a phytoestrogen rich diet demonstrated a weak estrogenic response on the breast and no antiestrogenic effects were detected.63 However, some contradictory evidence suggesting proliferation of mammary glands64 and breast tumour cells lines65,66 has been observed. It has been shown that phytoestrogens inhibit the proliferation of breast cancer cells in vitro.67-69

7 The estrogenic activity of phytoestrogens is dependent upon their interaction with ER and ER. In most systems, the relative binding affinities for ER are greater than that for

70 ER. Despite their ability to bind to the estrogen receptors, phytoestrogens are much weaker than human estrogens, with 102 to 105 times less activity.71 However, this is compensated by the fact that they are frequently present in the body in much higher quantities than endogenously produced estrogens.72

The proposed mechanisms by which they may inhibit cancer cells include : i) inhibition of DNA topoisomerase, ii) suppression of angiogenesis, iii) induction of differentiation in cancer cell lines and iv) induction of apoptosis.73,74

Phytoestrogens

Flavonoid Non-flavonoid

Isoflavones Flavones Coumestans

OH OH OH O OH O O

HO O HO O HO O O

14 15 OH 16

Lignans Macrolides Stilbenes

OH HO OH O O HO O O HO OH O OH 17 18 19

Figure 1

8 The phytoestrogens are divided into two main groups (Figure 1):73,75,76 i) flavonoid and ii) non-flavonoid phytoestrogens.

The flavonoid phytoestrogens are further classified into, a) isoflavones e.g. Genistein 14, b) flavones e.g. apigenin 15, and c) coumestans e.g. coumastrol 16.

The non-flavonoid phytoestrogens are further classified into, a) lignans e.g. enterolactone 17, b) macrolides e.g. zearalenone 18, and c) stilbenes e.g. resveratrol 19.

Isoflavones are the most commonly studied phytoestrogens because they possess the highest estrogenic properties.73

1.1.5. Flavonoids

The flavonoids are a very well known family of natural products.77-79 They are found exclusively in the plant kingdom and play a vital role in the ecology of plants.

Flavonoids are widely distributed in the human diet and occur primarily in plant-derived foods and beverages. Green tea, cocoa, soybeans and chocolate are the rich sources of flavonoids. Over the last few years they have received considerable attention on account of their medicinal properties,80 such as antioxidant,81 anti-inflammatory,82 gastroprotective,83 antiviral,84 antimutagenic,85 topoisomerase II inhibitory,86 protein kinase C inhibitory87 and cytotoxic activities.88-90

9 The flavonoids are broadly classified into the following categories (Figure 2).

4' 5' 3' 3' B

O O 2' 4' 6' 2' 5 5 B 4 5' 6 3 6 5 3 3 A C 2' A C 6' A C 7 2 O 2 3' 7 O 2 7 O 8 B 8 8 6' 4' 20 5' 21 22

O O 5 4 4 6' OH 1' 6 3 5 5' A C 2' A A 2 2 6 2' 4' 3 7 O 2 3' O 2' OH 8 B 7 3' B 6' 3' 6' 4' B 6 4 23 5' 24 5' 4' 25 5

Figure 2

In flavones 20, ring–B is attached to ring-C at the C2 position, whereas in isoflavones

21, ring–B is attached at the C3 position; in neoflavonoids 22, this attachment is via the

C4 position. Anthocyanines 23 are made up of a charged flavylium structures whereas aurones 24 have a five membered ring with an exocyclic double bond at the C2 position. Chalcones 25 on the other hand have only two aromatic rings joined together via an ,-unsaturated ketone. Thus, flavone 20 and isoflavone 21 are regioisomers.

However, such a subtle difference in their structures gives rise to significant differences in their reactivity and methodologies required for their synthesis.

In addition to these compounds, many natural flavonoids also exist as dimers, trimers and oligomers in which the above mentioned classes are coupled together at various positions.

1.1.6. Biflavonoids

Biflavonoids are a series of naturally occurring compounds that include flavone-flavone, flavanone-flavone and flavanone-flavanone units linked to each other. They are further classified into two groups: i) the biphenyl type in which the two units are linked through

10 a carbon-carbon bond, and ii) the biphenyl ether type in which the linkage is through an oxygen atom. So far, more than 100 biflavonoid compounds have been isolated from various plants and a variety of biological activities associated with them have been published.91,92

Robustaflavone 26 and hinoidflavone 27 are examples of novel non-nucleoside natural products which possess impressive activity against hepatitis B virus (HBV) replication.

Robustaflavone 26 acts via inhibition of HBV DNA polymerase and complements the currently used drugs which are all nucleotide analogues.91

5''' 6''' OH OH O 8'' HO O 6 3''' 3 2'' 2''' 2 2' 6'' 3'' 3' HO 8 O OH O 6' 26 5' OH OH O 5''' 6''' 4'''O 6 3 8'' 2' HO O 2 HO O 3' 2'' 8 3'' 6' 6'' OH 27 5' OH O

In robustaflavone 26 two apigenin molecules 15 are directly attached to each other via the C6 of one apigenin molecule to the C3’’’ of the other apigenin molecule, whereas in hinoidflavone 27, the C6 and C4’’’ carbons are linked together via an oxygen atom.

The rapid spread of tuberculosis worldwide has highlighted the need to develop more

OH OMe O O HO MeO OH O OMe O O O

HO O MeO O

OH OH OMe OMe 28 29

11 efficient drugs to combat this disease. Biflavonoid 28 and its hexamethyl ether 29 in which two naringenin 30 molecules are attached via a C3-C8’’ linkage show potent antitubercular activity.93

OH O

HO O 30 OH

Sikokianins B 31 and C 32, which are C3-C3’’ dimers of naringenin 30, show potent antimalarial activity against chloroquine resistant strains of Plasmodium falciparum.94

OMe OMe H H HO O HO O O OH O OH H H H H OH O OH O O OH O OH H H HO HO 31 32

Compound 33 shows potent anti-inflammatory activity.95 In this molecule, the two flavonoid units are attached to each other by both C-C and C-O linkages. Additionally, it contains a sugar molecule attached to the C7 hydroxyl of one of the flavonoid units.

OH HO MeO OMe OMe H O MeO O OMe HH O OH O

OH OMe H OH OH O OH OH O O O OH 33 OH 34

Dependensin 34 has a unique structure which contains two flavonoid molecules fused to each other. The crude extract of Uvaria dependens containing dependensin 34 shows potent antimalarial activity. 96

12 1.1.7. Biisoflavonoids

Biisoflavonoids are naturally occurring compounds that contain two isoflavone molecules attached to each other. Like their biflavonoid counterparts, biisoflavonoids are also further classified into two groups: i) the biphenyl type, in which the two units are linked through a carbon-carbon bond, and ii) the biphenyl ether type, in which the linkage is through an oxygen atom. However, unlike biflavonoids, biisoflavonoids are much less known in the literature.

Kudzuisoflavones A 35, B 36 and C 37 were isolated upon treatment of P. lobata cell cultures with an elicitor yeast extract.97 It was further proposed that these metabolites are probably formed by non-specific oxidation of daidzein 38 with peroxidase.

OH O OH O

O O OH HO O HO 35 OH O

O O

HO O 36

O O OH O O O HO O O HO O 38

HO 37

Compounds 36, 39, 40 and 41 show 5-reductase inhibitor activity, and hence find use in the treatment of prostate hyperplasia.98 Biisoflavonoid 35 contains two daidzein molecules 38 attached to each other via an oxygen atom whereas in 39 the daidzein 38 and genistein 14 molecules are directly attached to each other via a C3’-C3’’’ linkage.

13 OH O OH O

O OH HO O HO 39

OH O OH OH O

O OH HO O HO OH OH 40 OH O OH O

HO O HO O 41

Compounds 40 and 41 have two genistein 14 molecules attached to each other in a symmetrical (C3’-C3’’’) and unsymmetrical manner (C3’-C6) respectively.

Kumar and Heaton have demonstrated that dimeric isoflavonoid compounds with the general formulae as depicted in 42 and 43 show potent anticancer activity in a variety of cancer cell lines.99

R R R R R O

R O R O R= OH, acetoxy 42 43

Biisoflavonoid 44 was isolated from the heartwood of Platymiscium floribundum, and showed cytotoxic activity against five human cancer cell lines in vitro.100

14 MeO OMe O OMe OMe O

OH O O O 44

Tang et al.101 isolated dehydrohexaspermone C 45 from Ochna macrocalyx together with other anticancer and antibacterial compounds while five biisoflavonoids 46-50 were isolated from the heartwood of D. odorifera.102

MeO O OH

H MeO O O OMe H

O OMe 45

MeO O R3O R1 MeO O O

OMe OMe

OMe R2 OMe O

OH OH HO O HO O 50 46 R1 = OH, R2, R3 = H 47 R1, R2, R3 = H 48 R1, R3 = H, R2 = OMe 49 R1 = OH, R2 = H, R3 = OMe

1.1.8. Limitations

Although there are several examples of naturally occurring dimeric flavonoids with potent activity against several ailments, their use as medicaments has been severely limited due to : i) low abundance of these compounds in the plant material, ii) tedious methods of extraction and purification which often require extraction with very large quantities of solvents, and multiple chromatographic purifications, occasionally including HPLC purifications, and iii) unavailability of appropriate biological data.

15 For example, isolation of just 5.6 g of robustaflavone 26 required extraction of 16 kg of powdered seeds of Rhus succedanea using 150 litres of ethanol and three chromatographic purifications using solvent systems containing pyridine and formic acid, followed by crystallization from pyridine.91

One of the possible solutions to these problems is the development of efficient synthetic methodologies which could generate not only the natural products but also their synthetic analogues.

1.2. Aims of the present work

Although there are several examples of naturally occurring biflavonoids and biisoflavonoids, the dimeric compounds consisting of a flavone or isoflavone and a heterocyclic compound like an indole, benzofuran or chromene are not known in the literature. Furthermore, heterocyclic dimers containing one flavone and one isoflavone molecules have not been reported in the literature.

Therefore, the aim of the present work was: i) to synthesize new heterocyclic dimers, particularly i) isoflavone-heterocycle, flavone-heterocycle and isoflavone-flavone dimers and ii) to investigate various methodologies for their synthesis.

Another aim of the present work was to develop methodologies for the synthesis of some naturally occurring dimeric flavonoids.

16 CHAPTER 2

SYNTHESIS OF

4-ARYLISOFLAVANS AND

4-ARYLFLAVANS

17 2.1. Introduction

Nonsteroidal ligands for the ER such as tamoxifen 9, raloxifene 13, centchroman103 51 and diphenylbenzofuran104 52 as shown in figure 3 exhibit a recognizable structural pattern.

N O O N

OH HO S 9 13

N O OH

OH MeO O HO O

51 52 Figure 3

This pattern shown in figure 4 consists of a core structure A onto which other, peripheral structural elements such as a phenolic unit (B), second aromatic group (C) and another substituent (D) which may be aromatic are attached. In the case of ER antagonists or mixed agonist/antagonist, one of the substituents generally contains a basic or polar functionality.105,106

Substituent D (aromatic)

Second aromatic group C HO

Phenol B Core structure A (A double bond, aryl or heteroaryl ring)

Figure 4

18 As discussed in section 1.1.7., Kumar et al.99 have shown that a new class of dimeric isoflavone compounds with the general formulae as depicted in 42 and 43, show strong binding affinity for estrogen receptors and hence exhibit remarkable physiological activity. For example dimeric compound 53 shows potent anticancer activity against a variety of cancer cell lines (Table 1).99

O OH

OH HO

HO O 53

Cell Line MCF-7 PC3 C6 KyM-1 NCI-H460 NCI-H23

IC50 (µM) 18±2 13.5 17.5 3.2 14.4 13.5

Table 1

Similar biologically active compounds can be found in the 4-arylflavan series as well.

For example myristinins B 54, C 55, E 56 and F 57 possess antifungal and selective

COX-2 inhibitor activities, whereas Hecht et al.107 have described compounds 55 and

57 as potent DNA polymerase inhibitors.

OH O O OH R R 8 8 HO OH HO OH

HO O HO O

OH OH

54 R = CH2CH2CH3 56 R = CH2CH2CH3 55 R = Ph 57 R = Ph

19 Therefore, synthesis of a series of 4-aryl and 4-heteroaryl substituted isoflavans e.g. compound 58 and 4-aryl and 4-heteroaryl substituted flavans e.g. compound 59 was undertaken.

OH R R

HO O HO O 59 58 OH R = Aryl or Heteroaryl

2.1.1. Known synthetic methodologies

Synthesis of 4-Arylisoflavans have been reported by Carney et al.108 who demonstrated that reaction of isoflavanol 60 with phenol in the presence of AlCl3 gives isoflavan 61 as one of the products (Scheme 1). However, the yield of the reaction was not reported.

Cl Cl OH OH

AlCl3 benzene O O 60 61 One of the products Scheme 1

The corresponding cis isomer 64 was synthesized by reacting isoflavanone 62 with p- methoxyphenylmagnesium bromide, followed by dehydration to give the intermediate isoflavene 63. Catalytic hydrogenation and demethylation of compound 63 gave isoflavan 64 (Scheme 2).

OMe OH

Cl Cl Cl O

1) p-MeOC6H4MgBr 1) H2, Pd/C, 70% 2) dehydration 2) py·HCl, heat O O O 29% 74% 62 63 64

Scheme 2

20 Reaction of 4-haloflavans with the potassium salt of phenolic compounds in refluxing dioxane has also been reported to give cis-4-arylflavans. For example, reaction of 4- chloroflavan 65 with potassium p-cresolate gave flavan 66 as a minor product (Scheme

3).109 Me

Cl OH

p-MeC6H4O K dioxane, 45°C O O

OMe OMe 65 66 Minor product

Scheme 3

Ferreira et al.110 have reported that 4-arylflavans such as 69 can be prepared under neutral conditions from 4-benzylthioflavan 67 and flavan 68 in the presence of dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF) or silver tetrafluoroborate

(Scheme 4).

OH OH

HO O OH 68 OH OH OH HO DMTSF or O CH Ph OH OH S 2 OH AgBF4 OH OH OH HO O HO O OH 67 OH 69 OH OH Scheme 4

However, these methodologies can not be easily adopted for the synthesis of highly oxygenated flavones or isoflavones due to their low yields. The oxygenation pattern is very important for biological activity.

21 2.2. Results and discussion

2.2.1. Synthesis of 4-aryl and 4-heteroarylisoflavans

The retrosynthetic analysis shows that 4-aryl and 4-heteroarylisoflavans 58 can be synthesized by the reaction of activated aromatic or heteroaromatic compounds with

OH OPG OPG R OH

HO O PGO O PGO O 58 70 71

Activated aromatic or heteroaromatic compound

Scheme 5 carbocation 70, which in turn can be obtained from reaction of isoflavan-4-ol 71 with a

Lewis acid (Scheme 5). Protection of the phenolic hydroxyl groups would be necessary to avoid self coupling of the starting isoflavanols.

Another possible side reaction is that carbocation 70 might undergo elimination to give isoflavene as a by-product.

2.2.1.1. Synthesis of isoflavanol

The diacetoxyisoflavanol 76 was synthesized in four steps using standard isoflavone synthesis as outlined in Scheme 6.

Resorcinol 72 was reacted with 4-hydroxyphenylacetic acid 73 in the presence of boron

111 trifluoride-diethyl etherate (BF3·OEt2) to give deoxybenzoin 74 in 73% yield.

Deoxybenzoin 74 was cyclized by heating it with triethyl orthoformate in the presence of pyridine and piperidine to give daidzein 38 in 67% yield.111 Acetylation using acetic anhydride/pyridine followed by catalytic hydrogenation with palladium on carbon gave

4’,7-diacetoxyisoflavan-4-ol 76 as a 2:1 cis:trans mixture of isomers as determined by

1H NMR spectroscopy. The mixture was not separated and was used further without 22 purification.

O OH OH OH O

BF3·OEt2 110°C, 73% HO HO OH OH (EtO)3CH pyridine piperidine 120°C 72 73 74 67% OAc OAc OH OH O O

H2, Pd/C, EtOH Ac2O, pyridine AcO O 90% AcO O 110°C, 90%HO O 76 75 38 cis:trans 2:1

Scheme 6

2.2.1.2. Synthesis of 4-arylisoflavans

Isoflavanol 76 was reacted with 2’-hydroxy-6’-methoxyacetophenone 77 in the presence of BF3·OEt2 at r.t. for 1 h. After aqueous work-up the crude product was chromatographed to give isoflavan 78 in 67% yield (Scheme 7).

O OMe O OMe

OAc J = 7.2 Hz OH OH HO H HO H 77, BF3·OEt2 1M KOH, MeOH DCM, 67% 84% AcO O AcO O OAc HO O 76 78 79 Scheme 7

The trans stereochemistry of the product was established on the basis of the coupling constant of 7.2 Hz between H3 and H4 and more importantly the absence of NOE

(Figure 5) correlation between the H3 and H4 protons. In addition to this, the methoxy group showed NOE to the adjacent aromatic proton thus ruling out substitution ortho to the methoxy group. This established that the acetophenone 77 was attached to the C4 carbon of isoflavan through the C3 position.

O OMe H

HO H H H OAc

AcO O NOE Important NOEs for 78 Figure 5

Figure 6 shows an energy minimized Chem3D structure of intermediate carbocation.

The exclusive formation of the trans product in this reaction can be explained by the fact that although the carbocation is flat, the presence of the aryl group at the C3 position of the intermediate carbocation prevents the attack of the incoming nucleophile from the same side due to steric hindrance. This results in the attack from the opposite side of the C3 aryl group giving rise to the trans product exclusively.

Nucleophile (Highly hindered) H cis OAc attack H AcO O

H trans attack

Nucleophile (Less hindered)

Figure 6

Compound 78 was hydrolysed using 1M KOH solution to give the 4’,7-dihydroxy compound 79 in 84% yield.

Thus, the BF3·OEt2 catalyzed arylation reaction is stereoselective and although the starting material diacetoxyisoflavanol 76 is a mixture of cis/trans isomers, only the trans product is obtained in good yield. With these encouraging results it was decided to extend the reaction to some other activated phenolic compounds.

24 Isoflavanol 76 was reacted with 2’-hydroxy-4’-methoxyacetophenone 80 under similar conditions. In this case the reaction did not go to completion even on addition of twice the amount of BF3·OEt2 and extended reaction time. Interestingly, in this case the reaction was observed at C5’’ position which is para to the hydroxyl group and ortho to the methoxy group. The reason for this is that the C3’’ position is highly hindered due to the presence of bulky methoxy and hydroxyl groups on the adjacent carbons. The product 81 was obtained in 28% yield (Scheme 8).

OH O OH O

3'' 5' OAc 6'' OAc OH OH MeO 5'' MeO

80, BF3·OEt2 4 1M KOH, MeOH 2' DCM, 28% 95% AcO O AcO O 2 HO O 76 81 82 Scheme 8

The 1H NMR spectrum of compound 81 showed multiplets at 3.30 (1H) and 4.29 (2H) corresponded to H3 and two H2 protons respectively whereas the H4 protons appeared as doublet at 4.55 (J = 7.2 Hz). The H5’’ and H2’’ protons appeared as singlets at

6.33 and 7.12 respectively. Again the reaction was found to proceed stereoselectively leading to the trans product 81. Isoflavan 81 was then hydrolysed with 1M KOH to afford the hydroxy compound 82 in 95% yield (Scheme 8).

A similar reaction with phenol gave isoflavan 83 (Scheme 9). The structure was established on the basis of 1H NMR spectroscopy which showed two pairs of doublets with a coupling constant of 8.3 Hz which indicated the presence of two para substituted benzene rings. The regioselectivity in this case is attributed to the mild reaction conditions which favour reaction at the unhindered C4 position of phenol over the C2 and C6 positions. Upon hydrolysis of isoflavan 83, compound 84 was isolated in 95% yield.

25 OH OH

OAc OH

phenol, BF3·OEt2 1M KOH, MeOH 76 DCM, 28% 95% AcO O HO O 83 84 Scheme 9

The BF3·OEt2 catalyzed reaction of isoflavanol 76 with highly substituted phenolic compounds gave mixtures of atropisomeric products which have the same Rf values in thin layer chromatography using a number of solvent systems and therefore could not be separated.

For example, reaction of isoflavanol 76 with 3,5-dimethoxyphenol 85 gave isoflavan 86 as a mixture of atropisomers in 46% yield, and hydrolysis of this gave compound 87 in

64% yield (Scheme 10).

OMe OMe

5'' 3''

MeO 1'' OH MeO OH 85, BF ·OEt 1M KOH, MeOH 76 3 2 4 OAc OH DCM, 46% 64% 2' 3' AcO O HO O 86 87 Scheme 10

Since compound 86 has bulky substituents at the 2’’ and 6’’ positions, the rotation around the C4-C1’’ bond is restricted (Figure 7). The atropisomerism caused broadening of some of the peaks in the 1H NMR spectrum, in particular the 6’’-MeO,

H5, H2’ and H6’ protons. In the 13C NMR spectrum of isoflavans 86 and 87 extra peaks for some of the carbon atoms were also observed. These are shown in brackets in the

13C NMR data.

26 OMe OMe

MeO OH MeO OH H H OAc OAc

AcO O AcO O

Figure 7. Atropisomers of compound 86

Atropisomers were also observed in the reactions of 3,4,5-trimethoxyphenol 88 and 2- naphthol 91 with isoflavanol 76 (Scheme 11).

OMe OMe MeO MeO

MeO OH MeO OH

88, BF3·OEt2 1M KOH, MeOH 76 OAc OH DCM, 81% 68% AcO O HO O 89 90 1:2 mixture of atropisomers

OH OH 91, BF ·OEt 1M KOH, MeOH OH 76 3 2 OAc DCM, 65% 80% AcO O HO O 92 93 1:1.1 mixture of atropisomers Scheme 11

The reaction of compound 76 with anisole was sluggish and gave a 1.5:1 mixture of expected product 94 and dehydration product isoflav-3-ene 95 (Scheme 12). Since these compounds had similar Rf values on TLC in several different solvent systems, they could not be separated by column chromatography.

27 OMe

OAc OAc

anisole, BF3·OEt2 76 DCM AcO O AcO O 94 95 1.5:1 mixture

Scheme 12

Compound 94 could be synthesized more efficiently by methylation of isoflavan 83 with dimethyl sulfate and K2CO3. Hydrolysis of isoflavan 94 gave the desired dihydroxyisoflavan 96 in 80% yield (Scheme 13).

OMe OMe

OAc OH

Me SO , K CO 1M KOH, MeOH 83 2 4 2 3 acetone, reflux 80% 65% AcO O HO O 94 96 Scheme 13

With other phenolic substrates such as 3-methylcatechol 97 and 1-naphthol 98, a complex mixture was obtained which could not be separated, whereas attempted reactions with phloroglucinol 99 and pyrogallol 100 were unsuccessful due to their insolubility in dichloromethane (Scheme 14).

3-methylcatechol 97 or -naphthol 98 Complex mixture BF3·OEt2, DCM

76 phloroglucinol 99 or pyrogallol 100 No reaction BF3·OEt2, DCM Scheme 14

With these results in hand, reactions of isoflavanol 76 with some activated heterocyclic compounds such as benzofurans, indoles and isoflavenes were investigated.

28 2.2.1.3. Synthesis of 4-heteroarylisoflavans

The various heterocyclic compounds required for the arylation reactions were synthesized following the reported procedures.

Benzofuran 103 was synthesized by the reaction of 3,5-dimethoxyphenol 85 with 4- bromophenacylbromide 101, followed by cyclization of the resulting intermediate 102 with trifluoroacetic acid (TFA) (Scheme 15).112

Br Br Br

OMe OMe OMe O O KHCO3, acetone TFA, r.t. reflux, 66% 62% MeO OH Br MeO O MeO O 85 101 102 103 Scheme 15

Reaction of 3,5-dimethoxyaniline 104 with benzoin 105 in the presence of aniline and acetic acid gave 4,6-dimethoxy-2,3-diphenylindole 106 in a single step in 63% yield

(Scheme 16).113

OMe OMe O i) 125°C, 1h ii) PhNH , AcOH MeO NH2 HO 2 N 125°C, 63% MeO H 104 105 106

Scheme 16

4,6-Dimethoxy-3-(4’-bromophenyl)indole 110 was synthesized by a modified Bischler indole synthesis from 3,5-dimethoxyaniline 104 in four steps (Scheme 17).114 In the first step, aniline 104 was condensed with 4-bromophenacylbromide 101 to give compound

107 which on acetylation with acetic anhydride gave N-acyl compound 108. Cyclization was carried out by refluxing compound 108 with trifluoroacetic acid (TFA) to give N- acetylindole 109 which on hydrolysis with methanolic KOH gave indole 110.

29 Br Br Br OMe OMe OMe O O O NaHCO3, EtOH Ac2O, 50°C reflux, 95% 89% MeO NH2 Br MeO N MeO N H Ac 104 101 107 108

Br Br

OMe OMe

KOH, MeOH TFA r.t., 75% reflux, 94% MeO N MeO N H Ac 110 109 Scheme 17

4’,7-Dimethoxyisoflav-3-ene 112 was synthesized in 93% yield by the methylation of

4’,7-dihydroxyisoflav-3-ene (Phenoxodiol) 111 with methyl iodide in the presence of

K2CO3 (Scheme 18).

OH OMe

MeI, K2CO3 acetone, reflux HO O MeO O 93% 111 112 Scheme 18

When isoflavanol 76 was reacted with benzofuran 103, 4-(benzofuran-2-yl)isoflavan

113 was obtained in 43% yield which upon hydrolysis gave the phenolic compound 114 in 83% yield (Scheme 19).

MeO OMe MeO OMe

Br Br O O 103, BF ·OEt 1M KOH, MeOH 76 3 2 OAc OH DCM, 43% 83% AcO O HO O 113 114 Scheme 19

30 The structure and the trans stereochemistry of compound 114 was confirmed by X-ray crystal structure determination as shown in Figure 8. The solvent molecules are omitted for clarity.

Figure 8

Compound 114 crystallizes in a monoclinic space group P 21/c. A selection of important torsional angles for compound 114 is given in Table 2.

Selected torsional angles for compound 114

Torsional angles [°]

H1C11-C11-C10-HC10 67.3

H2C11-C11-C10-HC10 173.7

HC9-C9-C10-HC10 178.4

C9-C10-C11-O2 62.5

C1-C9-C10-HC10 61.9

C16-C9-C10-C11 53.6

C12-O2-C11-C10 37.6

Table 2

31 The reaction of compound 76 with indole 106 gave 4-(indol-7-yl)isoflavan 115 in 75% yield as a mixture of atropisomers, which upon hydrolysis gave dihydroxyisoflavan 116 in 80% yield. Interestingly, 4’,6-dimethoxyisoflav-3-ene 112 gave isoflavan 117 in 77% which upon hydrolysis gave compound 118 in 74% yield (Scheme 20).

OMe OMe

MeO N MeO N H H 106, BF3·OEt2 1M KOH, MeOH OAc OH DCM, 75% 80% AcO O HO O 115 116

76 O O OMe OMe MeO MeO

112, BF3·OEt2 1M KOH, MeOH OAc OH DCM, 77% 74% AcO O HO O 117 118 Scheme 20

When the reaction was attempted with 4’,7-dihydroxyisoflav-3-ene 111, compound 119 was obtained in 35% yield. Attempts to deprotect the acetoxy groups under alkaline conditions gave a complex mixture of products which could not be separated. No reaction was observed when 7-acetoxyisoflav-3-ene 120 was used as a substrate, presumably due to insufficient activation of the ring-A by the 7-acetoxy group (Scheme

21).

O OH HO

111, BF3·OEt2 OAc 1M KOH, MeOH Complex DCM, r.t. r.t. mixture 35% AcO O 76 119

120, BF3·OEt2 No reaction DCM, r.t. Scheme 21

32 OMe OMe

OMe OMe

AcO N HO O O H Me Me 120 121 122

Reactions of compound 76 with some other activated heterocyclic substrates such as

3-arylindoles 109, 110, unsubstituted indole 121, and hydroxyisoflavene 122, gave complex mixtures which could not be separated by column chromatography (Scheme

22).

109, BF3·OEt2 DCM, r.t.

110, BF3·OEt2 DCM, r.t. Complex 76 mixture

121, BF3·OEt2 DCM, r.t.

122, BF3·OEt2 DCM, r.t.

Scheme 22

The reason for this could be the fact that compared to their benzofuran counterparts, the unsubstituted indole 121 and the 3-substituted indoles 109, 110 are more reactive.

Therefore, the reaction could occur at more than one reactive site. Another reason could be that indoles readily undergo acid-catalyzed dimerization reactions which could give rise to the formation of multiple products.

Thus, acid catalyzed arylation and heteroarylation using isoflavanol is an excellent method for the synthesis of 4-aryl and 4-heteroarylisoflavans. The reaction is highly stereoselective and gives trans products exclusively in good yield.

With these encouraging results, this methodology was extended to the synthesis of 4- arylflavans.

33 2.2.2. Synthesis of 4-aryl and 4-heteroarylflavans

It was hypothesized that 4-aryl and 4-heteroarylflavans 59 could be synthesized by condensation of protected flavanol 128 with the activated aryl or heteroaryl compounds.

The flavanol 128 can be synthesized by acetylation and reduction of flavanone 126 which in turn can be synthesized from resacetophenone 123 (Scheme 23).

R OH

HO O AcO O 59 128 OH OAc

O O

HO OH HO O 123 126 OH

Scheme 23

2.2.2.1. Synthesis of flavanol

4,2’,4’-Trihydroxy chalcone 125 was synthesized by condensation of resacetophenone

123 with 4-hydroxybenzaldehyde 124 in the presence of an excess of KOH.115

However, attempts to cyclize the chalcone 125 using a literature procedure116 (1.5% aqueous sodium acetate solution) gave very low yield of the flavanone 126 (Scheme

24). O O O

H KOH, EtOH 100°C, 65% HO OH OH HO OH 125 123 124 OH

O 1.5% AcONa 7 days

HO O

126 OH

Scheme 24

34 O O

HO OH HO O 126 125 OH OH

Scheme 25

It has been reported in the literature that chalcone 125 and flavanone 126 exist in an

117 equilibrium (Scheme 25) and have the same Rf value on TLC, thus making their separation very difficult by column chromatography. The cyclization reaction was attempte d under various conditions and the results are summarized in Table 3.

No. Reaction condition Time Conversion (1H NMR)

1 1.5% AcONa, H2O, r.t. 72 h Trace

2 AcONa, H2O, reflux 40 h 40-45%

3 5% DBU, acetonitrile, r.t. 48 h 20-25%

4 5% DBU, H2O, r.t. 48 h 20%

5 DABCO, acetonitrile, reflux 48 h No reaction

6 DABCO, H2O, reflux 48 h No reaction

7 Triton-B, DCM, H2O, reflux 48 h No reaction

8 Piperidine, H2O, reflux 48 h 5-10%

9 TFA, reflux 24 h 25-30%

10 AcONa, AcOH, reflux 24 h 50-55%

11 AcOH, reflux 24 h 55-60%

12 H2SO4, EtOH, reflux 24 h 45-50%

13 conc. HCl, MeOH, reflux 24 h 75%

Table 3

In general, low conversion was observed under various alkaline conditions (Entries 1-8) while better conversion was obtained when the reaction was attempted under acidic

35 conditions (Entries 9-13). Finally, maximum conversion was observed when chalcone

125 was refluxed with conc. HCl in methanol for 24 h and flavanone 126 was obtained in 62% isolated yield. Acetylation of flavanone 126 with excess acetic anhydride in the presence of pyridine gave the diacetoxyflavanone 127 in 76% yield (Scheme 26).

OO O

conc. HCl, MeOH Ac2O, pyridine reflux, 62% 100°C, 76% HO OH HO O AcO O

125 OH 126 OH 127 OAc

Scheme 26

Catalytic reduction of flavanone 127 in ethanol was found to be very sluggish and less than 5% of the reduced product was observed after 72 h. It was soon realized that this was due to the poor solubility of the substrate in ethanol. However, when tetrahydrofuran (THF) was used as the solvent, reduction was complete in 48 h and the flavanol 128 could be isolated in 90% yield (Scheme 27).

H2, Pd/C, EtOH r.t., 5% O OH

AcO O AcO O

127 OAc 128 OAc H2, Pd/C, THF r.t., 90%

Scheme 27

The stereochemistry of flavanol 128 was established on the basis of an NOE between

H2 and H4 (Figure 9).

AcO NOE H H O 2 4 cis HO H H OAc 128 Figure 9

36 Flavanol 128 was condensed with various activated phenolic and heterocyclic compounds in the presence of BF3·OEt2 as mentioned in section 2.2.1.2. However, in this case the reactions were not stereoselective and gave mixtures of cis and trans isomers. The lack of stereoselectivity can be explained by the fact that the C2 phenyl group is away from the cationic carbon. As a result, the incoming nucleophile can attack from either face of the carbocation giving rise to a mixture of cis and trans isomers (Figure 10). The cis/trans isomers have the same Rf value on TLC and are very difficult to separate using flash column chromatography.

AcO H O H OAc trans H nucleophile H AcO H R 130 O 2 H OAc E H H AcO NO 129 H H O cis H nucleophile H OAc R 131

Figure 10

The mixtures were rechromatographed on a long silica column (~35 cm) and a number of fractions of smaller volume were collected. The initial fractions usually contained the trans isomer whereas the later fractions contained the cis isomer. In most cases the trans isomer was obtained in purer form than the cis isomer, and the latter isomer was always contaminated with 10-20% of the trans isomer.

2.2.2.2. Synthesis of 4-arylflavans

Reaction of flavanol 128 with 2’-hydroxy-6’-methoxyacetophenone 77 and 2’-hydroxy-

4’-methoxyacetophenone 80 gave a 50:50 mixture of cis/trans isomers in 67% and 37%

37 yields respectively. The isomers were separated by flash column chromatography and the acetoxy protecting groups were removed by hydrolysis (Scheme 28).

OMe O OMe O

5'' 6'' OH OH 5 4 H 77, BF ·OEt NOE 3 2 6 3 DCM, 67% H R O 2 5' R O

trans 2' R cis R 132 R = AcO 134 R = AcO KOH, MeOH KOH, MeOH 128 97% 133 R = OH 85% 135 R = OH

O OH O OH

5''

2'' OMe OMe 4 H NOE 80, BF3·OEt2 6 DCM, 37% H R O 5' R O

2' trans R cis R 136 R = AcO 138 R = AcO KOH, MeOH KOH, MeOH 87% 137 R = OH 100% 139 R = OH

Scheme 28

The 1H NMR spectrum of compound 132 showed two multiplets at 2.22 and 2.33 corresponding to two H3 protons. The H4 proton appeared as triplet at 4.57 (J = 4.1

Hz) whereas a doublet of doublet at 4.88 (J = 4.9, 8.7 Hz) corresponded to H2 proton.

In 1H NMR spectrum of compound 134 the two H3 protons appeared as multiplets at

2.22 and 2.41 and the H4 and H2 protons appeared as multiplets at 4.68 and 5.23.

Hence, the assignment of the stereochemistry was mainly based on an observed NOE between H2 and H4 protons in compound 134.

The 1H NMR spectrum of compound 136 showed two multiplets at 2.20 and 2.25 corresponding to two H3 protons and two doublets of doublets at 4.46 (J = 2.6, 5.3

Hz) and 4.89 (J = 3.0, 10.6 Hz) corresponding to H4 and H2 protons respectively. Two

38 singlets at 6.46 and 7.00 corresponded to H5’’ and H2’’ protons respectively. In the

1H NMR spectrum of compound 138 the H3 protons appeared as multiplet at 2.28, H4 proton appeared as multiplet at 4.69 whereas H2 proton appeared as doublet at

5.23 (J = 12.4 Hz). Again the assignment of the stereochemistry was mainly based on an NOE observed between H2 and H4 protons in compound 138.

Reactions of flavanol 128 with resorcinol 72, 3,5-dimethoxyphenol 85 and 3,4,5- trimethoxyphenol 88 gave complex mixtures which could not be separated by column chromatography (Scheme 29).

resorcinol 72

DCM, BF3·OEt2

85, BF ·OEt Complex 128 3 2 DCM, r.t. mixture

88, BF3·OEt2 DCM, r.t.

Scheme 29

This could be due to the presence of a number of reactive sites in the substrates. As a result, a mixture of regioisomers and stereoisomers having very close Rf values on TLC was obtained. Since the intermediate carbocation 129 in this case is less hindered compared to the carbocation formed from isoflavanol 140, it can react at hindered positions of the substrate such as in between the two hydroxy or two methoxy groups.

Less hindered More hindered

OAc

AcO O AcO O

129 OAc 140 Carbocation from Carbocation from flavanol 128 isoflavanol 76

39 2.2.2.3. Synthesis of 4-heteroarylflavans

With these results in hand, the reactions of flavanol 128 with some activated heterocyclic compounds were investigated.

Reaction of flavanol 128 with benzofuran 103 gave 50:50 mixtures of cis/trans isomers.

However, in this case only the trans isomer 141 could be isolated in pure form. The cis isomer was contaminated with substantial amounts of trans isomer and therefore was not completely characterized.

OMe MeO Br

O 103, BF3·OEt2 Chrom. 128 cis + trans DCM, 24% mixture R O

trans R 141 R = AcO KOH, MeOH 83% 142 R = OH

Scheme 30

The acetoxy protecting groups were removed under standard conditions using aq. KOH solution to give compound 142 (Scheme 30).

Similarly, reactions of flavanol 128 with isoflavene 112 and diphenylindole 106 gave mixtures of cis/trans isomers from which only the trans isomer could be isolated in pure form. The cis isomer was always contaminated with trans isomer and hence could not be completely characterized (Scheme 31).

40 O 2'' 5''' 8'' OMe

MeO 2''' 5'' 112, BF3·OEt2 Chrom. 4 cis + trans 6 DCM, 69% mixture 2 5' R 8 O 2' trans R 143 R = AcO KOH, MeOH 128 92% 144 R = OH

OMe 5''

MeO 2'' 106, BF3·OEt2 Chrom. N cis + trans 4 DCM, 73% mixture 6 H 2 5' R 8 O trans 2' R

145 R = AcO KOH, MeOH 95% 146 R = OH

Scheme 31

The 1H NMR spectrum of compound 143 showed two multiplets at 2.22 and 2.33 corresponding to two H3 protons. The H4 proton appeared as a multiplet at 4.49 whereas a doublet of doublet at 4.95 (J = 3.6, 10.6 Hz) corresponded to H2 proton.

Two singlets as 6.45 and 6.47 corresponded to H5’’ and H8’’ protons indicating that the C4 carbon was attached to C6’’ of the isoflavene subunit. In the 1H NMR spectrum of compound 145 multiplets at 2.44 (2H) and 4.78 (1H) corresponded to H3 and H4 protons respectively whereas the H2 proton appeared as doublet of doublet at 5.19 (J

= 5.3, 6.4 Hz). The H5’’ proton appeared as singlet at 6.34.

2.3. Conclusion

BF3·OEt2 catalyzed reactions of 4’,7-diacetoxyisoflavan-4-ol 76 with activated aryl and heteroaryl compounds gave trans 4-arylisoflavans and 4-heteroarylisoflavans in good

41 yield in a single step. However, the reaction of 4’,7-diacetoxyflavan-4-ol 128 under similar conditions gave a mixture of cis/trans isomers.

42 CHAPTER 3

ACID CATALYZED DIMERIZATION

OF FLAVENES

43 3.1. Introduction

Phenoxodiol 111, an isoflavone based drug candidate, shows cardioprotective as well as potential immunoprotective abilities.118 It has also been shown by numerous studies that it exerts inhibitory effects on several types of cancer cells, specifically hormone- dependent cancers such as prostate, ovarian and breast cancer and appears to be five to twenty times more potent than genistein 14.119,120

HO O 111

It has the ability to significantly reduce the mean tumor incidence and multiplicity, and significantly increase the median latency period in breast cancer cells, which is comparable to established agents such as Tamoxifen 9.121 It is thought that the mechanism of action of this compound is through inhibition of DNA topoisomerase II.

This prevents cell proliferation resulting in apoptosis (cell death) of cancer cells only.119

HO O HO O

111 147 OH Scheme 32

Phenoxodiol 111 is an isoflavene derivative. A structurally related molecule which has a similar substitution pattern is 4’,7-dihydroxyflav-2-ene 147 (Scheme 32). Will this compound have similar or better pharmacological properties than phenoxodiol 111?

Therefore, the synthesis of flavene 147 and related compounds was targeted in this project.

44 3.2. Retrosynthesis of 4’,7-dihydoxyflav-3-ene (147)

Retrosynthetic analysis indicates that flavene 147 can be synthesized by hydrolysis of

4’,7-diacetoxyflav-3-ene 148, which in turn can be obtained from the dehydration of

4’,7-diacetoxyflavan-4-ol 128. The synthesis of 128 has already been described in section 2.2.2.1. (Scheme 33).

HO O AcO O AcO O

147 OH 148 OAc 128 OAc

Scheme 33

3.3. Results and discussion

Dehydration of flavanol 128 with phosphorus pentoxide in dichloromethane gave flavene 148 in 35% yield. However, when the dehydration was carried out in refluxing toluene in the presence of a catalytic amount of p-toluenesulfonic acid, flavene 148 was obtained in 70% yield (Scheme 34).

P2O5, DCM OH 35%

AcO O AcO O

128 OAc p-TSA, toluene 148 OAc reflux, 70%

Scheme 34

The 1H NMR spectrum of flavene 148 showed a doublet of doublets at 5.91 (J = 1.1,

3.4 Hz, 1H) corresponding to H2 and two doublets of doublets at 5.75 (J = 3.4, 9.8

Hz, 1H) and 6.51 (J = 1.1, 9.8 Hz, 1H) corresponding to H3 and H4 respectively.

However, attempts to deprotect the acetoxy groups in flavene 148 under various mild alkaline conditions such as 1M KOH or 1M NaOH in methanol or even 10% ammonia in methanol instantaneously resulted in the formation of a brown polymeric material which

45 did not move on a TLC plate and showed no identifiable signals in the 1H NMR spectrum (Scheme 35).

1M KOH, MeOH r.t.

NH3(aq), MeOH r.t. AcO O HO O

148 OAc 1M NaOH, MeOH 147 OH r.t.

Scheme 35

In an attempt to avoid this extensive decomposition of the product, the diacetoxyflavene

148 was reacted under acidic conditions.

Surprizingly, while hydrolysis of the acetoxy groups with methanolic hydrochloric acid was successful, the product was not the expected flavene 147.

Figure 11. 1H NMR spectrum of compound 149

The 1H NMR spectrum (Figure 11) of the isolated compound was not consistent with the structure of flavene 147. High resolution mass spectrometric analysis of the product showed its molecular weight to be 530.1478 (M + Na)+ corresponding to molecular formula of C24H30O6 and indicated the formation of a dimeric compound.

46 The compound was subjected to extensive 1D and 2D NMR experiments using the 600

MHz NMR spectrometer.

A doublet of doublet of doublets at 2.51 (J = 2.1, 2.4, 10.9 Hz, 1H), doublet of doublets at 3.11 (J = 2.1, 6.7 Hz, 1H), doublets at 4.89 (J = 10.9 Hz, 1H) and 5.08 (J =

2.4 Hz, 1H) indicated the presence of four tertiary aliphatic protons, two of which should be attached to oxygenated carbon atoms. A doublet at 6.02 (J = 15.7 Hz, 1H) and a doublet of doublets at 6.24 (J = 6.7, 15.7 Hz, 1H) indicated the presence of a trans double bond in the molecule. Three doublets at 6.33 (J = 2.3 Hz, 2H), 6.77 and 7.25 each (J = 8.3 Hz, 1H) along with two doublets of doublets at 6.41 (J = 2.4, 8.3 Hz,

1H), 6.48 (J = 2.3, 8.3 Hz, 1H) indicated the presence of two 1,3,4-trisubstituted benzene rings. Two doublets at 6.74 and 7.19 each (J = 8.6 Hz, 2H), 6.89 and 7.2 each

(J = 8.5 Hz, 2H) indicated the presence of two 1,4–disubstituted benzene rings. Finally, two exchangeable broad peaks at 8.3 and 8.5 each (2H) indicated the presence of four hydroxyl groups in the molecule (Figure 11).

DEPT-135 along with the a broadband decoupled 13C NMR spectra indicated the

3 absence of any CH2 groups in the molecule, and the presence of four protonated sp carbons, 16 protonated sp2 carbons, and 10 non-protonated sp2 carbons.

This together with COSY, NOESY, HMQC and HMBC correlations indicated the structure 149 for the isolated compound.

47 2 1 OH 11 H HO O 4 12a H6a H 9 O 78 H 6 ß 2' 3' 2''

3'' OH

OH H 149 H H OH H OH H H HO O HO O H H H O H H H O H H H H H H H H H H H H H OH OH

OH OH Important NOEs for 149 Important HMBCs for 149

However, attempts to crystallize dimer 149 from various solvents to obtain a single crystal suitable for X-ray diffraction studies were not successful.

The corresponding tetraacetoxy derivative 150 was also synthesized by heating compound 149 in acetic anhydride and pyridine (Scheme 36). However, a single crystal of this derivative could not be obtained either.

OH OAc H H HO O AcO O H H H H O O H Ac2O, pyridine H 100°C, 74%

OH OAc

OH OAc 149 150 Scheme 36

48 3.4. Mechanism of the acid catalyzed rearrangement

A possible mechanism for this rearrangement is outlined in Scheme 37. Initially the flavene 148 presumably undergoes an acid catalyzed hydrolysis to give the dihydroxy flavene 147. Under acidic conditions, this could undergo protonation followed by ring opening of the flavene to give a benzylic carbocation 152. Probably the driving force behind this rearrangement is the relatively high stability of this benzylic carbocation.

This then could undergo rotation about the carbon-carbon single bond followed by attack of another dihydroxyflavene molecule 147. The attack would occur in such a way as to generate a second highly stable benzylic carbocation 153 which upon cyclization gives the dimer 149 (Scheme 37).

H H

AcO O HO O HO O H 148 OAc 147 OH 151 OH OH

rearrangement

rotation

HO OH

HO OH 152 OH 152

OH OH OH

O O O

HO OH HO OH HO O

OH OH OH 149 152 147 153 Scheme 37

This result was very interesting as it gives a very simple method for the synthesis of the highly functionalized benzopyranobenzopyran ring system in a single step. A survey of

49 the literature revealed that only one natural product, dependensin 34, having the same ring system has been reported previously.96 In the following chapter, the synthesis of dependensin 34 using this methodology will be discussed.

In order to investigate the scope of this acid catalyzed dimerization reaction, synthesis of other flav-3-enes where the hydroxyl group in ring-A was present at different positions was undertaken.

3.5. Synthesis of 4’,6-dihydroxyflav-3-ene (154) and its attempted dimerization

If ring-B in phenoxodiol 111 is moved from C3 to C2 and the hydroxyl group is moved from C7 to C6 carbon, it would result in 4’,6-dihydroxyflav-3-ene 154 (Scheme 38).

HO O O

111 154 OH Scheme 38

It would be of interest to establish whether such a compound would be stable under acidic conditions or would it also undergo dimerization. A literature survey revealed that compound 154 is not known.

3.5.1. Retrosynthesis of 4’,6-dihydroxyflav-3-ene (154)

OH O HO AcO HO

O O OH 154 OH 160 OAc 155

Scheme 39

In a sequence similar to that shown in the section 3.2., synthesis of 4’,6-dihydroxyflav-

3-ene 154 could possibly be achieved in two steps from flavanol 160, which in turn

50 could be derived from 2’,5’-dihydroxyacetophenone 155 in four steps as outlined in

Scheme 39.

3.5.2. Results and discussion

The literature procedure for the synthesis of chalcone 156 involves condensation of

2’,5’-dihydroxyacetophenone 155 and 4-hydroxybenzaldehyde 124 in the presence of

40% aqueous KOH at r.t. for a period of seven days.122 In order to avoid long reaction time, a similar procedure as described for the preparation of chalcone 125 was followed for this reaction (Scheme 40).

O O HO 124 HO KOH, EtOH O O HO OH OH 100°C OH

OH OH HO 155 156 157 Scheme 40

However, in this case, in addition to the desired product 156, compound 157 was also isolated. Presumably it was formed by Michael addition of a second molecule of 2’,5’- dihydroxyacetophenone 155 to the chalcone 156 (Scheme 41).

O O O O HO OH HO OH

OH HO OH HO 157 156 OH

Scheme 41

The cyclization of chalcone 156 was achieved by refluxing it with methanolic HCl, to give flavanone 158 in 92% yield. Acetylation of flavanone 158 followed by catalytic reduction of the diacetoxyflavanone 159 using palladium on charcoal gave predominantly the cis- flavanol 160 in 99% yield (Scheme 42).

51 O O O HO HO AcO conc. HCl, MeOH Ac2O, pyridine reflux, 92% OH O 100 °C, 65% O 159 156 OH 158 OH OAc

H2, Pd/C OH THF, r.t. 99% AcO AcO p-TSA, toluene reflux, 95% O O 161 160 OAc OAc

Scheme 42

The stereochemistry of the flavanol 160 (cis:trans:95:5) was established on the basis of an NOE observed between H2 and H4 protons (Figure 12).

NOE H H AcO O 2 4 cis HO H H OAc 160 Figure 12

The dehydration of flavanol 160 was achieved by refluxing it in the presence of a catalytic amount of p-toluenesulfonic acid in toluene to give flavene 161 in 95% yield.

However, attempted dimerization of flavene 161 with methanolic HCl gave a complex mixture. When flavene 161 was treated with aqueous KOH solution followed by acidification, dihydroxy flavene 154 was isolated in 47% yield (Scheme 43).

conc. HCl Complex mixture MeOH AcO

O HO

161 OAc KOH, EtOH 47% O 154 OH Scheme 43

This result indicated that the stabilization of the intermediate carbocation by the hydroxyl group in ring-A of flavene is necessary for the dimerization reaction. The 7-OH

52 group in 4’,7-dihydroxyflavene 148 is in a para position to the double bond and therefore stabilizes the intermediate carbocation 152 (Scheme 44). On the other hand, the 6-OH group in 4’,6-dihydroxyflavene 154 is meta to the double bond and therefore does not stabilize the intermediate carbocation 162 and hence flavene 154 does not undergo rearrangement and dimerization (Scheme 44).

Rearrangement and dimerization HO O HO OH 152 148 OH OH Highly stable benzylic cation

HO HO

No rearrangement O OH 162 154 OH OH No stabilization of benzylic cation Scheme 44

Such a stabilized carbocation would also be possible if the hydroxyl group is present at the C5 position such as in flavene 163 (Scheme 45).

OH OH

Might undergo rearrangement and dimerization O OH 163 164 OH OH

Scheme 45

Therefore, synthesis of 4’,5-dihydroxyflav-3-ene 163 was undertaken.

53 3.6. Synthesis of 4’,5-dihydroxyflav-3-ene (163)

3.6.1. Retrosynthesis of 4’,5-dihydroxyflav-3-ene (163)

4’,5-Dihydroxyflav-3-ene 163 should be accessible from 2’,6’-dihydroxyacetophenone

165, according to the strategy developed for the synthesis of flav-2-ene 148 via flavanol

172 as described in sections 3.2. and 3.3. (Scheme 46).

OH OAc OH OH O

O O OH 165 163 OH 172 OAc

Scheme 46

3.6.2. Results and discussion

Attempts to synthesize chalcone 166 by condensation of 4-hydroxybenzaldehyde 124 and 2’,6’-dihydroxyacetophenone 165 in the presence of excess KOH at 100 C were unsuccessful and led to the formation of a polymeric material. The literature method for the synthesis of chalcone 166 by condensation of 4-hydroxybenzaldehyde 124 and acetophenone 165 in the presence of NaOH123 or KOH124 gave very poor conversion

(Scheme 47). This observation has been confirmed by Takahashi et al.125 who reported similar problems with this method.

NaOH CHO OH O OH O EtOH

OH OH KOH OH EtOH OH 165 124 166 Poor conversion Scheme 47

A one step synthesis of flavanone 167 has been reported in the literature91 and involves heating 4-hydroxybenzaldehyde 124 and acetophenone 165 in the presence of boric acid and piperidine in various solvents. However, in our hands this method gave only very poor conversion to flavanone 167 (Scheme 48).

54 OH O CHO OH O

H3BO3, piperidine DMF OH O OH OH 165 124 167 Poor conversion Scheme 48

The discrepancy in the literature on the synthesis of 2’,6’-dihydroxychalcones has been discussed by Miles et al.126 who addressed this problem by protecting one of the hydroxyl groups of acetophenone 165 as the THP ether and then condensed the monoprotected acetophenone derivative with various aldehydes. Thus, acetophenone

165 was reacted with 3,4-dihydro-2H-pyran (DHP) in the presence of p-toluenesulfonic acid to give 2’-hydroxy-6’-tetrahydropyran-2-yloxyacetophenone 168 in 55% yield. The hydroxyl group of 4-hydroxybenzaldehyde 124 was also protected as the THP ether

169. Condensation of the THP protected acetophenone 168 and aldehyde 169 under standard conditions in the presence of excess KOH followed by deprotection gave

2’,4,6’-trihydroxychalcone 166 in 56% overall yield (Scheme 49).

OH O OH O

DHP, p-TSA THF, 55% THPO O OH OTHP 165 168 KOHaq EtOH CHO CHO OH DHP, p-TSA 170 OTHP THF, 80% Not isolated OH OTHP 2N HCl 124 169 MeOH 56%

OH O

OH 166 OH Scheme 49

Attempts to cyclize chalcone 166 under acidic conditions (similar to the ones used for the cyclization of chalcones 125 and 156) were unsuccessful and the starting material

55 was recovered unchanged. The literature method124 of using aq. NaOH and hydrogen peroxide for this cyclization also gave very poor conversion (Scheme 50).

HCl, MeOH OH O OH O reflux

OH O NaOH, H2O2 166 OH 167 OH Poor conversion Scheme 50

Surprisingly, this cyclization was achieved in high yield when sodium acetate was used as the base, and flavanone 167 was obtained in 92% isolated yield (Scheme 51).

OH O HO O OAc O

AcONa, EtOH Ac2O, pyridine reflux, 92% 100°C, 94% OH O O

166 OH 167 OH 171 OAc

Scheme 51

The high yield and ease of formation of 167 under these mildly alkaline conditions is probably due to the presence of 6’–OH group which stabilizes the intermediate anion by hydrogen bonding (Scheme 52).

H O O OH O 6'

2' O O H 166 OH 167 OH

AcO

Scheme 52

The two hydroxyl groups in the flavanone 167 were then protected by acetylation using acetic anhydride and pyridine under standard conditions giving diacetoxyflavanone 171 in 94% yield (Scheme 51).

56 Attempts to reduce the flavanone 171 by catalytic hydrogenation using Pd/C as a catalyst at ambient temperature and at 60 C were unsuccessful and the starting material was recovered unchanged. Reduction by transfer hydrogenation using Pd/C and ammonium formate gave a complex mixture, whereas catalytic hydrogenation using Raney nickel gave only the starting material (Scheme 53).

H2, Pd/C, MeOH No reaction 0o to 60oC OAc O

H , Ni 2 No reaction O MeOH, r.t. 171 OAc

HCOONH4 Complex mixture Pd/C, MeOH

Scheme 53

The difficulty in the reduction of the carbonyl group might by due to the presence of the bulky neighbouring acetoxy group at C5 which prevents the attachment of the carbonyl group to the catalyst surface.

Finally, the reduction was successfully carried out using sodium borohydride127 to give the desired trans-flavanol 172 in 95% yield. The dehydration of isoflavanol 172 was carried out under standard conditions, by refluxing it in toluene in the presence of a catalytic amount of p-toluenesulfonic acid to give 4’-acetoxy-5-hydroxyflav-3-ene 173 in

15% yield (Scheme 54).

OAc O OAc OH OH

NaBH4 p-TSA, toluene THF, MeOH reflux, 15% O 95% O O 171 OAc 172 OAc 173 OAc

Scheme 54

57 The dehydration in this case was also accompanied by deprotection of one of the acetoxy groups. This results in poor yields of the flavene 173 and formation of a substantial amount of polymeric material. The deprotection of the O-acetyl group at the

C5 can be explained on the basis of neighbouring group participation (Scheme 55).127

AcO OH O OH2 O O O O H2O

O O O O

172 OAc 174 OAc 175 OAc 176 OAc

O OH2

OH OH O O O H + H +H -H+ O O O

173 OAc 178 OAc 177 OAc

Scheme 55

However, when flavene 173 was treated with methanolic hydrochloric acid, only a brown polymeric material was obtained and a dimeric product could not be isolated from this reaction. The dimerization reaction was also attempted using trifluoroacetic acid/MeOH and p-toluenesulfonic acid/MeOH. However, reaction with trifluoroacetic acid/MeOH gave a polymeric material whereas reaction under p-TSA/MeOH conditions gave back the starting material (Scheme 56).

HCl, MeOH Polymeric material r.t. OH

TFA, MeOH Polymeric material O r.t.

173 OAc p-TSA, MeOH r.t. No reaction Scheme 56

58 3.7. Conclusion

4’,7-Dihydroxyflav-3-ene 148 undergoes stereoselective rearrangement and dimerization upon treatment with methanolic hydrochloric acid to give benzopyranobenzopyran ring system. However, the corresponding 4’,5- or 4’,6- dihydroxy substituted flavenes do not rearrange and dimerize under similar reaction conditions even though the 4’,5-dihydroxyflavene was expected to undergo the dimerization reaction.

59 CHAPTER 4

SYNTHESIS OF SOME FLAVONOID

NATURAL PRODUCTS

60 4.1. Synthesis of dependensin (34)

4.1.1. Introduction

Dependensin 34 is a dimeric flavonoid isolated from root bark of a Tanzanian medicinal plant of the species Uvaria dependens96 along with trimethoxyflavene 179, chalcone

180 and some other compounds (Figure 13). Although the biological activity of pure dependensin 34 has not been investigated due to unavailability of sufficient quantities of the natural material, the crude Uvaria extract containing dependensin 34 shows potent anti-malarial activity.96

MeO OMe OMe H MeO O OMe HH O

OMe H

34 OMe OMe O

MeO O MeO OH OMe OMe 180 179 Figure 13

It was further hypothesized96 that dependensin 34 might have originated by acid catalyzed dimerization of trimethoxyflavene 179, and therefore might be an artefact.

However, it was further reported that treatment of flavene 179 with HCl gas in chloroform followed by aeration gave chalcone 180 as the sole product and no traces of dependensin 34 were detected (Scheme 57).96

OMe OMe O

HCl(g), air CHCl , r.t. MeO O 3 MeO OH OMe OMe 180 179 Scheme 57

61 Based on the acid catalyzed dimerization of diacetoxyflavene 149 described in the previous chapter, it was thought that dependensin 34 could probably be formed in nature by the dimerization of trimethoxyflavene 179 (Scheme 58).

MeO OMe OMe H OMe MeO O OMe HH H+ O MeO O OMe H OMe 179

34 Scheme 58

In order to test this hypothesis, the synthesis of dependensin 34 was undertaken.

4.1.2. Retrosynthesis of dependensin (34)

As mentioned earlier dependensin 34 could be derived by the acid catalyzed dimerization of 5,7,8-trimethoxyflav-3-ene 179. Although the synthesis of flavene 179 has not been reported in the literature, based on the earlier studies described in section

3.3. it was envisaged that it could be obtained from trimethoxyflavanone 184 (Scheme

59).

OMe OMe O OMe

34 MeO O MeO O MeO OMe OMe OMe OMe 179 184 181 Scheme 59

A review of the literature indicated that flavanone 184 can be synthesised from tetramethoxybenzene 181 in three steps (Scheme 59).128

62 4.1.3. Results and discussion

Reaction of 3,4,5-trimethoxyphenol 88 with methyl iodide and K2CO3 in acetone gave

1,3,4,5-tetramethoxybenzene 181 in 96% yield. Due to the highly volatile nature of methyl iodide (b.p. 41 C), it was necessary to add excess of the reagent after every 6 h in order to drive the reaction to completion. The tetramethoxybenzene 181 so obtained was acetylated following the literature procedure129 involving aluminium chloride and acetyl chloride to give acetophenone 182 in 56% yield. One of the methoxy groups ortho to the acetyl group undergoes demethylation under the reaction conditions to give the target compound 182 (Scheme 60).

OH OMe OMe O

MeI, K2CO3 CH3COCl, AlCl3 acetone, reflux ether, 0°C to r.t. MeO OMe 96% MeO OMe 56% MeO OH OMe OMe OMe 88 181 182 Scheme 60

The acetophenone 182 was then converted to chalcone 183 in 95% yield by reaction with benzaldehyde and KOH in aqueous ethanol. The cyclization of the chalcone 183 to flavanone 184 was achieved in 63% yield by refluxing it with methanolic hydrochloric acid (Scheme 61).

OMe O OMe O OMe O

PhCHO, KOH conc. HCl, MeOH ethanol, r.t. reflux, 63% MeO OH MeO OH MeO O 95% OMe OMe OMe 182 183 184 Scheme 61

Attempts to reduce the flavanone 184 by hydrogenation using hydrogen gas and Pd/C as a catalyst were unsuccessful. The reaction was sluggish (ca 5-7 days) and the resulting product was a complex mixture. However, reduction using sodium borohydride in THF and methanol mixture (1:1) gave flavanol 185 as a sticky solid in 95% yield

(Scheme 62).

63 OMe O OMe OH OMe

NaBH4, THF, MeOH p-TSA, toluene 10°C, 95% reflux, 80% MeO O MeO O MeO O OMe OMe OMe 184 185 179

Scheme 62

The stereochemistry of flavanol 185 was found to be cis on the basis of an observed

NOE between H2 and H4 (Figure 14).

MeO MeO NOE H H O cis MeO HO H H 185 Figure 14

The flavanol 185 was found to be unstable, therefore it was quickly converted into the related flavene 179 by dehydration with p-toluenesulfonic acid in refluxing toluene

(Scheme 62).

The flavene 179 underwent dimerization on treatment with methanolic hydrochloric acid to give dependensin 34 in 72% yield (Scheme 63).

MeO OMe OMe H OMe MeO O OMe H H conc. HCl, MeOH O H MeO O overnight, r.t. OMe OMe 72% 179

Scheme 63

The structure and stereochemistry of 34 were established on the basis of spectroscopic data. The observed UV, IR and NMR signals matched exactly with the reported values.96

64 A selection of important NOEs and long range 1H-13C correlations are shown in Figure

15.

H H MeO OMe MeO 1 OMe OMe OMe H H MeO O MeO O 4 OMe OMe HH H 6aH H O 9 O H 7 6 MeO H MeO H H H H H H 2' 3' 2'' 3'' Important long range Important NOEs for 34 correlations for 34

Figure 15

The cis-fusion of the benzopyran rings was indicated by the observed coupling constant

(J = 2.6 Hz) between H6a and H12a and from the presence of NOE between these protons. NOEs and 1H couplings also established the relative configurations of H-6 and

H-7 protons. However, the melting point of the synthetic dependensin was found to be

197-199 °C (from MeOH) compared with the reported96 melting point of 125-126 °C

(from MeOH). This difference in the melting point could be due to a typographical error in the literature, or to a different polymorphic form or possibly due to some impurity in the natural compound. The structure of the synthesized dependensin 34 was further confirmed by elemental analysis.

4.1.4. Conclusion

It was found that appropriately substituted flavenes undergo stereoselective rearrangement and dimerization when treated with methanolic hydrochloric acid to give benzopyranobenzopyrans. This synthetic methodology has been used for a high yield synthesis of the natural product dependensin 34.

65 4.2. Attempted synthesis of kamalachalcone-A (186)

4.2.1. Introduction

The granular hairs on the surface of fruits of Mallotus philippensis Muell are covered with an exudate of a reddish substance called kamala130 which has traditionally been used as a drug and a dye. Some of the flavonoids from Mallotus japonicus Muell have shown cytotoxic activity in the L-5178Y mouse lymphoma cell lines.131 Therefore, the constituents in the genus Mallotus have drawn attention for their possible biological activity.130

Kamalachalcone-A 186 was isolated from the acetone extracts of kamala along with kamalachalcone-B 187 and Rottlerin 188, and its structure was esta blished on the basis of 2D NMR spectroscopy (Figure 16).130

OO H O O H HO O H Me HO OH Me 186

Me OH O O H OH O O HO H HO O O OH H OH HO O O HO OH O Me HO OH 188 Me 187

Figure 16

It was further proposed that a plausible biogenesis of kamalachalcone-A 186 involves ring formation between identical chalcones 189, although the enzyme or catalyst for such dimerization and ring formation was not indicated (Scheme 64).130

66 O O O O H Ph O O Ph O O H HO O Ph HO OH Ph H Me Me HO OH HO OH Me Me 186 189 189

Scheme 64

Based on our experience with the synthesis of dependensin 34, it was proposed that kamalachalcone-A 186 could be formed by acid catalyzed dimerization of chalcone

189. The literature precedence for this proposal is the synthesis of dimeric dihydropyran natural product 191 by acid catalyzed dimerization of dihydropyran natural product 190 (Scheme 65).132

O O O H O O HO O H HCl, MeOH HO O H Me r.t. Me HO OH OH Me 190 191 Scheme 65

4.2.2. Retrosynthesis of kamalachalcone-A (186)

As discussed in the previous section, kamalachalcone-A 186 could be derived from acetophenone 192 via the chalcone 189 (Scheme 66).

O O

HO O HO OH 186 Me OH OH 189 192 Scheme 66

67 4.2.3. Results and discussion

Although acetophenone 192 is commercially available, its procurement takes a long time. With plenty of phloroglucinol 99 at hand, acetophenone 192 was synthesized by the Hoesch acetylation reaction (Scheme 67).133 The commercially available phloroglucinol dihydrate was dried by heating in a hot air oven at 120 C for 12 h. Due to unavailability of fused zinc chloride, which is normally used as a Lewis acid in

Hoesch acetylation, the reaction was attempted using anhydrous zinc chloride.

O O

HO OH HO OH HO OH MeCN, ZnCl2 Zn(CN)2 HClg, Et2O HClg, Et2O CHO OH 75% OH 20°C, 72% OH 99 192 193 Scheme 67

However, under these reaction conditions acetophenone 192 was obtained in only 37% yield, instead of the reported yield of 85%. This could be due to the use of anhydrous zinc chloride instead of fused zinc chloride. Therefore, in subsequent preparations the amount of anhydrous zinc chloride was doubled and the yield of reaction increased from 37% to 75%. Acetophenone 192 was formylated under Gattermann formylation conditions using the literature procedure134,135 except that the reaction was carried out at 20 C and compound 193 was obtained in 72% yield (Scheme 67).

Zinc cyanide required in the Gattermann formylation was prepared by reacting anhydrous zinc chloride with sodium cyanide in quantitative yield using a literature procedure136 (Scheme 68).

H2O ZnCl2 + 2 NaCN Zn(CN)2 + 2 NaCl EtOH

Scheme 68

68 The aldehydic group in acetophenone 193 was selectively reduced under Clemmensen reduction conditions134 using amalgamated zinc wool and conc. HCl in methanol at 50

C, yielding 3’-methylacetophenone 194 in 75% yield (Scheme 69).

O O 2 1 HO OH HO OH Zn(Hg), HCl CHO MeOH, 50°C 5' 3' Me 76% OH OH 193 194 Scheme 69

The synthesis of 194 has also been reported in the literature137 by C-methylation of acetophenone 192 with methyl iodide in the presence of sodium methoxide in anhydrous methanol (Scheme 70). In our hands this method gave a mixture consisting of starting material and the desired product which unfortunately could not be separated by column chromatography.

O O

HO OH HO OH MeI, MeONa anh. MeOH Me OH OH 193 194 Scheme 70

With the other method at hand this route was not pursued further.

The next step in the sequence is the alkylation of the 6’-OH group of acetophenone 194 with 3-chloro-3-methyl-1-butyne 196 which was synthesised from 2-methyl-3-butyn-2-ol

195 in 72% yield and excellent purity138 (as determined by its 1H NMR spectrum)

(Scheme 71). Hence, this product was used in the next step without further purification.

CuCl, CaCl2 H H conc. HCl, 0°C OH Cl 72% 195 196

Scheme 71

69 However, attempts to alkylate acetophenone 194 with 3-chloro-3-methyl-1-butyne 196 gave a very complex mixture and all attempts to separate this mixture by column chromatography were unsuccessful (Scheme 72).

O O

HO 2' 6' OH HO O 196, K2CO3, KI dioxane, reflux Me 4' Me OH OH 194 197

Scheme 72

It has been reported that in acetophenone 194 the hydroxyl group para to the carbonyl group is the most reactive and is the first to undergo an alkylation or acylation reaction.139,140,141 Therefore, protection of the 4’-OH group is essential prior to alkylation with 3-chloro-3-methyl-1-butyne 196. The selected protecting group should be such that it can be easily removed under mildly acidic or alkaline conditions and should not require drastic conditions or hydrogenation for deprotection.

The protection of the 4’-OH of acetophenone 194 as a tosylate ester has already been reported.139 The reaction involved refluxing the acetophenone 194 with p- toluenesulfonyl chloride in dry acetone in the presence of ignited K2CO3. It is further reported that the protected acetophenone 198 was isolated in 22% yield together with the ditosylated acetophenone 199 in 15% yield (Scheme 73).139

O O O

HO OH HO OH TsO OH TsCl, K2CO3 acetone, reflux Me Me Me OH OTs OTs 194 198 199

Scheme 73

However, in our hands the reaction under the same conditions gave the desired monotosylated acetophenone 198 in 11% yield and a mixture of the ditosylated

70 acetophenone 199 and tritosylated acetophenone 200 was obtained as the major products. O

TsO OTs

OTs 200

The tritosyloxy product 200 has the same Rf value as that of the monotosyloxy product

198 which made the chromatographic purification extremely difficult. When the reaction was repeated on a larger scale, it yielded a mixture of monotosyloxy 198 and tritosyloxy

200 compounds from which the pure monotosyloxy product 198 could not be isolated.

The reason for the lack of selectivity in the tosylation reaction is probably due to the electron withdrawing nature of the tosyl group. After monotosylation the remaining two hydroxyl groups become more acidic and hence react quickly with p-toluenesulfonyl chloride to give the ditosylated product 199. Presence of the two tosyloxy groups makes the remaining hydroxyl group even more acidic and a rapid reaction with tosyl chloride gives the tritosyloxy product 200.

As the protection of 4’-OH is important this tosylation reaction was studied extensively and the results of the various trials are summarized in Table 4.

71 No. Reaction conditions Result

1 TsCl, K2CO3, acetone, reflux

2 TsCl, K2CO3 (1 eq.), acetone, reflux

3 TsCl, K2CO3 (0.5 eq.), acetone, reflux TsCl (slow addition), K CO , 4 2 3 acetone (75 volume), reflux 5 TsCl, K CO , acetone, r.t. Mixture of 2 3 198, 199, 200 194 + K CO + acetone reflux 6 2 3 then slow addition of TsCl

7 TsCl, NaHCO3, acetonitrile, reflux

8 TsCl, KHCO3, acetonitrile, reflux

9 TsCl, pyridine, r.t.

Table 4

As the above mentioned attempts for selective monotosylation were unsuccessful, hydrolysis of the ditosylated compound 199 under alkaline conditions with one equivalent of KOH in methanol was also investigated.

O O

TsO OH HO OH KOH (1 eq.) MeOH, 50°C Me Me OTs OTs 199 198 Scheme 74

However, the reaction gave a complex mixture from which the desired monotosylated product 198 could not be isolated (Scheme 74).

In order to overcome this problem, the tosylation of 3’-formylacetophenone 193 was also attempted, in case it might give some selectivity, and the formyl group could then be selectively reduced later in the synthesis. However, a complex mixture was obtained in the attempted tosylation of the formylacetophenone 193 (Scheme 75).

72 O O O

HO OH HO OH HO OH TsCl, K2CO3 acetone, reflux CHO CHO Me OH OTs OTs 193 201 198 Scheme 75

To overcome these difficulties, the use of methoxymethyl (MOM) protecting group, which can be easily cleaved off under mildly acidic conditions was investigated.

The alkylation of acetophenone 194 was attempted under two different conditions. In the first instance, the acetophenone 194 was reacted with 1 equivalent of chloromethyl methyl ether (MOMCl) in dry acetone in the presence of anhydrous K2CO3. However, this reaction gave multiple products. When the reaction was carried out in dry dichloromethane in the presence of an organic base such as diisopropylethylamine

(DIPEA), again multiple products, with very close Rf values were obtained (Scheme

76).

O MOMCl, K2CO3 O acetone, r.t. HO OH HO OH

Me Me MOMCl, DIEA OH O O DCM, 0-5°C 194 202 Scheme 76

The reason for the lack of selectivity with the methoxymethyl protecting group is probably due to high reactivity of MOMCl. Therefore, use of bulky silyl protecting groups such as trimethylsilyl and tert-butyldimethylsilyl was investigated for the protection step.

Surprisingly, attempts to react acetophenone 194 with trimethylsilyl chloride (TMSCl) in the presence of triethylamine in dichloromethane gave none of the desired product. The

73 reasons for this unsuccessful result are not fully understood although the presence of moisture in triethylamine might have been one of the possibilities (Scheme 77).

O O

HO OH HO OH TMSCl, TEA DCM, 0°C to reflux Me Me OH OTMS 194 203 Scheme 77

Acetophenone 194 was then reacted with tert-butyldimethylsilyl chloride (TBDMSCl) in dry DMF in the presence of dry imidazole.142 Initially when 1.2 equivalents of TBDMSCl were used in the reaction, formation of a small amount of the desired compound 204 was observed by TLC and most of the starting material remained unreacted even after stirring for 15 h. Further addition of 0.8 equivalents of TBDMSCl in the reaction resulted in the formation of two products along with starting material. Upon work-up the desired monosilylated acetophenone 204 was isolated in 29% yield along with the disilylated product 205 in 36% yield (Scheme 78).

O O O

HO OH HO OH TBDMSO OH TBDMSCl, TEA DCM, 0°C to reflux Me Me Me OH OTBDMS OTBDMS 194 204 205 Scheme 78

Although the yield of the desired monosilylated product 204 was low, with all other options exhausted, this product was subjected to the alkylation reaction.

The monosilylated acetophenone 204 was treated with chlorobutyne 196 in acetone in the presence of KI and excess K2CO3, however, no reaction was observed. The use of diisopropylethylamine (DIPEA) as a base in refluxing dichloromethane also did not improve the reaction (Scheme 79).

74 196, K2CO3, KI acetone, reflux No reaction 196, DIPEA O DCM, reflux O

HO OH TBDMSO OH 196, DIPEA acetone, reflux Me Me OTBDMS OTBDMS 205 204 196, DIPEA DMF, r.t. O HO OH

196, TBAI, K2CO3 MEK, reflux Me OH 194

Scheme 79

When the reaction was carried out in DMF at r.t. with DIPEA as base surprisingly complete desilylation of acetophenone 204 was observed within 0.5 h and the parent acetophenone 194 was isolated as the sole product.

Reaction in refluxing acetone with DIPEA as base gave a new spot on the TLC plate.

Surprisingly, upon work-up, the product was found to be the disilylated product 205 probably resulting from the disproportionation of the starting material under alkylation conditions.

These results indicated that chlorobutyne 196 is not reactive enough under these mild conditions. In order to address this issue, the reaction was carried out in refluxing methyl ethyl ketone (MEK) in the presence of tetrabutylammonium iodide and excess

K2CO3. However, desilylation of acetophenone 204 was observed under these conditions and only acetophenone 194 was isolated from this reaction.

With these disappointing results, the dimerization strategy was investigated using acetophenone 192. It was envisaged that the dihydroxychromene 206 upon treatment

75 with acid would undergo dimerization to give the dimer 207, which could then be converted into kamalachalcone-A 186 (Scheme 80).

O O O H HO O O O H 186 HO O H OH HO OH 206 207 Scheme 80

The dihydroxychromene 206 can be synthesised from acetophenone 192 in three steps.

Acetophenone 192 was tosylated using two equivalents of p-toluenesulfonyl chloride in refluxing acetone to give ditosyloxyacetophenone 208 and tritosyloxyacetophenone 209 in 55% and 8% yields respectively. The ditosylate 208 was then heated with 3-chloro-3- methyl-1-butyne 196 in acetone to give alkyne 210 which on thermal cyclization gave ditosyloxychromene 211. The tosyl groups were hydrolysed by refluxing the chromene

211 with methanolic KOH to give dihydoxychromene 206 (Scheme 81).

O O O HO OH TsO OH TsO O TsCl, K2CO3 196, K2CO3 acetone, reflux acetone, reflux OH 55% OTs 97% OTs O H 192 208 210 TsO OTs

O O DMA, DMF 140°C, 100% OTs HO O TsO O 209 KOH, MeOH reflux, 32%

OH OTs 206 211 Scheme 81

Surprisingly, dihydroxychromene 206 upon treatment with acids under various conditions failed to dimerize. Upon treatment with conc. HCl/MeOH or 10-

76 camphorsulfonic acid/MeOH, only the unchanged starting material was recovered, whereas treatment with TFA or 10-camphorsulfonic acid/benzene gave a complex mixture of prodcts (Scheme 82).

conc. HCl, MeOH r.t.

No reaction O CSA, MeOH HO O r.t.

CSA, benzene

OH r.t. 206 Complex mixture TFA

r.t., 10 min Scheme 82

It is possible that the C6-methyl group in chromene is important for the dimerization reaction to proceed. In an attempt to introduce the C6-methyl group, formylation of chromene 206 under Gattermann conditions was undertaken.

However, treatment of chromene 206 with zinc cyanide and hydrogen chloride only gave a polymeric meterial (Scheme 83).

O O O HO O HO O HO O Zn(CN)2, HCl(g) Ether OHC Me OH OH OH 206 212 213

O O H O O 186 H HO O H Me HO OH 214 Me Scheme 83

77 Due to these poor results, despite following different synthetic strategies, the synthesis of kamalachalcone-A 186 was discontinued.

4.2.4. Conclusion

Kamalachalcone-A 186 with its polycyclic structure and dense array of functionality and stereochemistry was found to be a very challenging synthetic target. Because of poor yields and frequent formation of complex mixtures/polymeric materials in the synthesis of various intermediates, the total synthesis of kamalachalcone-A 186 could not be completed during the course of this investigation.

78 4.3. Synthesis of flavonoid natural products

4.3.1. Introduction

Calanolide-A 215 and Inophyllum-B 216 are two dipyranocoumarins that have been identified as potent inhibitors of human immunodeficiency virus-1 reverse transcriptase

(HIV-1 RT) in in vitro screening assays.143

O O

O O O O O O

OH OH

215 216

Octandrenolone 217, flemiculosin 218, (–)-3-deoxy-MS-II 219 and laxichalcone 220 are examples of polycyclic flavonoid natural products which have similar polycyclic ring structures to calanolide-A 215 and inophyllum-B 216 (Figure 17).

6'' 5'' 6'' 5''

2'' 2'' 3'' O O 3'' O O 2 2' 4'' 1 4'' 1' 3 3' 2 4 6 4' 6' 1 3 O 5 OH O 5' OH 2''' 2''' 5''' 4''' 5''' 4''' 6 4 3''' 3''' 5 6''' 6''' 217 218

6'' 5'' 6'' 5''

2'' 2'' 3'' O O 3'' O O 2' 5 4 4'' 4'' 4a 3 1' 6 3' 2' 2 7 8a 2 4' 6' 3' 3 O 5' OH 1 O 8 O 1' 2''' 4 5''' 2''' 5''' 4''' 4''' 6' 4' 6 OH 3''' 5' 3''' 5 6''' 6''' 219 220 Figure 17

Octandrenolone 217 was first isolated from the leaves of Melicope octandra144 and later from Melicope erromangensis.145 The related chalcone structure flemiculosin 218 was

79 isolated from leaves of Flemengia fruticulosa146 and its structure was confirmed by X- ray crystallography.147 A closely related analogue laxichalcone 220 was isolated from the roots of Derris laxiflora and its structure was established on the basis of spectroscopic data.148,149 Kingston et al.150 isolated (–)-3-deoxy-MS-II 219 from the bark and leaf extracts of Mundulea chapelieri and reported its potent cytotoxicity against a human ovarian cancer cell line.

Although the synthesis of octandrenolone 217 is known, syntheses of flemiculosin 218,

(–)-3-deoxy-MS-II 219 and laxichalcone 220 have not been reported previously.

Therefore, the synthesis of these natural products was undertaken during the course of this project.

4.3.2. Results and discussion

Prior to its isolation as a natural product, octandrenolone 217 was synthesized by the reaction of acetophenone 192 with 3-hydroxy-3-methylbutanal dimethyl acetal 221 in

4% yield (Scheme 84).151

O O O

HO OH OMe pyridine OMe reflux, 4% OH O OH OH 221 192 217 Scheme 84

Chromenes such as 224 are generally synthesized by reaction of a phenolic compound

222 with 3-chloro-3-methylbut-1-yne 196 (Scheme 85)

OH O O K2CO3, KI R H R R acetone, reflux Cl R1 R1 R1 222 196 223 H 224

Scheme 85

80 The reaction involves the initial formation of a propargyl ether intermediate 223 followed by cyclization to give chromene 224. It has been reported that when this method was used for the synthesis of octandrenolone 217 from acetophenone 192, a complex mixture of six products was obtained containing the desired product together with some uncyclized intermediates (Scheme 86).152

O O O O O O H

O OH O O OH O OH

HO OH 196, K CO , KI 225 2 3 217 H 226 reflux

OH O O O O O O 192

O OH O OH O OH

227 228 229

Scheme 86

It was further reported152 that addition of a catalytic amount of CuI dramatically affects the course of the reaction and octandrenolone 217 was isolated in 78% yield (Scheme

87).

. O O O HO OH 196, K2CO3, KI, CuI acetone, reflux 78% O OH OH

192 217 Scheme 87

However, in our hands, the attempted synthesis of octandrenolone 217 from acetophenone 192 following this procedure led to a complex mixture of compounds from which only a very small amount of the desired product could be isolated.

81 Addition of CuI has been shown to catalyse only the propargyl ether formation.153

Moreover, the catalytic effect is observed only for phenols with electron withdrawing substituents in the aromatic ring. The following mechanism has been proposed to explain the catalytic effect of CuI (Scheme 88).

2 2 R 2 R -Cl -Cu 2 R Base R Cu Cl Cu H Cl 1 1 CuI 1 R R 1 R 232 230 R 231 233

-Cu ArOH ArOH

R2 H OAr 1 234 R Scheme 88

It has also been reported that heating of the propargyl intermediate 223 in a high boiling solvent like N,N-dimethylaniline (DMA), DMF, 1,2-dichlorobenzene or a mixture thereof is essential for the cyclization to chromene 224.

Assuming that uncyclized intermediates were present in the reaction mixture, the crude product was heated in a mixture of N,N-dimethylaniline (DMA) and DMF (1:12) at 140

ºC for 2 h. The TLC analysis of the reaction mixture showed formation of octandrenolone 217 as the major product along with two minor impurities.

Octandrenolone 217 could be quite easily isolated from this mixture by column chromatography in 40% yield (Scheme 89).

O O O 196 HO OH o K2CO3, KI, CuI complex DMF, DMA, 140 C mixture chromatography acetone, reflux O OH OH 40% 192 217 Scheme 89

82 Figure 18. 1H NMR of octandrenolone 217

1 The H NMR spectrum of octandrenolone 217 showed four geminal CH3 groups as two singlets at 1.43 and 1.49 (6H each). The CH3CO protons appeared as a singlet at

2.64 whereas the hydrogen bonded OH appeared as a singlet at 13.99. Two doublets at 5.43 (J = 10.3 Hz) corresponded to the H3’’, H3’’’ protons whereas the H4’’ and

H4’’’ protons appeared as two doublets at 6.58 and 6.64 (each J = 10.3 Hz) (Figure

18).

Octandrenolone 217 was condensed with benzaldehyde in the presence of excess

KOH in ethanol to give flemiculosin 218 in 90% yield (Scheme 90).

O O O O O O PhCHO, KOH AcONa, EtOH EtOH, r.t. OH reflux, 42% O 90% O OH O O

217 218 219 Scheme 90

Cyclization of flemiculosin 218 was achieved by refluxing it with sodium acetate in ethanol. However, the progress of the reaction slowed after 48 h due to the chalcone- flavanone equilibrium. Aqueous work-up gave (±)-3-deoxy-MS-II 219 in 42% yield

(Scheme 90).

83 Figure 19. 1H NMR of flemiculosin 218

1 The H NMR spectrum of flemiculosin 218 (Figure 19) showed four geminal CH3 groups as two singlets at 1.45 and 1.55 (each 6H). The H3’’, H3’’’ protons appeared as a doublet at 5.47 (J = 10.2 Hz), whereas the H4’’’ and H4’’ protons appeared as two doublets at 6.61 and 6.69 (each J = 10.2 Hz). The doublets at 7.76 and 8.09 (each

J = 15.5 Hz) corresponded to the trans double bond protons, whereas the hydrogen bonded OH appeared as a singlet at 14.36. The aromatic protons were present as multiplets at 7.40 and 7.61.

Figure 20. 1H NMR of (±)-3-deoxy-MS-II 219

84 1 The H NMR spectrum of (±) 3-deoxy-MS-II 219 showed four geminal CH3 groups as four singlets at 1.44, 1.45, 1.48 and 1.52 (Figure 20). The two H3 protons appeared at 2.77 (dd, J = 3.1, 16.6 Hz, 1H) and 2.96 (dd, J = 12.8, 16.6 Hz, 1H), whereas the

H2 proton appeared at 5.39 (dd, J = 3.0, 12.8 Hz, 1H). The H3’’’, H3’’, H4’’’ and H4’’ protons appeared at 5.46, 5.50, 6.57 and 6.60 each (d, J = 10.1 Hz, 1H). The aromatic protons were present as multiplets at 7.35-7.46.

Attempts to condense octandrenolone 217 with 4-hydroxybenzaldehyde 124 in the presence of KOH in ethanol were unsuccessful and only starting materials were recovered from the reaction. The reaction was repeated using various phase transfer catalysts such as tetrabutylammonium bromide (TBAB), tetrabutylammonium iodide

(TBAI) and tetraethylammonium acetate (TEAA). However, none of the above mentioned conditions were effective and only unreacted starting materials were recovered from these reactions (Scheme 91).

KOH, EtOH r.t.

KOH, TBAB O O O O CHO EtOH, r.t.

O OH O OH OH KOH, TBAI OH EtOH, r.t. 217 124 220 KOH, TBAA EtOH, r.t. Scheme 91

The presence of the hydroxyl group para to the aldehyde is mainly responsible for this reduced reactivity of 4-hydroxybenzaldehyde 124. The hydroxyl group can easily form a potassium salt, which in turn reduces the electrophilic character of the carbonyl group

(Scheme 92).

85 H O K CHO H O

KOH

OH K O O 124

Scheme 92

To overcome this problem, the hydroxyl group was protected as the methoxymethyl

(MOM) ether. Thus, 4-hydroxybenzaldehyde 124 was reacted with an excess of dimethoxymethane in the presence of phosphorus pentoxide to yield 4- methoxymethoxybenzaldehyde 235 in 66% yield (Scheme 93).

CHO CHO

CH2(OCH3)2, CHCl3

P2O5, r.t. OH 66% O O 124 235 Scheme 93

Octandrenolone 217 was reacted with 4-methoxymethoxybenzaldehyde 235 in the presence of sodium hydride as base in DMF at 0 C. The intermediate chalcone 236 was deprotected in situ to give laxichalcone 220 in 78% overall yield (Scheme 94).

O O O O O O

235, NaH HClaq, EtOH DMF, 0oC 60oC O OH O OH O OH O OMe OH 217 236 220 Not isolated Overall 78%

Scheme 94

86 Figure 21. 1H NMR of laxichalcone 220

The 1H NMR spectrum (Figure 21) of laxichalcone 220 was similar to that of flemiculosin 218 except that the aromatic protons appeared as two doublets at 6.84 and 7.52 each (J = 8.7 Hz, 2H) and there are two hydroxyl peaks at 10.16 (bs, 4-OH) and 14.42 (s, 6’-OH)

The NMR and other spectroscopic data of all synthesized compounds and the reported natural products were identical.

4.3.3. Conclusion

Short and efficient syntheses of polycyclic natural products octandrenolone 217, flemiculosin 218, (±) 3-deoxy-MS-II 219 and laxichalcone 220 have been developed.

87 CHAPTER 5

SYNTHESIS OF DIMERS BY

OXIDATIVE COUPLING

88 5.1. Introduction

Oxidative coupling of phenols is of great importance in natural products chemistry and has been widely postulated as a biosynthetic pathway to many aromatic heterocyclic products154 including alkaloids and antibiotics. The coupling step is often replicated in the laboratory by use of inorganic oxidants. However, the yields of the coupling step are, in general, low and the work-up procedure is complicated by the necessity of handling polyhydric phenols in the presence of strong base.

A number of reagents have been widely used for oxidative coupling reactions such as

155 156 FeCl3, FeCl3-DMF complex, FeCl3 bound to silica, copper(II) diamine

157 158 159 complexes, alkaline K3[Fe(CN)6], (NH4)2Ce(NO3)6-H2O2 and photochemical conditions.160

Recently, a number of new reagents have been reported and these appear to give consistently high yields of intramolecularly coupled products. Those which are

161 particularly useful are vanadium oxytrichloride (VOCl3), vanadium oxytrifluoride

162-165 166 (VOF3), manganese tris(acetylacetonate) (MTA), thallium(III) trifluoroacetate

(TTFA)167,168 and lead tetraacetate (LTA).169,170 These reagents have been used to couple a wide range of monophenolic, diphenolic and nonphenolic substrates. Metal salt induced oxidative dehydrodimerization of aromatic compounds is known as the

Scholl reaction.167,171,172 In addition, controlled electrochemical oxidation173,174 of nonphenolic and monophenolic substrates has also been developed as a method of choice for the synthesis of various complex natural products.

5.2. General types of coupling mechanisms175

Plausible mechanisms for the oxidative coupling can be grouped into two broad classes, each of which may be further divided into several general mechanistic types.

89 5.2.1. Mechanism involving free-radical intermediates (Scheme 95)

i) Direct coupling of two phenoxy radicals (FR1),

ii) homolytic aromatic substitution (FR2) and

iii) heterolytic coupling preceded by two successive one-electron oxidations

(FR3).

OH O O R R R R R R -e-, -H+

237 238 FR2 239 FR3 - 237 -e R R O H R R HO O Coupling of two FR1 phenoxy radicals H R H R -e- -H+ -H+ 244 242 237 R R Disproportionation H O O R H R H H R 240 R HO OH H R 243 R -2 H+ - -2 e R R

HO OH

R 241 R

Scheme 95

In the free-radical mechanism, initially an electron is transferred from phenol 237 to an oxidant resulting in the formation of a phenoxy radical with several resonance structures. This radical can then take one of three general paths, all leading to the same product. Firstly, two such radicals might couple homolytically, by mechanism

FR1, to give quinone 240 which tautomerizes to a stable bisphenol product 241.

Secondly, one of these radical species could react with another phenol molecule 237 to generate a dimeric radical 242 (FR2). This new radical could lose an electron and a proton to give quinone 240 or it might disproportionate, leading to a dihydro product

90 243 as well as quinone 240. Finally, a heterolytic coupling process might occur following the oxidation of a phenoxy radical to a phenoxy cation 244 (FR3), which could then lead to quinone 240 followed by tautomerism to bisphenol 241.

FR1 is the most commonly accepted mechanistic pathway, however, the possibility of

FR2 cannot be ruled out. FR3 is also another possible pathway, but it has been given little importance.

5.2.2. Mechanism with non-radical intermediates

i) Heterolytic coupling preceded by a single two electron transfer (NR1)

(Scheme 96) and

ii) concerted coupling and electron transfer (NR2) (Scheme 97).

OH +2 O M O R R R R R R -H+ -M+ M+3

237 245 244

+ -H 237

R R R R H HO OH O O H R R R R 241 240

Scheme 96

In the non-radical mechanism (NR1), a metal ion forms an initial metal-phenolate compound 245, which decomposes into a phenoxy cation with concurrent two-electron reduction of the metal ion followed by heterolytic coupling to give quinone 240 which tautomerizes to bisphenol 241 (Scheme 96). Another possibility is concerted electron transfer (NR2) as outlined in Scheme 97.

91 R R R R -H+ HO OH M+3 H O O M+2

R R R 237 R 245 237 237 -H+

R R R R H HO OH O O H R 241 R R 240 R Scheme 97

5.3. Results and discussion

5.3.1. Oxidative dimerization of daidzein 38

As discussed in section 1.1.7., kudzuisoflavones A 35, B 36 and C 37 were isolated upon treatment of P. lobata cell cultures with an elicitor yeast extract.97 It was further proposed that these metabolites are probably formed by non-specific oxidation of daidzein 38 with a peroxidase.

OH O OH O

O OH O HO O HO OH 35 O O O

HO O 36

O O

O O HO O O

HO 37

In order to develop a facile method for the synthesis of compounds 35, 36 and 37, daidzein 38 was subjected to oxidative dimerization under various conditions. However,

176 177 when FeCl3/DMF, FeCl3/AlCl3/CH3NO2, FeCl3/CH3OH/H2O, FeCl3 (solid phase),

92 178 179 160 PhI(AcO)2, CuCl2/PhCH2NH2/MeOH and photochemical conditions were used, no reaction was observed and the unreacted starting material was recovered (Scheme

98).

FeCl3, DMF

FeCl3, MeOH, H2O

FeCl3 solid phase

OH K3[Fe(CN)6], Na2CO3, H2O O

CuCl , PhCH NH , MeOH 2 2 2 No reaction HO O PhI(OAc) , acetonitrile 38 2

PhI(OAc)2, DMF

FeCl3, AlCl3, MeNO2

Ph2CO, hv, acetone

Scheme 98

When iodine was used as an oxidant180 for the oxidative dimerization of daidzein 38, 3’- iododaidzein 246 was isolated as the main product whereas oxidation with ceric ammonium nitrate gave 3’-nitrodaidzein 247 as the sole product. 3’-Nitrodaidzein 247

(also known as K3D3) is a natural product isolated from the culture broth of genetically engineered Streptomyces K2181 and its synthesis has not been reported previously.

When the oxidation was carried out using potassium ferricyanide under aqueous and non-aqueous conditions, a complex mixture was obtained (Scheme 99).

93 OH O I , KOH, MeOH 2 I

HO O 246 OH OH O O (NH ) Ce(NO ) 4 2 3 6 NO2 AcOH HO O HO O 38 247

K3[Fe(CN)6], NaOH, H2O Complex mixtures OR K3[Fe(CN)6], TEA, MeOH

Scheme 99

Ueno et al.182 have described the oxidative dimerization of a variety of phenolic substrates such as naphthol 248 by aerial oxidation in the presence of CuCl as catalyst

(Scheme 100).

COOMe

OH air, CuCl, DMF OH 70°C, 95% OH COOMe

COOMe 248 249

Scheme 100

The application of these reaction conditions for oxidative dimerization of daidzein 38 gave kudzuisoflavone-A 35 in 10% yield (Scheme 101).

OH OH OOH O O CuCl, DMF 100°C, 10% O HO O HO O HO

38 35 Scheme 101

One of the main reasons for the low yield in this reaction is the extremely low solubility of the dimer 35 in most of the organic solvents, which makes its isolation and

94 purification very difficult. The main reason why the reaction occurs exclusively in ring-B is due to the presence of a carbonyl group at C-4 which deactivates ring-A towards oxidative dimerization.

5.3.2. Oxidative dimerization of phenoxodiol (111)

Phenoxodiol 111 was subjected to oxidative dimerization under various conditions.

Unlike daidzein 38, phenoxodiol 111 does not have a carbonyl group in ring-A. As a result, both ring-A and ring-B are highly activated and reactive. Therefore, a range of symmetrical and unsymmetrical dimeric products were expected (Scheme 102).

HO O 111 Oxidative dimerization OH OH HO OH HO OH

Possible symmetrical O O dimers O O O O

OH HO OH OH OH OH 251 252 250 OH OH OH OH HO HO

O O Possible unsymmetrical O O dimers O O

OH OH OH OH OH OH 253 254 255

Scheme 102

95 Attempts to oxidatively dimerize phenoxodiol 111 with iodine in alkaline methanol180 gave a complex mixture of products while no reaction was observed when

179 CuCl2/methylbenzylamine 256 system was used for the oxidation (Scheme 103).

I , KOH, MeOH 2 Complex mixture OH r.t.

HO O 111 256,CuCl2,MeOH No reaction r.t. Scheme 103

When phenoxodiol 111 was treated CuCl at 100 C, a polymeric material was obtained within 15 min. (Scheme 104).

air, CuCl Polymeric product HO O 100oC, DMF, 15 min 111

Scheme 104

Therefore, the same reaction was attempted at r.t, and air was bubbled through a mixture of phenoxodiol 111 and CuCl in DMF to yield compound 257 as the major product after column chromatography. Two minor compounds were also present but could not be isolated in pure form and hence were not characterized.

The 1H NMR spectrum of compound 257 indicated it to be a dimeric compound (Figure

22) while high resolution mass spectrometry gave molecular ion at 501.1307 (M + Na)+ which corresponded to the molecular formula of C30H22O6. This together with NMR data confirmed the formation of a dimeric compound. In order to determine its structure, the product was subjected to extensive 1D and 2D NMR spectroscopy experiments.

96 Figure 22. 1H NMR of compound 257

The 1H NMR spectrum of compound 257 showed a doublet at 3.92 (J = 11.7 Hz, 1H) and a doublet of doublets at 4.62 (J = 0.8, 11.7 Hz, 1H) indicating the presence of two geminally coupled protons. A doublet at 5.08 (J = 1.8 Hz, 2H) indicated the presence of a CH2 group, and a doublet at 5.53 (J = 0.8 Hz, 1H) indicated a CH group attached to an oxygenated carbon. Doublets at 6.36 (J = 2.3 Hz, 1H) and 7.28 (J = 8.3 Hz, 1H) along with a doublet of doublets at 6.51 (J = 2.3, 8.3 Hz, 1H) indicated the presence of a 1,3,4-trisubstituted benzene ring. Doublets at 6.81, 6.84, 7.36 and 7.38 each (J =

8.7 Hz, 2H) indicated the presence of two 1,4-disubstituted benzene rings. Three singlets at 6.34, 6.75 and 6.77 each (1H) indicated the presence of three isolated

2 protons attached to sp carbons. In addition, three broad singlets (D2O exchangeable) at 8.3, 8.45 and 8.53 each (1H) corresponded to three hydroxyl groups.

The 13C NMR spectrum together with DEPT-135 confirmed the presence of one

2 quaternary carbon at 49.5, two CH2 groups, 11 protonated sp carbons and 12 quaternary sp2 carbons.

97 This information, together with COSY, NOESY, HMQC and HMBC correlations, indicated the following structure for the dimer 257.

12 O 11a H 10 O 1 13a 7a 13b 2 8 7 6a 6 2'' HO O 4a OH 3'' H 4 a Hb 2' HO 3'

257 H H H H H O H H O H O H O H H H

H H H H HO H H O OH HO H H O OH H H H H H H H H HO H HO H

Important NOEs for dimer 257 Important HMBCs for dimer 257

The cis stereochemistry at the ring junction was indicated by the presence of NOE between H13a and H2’, H6’ protons.

Attempts to crystallize this product from various solvents such as methanol, acetonitrile and toluene to obtain a single crystal suitable for X-ray crystallographic studies were unsuccessful.

A plausible mechanism for the formation of dimer 257 is depicted in Scheme 105.

98 O Ar

O 258 H Ar H Ar Ar -2 e- + HO O -H O O HO O 111 258 111

Ar = OH O O O Ar H O H Ar H -H+ Ar Ar HO O HO O

257 259

Scheme 105

The oxidative dimerization of phenoxodiol 111 with thallium(III) trifluoroacetate (TTFA) was investigated next. When phenoxodiol 111 in trifluoroacetic acid (TFA) was treated with TTFA, TLC analysis after 15 min showed an absence of the starting material and formation of one major and one minor product. The high resolution mass of the major product 260 was found to be 279.0630 (M + Na+), which corresponded to a molecular formula of C15H12O4. This indicated that TTFA has somehow introduced one oxygen atom into the molecule. In order to elucidate its structure, the compound was subjected to 13C, DEPT-135 and 2D NMR spectroscopy experiments. The 1H NMR spectrum of the major product 260 showed two doublets at 6.85 and 7.50 each (J = 8.7 Hz, 2H) indicated that ring-B was intact in the molecule (Figure 23). Also doublets at 6.45 (J =

2.6 Hz, 1H) and 7.08 (J = 8.3 Hz, 1H), and a doublet of doublets at 6.48 (J = 2.6, 8.3

Hz, 1H) indicated the absence of any additional functionality in ring-A. D2O exchange resulted in the disappearance of a doublet at 5.91 (J = 7.1 Hz, 1H) and singlets at

8.37 (1H) and 8.42 (1H) indicating the presence of three hydroxyl groups in the molecule. This evidence pointed towards the possible hydroxylation of the C2 or C4 carbon atoms. 99 Figure 23. 1H NMR spectrum of compound 260

The absence of negative peaks in the DEPT-135 spectrum indicated the absence of a methylene group which meant that the new hydroxyl group had been introduced at the

C2 carbon atom. Hence, the following structure was proposed for the major product

260. OH

HO O OH 260

The structure was further confirmed by 2D NMR spectroscopy, particularly NOESY and

HMBC experiments. The important NOEs and long range 1H-13C correlations observed for this compound are shown in Figure 24.

H OH OH H H H H H H HO O H HO O H OH OH H

Important NOEs for 260 Important HMBCs for 260 Figure 24

100 The high resolution mass spectrum of the second compound 261 isolated from this reaction gave a molecular ion at 517.1263 a.m.u. (M + Na+) which corresponded to the molecular formula C30H22O7. This indicated the dimeric nature of the compound where two phenoxodiol molecules could be present in its structure along with an additional oxygen atom. The simple pattern of its 1H NMR spectrum indicated the dimer has a symmetrical structure (Figure 25).

Figure 25. 1H NMR spectrum of 261

The 1H NMR spectrum of the dimer 261 was found to be similar to that of isoflavene

260 except for the absence of the doublets at 5.91 and 6.21 and the presence of a singlet at 6.72 (1H). D2O exchange resulted in the disappearance of two singlets at

8.42 (1H) and 8.73 (1H) indicating the presence of two hydroxyl groups. The presence of two doublets at 6.66 and 7.28 (each J = 8.7 Hz, 2H) indicated that ring-B was intact. Also the presence of doublets at 6.75 (J = 2.3 Hz, 1H) and 7.12 (J = 8.3 Hz,

1H), and a doublet of doublets at 6.58 (J = 2.3, 8.3 Hz, 1H) ruled out any substitution in ring-A. This leaves the possibility of attachment of oxygen at the C2 or C4 carbon atom. The absence of any negative peak in the DEPT-135 spectrum indicated that the two phenoxodiol molecules must be attached via the C2 carbons, indicating the following structure for the compound 261.

101 OH

HO O O O OH

HO 261

The structure was further confirmed by 2D NMR spectroscopy experiments. The important NOEs and long range 1H-13C correlations observed for the compound 250 are shown in Figure 26.

H OH OH H H H

H HO O H HO O H H H O O H O OH O OH H H

H H H HO HO

H Important NOEs for 261 Important HMBCs for 261

Figure 26

The formation of compound 261 can be explained by the dehydration of compound 260 by the action of TFA.

5.3.3. Oxidative dimerization of isoflavones

From the oxidative dimerization experiments with daidzein 38, it was realized that the main problem in the dimerization of flavonoids lies in their extreme insolubility in most of the solvents, even at elevated temperatures. The products of these reactions were even less soluble and therefore their separation from the impurities and by-products by solvent extraction or chromatography was almost impossible.

102 The solubility of flavonoids in many organic solvents, especially halogenated solvents such as dichloromethane, chloroform, dichloroethane, and ethereal solvents such as

THF or dioxane can be substantially increased by converting the hydroxyl groups into ether or ester derivatives.

Therefore, daidzein 38 was methylated using methyl iodide and KOH to give 4’,7- dimethoxyisoflavone 262 which has good solubility in dichloromethane (Scheme 106).

OH OMe O O

MeI, KOH DMSO, r.t. HO O MeO O 90% 38 262 Scheme 106

However, when dimethoxyisoflavone 262 was subjected to oxidative dimerization using

TTFA or vanadium oxytrifluoride (VOF3), no reaction was observed and the unreacted starting material was recovered (Scheme 107).

OMe VOF 3 OMe O OMe O O

MeO O O MeO O MeO 262 TTFA 263 Scheme 107

These results indicated that dimethoxyisoflavone 262 is not reactive enough to undergo oxidative dimerization. It has been reported that oxidative dimerization is successful

167 only for electron rich substrates and furthermore, addition of BF3·OEt2 is essential for the oxidations and oxidation is not observed if it is omitted.167 It has been proposed that

183 Lewis acids such as BF3·OEt2 or SbF5 increase the electrophilic character of TTFA.

In order to improve solubility and nucleophilicity of isoflavones, it was decided to introduce an additional methoxy group in the ring-B.

103 Resorcinol 72 was reacted with 3,4-dimethoxyphenylacetic acid 264 in the presence of

BF3·OEt2 to give deoxybenzoin 265, which was then cyclized by heating with methanesulfonyl chloride and BF3·OEt2 in DMF to give isoflavone 266. Acetylation of compound 266 with acetic anhydride and pyridine gave the diacetoxyisoflavone 267

(Scheme 108).

OMe OMe OH CH2COOH O

BF3·OEt2 110°C, 52% HO OMe HO OH OMe 265 72 264 DMF, BF3·OEt2 MeSO2Cl 110°C, 74% OMe OMe OMe OMe O O

Ac2O, pyridine 100°C, 87% AcO O HO O 267 266 Scheme 108

Compound 267 has two methoxy groups in ring-B and also has good solubility in dichloromethane; therefore it was expected to undergo oxidative dimerization reaction.

The oxidative dimerization of isoflavone 267 could give a mixture of three isomeric dimeric biisoflavones, namely, 5’-5’’’ isomer 268, 6’-6’’’ isomer 269 and 5’-6’’’ isomer

270 (Scheme 109).

104 OMe OMe O OAc O

5'-5''' isomer O AcO O MeO 268 OMe OMe OMe O O OAc

TTFA 71% 6'-6''' isomer 267 AcO O BF ·OEt 269 3 2 O MeO OMe

OMe OMe O O OAc

5'-6''' isomer AcO O O 270 MeO OMe

Scheme 109

Surprisingly, when isoflavone 267 was treated with TTFA in the presence of BF3 OEt2 in dichloromethane at 0 °C, the 6’-6’’’ biisoflavone 269 was found to be the exclusive product of the reaction and was isolated in 71% yield. The structure was assigned on the basis of the 1H NMR spectrum (Figure 27) which showed two sharp singlets corresponding to H2’, H2’’’ and H5’, H5’’’ protons.

105 Figure 27. 1H NMR spectrum of 269

The structure of dimer 269 was further confirmed by 2D NMR experiments. The important NOESY and HMBC correlations are shown in Figure 28.

OMe OMe H OMe H OMe O O

H H H O OAc H O OAc AcO O H AcO O H H H

O O MeO H MeO H OMe OMe

Important NOEs for 269 Important HMBCs for 269 Figure 28

The oxidative dimerization was found to be high yielding and regioselective.

This result was very encouraging and prompted us to apply this methodology to isoflavones with different substitution patterns in ring-A.

Isoflavone 266 was methylated using methyl iodide and KOH in DMSO to give 3’,4’,7- trimethoxyisoflavone 271 in 90% yield (Scheme 110).

106 OMe OMe OMe OMe O O MeI, KOH

DMSO, r.t. HO O MeO O 90% 266 271 Scheme 110

When trimethoxyisoflavone 271 was subjected to oxidative dimerization, the expected

6’-6’’’ dimer 272 was obtained in 76% yield. In addition, another compound 273, formed by partial demethylation of dimer 272 was also isolated in 10% yield (Scheme 111).

OMe OMe O O OMe

MeO O O MeO 272 OMe TTFA, BF ·OEt 76% 271 3 2 OMe DCM, 0°C 10% OH O O OMe

MeO O O MeO 273 OMe Scheme 111

Isoflavone 274, prepared from 5-methylresorcinol and 3,4-dimethoxyphenylacetic acid

264 in three steps following the route outlined in Scheme 108, was subjected to oxidative dimerization using TTFA, when the expected dimer 275 was isolated in 78% yield (Scheme 112).

107 OMe OMe OMe OMe Me O Me O O OAc TTFA, BF3·OEt2 DCM, 0°C AcO O AcO O 76% O Me MeO 274 OMe 275 Scheme 112

Similarly, isoflavones 276, 278 and 280 upon reaction with TTFA gave the expected dimeric products in 277, 279 and 281 in 65%, 74%, and 76% yields respectively.

OMe OMe OMe OMe O OAc O O OAc TTFA, BF3·OEt2 DCM, 0°C AcO O AcO O 65% OAc O OAc MeO 276 OMe 277 OMe OMe OMe OMe O Me O O OMe TTFA, BF3·OEt2 DCM, 0°C MeO O MeO O 74% Me O Me MeO 278 279 OMe OMe OMe O Me O OAc

AcO O OMe Me O OMe MeO O 281 76% OMe TTFA, BF3·OEt2 OMe DCM, 0 °C 22% OH AcO O O Me Me 280 O OAc

AcO O Me O MeO 282 OMe Scheme 113

108 In addition to this, isoflavone 280 also gave the monodemethylated compound 282 in

22% yield (Scheme 113).

These results clearly indicate that activated isoflavones can be oxidatively dimerized in good to excellent yields in a regioselective manner using TTFA. The high regioselectivity in these reactions can be explained by the unique structure of isoflavones. The ring-B and the benzopyran oxygen in the isoflavones are separated by a double bond. Therefore, isoflavone 283 is a hybrid of structures 284, 285 and 286 (in addition to the Kekule structures) (Scheme 114).

OMe O

OMe

O 285

OMe OMe H OMe O O O

OMe OMe OMe H O O O 283 284 286

OMe O OMe Net effect O 287 Scheme 114

The net result of this delocalization is the increase in the electron density in ring-B. This increased electron density activates isoflavones towards oxidative dimerization at the

C2’, C4’ and C6’ positions. Since the C4’ position is already occupied and the C2’ position is extremely hindered due to the adjacent methoxy and benzopyran ring, the reaction occurs exclusively at the C6’ position (Figure 29).

109 OMe O Particualrly OMe electron rich

O e density 283

Figure 29

5.3.4. Oxidative dimerization of flavones

Having successfully developed a facile method for oxidative dimerization of isoflavones, the oxidative dimerization of flavones was investigated. Since flavones and isoflavones are merely regioisomers, oxidative dimerization of flavones with similar substitution patterns under similar reaction conditions would be expected to yield 5’-5’’’ or 6’-6’’’ dimers or mixtures thereof.

The starting compound 3’,4’,5,7-tetramethoxyflavone 291 was synthesized from acetophenone 192 in three steps as outlined in Scheme 115.

OH O OMe O

Me2SO4, K2CO3 acetone, reflux HO OH 72% MeO OH 192 288

289, NaOH EtOH, 87%

OMe O OMe O

I2 , DMSO o MeO O 150 C, 81%MeO OH

291 OMe 290 OMe OMe OMe

Scheme 115

Acetophenone 192 was methylated by refluxing with dimethyl sulfate in the presence of

K2CO3 in acetone to give 2’-hydroxy-4’,6’-dimethoxyacetophenone 288 in 72% yield which upon condensation with 3,4-dimethoxybenzaldehyde 289 in the presence of

110 ethanolic NaOH gave chalcone 290 in 87% yield. Oxidative cyclization184 of chalcone

185 290 using I2/DMSO gave flavone 291 in 81% yield (Scheme 115).

Treating flavone 291 with TTFA in the presence of BF3·OEt2 in dichloromethane at 0

C, did not produce the desired dimer 292. Formation of a new product was observed when the temperature of the reaction was increased to r.t. However, after continuing the reaction for 3 h, no further progress was observed, hence the reaction was worked up to yield compound 293. Surprisingly, the 1H NMR spectrum of the isolated product showed doublets at 6.98 (J = 8.6 Hz, 1H) and 7.66 (J = 1.9 Hz, 1H), and a doublet of doublets at 7.64 (J = 1.9, 8.6 Hz, 1H) indicating that ring-B was unchanged. The doublets at 6.37 and 6.56 corresponding to H6 and H8 respectively in the starting material were replaced by a singlet at 6.43 (1H). This indicated that the reaction had taken place at C8 instead of ring-B. The shielding of the C8 carbon atom from 96.0 in the starting material to 64.8 in the product indicated possible iodination of C8 instead of dimerization (Scheme 116).

OMe MeO OMe O O OMe

MeO O OMe O O OMe TTFA OMe BF ·OEt OMe 3 2 OMe O 292 MeO O 0oC to r.t. 291 OMe OMe MeO O I 293 OMe OMe Scheme 116

This was an unexpected result and it indicated that the ring-B in flavones is much less activated than ring-B in isoflavones. Flavone 291 undergoes electrophilic thallation at

C8 to give an arylthallium compound which, during work-up, reacts with KI to give 8- iodoflavone 293.167,186

111 In order to avoid iodination at C8, oxidative dimerization of 3’,4’-dimethoxyflavone 296 was investigated. Flavone 296 was synthesized from 2’-hydroxyacetophenone 294 by condensation with 3,4-dimethoxybenzaldehyde 289 followed by cyclization (Scheme

117).

O O O

289, NaOH I2 , DMSO EtOH, 70% 150oC, 88% OH OH O

294 295 OMe 296 OMe OMe OMe

Scheme 117

However, when flavone 296 was reacted with TTFA in the presence of BF3·OEt2, no reaction was observed at 0 °C, at r.t. or even under reflux when analysed by TLC.

Upon work-up, only the unreacted starting material was isolated (Scheme 118).

TTFA, BF ·OEt 3 2 No reaction o O DCM, 0 C to reflux

296 OMe OMe

Scheme 118

This result supports the observation that the ring-B of flavones such as 297 is much less activated than ring-B of isoflavones. This can be explained as follows. In flavones, ring-B is in conjugation with the carbonyl group and therefore flavone 297 is a hybrid of structures 298, 299 and 300 (Scheme 119).

112 O

O 299 OMe OMe

O O O H O O O 300 298 H OMe 297 OMe OMe OMe OMe OMe

Net effect O 301 OMe OMe Scheme 119

The net result of this delocalization is the lowering of the electron density in ring-B.

O electron density O

297 OMe OMe

Figure 30

This decreased electron density is responsible for the unreactivity of flavones towards oxidative dimerization.

5.4. Conclusion

Different classes of flavonoids give rise to a variety of products when subjected to oxidative dimerization conditions. Daidzein 38 was found to be resistant towards oxidative dimerization whereas dihydroxyisoflavene 111 gave different products depending upon the oxidation conditions. Activated isoflavones gave novel 6’-6’’’

113 biisoflavone dimers regioselectively in good yield. However, related flavone analogues were unreactive under similar reaction conditions.

114 CHAPTER 6

SYNTHESIS OF DIMERS BY

SONOGASHIRA COUPLING

115 6.1. Introduction

Over the past 25 years, palladium catalyzed coupling of terminal alkynes with a vinyl or aryl halide, also known as the Sonogashira coupling has become one of the most attractive and powerful tools for the synthesis of aryl-alkynes and vinyl-alkynes

(Scheme 120).187-190

X R

OR Pd cat. + H R OR CuI X R

Scheme 120

This reaction has been extensively studied and numerous modifications to this reaction have been reported. These include the use of various solvents,191,192 phase-transfer catalysts,193 new catalyst systems,194-197 copper free versions,93,198,199 biphasic versions,200 use of hydrogen atmosphere to suppress the homocoupling of the terminal alkynes,201 polymer supported Pd-triazine complex202 and solid supported Pd- catalyst.203 In addition to the copper salts, use of other metal co-catalysts such as zinc, tin, boron or aluminium salts have also been reported.204-206 Although the exact mechanism of the homogeneous copper-cocatalyzed Sonogashira reaction is unknown,207 the generally accepted mechanism is depicted in Scheme 121.207

Pd0L Ar R 4 Ar-X

Reductive Oxidative elimination addition

L L Ar' Pd R Ar' Pd X L Trans- metallation L

CuX Cu R

H R

Scheme 121

116 The first step involves a fast oxidative addition of Ar-X to the Pd(0) catalyst generated from the initial palladium complex. The next step is the rate determining transmetallation step involving the copper acetylide formed in the Cu-cycle and the aryl- palladium complex. This is followed by trans/cis isomerization and reductive elimination to give the final coupled alkyne with regeneration of the catalyst.

The reaction can be applied to the substrates carrying various functional groups and has found applications in the synthesis of numerous natural products, pharmaceuticals and enediyne antibiotics, such as neocarzinostatin 302 and dynemicin 303.208

OH O Me MeO O COOH O O OH O HN O O COOH OMe O O NH OH O OH HO O OH 302 303

Terbinafine (Lamisil) 304 is a pharmaceutically important compound used in the treatment of superficial fungal infections while tazarotene 305 is a member of new generation receptor-selective, synthetic retinoids, for the effective treatment of acne, psoriasis and photoaging.209

Me Me COOEt Me N Me N

S 304 305

The the acetylenic group is frequently present in bioactive natural products as well as pharmaceuticals. Therefore, synthesis of dimeric flavonoids linked via an acetylenic bridge was undertaken. 117 It was thought that reaction of two equivalents of halogenated flavones or isoflavones

306 and one equivalent of acetylene should give the dimer linked via an acetylenic bridge such as compound 307 (Scheme 122).

O O O X Pd(0) R + H H R R CuI O acetylene O O 306 307 2 Equivalents Dimer isoflavone or flavone Scheme 122

Acetylene is a highly flammable gas and is rather difficult to handle under laboratory conditions. Another problem with the use of acetylene gas is the maintainance of the desired stoichiometry of the reaction. Incomplete absorption of acetylene would leave unreacted halogenated compound in the reaction mixture, whereas excess acetylene would result in the formation of monosubstituted alkynes as impurities.

H SiMe3 H H OH OH 308 309 195 Ethynyltrimethylsilane 308 has been extensively used as a protected acetylene.210-214 It is a liquid at room temperature and therefore, can be easily handled and added in stoichiometric amounts. The TMS protecting group can be easily removed by treatment with fluoride ions or a base. Propargyl alcohol215 309 has also been used as a protected acetylene. It can be deprotected by hydrolysis with a base or by oxidation with MnO2 and alkaline hydrolysis. 2-Methyl-3-butyn-2-ol 195 is another masked acetylene where the alcohol functionality can be removed by treatment with KOH or

NaOH212,214,216-218 in butanol or in situ with a phase-transfer catalyst.

118 6.2. Results and discussion

Diacetyldaidzein 310 was hydrolysed and iodinated in situ using iodine in alkaline methanol to give 3’-iododaidzein 246. The hydroxyl groups were protected by methylation using methyl iodide in the presence of KOH in DMSO to give 3’-iodo-4’,7- dimethoxyisoflavone 311 (Scheme 123).

OAc OH OMe O O O

KOH, MeOH I MeI I AcO O I2, r.t., 88% HO O KOH, DMSO MeO O 55% 310 246 311

Scheme 123

Iodoisoflavone 311 was reacted with ethynyltrimethylsilane 308 in the presence of catalytic amounts of PdCl2(PPh3)2 and CuI. DMF was chosen as solvent since it dissolves most of the flavonoid compounds. Triethylamine was used both as base and co-solvent. The mixture was heated for 7 h and chromatographic purification after work- up yielded the desired product 312 in 56% yield. The TMS protecting group was removed by stirring with K2CO3/MeOH and the resulting isoflavone 313 was reacted with another equivalent of iodoisoflavone 311 in the presence of PdCl2(PPh3)2 and CuI in TEA/DMF solvent system to yield the dimer 314 in 75% yield (Scheme 124).

OMe O O OMe 308 I PdCl2(PPh3)2, CuI SiMe3 TEA, DMF MeO O 56% MeO O 311 312

K2CO3/MeOH 40% 95%

OMe O O OMe 311 O OMe H PdCl2(PPh3)2, CuI MeO O TEA, DMF MeO O O 75% MeO 313 314 Scheme 124

119 Although the yield in the individual reaction steps of this sequence were reasonable, the overall yield was just 40%. It is important to note that the reagents and reaction conditions in steps 1 and 3 of the sequence are exactly the same. Therefore, if the deprotection of the silyl group could be carried out in situ then it would be possible to carry out all the three steps in one-pot.

6.2.1. One-pot synthesis

Grieco et al. have reported a one-pot synthesis of biarylethynes.219

308 0 Pd , CuI, DBU, H2O X benzene, 60-80 °C R R R 315 316

Scheme 125

It involves refluxing a mixture of an aryl halide 315 with ethynyltrimethylsilane 308, CuI and palladium catalyst in benzene, followed by addition of 0.4 equivalents of water and

6.0 equivalents of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for in situ deprotection of the TMS group. One more equivalent of aryl halide 315 is added and the reaction is continued to give the dimeric product 316 (Scheme 125).

A one-pot synthesis of isoflavone dimers was investigated using similar conditions.

However, benzene being a carcinogenic solvent was replaced with DMF. Another advantage of using DMF is the high solubility of flavonoids in this solvent.

It has been reported that the presence of residual oxygen in the reaction mixture can reoxidize the Pd(0) species.220 Therefore, degassing of the reaction mixture is crucial for the success of the reaction. Insufficient degassing leads to incomplete reaction due to deactivation of the catalyst and also gives rise to higher amounts of the homocoupled by products such as compound 317 (Scheme 126).

120 Pd(0), CuI Me3Si H Me3Si SiMe3 (iPr)2NH 308 317 Scheme 126

The degassing was done by heating the reactants and the solvent for 30 min while sweeping the headspace with argon prior to the addition of catalyst.220

Initially, reaction using a model substrate 3-iodo-4-methoxybenzaldehyde 319 was investigated. Aldehyde 319 was chosen as a model substrate because its substitution pattern resembles the substitution pattern of the actual substrates and it can be easily synthesized from readily available starting materials. 4-Methoxybenzaldehyde 318 was iodinated according to a reported procedure221 with the exception that the reaction was carried out at 80 °C instead of 60 °C (Scheme 127).

OMe OMe I ICl, AcOH 80°C, 89%

CHO CHO 318 319

Scheme 127

A mixture of iodobenzaldehyde 319, triethylamine and DMF was heated at 80 °C under an argon atmosphere. This was followed by the addition of PdCl2(PPh3)2, CuI and ethynyltrimethylsilane 308. After completion of the initial coupling reaction, DBU was added followed by addition of a second equivalent of iodobenzaldehyde 319.

Continuation of the reaction for 1.5 h furnished the dimeric compound 322 in an overall yield of 86% (Scheme 128).

121

OMe OMe OMe I 308 PdCl2(PPh3)2, CuI SiMe3 DBU H TEA, DMF CHO CHO CHO 319 320 321 Not isolated 86%

OMe OMe 319 PdCl2(PPh3)2, CuI TEA, DMF

CHO CHO 322

Scheme 128

Thus, the one-pot reaction not only improved the yield, but also reduced the amounts of catalyst and solvents used in the reaction, and the time spent on the work-up and isolation of the intermediates.

With these encouraging results, the one-pot methodology was applied to the synthesis of isoflavone and flavone dimers.

6.2.2. Synthesis of isoflavone-isoflavone dimers

Iodoisoflavone 311 was reacted with ethynyltrimethylsilane 308 under one-pot reaction conditions as described above. The intermediate was not isolated and treated in situ with DBU and another equivalent of iodoisoflavone 311 to yield the dimer 314 in 75% yield (Scheme 129).

122 OMe O O OMe 308 SiMe3 I PdCl2(PPh3)2, CuI TEA, DMF MeO O MeO O 311 312 Not isolated

75% DBU

O OMe OMe O OMe O 311 H MeO O MeO O MeO O 314 313 Not isolated Scheme 129

6.2.3. Synthesis of flavone-flavone dimers

Iodoflavones required for the dimerization reaction were synthesized in two steps from their respective acetophenones. In the first step, appropriately substituted acetophenones (294, 77, 80 and 288) were reacted with 3-iodo-4- methoxybenzaldehyde 319 in the presence of excess KOH to give chalcones (323,

325, 327 and 329). Oxidative cyclization was then carried out by heating the chalcones in DMSO in the presence of a catalytic amount of iodine to give flavones 324, 326, 328 and 330 (Scheme 130). The yields and the nature of R1 and R2 substituents are depicted in Table 5.

R1 O R1 O R1 O

319, KOH I2, DMSO I 150°C I R2 OH EtOH, r.t. R2 OH R2 O

OMe OMe 294, 77, 323, 325, 324, 326, 80, 288 327, 329 328, 330

Scheme 130

123 R1 R2 Product (% yield) Product (% yield)

H H 323 (60) 324 (91)

MeO H 325 (64) 326 (92)

H MeO 327 (50) 328 (95)

MeO MeO 329 (50) 330 (95)

Table 5

The iodoflavones 324, 326, 328 and 330 thus obtained were dimerized using the one- pot procedure to yield dimers 331-334 (Scheme 131). The yields are depicted in Table

1 R O R1 O MeO

O R2

2 I R O R2 O

OMe OMe O R1 324, 326, 331, 332, 328, 330 333, 334 Scheme 131

R1 R2 Product (% yield)

H H 331 (80)

MeO H 332 (90)

H MeO 333 (90)

MeO MeO 334 (84)

Table 6

124 6.2.4. Synthesis of heterocycle-heterocycle dimers

With these results in hand, further experiments were undertaken to confirm whether this methodology could be applied to brominated heterocyclic substrates such as bromophenylbenzofuran 103 or bromophenylindole 110. The reaction with bromophenylindole 110 was found to be sluggish and the dimeric compound 335 was obtained in 56% yield (Scheme 132).

MeO 5 5'' OMe OMe OMe MeO 6' 5' 5''' 6''' 7 7''

MeO N HN NH H 2 2' 3' 3''' 2''' 2'' 110 335 Scheme 132

The 1H NMR spectrum of compound 335 showed two singlets at 3.80 and 3.83 (each

6H) corresponding to four methoxy groups. The H5, H5’’ and H7, H7’’ protons appeared as two doublets at 6.26 and 6.61 (each J = 1.9 Hz, 2H) whereas’ the H2, H2’’ protons appeared as doublet at 7.24 (J = 1.5 Hz, 2H). Doublets at 7.49 and 7.65 (each J =

8.3 Hz, 4H) corresponded to H2’, H6’, H2’’’, H6’’’, and H3’, H5’, H3’’’, H5’’’ protons respectively whereas a broad singlet at 10.32 (2H) was due to two NH protons.

MeO OMe OMe OMe MeO

MeO O O O 103 336

N HN NH H 337 338 Scheme 133

125 However, when this method was used for the dimerization of bromophenylbenzofuran

103 and 5-bromoindole 337, only the unreacted starting materials were recovered

(Scheme 133).

These results indicate that this method is not particularly suitable for the synthesis of dimers from brominated heterocycles.

6.2.5. Synthesis of isoflavone-flavone dimers

In order to further establish the scope of this one-pot reaction, synthesis of unsymmetrical isoflavone-flavone dimers was undertaken. Iodoflavone 328 was first reacted with ethynyltrimethylsilane 308 under usual reaction conditions and then deprotected in situ using DBU. The resulting alkyne was treated with one equivalent of iodoisoflavone 311. The unsymmetrical dimer 341 was obtained after work-up in 82% yield (Scheme 134).

O O 308

PdCl2(PPh3)2, CuI I MeO O TEA, DMF MeO O SiMe3 328 OMe 339 OMe Not isolated

DBU 5' OMe O 6' O O 5 5'' 6 3'' 6'' 311 2' 2''' 2 H MeO 8 O O 8'' OMe MeO O 340 341 MeO 6''' OMe Overall 82% 5''' Not isolated

Scheme 134

The 1H NMR spectrum of compound 341 showed four singlets at 3.91, 3.92, 3.98 and

3.99 (each 3H) corresponding to four methoxy groups whereas the H3’’ and H2 protons appeared as two singlets at 6.69 and 7.97 (each 1H) respectively. Three doublets at

6.85, 7.74 and 8.11 (each J = 2.3 Hz, 1H) corresponded to H8, H2’ and H2’’’ protons

126 respectively, whereas two doublet at 8.11 (J = 8.6 Hz, 1H) and 8.21 (J = 9.0 Hz, 1H) corresponded to protons at H5’’ and H5. The H6’ and H6’’’ protons appeared as two doublets of doublets at 7.59 (J = 2.3, 8.7 Hz, 1H) and 7.81 (J = 2.3, 8.8 Hz, 1H) respectively, whereas the multiplet (5H) at 6.99 corresponded to H5’, H6, H5’’’, H6’’ and H8’’ protons.

Under similar conditions, iodoflavone 326 gave the unsymmetrical dimer 344 in 72% yield (Scheme 135).

OMe O OMe O 308 PdCl2(PPh3)2, CuI I TEA, DMF O O SiMe3 326 342 OMe Not isolated OMe

DBU

5' OMe O 6' O OMe OMe O 5 6 3'' 6'' 311 2' 2''' 2 7'' O H MeO 8 O O 8'' 343 344 MeO 6''' OMe 5''' Not isolated Overall 72%

Scheme 135

The 1H NMR spectrum of compound 344 showed two singlets at 3.92 (3H) and 3.99

(9H) corresponding to four methoxy groups, whereas the H3’’ and H2 protons appeared as two singlets at 6.67 and 7.97 (each 1H) respectively. Three doublets at 6.86,

7.72 and 8.09 (each J = 2.3 Hz, 1H) corresponded to H8, H2’ and H2’’’ protons, whereas doublets at 6.82, 7.16 (each J = 8.3 Hz, 1H) and 8.21 (J = 9.0 Hz, 1H) corresponded to H6’’, H8’’ and H5 protons respectively. The H6’ and H6’’’ protons appeared as two doublets of doublets at 7.62 (J = 2.3, 8.6 Hz, 1H) and 7.81 (J = 2.3,

8.7 Hz, 1H) respectively, whereas a triplet at 7.56 (J = 8.3 Hz, 1H) corresponded to

H7’’. The H6, H5’’’and H5’ protons appeared as multiplet at 6.99 (3H).

127 6.3. Conclusion

The palladium-catalyzed one-pot Sonogashira coupling methodology can be used for the synthesis of symmetrical and unsymmetrical flavone and isoflavone dimers. The method obviates the need for the isolation of the intermediates.

However, this method was not found to be suitable when brominated heterocycles were used as substrates.

128 CHAPTER 7 SYNTHESIS OF DIMERS BY ULLMANN AND SUZUKI- MIYAURA COUPLING REACTIONS

129 7.1. SYNTHESIS OF DIMERS BY ULLMANN COUPLING

7.1.1. Introduction

The formation of a biaryl by the condensation of two molecules of an aromatic halide in the presence of finely divided copper at high temperature is known as the Ullmann reaction (Scheme 136).222-226 It was initially reported in 1901227 and since then it has been widely used for the synthesis of biaryls.

Copper powder R R R 315 345 Scheme 136

Generally, the reaction is carried out using the commercially available form of mechanically pulverized copper known as copper bronze.228 The reactivity of aryl halides with copper is greatly dependent on the structure of the halide. Strongly electron withdrawing substituents such as nitro and carbomethoxyl, predominantly located in the ortho position to the halide, have an activating effect whereas substituents which provide alternative reaction sites, such as amino, hydroxyl and free carboxyl groups greatly limit or prevent the reaction.223

The use of DMF as a solvent in the Ullmann coupling reaction has been reported by

Kornblum et al.229 Not only does it reduce the temperature required for the reaction, but also gives better yields of the biaryl product. DMF has also been reported to be an especially advantageous solvent for the preparation of biaryls containing free aldehyde and ketone groups.230,231 The advantage has been ascribed to its action as a solvent in keeping the copper surface free of copper halide, reactants and products. Another convenient property of DMF is that it can easily be removed from the reaction products by simply pouring the mixture into water.

130 In the Ullmann coupling reaction, if the substrate has hydrogen donor groups such as carboxylic acids, dehalogenation is the predominant side reaction. However, a small amount of dehalogenation also occurs even when no obvious hydrogen source is present.232

7.1.2. Known synthetic methodologies

The Ullmann reaction has been utilized for the synthesis of biflavonoids. Nakazawa et al.233 have reported the synthesis of Ginkgetin 348 in 21% yield by Ullmann reaction between iodoflavones 346 and 347 (Scheme 137).

OBz O

OH O I MeO O 346 OMe HO O Cu OBz O OH 230°C OH HO O

BnO O I OH O 347 OBn 348

Scheme 137

Lin et al.234 have reported the synthesis of 8,8’’-biflavone 350 by Ullmann reaction of iodoflavone 349 in 40% yield (Scheme 138).

OMe O

OMe O OMe Cu, DMF MeO O reflux, 40% MeO O MeO O OMe I OMe OMe O 349 350

Scheme 138

131 Chen et al.235 have reported the synthesis of 3,3’-, 6,6’-, 4’,4’’’-dimethoxy-6,6’’-, 7,7’-,

4’,4’’’-dimethoxy-7,7’’-, 8,8’-, 3’,3’’’- and 4’,4’’’-biflavones by Ullmann reaction of corresponding bromo and iodoflavones.

7.1.3. Results and discussion

Although there are several examples in the literature of the synthesis of symmetrical and unsymmetrical biflavones by the Ullmann coupling reaction, the synthesis of biisoflavones or flavone-isoflavone dimers has not been reported.

Therefore, the synthesis of biisoflavones using this methodology was investigated. For example, it was envisaged that the dimer 35 could be synthesized by Ullmann coupling of 3’-iodoisoflavone 311 followed by demethylation (Scheme 139).

OH OMe O O OH O

I O HO O HO MeO O 35 311 Scheme 139

Initially, the trial reaction was carried out using a model substrate 3-iodo-4- methoxybenzaldehyde 319 which upon heating with copper bronze gave the dialdehyde 351 in 66% yield (Scheme 140).

OMe OMe OMe I Cu, DMF, 150°C 66%

CHO CHO CHO 319 351 Scheme 140

This was an encouraging result; hence it was decided to apply this methodology to the synthesis of isoflavone dimers 35, 39 and 40.

132 However, when iodoisoflavone 311 was subjected to Ullmann coupling in dry DMF under reflux, 4’,7-dimethoxyisoflavone 262 was obtained as the sole product (Scheme

141). Monitoring this reaction by TLC was problematic as isoflavone 311 and isoflavone

262 have the same Rf values under several different solvent systems.

Cu, DMF OMe reflux OMe O O activated Cu I DMF, reflux

MeO O Cu, ultrasound MeO O 311 DMF, reflux 262 Cu powder neat, 240°C

Scheme 141

There are some reports in the literature on the use of freshly activated copper prepared by successively washing the copper bronze with an acetone solution of iodine and hydrochloric acid in the Ullmann coupling reaction.133 However, the use of freshly activated copper did not improve this reaction and dimethoxyisoflavone 262 was again isolated.

The use of ultrasound for activation of copper before the Ullmann reaction has also been reported in the literature.222,236 Therefore, a mixture of isoflavone 311 and copper powder in dry DMF was placed in an ultrasonic bath for 20 min and then refluxed under an argon atmosphere. However, no dimeric product could be obtained from the reaction, the main product being the dehalogenated isoflavone 262 along with some starting material (Scheme 141).

One of the disadvantages of using DMF as a solvent is that it increases the extent of the dehalogenation reaction.230,237,238 Therefore, the Ullmann coupling reaction of isoflavone 311 with neat copper powder at 240 °C under an argon atmosphere was

133 investigated. Once again, no traces of dimeric product could be observed in the 1H

NMR spectrum of the reaction mixture.

Copper(I)-thiophene- 2-carboxylate (CuTC) 355 mediated Ullmann-reductive coupling of substituted aromatic iodides and bromides at r.t. has been reported by Liebeskind et al.239 (Scheme 142). It is reported that this reaction is quite general and can tolerate various functional groups (Table 7).

L L 2.5 eq. CuTC NMP, r.t. X L 352 353 Scheme 142

L X TimeYield (% )

CO2Me I 1 h 97

NO2 I 30 min 92

C=S(NMe2) I 48 h 94

NHCOMe I 30 min 90

CH2NHMe Br 12 h 99

Table 7

CuTC 355 was synthesized from thiophene-2-carboxylic acid 354 and copper(I) oxide in toluene under reflux (Scheme 143).

Cu2O, toluene COOH Dean-Stark COOCu S S 354 355

Scheme 143

134 However, when iodoisoflavone 311 was treated with CuTC 355 in N-methyl-2- pyrrolidinone (NMP), no reaction was observed and the starting material was recovered unchanged (Scheme 144).

OMe O

I CuTC, NMP No reaction MeO O r.t. 311

Scheme 144

Despite these disappointing results, the Ullmann coupling reactions using iodoflavones as substrates were investigated. When iodoflavone 330 was subjected to Ullmann coupling conditions, flavone 356 was obtained as the sole product presumably via demethylation followed by hydrodehalogenation of the substrate (Scheme 145).

OMe O OMe O

Cu, DMF reflux MeO O MeO O

330 356 OMe OH I Scheme 145

This consistent formation of undesired hydro-dehalogenation products in the Ullmann reaction prompted a change of direction. Since this approach had already been used extensively in the synthesis of dimeric flavonoids, it was unattractive from a method development perspective.

Hence, the Ullmann methodology was no longer pursued and an alternate methodology for the coupling reaction was investigated.

135 7.1.4. Conclusion

The Ullmann coupling gave good yield of biaryl compound when applied to the model substrate, iodobenzaldehyde 319. However, it failed to give any dimeric compounds when applied to iodinated isoflavone or flavone, with hydrodehalogenation being the main product of the reaction.

136 7.2. Synthesis of dimers by Suzuki-Miyaura coupling reaction

7.2.1. Introduction

The coupling of organoboron compounds with aryl, alkenyl, and alkynyl halides in the presence of a palladium catalyst is called the Suzuki-Miyaura coupling reaction

(Scheme 146).190,240-246 It is one of the most useful methods of carbon-carbon bond formation and has been extensively used in the synthesis of natural products, pharmaceuticals and advanced materials.247-250

Pd cat. Ar B(OR) Ar' X 2 + base Ar Ar'

Scheme 146

In this coupling method, only a small amount of palladium catalyst is requ ired which is a major advantage over other methodologies where stoichio metric amounts of heavy metals (viz. copper) are needed. The following mechanism has been proposed for the reaction (Scheme 147).251

0 Ar Ar' Pd L4 Ar'X

Reductive Oxidative elimination addition

L L Ar Pd Ar' XPdAr' L Trans- metallation L

XB(OR)2 Ar' B(OR)2 Scheme 147

The first step involves fast oxidative addition of Ar-X to the Pd(0) catalyst generated from the initial palladium complex. The next step is the rate determining transmetallation step involving the aryl boronic acid or boronate ester and the palladium complex. This is followed by trans/cis isomerization and reductive elimination to give the final coupled biaryl with regeneration of the catalyst.

137 Both arylboronic acids and arylboronates can be used in this reaction and these can be easily synthesized by the following two principal me thods:

i) transmetallation between aryl magnesium or lithium intermediates and boron compounds having good leaving groups such as halogen or alkoxy groups (Scheme

148)252,253 and

ArMgX + B(OR)3 Ar B(OR)2

Scheme 148 ii) the more recently developed PdCl2(dppf) catalyzed borylation of aryl halides with tetra(alkoxy)diboron254,255 such as bis(pinacolato)diboron 357 or with dialkoxyboranes such as pinacolborane 358 (Scheme 149).256-259

O O O Pd cat. O Ar' X + B B or B H Ar' B O O O O 357 358 359 Scheme 149

The second method possesses several advantages. It can tolerate various functional groups and does not require inert conditions. The boronate esters prepared by this method are generally stable in air, not affected by moisture, and can be easily chromatographed.260-263

When bis(pinacolato)diboron 357 is used as the boronation reagent, the reaction is normally carried out in the presence of potassium acetate. The following mechanism has been proposed for the reaction (Scheme 150).

138 O Ar' B O Ar'X 0 359 Pd L4

L L Ar' Pd B(OR)2 Ar' Pd X L L

(RO)2BOAc AcO- L Ar' Pd OAc 357 L Scheme 150

The first step involves fast oxidative addition of Ar-X to the Pd(0) catalyst generated from the initial palladium complex. This is followed by displacement of the halide with acetate ion. The next step is the rate determining transmetallation step involving tetraalkoxydiboron and the acetoxy palladium complex. This is followed by trans/cis isomerization and reductive elimination to give the boronate ester with regeneration of the catalyst.

Recently, a CuI catalyzed reaction of pinacolborane 358 with aryl iodides has been reported by Ma et al. (Scheme 151).264 The advantage of this method is that it avoids the use of expensive palladium catalyst.

O CuI, NaH O Ar' I + B H Ar B O THF, r.t. O

358 359 Scheme 151

139 7.2.2. One-pot Suzuki-Miyaura coupling reactions

A one-pot Suzuki-Miyaura coupling reaction has also been reported in the literature.259,265-267

It involves the in situ conversion of an aryl halide 315 into the boronate ester intermediate followed by the addition of a second equivalent of aryl halide 315 together with a second palladium catalyst and base to afford the biaryl product 345 (Scheme

152). X X

i) borylation ii) Suzuki-Miyaura R R R R coupling 315 315 345

Scheme 152

Avoiding the isolation of arylboronates via the one-pot Suzuki-Miyaura procedure is highly desirable because it avoids the use of large quantities of solvents in the isolation of the intermediates and also reduces the time required to complete the reaction. This method is particularly useful in cases where the boronate intermediates are unstable.

In order to carry out the two steps in one-pot effectively, the boronate ester formation needs to be reasonably clean. Furthermore, a proper selection of reaction conditions, such as catalyst, solvent, base and temperature is also essential.

140 7.2.3. Results and discussion

OMe OMe O OMe OMe I B 357, PdCl2(dppf) O 319, Pd(PPh3)4 KOAc, DMF aq. NaOH 100°C Overall 77% CHO CHO CHO CHO 319 360 351 Scheme 153

Once again the model substrate, 3-iodo-4-methoxybenzaldehyde 319, was treated with bis(pinacolato)diboron 357, in the presence of PdCl2 (dppf) and potassium acetate in dry DMF. Upon complete conversion (TLC) of the aryl halide into the boronate intermediate 360, another equivalent of iodobenzaldehyde 319 was added followed by addition of Pd(PPh3)4 and aq. NaOH solution. The reaction was continued for further 4 h and after work-up and chromatographic purification, dialdehyde 351 was obtained in

77% yield (Scheme 153).

Encouraged by this result, the same methodology was applied for the preparation of flavone dimers. Iodoflavones 324 and 326 were subjected to the one-pot reaction conditions described above and the resulting dimers 361 and 362 were obtained in 63 and 59% yields respectively (Scheme 154).

O O MeO

O I O O

OMe OMe 324 361 O OMe O OMe O MeO

O I O O OMe OMe 326 362 O OMe

Scheme 154

141 In order to assess the scope of this reaction, this methodology was applied to the synthesis of dimeric indole and benzofuran derivatives. In general, the coupling reaction with brominated compounds took 12 to 16 h to complete, and even though the reactions appeared complete on TLC, the yields of the dimeric compounds were between 37 and 53%. The following dimers were synthesized by this methodology and their yields are summarised in Table 8.

Entry Substrate Product % Yield

Br HN NH 1 41 N H 363 364

Br 2 HN NH 37 N H 337 365

Br N 3 H N N 44 366 H 367 H

NH HN N 4 H 50 Br 368 369

MeO OMe OMe MeO Br 5 37 HN HN 2 110 370

142 MeO OMe OMe MeO Br

6 O 42 O 2 103 371

OMe OMe

7 Br 36 MeO N MeO N H H 372 373 2

OMe MeO MeO OMe OMe MeO Br 8 39 O O 374 375 2

Table 8

The 2-bromophenylindole 372 was synthesized by heating ketone 107 in silicone oil following a literature procedure (Scheme 155).268

Br OMe OMe O silicone oil Br 130°C, 53% MeO N MeO N H H 107 372 Scheme 155

The trimethoxybenzofuran 374 was synthesized from 3,4,5-trimethoxyphenol 88 and 4- bromophenacylbromide 101 followed by cyclization of the interme diate 376 with trifluoroacetic acid (Scheme 156).269

143 Br Br OMe OMe MeO O MeO O KHCO3, acetone reflux, 58% MeO OH Br MeO O 88 101 376 Br

OMe MeO TFA, r.t. 35% MeO O 374 Scheme 156

However, when 3-bromoindole 377 and 3-bromo-2-phenylindol 380, prepared by brominating indole 121 and 2-phenylindole 379 in DMF respectively,270 were subjected to a coupling reaction, complex mixtures of products were obtained (Scheme 157).

Br2, DMF N 65% N H H HN NH 121 377 378 Br Br , DMF Ph 2 Ph N 85% N H H HN NH 379 380 Ph Ph 381 Scheme 157

Considering the possible sensitivity of 3-bromoindoles under coupling conditions, the coupling reaction was attempted using 3-bromo-1-methylindole 383 as a substrate. 3- bromo-1-methylindole 383 was prepared by methylation of indole 121 using MeI/KOH in DMSO271 followed by bromination270 with bromine in DMF (Scheme 158).

144 Br

MeI, KOH Br2, DMF DMSO 87% N N N N N H 99% Me Me Me Me 121 382 383 384 Very unstable Scheme 158

However, indole 383 was found to be highly unstable and rapidly decomposed.

Therefore, the three 3-bromoindole precursors 377, 380 and 383 were considered to be unsuitable substrates for the one-pot Suzuki-Miyaura reactions.

7.4. Conclusion

The palladium-catalyzed in situ Suzuki-Miyaura reaction works well for iodoflavone, bromoindole and bromobenzofuran substrates. The method obviates the need for the isolation of the boronic acid or boronate ester intermediates which are often difficult to isolate in pure form. However, the method is not suitable for the dimer ization of highly reactive 3-bromoindoles and gives a complex mixture of products.

145

CHAPTER 8

EXPERIMENTAL

146 General information

All reactions requiring anhydrous conditions were performed under an argon atmosphere.

Methanol (MeOH), ethanol (EtOH), pentane and ethyl acetate were obtained from commercial sources. Light petroleum (hexane) was distilled and the fraction 60-80 °C was used for chromatography. Anhydrous ether and tetrahydrofuran (THF) were distilled from sodium metal and benzophenone under argon. Anhydrous dichloromethane (DCM) was freshly distilled from calcium hydride under argon.

Anhydrous acetonitrile was freshly distilled from phosphorus pentoxide.

Melting points were measured using a Mel-Temp melting point apparatus, and are uncorrected.

Microanalyses were performed on a Carlo Erba Elemental Analyzer EA 1108 at the

Campbell Microanalytical Laboratory, University of Otago, New Zealand.

NMR spectra were recorded in the designated solvents on a Bruker Avance DPX300

(300 MHz) or a Bruker DMX600 (600 MHz) spectrometer at the designated frequency and were internally referenced to the solvent peaks. 1H NMR spectral data are reported as follows: chemical shift measured in parts per million (ppm) downfield from TMS (); multiplicity; observed coupling constant (J) in Hertz (Hz); proton count; assignment.

Multiplicities are reported as singlet (s), broad singlet (bs), doublet (d), triplet (t), quartet

(q), quintet (p), multiplet (m), doublet of doublets (dd), doublet of doublet of doublets

(ddd), broad (br), buried, and combinations of these. 13C NMR chemical shifts are reported in ppm downfield from TMS (), and identifiable carbons are given. Acid-free deuterated chloroform was obtained by passing the solvent through a short column of anhydrous K2CO3 immediately prior to use. 147 Low resolution mass spectrometric analysis was carried out at the Bioanalytical Mass

Spectrometry Facility, UNSW, and the spectra were recorded on either

Q-Star Pulsar API (Applied Biosystems)

Q-TOF Ultima API (Micromass)

Voyager DE STR MALDI TOF (Applied Biosystems) mass spectrometers.

High resolution mass spectra were recorded on either a Bruker FT-ICR MS (EI) or a

Micromass ZQ2000 (ESI) mass spectrometer at the School of Chemistry, UNSW. High resolution mass is reported upto 4 decimal places and the low resolution mass is reported upto 2 decimal places.

Infrared spectra were recorded with a Thermo Nicolet 370 FTIR spectrometer.

Ultraviolet-visible spectra were recorded using a Varian Cary 100 Scan spectrometer, and the absorption maxima together with the molar absorptivity () are reported.

Column chromatography was carried out using Merck 230-400 mesh ASTM silica gel.

Preparative thin layer chromatography was carried out on 3×200×200 mm glass plates coated with Merck 60GF254 silica gel.

Reactions were monitored using thin layer chromatography, performed on Merck DC aluminium foil coated with silica gel GF254. Compounds were detected by short and long wavelength ultraviolet light and with iodine vapour.

148 2,4,4’-Trihydroxydeoxybenzoin (74)

A mixture of resorcinol 72 (5.5 g, 50 mmol), 4- OH O hydroxyphenylacetic acid 73 (7.6 g, 50 mmol) and

BF3·OEt2 (127 mL, 1 mol) was heated at 110 C for 1.5 HO OH h. The mixture was cooled to 5 C and maintained at the same temperature for 1 h. The precipitated product was filtered, washed successively with sodium acetate solution

(250 mL, 10%), water (50 mL) and dried. The title compound was obtained as a yellow

272 1 solid (9.0 g, 73%). M.p. 189-191 °C, lit. 192 °C; H NMR (300 MHz, DMSO-d6):

4.11 (s, 2H, CH2), 6.23 (d, J = 2.7 Hz, 1H, H3), 6.36 (dd, J = 2.7, 8.7 Hz, 1H, H5), 6.68

(d, J = 8.4 Hz, 2H, H3’, H5’), 7.06 (d, J = 8.4 Hz, 2H, H2’, H6’), 7.91 (d, J = 8.7 Hz, 1H,

H6), 9.28 (s, 1H, 4’ OH), 10.67 (s, 1H, 4 OH), 12.59 (s, 1H, 2 OH).

Daidzein (38)

A mixture of deoxybenzoin 74 (500 mg, 2.05 mmol), OH O triethyl orthoformate (5 mL, 30 mmol), pyridine (0.9 mL,

11.39 mmol) and piperidine (2 drops) was heated at HO O

120 C for 3.5 h. The reaction mixture was cooled to r.t. and poured over a mixture of conc. hydrochloric acid (2 mL) and ice (10 g) and stirred for 5 min. The product was filtered, washed with water (10 mL) and air dried to give title compound as a light pink

138 1 solid (350 mg, 67%). M.p. 290 °C (dec), lit. 290 °C; H NMR (300 MHz, DMSO-d6):

6.79 (d, J = 8.6 Hz, 2H, H3’, H5’), 6.84 (d, J = 2.1 Hz, 1H, H8), 6.92 (dd, J = 2.1, 8.7

Hz, 1H, H6), 7.36 (d, J = 8.6 Hz, H2’, H6’), 7.95 (d, J = 8.7 Hz, 1H, H5), 8.28 (s, 1H,

H2).

4’,7-Diacetoxyisoflavone (75) OAc A mixture of daidzein 38 (1.0 g, 3.93 mmol), pyridine O

(1.12 mL, 14.2 mmol) and acetic anhydride (6.0 mL, AcO O

149 64 mmol) was heated with stirring at 110 C for 1 h. The mixture was cooled to 5 C and stirred at the same temperature for 2 h. The white solid was filtered, washed with methanol/water (50:50, 10 mL) and air dried (1.2 g, 90%). M.p. 183-185 °C, lit.273 186-

1 188 °C; H NMR (300 MHz, CDCl3): 2.32 (s, 3H, CH3COO), 2.37 (s, 3H, CH3COO),

7.17 (d, J = 8.7 Hz, 2H, H3’, H5’), 7.18 (dd, J = 2.1, 8.6 Hz, 1H, H6), 7.32 (d, J = 2.1

Hz, 1H, H8), 7.59 (d, J = 8.7 Hz, 2H, H2’, H6’), 8.01 (s, 1H, H2), 8.33 (d, J = 8.6 Hz, 1H,

H5).

4’,7-Diacetoxyisoflavan-4-ol (76)274

To a solution of isoflavone 75 (1.5 g, 4.36 mmol) in OAc OH ethanol (60 mL) was added moist palladium charcoal

(10%, 400 mg Pd/C + 400 mg water). The mixture was AcO O hydrogenated at atmospheric pressure for 48 h. The catalyst was removed by filtration through Celite® and the filtrate was concentrated under vacuum when the title compound was obtained as a 2:1 mixture of cis:trans isomers (1.35 g, 90%). The cis/trans mixture was used in subsequent reactions without further purification.

1 trans isomer. H NMR (300 MHz, CDCl3): 2.28 (s, 3H, CH3COO), 2.29 (s, 3H,

CH3COO), 3.14 (ddd, J = 3.7, 7.9, 9.1 Hz, 1H, H3), 4.24 (dd, J = 9.1, 11.3 Hz, 1H, H2),

4.35 (dd, J = 3.7, 11.3 Hz, 1H, H2), 4.87 (d, J = 7.9 Hz, 1H, H4), 6.61 (d, J = 2.3 Hz,

1H, H8), 6.70 (dd, J = 2.3, 8.4 Hz, 1H, H6), 7.06 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.23 (d, J

= 8.6 Hz, 2H, H2’, H6’), 7.44 (dd, J = 8.4 Hz, 1H, H5).

1 cis isomer. H NMR (300 MHz, CDCl3): 2.28 (s, 3H, CH3COO), 2.29 (s, 3H,

CH3COO), 3.30 (dt, J = 3.4, 11.8 Hz, 1H, H3), 4.31 (ddd, J = 1.4, 11.8, 10.5 Hz, 1H,

H2), 4.56 (dd, J = 10.5, 11.8 Hz, 1H, H2), 4.75 (dd, J = 1.4, 3.4 Hz, 1H, H4), 6.66 (dd, J

= 2.3, 8.7 Hz, 1H, H6), 6.69 (d, J = 2.3 Hz, 1H, H8), 7.08 (d, J = 8.6 Hz, 2H, H3’, H5’),

7.26 (d, J = 8.7 Hz, 1H, H5), 7.29 (d, J = 8.6 Hz, 2H, H2’, H6’).

150 trans-4’,7-Diacetoxy-4-(3-acetyl-2-hydroxy-4-methoxyphenyl)isoflavan (78)

To a stirred solution of isoflavanol 76 (500 mg, 1.46 O OMe mmol) and 2’-hydroxy-6’-methoxyacetophenone 77 OAc HO (242 mg, 1.61 mmol) in dichloromethane (25 mL) was added BF3·OEt2 (10 drops). The mixture was stirred at AcO O r.t. for 2 h and then quenched by addition of water (25 mL). The mixture was stirred for

10 min and the organic layer was separated. The aqueous layer was extracted with dichloromethane (25 mL). The combined organic extracts were dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 25% ethyl acetate/hexane) gave the title compound 78 as a white solid (480 mg, 67%). M.p. 138-

-1 -1 -1 -1 140 C; UV (MeOH): max 206 ( 49509 cm M ), 275 ( 14429 cm M ), 344 ( 4233

-1 -1 cm M ) nm; IR (KBr): max 3452, 2930, 1760, 1613, 1496, 1463, 1428, 1368, 1317,

-1 1 1244, 1207, 1146, 1111, 1088, 1035, 1017, 911, 801 cm ; H NMR (300 MHz, CDCl3):

2.26 and 2.60 (2 × s, 6H, 2 × CH3COO), 2.68 (s, 3H, CH3CO), 3.42 (m, 1H, H3), 3.83

(s, 3H, CH3O), 4.23 (m, 2H, 2 × H2), 4.69 (d, J = 7.2 Hz, 1H, H4), 6.27 (d, J = 8.6 Hz,

1H, H5”), 6.54 (dd, J = 2.3, 8.3 Hz, 1H, H6), 6.66 (d, J = 2.3 Hz, 1H, H8), 6.75 (d, J =

8.3 Hz, 1H, H5), 6.96 (d, J = 8.7 Hz, 2H, H3’, H5’), 6.97 (d, J = 8.6 Hz, 1H, H6”), 7.30

13 (d, J = 8.7 Hz, 2H, H2’, H6’), 13.77 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 20.9 and 21.0 (2 × CH3COO), 33.6 (CH3CO), 39.9 (C3), 43.0 (C4), 55.4 (CH3O), 68.6 (C2),

100.7 (ArCH), 109.6 (ArCH), 110.7 (ArC), 114.0 (ArCH), 121.6 (ArCH), 122.0 (ArC),

128.7 (ArCH), 130.7 (ArCH), 136.4 (ArCH), 138.3 (ArC), 149.4 (ArC), 149.9 (ArC),

155.2 (ArC), 160.3 (ArC), 162.1 (ArC), 169.2 and 169.3 (2 × COO), 205.3 (C=O); MS

+ (TOF-ESI) m/z Calcd. for C28H26O8Na (M + Na) 513.15. Found 513.12; Anal. Calcd. for

C28H26O8: C, 68.56; H, 5.34. Found: C, 68.36; H, 5.64.

151 trans-4’,7-Dihydroxy-4-(3-acetyl-2-hydroxy-4-methoxyphenyl)isoflavan (79)

To a suspension of isoflavan 78 (80 mg, 0.163 mmol) in O OMe methanol (2 mL) was added KOH solution (1M, 20 OH drops). The mixture was stirred for 1 h and then acetic HO acid (1M, 20 drops) was added. The mixture was HO O concentrated under vacuum and diluted with water (2.5 mL). The solid was filtered, washed with water (2 mL) and dried. The product was triturated with methanol (1 mL), filtered and washed with a few drops of methanol. The title compound was obtained as a white solid (56 mg, 84%). M.p. 268-270 C; UV

-1 -1 -1 -1 -1 -1 (MeOH): max 206 ( 509189 cm M ), 224 ( 33378 cm M ), 277 ( 15630 cm M ),

-1 -1 346 ( 3520 cm M ) nm; IR (KBr): max 3363, 3236, 1618, 1593, 1568, 1514, 1420,

1371, 1322, 1244, 1228, 1215, 1167, 1109, 1121, 1091, 1033, 840, 814 cm-1; 1H NMR

(300 MHz, DMSO-d6 + acetone-d6): 2.61 (s, 3H, CH3CO), 3.33 (m, 1H, H3), 3.85 (s,

3H, CH3O), 4.12 (m, 2H, 2 × H2), 4.56 (d, J = 8.3 Hz, 1H, H4), 6.22 (dd, J = 2.3, 8.3 Hz,

1H, H6), 6.24 (d, J = 2.3 Hz, 1H, H8), 6.43 (d, J = 8.3 Hz, 1H, H5), 6.48 (d, J = 8.7 Hz,

1H, H5”), 6.63 (d, J = 8.3 Hz, 2H, H3’, H5’), 7.07 (d, J = 8.3 Hz, 2H, H2’, H6’), 7.11 (d, J

= 8.7 Hz, 1H, H6”), 9.03 and 9.06 (2 × s, 2H, 2 × OH), 13.66 (s, 1H, OH); 13C NMR

(75.6 MHz, DMSO-d6 + acetone-d6): 33.3 (CH3CO), 40.0 (C3), 42.8 (C4), 55.7

(CH3O), 69.4 (C2), 101.3 (ArCH), 102.6 (ArCH), 108.6 (ArCH), 110.5 (ArC), 115.3

(ArCH), 115.7 (ArC), 124.8 (ArCH), 130.3 (ArCH), 131.3 (ArC), 136.9 (ArCH), 155.4

(ArC), 156.4 (ArC), 157.1 (ArC), 160.2 (ArC), 161.9 (ArC), 206.2 (C=O); MS (ESI) m/z

+ Calcd. for C24H22O6Na (M + Na) 429.13. Found 429.10; Anal. Calcd. for C24H22O6: C,

70.92; H, 5.46. Found: C, 70.66; H, 5.64.

152 trans-4’,7-Diacetoxy-4-(3-acetyl-4-hydroxy-6-methoxyphenyl)isoflavan (81)

The title compound was synthesized following the OH O procedure for isoflavan 78 using isoflavanol 76 (500 mg, 1.46 mmol), 2’-hydroxy-4’-methoxyacetophenone OAc MeO

80 (242 mg, 1.61 mmol), BF3·OEt2 (10 drops) and dichloromethane (25 mL). After stirring for 2 h, more AcO O

BF3·OEt2 (10 drops) was added and stirring was continued further for 2 h. However, in this case the reaction did not go to completion. Chromatography (SiO2, 25% ethyl acetate/hexane) gave the title compound 81 as a white solid (200 mg, 28%). M.p. 168-

-1 -1 -1 -1 170 C; UV (MeOH): max 208 ( 66942 cm M ), 221 ( 55537 cm M ), 276 ( 21595

-1 -1 -1 -1 cm M ), 324 ( 9104 cm M ) nm; IR (KBr): max 3444 (br), 2924, 1758, 1496, 1634,

1588, 1496, 1371, 1270, 1207, 1144, 1108, 1035, 1016 cm-1; 1H NMR (300 MHz,

CDCl3): 2.25 (s, 3H, CH3COO), 2.27 (s, 3H, CH3COO), 2.35 (s, 3H, CH3CO), 3.30 (m,

1H, H3), 3.68 (s, 3H, CH3O), 4.29 (m, 2H, 2 × H2), 4.55 (d, J = 7.2 Hz, 1H, H4), 6.33 (s,

1H, H5”), 6.56 (dd, J = 2.3, 8.5 Hz, 1H, H6), 6.68 (d, J = 2.3 Hz, 1H, H8), 6.77 (d, J =

8.5 Hz, 1H, H5), 6.95 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.12 (s, 1H, H2”), 7.13 (d, J = 8.6

13 Hz, 2H, H2’, H6’), 12.60 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 20.97 and 21.01 (2

× CH3COO), 26.0 (CH3CO), 30.8 (C3), 44.4 (C4), 55.6 (CH3O), 68.9 (C2), 99.4 (ArCH),

109.8 (ArCH), 113.4 (ArC), 114.1 (ArCH), 121.4 (ArCH), 128.6 (ArCH), 130.4 (ArCH),

132.0 (ArCH), 137.9 (ArC), 149.5 (ArC), 149.9 (ArC), 155.3 (ArC), 163.7 (ArC), 164.0

(ArC), 169.2 and 169.3 (2 × COO), 202.5 (C=O); MS (TOF-ESI) m/z Calcd. for

+ C28H26O8Na (M + Na) 513.15. Found 513.14; Anal. Calcd. for C28H26O8: C, 68.56; H,

5.34. Found: C, 68.85; H, 5.50.

153 trans-4’,7-Dihydroxy-4-(3-acetyl-4-hydroxy-6-methoxyphenyl)isoflavan (82)

The title compound was synthesized following the OH O procedure for compound 79 using isoflavan 81 (80 mg, OH MeO 0.163 mmol). The trihydroxy compound 82 was obtained as a white solid (63 mg, 95%). M.p. 192-194 HO O -1 -1 -1 -1 C; UV (MeOH): max 206 ( 55831 cm M ), 226 ( 35729 cm M ) sh, 276 ( 19738

-1 -1 -1 -1 cm M ), 325 ( 7633 cm M ) nm; IR (KBr): max 3395 (br), 2954, 2925, 1633, 1600,

1515, 1445, 1372, 1332, 1261, 1204, 1157, 1113, 1063, 1033, 831 cm-1; 1H NMR (300

MHz, acetone-d6): 2.39 (s, 3H, CH3CO), 3.32 (m, 1H, H3), 3.80 (s, 3H, CH3O), 4.19

(m, 2H, 2 × H2), 4.53 (d, J = 8.2 Hz, 1H, H4), 6.29 (dd, J = 2.3, 8.3 Hz, 1H, H6), 6.33

(d, J = 2.3 Hz, 1H, H8), 6.40 (s, 1H, H5”), 6.53 (d, J = 8.3 Hz, 1H, H5), 6.69 (d, J = 6.8

Hz, 2H, H3’, H5’), 7.08 (d, J = 6.8 Hz, 2H, H2’, H6’), 7.41 (s, 1H, H2’’), 8.18 (br, 2H, 2 ×

13 OH), 12.65 (s, 1H, OH); C NMR (75.6 MHz, acetone-d6): 29.1 (CH3CO), 25.3 (C3),

43.6 (C4), 55.4 (CH3O), 69.3 (C2), 99.0 (ArCH), 102.5 (ArCH), 108.2 (ArCH), 113.1

(ArC), 114.9 (ArCH), 116.0 (ArC), 128.7 (ArCH), 131.7 (ArC), 130.2 (ArCH), 132.4

(ArCH), 155.6 (ArC), 156.0 (ArC), 156.7 (ArC), 163.7 (ArC), 164.2 (ArC), 202.9 (C=O);

+ MS (TOF-ESI) m/z Calcd. for C24H22O6 (M + 2) 408.14. Found 408.35; Anal. Calcd. for

C24H22O6: C, 70.92; H, 5.46. Found: C, 70.52; H, 5.50.

trans-4’,7-Diacetoxy-4-(4-hydroxyphenyl)isoflavan (83).

The title compound was synthesized following the OH procedure for compound 78 using isoflavanol 76 (500 OAc mg, 1.46 mmol) and phenol (151 mg, 1.61 mmol).

Chromatography (SiO2, 35% ethyl acetate/hexane) AcO O gave diacetoxyisoflavan 83 as a white solid (170 mg,

-1 -1 -1 -1 28%). M.p. 188-190 °C; UV (MeOH): max 206 ( 39997 cm M ), 225 ( 20613 cm M )

-1 -1 sh, 276 ( 4348 cm M ) nm; IR (KBr): max 3412, 1757, 1737, 1615, 1594, 1511, 1493,

154 -1 1 1426, 1419, 1370, 1214, 1145, 1109, 1033, 1018 cm ; H NMR (300 MHz, CDCl3):

2.25 (s, 3H, CH3COO), 2.27 (s, 3H, CH3COO), 3.23 (ddd, J = 3.7, 9.8, 10.2 Hz, 1H,

H3), 4.15 (dd, J = 10.2, 10.9 Hz, 1H, H2), 4.21 (d, J = 9.8 Hz, 1H, H4), 4.33 (dd, J =

3.7, 10.9 Hz, 1H, H2), 4.72 (brs, 1H, OH), 6.53 (dd, J = 2.6, 8.5 Hz, 1H, H6), 6.64 (d, J

= 8.3 Hz, 2H, H3’, H5’), 6.65 (d, J = 2.6 Hz, 1H, H8), 6.76 (d, J = 8.5 Hz, 1H, H5), 6.83

(d, J = 8.3 Hz, 2H, H2’, H6’), 6.95 (d, J = 8.3 Hz, 2H, H3’’, H5’’), 7.03 (d, J = 8.3 Hz, 2H,

13 H2’’, H6’’); C NMR (75.6 MHz, CDCl3): 20.09 and 21.01 (2 × CH3COO), 46.8 (C3),

47.9 (C4), 69.6 (C2), 109.7 (ArCH), 113.9 (ArCH), 115.2 (ArCH), 121.3 (ArC), 121.5

(ArCH), 123.4 (ArC), 128.7 (ArCH), 130.0 (ArCH), 131.1 (ArCH), 135.0 (ArC), 137.5

(ArC), 149.4 (ArC), 149.8 (ArC), 154.4 (ArC), 155.2 (ArC), 169.5 and 169.5 (2 × COO);

+ MS (TOF-ESI) m/z Calcd. for C25H22O6Na (M + Na) 441.13. Found 441.13; Anal.

Calcd. for C25H22O6: C, 71.75; H, 5.29. Found: C, 71.83; H, 5.32.

trans-4’,7-Dihydroxy-4-(4-hydroxyphenyl)isoflavan (84)

The title compound was synthesized following the OH procedure for compound 79 using isoflavan 83 (75 mg, OH 0.179 mmol). Trihydroxyisoflavan 84 was obtained as an off-white solid (56 mg, 95%). M.p.130 °C; UV

-1 -1 - HO O (MeOH): max 207 ( 40847 cm M ), 225 ( 26054 cm

1 -1 -1 -1 M ) sh, 278 ( 6389 cm M ) nm; IR (KBr): max 3418, 2923, 1614, 1593, 1567, 1514,

-1 1 1467, 1444, 1384, 1255, 1234, 1166, 1106 cm ; H NMR (300 MHz, acetone-d6):

3.13 (ddd, J = 4.5, 9.4, 10.5 Hz, 1H, H3), 4.17 (m, 3H, H4, 2 × H2), 6.28 (dd, J = 2.3,

8.3 Hz, 1H, H6), 6.32 (d, J = 2.3 Hz, 1H, H8), 6.48 (d, J = 8.3 Hz, 1H, H5), 6.65 and

6.68 (2 × d, J = 8.3 Hz, 4H, H3’, H5’, H3’’, H5’’), 6.83 and 6.98 (2 × d, J = 8.3 Hz, 4H,

13 H2’, H6’, H2’’, H6’’); C NMR (75.6 MHz, acetone-d6): 46.5 (C3), 47.3 (C4), 70.0

(C2), 102.4 (ArCH), 108.1 (ArCH), 114.8 (ArCH), 115.0 (ArCH), 117.6 (ArC), 128.9

(ArCH), 129.8 (ArCH), 130.9 (ArCH), 131.2 (ArC), 134.8 (ArC), 155.5 (ArC), 155.7

+ (ArC), 156.1 (ArC), 156.7 (ArC); MS (TOF-ESI) m/z Calcd. for C21H18O4·(M+1) 335.12.

155 1 Found, 335.10; Anal. Calcd. for C21H18O4· /2H2O: C, 73.46; H, 5.58. Found: C, 73.28; H,

5.77.

trans-4’,7-Diacetoxy-4-(2-hydroxy-4,6-dimethoxyphenyl)isoflavan (86)

The title compound was synthesized following the OMe procedure for isoflavan 78 using isoflavanol 76 (500 mg, 1.46 mmol) and 3,5-dimethoxyphenol 85 (248 MeO OH OAc mg, 1.61 mmol). Chromatography (SiO2, 25% ethyl AcO O acetate/hexane) gave the title compound as a 1:3 mixture of atropisomers (325 mg, 46%). M.p. 136 °C; UV (MeOH): max 211 ( 50995

-1 -1 -1 -1 cm M ), 275 ( 4321 cm M ) nm; IR (KBr): max 3444, 1755, 1731, 1614, 1588, 1511,

-1 1 1495, 1460, 1424, 1370, 1215, 1144 cm ; H NMR (300 MHz, CDCl3): 2.25 (s, 3H,

CH3COO) and 2.26 (s, 3H, CH3COO), 3.40 (s, 3H, CH3O), 3.55 (ddd, J = 2.6, 10.9,

11.3 Hz, 1H, H3), 3.70 (s, 3H, CH3O), 4.27 (dd, J = 10.9, 11.3 Hz, 1H, H2), 4.39 (dd, J

= 2.6, 10.9 Hz, 1H, H2), 4.89 (d, J = 10.9 Hz, 1H, H4), 5.90 and 5.95 (each bs, 2H, H3”,

H5”), 6.57 (dd, J = 2.6, 8.3 Hz, 1H, H6), 6.69 (d, J = 2.6 Hz, 1H, H8), 6.91 (d, J = 8.3

Hz, 1H, H5), 6.91 (d, J = 8.3 Hz, 2H, H3’, H5’), 7.07 (d(br), J = 8.3 Hz, 2H, H2’, H6’);

13 C NMR* (75.6 MHz, CDCl3): 21.0 (2 × CH3COO), 37.5 (C3), 42.1 (C4), 55.0 (CH3O),

55.5 (CH3O), 71.0 (C2), 91.3 (ArCH), 95.1 (ArCH), 108.6 (ArC), 110.1 (ArCH), 114.3

(ArCH), 121.0 (ArCH), 122.4 (ArC), 128.8 (ArCH), 129.0 (ArC), 137.5 (ArC), 149.4

(149.9) (ArC), (155.2) 155.3 (ArC), (159.6) 159.9 (ArC), 169.4 (2 × COO); HRMS (ESI)

+ m/z Calcd. for C27H26O8Na (M + Na) 501.1525. Found 501.1437; Anal. Calcd. for

C27H26O8: C, 67.77; H, 5.47. Found: C, 67.51; H, 5.68.

*Additional peaks are due to atropisomers.

156 trans-4’,7-Dihydroxy-4-(2-hydroxy-4,6-dimethoxyphenyl)isoflavan (87)

To a stirred solution of diacetoxyisoflavan 86 (170 mg, OMe

0.35 mmol) in methanol (2 mL) was added 1M KOH MeO OH (20 drops). The solution was stirred for 30 min and OH then neutralized by addition of acetic acid (1M, 20 HO O drops). The reaction mixture was diluted with water (5 mL) and the product was extracted with ether (5 mL × 3). The combined ethereal extracts were dried over anhydrous sodium sulfate and concentrated under vacuum. Trihydroxyisoflavan 87 was obtained as a pale yellow solid (90 mg, 64%). M.p. 118-120 C; UV (MeOH): max 209 (

-1 -1 -1 -1 -1 -1 58136 cm M ), 225 ( 31428 cm M ) sh, 280 ( 5431 cm M ) nm; IR (KBr): max

3388, 2960, 2938, 1615, 1596, 1514, 1465, 1452, 1338, 1253, 1201, 1151, 1115, 1092,

-1 1 1052, 1029, 942, 830, 543 cm ; H NMR (300 MHz, acetone-d6): 3.51 (br, 1H, 4”

OH), 3.63 (s, 6H, 2 × CH3O), 3.90 (m, 1H, H3), 4.04 (dd, J = 10. 6, 10.9 Hz, 1H, H2),

4.17 (dd, J = 3.8, 10.6 Hz, 1H, H2), 4.82 (d, J = 11.3 Hz, 1H, H4), 5.98 (s, 2H, H3”,

H5”), 6.19 (dd, J = 2.6, 8.3 Hz, 1H, H6), 6.26 (d, J = 2.6 Hz, 1H, H8), 6.47 (d, J = 8.3

Hz, 1H, H5), 6.65 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.04 (d, J = 8.6 Hz, 2H, H2’, H6’), 7.90

+ (br, 2H, 2 × OH); HRMS (ESI) m/z Calcd. for C23H22O6Na (M + Na) 417.1314. Found

417.1238.

trans-4’,7-Diacetoxy-4-(2-hydroxy-4,5,6-trimethoxyphenyl)isoflavan (89)

The title compound was synthesized following the OMe OMe procedure for compound 78 using isoflavanol 76 (500 OMe mg, 1.46 mmol) and 3,4,5-trimethoxyphenol 88 (297 HO OAc mg, 1.61 mmol). Chromatography (SiO2, 5% AcO O MeOH/toluene) gave the title compound 89 as a

1:1.2 mixture of atropisomers (607 mg, 81%). M.p.116-118 °C (from MeOH); UV

-1 -1 -1 -1 (MeOH): max 207 ( 62745 cm M ), 284 ( 6294 cm M ) nm; IR (KBr): max 3444,

157 1756, 1604, 1494, 1459, 1416, 1369, 1212, 1192, 1143, 1130, 1109, 1033, 993, 906

-1 1 cm ; H NMR* (300 MHz, CDCl3): 2.23, 2.25 and 2.26 (3 × s, 6H, 2 × CH3COO),

3.19, 3.40, 3.47, 3.63, 3.69 and 3.73 (6 × s, 9H, 3 × CH3O), 3.80 (m, 1H, H3), 4.10-4.45

(m, 2H, 2 × H2), 4.73 (d, J = 11.3 Hz, 1H, H4), 5.95 and 6.11 (2 × s, 1H, H3’’), 6.52 (m,

1H, H6), 6.66 (m, 1H, H8), 6.80 and 6.85 (2 × d, J = 8.3 Hz, 1H, H5), 6.91 (d, J = 8.3

Hz, 2H, H3’, H5’), 7.07 and 7.14 (2 × d, J = 8.3 Hz, 2H, H2’, H6’); 13C NMR* (75.6 MHz,

CDCl3): 21.0 (2 × CH3COO), 39.2 (38.5) and 41.4 (42.8) (C3 and C4), 50.7, 55.6,

59.4 and 60.7 (60.9) (3 × CH3O), 70.86 (71.0) (C2), 95.3 (ArCH), 97.4 (ArCH), 110.1

(109.5) (ArCH), 113.4 (113.5) (ArCH), 114.4 (114.9), 121.4 (121.2) (ArCH), 122.7

(ArC), 125.5 (ArC), 128.7 (ArC), 128.8 (128.9) (ArCH), 135.6 (136.7) (ArC), 137.7

(138.3) (ArC), 149.5 (ArC), 149.9 (149.8) (ArC), 152.5 (ArC), 152.9 (152.7) (ArC), 155.2

+ (155.0) (ArC), 169.5 (169.4) (2 × COO); MS (ESI) m/z Calcd. for C28H28O9Na (M + Na)

531.16. Found 531.14; Anal. Calcd. for C28H28O9: C, 66.13; H, 5.55. Found: C, 65.84;

H, 5.60.

*Additional peaks are due to atropisomers.

trans-4’,7-Dihydroxy-4-(2-hydroxy-4,5,6-trimethoxyphenyl)isoflavan (90)

The title compound was synthesized following the OMe procedure for compound 79 using isoflavan 89 (100 OMe mg, 0.196 mmol), methanol (2 mL), KOH solution (1M, HO OMe 20 drops) and acetic acid (1M, 20 drops). Preparative OH thin layer chromatography (SiO2, 55% ethyl HO O acetate/hexane) gave dihyroxyisoflavan 90 as a white solid (57 mg, 68%). M.p. 116-

-1 -1 -1 -1 118 °C; UV (MeOH): max 207 ( 62745 cm M ), 284 ( 6294 cm M ) nm; IR (KBr):

max 3444, 1756, 1604, 1494, 1459, 1416, 1369, 1212, 1192, 1143, 1130, 1109, 1033,

-1 1 993, 906 cm ; H NMR* (300 MHz, acetone-d6): 3.16, 3.20, 3.46, 3.61 and 3.66 (6 × s, 9H, 3 × CH3O), 3.80-4.20 (m, 3H, H3, 2 × H2), 4.63 and 4.80 (2 × d, J = 10.9 Hz, 1H,

H4), 6.17 (s, 1H, H3’’), 6.27 (m, 2H, H6, H8), 6.50 (m, 1H, H5), 6.67 (d, J = 7.9 Hz, 2H,

158 H3’, H5’), 7.02 and 7.07 (2 × d, J = 7.9 Hz, 2H, H2’, H6’), 7.70, 7.99, 8.02, 8.04 and

13 8.09 (br, 3H, 3 × OH); C NMR* (75.6 MHz, acetone-d6): 37.4 (39.1) and 42.2 (40.32)

(C3 and C4), 58.8, 59.6 and 60.3 (3 × CH3O), 71.2 (71.7) (C2), 94.9 (ArCH), 96.6

(ArCH), 102.4 (ArCH), 107.6 (107.5) (ArCH), 115.2 (114.0) (ArC), 114.8 (ArCH), 119.1

(118.3) (ArC), 128.8 (ArCH), 129.2 (128.7) (ArC), 132.3 (131.9) (ArC), 136.2 (135.0)

(ArC), 151.5 (151.3) (ArC), 152.2 (ArC), 153.5 (153.1) (ArC), 155.3 (ArC), 155.8 (ArC),

+ 156.0 (ArC); MS (ESI) m/z Calcd. for C24H24O7 (M) 424.15. Found 424.05; Anal. Calcd.

1 for C24H24O7· /2CH3OH: C, 66.81; H, 5.95. Found: C, 66.74; H, 5.70.

*Additional peaks are due to atropisomers.

trans-4’,7-Diacetoxy-4-(2-hydroxynaphth-1-yl)isoflavan (92)

The title compound was synthesized following the procedure for isoflavan 78 using isoflavanol 76 (500 OH mg, 1.46 mmol), 2-naphthol 91 (232 mg, 1.61 mmol) OAc and BF3·OEt2 (20 drops). Chromatography (SiO2, AcO O

35% ethyl acetate/hexane) gave the title compound as a (1:1.15) mixture of

-1 -1 atropisomers (450 mg, 65%). M.p. 201-203 °C; UV (MeOH): max 212 ( 40250 cm M ) sh, 227 ( 46755 cm-1M-1), 280 ( 9451 cm-1M-1), 337 ( 3714 cm-1M-1) nm; IR (KBr):

max 3450, 1751, 1621, 1588, 1493, 1425, 1368, 1216, 1114, 1168, 1033, 1016, 910,

-1 1 815 cm ; H NMR* (300 MHz, CDCl3): 2.17, 2.22, 2.26, and 2.27 (4 × s, 6H, 2 ×

CH3COO), 3.98 (m, 1H, H3), 4.42 (m, 2H, 2 × H2), 5.12 and 5.43 (2 × d, J = 11.0 Hz,

+ H4), 6.40-7.70 (m, 13H, ArH); HRMS (ESI) m/z Calcd. for C29H24O6Na (M + Na) ,

491.1471. Found 491.1404; Anal. Calcd. for C29H24O6: C, 74.34; H, 5.16. Found: C,

74.27; H, 5.21.

*Additional peaks are due to atropisomers.

159 trans-4’,7-Dihydroxy-4-(2-hydroxynaphth-1-yl)isoflavan (93)

The title compound was synthesized following the procedure for compound 79 using diacetoxyisoflavan OH

92 (150 mg, 0.32 mmol), methanol (3 mL), KOH OH solution (1M, 30 drops) and acetic acid (1M, 30 drops). HO O

The title compound was obtained as an off-white solid (99 mg, 80%). M.p. 138-140 °C;

-1 -1 -1 -1 -1 -1 UV (MeOH): max 207 ( 60965 cm M ), 229 ( 75412 cm M ), 280 ( 11174 cm M ),

-1 -1 337 ( 4412 cm M ) nm; IR (KBr): max 3394 (br), 1620, 1598, 1514, 1467, 1447, 1255,

-1 1 1162, 1117, 1029, 811 cm ; H NMR (300 MHz, CDCl3): 3.90 (m, 1H, H3), 4.30 (m,

2H, 2 × H2), 5.20 and 5.55 (2 × d, J = 11.7 Hz, 1H, H4), 6.10-7.70 (m, 13H, ArH), 8.30

+ (br, 3H, 3 × OH); HRMS (ESI) m/z Calcd. for C25H20O4Na (M + Na) , 407.1259. Found

1 407.1186; Anal. Calcd. for C25H20O4· /2H2O: C, 76.32; H, 5.38. Found: C, 76.27; H,

5.25.

trans-4’,7-Diacetoxy-4-(4-methoxyphenyl)isoflavan (94)

A mixture of isoflavan 83 (250 mg, 0.6 mmol), K2CO3 OMe (100 mg, 0.71 mmol), dimethyl sulfate (70 L, 0.71 OAc mmol) and acetone (5 mL) was refluxed for 4 h. The solution was concentrated under vacuum and then AcO O diluted with water (25 mL). The product 94 was filtered, washed with water and air dried. The title compound was obtained as a white

-1 -1 solid (168 mg, 65%). M.p. 118 °C; UV (MeOH): max 208 ( 33589 cm M ), 220 (

-1 -1 -1 -1 27778 cm M ), 275 ( 3699 cm M ) nm; IR (KBr): max 1758, 1611, 1510, 1369, 1207,

-1 1 1146, 1035, 1016, 909 cm ; H NMR (300 MHz, CDCl3): 2.26 and 2.27 (2 × s, 6H, 2 ×

CH3COO), 3.26 (dt, J = 3.8, 9.8 Hz, 1H, H3), 3.74 (s, 3H, CH3O), 4.16 (dd, J = 9.8, 10.9

Hz, 1H, H2), 4.22 (d, J = 9.8 Hz, 1H, H4), 4.34 (dd, J = 3.8, 10.9 Hz, 1H, H2), 6.54 (dd,

J = 2.3, 8.3 Hz, 1H, H6), 6.66 (d, J = 2.3 Hz, 1H, H8), 6.72 (d, J = 8.7 Hz, 2H, H3’, H6’),

6.77 (d, J = 8.3 Hz, 1H, H6), 6.89 (d, J = 8.3 Hz, 2H, H2’, H6’), 6.95 (d, J = 8.3 Hz, 2H, 160 13 H3”, H5’’), 7.05 (d, J = 8.3 Hz, 2H, H2”, H6’’); C NMR (75.6 MHz, CDCl3): 21.0 (2 ×

CH3COO), 46.8 (C3), 47.8 (C4), 55.0 (CH3O), 69.7 (C2), 109.7 (ArCH), 113.7 (ArCH),

113.9 (ArCH), 121.4 (ArCH), 123.3 (ArC), 128.6 (ArCH), 129.8 (ArCH), 131.0 (ArCH),

135.0 (ArC), 137.5 (ArC), 149.5 (ArC), 149.8 (ArC), 155.2 (ArC), 158.2 (ArC), 169.2 (2

+ × COO); MS (TOF-ESI) m/z Calcd. for C26H24O6Na (M + Na) 455.14. Found 455.14;

Anal. Calcd. for C26H24O6: C, 72.21; H, 5.59. Found: C, 72.57; H, 5.77.

trans-4’,7-Dihydroxy-4-(4-methoxyphenyl)isoflavan (96)

The title compound was synthesized following the OMe procedure for isoflavan 79 using diacetoxyisoflavan 94 OH (100 mg, 0.23 mmol), methanol (2 mL), KOH solution

(1M, 20 drops) and acetic acid (1M, 20 drops). The title HO O compound 96 was obtained as an off-white solid (64 mg, 80%). M.p. 146 °C; UV

-1 -1 -1 -1 -1 -1 (MeOH): max 205 ( 35881 cm M ), 225 ( 20313 cm M ), 278 ( 4142 cm M ) nm;

-1 1 IR (KBr): max 3424, 1612, 1512, 1444, 1246, 1157, 1111, 1033 cm ; H NMR (300

MHz, CDCl3): 3.15 (ddd, J = 3.8, 9.8, 10.9 Hz, 1H, H3), 3.74 (s, 3H, CH3O), 4.09 (d, J

= 10.9 Hz, 1H, H4), 4.17 (dd, J = 9.8, 10.9 Hz, 1H, H2), 4.28 (dd, J = 3.8, 10.9 Hz, 1H,

H2), 5.01 (bs, 2H, 2 × OH), 6.30 (dd, J = 2.6, 8.3 Hz, 1H, H6), 6.39 (d, J = 2.6 Hz, 1H,

H8), 6.62 (d, J = 8.3 Hz, 1H, H5), 6.68 (d, J = 8.7 Hz, 2H, H3’, H5’), 6.72 (d, J = 8.6 Hz,

2H, H3”, H5’’), 6.88 (d, J = 8.7 Hz, 2H, H2’, H6’), 6.90 (d, J = 8.6 Hz, 2H, H2”, H6’’); 13C

NMR (75.6 MHz, CDCl3): 46.7 (C3), 47.7 (C4), 55.1 (CH3O), 69.9 (C2), 102.8 (ArCH),

108.4 (ArCH), 113.5 (ArCH), 115.3 (ArCH), 118.3 (ArC), 128.9 (ArCH), 129.7 (ArCH),

131.4 (ArCH), 132.4 (ArC), 135.9 (ArC), 154.3 (ArC), 155.0 (ArC), 155.5 (ArC), 157.9

+ (ArC); MS (TOF-ESI) m/z Calcd. for C22H20O4 (M + 1) 349.39. Found 349.18. Anal.

1 Calcd. for C22H20O4· /3H2O: C, 74.56; H, 5.88. Found: C, 74.87; H, 5.97.

161 2-(3’,5’-Dimethoxyphenoxy)-4’-bromoacetophenone (102)

A mixture of 3,5-dimethoxyphenol 85 (2.0 g, 13.0 Br mmol), 4-bromophenacylbromide 101 (3.6 g, 13.0 OMe O mmol), potassium bicarbonate (1.3 g, 13.0 mmol) and MeO O acetone (40 mL) was refluxed for 24 h. Acetone was removed under vacuum. Water (25 mL) was added to the residue and the product was extracted with dichloromethane (25 mL × 2). The combined extracts were dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2,

10% ethyl acetate/hexane) gave pure acetophenone 102 (3.0 g, 66%). M.p. 105-107 °C

112 1 (from ethyl acetate/hexane), lit. 106-108 °C; H NMR (300 MHz, CDCl3): 3.75 (s,

6H, 2 × CH3O), 5.14 (s, 2H, CH2), 6.11 (s, 3H, H2’’, H4’’, H6’’), 7.63 and 7.85 (2 × d, J =

7.6 Hz, 4H, H2’, H4’, H5’, H6’).

3-(4’-Bromophenyl)-4,6-dimethoxybenzofuran (103)

A mixture of acetophenone 102 (1.5 g, 4.27 mmol) and trifluoro Br acetic acid (6 mL) was stirred at ambient temperature for 1 h.

The reaction mixture was poured onto crushed ice (50.0 g) and OMe the precipitated product was filtered, washed with water and air MeO O dried (0.88 g, 62%). M.p. 117 °C (from ethyl acetate/hexane),

112 1 lit. 117-118 °C; H NMR (300 MHz, CDCl3): 3.81 (s, 3H, CH3O), 3.87 (s, 3H,

CH3O), 6.36 (d, J = 2.0 Hz, 1H, H5), 6.68 (d, J = 2.0 Hz, 1H, H7), 7.17 (s, 1H, H2),

7.47-7.54 (m, 4H, H2’, H3’, H5’, H6’).

4,6-Dimethoxy-2,3-diphenylindole (106)

A mixture of 3,5-dimethoxyaniline 104 (2.0 g, 13 mmol) and OMe benzoin 105 (2.77 g, 13 mmol) was heated at 125 °C for 1.5 h. The mixture was cooled to r.t., aniline (0.4 mL, 4.3 mmol) MeO N H

162 and acetic acid (8 mL, 140 mmol) were added and the heating was continued further at

125 °C for 4 h. The mixture was cooled to r.t. and filtered. The product was washed with methanol and dried (2.7 g, 63%). M.p. 240-242 °C (from chloroform/hexane), lit.275

1 240-241 °C; H NMR (300 MHz, CDCl3): 3.65 (s, 3H, CH3O), 3.85 (s, 3H, CH3O), 6.20

(d, J = 2.0 Hz, 1H, H5), 6.65 (d, J = 2.0 Hz, 1H, H7), 7.25-7.40 (m, 10H, Ar).

1-(4-Bromophenyl)-2-[(3,5-dimethoxyphenyl)amino]ethanone (107)

A mixture of 3,5-dimethoxyaniline 104 (4.1 g, 26.76 mmol), 4-bromophenacylbromide

101 (7.5 g, 27.0 mmol), sodium bicarbonate (2.6 g, OMe O 31.0 mmol) and absolute ethanol (75 mL) was refluxed Br MeO N for 1.5 h. The reaction mixture was cooled to r.t. and H stirred for 1 h. The product was filtered, washed with chilled methanol (20 mL) and

275 1 dried (8.9 g, 95%). M.p. 133-135 °C, lit. 134-135 °C; H NMR (300 MHz, CDCl3):

3.78 (s, 6H, CH3O), 4.52 (s, 2H, CH2), 5.90-5.95 (m, 3H, H2’, H4’, H6’), 7.60-7.95 (m,

4H, H2, H3, H5, H6).

N-[2-(4-Bromophenyl)-2-oxo-ethyl]-N-(3,5-dimethoxyphenyl)acetamide(108)114

A mixture of acetophenone 107 (10.0 g, 28.55 mmol) OMe Br and acetic anhydride (20 mL, 211.5 mmol) was heated O at 50 °C for 1 h. Water (100 mL) was added and the MeO N mixture was stirred overnight at r.t. The precipitated O product was filtered, washed with water and dried (10.0 g, 89%). M.p. 113-114 °C; 1H

NMR (300 MHz, CDCl3): 2.00 (s, 3H, CH3CO), 3.76 (s, 6H, CH3O), 4.98 (s, 2H, CH2),

6.40 (t, J = 2.3 Hz, 1H, H4’), 6.50 (d, J = 2.3 Hz, 2H, H2’, H6’), 7.56 (d, J = 8.7 Hz, 2H,

H2, H6), 7.78 (d, J = 8.7 Hz, 2H, H3, H5).

163 1-Acetyl-3-(4’-bromophenyl)-4,6-dimethoxyindole (109)

A mixture of ketone 108 (10.0 g, 25.5 mmol) and trifluoroacetic Br acid (25 mL) was refluxed under an argon atmosphere for 2 h. OMe The reaction mixture was cooled to r.t. and poured into ice-cold water (200 mL). The precipitated product was filtered, washed MeO N with cold water and air dried (9.0 g, 94%). M.p. 156-158 °C, O

114 ° 1 lit. 156-158 C; H NMR (300 MHz, CDCl3): 2.62 (s, 3H, CH3CO), 3.74 (s, 3H,

CH3O), 3.89 (s, 3H, CH3O), 6.40 (d, J = 1.8 Hz, 1H, H5), 7.14 (s, 1H, H2), 7.41 (d, J =

8.7 Hz, 2H, H2’, H6’), 7.49 (d, J = 8.7 Hz, 2H, H3’, H5 ), 7.76 (d, J = 1.8 Hz, 1H, H7).

3-(4’-Bromophenyl)-4,6-dimethoxyindole (110)

To a suspension of acetylindole 109 (4.5 g, 12 mmol) in Br methanol (70 mL) was added KOH (2.5 g, 44.6 mmol). The OMe mixture was stirred at ambient temperature for 1 h and then poured into ice-water (200 mL). The precipita ted product was MeO N H filtered, washed with water and dried (3.0 g, 75%). M.p. 175-178 °C, lit.275 180-181 °C;

1 H NMR (300 MHz, CDCl3): 3.79 (s, 3H, CH3O), 3.84 (s, 3H, CH3O), 6.25 (d, J = 1.9

Hz, 1H, H5), 6.48 (d, J = 1.9 Hz, 1H, H7), 7.00 (d, J = 2.6 Hz, 1H, H2), 7.46 (s, 4H, H2’,

H3’, H5’, H6’), 8.13 (br, 1H, NH).

4’,7-Dimethoxyisoflav-3-ene (112) OMe To a mixture of phenoxodiol 111 (480 mg, 2.0 mmol), K2CO3 (414 mg, 3 mmol) and acetone (10 MeO O mL) was added methyl iodide (2 mL). The mixture was refluxed for 4 h, concentrated under vacuum and the residue was diluted with water (25 mL). The resulting solid was filtered, washed with water and dried. The title compound was obtained as a white solid (500 mg, 93%). M.p. 155-158 C, lit.276 159-

-1 -1 -1 -1 161 °C; UV (MeOH): max 211 ( 31027 cm M ), 249 ( 19926 cm M ), 333 ( 32348 164 -1 -1 1 cm M ) nm; H NMR (300 MHz, CDCl3): 3.78 (s, 3H, CH3O), 3.80 (s, 3H, CH3O),

5.10 (s, 2H, 2 × H2), 6.44 (d, J = 2.3 Hz, 1H, H8), 6.47 (dd, J = 2.3, 7.9 Hz, 1H, H6),

6.67 (s, 1H, H4), 6.91 (d, J = 9.1 Hz, 2H, H3’, H5’), 6.98 (d, J = 7.9 Hz, 1H, H5), 7.35

13 (d, J = 9.1 Hz, 2H, H2’, H6’); C NMR (75.6 MHz, CDCl3): 55.2 (CH3O), 55.3 (CH3O),

67.2 (C2), 101.3 (ArCH), 107.2 (ArCH), 114.0 (ArCH), 116.3 (ArC), 118.0 (ArCH), 125.8

(ArCH), 127.3 (ArCH), 128.3 (ArC), 129.5 (ArC), 154.2 (ArC), 159.2 (ArC), 160.3 (ArC).

trans-4’,7-Diacetoxy-4-(3-(4’-bromophenyl)-4,6-dimethoxybenzofuran-2-yl) isoflavan (113)

The title compound was synthesized following the MeO OMe procedure for diacetoxyisoflavan 78 using Br O isoflavanol 76 (500 mg, 1.46 mmol), benzofuran 103 OAc (445 mg, 1.46 mmol) and BF3·OEt2 (10 drops). AcO O Chromatography (SiO2, 15% ethyl acetate/hexane) gave the title compound as an off-white solid (430 mg, 43%). M.p. 204-206 C (from

-1 -1 -1 -1 MeOH); UV (MeOH): max 206 ( 86888 cm M ), 259 ( 25350 cm M ) nm; IR (KBr):

max 2929, 2832, 1763, 1618, 1601, 1501, 1460, 1424, 1368, 1205, 1147, 1109, 1070,

-1 1 1036, 1009, 819 cm ; H NMR (300 MHz, CDCl3): 2.27 (2 × s, 6H, 2 × CH3COO),

3.62 (s, 3H, CH3O), 3.62 (ddd, J = 3.8, 10.9, 11.3 Hz, 1H, H3), 3.81 (s, 3H, CH3O), 4.15

(dd, J = 10.9, 11.3 Hz, 1H, H2), 4.29 (d, J = 10.9 Hz, 1H, H4), 4.40 (dd, J = 3.8, 10.9

Hz, 1H, H2), 6.24 (d, J = 1.9 Hz, 1H, H5”), 6.55-6.58 (m, 2H, H7” and H6), 6.68 (d, J =

2.3 Hz, 1H, H8), 6.80-6.88 (m, 7H, H5, H3’, H5’, H2’’’, H3’’’, H5’’’, H6’’’), 7.39 (d, J = 8.3

13 Hz, 2H, H2’, H6’); C NMR (75.6 MHz, CDCl3): 20.97 and 20.99 (2 × CH3COO), 40.9

(C3), 42.4 (C4), 55.2 (CH3O), 55.6 (CH3O), 70.0 (C2), 88.2 (ArCH), 94.5 (ArCH), 110.2

(ArCH), 110.6 (ArC), 114.2 (ArCH), 119.3 (ArC), 120.0 (ArC), 121.1 (ArCH), 121.7

(ArC), 121.7 (ArC), 128.4 (ArCH), 129.5 (ArCH), 130.7 (ArCH), 131.6 (ArCH), 131.7

(ArC), 136.4 (ArC), 149.6 (ArC), 149.8 (ArC), 149.8 (ArC), 154.2 (ArC), 155.9 (ArC),

156.0 (ArC), 159.0 (ArC), 169.2 and 169.3 (2 × COO); MS (TOF-ESI) m/z Calcd. for 165 + 79 81 79 C35H29BrO8Na (M + Na) 679.09 (Br ) and 681.09 (Br ). Found 679.09 (Br ) and

81 681.09 (Br ); Anal. Calcd. for C35H29BrO8: C, 63.93; H, 4.45. Found: C, 63.98; H, 4.44.

trans-4’,7-Dihydroxy-4-(3-(4’-bromophenyl)-4,6-dimethoxybenzofuran-2-yl) isoflavan (114)

The title compound was synthesized following the MeO OMe Br procedure for isoflavan 79 using compound 113 (100 O mg, 0.15 mmol), methanol (2 mL), KOH solution (1M, OH 20 drops) and acetic acid (1M, 20 drops). The title HO O compound 114 was obtained as a pale yellow solid (72 mg, 83%). M.p. 142-145 C

-1 -1 -1 -1 (from MeOH); UV (MeOH): max 205 ( 86798 cm M ), 224 (57906 cm M ) sh, 260 (

-1 -1 24028 cm M ) nm; IR (KBr): max 3677-3078 (br), 2960, 2934, 2832, 1619, 1598, 1504,

1451, 1465, 1218, 1200, 1148, 1110, 1037, 968, 825, 538 cm-1; 1H NMR (300 MHz, acetone-d6): 3.59 (m, 1H, H3), 3.63 (s, 3H, CH3O), 3.80 (s, 3H, CH3O), 4.10 (dd, J =

10.9, 11.3 Hz, 1H, H2), 4.24 (d, J = 11.3 Hz, 1H, H4), 4.35 (dd, J = 3.8, 10.9 Hz, 1H,

H2), 5.00 (br, 2H, 2 × OH), 6.23 (d, J = 2.0 Hz, H5”), 6.31 (dd, J = 2.7, 8.3 Hz, 1H, H6),

6.43 (d, J = 2.6 Hz, 1H, H8), 6.58 (d, J = 2.0 Hz, 1H, H7”), 6.60 (d, J = 8.7 Hz, 2H, H3”’,

H5’’’), 6.69 (d, J = 8.3 Hz, 1H, H5), 6.74 (d, J = 8.7 Hz, 2H, H2”’, H6’’’), 6.87 (d, J = 8.3

13 Hz, 2H, H3’, H5’), 7.39 (d, J = 8.3 Hz, 2H, H2’, H6’); C NMR (75.6 MHz, acetone-d6)

(After D2O exchange): 38.3 (C3), 42.8 (C4), 55.2 (CH3O), 55.6 (CH3O), 70.2 (C2),

88.3 (ArCH), 94.3 (ArCH), 103.4 (ArCH), 108.5 (ArCH), 110.7 (ArC), 115.1 (ArCH),

115.3 (ArC), 119.4 (ArC), 121.0 (ArC), 128.7 (ArCH), 129.7 (ArCH), 130.5 (ArCH),

131.2 (ArCH), 131.6 (ArC), 150.6 (ArC), 153.9 (ArC), 154.0 (ArC), 154.7 (ArC), 155.2

(ArC), 155.5 (ArC), 155.9 (ArC), 158.8 (ArC); MS (TOF-ESI) m/z Calcd. for

+ 79 81 79 C31H25BrO6Na (M + Na) 595.07 (Br ) and 597.79 (Br ). Found 595.09 (Br ) and

79 597.09 (Br ); Anal. Calcd. for C31H25BrO6: C, 64.93; H, 4.39. Found: C, 64.94; H, 4.50.

166 trans-4’,7-Diacetoxy-4-(4,6-dimethoxy-2,3-diphenylindol-7-yl)isoflavan (115)

The title compound was synthesized following the OMe procedure for diacetoxyisoflavan 78 using isoflavanol

76 (500 mg, 1.46 mmol), diphenylindole 106 (480 mg, MeO N H 1.46 mmol), dichloromethane (50 mL) and BF ·OEt 3 2 OAc

(40 drops). Chromatography (SiO2, 25% ethyl AcO O acetate/hexane) gave the title compound 115 as a white solid (710 mg, 75%). M.p. 215-

-1 -1 -1 -1 217 C; UV (MeOH): max 209 ( 55865 cm M ), 257 ( 26274 cm M ), 324 ( 13905

-1 -1 cm M ) nm; IR (KBr): max 3446, 2955, 2929, 1760, 1600, 1494, 1424, 1368, 1206,

-1 1 1146, 1103, 1019, 912, 697 cm ; H NMR (300 MHz, CDCl3): 2.27 (s, 3H, CH3COO),

2.31 (s, 3H, CH3COO), 3.44 (m, 1H, H3), 3.44 (s, 3H, CH3O), 3.66 (s, 3H, CH3O), 3.49

(m, 2H, 2 × H2), 5.12 (d, J = 9.0 Hz, 1H, H4), 6.12 (s, 1H, H5”), 6.82 -7.50 (m, 18H,

+ ArH, NH); MS (TOF-ESI) m/z Calcd. for C41H35NO7Na (M + Na) 676.23. Found 676.24;

Anal. Calcd. for C41H35NO7·: C, 75.33; H, 5.40; N, 2.14. Found: C, 75.81; H, 5.49; N,

2.20.

trans-4’,7-Dihydroxy-4-(4,6-dimethoxy-2,3-diphenylindol-7-yl)isoflavan (116)

The title compound was synthesized following the OMe procedure for isoflavan 79 using diacetoxyflavan 115

(100 mg, 0.153 mmol), methanol (5 mL), KOH solution MeO N H (1M, 25 drops) and acetic acid (1M, 25 drops). The title OH compound 116 was obtained as a pale yellow solid (70 HO O

-1 -1 - mg, 80%). M.p. 272-274 C; UV (MeOH): max 205 ( 71885 cm M ), 222 ( 44497 cm

1 -1 -1 -1 -1 -1 M ) sh, 259 ( 25942 cm M ), 324 ( 14162 cm M ) nm; IR (KBr): max 3436, 3334,

1614, 1598, 1514, 1503, 1217, 1161, 1153, 1109, 698 cm-1; 1H NMR (300 MHz,

DMSO-d6 + acetone-d6): 3.59 (s, 6H, 2 × CH3O), 4.10 (m, 3H, H3, 2 × H2), 5.14 (d, J

= 10.2 Hz, 1H, H4), 6.10-7.40 (m, 19H, Ar, NH), 8.80 (br, 2H, 2 × OH); MS (TOF-ESI)

167 + m/z Calcd. for C37H31NO5Na (M + Na) 592.20. Found 592.44; Anal. Calcd. for

C37H31NO5: C, 78.01; H, 5.49; N, 2.46. Found: C, 78.01; H, 5.66; N, 2.53.

trans-4’,7-Diacetoxy-4-(4’,7-dimethoxyisoflav-3-ene-6-yl)isoflavan (117)

The title compound was synthesized following the OMe procedure for isoflavan 78 using isoflavanol 76 O (568 mg, 1.66 mmol), isoflavene 112 (445 mg,

1.66 mmol) and BF3·OEt2 (10 drops). MeO

Chromatography (SiO2, 35% ethyl acetate/hexane) OAc gave diacetoxyisoflavan 117 as an off-white solid AcO O

-1 -1 (760 mg, 77%). M.p.128 °C (from MeOH); UV (MeOH): max 209 ( 49001 cm M ), 256

-1 -1 -1 -1 ( 21820 cm M ), 340 ( 24034 cm M ) nm; IR (KBr): max 3500 (br), 2934, 2836,

1758, 1615, 1513, 1496, 1463, 1425, 1368, 1303, 1279, 1248, 1205, 1146, 1109, 1034,

-1 1 1017, 909, 826 cm ; H NMR (300 MHz, CDCl3): 2.25 (s, 3H, CH3COO), 2.27 (s, 3H,

CH3COO), 3.28 (m, 1H, H3), 3.46 (s, 3H, CH3O), 3.80 (s, 3H, CH3O), 4.25 (dd, J = 7.5,

10.9 Hz, 1H, H2), 4.33 (dd, J = 3.4, 10.9 Hz, 1H, H2), 4.61 (d, J = 7.5 Hz, 1H, H4), 5.08

(d, J = 1.1 Hz, 2H, 2 × H2’’), 6.36 (s, 1H, H8’’), 6.56 (m, 3H, H4’’, H5’’, H6), 6.67 (d, J =

2.3 Hz, 1H, H8), 6.81 (d, J = 8.3 Hz, 1H, H5), 6.87 (d, J = 8.6 Hz, 2H, H3’’’, H5’’’), 6.95

(d, J = 8.7 Hz, 2H, H3’, H5’), 7.19 (d, J = 8.6 Hz, 2H, H2’’’, H6’’’), 7.30 (d, J = 8.7 Hz,

13 2H, H2’, H6’); C NMR (75.6 MHz, CDCl3): 20.98 (CH3COO), 21.03 (CH3COO), 30.8

(C3), 44.5 (C4), 55.0 (CH3O), 55.5 (CH3O), 67.2 and 68.8 (2 × CH2), 98.8 (ArCH),

109.5 (ArCH), 113.9 (ArCH), 114.0 (ArCH), 115.8 (ArC), 118.0 (ArCH), 121.2 (ArCH),

122.5 (ArC), 125.6 (ArCH), 127.7 (ArCH), 128.1 (ArC), 128.7 (ArCH), 128.9 (ArC),

129.4 (ArC), 130.9 (ArCH), 138.4 (ArC), 149.3 (ArC), 149.7 (ArC), 152.9 (ArC), 155.4

(ArC), 157.7 (ArC), 159.1 (ArC), 169.2 (COO) and 169.3 (COO); MS (MALDI-ESI) m/z

+ + + Calcd. for C36H32O8 (M) 592.20. Found 591.19 (M-1) , 592.19 (M) ; Anal. Calcd. for

C36H32O8: C, 72.96; H, 5.44. Found: C, 72.73; H, 5.54.

168 trans-4’,7-Dihydroxy-4-(4’,7-dimethoxyisoflav-3-ene-6-yl)isoflavan (118)

The title compound was synthesized following the OMe procedure for dihydroxyisoflavan 79 using O diacetoxyisoflavan 117 (50 mg, 0.084 mmol), methanol (1 mL), KOH solution (1M, 10 drops) and MeO OH acetic acid (1M, 10 drops). The dihydroxyisoflavan HO O 118 was obtained as a pale yellow solid (32 mg,

-1 -1 -1 -1 74%). M.p. 111 C ; UV (MeOH): max 205 ( 65677 cm M ), 239 ( 27326 cm M ),

-1 -1 257 ( 25131 cm M ) sh, nm; IR (KBr): max 3394, 2955, 2842, 1615, 1513, 1465,

-1 1 1445, 1303, 1248, 1159, 1181, 1032, 826 cm ; H NMR (300 MHz, acetone-d6): 3.25

(m, 1H, H3), 3.73 (s, 3H, CH3O), 3.80 (s, 3H, CH3O), 4.17 (m, 2H, 2 × H2), 4.55 (d, J =

8.3 Hz, 1H, H4), 5.06 (s, 2H, 2 × H2’’), 6.29 (dd, J = 2.6, 8.3 Hz, 1H, H6), 6.31 (d, J =

2.6 Hz, 1H, H8), 6.54 (d, J = 8.3 Hz, 1H, H5), 6.69 (m, 4H, H3’, H5’, H4’’, H5’’), 6.91 (d,

J = 8.7 Hz, 2H, H3’’’, H5’’’), 7.09 (d, J = 8.3 Hz, 2H, H2’, H6’), 7.42 (d, J = 8.7 Hz, 2H,

13 H2’’’, H6’’’), 8.07 (br, 2H, 2 × OH); C NMR (75.6 MHz, acetone-d6): 29.1 (C3), 44.0

(C4), 54.6 and 55.2 (2 × CH3O), 66.6, 69.1 (2 × CH2), 98.8 (ArCH), 102.4 (ArCH), 108.2

(ArCH), 113.9 (ArCH), 114.9 (ArCH), 115.8 (ArC), 116.5 (ArC), 117.7 (ArCH), 125.6

(ArCH), 126.0 (ArC), 127.6 (ArCH), 128.1 (ArC), 128.8 (ArCH), 129.2 (ArC), 130.6

(ArCH), 132.1 (ArC), 152.7 (ArC), 155.7 (ArC), 155.9 (ArC), 156.6 (ArC), 158.1 (ArC),

+ 159.3 (ArC); MS (TOF-ESI) m/z Calcd. for C32H28O6Na (M + Na) 531.17. Found

531.18; Anal. Calcd. for C36H28O6·H2O: C, 72.99; H, 5.74. Found: C, 72.73; H, 5.66.

trans-4’,7-Diacetoxy-4-(4’,7-dihydroxyisoflav-3-ene-6-yl)isoflavan (119)

The title compound was synthesized following O OH the procedure for isoflavan 78 using isoflavanol HO 76 (500 mg, 1.46 mmol), phenoxodiol 111 (387 OAc mg, 1.61 mmol), dichloromethane (40 mL) and AcO O

BF3·OEt2 (40 drops). Chromatography (SiO2, 30% ethyl acetate/hexane) gave the title 169 compound 119 as a pink solid (290 mg, 35%). M.p. 210 C (dec); UV (MeOH): max 206

( 53629 cm-1M-1), 255 ( 14137 cm-1M-1), 282 ( 12717 cm-1M-1), 330 ( 19092 cm-1M-1)

-1 1 nm; IR (KBr): max 3418, 3032, 1757, 1736, 1616, 1589, 1506, 1224 cm ; H NMR (300

MHz, CDCl3): 2.25 and 2.28 (2 × s, 6H, 2 × CH3COO), 3.37 (m, 1H, H3), 4.25 (dd, J =

8.7, 11.2 Hz, 1H, H2), 4.35 (dd, J = 3.8, 11.2 Hz, 1H, H2), 4.50 (d, J = 8.7 Hz, 1H, H4),

5.02 (s, 2H, 2 × H2’’), 5.18 (br, 2H, 2 × OH), 6.20 (s, 1H, H8’’), 6.48 (s, 1H, H4’’), 6.51

(s, 1H, H5’’), 6.57 (dd, J = 2.3, 8.7 Hz, 1H, H6), 6.68 (d, J = 2.3 Hz, 1H, H8), 6.78 and

6.94 (2 × d, J = 8.7 Hz, 4H, H3’, H5’, H3’’’, H5’’’), 6.87 (d, J = 8.7 Hz, 1H, H5), 7.17 and

13 7.21 (2 × d, J = 8.7 Hz, 4H, H2’, H6’, H2’’’, H6’’’); C NMR (75.6 MHz, CDCl3): 21.0 and 21.04 (2 × CH3COO), 41.5 and 44.1 (C3, C4), 67.0 and 69.0 (C2, C2’’), 102.9

(ArCH), 109.6 (ArCH), 114.0 (ArCH), 115.5 (ArCH), 116.2 (ArC), 117.8 (ArCH), 121.3

(ArCH), 122.6 (ArC), 123.1 (ArC), 125.7 (ArCH), 128.0 (ArC), 128.1 (ArCH), 128.8

(ArCH), 129.1 (ArC), 131.0 (ArCH), 138.3 (ArC), 149.2 (ArC), 149.7 (ArC), 152.4 (ArC),

154.2 (ArC), 155.3 (ArC), 155.5 (ArC), 170.1 and 170.1 (2 × COO); MS (TOF-ESI) m/z

+ Calcd. for C34H28O8Na (M + Na) 587.16. Found 587.16; Anal. Calcd. for

1 C34H28O8· /2H2O: C, 71.19; H, 5.10. Found: C, 70.83; H, 4.99.

4,2’,4’-Trihydroxychalcone (125)

To a mixture of resacetophenone 123 (6.8 g, 44.7 O mmol), 4-hydroxybenzaldehyde 124 (5.6 g, 45.9 mmol) HO OH and ethanol (5.6 mL) was added aqueous KOH (41.6 OH mL, 60% w/w). The resulting suspension was heated at 100 ºC for 1.5 h and then kept overnight at r.t. The reaction mixture was poured onto ice (100.0 g) and acidified to pH

4 using conc. hydrochloric acid. The precipitated solid was filtered, washed with water

(200 mL) and air dried to give trihydroxychalcone 125 as a yellow solid (7.5 g, 65%).

116 - M.p. 200 C (from MeOH/water), lit. 200-201 C; UV (MeOH): max 203 ( 21601 cm

1 -1 -1 -1 M ), 371 ( 19967 cm M ) nm; IR (KBr): max 3383, 1627, 1605, 1513, 1225, 1211,

170 -1 1 1143 cm ; H NMR (300 MHz, acetone-d6): 6.35 (d, J = 2.3 Hz, 1H, H3’), 6.45 (dd, J

= 2.3, 8.7 Hz, 1H, H5’), 6.91 (d, J = 8.7 Hz, 2H, H3, H5), 7.72 (d, J = 8.7 Hz, 2H, H2,

H6), 7.74 (d, J = 16.2 Hz, 1H, H), 8.83 (d, J = 16.2 Hz, 1H, H), 8.10 (d, J = 8.7 Hz, 1H,

H6’), 9.10 (br, 2H, 4-OH, 4’-OH). 13.59 (s, 1H, 2’-OH); 13C NMR (75.6 MHz, acetone- d6): 102.5 (ArCH), 107.7 (ArCH), 113.6 (ArC), 115.8 (ArCH), 117.4 (C), 126.6 (ArC),

130.8 (ArCH), 132.3 (ArCH), 144.1 (C), 160.0 (ArC), 164.6 (ArC), 166.6 (ArC), 191.9

(C=O).

4’,7-Dihydroxyflavanone (126)

A suspension of chalcone 125 (3.0 g, 11.7 mmol) in O methanol (50 mL) and conc. hydrochloric acid (25 mL) HO O was refluxed for 24 h. Methanol was removed under OH vacuum and the resulting dark solution was diluted with water. The product was extracted with ethyl acetate (100 mL × 3), the extract dried over anhydrous sodium sulfate and the solvent evaporated under vacuum. Chromatography (SiO2, 50% ethyl acetate/hexane) gave the dihydroxyflavanone 126 as a pale yellow solid (1.86 g, 62%).

116 M.p. 195-197 C (from benzene/hexane), lit. 195-196 C; UV (MeOH): max 212 (

25040 cm-1M-1), 230 ( 18805 cm-1M-1) sh, 275 ( 13611 cm-1M-1), 311 ( 7472 cm-1M-1),

-1 -1 - 369 ( 3692 cm M ) nm; IR (KBr): max 3377, 1656, 1601, 1516, 1465, 1234, 1163 cm

1 1 ; H NMR (300 MHz, acetone-d6): 2.66 (dd, J = 3.0, 16.8 Hz, 1H, H3), 3.03 (dd, J =

13.0, 16.8 Hz, 1H, H3), 5.44 (dd, J = 3.0, 13.0 Hz, 1H, H2), 6.41 (d, J = 2.3 Hz, 1H,

H8), 6.56 (dd, J = 2.3, 8.7 Hz, 1H, H6), 6.88 (d, J = 8.7 Hz, 2H, H3’, H5’), 7.38 (d, J =

8.7 Hz, 2H, H2’, H6’), 7.71 (d, J = 8.7 Hz, 1H, H5), 8.45 (br, 1H, OH), 9.30 (br, 1H, OH);

13 C NMR (75.6 MHz, acetone-d6): 43.7 (C3), 79.5 (C2), 102.7 (ArCH), 110.2 (ArCH),

114.3 (ArC), 115.2 (ArCH), 128.0 (ArCH), 128.5 (ArCH), 130.3 (ArC), 157.5 (ArC),

163.5 (ArC), 164.2 (ArC), 189.6 (C=O).

171 4’,7-Diacetoxyflavanone (127)

A mixture of flavanone 126 (500 mg, 1.95 mmol), O pyridine (0.6 mL) and acetic anhydride (3 mL) was AcO O heated with stirring at 100 ºC for 1 h. The reaction OAc mixture was cooled to r.t. After 2 h the precipitated white solid was filtered, washed with methanol-water (10 mL, 50:50) and air dried (510 mg, 76%). M.p. 192-194 C, lit.277

-1 -1 -1 -1 195-198 C; UV (MeOH): max 215 ( 30455 cm M ), 256 ( 11970 cm M ), 313 (

-1 -1 4229 cm M ) nm; IR (KBr): max1763, 1742, 1693, 1609, 1511, 1441, 1425, 1370,

-1 1 1282, 1246, 1196, 1142, 1118, 1063, 1013, 914 cm ; H NMR (300 MHz, CDCl3):

2.30 (s, 3H, CH3COO), 2.31 (s, 3H, CH3COO), 2.88 (dd, J = 3.0, 16.8 Hz, 1H, H3), 3.05

(dd, J = 13.0, 16.8 Hz, 1H, H3), 5.50 (dd, J = 3.0, 13.0 Hz, 1H, H2), 6.82 (d, J = 2.3 Hz,

1H, H8), 6.83 (dd, J = 2.3, 8.3 Hz, 1H, H6), 7.16 (d, J = 8.3 Hz, 2H, H3’, H5’), 7.48 (d, J

13 = 8.3 Hz, 2H, H2’, H6’), 7.95 (d, J = 8.3 Hz, 1H, H5); C NMR (75.6 MHz, CDCl3):

19.9 and 20.0 (2 × CH3COO), 43.7 (C3), 79.4 (C2), 111.0 (ArCH), 115.6 (ArCH), 118.7

(ArC), 121.9 (ArCH), 127.5 (ArCH), 127.7 (ArCH), 136.5 (ArC), 151.1 (ArC), 156.7

(ArC), 162.2 (ArC), 168.1 (COO), 168.6 (COO), 189.7 (C=O).

cis-4’,7-Diacetoxyflavan-4-ol (128)

To a solution of diacetoxyflavanone 127 (700 mg, 2.05 OH mmol) in THF (28 mL) was added 10% palladium on AcO O charcoal (200 mg). The mixture was hydrogenated at OAc r.t. for 48 h and filtered through a pad of Celite®. Evaporation of the solvent under vacuum afforded diacetoxyflavanol 128 as a white solid (630 mg, 90%). M.p. 156-158

-1 -1 -1 -1 C (from MeOH); UV (MeOH): max 207 ( 26529 cm M ), 276 ( 1968 cm M ) nm; IR

(KBr): max 3471, 1756, 1738, 1613, 1588, 1494, 1425, 1371, 1219, 1196, 1142, 1117,

-1 1 1017, 968, 914, 832 cm ; H NMR (300 MHz, CDCl3): 2.10 (ddd, J = 10.4, 11.7, 13.2

Hz, 1H, H3), 2.28 (s, 3H, CH3COO), 2.30 (s, 3H, CH3COO), 2.51 (ddd, J = 1.9, 6.4,

172 13.2 Hz, 1H, H3), 5.07 (dd, J = 6.4, 10.4 Hz, 1H, H2), 5.18 (dd, J = 1.9, 11.7 Hz, 1H,

H4), 6.62 (d, J = 2.3 Hz, 1H, H8), 6.72 (dd, J = 2.3, 8.7 Hz, 1H, H6), 7.12 (d, J = 8.7 Hz,

2H, H3’, H5’), 7.44 (d, J = 8.7 Hz, 2H, H2’, H6’), 7.52 (d, J = 8.7 Hz, 1H, H5); 13C NMR

(75.6 MHz, CDCl3): 20.9 and 21.0 (CH3COO), 39.7 (C3), 65.3 (C4), 76.6 (C2), 109.8

(ArCH), 114.3 (ArCH), 121.7 (ArCH), 123.5 (ArC), 127.1 (ArCH), 127.7 (ArCH), 137.7

(ArC), 150.4 (ArC), 150.9 (ArC), 155.0 (ArC), 169.4 (2 × COO); HRMS (ESI) m/z Calcd.

+ for C19H18O6Na (M + Na) 365.0995. Found 365.0996; Anal. Calcd. for C19H18O6: C,

66.65; H, 5.29. Found: C, 66.35; H, 5.35.

4’,7-Diacetoxy-4-(3-acetyl-2-hydroxy-4-methoxyphenyl)flavan (132, 134)

To a stirred solution of flavanol 128 (500 mg, 1.46 mmol) and 2’-hydroxy-6’- methoxyacetophenone 77 (242 mg, 1.62 mmol) in dichloromethane (25 mL) was added

BF3·OEt2 (15 drops). The mixture was stirred for 2 h and then quenched by addition of water (25 mL). The mixture was stirred for 10 min and the organic layer was separated.

The aqueous layer was extracted with dichloromethane (25 mL × 2). The combined organic extract was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 25% ethyl acetate/hexane) gave the title compound as

1:1 mixture of cis/trans isomers (265 mg, 37%). TLC analysis using several solvent systems failed to achieve separation between the two isomers.

The mixture (260 mg) was rechromatographed on a 20 inch long silica column. The compound was collected in 30 small fractions. The initial fractions gave almost pure trans flavan 132 (30 mg). This was followed by mixture of both isomers. The last fractions gave predominantly cis flavan 134 with about 15% trans isomer (50 mg).

173 trans isomer (132)

White solid. M.p. 185-187 C; UV (MeOH): max 208 OMe O ( 61079 cm-1M-1), 222 ( 63682 cm-1M-1), 274 (

-1 -1 27514 cm M ) nm; IR (KBr): max 3446 (br), 1761, OH

1602, 1424, 1368, 1209, 1141, 1118 cm-1; 1H NMR AcO O (300 MHz, CDCl3): 2.22 (m, 1H, H3), 2.27 (s, 3H, OAc

CH3COO), 2.29 (s 3H, CH3COO), 2.33 (m, 1H, H3), 2.70 (s, 3H, CH3CO), 3.87 (s, 3H,

CH3O), 4.57 (t, J = 4.1 Hz, 1H, H4), 4.88 (dd, J = 4.9, 8.7 Hz, 1H, H2), 6.29 (d, J = 8.3

Hz, 1H, H5’’), 6.64 (dd, J = 2.3, 8.6 Hz, 1H, H6), 6.74 (d, J = 2.3 Hz, 1H, H8), 6.89 (d, J

= 8.6 Hz, 1H, H5), 6.96 (d, J = 8.3 Hz, 1H, H6’’), 7.04 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.33

13 (d, J = 8.6 Hz, 2H, H2’, H6’), 13.83 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 20.99

(CH3COO), 21.03 (CH3COO), 33.6 (CH3CO), 35.1 (C3), 55.4 (CH3O), 73.3 (C2), 100.1

(ArCH), 110.1 (ArCH), 110.7 (ArC), 114.0 (ArCH), 120.5 (ArC), 121.4 (ArCH), 126.3

(ArC), 127.2 (ArCH), 131.1 (ArCH), 136.8 (ArCH), 138.5 (ArC), 150.1 (ArC), 156.3

(ArC), 160.1 (ArC), 161.5 (ArC), 169.2 (COO), 169.3 (COO), 205 (C=O); HRMS (TOF-

+ ESI) m/z Calcd. for C28H26O8Na (M + Na) 513.1525. Found 513.1306 Anal. Calcd. for

1 C28H26O8· /2H2O: C, 67.33; H, 5.45. Found: C, 67.36; H, 5.64.

cis isomer (134)

-1 -1 OMe O White solid. UV (MeOH): max 210 ( 60079 cm M ),

228 ( 6462 cm-1M-1), 275 ( 22827 cm-1M-1) nm; IR OH

(KBr): max 3435 (br), 1763, 1614, 1428, 1368, 1212,

-1 1 1143, 1109, cm ; H NMR (300 MHz, CDCl3): 2.22 AcO O

(m, 1H, H3), 2.27 (s, 3H, CH3COO), 2.29 (s, 3H, OAc

CH3COO), 2.41 (m, 1H, H3), 2.70 (s, 3H, CH3CO), 3.88 (s, 3H, CH3O), 4.68 (m, 1H,

H4), 5.23 (m, 1H, H2), 6.34 (d, J = 8.7 Hz, H5’’), 6.55 (dd, J = 2.3, 8.6 Hz, 1H, H6), 6.68

(d, J = 2.3 Hz, 1H, H8), 6.81 (d, J = 8.6 Hz, 1H, H5), 7.10 (d, J = 8.3 Hz, 2H, H3’, H5’),

174 7.15 (d, J = 8.7 Hz, 1H, H6’’), 7.46 (d, J = 8.3 Hz, 2H, H2’, H6’), 13.75 (s, 1H, 2’’ OH);

13 C NMR (300 MHz, CDCl3): 21.0 (2 × CH3COO), 29.6 (C4), 33.6 (CH3CO), 38.1

(C3), 55.5 (CH3O), 78.1 (C2), 101.0 (ArCH), 110.2 (ArCH), 113.8 (ArCH), 121.4 (ArC),

121.48 (ArCH), 123.0 (ArC), 127.0 (ArCH), 127.2 (ArC), 129.7 (ArC), 135.5 (ArC),

138.6 (ArC), 149.7 (ArC), 150.2 (ArC), 156.3 (ArC), 160.3 (ArC), 162.4 (ArC), 169.2

(COO), 169.3 (COO), 205.3 (CO); HRMS (TOF-ESI) m/z Calcd. for C28H26O8Na (M +

+ 1 Na) 513.1525. Found 513.1401 Anal. Calcd. for C28H26O8· /2H2O: C, 67.33; H, 5.45.

Found: C, 67.36; H, 5.64.

4’,7-Dihydroxy-4-(3-acetyl-2-hydroxy-4-methoxyphenyl)flavan (133, 135)

trans isomer (133)

The title compound was synthesized following the OMe O procedure for isoflavan 79 using trans-diacetoxyflavan

132 (30 mg, 0.06 mmol). Compound 133 was obtained OH as a white solid (24 mg, 97%). M.p. 258-260 C; UV HO O (MeOH): 208 ( 43446 cm-1M-1), 224 ( 38844 cm- max OH 1 -1 -1 -1 -1 -1 M ), 276 ( 16180 cm M ), 347 (3255 cm M ) nm; IR (KBr): max 3416 br, 1614,

-1 1 1506, 1426, 1240, 1110 cm ; H NMR (300 MHz, CDCl3): 2.25 (m, 2H, 2 × H3), 2.66

(s, 3H, CH3CO), 3.90 (s, 3H, CH3O), 4.45 (dd, J = 2.3, 5.3 Hz, 1H, H4), 4.80 (dd, J =

2.6, 10.5 Hz, 1H, H2), 6.40 (d, J = 1.9 Hz, 1H, H8), 6.41 (dd, J = 1.9, 9.0 Hz, 1H, H6),

6.49 (d, J = 8.6 Hz, 1H, H5’’), 6.74 (d, J = 9.0 Hz, 1H, H5), 6.79 (d, J = 8.7 Hz, 2H, H3’,

H5’), 6.92 (d, J = 8.6 Hz, 1H, H6’’), 7.15 (d, J = 8.7 Hz, 2H, H2’, H6’), 8.19 (br, 1H, OH),

13 8.23 (br, 1H, OH), 13.87 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 32.8 (CH3CO),

33.2 (C4), 35.4 (C3), 55.2 (CH3O), 73.3 (C2), 100.6 (ArCH), 102.8 (ArCH), 108.6

(ArCH), 110.4 (ArC), 113.9 (ArC), 115.0 (ArCH), 126.8 (ArC), 127.4 (ArCH), 131.0

(ArCH), 132.4 (ArC), 136.8 (ArCH), 156.9 (ArC), 156.9 (ArC), 157.1 (ArC), 160.1 (ArC),

+ 161.4 (ArC), 206.1 (C=O); HRMS (TOF-ESI) m/z Calcd. for C24H22O6Na (M + Na) 175 429.1314. Found 429.1166; Anal. Calcd. for C24H22O6: C, 70.92; H, 5.46. Found: C,

70.67; H, 5.66.

cis isomer (135)

The title compound was synthesized following the OMe O procedure for isoflavan 79 using cis-diacetoxyflavan 134

(30 mg, 0.06 mmol). Compound 135 was obtained as a OH white solid (21 mg, 85%). UV (MeOH): max. 213 ( 43543 HO O cm-1M-1), 232 ( 36622 cm-1M-1), 286 ( 19190 cm-1M-1), OH -1 -1 -1 1 345 (3333 cm M ) nm; IR (KBr): max 3410 (br), 1615, 1500, 1426, 1246, 1116 cm ; H

NMR (300 MHz, acetone-d6): 2.05 (m, 1H, H3), 2.20 (m, 1H, H3), 2.66 (s, 3H,

CH3CO), 3.93 (s, 3H, CH3O), 4.70 (m, 1H, H4), 5.10 (d, J = 12.8 Hz, 1H, H2), 6.30 (m,

2H, H5’’, H6), 6.55 (m, 2H, H8, H5), 6.84 (d, J = 8.7 Hz, H3’, H5’), 7.25 (d, J = 8.6 Hz,

H6’’), 7.32 (d, J = 8.7 Hz, 2H, H2’, H6’), 8.29 (br, 2H, 2 × OH), 13.80 (brs, 1H, OH); 13C

NMR (75.6 MHz, acetone-d6): 32.8 (CH3CO), 33.2 (C4), 35.4 (C3), 55.2 (CH3O), 77.9

(C2), 101.5 (ArCH), 103.0 (ArCH), 108.1 (ArCH), 110.4 (ArC), 115.0 (ArCH), 116.6

(ArC), 127.4 (ArCH), 129.5 (ArC), 131.0 (ArCH), 132.7 (ArC), 136.8 (ArCH), 156.6

(ArC), 156.8 (ArC), 157.0 (ArC), 160.4 (ArC), 162.2 (ArC), 206.1 (C=O); HRMS (TOF-

+ ESI) m/z Calcd. for C24H22O6Na (M + Na) 429.1314. Found 429.1166; Anal. Calcd. for

C24H22O6: C, 70.92; H, 5.46. Found: C, 70.80; H, 5.44.

4’,7-Diacetoxy-4-(3-acetyl-4-hydroxy-6-methoxyphenyl)flavan (136, 138)

The title compound was synthesized following the procedure for flavans 132 and 134 using flavanol 128 (1000 mg, 2.92 mmol), 2’-hydroxy-4’-methoxyacetophenone 80 (484 mg, 3.24 mmol), dichloromethane (50 mL) and BF3·OEt2 (20 drops). Chromatography

(SiO2, 25% ethyl acetate/hexane) gave the title compound as 1:1 mixture of cis/trans isomers (958 mg, 67%). TLC analysis using several solvent systems failed to achieve separation between the two isomers. The mixture (260 mg) was rechromatographed on

176 a 20 inch long silica column. The compound was collected into 30 small fractions. The initial fractions gave almost pure trans flavan 136 (30 mg). This was followed by a mixture of both isomers. The last fractions gave predominantly cis flavan 138 contaminated with about 15% trans isomer (50 mg).

trans isomer (136)

- M.p. 189-190 C; UV (MeOH): max 206 ( 47375 cm O OH

1M-1), 231 ( 29921 cm-1M-1), 275 ( 17122 cm-1M-1), OMe -1 -1 324 ( 6651 cm M ) nm; IR (KBr): max 3431(br),

1762, 1634, 1495, 1370, 1205, 1143 cm-1; 1H NMR AcO O

(300 MHz, CDCl3): 2.20 (m, 1H, H3), 2.25 (m, 1H, OAc

H3), 2.26 (s, 3H, CH3COO), 2.28 (s, 3H, CH3COO), 2.31 (s, 3H, CH3CO), 3.90 (s, 3H,

CH3O), 4.46 (dd, J = 2.6, 5.3 Hz, 1H, H4), 4.89 (dd, J = 3.0, 10.6 Hz, 1H, H2), 6.46 (s,

1H, H5’’), 6.66 (dd, J = 2.3, 8.3 Hz, 1H, H6), 6.76 (d, J = 2.3 Hz, 1H, H8), 6.96 (d, J =

8.3 Hz, 1H, H5), 7.00 (s, 1H, H2’’), 7.06 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.33 (d, J = 8.6

13 Hz, 2H, H2’, H6’), 12.74 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 20.98 (CH3COO),

21.00 (CH3COO), 25.9 (CH3CO), 33.8 (C4), 35.6 (C3), 55.8 (CH3O), 73.3 (C2), 99.4

(ArCH), 110.2 (ArCH), 113.0 (ArC), 114.2 (ArCH), 119.0 (ArC), 121.5 (ArCH), 125.5

(ArC), 127.2 (ArCH), 131.0 (ArCH), 132.3 (ArCH), 138.4 (ArC), 150.3 (ArCH), 156.2

(ArC), 163.0 (ArC), 164.2 (ArC), 169.3 (COO), 202.7 (C=O); HRMS (TOF-ESI) m/z

+ Calcd. for C28H26O8Na (M + Na) 513.1525. Found 513.1366; Anal. Calcd. for

1 C28H26O8· /2H2O: C, 67.33; H, 5.45. Found: C, 67.36; H, 5.54.

177 cis isomer (138) .

-1 -1 White solid. UV (MeOH): max 206 ( 47375 cm M ), O OH 231 ( 29921 cm-1M-1), 275 ( 17122 cm-1M-1), 324 (

-1 -1 OMe 6651 cm M ) nm; IR (KBr): max 3431(br), 1762, 1634,

1495, 1370, 1205, 1143 cm-1; 1H NMR (300 MHz, AcO O CDCl3): 2.27 (s, 3H, CH3COO), 2.29 (s, 3H, OAc

CH3COO), 2.28 (m, 2H, 2 × H3), 2.45 (s, 3H, CH3CO), 3.84 (s, 3H, CH3O), 4.69 (m, 1H,

H4), 5.23 (d, J = 12.4 Hz, 1H, H2), 6.46 (s, 1H, H5’’), 6.55, (dd, J = 2.3, 8.3 Hz, 1H, H6)

6.70 (d, J = 2.3 Hz, 1H, H8), 6.77 (d, J = 8.3 Hz, 1H, H5), 7.11 (d, J = 8.3 Hz, 2H, H3’,

H5’), 7.37 (s, 1H, H2’’), 7.48 (d, J = 8.3 Hz, 2H, H2’, H6’), 12.71 (s, 1H, OH); 13C NMR

(75.6 MHz, CDCl3): 21.0 (2 × CH3COO), 26.2 (CH3CO), 33.8 (C4), 35.6 (C3), 55.8

(CH3O), 77.9 (C2), 110.3 (ArCH), 113.6 (ArCH), 113.8 (ArC), 121.6 (ArCH), 122.8

(ArC), 125.5 (ArC), 127.0 (ArCH), 129.3 (ArC), 132.4 (ArC), 138.4 (ArC), 149.8 (ArC),

156.2 (ArC), 150.3 (ArC), 163.0 (ArC), 163.9 (COO), 169.3 (COO), 202.6 (C=O);

+ HRMS (TOF-ESI) m/z Calcd. for C28 H 26 O 8 Na (M + Na) 513.1525. Found 513.1382;

Anal. Calcd. for C28 H 26 O 8 : C, 68.56; H, 5.34. Found: C, 68.36; H, 5.54.

4’,7-Dihydroxy-4-(3-acetyl-4-hydroxy-6-methoxyphenyl)flavan

trans isomer (137)

The title compound was synthesized following the O OH procedure for isoflavan 79 using diacetoxyflavan 136 OMe (20 mg, 0.04 mmol). Compound 137 was obtained as a white solid (16 mg, 87%). M.p. 205-210 C; UV HO O (MeOH): 206 ( 40334 cm-1M-1), 219 ( 30387 cm- max OH

1-1 -1-1 -1-1 M ), 275 ( 13479 cm M ), 325 ( 4693 cm M ) nm; IR (KBr): max 3418 br, 1632,

1 1506, 1372, 1257, 1205, 1154; H NMR (acetone-d6 + CDCl3): 2.20 (m, 1H, H3), 2.05

178 (m, 1H, H3), 2.85 (s, 3H, CH3CO), 3.91 (s, 3H, CH3O), 4.36 (dd, J = 2.3, 5.7 Hz, 1H,

H4), 4.77 (dd, J = 2.3, 10.9 Hz, 1H, H2), 6.41 (m, 3H, H5’’, H6, H8), 6.75 (m, 3H, H5,

H3’, H5’), 7.12 (m, 3H, H2’’, H2’, H6’), 8.12 (s, 1H, OH), 8.14 (s, 1H, OH), 12.68 (s, 1H,

13 OH); C NMR (acetone-d6 + CDCl3): 26.1 (CH3CO), 34.2 (C4), 36.5 (C3), 56.3

(CH3O), 73.8 (C2), 99.8 (ArCH), 103.7 (ArCH), 109.4 (ArCH), 113.4 (ArC), 114.2 (ArC),

115.7 (ArCH), 127.2 (ArC), 128.2 (ArCH), 131.7 (ArCH), 133.1 (ArCH), 133.2 (ArC),

157.6 (ArC), 157.8 (ArC), 164.0 (ArC), 164.8 (ArC), 203.4 (C=O); HRMS (TOF-ESI) m/z

+ Calcd. for C24H22O6Na (M + Na) 429.1314. Found 429.1280.

cis isomer (139)

The title compound was synthesized following the O OH procedure for isoflavan 79 using compound 138 (20 mg, OMe 0.04 mmol). Compound 139 was obtained as a white

1 solid (14 mg, 100%). H NMR (acetone-d6): 2.05 (m, HO O 1H, H3), 2.10 (m, 1H, H3), 2.45 (s, 3H, CH CO), 3.89 (s, 3 OH

3H, CH3O), 4.62 (m, 1H, H4), 5.11 (m, 1H, H2), 6.29 (dd, J = 2.3, 8.3 Hz, 1H, H6), 6.33

(s, 1H, H5’’), 6.33 (d, J = 2.3 Hz, H8), 6.51 (s, 1H, H2’’), 6.54 (d, J = 8.3 Hz, 1H, H5),

6.84 (d, J = 8.3 Hz, 2H, H3’, H5’), 7.32 (d, J = 8.3 Hz, 2H, H2’, H6’), 7.61 (br, 2H, OH),

+ 12.71 (br, 1H, OH); HRMS (TOF-ESI) m/z Calcd. for C24H22O6Na (M + Na) 429.1314.

Found 429.1320.

4’,7-Diacetoxy-4-(3-(4-bromophenyl)-4,6-dimethoxybenzofuran-2-yl)flavan (141)

The title compound was synthesized following the procedure for flavans 132 and 134 using flavanol 128 (286 mg, 0.836 mmol), benzofuran 103 (280 mg, 0.84 mmol), dichloromethane (5 mL) and BF3·OEt2 (6 drops). Chromatography (SiO2, 25% ethyl acetate/hexane) gave the title compound as a 1:1 mixture of cis/trans isomers (160 mg,

29%). The mixture was rechromatographed on a 20 inch long silica column. The compound was collected into 30 small fractions. The initial fractions gave

179 predominantly trans flavan 141 (27 mg). Remaining fractions were all 50:50 mixture of

(cis:trans) isomers

trans isomer (141)

White solid. M.p. 226-228 C (from MeOH); UV OMe MeO Br -1 -1 (MeOH): max 204 ( 74131 cm M ), 259 ( 21491

-1 -1 cm M ) nm; IR (KBr): max 2921, 1756, 1674, 1618, O

1500, 1418, 1201, 1144, 1108 cm-1; 1H NMR (300 AcO O MHz, CDCl3): 2.26 (s, 3H, CH3COO), 2.30 (m, 1H, OAc

H3), 2.31 (s, 3H, CH3COO), 2.40 (m, 1H, H3), 3.70 (s, 3H, CH3O), 3.82 (s, 3H, CH3O),

4.23 (m, 1H, H4), 5.60 (dd, J = 3.0, 9.0 Hz, 1H, H2), 6.30 (d, J = 1.9 Hz, 1H, H5’’), 6.54

(dd, J = 2.3, 8.3 Hz, 1H, H6), 6.61 (d, J = 2.3 Hz, 1H, H8), 6.73 (d, J = 1.9 Hz, 1H, H7’’),

6.82 (d, J = 8.3 Hz, 1H, H5), 7.09 (d, J = 8.3 Hz, 2H, H3’, H5’), 7.29 (d, J = 8.3 Hz, 2H,

H3’’’, H5’’’), 7.40 (d, J = 8.3 Hz, 2H, H2’, H6’), 7.50 (d, J = 8.3 Hz, 2H, H2’’’, H6’’’); 13C

NMR (75.6 MHz, CDCl3): 21.0 (2 × CH3COO), 31.0 (C4), 35.6 (C3), 55.3 (CH3O),

55.7 (CH3O), 74.5 (C2), 88.2 (ArCH), 94.5 (ArCH), 110.4 (ArCH), 110.8 (ArC), 114.0

(ArCH), 116.6 (ArC), 118.8 (ArC), 121.1 (ArC), 121.6 (ArCH), 121.61 (ArC), 126.9

(ArCH), 130.1 (ArCH), 130.9 (ArCH), 131.6 (ArC), 131.8 (ArCH), 138.4 (ArC), 150.2

(ArC), 150.3 (ArC), 153.6 (ArC), 154.3 (ArC), 155.2 (ArC), 156.0 (ArC), 158.9 (ArC),

+ 169.1 (COO), 169.2 (COO); HRMS (TOF-ESI) m/z Calcd. for C35H29BrO8Na (M + Na)

679.0944 (Br79) and 681.0923 (Br81). Found 679.0061 (Br79) and 681.0572 (Br81); Anal.

Calcd. for C35H29BrO8: C, 63.93; H, 4.45. Found: C, 63.48; H, 4.44.

180 trans-4’,7-Dihydroxy-4-(3-(4-bromophenyl)-4,6-dimethoxybenzofuran-2-yl)flavan

(142)

The title compound was synthesized following the OMe MeO Br procedure for isoflavan 79 using compound 141 (27 mg, 0.041 mmol). Compound 142 was obtained as a O white solid (20 mg, 83%). M.p. 232-234 C (from HO O -1 -1 MeOH); UV (MeOH): max 205 ( 68660 cm M ), 225 OH -1 -1 -1 -1 ( 4339 cm M ) sh, 260 ( 19080 cm M ) nm; IR (KBr): max 3398, 1618, 1505, 1457,

-1 1 1216, 1148, 1109 cm ; H NMR (300 MHz, CDCl3): 2.37 (m, 2H, 2 × H3), 3.69 (s, 3H,

CH3O), 3.81 (s, 3H, CH3O), 4.81 (dd, J = 4.9 Hz, 1H, H4), 4.90 (br, 2H, 2 × OH), 5.51

(dd, J = 5.6, 6.4 Hz, 1H, H2), 6.28 (dd, J = 2.6, 8.3 Hz, 1H, H6), 6.30 (d, J = 1.9 Hz, 1H,

H5’’), 6.44 (d, J = 2.6 Hz, 1H, H8), 6.57 (d, J = 1.9 Hz, 1H, H7’’), 6.67 (d, J = 8.3 Hz,

1H, H5), 6.81 (d, J = 8.7 Hz, 2H, H3’, H5’), 7.26 (d, J = 8.7 Hz, 2H, H2’, H6’), 7.28 (d, J

= 8.3 Hz, 2H, H2’’’, H6’’’), 7.48 (d, J = 8.3 Hz, 2H, H3’’’, H5’’’); 13C NMR (75.6 MHz,

CDCl3): 30.8 (C4), 35.6 (C3), 55.2 (CH3O), 55.7 (CH3O), 74.6 (C2), 88.3 (ArCH), 94.5

(ArCH), 103.6 (ArCH), 108.3 (ArCH), 113.7 (ArC), 115.3 (ArCH), 116.2 (ArC), 121.0

(ArC), 127.4 (ArCH), 127.8 (ArCH), 130.3 (ArC), 130.7 (ArCH), 130.8 (ArC), 131.6

(ArCH), 131.9 (ArC), 133.3 (ArC), 154.1 (ArC), 154.2 (ArC), 154.3 (ArC), 155.2 (ArC),

+ 155.7 (ArC), 156.0 (ArC); HRMS (TOF-ESI) m/z Calcd. for C31H25BrO6Na (M + Na)

595.0732 (Br = 79) and 597.0712 (Br = 81). Found 595.0662 (Br = 79), 597.0639 (Br =

79).

4’,7-Diacetoxy-4-(4’,7-dimethoxyisoflav-3-ene-6-yl)flavan (143)

The title compound was synthesized following the procedure for flavans 132 and 134 using flavanol 128 (500 mg, 1.46 mmol), dimethoxyflavene 112 (392 mg, 1.62 mmol), dichloromethane (25 mL) and BF3·OEt2 (11 drops). Chromatography (SiO2, 30% ethyl acetate/hexane) gave the title compound as a 1:1 mixture of cis/trans isomers (600 mg,

69%). TLC analysis using several solvent systems failed to achieve separation between 181 the two isomers. The mixture was rechromatographed on a 20 inch long silica column.

The compound was collected in 100 small fractions. The initial fractions gave almost pure trans compound 143 (140 mg). This was followed by mixtures of both isomers.

trans isomer (143) O Off-white solid. M.p. 146-149 °C (from OMe

- MeO MeOH); UV (MeOH): max 210 ( 52223 cm

1M-1), 265 ( 23045 cm-1M-1), 349 ( 35948

-1 -1 AcO O cm M ) nm; IR (KBr): max 1766, 1620, 1515, OAc 1490, 1215, 1181, 1144, 1108, 1032, 1015

-1 1 cm ; H NMR (300 MHz, CDCl3): 2.22 (m, 1H, H3), 2.23 (m, 1H, H3), 2.28 (s, 3H,

CH3COO), 2.29 (s, 3H, CH3COO), 3.80 (s, 3H, CH3O), 3.84 (s, 3H, CH3O), 4.49 (m, 1H,

H4), 4.95 (dd, J = 3.6, 10.6 Hz, 1H, H2), 5.10 (s, 2H, 2 × H2’’), 6.45 and 6.47 (2 × s,

2H, H5’’, H8’’), 6.58 (s, 1H, H4’’), 6.65 (dd, J = 2.6, 8.7 Hz, 1H, H6), 6.75 (d, J = 2.6 Hz,

1H, H8), 6.87 and (d, J = 9.1 Hz, 2H, H3’’’, H5’’’), 6.99 (d, J = 8.7 Hz, 1H, H5), 7.05 (d,

J = 8.7 Hz, 2H, H3’, H5’), 7.31 (d, J = 9.1 Hz, 2H, H2’’’, H6’’’), 7.34 (d, J = 8.7 Hz, 2H,

13 H2’, H6’); C NMR (75.6 MHz, CDCl3): 20.98 and 21.04 (2 × CH3COO), 33.7 (C3),

36.0 (C4), 55.2 and 55.4 (2 × CH3O), 67.2 (C2’’), 73.3 (C2), 98.7, 102.8, 109.9, 114.1,

115.1, 118.1, 120.8, 121.4, 125.6, 126.9, 127.3, 127.9, 128.4, 129.3, 131.2, 138.7,

138.8, 150.1, 150.1, 156.3, 156.8, 159.1, 169.2 (COO), 169.3 (COO); HRMS (TOF-ESI)

+ m/z Calcd. for C36H32O8Na (M + Na) 615.1995. Found 615.1800; Anal. Calcd. for

C36H32O8: C, 72.96; H, 5.44. Found: C, 72.43; H, 5.54.

182 trans-4’,7-Dihydroxy-4-(4’,7-dimethoxyisoflav-3-ene-6-yl)flavan (144)

The title compound was synthesized following O the procedure for isoflavan 79 using OMe MeO compound 143 (100 mg, 0.16 mmol).

Compound 144 was obtained as a white solid

(80 mg, 92%). M.p. 226-228 °C; UV (MeOH): HO O

-1 -1 - OH max 212 ( 43878 cm M ), 255 ( 20375 cm

1 -1 -1 -1 M ), 334 ( 20745 cm M ) nm; IR (KBr): max 3428 (br), 1616, 1513, 1445, 1248,

-1 1 1159, 1108 cm ; H NMR (300 MHz, acetone-d6): 2.30 (m, 2H, 2 × H3), 3.75 (s, 3H,

CH3O), 3.84 (s, 3H, CH3O), 4.60 (m, 1H, H4), 5.07 (s, 2H, 2 × H2’’), 5.10 (m, 1H, H2),

6.30-6.70 (m, 6H, H5, H6, H8, H4’’, H5’’, H8’’), 6.83 (d, J = 8.7 Hz, 2H, H3’, H5’), 6.90

(d, J = 8.7 Hz, 2H, H3’’’, H5’’’), 7.31 (d, J = 8.7 Hz, 2H, H2’, H6’), 7.39 (d, J = 8.7 Hz,

13 2H, H2’’’, H6’’’); C NMR (75.6 MHz, acetone-d6): 33.4 (C4), 36.1 (C3), 54.6 and 55.3

(2 × CH3O), 66.7 (C2’’), 78.0 (C2), 98.6 ,103.0, 108.1, 108.6, 114.4, 115.1, 116.1,

117.2, 117.7, 125.6, 127.5, 127.6, 128.2, 129.2, 132.8, 152.8, 156.5, 157.0, 157.1,

+ 158.1, 159.28, 159.33; HRMS (TOF-ESI) m/z Calcd. for C32H28O6Na (M + Na)

531.1784. Found 531.1789.

4’,7-Diacetoxy-4-(4,6-dimethoxy-2,3-diphenylindol-7-yl)flavan (145)

The title compound was synthesized following the procedure for flavans 132 and 134 using flavanol 128 (500 mg, 1.42 mmol), diphenylindole 106 (480 mg, 1.45 mmol), dichloromethane (50 mL) and BF3·OEt2 (40 drops). Chromatography (SiO2, 25% ethyl acetate/hexane) gave the title compound as a 1:1 mixture of cis/trans isomers (700 mg,

73%). The mixture was rechromatographed on a 20 inch long silica column. The compound was divided into 30 small fractions. The initial fractions gave predominantly trans compound 145. Remaining fractions were all 1:1 mixture of cis/trans isomers

183 trans isomer (145)

Off-white solid. M.p. 227-230 C; IR (KBr): max 3454, OMe 2955, 2924, 1764, 1600, 1494, 1209, 1142, 1104 cm-1;

1 H NMR (300 MHz, CDCl3): 2.28 (s, 3H, CH3COO), MeO N H 2.32 (s, 3H, CH3COO), 2.44 (m, 2H, 2 × H3), 3.68 (s,

3H, CH3O), 3.90 (s, 3H, CH3O), 4.78 (m, 1H, H4), 5.19 AcO O

(dd, J = 5.3, 6.4 Hz, 1H, H2), 6.34 (s, 1H, H5’’), 6.73 OAc

(dd, J = 2.3, 8.3 Hz, 1H, H6), 6.87-7.39 (m, 16H, aromatic, NH); 13C NMR (75.6 MHz,

CDCl3): 21.0 (2 × CH3COO), 31.5 (C4), 36.8 (C3), 55.4 (CH3O), 56.7 (CH3O), 77.1

(C2), 89.5 (C5’’), 106.9, 110.6 (ArCH), 114.5 (ArC), 114.6 (ArCH), 121.4 (ArCH), 125.8

(ArCH), 126.6 (ArCH), 127.1 (ArCH), 127.2 (ArCH), 128.4 (ArC), 131.3 (ArCH), 132.2

(ArC), 132.3 (ArC), 136.1 (ArC), 136.5 (ArC), 138.5 (ArC), 150.1 (ArC), 150.7 (ArC),

153.6 (ArC), 153.8 (ArC), 155.4 (ArC), 169.0 (COO), 169.3 (COO); MS (TOF-ESI) m/z

+ Calcd. for C41H35NO7Na (M + Na) 676.2311. Found 676.2023; Anal. Calcd. for

C41H35NO7: C, 75.33; H, 5.40; N, 2.14. Found: C, 75.55; H, 5.49; N, 2.25.

trans-4’,7-Dihydroxy-4-(4,6-dimethoxy-2,3-diphenylindol-7-yl)flavan (146)

The title compound was synthesized following the procedure for isoflavan 79 using flavan 145 (400 mg, OMe

0.61 mmol). Compound 146 was obtained as a white MeO N solid (331 mg, 95%). M.p. 256-258 C (from MeOH); IR H

(KBr): 3439 , 2919, 1616, 1599, 1504, 1261, 1152, max HO O -1 1 1104 cm ; H NMR (300 MHz, CDCl3): 2.41 (m, 2H, 2 OH

× H3), 3.65 (s, 3H, CH3O), 3.97 (s, 3H, CH3O), 4.75 (m, 1H, H4), 5.19 (dd, J = 5.3, 6.4

Hz, 1H, H2), 6.33 (s, 1H, H5’’), 6.47 (dd, J = 2.3, 8.3 Hz, 1H, H6), 6.60 (d, J = 2.3 Hz,

1H, H8), 6.80-7.39 (m, 16H, aromatic, NH); MS (TOF-ESI) m/z Calcd. for C37H31NO5Na

184 + (M + Na) 592.2094. Found 592.2007; Anal. Calcd. for C37H31NO5: C, 78.01; H, 5.49; N,

2.46. Found: C, 78.10; H, 5.57; N, 2.53.

4’,7-Diacetoxyflav-3-ene (148)

A mixture of p-toluenesulfonic acid (120 mg) and toluene (750 mL) was refluxed for 45 min with Dean- AcO O Stark apparatus to remove traces of water. OAc Diacetoxyflavan-4-ol 128 (1.8 g, 5.26 mmol) was added and the heating was continued for a further 2 h. The reaction mixture was cooled to r.t. and washed with water (200 mL

× 2). The organic layer was dried over anhydrous sodium sulfate and the solvent was removed under vacuum. Chromatography (SiO2, 25% ethyl acetate/hexane) afforded flavene 148 (1.2 g, 70%) as colourless crystals. M.p. 110-112 C (from MeOH); UV

-1 -1 -1 -1 -1 -1 (MeOH): max 228 ( 40168 cm M ), 269 ( 13620 cm M ), 306 ( 12400 cm M ) nm;

-1 1 IR (KBr): max 1756, 1497, 1372, 1218, 1202, 1191, 1139, 1115, 910 cm ; H NMR (300

MHz, CDCl3): 2.25 (s, 3H, CH3COO), 2.29 (s, 3H, CH3COO), 5.75 (dd, J = 3.4, 9.8

Hz, 1H, H3), 5.91 (dd, J = 1.1, 3.4 Hz, 1H, H2), 6.51 (dd, J = 1.1, 9.8 Hz, 1H, H4), 6.53

(d, J = 2.3 Hz, H8), 6.61 (dd, J = 2.3, 7.9 Hz, 1H, H6), 6.98 (d, J = 7.9 Hz, 1H, H5), 7.09

(d, J = 8.7 Hz, 2H, H3’, H5’), 7.44 (d, J = 8.7 Hz, 2H, H2’, H6’); 13C NMR (75.6 MHz,

CDCl3): 21.0 (2 × CH3COO), 76.6 (C2), 109.6 (ArCH), 114.2 (ArCH), 118.9 (ArC),

121.7 (ArCH), 123.4 (ArCH), 123.9 (ArCH), 126.9 (ArCH), 128.2 (ArCH), 138.0 (ArC),

150.6 (ArC), 151.3 (ArC), 153.7 (ArC), 169.0 and 169.3 (2 × COO); HRMS (ESI) m/z

+ Calcd. for C19H16O5Na (M + Na) , 347.0890. Found 347.0893; Anal. Calcd. for

C19H16O5: C, 70.36; H, 4.97. Found: C, 70.55; H, 4.97.

185 6a,12a-Dihydro-3,10-dihydroxy-6-(4’-hydroxyphenyl)-7-[(1E)-2-(4’’- hydroxyphenylethenyl)]-6H,7H-[1]benzopyrano[4, 3-b][1]benzopyran (149)

To a suspension of flavene 148 (350 mg, 1.08 mmol) in 2 1 OH 11 H methanol (35 mL) was added hydrochloric acid (10M, 2.7 HO O 4 12a H6a H mL). The mixture was stirred under an argon atmosphere 9 O 78 H 6 for 6 h. Methanol was evaporated off at 30 °C under ß 2' 3' 2'' vacuum and the residue was taken up in ethyl acetate 3'' OH (50 mL). The organic layer was washed with water (25 OH mL × 2), dried over anhydrous sodium sulfate and concentrated under vacuum.

Chromatography (SiO2, 70% ethyl acetate/hexane) gave dimer 149 as a light red solid

(240 mg, 92%). M.p. 190-192 C (ethyl acetate/hexane); UV (MeOH): max 206 ( 94500

-1 -1 -1 -1 cm M ), 265 ( 26060 cm M ) nm; IR (KBr): max 3407, 2958, 1616, 1511, 1458, 1230,

-1 1 1159, 1119, 1017, 836 cm . H NMR (acetone-d6, 600 MHz): 2.51 (ddd, J = 2.1, 2.4,

10.9 Hz, 1H, H6a), 3.11 (dd, J = 2.1, 6.7 Hz, 1H, H7), 4.89 (d, J = 10.9 Hz, 1H, H6),

5.08 (d, J = 2.4 Hz, 1H, H12a), 6.02 (d, J = 15.7 Hz, 1H, H ), 6.24 (dd, J = 6.7, 15.7 Hz,

1H, H ), 6.33 (d, J = 2.3 Hz, 1H, H4), 6.33 (d, J = 2.4 Hz, 1H, H11), 6.41 (dd, J = 2.4,

8.3 Hz, 1H, H9), 6.48 (dd, J = 2.3, 8.3 Hz, 1H, H2), 6.74 (d, J = 8.6 Hz, 2H, H3’’, H5’’),

6.77 (d, J = 8.3 Hz, 1H, H8), 6.89 (d, J = 8.5 Hz, 2H, H3’, H5’), 7.19 (d, J = 8.6 Hz, 2H,

H2’’, H6’’), 7.20 (d, J = 8.5 Hz, 2H, H2’, H6’), 7.25 (d, J = 8.3 Hz, 1H, H1), 8.31 (brs, 2H,

13 2 × OH), 8.52 (brs, 2H, 2 × OH); C NMR (acetone-d6, 150 MHz): 38.7 (C7), 41.6

(C6a), 67.6 (C12a), 77.0 (C6), 102.9 (C11), 103.2 (C4), 108.6 (C2), 109.1 (C9), 112.2

(C7a), 113.7 (C12b), (2 × 115.7) (C3’, C5’, C3’’, C5’’), 127.9 (C2’’, C6’’), 129.2 (C1’’),

129.4 (C2’, C6’), 130.3 (C1’), 130.9 (C ), 131.3 (C8), 131.5 (C ), 132.0 (C1), 154.1

(C11a), 157.3 (C4’’), 156.5 (C4a), 157.9 (C10), 158.1 (C4’), 159.7 (C3); HRMS (ESI)

+ m/z Calcd. for C30H24O6Na (M + Na) , 503.1465. Found 503.1478.

186 6a,12a-Dihydro-3,10-diacetoxy-6-(4’-acetoxyphenyl)-7-[(1E)-2-(4’’- acetoxyphenylethenyl)]-6H,7H-1]benzo pyrano[4, 3-b][1]benzopyran (150)

A mixture of compound 149 (50 mg, 0.104 mmol), OAc H acetic anhydride (1 mL) and pyridine (0.5 mL) was AcO O H H O heated at 100 °C for 6 h. The reaction mixture was H cooled to r.t. and poured into cold water (50 mL). The white solid was filtered, washed with water and dried OAc

(50 mg, 74%). M.p 140-142 C (from ethyl OAc

-1 -1 -1 -1 acetate/hexane); UV (MeOH): max 204.9 ( 67705 cm M ), 258 ( 19680 cm M ) nm;

-1 1 IR (KBr): max 2923, 1762, 1616, 1498, 1369, 1209, 1144, 1115, 1015 cm ; H NMR

(CDCl3, 300 MHz): 2.26 (s, 3H, CH3COO), 2.28 (s, 6H, 2 × CH3COO), 2.31 (s, 3H,

CH3COO), 2.49 (ddd, J = 2.3, 3.0, 9.8 Hz, 1H, H6a), 3.24 (dd, J = 2.3, 6.4 Hz, 1H, H7),

5.08 (d, J = 3.0 Hz, 1H, H12a), 5.08 (d, J = 9.8 Hz, 1H, H6), 6.07 (d, J = 15.8 Hz, 1H,

H), 6.16 (dd, J = 6.4, 15.8 Hz, 1H, H), 6.67 (dd, J = 2.3, 8.3 Hz, 1H, H2), 6.69 (d, J =

2.3 Hz, 1H, H9), 6.69 (d, J = 2.3 Hz, 2H, H4, H11), 6.73 (dd, J = 2.3, 8.3 Hz, 1H, H9),

6.96 (d, J = 8.3 Hz, 1H, H8), 6.99 (d, J = 8.6 Hz, 2H, H3’’, H5’’), 7.14 (d, J = 8.3 Hz, 2H,

H3’, H5’), 7.28 (d, J = 8.6 Hz, 2H, H2’’, H6’’), 7.31 (d, J = 8.3 Hz, 2H, H2’, H6’), 7.39 (d,

13 J = 8.3 Hz, 1H, H1); C NMR (75.6 MHz, CDCl3): 21.0 (4 × CH3COO), 37.9 (C7),

41.0 (C6a), 66.9 (C12a), 76.2 (C6), 110.24 (ArCH), 110.15 (ArCH), 114.3 (ArCH),

114.5 (ArCH), 117.6 (ArC), 118.4 (ArC), 121.6 (ArCH), 121.8 (ArCH), 127.2 (ArCH),

128.2 (ArCH), 130.8 (ArCH), 131.0 (ArCH), 131.5 (ArCH), 132.3 (ArCH), 134.2 (ArC),

135.8 (ArC), 150.0 (ArC), 150.6 (ArC), 150.9 (ArC), 152.2 (ArC), 153.0 (ArC), 155.1

(ArC), 169.1, 169.1, 169.1 and 169.2 (4 × COO); Anal. Calcd. for C38H32O10: C, 70.36;

H, 4.97. Found: C, 70.41; H, 5.27.

187 2’,4,5’-Trihydroxychalcone (156) O To a mixture of 2’,5’-dihydroxyacetophenone 155 (1.36 HO g, 8.94 mmol), 4-hydroxybenzaldehyde 124 (1.12 g, 9.1 OH mmol) and ethanol (1.12 mL) was added KOH solution OH

(8 mL, 60% w/w). The dark mixture was heated at 100 °C for 2 h. TLC analysis showed formation of two products. The reaction mixture was cooled to r.t. and poured into ice cold water (30 mL) and acidified to pH 5 with conc. hydrochloric acid (ca 13 mL). The solid was filtered, washed with water (50 mL) and dried at 80 °C. Chromatography

(SiO2, 40% ethyl acetate/hexane) gave chalcone 156 (1.10 g, 48%) as a yellow solid.

116 -1 -1 M.p. 228-230 C, lit. 223-235 C; UV (MeOH): max 203 ( 25664 cm M ), 243 (

-1 -1 -1 -1 16579 cm M ), 361 ( 26541 cm M ) nm; IR (KBr): max 3358, 3174, 1705, 1636,

1599, 1583, 1541, 1516, 1437, 1369, 1321, 1289, 1268, 1186, 1168, 821 cm-1; 1H NMR

(300 MHz, acetone-d6): 6.79 (d, J = 8.6 Hz, 1H, H3’), 6.91 (d, J = 8.6 Hz, 2H, H3, H5),

7.05 (dd, J = 3.0, 8.6 Hz, 1H, H4’), 7.52 (d, J = 3.0 Hz, 1H, H6’), 7.68 (d, J = 15.1 Hz,

1H, H), 7.72 (d, J = 8.6 Hz, 2H, H2, H6), 7.84 (d, J = 15.1 Hz, 1H, H), 8.03 (s, 1H,

OH), 8.98 (s, 1H, OH), 12.40 (s, 1H, OH).

Further elution gave compound 157 as a pale yellow solid (350 mg, 20%)

1,5-Bis(2,5-dihydroxyphenyl)-3-(4-hydroxyphenyl)pentane-1,5-dione (157)

M.p. 179-181 C; UV (MeOH): 204 ( 31937 cm- max OH HO 1M-1) sh, 224 ( 39912 cm-1M-1), 258 ( 17616 cm-1M- HO O O OH 1 -1 -1 ), 366 ( 9803 cm M ) nm; IR (KBr): max 3404 (br),

1642, 1629, 1609, 1485, 1232, 1198, 1176, 999, 792

-1 1 cm ; H NMR (300 MHz, acetone-d6): 3.42 (dd, J = OH

7.5, 16.6 Hz, 2H), 3.52 (dd, J = 6.4, 16.6 Hz, 2H), 3.99 (dt, J = 6.4, 7.5 Hz, 1H), 6.71 (d,

J = 8.6 Hz, 2H), 6.76 (d, J = 9.0 Hz, 2H), 7.06 (dd, J = 3.0, 9.0 Hz, 2H), 7.21 (d, J = 8.6

188 Hz, 2H), 7.40 (d, J = 3.0 Hz, 2H), 8.07 (s, 2H), 8.08 (s, 1H), 11.65 (s, 2H); 13C NMR

(75.6 MHz, acetone-d6): 36.2 (CH), 44.6 (2 × CH2), 114.7 (ArCH), 115.0 (ArCH),

118.3 (ArCH), 119.3 (ArC), 124.7 (ArCH), 128.5 (ArCH), 134.1 (ArC), 149.3 (ArC),

154.9 (ArC), 155.8 (ArC), 205.1 (C=O); HRMS (ESI) m/z Calcd. for C23H20O7Na (M +

+ Na) , 431.1101. Found 431.1099; Anal. Calcd. for C23H20O7: C, 67.64; H, 4.94. Found:

C, 67.25; H, 4.78.

4’,6-Dihydroxyflavanone (158)

A mixture of chalcone 156 (2.5 g, 9.76 mmol), methanol O HO (125 mL) and conc. hydrochloric acid (10 mL) was refluxed for 48 h. The reaction mixture was O OH concentrated under vacuum to 20 mL and diluted with water (100 mL). The product was filtered, washed with water and dried. The flavanone

158 was obtained as a pale yellow solid (2.3 g, 92%). M.p. 235-237 C, lit.122 230 °C;

-1 -1 -1 -1 -1 -1 UV (MeOH): max 204 ( 18324 cm M ), 227 ( 27054 cm M ), 253 ( 8580 cm M )

-1 -1 sh, 357 ( 4722 cm M ) nm; IR (KBr): max 3500-2500 (br), 3331, 1669, 1617, 1476,

-1 1 1374, 1318, 1214, 1135, 837, 777 cm ; H NMR (300 MHz, acetone-d6): 2.71 (dd, J =

2.6, 17.0 Hz, 1H, H3), 3.07 (dd, J = 13.2, 17.0 Hz, 1H, H3), 5.40 (dd, J = 2.6, 13.2 Hz,

1H, H2), 6.88 (d, J = 6.8 Hz, 2H, H3’, H5’), 6.89 (d, J = 8.6, 1H, H8), 7.07 (dd, J = 3.4,

8.6 Hz, 1H, H7), 7.23 (d, J = 3.4 Hz, 1H, H5), 7.38 (d, J = 6.8 Hz, 2H, H2’, H6’), 8.34 (s,

13 1H, OH), 8.51 (s, 1H, OH); C NMR (75.6 MHz, acetone-d6): 44.0 (C3), 79.3 (C2),

110.2 (ArCH), 115.1 (ArCH), 118.9 (ArCH), 121.1 (ArC), 124.1 (ArCH), 127.9 (ArCH),

130.4 (ArC), 151.5 (ArC), 155.6 (ArC), 157.6 (ArC), 191.4 (C4).

189 4’,6-Diacetoxyflavanone (159) O A mixture of flavanone 158 (2.3 g, 9.0 mmol), acetic AcO anhydride (14 mL) and pyridine (2.3 mL) was heated O at 100 °C for 1 h. The reaction mixture was cooled to OAc r.t. and maintained there for 2 h. The precipitated white solid was filtered and washed with methanol-water (50 mL, 1:1) and dried to give the diacetoxyflavanone 159 as white

- crystals (2.0 g, 65%). M.p. 181-183 C (from MeOH); UV (MeOH): max 247 ( 9990 cm

1 -1 -1 -1 M ), 326 ( 3995 cm M ) nm; IR (KBr): max 1768, 1748, 1683, 1613, 1485, 1365,

-1 1 1280, 1226, 1197, 1181, 1013, 920, 907 cm ; H NMR (300 MHz, CDCl3): 2.29 (s,

3H, CH3COO), 2.31 (s, 3H, CH3COO), 2.88 (dd, J = 3.0, 16.9 Hz, 1H, H3), 3.05 (dd, J =

13.2, 16.9 Hz, 1H, H3), 5.47 (dd, J = 3.0, 13.2 Hz, 1H, H2), 7.06 (d, J = 8.7 Hz, 1H,

H8), 7.16 (d, J = 8.7 Hz, 2H, H3’, H5’), 7.23 (dd, J = 2.6, 8.7 Hz, 1H, H7), 7.49 (d, J =

13 8.7 Hz, 2H, H2’, H6’), 7.61 (d, J = 2.6 Hz, 1H, H5); C NMR (75.6 MHz, CDCl3): 20.8

(CH3COO), 21.0 (CH3COO), 44.3 (C3), 79.2 (C2), 119.1 (ArCH), 119.2 (ArCH), 121.1

(ArCH), 122.0 (ArCH), 127.2 (ArCH), 129.8 (ArCH), 135.9 (ArC), 144.8 (ArC), 150.8

(ArC), 158.9 (ArC), 169.2 (COO), 169.4 (COO), 190.8 (C4); HRMS (ESI) m/z Calcd. for

+ C19H16O6Na (M + Na) , 363.0840. Found 363.0834; Anal. Calcd. for C19H16O6: C, 67.05;

H, 4.73. Found: C, 67.25; H, 4.78.

cis-4’,6-Diacetoxyflavan-4-ol (160)

To a solution of diacetoxyflavanone 159 (2.0 g, 5.88 OH AcO mmol) in THF (80 mL) was added 10% palladium on O charcoal (200 mg). The mixture was hydrogenated at OAc r.t. for 48 h. The catalyst was filtered off through Celite® and the bed was washed with dichloromethane (25 mL × 2). Evaporation of the filtrate under vacuum afforded flavanol 160 as a white solid (2.0 g, 99%). M.p. 142-143 C (from MeOH); UV (MeOH):

-1 -1 -1 -1 max 208 ( 21631 cm M ), 281 ( 2528 cm M ) nm; IR (KBr): max 3464, 1755, 1483,

190 -1 1 1367, 1223, 1395, 1018, 898, 836 cm ; H NMR (300 MHz, CDCl3): 2.04 (ddd, J =

4.5, 11.7, 13.2 Hz, 1H, H3), 2.27 (s, 3H, CH3COO), 2.30 (s, 3H, CH3COO), 2.44 (ddd, J

= 1.9, 6.0, 13.2 Hz, 1H, H3), 5.01 (dd, J = 4.5, 6.0 Hz, 1H, H4), 5.13 (dd, J = 1.9, 11.7

Hz, 1H, H2), 6.84 (d, J = 8.3 Hz, 1H, H8), 6.89 (dd, J = 2.3, 8.3 Hz, 1H, H7), 7.11 (d, J

= 8.7 Hz, 2H, H3’, H5’), 7.22 (d, J = 2.3 Hz, 1H, H5), 7.41 (d, J = 8.7 Hz, 2H, H2’, H6’);

13 C NMR (75.6 MHz, CDCl3): 20.9 (CH3COO), 21.0 (CH3COO), 39.6 (C3), 65.5 (C4),

76.5 (C2), 117.3 (ArCH), 119.7 (ArCH), 121.7 (ArCH), 122.2 (ArCH), 126.5 (ArC), 127.2

(ArCH), 137.8 (ArC), 144.3 (ArC), 150.4 (ArC), 151.9 (ArC), 169.3 (COO), 170.0

+ (COO); HRMS (ESI) m/z Calcd. for C19H18O6Na (M + Na) , 365.0996. Found 365.0999;

Anal. Calcd. for C19H18O6: C, 66.65; H, 5.29. Found: C, 67.14; H, 5.37.

4’,6-Diacetoxyflav-3-ene (161)

A mixture of p-toluenesulfonic acid monohydrate (66 AcO mg, 0.35 mmol) and toluene (425 mL) was refluxed for O 45 min with a Dean-Stark apparatus to remove traces OAc of water. Flavanol 160 (1.0 g, 2.92 mmol) was added and the heating was continued further for 1.5 h. The reaction mixture was cooled to r.t. and washed with saturated sodium bicarbonate solution (100 mL). The organic layer was dried over anhydrous sodium sulfate and the solvent was evaporated off under vacuum. Chromatography

(SiO2, 25% ethyl acetate/hexane) gave diacetoxyflavene 161 as white crystals (0.9 g,

-1 -1 -1 -1 95%). M.p. 97-99 C; UV (MeOH): max 207 ( 24232 cm M ), 227 ( 31416 cm M ),

-1 -1 -1 -1 263 ( 4020 cm M ), 314 ( 2957 cm M ) nm; IR (KBr): max 3064, 1752, 1743, 1483,

-1 1 1370, 1207, 1193, 1165, 909 cm ; H NMR (300 MHz, CDCl3): 2.26 (s, 3H,

CH3COO), 2.28 (s, 3H, CH3COO), 5.80 (dd, J = 3.4, 10.1 Hz, 1H, H3), 5.90 (dd, J = 1.9,

3.4 Hz, 1H, H2), 6.48 (dd, J = 1.9, 10.1 Hz, 1H, H4), 6.75 (d, J = 8.7 Hz, 1H, H8), 6.76

(d, J = 3.0 Hz, 1H, H5), 6.81 (dd, J = 3.0, 8.7 Hz, 1H, H7), 7.09 (d, J = 8.7 Hz, 2H, H3’,

13 H5’), 7.45 (d, J = 8.7 Hz, 2H, H2’, H6’); C NMR (75.6 MHz, CDCl3): 20.9 (CH3COO),

21.0 (CH3COO), 76.6 (C2), 116.5 (ArCH), 119.3 (ArCH), 121.7 (ArCH), 121.7 (ArC), 191 122.0 (ArCH), 123.6 (ArCH), 125.4 (ArCH), 128.2 (ArCH), 137.9 (ArC), 144.4 (ArC),

150.4 (ArC), 150.6 (ArC), 169.2 (COO), 169.6 (COO); HRMS (ESI) m/z Calcd. for

+ C19H16O5Na (M + Na) , 347.0890. Found 347.0893; Anal. Calcd. for C19H16O5: C, 70.36;

H, 4.97. Found: C, 70.11; H, 5.10.

4’,6-Dihydroxyflav-3-ene (154)

To a suspension of diacetoxyflavene 161 (100 mg, 0.3 HO mmol) in methanol (5 mL) was added KOH solution O

(1M, 25 drops). The mixture was stirred under an argon OH atmosphere for 1 h. The reaction mixture was neutralized by adding acetic acid (1M, 25 drops). Water (25 mL) was added and the mixture was extracted with ethyl acetate (25 mL × 3). The combined organic extract was washed with saturated sodium bicarbonate solution (25 mL), dried over anhydrous sodium sulfate and evaporated under vacuum.

The crude product was purified by preparative thin layer chromatography (SiO2, 50% ethyl acetate/hexane). The dihydroxyflavene 154 was obtained as a pink solid (35 mg,

-1 -1 -1 -1 47%). M.p. 140-142 C; UV (MeOH): max 204 ( 28408 cm M ), 226 ( 27401 cm M ),

-1 -1 -1 -1 271 ( 6050 cm M ) sh, 330 ( 3865 cm M ) nm; IR (KBr): max 3656-3002 (br), 1517,

-1 1 1486, 1278, 1250, 1213, 1033, 836, 775 cm ; H NMR (300 MHz, acetone-d6): 5.71

(dd, J = 1.5, 3.4 Hz, 1H, H2), 5.85 (dd, J = 3.4, 9.8 Hz, 1H, H3), 6.55 (m, 4H, H4, H5,

H7, H8), 6.79 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.26 (d, J = 8.6 Hz, 2H, H2’, H6’), 8.15 (br,

13 2H, 2 × OH); C NMR (75.6 MHz, acetone-d6): 76.1 (C2), 112.7 (ArCH), 115.0

(ArCH), 115.4 (ArCH), 116.1 (ArCH), 123.7 (ArCH), 126.0 (ArCH), 128.5 (ArCH), 131.8

(ArC), 146.1 (ArC), 151.4 (ArC), 157.4 (ArC); HRMS (ESI) m/z Calcd. for C15H12O3Na

+ (M + Na) , 263.0681. Found 263.0681; Anal. Calcd. for C15H12O3: C, 74.99; H, 5.03.

Found: C, 74.86; H, 5.14.

192 2’-Hydroxy-6’-(tetrahydropyranyl-2-oxy)acetophenone (168)126 p-Toluenesulfonic acid (30 mg, 0.15 mmol) was added to a mixture of acetophenone 165 (3.0 g, 19.86 mmol), 3,4-dihydro-2H-pyran (10 OO O mL) and dry THF (15 mL). The mixture was stirred under an argon atmosphere overnight. The reaction mixture was poured into OH saturated sodium bicarbonate solution (50 mL) and stirred for 5 min. Hexane (100 mL) was added and the layers were separated. The organic layer was washed with NaOH solution (2M, 50 mL × 2). The pH of the aqueous layer was adjusted to 8 using 1M hydrochloric acid and again the product was extracted with hexane (50 mL × 3), dried over anhydrous sodium sulfate and the solvent was partially removed under vacuum.

The solution was kept in the refrigerator overnight and filtered. The protected acetophenone 168 was obtained as pale yellow crystals (2.6 g, 55%). 1H NMR (300

MHz, acetone-d6): 1.70-1.90 (m, 6H, 3 × CH2), 2.71 (s, 3H, CH3CO), 3.72 (m, 2H,

OCH2), 5.50 (m, 1H, CH), 6.51 and 6.60 (2 × d, J = 8.2 Hz, 2H, H3’, H5’), 7.32 (t, J =

13 8.2 Hz, 1H, H4’), 13.14 (s, 1H, OH); C NMR (75.6 MHz, acetone-d6): 19.0 (CH2),

24.9 (CH2), 30.2 (CH3), 33.6 (CH2), 62.2 (CH2), 97.3 (CH), 104.6 (ArCH), 111.2 (ArC),

111.7 (ArCH), 136.0 (ArCH), 159.0 (ArC), 164.3 (ArC), 204.9 (C=O).

4-(Tetrahydro-2-pyranoxy)benzaldehyde (169)278 p-Toluenesulfonic acid (30 mg, 0.15 mmol) was added to a solution of 4- CHO hydroxybenzaldehyde 124 (2.4 g, 19.67 mmol) in 3,4-dihydro-2H-pyran

(10 mL) and dry THF (15 mL). The mixture was stirred under an argon O atmosphere overnight. The reaction was quenched by pouring into O saturated sodium bicarbonate solution (25 mL) followed by stirring for 5 min. The organic layer was separated, dried over anhydrous sodium sulfate and concentrated under vacuum at r.t. Chromatography (SiO2, 33% dichloromethane/hexane) gave

1 aldehyde 169 as a yellowish oil (3.2 g, 80%). H NMR (300 MHz, CDCl3): 1.37 and

1.66 (m, 6H, 3 × CH2), 3.36 and 3.57 (m, 2H, OCH2), 5.27 (t, J = 2.8 Hz, 1H, CH), 6.90

193 (d, J = 8.8 Hz, 2H, H3, H5), 7.56 (d, J = 8.8 Hz, 2H, H2, H6), 9.60 (s, 1H, CHO); 13C

NMR (75.6 MHz, CDCl3): 17.7 (CH2), 24.3 (CH2), 29.3 (CH2), 61.2 (OCH2), 95.4 (CH),

116.0 (ArCH), 129.7 (ArC), 131.0 (ArCH), 161.5 (ArC), 190.1 (C=O).

2’,4,6’-Trihydroxychalcone (166)

To a solution of acetophenone 168 (0.77 g, 3.26 mmol) and OH O aldehyde 169 (0.73 g, 3.58 mmol) in absolute ethanol (3 mL) was added a solution of KOH (3.0 g) in water (2 mL). The OH mixture was stirred at ambient temperature overnight, OH poured into water (150 mL) and acidified to pH 5. The product was extracted with ethyl acetate (25 mL × 3), dried over sodium sulfate and evaporated under vacuum. The crude product (1.5 g) was dissolved in methanol (30 mL), hydrochloric acid (2M, 10 mL,) was added and the mixture was heated at 70 C for 30 min. The reaction was poured into water (150 mL) and extracted with ethyl acetate (25 mL × 4). The combined organic extract was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 50% ethyl acetate/hexane) gave chalcone 166 as orange needles (0.47 g, 56%). Mp: 214-216 C, lit.125 215-216 C; IR (KBr): 3363, 3235,

1632, 1581, 1511, 1499, 1453, 1205, 1169, 1009, 822, 746 cm-1; 1H NMR (300 MHz, acetone-d6): 6.44 (d, J = 8.3 Hz, 2H, H3’, H5’), 6.90 (d, J = 8.7 Hz, 2H, H3, H5), 7.25

(t, J = 8.3 Hz, 1H, H4’), 7.59 (d, J = 8.7 Hz, 2H, H2, H6), 7.80 (d, J = 15.5 Hz, 1H, H),

13 8.08 (d, J = 15.5 Hz, 1H, H), 8.99 (s, 1H, 4 OH), 11.55 (s, 2H, 2 × 2’ OH); C NMR

(75.6 MHz, acetone-d6): 107.6 (ArCH), 115.9 (ArCH), 124.2 (ArCH), 126.9 (ArC),

130.5 (ArCH), 135.7 (ArCH), 143.4 (ArCH), 160.0 (ArC), 162.1 (ArC), 194.3 (C=O).

194 4’,5-Dihydroxyflavanone (167) OH O A mixture of chalcone 166 (1.3 g, 5.07 mmol), sodium acetate (1.3 g, 15.8 mmol) and ethanol (26 mL) was refluxed O for 1 h. The reaction mixture was cooled to r.t., poured into OH water (100 mL) and acidified to pH 5 using 1M hydrochloric acid. The solid was filtered, washed with water and air dried to give flavanone 167 (1.2 g, 92%) as colourless

91 needles. M.p. 205-207 C (from MeOH), lit. 205-206 C; UV (MeOH): max 203 (

29762 cm-1M-1), 222 ( 25971 cm-1M-1), 270 ( 11897 cm-1M-1), 347 ( 4310 cm-1M-1)

- nm; IR (KBr): max 3415, 3257, 1632, 1618, 1460, 1371, 1218, 1209, 1057, 837, 714 cm

1 1 ; H NMR (300 MHz, acetone-d6): 2.83 (dd, J = 3.0, 17.0 Hz, 1H, H3), 3.29 (dd, J =

12.8, 17.0 Hz, 1H, H3), 5.52 (dd, J = 3.0, 12.8 Hz, 1H, H2), 6.47 (2 × d, J = 8.3 Hz, 2H,

H6, H8), 6.89 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.41 (d, J = 8.6 Hz, 2H, H2’, H6’), 7.43 (t, J

13 = 8.3 Hz, 1H, H7); C NMR (75.6 MHz, acetone-d6): 43.0 (C3), 78.9 (C2), 107.3

(ArCH), 107.9 (ArC), 108.7 (ArCH), 115.2 (ArCH), 128.0 (ArCH), 129.6 (ArC), 138.1

(ArCH), 157.8 (ArC), 161.9 (ArC), 162.0 (ArC), 199.0 (C4).

4’,5-Diacetoxyflavanone (171)

A mixture of flavanone 167 (1.2 g, 4.68 mmol), acetic OAc O anhydride (7.2 mL, 76.2 mmol) and pyridine (1.2 mL, 14.9 mmol) was heated with stirring at 100 °C for 2 h. The O reaction mixture was cooled to r.t. and poured over a OAc mixture of hydrochloric acid (2M, 50 mL) and ice (100.0 g). The mixture was stirred for

10 min and filtered. The solid was washed with water (50 mL) and air dried to give diacetoxyflavanone 171 as a white solid (1.5 g, 94%). M.p. 134-135 C (from MeOH),

124 -1 -1 -1 -1 lit. 114 C; UV (MeOH): max 215 ( 29035 cm M ), 253 ( 7827 cm M ), 319 (

-1 -1 3395 cm M ) nm; IR (KBr): max 1764, 1745, 1682, 1616, 1467, 1370, 1222, 1190,

-1 1 1046, 911 cm ; H NMR (300 MHz, CDCl3): 2.31 (s, 3H, CH3COO), 2.39 (s, 3H,

195 CH3COO), 2.78 (dd, J = 2.3, 16.6 Hz, 1H, H3), 3.04 (dd, J = 13.2, 16.6 Hz, 1H, H3),

5.48 (dd, J = 2.3, 13.2 Hz, 1H, H2), 6.70 (d, J = 7.9 Hz, 1H, H8) and 6.96 (d, J = 8.3 Hz,

1H, H6), 7.15 (d, J = 8.7 Hz, 2H, H3’, H5’), 7.48 (m, 3H, H7, H2’, H6’); 13C NMR (75.6

MHz, CDCl3): 21.0 (2 × CH3COO), 45.3 (C3), 78.7 (C2), 106.7 (ArC), 113.8 (ArC),

116.2 (ArCH), 122.0 (ArCH), 127.3 (ArCH), 135.8 (ArCH), 150.1 (ArC), 150.9 (ArC),

162.4 (ArC), 169.2 (ArC), 169.6 (COO), 172.7 (COO), 189.8 (C=O); Anal. Calcd. for

C19H16O6: C, 67.05; H, 4.73. Found: C, 67.18; H, 4.66.

trans-4’,5-Diacetoxyflavanol (172)

A suspension of diacetoxyflavanone 171 (900 mg, 2.64 OAc OH mmol) and methanol (40 mL) was stirred at r.t. for 10 min.

The mixture was cooled to -15 °C using an ice-salt bath O under an argon atmosphere and powdered sodium OAc borohydride (580 mg, 15.33 mmol) was added in portions over 15 min. The mixture was stirred at -15 to -10 °C for 1.5 h, then quenched by dropwise addition of glacial acetic acid (65 drops) over 15 min and poured into ice-water (200 mL). The solid was filtered and washed with water (50 mL). The title compound was obtained as a white solid (850

-1 -1 mg, 95%). M.p. >320 C (from acetone); UV (MeOH): max 210 ( 31064 cm M ), 226

-1 -1 -1 -1 ( 16386 cm M ), 280 ( 3656 cm M ) nm; IR (KBr): max 3230, 1757, 1697, 1593,

-1 1 1466, 1371, 1268, 1199, 1176, 1051, 1035, 916, 786 cm ; H NMR (300 MHz, CDCl3):

2.15 (m, 1H, H3), 2.13 (m, 1H, H3), 2.18 (s, 3H, CH3COO), 2.31 (s, 3H, CH3COO),

3.34 (dd, J = 2.3, 12.4 Hz, 1H, H2), 5.98 (t, J = 2.8 Hz, 1H, H4), 6.52 and 6.53 (2 × d, J

= 7.9 Hz, 2H, H6, H8), 7.14 (d, J = 8.6 Hz, 2H, H3’, H5’), 7.19 (t, J = 7.9 Hz, 1H, H7),

13 7.49 (d, J = 8.6 Hz, 2H, H2’, H6’), 8.32 (brs, 1H, OH); C NMR (75.6 MHz, CDCl3):

21.0 (CH3COO), 21.3 (CH3COO), 35.3 (C3), 63.8 and 72.0 (C2, C4), 106.9 (ArC), 108.8

(ArCH), 109.1 (ArCH), 121.7 (ArCH), 127.3 (ArCH), 131.7 (ArCH), 137.8 (ArC), 150.5

(ArC), 156.0 (ArC), 156.1 (ArC), 169.4 (COO), 173.9 (C=O); HRMS (ESI) m/z Calcd. for

196 + C19H18O6Na (M + Na) , 365.0996. Found 365.0979; Anal. Calcd. for C19H18O6: C, 66.65;

H, 5.29. Found: C, 66.44; H, 5.45.

4’–Acetoxy-5-hydroxyflav-3-ene (173)

This was prepared by the procedure used for preparation of OH flavene 161. Hydroxyflavene 173 was obtained as a light O - pink solid (80 mg, 15%). UV (MeOH): max 205 ( 25084 cm OAc 1 -1 -1 -1 -1 -1 M ), 219 ( 24293 cm M ), 281 ( 6096 cm M ) nm; IR (KBr): max 3437, 1756, 1736,

-1 1 1613, 1463, 1369, 1196, 1067, 1015, 913, 776 cm ; H NMR (300 MHz, CDCl3): 2.29

(s, 3H, CH3COO), 5.47 (brs, 1H, OH), 5.75 (dd, J = 3.4, 9.8 Hz, 1H, H3), 5.84 (dd, J =

1.9, 3.4 Hz, 1H, H2), 6.27 (d, J = 7.9 Hz, 1H, H6), 6.39 (d, J = 8.3 Hz, 1H, H8), 6.85

(dd, J = 1.9, 9.8 Hz, 1H, H4), 6.92 (dd, J = 7.9, 8.3 Hz, 1H, H7), 7.08 (d, J = 8.7 Hz, 2H,

13 H3’, H5’), 7.46 (d, J = 8.7 Hz, 2H, H2’, H6’); C NMR (75.6 MHz, CDCl3): 21.0 (2 ×

CH3COO), 76.0 (C2), 108.2 (ArCH), 108.7 (ArCH), 109.6 (ArC), 118.6 (ArCH), 121.6

(ArCH), 122.7 (ArCH), 128.2 (ArCH), 129.3 (ArCH), 138.3 (ArC), 150.4 (ArC), 151.6

+ (ArC), 153.9 (ArC), 169.6 (C=O); HRMS (ESI) m/z Calcd. for C17H14O4Na (M + Na) ,

305.2804 Found 305.2841; Anal. Calcd. for C17H14O4: C, 72.33; H, 5.00. Found: C,

72.26; H, 5.10.

1,2,3,5-Tetramethoxybenzene (181) OMe To a suspension of 3,4,5-trimethoxyphenol 88 (3.0 g, 16.3 mmol) and K2CO3 (3.0 g, 21.7 mmol) in acetone (75 mL) was added MeO OMe methyl iodide (2 mL, 32.1 mmol). The mixture was refluxed for 24 h OMe with addition of methyl iodide (2 mL, 32.1 mmol) after every 6 h. Acetone was distilled off under vacuum and the residue was dissolved in water and extracted with dichloromethane (25 mL × 3). The combined organic extracts were dried over anhydrous sodium sulfate and the solvent concentrated under vacuum to give 1,3,4,5- tetramethoxybenzene 181 as a white solid (3.1 g, 96%). M.p. 46 °C, lit.129 47 C; UV

197 -1 -1 -1 -1 -1 -1 (MeOH): max 210 ( 54938 cm M ), 230 ( 19215 cm M ) sh, 276 ( 3623 cm M )

1 nm; H NMR (300 MHz, CDCl3): 3.78 (s, 3H, CH3O), 3.784 (s, 3H, CH3O), 3.84 (s,

13 6H, 2 × CH3O), 6.15 (s, 2H, H4, H6); C NMR (75.6 MHz, CDCl3): 55.4 (CH3O), 56.0

(CH3O), 60.9 (CH3O), 91.7 (ArCH), 132.3 (ArC), 153.6 (ArC), 156.2 (ArC).

2’-Hydroxy-3’,4’,6’-trimethoxyacetophenone (182)

A solution of 1,2,3,5-tetramethoxybenzene 181 (3.0 g, 15.1 mmol) OMe O in dry ether (15 mL) was cooled to 0 °C under an argon atmosphere. Aluminium chloride (3.0 g, 22.5 mmol) was added in MeO OH portions followed by addition of acetyl chloride (3 mL, 42.2 mmol) OMe over 5 min. The reaction mixture was stirred at 0 °C for 3 h and was then kept overnight at r.t. The reaction was quenched by adding a mixture of conc. hydrochloric acid and ice. The precipitated solid was filtered, washed with water (50 mL) and dried.

Chromatography (SiO2, 30% ethyl acetate/hexane) gave acetophenone 182 as pale

128 yellow crystals (1.9 g, 56%). M.p. 114-115 °C, lit. 112-113 C; UV (MeOH): max 210

( 37346 cm-1M-1), 232 ( 23299 cm-1M-1) sh, 288 ( 38661 cm-1M-1), 331 ( 8196 cm-1M-

1 ) nm; IR (KBr): max 3500 (br), 2933, 1625, 1588, 1471, 1421, 1360, 1295, 1278, 1233,

-1 1 1212, 1126, 1025, 991, 791 cm ; H NMR (300 MHz, CDCl3): 2.61 (s, 3H, CH3CO),

3.81 (s, 3H, CH3O), 3.89 (s, 3H, CH3O), 3.93 (s, 3H, CH3O), 5.96 (s, 1H, H5’), 13.76 (s,

13 1H, OH); C NMR (75.6 MHz, CDCl3): 33.0 (CH3CO), 55.5 (CH3O), 55.9 (CH3O),

60.6 (CH3O), 86.4 (ArCH), 106.3 (ArC), 130.5 (ArC), 158.3 (ArC), 158.7 (ArC), 158.9

(ArC), 203.6 (C=O).

2’-Hydroxy-3’,4’,6’-trimethoxychalcone (183)

To a stirred mixture of acetophenone 182 (1.8 g, 7.96 OMe O mmol), benzaldehyde (1.2 g, 11.3 mmol) and ethanol (60 mL) was added a solution of KOH (15.0 g) in water (15 mL). MeO OH OMe

198 The resulting mixture was stirred overnight under an argon atmosphere. Crushed ice

(100 g) was added and the mixture was acidified to pH 3 with conc. hydrochloric acid.

The precipitated solid was filtered, washed with water and dried to give chalcone 183

279 as a yellow solid (2.37 g, 95%). M.p. 141-142 °C, lit. 144 C; UV (MeOH): max 204 (

-1 -1 -1 -1 313677 cm M ), 341 ( 22725 cm M ) nm; IR (KBr): max 3447 (br), 1625, 1558, 1420,

-1 1 1330, 1245, 1206, 1124, 1009, 793 cm ; H NMR (300 MHz, CDCl3): 3.84 (s, 3H,

CH3O), 3.95 (2 × s, 6H, 2 × CH3O), 6.02 (s, 1H, H5’), 7.40 and 7.61 (m, 5H, H2, H3,

13 H4, H5, H6), 7.88 (d, J = 15.3 Hz, 1H, H), 7.87 (d, J = 15.3 Hz, 1H, H); C NMR (75.6

MHz, CDCl3): 55.9 (CH3O), 56.0 (CH3O), 60.6 (CH3O), 87.1 (C5’), 106.9 (ArC), 127.4

(ArCH), 128.3 (ArCH), 128.7 (ArCH), 130.0 (C), 130.9 (ArC), 135.4 (ArC), 142.5 (C),

158.4 (ArC), 158.5 (ArC), 159.3 (ArC), 193.2 (C=O).

5,7,8-Trimethoxyflavanone (184)

A mixture of chalcone 183 (2.4 g, 7.6 mmol), methanol OMe O (120 mL) and conc. hydrochloric acid (60 mL) was refluxed for 40 h. Methanol was distilled off under vacuum and the MeO O OMe residue was diluted with ice water (200 mL). The precipitated solid was filtered, washed with water (100 mL) and dried. Chromatography

(SiO2, 50% ethyl acetate/hexane) gave starting material 175 (0.5 mg). Further elution with 100% ethyl acetate gave trimethoxyflavanone 184 (1.52 g, 63%). M.p. 163-165 °C,

128 -1 -1 -1 -1 lit. 156-158 C; UV (MeOH): max 211 ( 29398 cm M ), 237 ( 13026 cm M ) sh,

-1 -1 -1 -1 285 ( 16637 cm M ), 328 ( 5492 cm M ) nm; IR (KBr): max 3007, 2937, 1682, 1598,

-1 1 1569, 1346, 1276, 1124, 703 cm ; H NMR (300 MHz, CDCl3): 2.86 (dd, J = 3.4, 16.6

Hz, 1H, H3), 3.00 (dd, J = 12.0, 16.6 Hz, 1H, H3), 3.80 (s, 3H, CH3O), 3.91 (s, 3H,

CH3O), 3.93 (s, 3H, CH3O), 5.46 (dd, J = 3.4, 12.0 Hz, 1H, H2), 6.13 (s, 1H, H6), 7.40

13 (m, 5H, H2’, H3’, H4’, H5’, H6’); C NMR (75.6 MHz, CDCl3): 45.5 (C3), 56.0 (CH3O),

56.1 (CH3O), 61.1 (CH3O), 79.0 (C2), 89.4 (C6), 106.3 (ArC), 125.9 (ArCH), 128.4

199 (ArCH), 128.6 (ArCH), 131.1 (ArC), 138.8 (ArC), 156.2 (ArC), 157.8 (ArC), 158.7 (ArC),

189.2 (C=O).

cis-5,7,8-Trimethoxyflavan-4-ol (185)

A solution of flavanone 184 (250 mg, 7.96 mmol) in a OMe OH mixture of MeOH and THF (20 mL, 50:50) was cooled to 10

°C. Sodium borohydride (200 mg) was added in portions MeO O OMe and the mixture was stirred at the same temperature further for 1 h. The reaction was quenched by addition of acetic acid solution (10%, 4 mL), followed by stirring for 5 min. The reaction mixture was diluted with NaCl solution (10%,

100 mL) and the product was extracted with ethyl acetate (25 mL × 4). Solvent was distilled off and the residue was redissolved in ethyl acetate (25 mL), dried over anhydrous sodium sulfate and solvent evaporated to give flavanol 185 as a sticky solid

(240 mg, 95%). Attempts to solidify the product by trituration with various solvents and cooling failed. The product was found to be unstable and hence was immediately used

-1 -1 -1 -1 in the next reaction. UV (MeOH): max 210 ( 42295 cm M ), 236 ( 7659 cm M ) sh,

-1 -1 281 ( 168 cm M ) nm; IR (Chloroform): max 3500-2800 (br), 3017, 1610, 1502, 1466,

-1 1 1137, 1118, 1042 cm ; H NMR (300 MHz, CDCl3): 2.21 (ddd, J = 9.4, 11.7, 13.5 Hz,

1H, H3), 2.53 (ddd, J = 1.8, 7.1, 13.5 Hz, 1H, H3), 3.79 (s, 3H, CH3O), 3.88 (s, 3H,

CH3O), 3.89 (s, 3H, CH3O), 5.07 (dd, J = 1.8, 11.7 Hz, 1H, H4), 5.26 (dd, J = 7.1, 9.4

Hz, 1H, H2), 6.16 (s, 1H, H6), 7.40 (m, 5H, H2’, H3’, H4’, H5’, H6’); 13C NMR (75.6

MHz, CDCl3): 38.5 (C3), 55.1 (CH3O), 55.7 (CH3O), 59.8 (CH3O), 62.7 (C4), 76.9

(C2), 90.1 (C5), 125.9 (ArCH), 127.7 (ArCH), 128.3 (ArCH), 131.9 (ArC), 141.2 (ArC),

149.5 (ArC), 152.9 (ArC), 154.3 (ArC); HRMS (ESI) m/z Calcd. for C18H20O5Na (M +

Na)+ 339.1203. Found 339.1205.

200 5,7,8-Trimethoxyflav-3-ene (179) OMe A mixture of p-toluenesulfonic acid (16 mg) in toluene (120 mL) was refluxed for 1 h with azeotropic removal of water. MeO O OMe A solution of flavanol 185 (240 mg, 0.75 mmol) in dichloromethane (2 mL) was added over 2 min and heating was continued further for

15 min. The reaction mixture was cooled to r.t. and washed with saturated sodium bicarbonate solution (25 mL × 2). The toluene layer was dried over anhydrous sodium sulfate and the solvent evaporated under vacuum. Chromatography (SiO2, 20% ethyl acetate/hexane) gave pure flavene 179 as pale yellow oil (180 mg, 80%). The product was found to be unstable96 and hence was quickly analysed and used in next reaction.

-1 -1 -1 -1 -1 -1 UV (MeOH): max 204 ( 25651 cm M ), 216 ( 22753 cm M ), 242 ( 14830 cm M ),

-1 -1 - 291 ( 9227 cm M ) nm; IR (neat): max 2933, 1606, 1503, 1464, 1455, 1136, 1116 cm

1 1 ; H NMR (300 MHz, CDCl3): 3.65 (s, 3H, CH3O), 3.81 (s, 3H, CH3O), 3.84 (s, 3H,

CH3O), 5.69. (dd, J = 3.8, 10.1 Hz, 1H, H3), 5.88 (dd, J = 1.5, 3.8 Hz, 1H, H2), 6.05 (s,

1H, H6), 6.83 (dd, J = 1.5, 10.1 Hz, 1H, H4), 7.34 - 7.48 (m, 5H, H2’, H3’, H4’, H5’,

13 H6’); C NMR (75.6 MHz, CDCl3): 55.8 (CH3O), 56.1 (CH3O), 61.0 (CH3O), 76.6 (C2),

89.4 (C6), 105.3 (ArC), 118.6 (C4), 120.3 (C3), 126.9 (ArCH), 128.1 (ArCH), 128.4

(ArCH), 131.8 (ArC), 140.4 (ArC), 146.8 (ArC), 151.1 (ArC), 153.6 (ArC).

6a,12a-Dihydro-1,3,4,8,10,11-hexamethoxy-6-phenyl-7-[(1E)-2-phenylethenyl]-

6H,7H-[1]benzopyrano [4, 3-b][1]benzopyran. (Dependensin) (34)

To a solution of flavene 179 (500 mg, 1.67 mmol) in 2 MeO OMe methanol (50 mL) was added conc. hydrochloric acid OMe H MeO 11 O (10M, 4 mL) and the mixture was stirred overnight at 12a 4 OMe HH6a 9 O r.t. Methanol was removed under vacuum and the 7 H 6 OMe ß 2' product was dissolved in ethyl acetate, dried over 3' 2'' anhydrous sodium sulfate and concentrated. 3''

Chromatography (SiO2, 50% ethyl acetate/hexane) gave dependensin 34 as a white

201 solid (360 mg, 72%). The analytical sample was prepared by crystallization from

96 methanol. M.p. 197-199 °C (from MeOH), lit. 125-126 °C; UV (MeOH): max 238 (

-1 -1 -1 -1 26886 cm M ), 256 ( 21556 cm M ) nm; (KBr): max 2933, 1609, 1501, 1455, 1204,

-1 1 1140, 1116 cm ; H NMR (300 MHz, CDCl3): 2.31 (ddd, J = 1.9, 2.6, 11.3 Hz, 1H,

H6a), 3.35 (ddd, J = 1.5, 1.9, 5.7 Hz, 1H, H7), 3.67 (s, 3H, CH3O), 3.74 (s, 3H, CH3O),

3.82 (s, 3H, CH3O), 3.86 (s, 3H, CH3O), 3.89 (s, 3H, CH3O), 3.90 (s, 3H, CH3O), 4.96

(d, J = 11.3 Hz, 1H, H6), 5.40 (d, J = 2.6 Hz, 1H, H12a), 5.99 (dd, J = 1.5, 15.8 Hz, 1H,

H), 6.15 (s, 1H, H9), 6.17 (s, 1H, H2), 6.17 (dd, J = 5.7, 15.8 Hz, 1H, H), 7.10-7.40

13 (m, 10H, Ar); C NMR (75.6 MHz, CDCl3): 33.4 (C7), 41.5 (C6a), 56.3 (CH3O), 56.4

(CH3O), 56.8 (CH3O), 56.9 (CH3O), 61.3 (CH3O), 61.5 (CH3O), 63.0 (C12a), 77.2 (C6),

89.6 (C2), 89.9 (C9), 103.4 (C7a), 104.9 (C12b), 126.6 (C2’’, C6’’), 127.5 (C4’’), 127.8

(C2’, C6’), 128.8 × 2 (C3’, C5’, C3’’, C5’’), 128.9 (C4’), 131.0 (C), 131.9 (C11), 132.9

(C), 137.7 (C1’’), 139.3 (C1’), 147.6 (C11a), 149.9 (C4a), 152.5 (C10), 153.9 (C8),

+ 154.5 (C3), 155.2 (C1); MS (ESI) m/z Calcd. for C36H36O8Na (M + Na) 619.23. Found

619.21; Anal. Calcd. for C36H36O8: C, 72.46; H, 6.10. Found: C, 72.26; H, 6.10.

2’,4’,6’-Trihydroxyacetophenone (192)

Dry hydrogen chloride gas was passed through a mixture of dry O phloroglucinol 99 (25.2 g, 200 mmol), dry acetonitrile (21 mL, 400 HO OH mmol), dry ether (100 mL) and anhydrous zinc chloride (10.0 g, 75 mmol) at 0 °C for 2 h. The flask was stoppered, and kept in an ice OH bath for 4 h and then overnight in a refrigerator. Dry hydrogen chloride was once again passed through the mixture for 2 h and then the flask was kept in the refrigerator for 3 days. The supernatant ether was decanted off and the precipitate was washed with dry ether (25 mL). The solid was added to water (1 L) and the solution was refluxed for 2 h.

The mixture was left at r.t. for 24 h. The precipitated solid was filtered and dried at 120

°C. The acetophenone 192 was obtained as a yellow solid (24.0 g, 75%). M.p. 217-219

202 133 1 °C, lit. 217-219 °C; H NMR (300 MHz, acetone-d6): 2.59 (s, 3H, CH3CO), 5.91 (s,

2H, H3’, H5’), 9.12 (s, 1H, 4’ OH), 11.62 (s, 2H, 2’ OH, 6’ OH).

3’-Formyl-2’,4’,6’-trihydroxyacetophenone (193) O To a solution of 2’,4’,6’-trihydroxyacetophenone 192 (25.0 g, 148.8 HO OH mmol) in dry ether (500 mL) was added zinc cyanide (50.0 g, 425 CHO mmol). The suspension was cooled to 20 °C under an argon OH atmosphere and a rapid stream of dry hydrogen chloride gas was passed through the solution for 2 h maintaining the temperature at 20 °C. The mixture was then kept at ambient temperature further for 2 h. Ether was decanted off and the slurry was poured into water (500 mL) and the solution boiled for 5 min. The mixture was rapidly cooled to r.t. under running water, and the precipitated solid was filtered, washed with water (100 mL) and dried. The crude product was boiled with dilute hydrochloric acid (conc. hydrochloric acid (60 mL) and water (600 mL)) for 5 min., cooled rapidly to 40 °C, filtered and dried at 70 °C overnight. The acetophenone 193 was obtained as a white solid (21.0 g, 72%). M.p. 177-179 °C, lit.135 180-182 °C; 1H NMR (300 MHz, acetone- d6): 2.63 (s, 3H, CH3CO), 3.20 (brs, 1H, 4’ OH), 5.90 (s, 1H, H5’), 10.06 (s, 1H, CHO),

14.7 (brs, 2H, 2’ OH, 6’ OH).

2’,4’,6’-Trihydroxy-3’-methylacetophenone (194)

1) Preparation of zinc amalgam

Mercuric chloride (4.5 g, 16.5 mmol) was dissolved in a mixture of conc. hydrochloric acid (3 mL) and water (50 mL). Zinc wool (60.0 g, 923 mmol) was added and the mixture was stirred vigorously for 5 min. During the stirring the zinc wool was broken into small shining pieces. The aqueous layer was decanted. The amalgamated zinc was used immediately for the reduction.

203 2) Conc. hydrochloric acid (75 mL) and water (45 mL) were added to O a solution of acetophenone 193 (13.5 g, 68.8 mmol) in methanol (120 HO OH mL) in a 500 mL conical flask. The mixture was warmed to 50 °C and Me OH amalgamated zinc (prepared in part 1) was added in one lot. The heterogeneous mixture was stirred vigorously for 5 min. (exothermic reaction) and then quickly filtered through sintered glass funnel. The undissolved zinc amalgam was washed with methanol (50 mL). The combined filtrate was concentrated under vacuum until a yellow solid started precipitating. The mixture was cooled to r.t., filtered, washed with water (50 mL) and dried at 70 °C. The title compound 194 was obtained as an off- white solid (9.5 g, 76%). M.p. 209-211 °C, lit.134 210-211 °C; 1H NMR (300 MHz, acetone-d6): 1.94 (s, 3H, 3’ CH3), 2.59 (s, 3H, CH3CO), 6.05 (s, 1H, H5’), 8.90 (s, 1H,

4’ OH), 9.52 and 13.70 (2 × s, 2H, 2’ OH, 6’ OH).

3-Chloro-3-methyl-1-butyne (196)

To a cooled solution (10 °C) of CuCl (5.0 g, 50 mmol) in conc. CH3 H3C C C H hydrochloric acid (250 mL) was added anhydrous calcium chloride Cl

(110.0 g, 1.0 mol). The suspension was cooled with stirring to 0 °C and 3-hydroxy-3- methylbutyne 195 (84.0 g, 1.0 mol) was added in 3 h. The reaction mixture was further stirred at 0 °C for 1 h and then the two layers were separated. The organic layer was washed with water (100 mL), saturated sodium bicarbonate solution (100 mL), dried over anhydrous sodium sulfate and filtered. 3-Chloro-3-methyl-1-butyne 196 was

1 obtained as colourless liquid (74.5 g, 72%). H NMR (300 MHz, CDCl3): 1.86 (s, 6H, 2

13 × CH3), 2.62 (s, 1H, C-H); C NMR (75.6 MHz, CDCl3): 34.4 (2 × CH3), 56.8 (C3),

71.8 (C1), 86.5 (C2).

Tosylation of 2’,4’,6’-trihydroxy-3’-methylacetophenone (194)

A mixture of acetophenone 194 (5.0 g, 27.4 mmol), p-toluenesulfonyl chloride (5.2 g,

27.4 mmol), K2CO3 (3.8 g, 27.4 mmol) and acetone (300 mL) was refluxed for 3 h. TLC

204 analysis showed the presence of acetophenone 194 along with two products and the absence of p-toluenesulfonyl chloride. Acetone was removed under vacuum, the residue was diluted with water (300 mL) and the product was extracted with ethyl acetate (100 mL × 3). The combined organic extract was dried over anhydrous sodium sulfate and the solvent removed under vacuum. Chromatography (SiO2, 15% acetone/hexane) gave ditosyloxyacetophenone 199 (5.0 g). Further elution gave 2.5 g mixture of monotosyloxyacetophenone 198 and tritosyloxyacetophenone 200. The mixture containing acetophenones 198 and 200 was crystallized from methanol from which acetophenone 198 was isolated as colourless crystals (1.0 g, 11%).

2’,6’-Dihydroxy-3’-methyl-4’-tosyloxyacetophenone (198)

139 1 M.p. 183-185 °C, lit. 182-184 °C; H NMR (300 MHz, CDCl3): O HO OH 2.06 (s, 3H, 3’ CH3), 2.46 (s, 3H, CH3C6H5SO2), 2.56 (s, 3H,

CH3CO), 7.35 and 7.77 (2 × d, J = 8.3 Hz, 4H, ArH), 7.35 (s, 1H, Me OTs H5’), 7.35 and 13.47 (2 × s, 2H, 2’ OH, 6’ OH).

2’-Hydroxy-3’-methyl-4’,6’-ditosyloxyacetophenone (199)

White solid. M.p. 140-142 °C, lit.139 138-140 °C; 1H NMR (300 MHz, O

TsO OH CDCl3): 1.81 (s, 3H, 3’ CH3), 2.46 and 2.48 (2 × s, 6H, 2 ×

CH3C6H4SO2), 2.69 (s, 3H, CH3CO), 6.42 (s, 1H, H5’), 7.35 (2 × d, J Me OTs = 8.3 Hz, 4H, ArH), 7.72 (2 × d, J = 8.3 Hz, 4H, ArH), 13.11 (s, 1H,

OH).

3’-Methyl 2’,4’,6’-tritosyloxyacetophenone (200)280

1 White solid. M.p. 120-122 °C. H NMR (300 MHz, CDCl3): 1.80 O

TsO OTs (s, 3H, 3’ CH3), 2.38 (s, 3H, CH3CO), 2.51 (s (br), 9H, 3 ×

CH3C6H4SO2), 7.05 (s, 1H, H5), 7.15 and 7.70 (m, 12H, ArH). Me OTs

205 2’,6’-Dihydroxy-3’-methyl-4’-(t-butyldimethylsilyloxy)acetophenone (204)

To a solution of acetophenone 194 (2.18 g, 12 mmol) and imidazole (2.61 g, 38 mmol) in dry DMF (20 mL) was added TBDMSCl (2.16 g, 14.3 mmol). The mixture was stirred at r.t. for 15 h. TLC analysis showed about 15-20% conversion and formation of two products. Therefore, additional TBDMSCl (1.45 g, 9.6 mmol) was added and stirring was continued for further 6 h. The mixture was poured into ice-water (200 mL) and stirred for 15 min. The solid was filtered and dissolved in ether (60 mL). The ether layer was dried over anhydrous sodium sulfate and concentrated. Chromatography (SiO2,

4% ethyl acetate/hexane) gave disilyloxyacetophenone 205 (1.80 g). Further elution with 10% ethyl acetate/hexane gave monosilyloxyacetophenone 204 (1.10 g, 29%).

2’,6’-Dihydroxy-3’-methyl-4’-(t-butyldimethylsilyloxy)acetophenone (204)

White needles. M.p. 136-138 °C; UV (MeOH): 211 ( 17004 cm- max O 1 -1 -1 -1 -1 -1 M ), 286 ( 19921 cm M ), 332 ( 3059 cm M ) nm; IR (KBr): max HO OH

3255, 2931, 1632, 1591, 1426, 1294, 1125, 861, 824 cm-1; 1H NMR Me OTBDMS (300 MHz, CDCl3): 0.23 (s, 6H, Si(CH3)2), 0.99 (s, 9H, (CH3)3C),

2.03 (s, 3H, 3’ CH3), 2.66 (s, 3H, CH3CO), 5.84 (s, 1H, H5’), 8.82 and 10.93 each (bs,

13 1H, OH); C NMR (75.6 MHz, CDCl3): -4.3 (Si(CH3)2), 7.9 (ArCH3), 18.1 (Si-CH3),

25.5 (C(CH3)3), 32.7 (CH3CO), 97.6 (ArC), 98.5 (ArCH), 105.3 (ArC), 159.3 (ArC), 160.2

+ (ArC), 161.6 (ArC), 203.4 (C=O); MS (TOF-ESI) m/z Calcd. for C15H24O4SiNa (M + Na)

319.1336. Found 319.1239; Anal. Calcd. for C15H24O4Si: C, 60.78; H, 8.16. Found: C,

61.10; H, 8.45.

2’-Hydroxy-3’-methyl-4’,6’-di(t-butyldimethylsilyloxy)acetophenone (205)

White crystals. M.p. 76-78 °C (from MeOH); UV (MeOH): max O -1 -1 -1 -1 - 220 ( 16158 cm M ), 285 ( 17094 cm M ), 332 ( 3017 cm TBDMSO OH

1 -1 M ) nm; IR (KBr): max 3442, 2956, 2930, 1617, 1595, 1573, Me OTBDMS

206 -1 1 1420, 1282, 1130, 851 cm ; H NMR (300 MHz, CDCl3): 0.23 and 0.32 each (s, 6H,

Si(CH3)2), 0.99 (s, 18H, 2 × (CH3)3C), 1.99 (s, 3H, 3’ CH3), 2.62 (s, 3H, CH3CO), 5.84

13 (s, 1H, H5’), 13.78 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): -4.2 and -3.5 (2 ×

Si(CH3)2), 8.1 (CH3), 18.2 and 18.7 (2 × C(CH3)3), 25.5 and 26.0 (2 × C(CH3)3), 32.8

(CH3CO), 101.1 (ArCH), 108.6 (ArC), 109.4 (ArC), 156.7 (ArC), 159.9 (ArC), 164.0

+ (ArC), 203.4 (C=O); HRMS (TOF-ESI) m/z Calcd. for C21H38O4Si2Na (M + Na)

433.2201; Found 433.2102; Anal. Calcd. for C21H38O4Si2: C, 61.41; H, 9.33. Found: C,

61.42; H, 9.38.

2’-Hydroxy-4’,6’-ditosyloxyacetophenone (208)281,282

A mixture of 2’,4’,6’-trihydroxyacetophenone 192 (3.0 g, 17.8 mmol), O

TsO OH p-toluenesulfonyl chloride (6.8 g, 35.6 mmol), K2CO3 (5.0 g, 36.1 mmol) and acetone (150 mL) was refluxed for 3 h. Acetone was OTs removed under vacuum, the residue was diluted with water (100 mL) and acidified with 2M hydrochloric acid. The product was extracted with ethyl acetate (50 mL × 2). The combined organic extract was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 15% ethyl acetate/hexane) gave the ditosyloxyacetophenone 208 as a white solid (4.7 g, 55%).

1 M.p. 82-84 °C; H NMR (300 MHz, CDCl3): 2.46 and 2.48 each (s, 3H, CH3C6H4SO2),

2.66 (s, 3H, CH3CO), 6.35 (d, J = 2.3 Hz, 1H, H3’), 6.45 (d, J = 2.3 Hz, H5’), 7.36 (2 × d, J = 8.3 Hz, 4H, ArH), 7.72 (2 × d, J = 8.3 Hz, 4H, ArH), 12.71 (s, 1H, OH); 13C NMR

(75.6 MHz, CDCl3): 21.67 and 21.73 (2 × CH3), 32.4 (CH3CO), 107.6 (ArCH), 110.2

(ArCH), 113.7 (ArC), 128.3 (ArCH), 128.5 (ArCH), 130.0 (ArCH), 130.2 (ArCH), 131.6

(ArC), 131.8 (ArC), 146.1 (ArC), 146.6 (ArC), 150.6 (ArC), 153.5 (ArC), 164.4 (ArC),

203.1 (C=O).

Further elution gave tritosyloxyacetophenone 209 as a white solid (1.0 g, 8%).

207 2’,4’,6’-Tritosyloxyacetophenone (209)

1 O H NMR (300 MHz, CDCl3): 2.27 (s, 3H, CH3CO), 2.46 (s, 9H, 3 × TsO OTs CH3C6H4SO2), 6.88 (s, 2H, H3’, H5’), 7.35 (m, 6H, ArH), 7.67 (m,

6H, ArH). OTs

8-Acetyl-2,2-dimethyl-5,7-ditosyloxy-2H-chromene (206)281

i) A mixture of acetophenone 208 (0.9 g, 1.9 mmol), 3-chloro-3- O

TsO O methyl-1-butyne 196 (2.5 g, 24.8 mmol), K2CO3 (0.5 g, 3.6 mmol),

KI (0.56 g, 3.3 mmol), CuI (3 mg, 0.01 mmol) and dry acetone (10 OTs mL) was refluxed for 20 h. The mixture was concentrated under H vacuum, diluted with water (25 mL) and the product was extracted with ethyl acetate

(25 mL × 2). The combined extract was dried over sodium sulfate and concentrated when acetophenone 210 was obtained as a viscous oil (1.0 g, 97%). It was used in the

1 next step without further purification. H NMR (300 MHz, CDCl3): 1.53 (s, 6H, 2 ×

CH3), 2.31 (s, 3H, CH3CO), 2.43 and 2.45 each (s, 3H, CH3C6H4SO2), 2.59 (s, 1H, CH),

6.53 (d, J = 1.9 Hz, 1H, H3’), 7.32 (m, 3H, H5’, ArH), 7.70 (m, 4H, ArH).

ii) A solution of acetophenone 210 (1.0 g, 1.84 mmol) in N,N- O dimethylaniline (0.5 mL) and DMF (6 mL) was heated under an TsO O argon atmosphere at 140 °C for 2 h. The mixture was cooled to OTs r.t., poured into a mixture of dilute hydrochloric acid (2M, 25 mL) and crushed ice (25.0 g), and the product extracted with ethyl acetate (25 mL × 3). The combined organic extract was washed with saturated NaHCO3 solution (25 mL), dried over anhydrous sodium sulfate and concentrated under vacuum. Ditosyloxychromene

211 was obtained as a sticky solid (1.0 g, 100%), and was used in the next step without

1 further purification. H NMR (300 MHz, CDCl3): 1.33 (s, 6H, 2 × CH3), 2.38 (s, 3H,

208 CH3CO), 2.44 and 2.45 (2 × s, 6H, 2 × CH3C6H4SO2), 5.54 and 6.29 (2 × d, J = 10.2 Hz,

2H, H3, H4), 7.33 (m, 4H, ArH), 7.70 (2 × d, 4H, ArH).

iii) Ditosyloxychromene 211 (1.0 g, 1.84 mmol) was added to a O solution of KOH (1.0 g, 17.8 mmol) in methanol (16 mL). The HO O mixture was refluxed for 2 h and then cooled to r.t. KH2PO4 solution (10%, 100 mL) was added and the product was OH extracted with ethyl acetate (25 mL × 2). The combined organic layer was washed with saturated NaHCO3 solution (25 mL), dried over sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 15% ethyl acetate/hexane) gave dihydroxychromene

206 as a light pink solid (140 mg, 32%). M.p. 135-137 °C, lit.281 135-136 °C; 1H NMR

(300 MHz, acetone-d6): 1.50 (s, 6H, 2 × CH3), 2.61 (s, 3H, CH3CO), 5.50 and 6.59 (2

× d, J = 9.0 Hz, 2H, H3, H4), 9.50 (brs, 1H, 4 OH), 13.66 (s, 1H, 2 OH).

Octandrenolone (217)

To a suspension of 2’,4’,6’-trihydroxyacetophenone 192 (1.0 g, 5.9 O O mmol), KI (1.8 g, 10.7 mmol) and K2CO3 (1.6 g, 11.5 mmol) in dry acetone (10 mL) was added CuI (10 mg, 0.05 mmol). The reaction O OH mixture was stirred at reflux for 15 min followed by the dropwise addition of 3-chloro-3-methylbut-1-yne 196 (5.5 g, 53.6 mmol) over a period of 1.5 h.

The refluxing was continued for a further 3 h. TLC analysis showed the absence of starting material and formation of five products. The reaction mixture was cooled to r.t. and water (25 mL) was added. The product was extracted with ethyl acetate (25 mL ×

3) and the combined organic extracts were dried over anhydrous sodium sulfate. The crude product obtained from evaporation of ethyl acetate was dissolved in a mixture of

N,N-dimethylaniline (1 mL) and DMF (12 mL), and heated for 2 h at 140 ºC under an argon atmosphere. TLC analysis showed formation of one major spot and disappearance of two other spots from the crude starting material. The reaction mixture

209 was cooled to r.t. and diluted with hydrochloric acid (1M, 50 mL). The mixture was extracted with hexane (30 mL × 3), dried over anhydrous sodium sulfate and evaporated to yield a pale yellow oil. Chromatography (SiO2, 0.5% ethyl acetate/hexane) gave pure octandrenolone 217 (0.7 g, 40%) as yellow prisms. An analytical sample was prepared by recrystallization from pentane. M.p. 88-90 ºC, lit.5 90

-1 -1 -1 -1 - ºC; UV (EtOH) max: 240 ( 9586 cm M ) sh, 268 ( 24911 cm M ), 280 ( 20749 cm

1-1 -1-1 M ) sh, 294 ( 14787 cm M ) sh nm; IR (KBr): max 3444, 2972, 1646, 1596, 1468,

-1 1 1361, 1281, 1138, 1115, 872, 728 cm ; H NMR (300 MHz, CDCl3): 1.43 (s, 6H, 2 ×

2” CH3), 1.49 (s, 6H, 2 × 2”’ CH3), 2.65 (s, 3H, CH3CO), 5.43 (2 × d, J = 10.2 Hz, 2H,

H3’’, H3’’’), 6.58 (d, J = 10.2 Hz, 1H, H4’’’), 6.64 (d, J = 10.2 Hz, 1H, H4’’), 13.99 (s, 1H,

13 -OH); C NMR (75.6 MHz, CDCl3): 27.9 (CH3), 28.3 (CH3), 33.1 (CH3CO), 78.1 (C2’’),

78.2 (C2’’’), 102.1, 102.2 and 105.4 (C1, C3, C5), 116.1 and 116.3 (C4’’, C4’’’), 124.6 and 125.3 (C3’’, C3’’’), 154.9, 156.6 and 160.5 (C2, C4, C6), 203.2 (C=O); HRMS (ESI)

+ m/z Calcd. for C18H20O4Na (M + Na) 323.1254. Found 323.1263; Anal. Calcd. for

C18H20O4: C, 71.98; H, 6.71. Found: C, 72.07; H, 6.98.

Flemiculosin (218)

To a solution of octandrenolone 217 (300 mg, 1 mmol) 6'' 5''

2'' and benzaldehyde (260 mg, 2.5 mmol) in absolute ethanol 3'' O O 2' 4'' 1' (10 mL) was added a solution of KOH (2.5 g, 44.6 mmol) 3' 2 4' 6' 1 3 in water (2.5 mL). The dark brown mixture was stirred at O 5' OH 2''' 5''' 4''' 6 4 3''' 5 ambient temperature under an argon atmosphere for 6 h. 6'''

The reaction mixture was poured into water (50 mL) and acidified to pH 5 using 3M hydrochloric acid. The product was extracted with ethyl acetate (25 mL × 3), dried over anhydrous sodium sulfate and concentrated under vacuum to yield brown oil.

Chromatography (SiO2, 1% acetone/hexane) gave pure flemiculosin 218 (350 mg,

90%) as red needles. An analytical sample was prepared by recrystallisation from

210 7 -1 -1 pentane. M.p. 98-99 ºC, lit. 99 ºC; UV (MeOH): max 202 ( 14900 cm M ), 277 (

-1 -1 -1 -1 -1 -1 16750 cm M ), 306 ( 17050 cm M ), 359 ( 14150 cm M ) nm; IR (KBr): max 3444,

-1 1 2970, 1633, 1601, 1588, 1546, 1341, 1184, 1141, 703 cm ; H NMR (300 MHz,

CDCl3): 1.45 (s, 6H, 5’’ CH3, 6’’ CH3), 1.54 (s, 6H, 5’’’ CH3, 6’’’ CH3), 5.47 (d, J = 10.2

Hz, 2H, H3’’, H3’’’), 6.61 (d, J = 10.2 Hz, 1H, H4’’’), 6.69 (d, J = 10.2 Hz, 1H, H4’’), 7.40

(m, 3H, H2, H4, H6), 7.61 (m, 2H, H3, H5), 7.76 (d, J = 15.5 Hz, 1H, H), 8.09 (d, J =

13 15.5 Hz, 1H, H), 14.36 (s, 1H, OH); C NMR (75.6 MHz, CDCl3 ): 28.0 (CH3), 28.3

(CH3 ), 77.1 and 78.2 (C2’’, C2’’’), 102.4, 102.5 and 105.9 (C1’, C3’, C5’), 116.2 and

116.6 (C4’’, C4’’’), 124.7 (C), 125.3 and 127.6 (C3’’, C3’’’), 128.1 (C2, C6), 128.5 (C3,

C5), 128.8 (C4), 129.9, 135.6 (C1), 142.0 (C), 155.2, 156.1 and 161.4 (C2’, C4’, C6’),

+ 192.8 (C=O); HRMS (ESI) m/z Calcd. for C25H24O4Na (M + Na) 411.1567. Found

411.1569; Anal. Calcd. for C25HO 24 4: C, 77.29; H, 6.22. Found: C, 77.03; H, 6.43.

(±)-3-Deoxy-MS-II (219)

To a solution of anhydrous sodium acetate (1.2 g, 14.6 6'' 5'' 2'' mmol) in ethanol (40 mL) was added flemiculosin 218 (400 3'' O O 5 4 4'' 4a 3 6 mg, 1 mmol). The reaction mixture was refluxed in an oil 2' 7 8a 2 3' O 8 O 1' bath for 48 h. Ethanol was distilled off under vacuum and 5''' 2''' 4''' 6' 4' 3''' 5' the residue was dissolved in water (20 mL). The product 6''' was extracted with dichloromethane (20 mL × 3), dried over anhydrous sodium sulfate and concentrated under vacuum to yield a yellow oil. Chromatography (SiO2, 5% ethyl acetate/hexane) yielded unreacted starting material (140 mg). Further elution (10% ethyl acetate/hexane) yielded the title compound 219 (170 mg, 42%) as yellow crystals.

-1 -1 M.p. 145-147 ºC (from hexane); UV (MeOH): max 267 ( 31818 cm M ), 315 ( 1168

-1 -1 -1 -1 cm M ) sh, 368 ( 3181 cm M ) nm; IR (KBr): max 2976, 1640, 1591, 1573, 1434,

-1 1 1140, 1014, 728 cm ; H NMR (300 MHz, CDCl3): 1.44 (s, 3H, 5’’’ CH3), 1.45 (s, 3H,

6’’’ CH3), 1.48 (s, 3H, 5’’ CH3), 1.52 (s, 3H, 6’’ CH3), 2.77 (dd, J = 3.1, 16.6 Hz, 1H, H3),

211 2.96 (dd, J = 12.8, 16.6 Hz, 1H, H3), 5.39 (dd, J = 3.0, 12.8 Hz, 1H, H2), 5.46 (d, J =

10.1 Hz, 1H, H3’’’), 5.50 (d, J = 10.1 Hz, 1H, H3’’), 6.57 (d, J = 10.1 Hz, 1H, H4’’’), 6.60

13 (d, J = 10.1 Hz, 1H, H4’’), 7.35-7.46 (m, 5H, H2’ H3’, H4’, H5’, H6’); C NMR (75.6

MHz, CDCl3): 27.8 (CH3), 28.0 (CH3), 28.1 (CH3), 28.4 (CH3), 45.8 (C3), 78.9 (C2),

102.3 (C6), 104.5 (C8), 105.5 (C4a), 115.7 and 116.2 (C4’’, C4’’’), 125.8 (C2’, C6’),

126.1 and 126.5 (C3’’, C3’’’), 128.6 (C3’, C5’), 128.7 (C4’), 139.0 (C1’), 154.2 (C5),

155.9 (C7), 157.49 (C8a), 188.6 (C4); HRMS (ESI) m/z Calcd. for C25H24O4Na (M +

+ Na) 411.1567. Found 411.1561; Anal. Calcd. for C25H24O4: C, 77.29; H, 6.22. Found:

C, 77.38; H 6.40.

Laxichalcone (220)

A solution of octandrenolone 217 (200 mg, 0.66 mmol) 6'' 5'' 2'' and 4-methoxymethoxybenzaldehyde 235 (165 mg, 3'' O O 2' 4'' 1' 3' 0.99 mmol) in dry DMF (2 mL) was cooled to 0 ºC 2 4' 6' 3 O 5' OH 1 under an argon atmosphere. Sodium hydride (80 mg, 2 5''' 2''' 4 4''' 6 3''' 5 OH mmol) was added in three lots and the mixture was 6''' stirred for 1 h at 0 ºC. Ethanol (15 mL) was slowly added followed by addition of water

(2 mL) and conc. hydrochloric acid (2 mL). The mixture was heated at 60 ºC for 3 h.

Ethanol was distilled off under reduced pressure and the residue was diluted with water

(25 mL). The product was extracted with dichloromethane (25 mL × 3), dried over anhydrous sodium sulfate and the solvent removed under vacuum. Chromatography

(SiO2, 20% ethyl acetate/hexane) gave pure laxichalcone 220 as red needles (210 mg,

11 78%). M.p. 174-176 ºC (from EtOH), lit. 174-176 ºC; UV (MeOH): max:203 ( 18876 cm-1M-1), 252 ( 22179 cm-1M-1), 266 ( 21685 cm-1M-1), 276 ( 22764 cm-1M-1), 376 (

-1 -1 31797 cm M ) nm; IR (KBr): max 3382, 3235, 1648, 1628, 1603, 1584, 1442, 1345,

-1 1 1185, 1153, 971 cm ; H NMR (300 MHz, DMSO-d6): 1.39 (s, 6H, 5’’ CH3, 6’’ CH3),

1.48 (s, 6H, 5’’’ CH3, 6’’’ CH3), 5.60 (d, J = 10.2 Hz, 1H, H3’’’), 5.61 (d, J = 10.2 Hz, 1H,

212 H3’’), 6.49 (d, J = 10.2 Hz, 1H, H4’’’), 6.52 (d, J = 10.2 Hz, 1H, H4’’), 6.84 (d, J = 8.7

Hz, 2H, H3, H5), 7.52 (d, J = 8.7 Hz, 2H, H2, H6), 7.68 (d, J = 15.5 Hz, 1H, H), 7.84 (d,

13 J = 15.5 Hz, 1H, H), 10.16 (bs, 1H, 4 OH), 14.42 (s, 1H, 6’ OH); C NMR (75.6 MHz,

DMSO-d6): 28.0 (CH3), 28.3 (CH3), 78.6 and 78.7 (C2’’, C2’’’), 102.3, 102.5 and 105.7

(C1’, C3’, C5’), 115.7 and 116.0 (C4’’, C4’’’), 116.5 (C3, C5), 123.6, 126.1, 126.3 and

126.6 (C3’’, C3’’’, C1, C), 130.8 (C2, C6), 143.8 (C), 154.6, 155.8, 160.6, 160.6 (C2’,

C4’, C6’, C4) 192.6 (C=O); Anal. Calcd. for C25H24O5: C, 74.24; H, 5.98. Found: C,

74.35; H, 6.21.

3’-Nitrodaidzein (247)181

To a stirred suspension of ammonium cerium(IV) nitrate (1.0 g, 1.82 mmol) in acetic acid (20 mL) OH O was added a solution of daidzein 38 (0.46 g, 1.82 NO2 mmol) in DMF (3 mL). The mixture was stirred HO O overnight at r.t. and then poured with stirring into cold water (150 mL). The resulting yellow solid was filtered, washed with water and air dried (0.5 g, 92%). M.p. 310-312

-1 1 °C; IR (KBr): max 3272, 1627, 1587, 1577, 1533, 1309, 1278, 1238, 1177 cm ; H NMR

(300 MHz, acetone-d6): 6.91 (d, J = 2.3 Hz, 1H, H8), 7.02 (dd, J = 2.3, 8.7 Hz, 1H,

H6), 7.24 (d, J = 8.7 Hz, 1H, H5’), 7.95 (dd, J = 2.3, 8.7 Hz, 1H, H6’), 8.05 (d, J = 8.7

Hz, 1H, H5), 8.40 (s, 1H, H2), 8.45 (d, J = 2.3 Hz, 1H, H2’), 9.78 (brs, 1H, OH), 10.47

+ (brs, 1H, OH); HRMS (ESI) m/z Calcd. for C15H9O6NNa (M + Na) 322.0322. Found

322.0319.

Kudzuisoflavone-A (35)

OH Daidzein 38 (500 mg, 1.96 mmol) was O O OH added to a suspension of CuCl (500 HO O O mg, 5.05 mmol) in DMF (10 mL). The HO

213 mixture was heated to 100 °C and air was bubbled through the mixture for 5 h. The reaction mixture was cooled to r.t. and poured into hydrochloric acid (200 mL, 1M). The precipitated solid was filtered, washed with water (20 mL × 2) and air dried. The solid was dissolved in THF and adsorbed on silica gel. Chromatography (SiO2, 60% ethyl acetate/hexane) gave the title compound 35 as an off-white solid (48 mg, 10%). M.p.

283 -1 -1 -1 -1 >300, lit. >300 °C; UV (MeOH): max 239 ( 43863 cm M ), 243 ( 44440 cm M ),

-1 -1 -1 -1 -1 -1 246 ( 44890 cm M ), 248 ( 44845 cm M ), 298 ( 20663 cm M ) nm; IR (KBr): max

3393, 3227, 1624, 1576, 1506, 1456, 1261, 1195, 1099 cm-1; 1H NMR (300 MHz, acetone-d6): 6.88 (d, J = 2.3 Hz, 2H, H8, H8’’), 6.97 (dd, J = 2.3, 8.7 Hz, 2H, H6,

H6’’), 7.04 (d, J = 8.3 Hz, 2H, H5’, H5’’’), 7.55 (dd, J = 2.3, 8.3 Hz, 2H, H6’, H6’’’), 7.59

(d, J = 2.3 Hz, 2H, H2’, H2’’’), 8.04 (d, J = 8.7 Hz, 2H, H5, H5’’), 8.25 (s, 2H, H2, H2’’);

13 C NMR (75.6 MHz, DMSO-d6): 102.5 (ArCH), 115.5 (ArCH), 115.9 (ArC), 117.0

(ArCH), 122.8 (ArC), 123.8 (ArCH), 126.0 (ArC), 127.7 (ArCH), 128.8 (ArC), 129.2

(ArC), 132.3 (ArCH), 153.3 (ArC), 155.0 (ArC), 157.8 (ArCH), 162.9 (ArC), 175.1

(C=O).

cis-6a,13a-Dihydro-6a,9-bis(4-hydroxyphenyl)-6H,10H-furo[3,2-c:4,5-g’]bis[1] benzopyran-3-ol (257)

Air was bubbled for 3 h through a stirred 12 O 11a H 10 O solution of phenoxodiol 111 (500 mg, 2.08 1 13a 7a 13b 2 8 7 6a mmol) and CuCl (250 mg, 2.52 mmol) in 6 2'' HO O 4a OH 3'' H 4 DMF (10 mL). The mixture was poured into a Hb 2' water (100 mL) and the precipitated solid HO 3' was filtered and washed with water. The crude product was re-dissolved in ethyl acetate (25 mL), filtered through a pad of Celite® and the filtrate was concentrated under vacuum. Chromatography (SiO2, 40% ethyl acetate/hexane) gave dimeric compound 257 as a pink solid (302 mg, 60%). M.p. 232 °C; UV (MeOH): max 230 (

-1 -1 -1 -1 -1 -1 19991 cm M ), 256 ( 12422 cm M ), 344 ( 19003 cm M ) nm; IR (KBr): max 3402, 214 -1 1 1618, 1514, 1480, 1249, 1151, 1104 cm ; H NMR (300 MHz, acetone-d6): 3.92 (d, J

= 11.7 Hz, 1H, H6), 4.62 (dd, J = 0.8, 11.7 Hz, 1H, H6), 5.08 (d, J = 1.1 Hz, 1H, H10),

5.53 (d, J = 0.8 Hz, 1H, H13a), 6.34 (s, 1H, H12), 6.36 (d, J = 2.3 Hz, 1H, H4), 6.51 (dd,

J = 2.3, 8.3 Hz, 1H, H2), 6.75 (d, J = 1.1 Hz, 1H, H8), 6.77 (s, 1H, H7), 6.81 (d, J = 8.7

Hz, 2H, H3’, H5’), 6.84 (d, J = 8.7 Hz, 2H, H3’’, H5’’), 7.28 (d, J = 8.3 Hz, H1), 7.36 (d, J

= 8.7 Hz, 2H, H2’’, H6’’), 7.38 (d, J = 8.7 Hz, 2H, H2’, H6’), 8.30 (s, 1H, 4’ OH), 8.45 (s,

13 1H, 4’’ OH), 8.53 (s, 1H, 3 OH); C NMR (75.6 MHz, acetone-d6): 49.5 (C6a), 68.7

(C6), 66.8 (C10), 86.0 (C13a), 97.9 (C12), 102.8 (C4), 109.5 (C2), 110.3 (C13b), 115.2

(C3’, C5’), 115.4 (C3’’, C5’’), 117.0 (C7a), 117.4 (C8), 122.5 (C7), 125.7 (C6b, C2’’,

C6’’), 128.1 (C9), 128.3 (C1’’), 128.7 (C2’, C6’), 131.2 (C1’), 132.7 (C1), 154.5 (C11a),

155.8 (C4a), 156.5 (C4’), 157.2 (C4’’), 159.1 (C3), 159.7 (C12a); HRMS (ESI) m/z

+ Calcd. for C30H22O6Na (M + Na) 501.1309. Found 501.1307.

2,4’,7-Trihydroxyisoflav-3-ene (260) OH To a stirred solution of phenoxodiol 111 (250 mg, 1.04 mmol) in TFA (5 mL) was added thallium(III) HO O OH trifluoroacetate (TTFA) (600 mg, 1.10 mmol). The mixture was stirred further for 15 min, poured into water (120 mL) and extracted with ethyl acetate (50 mL × 1, 25 mL × 2).

The combined organic extract was washed with saturated sodium bicarbonate solution

(50 mL × 2), dried over anhydrous sodium sulfate and concentrated under vacuum. The crude product was adsorbed onto silica gel. Chromatography (SiO2, 40% ethyl acetate/hexane) gave trihydroxyisoflav-3-ene 260 as a pink solid (130 mg, 48%). M.p.

-1 -1 -1 -1 >325 °C; UV (MeOH): max 211 ( 22853 cm M ), 236 ( 11623 cm M ), 323 ( 26597

-1 -1 cm M ) nm; IR (KBr): max 3228 (br), 3228 (br), 1814, 1623, 1610, 1589, 1518, 1508,

-1 1 1286, 1257, 1129, 983, 963 cm ; H NMR (300 MHz, acetone-d6): 5.91 (d, J = 7.1

Hz, 1H, 2 OH) , 6.21 (d, J = 7.1 Hz, 1H, H2), 6.45 (d, J = 2.6 Hz, 1H, H8), 6.48 (dd, J =

2.6, 8.3 Hz, 1H, H6), 6.85 (d, J = 8.7 Hz, 2H, H3’, H5’), 6.88 (s, 1H, H4’), 7.08 (d, J =

8.3 Hz, 1H, H5), 7.50 (d, J = 8.7 Hz, 2H, H2’, H6’), 8.37 (s, 1H, 4’ OH), 8.42 (s, 1H, 7

215 13 OH); C NMR (75.6 MHz, acetone-d6): 91.6 (C2), 103.3 (C8), 108.7 (C6), 114.4

(C4a), 115.3 (C3’, C5’), 118.0 (C4), 126.5 (C2’, C6’), 127.6 (C5), 128.7 and 129.0 (C3 and C1’), 151.6 (C8a), 156.9 (C4’), 158.2 (C7); HRMS (ESI) m/z Calcd. for C15H12O4Na

(M + Na)+ 279.0628. Found 279.0630.

Further elution gave the dimeric compound 261 as light pink solid (40 mg, 15%).

Bis-(4’,7-dihydroxyisoflav-3-ene-2-yl)ether (261)

-1 -1 3' UV (MeOH): max 210 ( 58558 cm M ), 238 ( 2' OH

-1 -1 -1 -1 45 3117 cm M ), 323 ( 62612 cm M ) nm; IR 6 5' 6'

8'' (KBr): max 3329, 1614, 1514, 1462, 1248, 1152, HO 8 O O O OH

-1 1 6''' 1120, 958, 907, 830 cm ; H NMR (300 MHz, 5''' 6'' 4'' 5'' 2''' acetone-d6): 6.58 (dd, J = 2.3, 8.3 Hz, 2H, H6, HO 3''' H6’’), 6.66 (d, J = 8.7 Hz, 4H, H3’, H3’’’, H5’, H5’’’), 6.72 (s, 2H, H2, H2’’), 6.75 (d, J =

2.3 Hz, 2H, H8, H8’’), 6.98 (s, 2H, H4, H4’’), 7.12 (d, J = 8.3 Hz, 2H, H5, H5’’), 7.28 (d,

J = 8.7 Hz, 4H, H2’, H2’’’, H6’, H6’’’), 8.42 (s, 2H, 4’ OH, 4’’’ OH), 8.73 (s, 2H, 7 OH, 7’’

13 OH); C NMR (75.6 MHz, acetone-d6): 91.7 (C2), 103.7 (C8), 109.7 (C6), 114.6

(C4a), 115.2 (C3’, C5’), 119.2 (C4), 126.5 (C3), 126.5 (C2’, C6’), 127.7 (C1’), 128.0

(C5), 150.8 (C8a), 156.9 (C4’), 158.4 (C7); HRMS (ESI) m/z Calcd. for C30H22O7Na (M

+ Na)+ 517.1258. Found 517.1263.

4’,7-Dimethoxyisoflavone (262)

To a stirred solution of daidzein 38 (2.0 g, 7.8 mmol) OMe O in DMSO (10 mL) was added a solution of KOH (1.3 g, 23 mmol) in water (1.5 mL). After 5 min at r.t., MeO O methyl iodide (4.4 g, 31.2 mmol) was added and the stirring was continued for further 2 h. The mixture was poured into water (200 mL) and the resulting solid was filtered, washed with water and air dried. The title compound 262 was obtained as a white solid

216 (2.0 g, 90%). M.p. 163-165 °C (from acetone), lit.284 162-163 °C; 1H NMR (300 MHz,

DMSO-d6): 3.79 (s, 3H, CH3O), 3.90 (s, 3H, CH3O), 6.99 (d, J = 8.4 Hz, 2H, H3’, H5’),

7.07 (dd, J = 2.5, 8.8 Hz, 1H, H6), 7.14 (d, J = 2.5 Hz, 1H, H8), 7.52 (d, J = 8.4 Hz, 2H,

H2’, H6’), 8.02 (d, J = 8.8 Hz, 1H, H5), 8.40 (s, 1H, H2).

2,4-Dihydroxyphenyl-3,4-dimethoxybenzyl ketone (265)

A mixture of resorcinol 72 (2.8 g, 25 mmol), 3,4- OMe OMe dimethoxyphenylacetic acid 264 (4.9 g, 25 mmol) and O

BF3·OEt2 (60 mL) was heated with stirring under an HO OH argon atmosphere at 110 °C for 1.5 h. The mixture was cooled and kept in a refrigerator overnight. The precipitated solid was filtered, washed with saturated sodium acetate solution (12%, 100 mL) and air dried (3.8 g,

52%). The product was used in the next step without further purification. M.p. 178-180

°C, lit.285 182-183 °C.

7-Hydroxy-3’,4’-dimethoxyisoflavone (266)

BF3·OEt2 (4.3 mL, 34 mmol) was slowly added to a OMe OMe stirred solution of ketone 265 (2.0 g, 6.9 mmol) in DMF O

(16 mL). The mixture was warmed to 50 °C under an HO O argon atmosphere and then a solution of methanesulfonyl chloride (2 mL, 25.8 mmol) in DMF (4 mL) was added dropwise. The mixture was then heated at 110 °C for 2 h, cooled to r.t. and poured into cold water

(150 mL). The resulting solid was filtered, washed with water and air dried (1.54 g,

74%). The product was used in the next step without further purification. M.p. 254-257

°C (from EtOH), lit.285 257-258 °C.

217 7-Acetoxy-3’,4’-dimethoxyisoflavone (267) OMe A mixture of isoflavone 266 (1.0 g, 3.4 mmol), acetic OMe O anhydride (5 mL, 52.9 mmol) and pyridine (1 mL, 12.3 mmol) was heated at 100 °C for 2 h. The mixture was AcO O cooled to r.t., poured into hydrochloric acid (1 M, 50 mL) and stirred for 10 min. The solid was filtered, washed with water and air dried (1.0 g, 87%). M.p. 166-168 °C (from

286 1 MeOH), lit. 163-164 °C; H NMR (300 MHz, CDCl3): 2.35 (s, 3H, CH3COO), 3.91 (s,

3H, CH3O), 3.92 (s, 3H, CH3O), 6.92 (d, J = 8.3 Hz, 1H, H5’), 7.05 (dd, J = 2.3, 8.3 Hz,

1H, H6’), 7.16 (dd, J = 2.3, 8.6 Hz, 1H, H6), 7.18 (d, J = 2.3 Hz, H2’), 7.29 (d, J = 2.3

Hz, 1H, H8), 7.99 (s, 1H, H2), 8.31 (d, J = 8.6 Hz, 1H, H5).

7,7’’-Diacetoxy-3’,3’’’,4’,4’’’-tetramethoxy-6’,6’’’-biisoflavonyl (269)

A solution of isoflavone 267 (500 mg, 1.47 OMe 3' 2' OMe mmol) in dichloromethane (11 mL) was O 5 8'' 5' O OAc 6 2'' cooled to 0 C under an argon 2 5''' 6'' AcO 8 O 5'' atmosphere. Thallium(III) trifluoroacetate 2''' O MeO 3''' (TTFA) (400 mg, 0.73 mmol) was added OMe followed by addition of BF3·OEt2 (0.5 mL). The reaction was stirred for 2.5 h and then quenched by addition of KI solution (2.0 g in 20 mL water) followed by stirring at ambient temperature for 30 min. Sodium metabisulfite solution (0.1 g dissolved in minimum amount of water) was added followed by further stirring for 10 min. The yellow precipitate was filtered and washed with dichloromethane (10 mL × 3). The organic layer was separated and the aqueous layer was extracted with dichloromethane (20 mL). The combined organic layer was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 100% dichloromethane) gave the title compound 269 as pale yellow crystals (354 mg, 71%). M.p. 257-259 °C (from

-1 -1 -1 -1 MeOH); UV (MeOH): max 218 ( 44090 cm M ), 241 ( 36524 cm M ), 296 ( 15479

218 -1 -1 -1 1 cm M ) nm; IR (KBr): max 1768, 1650, 1618, 1506, 1439, 1250, 1201, 1176 cm ; H

NMR (300 MHz, CDCl3): 2.34 (s, 6H, 2 × CH3COO), 3.75 and 3.86 (2 × s, 12H, 4 ×

CH3O), 6.83 and 6.87 (2 × s, 4H, H2’, H2’’’, H5’, H5’’’), 7.02 (dd, J = 2.3, 8.6 Hz, 2H,

H6, H6’), 7.21 (d, J = 2.3 Hz, 2H, H8, H8’’), 7.75 (s, 2H, H2, H2’’), 7.80 (d, J = 8.6 Hz,

13 2H, H5, H5’’); C NMR (75.6 MHz, CDCl3): 21.1 (CH3COO), 55.8 and 55.9 (2 ×

CH3O), 110.7 (ArCH), 114.2 (ArCH), 114.3 (ArCH), 119.2 (ArCH), 121.9 (ArC), 122.4

(ArC), 124.2 (ArC), 127.2 (ArCH), 132.5 (ArC), 147.7 (ArC), 148.5 (ArC), 154.3 (ArC),

155.2 (ArCH), 156.4 (ArC), 168.36 (C=O), 175.8 (COO); HRMS (ESI) m/z Calcd. for

+ C38H30O12Na (M + Na) 701.1629. Found 701.1640; Anal. Calcd. for C38H30O12: C,

67.25; H, 4.46. Found: C, 67.32; H, 4.57.

3’,4’,7-Trimethoxyisoflavone (271)

To a suspension of isoflavone 266 (500 mg, 1.6 OMe OMe mmol) in DMSO (2.5 mL) was added a solution of O

NaOH (135 mg, 3.3 mmol) in water (1 mL) followed MeO O by methyl iodide (1 mL, 16.0 mmol). The mixture was stirred at r.t. overnight and diluted with water (50 mL). The precipitated solid was filtered, washed with water and air dried (470 mg, 90%). M.p. 163 °C, lit.285 165 °C; 1H

NMR (300 MHz, CDCl3): 3.91 (s, 3H, CH3O), 3.92 (s, 3H, CH3O), 3.93 (s, 3H, CH3O),

6.86 (d, J = 2.4 Hz, 1H, H8), 6.93 (d, J = 7.9 Hz, 1H, H5’), 7.00 (dd, J = 2.4, 9.2 Hz, 1H,

H6), 7.05 (dd, J = 1.8, 7.9 Hz, H6’), 7.21 (d, J = 1.8 Hz, 1H, H2’), 7.88 (s, 1H, H2), 8.22

13 (d, J = 9.2 Hz, 1H, H5); C NMR (300 MHz, CDCl3): 55.8 (CH3O), 56.0 (2 × CH3O),

100.2 (ArCH), 111.2 (ArCH), 112.6 (ArCH), 114.6 (ArCH), 118.4 (ArCH), 121.1 (ArC),

124.8 (ArC), 125.0 (ArC), 127.8 (ArCH), 148.8 (ArC), 149.2 (ArC), 152.2 (ArCH), 157.9

(ArC), 164.0 (ArC), 175.9 (C=O).

219 3’,3’’’,4’,4’’’,7,7’’-Hexamethoxy-6’,6’’’-biisoflavonyl (272)

The title compound was synthesized OMe OMe following the procedure for dimer 269 O O OMe using trimethoxyisoflavone 271 (230 mg, MeO O 0.737 mmol), TTFA (199 mg, 0.36 mmol) O MeO and BF3·OEt2 (0.25 mL). OMe

Chromatography (SiO2, 2% ethyl acetate/dichloromethane) gave the title compound as off-white crystals (175 mg, 76%). M.p. 256-258 °C (from MeOH); UV (MeOH): max 216

-1 -1 -1 -1 -1 -1 ( 60803 cm M ), 248 ( 43627 cm M ) sh, 296 ( 25721 cm M ) nm; IR (KBr): max

1673, 1625, 1605, 1505, 1440, 1248, 1201, 1170, 1031, 1031cm-1; 1H NMR (300 MHz,

CDCl3): 3.71 and 3.86 (2 × s, 12 H, 4 × CH3O), 3.89 (s, 6H, 2 × CH3O), 6.78 (d, J =

2.3 Hz, 2H, H8, H8’’), 6.81 and 6.90 (2 × s, 4H, H2’, H2’’’, H5’, H5’’’), 6.85 (dd, J = 2.3,

9.0 Hz, 2H, H6, H6’’), 7.75 (d, J = 9.0 Hz, 2H, H5, H5’’), 7.76 (s, 2H, H2, H2’’); 13C NMR

(75.6 MHz, CDCl3): 55.8 (3 × CH3O), 99.9 (ArCH), 114.1 (ArCH), 114.3 (ArCH), 114.4

(ArCH), 118.1 (ArC), 123.0 (ArC), 124.1 (ArC), 127.2 (ArCH), 132.7 (ArC), 147.5 (ArC),

148.3 (ArC), 154.7 (C2), 157.8 (ArC), 163.8 (C4), 175.9 (CH3COO); HRMS (ESI) m/z

+ Calcd. for C36H30O10Na (M + Na) 645.1731. Found 645.1729; Anal. Calcd. for

1 C36H30O10· /2H2O: C, 68.46; H 4.91. Found: C 68.66; H 4.93.

Further elution of the column gave compound 273 as a pale yellow solid (24 mg, 10%).

4’-Hydroxy-3’,3’’’,4’’’,7,7’’-pentamethoxy-6’,6’’’-biisoflavonyl (273)

M.p 265-267 °C; UV (MeOH): max 219 ( OMe 62216 cm-1M-1), 295 ( 27672 cm-1M-1) OH O 2' 8'' 5 5' O OMe nm; IR (KBr): max 3434, 1627, 1607, 2'' 2 -1 1 5''' 1507, 1441, 1270, 1202 cm ; H NMR MeO 8 O 5'' O MeO 2''' (300 MHz, CDCl ): 3.69 and 3.70 (2 × 3 OMe s, 6H, 3’ CH3O, 3’’’ CH3O), 3.85 (s, 3H, 4’’’ CH3O), 3.88 and 3.89 (2 × s, 6H, 7 CH3O, 7’’ 220 CH3O), 5.53 (brs, 1H, 4’ OH), 6.77-6.91 (m, 8H, H6, H6’’, H8, H8’’, H2’, H2’’’, H5’, H5’’’),

7.70 and 7.89 (2 × s, 2H, H2, H2’’), 7.76 (2 × d, J = 9.1 Hz, 2H, H5, H5’); 13C NMR

(75.6 MHz, CDCl3): 55.66 (CH3O), 55.74 (CH3O), 55.8 (CH3O), 99.89 (ArCH), 99.95

(ArCH), 113.6 (ArCH), 114.1 (ArCH), 114.2 (ArCH), 114.3 (ArCH), 114.4 (ArCH), 117.6

(ArCH), 118.1 (ArC), 118.2 (ArC), 122.9 (ArC), 123.8 (ArC), 124.1 (ArC), 124.5 (ArC),

127.2 (ArCH), 127.4 (ArCH), 132.5 (ArC), 132.9 (ArC), 144.3 (ArC), 146.1 (ArC), 147.5

(ArC), 148.1 (ArC), 154.2 (ArCH), 155.1 (ArCH), 157.76 (ArC), 157.81 (ArC), 163.7

+ (ArC), 175.6 (C=O), 176.1 (C=O); HRMS (ESI) m/z Calcd. for C35H28O10Na (M + Na)

631.1575. Found 631.1560; Anal. Calcd. for C35H28O10: C, 69.07; H 4.64. Found: C

68.82; H 4.94.

7,7’’-Diacetoxy-3’,3’’’,4’,4’’’-tetramethoxy-5,5’’-dimethyl-6’,6’’’-biisoflavonyl (275)

The title compound was synthesized OMe OMe following the procedure for dimer 269 Me O O OAc using isoflavone 274 (300 mg, 0.847 AcO O mmol), TTFA (253 mg, 0.466 mmol) and O Me MeO

BF3·OEt2 (0.3 mL). Chromatography OMe

(SiO2, 2% ethyl acetate/dichloromethane) gave the title compound 275 as pale yellow crystals (234 mg, 78%). M.p. 258-260 °C (from MeOH); UV (MeOH): max 214 ( 62029

-1 -1 -1 -1 -1 -1 cm M ), 245 ( 55576 cm M ), 296 ( 18152 cm M ) nm; IR (KBr): max 1773, 1648,

-1 1 1608, 1508, 1449, 1255, 1197, 1144, 1018 cm ; H NMR (300 MHz, CDCl3): 2.31 (s,

6H, 2 × CH3COO), 2.36 (s, 6H, 2 × CH3), 3.80 and 3.86 (2 × s, 12H, 4 × CH3O), 6.77 (d,

J = 2.3 Hz, 2H, H6, H6’’), 6.82 and 6.87 (2 × s, 4H, H2’, H2’’’, H5’, H5’’’), 7.02 (d, J =

13 2.3 Hz, 2H, H8, H8’’), 7.50 (s, 2H, H2, H2’’); C NMR (75.6 MHz, CDCl3): 21.0 (CH3),

22.8 (CH3COO), 55.8 and 55.9 (2 × CH3O), 108.8 (ArCH), 114.2 (ArCH), 114.3 (ArCH),

120.6 (ArC), 121.0 (ArCH), 122.9 (ArC), 124.9 (ArC), 132.6 (ArC), 143.1 (ArC), 147.7

(ArC), 148.5 (ArC), 152.8 (ArC), 153.5 (C2), 158.0 (ArC), 168.3 (C4), 177.7 (COO);

221 + HRMS (ESI) m/z Calcd. for C40H34O12Na (M + Na) 729.1943. Found 729.1943; Anal.

1 Calcd. for C40H34O12· /2H2O: C, 67.13; H 4.93. Found: C 67.25; H 5.13.

7,7’’,8,8’’’-Tetraacetoxy-3’,3’’’,4’,4’’’-tetramethoxy-6’,6’’’-biisoflavonyl (277)

The title compound was synthesized OMe OMe following the procedure for dimer 269 O OAc O OAc using diacetoxyisoflavone 276 (350 mg,

0.87 mmol), TTFA (238 mg, 0.44 mmol) AcO O OAc O MeO and BF3·OEt2 (0.5 mL) except that the OMe reaction was carried out at 10 °C instead of 0 °C. Chromatography (SiO2, 2% ethyl acetate/dichloromethane) gave the title compound 277 as off-white crystals (230 mg,

-1 -1 -1 -1 65%). M.p. 167 C; UV (CHCl3): max 244 ( 40991 cm M ), 249 ( 39508 cm M ), 294

-1 -1 ( 17467 cm M ) nm; IR (KBr): max 1781, 1653, 1506, 1447, 1256, 1195, 1168, 1031

-1 1 cm ; H NMR (300 MHz, CDCl3): 2.34 and 2.37 (2 × s, 12H, 4 × CH3COO), 3.71 and

3.85 (2 × s, 12H, 4 × CH3O), 6.79 and 6.82 (2 × s, 4H, H2’, H2’’’, H5’, H5’’’), 7.14 (d, J =

9.0 Hz, 2H, H6, H6’’), 7.82 (d, J = 9.0 Hz, 2H, H5, H5’’), 7.86 (s, 2H, H2, H2’’); 13C NMR

(75.6 MHz, CDCl3): 20.2 and 20.6 (2 × CH3COO), 55.8 (2 × CH3O), 114.1 (ArCH),

114.3 (ArCH), 119.8 (ArCH), 122.1 (ArC), 122.8 (ArC), 123.5 (ArCH), 125.1 (ArC),

131.1 (ArC), 132.7 (ArC), 146.3 (ArC), 147.7 (ArC), 148.6 (ArC), 149.3 (ArC), 154.6

(ArCH), 167.0 (C=O), 167.4 and 175.3 (COO); HRMS (ESI) m/z Calcd. for C42H34O16Na

+ (M + Na) 817.1739. Found 817.1729. Anal. Calcd. for C42H34O16·H2O: C, 62.07; H 4.46.

Found: C 62.01; H 4.78.

222 3’,3’’’,4’,4’’,7,7’’-Hexamethoxy-8,8’’-dimethyl-6’,6’’’-biisoflavonyl (279)

The title compound was synthesized OMe OMe following the procedure for dimer 269 O Me O OMe using trimethoxyisoflavone 278 (470 mg,

1.44 mmol), TTFA (392 mg, 0.72 mmol) MeO O Me O MeO and BF3·OEt2 (0.5 mL). Chromatography OMe

(SiO2, 2% ethyl acetate/dichloromethane) gave the title compound 279 as off-white crystals (345 mg, 74%). M.p. 301-303 °C (from MeOH); UV (CHCl3): max 245 ( 56885

-1 -1 -1 -1 -1 -1 cm M ), 252 ( 54850 cm M ), 294 ( 29035 cm M ) nm; IR (KBr): max 1635, 1623,

-1 1 1601, 1505, 1271, 1250, 1197, 1170, 1100, 785 cm ; H NMR (300 MHz, CDCl3):

2.27 (s, 6H, 2 × CH3), 3.60, 3.84 and 3.95 (3 × s, 18H, 6 × CH3O), 6.86 and 6.78 (2 × s,

4H, H2’, H2’’’, H5’, H5’’’), 7.93 (d, J = 8.7 Hz, 2H, H6, H6’’), 7.94 (d, J = 8.7 Hz, 2H, H5,

13 H5’’), 8.06 (s, 2H, H2, H2’’); C NMR (75.6 MHz, CDCl3): 8.0 (CH3), 55.6, 55.7 and

56.0 (3 × CH3O), 108.4 (ArCH), 113.9 (ArC), 114.0 (ArCH), 114.2 (ArCH), 118.1 (ArC),

123.3 (ArC), 124.4 (ArC), 124.4 (ArCH), 133.4 (ArC), 147.4 (ArC), 148.0 (ArC), 155.1

(ArCH), 155.3 (ArC), 161.1 (ArC), 173.7 (C=O); HRMS (ESI) m/z Calcd. for

+ C38H34O10Na (M + Na) 673.2044. Found 673.2032; Anal. Calcd. for C38H34O10: C,

70.14; H, 5.27. Found: C, 69.95; H, 5.39.

7,7’’-Diacetoxy-3’,3’’’,4’,4’’’-tetramethoxy-8,8’’-dimethyl-6’,6’’’-biisoflavonyl (281)

The title compound was synthesized OMe OMe following the procedure for dimer 269 O Me O OAc using isoflavone 280 (500 mg, 1.41 AcO O mmol), TTFA (383 mg, 0.70 mmol) and Me O MeO

BF3·OEt2 (1 mL). Chromatography (SiO2, OMe

2% Ethyl acetate/dichloromethane) gave the title compound 281 as a pale yellow solid

-1 -1 (380 mg, 76%). M.p. 158 °C (from EtOH); UV (CHCl3): max 245 ( 54137 cm M ), 293

-1 -1 -1 ( 23362 cm M ) nm; IR (KBr): max 1766, 1646, 1603, 1506, 1205, 1183, 1053 cm ; 223 1 H NMR (300 MHz, CDCl3): 2.26 (s, 6H, 2 × CH3), 2.37 (s, 6H, 2 × CH3COO), 3.71 and 3.85 (2 × s, 12H, 4 × CH3O), 6.82 and 6.85 (2 × s, 4H, H2’, H2’’’, H5’, H5’’’), 7.01

(d, J = 8.8 Hz, 2H, H6, H6’’), 7.81 (d, J = 8.8 Hz, 2H, H5, H5’’), 7.95 (s, 2H, H2, H2’’);

13 C NMR (75.6 MHz, CDCl3): 9.1 (CH3), 20.7 (CH3COO), 55.8 (4 × CH3O), 114.1

(ArCH), 114.3 (ArCH), 119.4 (ArCH), 119.9 (ArC), 122.1 (ArC), 122.68 (ArC), 124.0

(ArCH), 124.5 (ArC), 132.9 (ArC), 147.6 (ArC), 148.3 (ArC), 152.6 (ArC), 155.1 (ArC),

155.2 (ArCH), 168.4 (C=O), 176.3 (COO); HRMS (ESI) m/z Calcd. for C40H34O12Na (M

+ + Na) 729.1942. Found 729.1939; Anal. Calcd. for C40H34O12·H2O: C, 66.29; H, 4.97.

Found: C, 66.42; H, 4.94.

Further elution with the same solvent system gave monodemethylated dimer 282 as a pale yellow solid (110 mg, 22%).

7,7’’-Diacetoxy-4’-hydroxy-3’,3’’’,4’’’-trimethoxy-8,8’’-dimethyl-6’,6’’’-biisoflavonyl

(282)

M.p. 260-262 °C; UV (CHCl3): max 245 ( OMe OH 43859 cm-1M-1), 294 ( 17161 cm-1M-1) O Me O OAc nm; IR (KBr): max 3433, 1736, 1647, AcO O 1636, 1507, 1203, 1183, 1152, 1054 cm-1; Me O MeO 1 OMe H NMR (300 MHz, CDCl3): 2.27 (s, 6H,

2 × CH3), 2.37 (s, 6H, 2 × CH3COO), 3.67 (s, 6H, 3’ CH3O, 3’’’ CH3O), 3.84 (s, 3H, 4’’’

CH3O), 5.52 (brs, 1H, 4’ OH), 6.78 and 6.79 (2 × s, 2H, H2’, H2’’’), 6.84 (s, 1H, H5’’’),

6.87 (s, 1H, H5’), 7.01 (d, J = 8.6 Hz, 1H, H6’’), 7.04 (d, J = 8.6 Hz, 1H, H6), 7.84 (d, J

= 8.6 Hz, 1H, H5’’), 7.92 (d, J = 8.6 Hz, 1H, H5), 7.93 (s, 1H, H2’’), 8.12 (s, 1H, H2); 13C

NMR (75.6 MHz, CDCl3): 9.05 (CH3), 9.09 (CH3), 20.7 (CH3COO), 55.76 (CH3O),

55.84 (CH3O), 113.5 (ArCH), 114.1 (ArCH), 114.3 (ArCH), 117.5 (ArCH), 119.4 (ArCH),

119.8 (ArC), 120.0 (ArC), 122.05 (ArC), 122.13 (ArC), 122.62 (ArC), 123.5 (ArC), 124.0

(ArCH), 124.1 (ArCH), 124.7 (ArC), 125.0 (ArC), 132.7 (ArC), 133.2 (ArC), 144.4 (ArC),

224 146.1 (ArC), 147.6 (ArC), 148.1 (ArC), 152.6 (ArC), 154.6 (ArC), 155.19 (ArC), 155.22

(ArCH), 155.5 (ArCH), 168.36 (C=O), 168.43 (C=O), 176.0 (COO), 176.5 (COO);

+ HRMS (ESI) m/z Calcd. for C39H32O12Na (M + Na) 715.1786. Found 715.1767; Anal.

1 Calcd. for C39H32O12· /2H2O: C, 66.76; H, 4.70. Found: C, 66.75; H, 4.77.

2’-Hydroxy-4’,6’-dimethoxyacetophenone (288) O

To a stirred mixture of 2’,4’,6’-trihydroxyacetophenone 192 (2.5 g, MeO OH

15 mmol), K2CO3 (4.1 g, 28 mmol) and acetone (45 mL) was added dimethyl sulfate (2.7 mL, 28 mmol) and the mixture was refluxed OMe for 5 h. The reaction mixture was cooled to r.t. and diluted with water (50 mL). The solid was filtered, washed with water and air dried. The title compound 288 was obtained as a pale yellow solid (2.1 g, 72%). M.p. 75-77 °C (from hexane), lit.287 75-77 °C; 1H NMR

(300 MHz, CDCl3): 2.60 (s, 3H, CH3CO), 3.81 (s, 3H, CH3O), 3.84 (s, 3H, CH3O),

5.90 (d, J = 2.3 Hz, 1H, H3’), 6.05 (d, J = 2.3 Hz, 1H, H5’), 14.01 (s, 1H, OH).

2’-Hydroxy-3,4,4’,6’-tetramethoxychalcone (290) OMe O A stirred mixture of acetophenone 288 (0.49 g, 2.5 mmol), 3,4-dimethoxybenzaldehyde 289 (0.43 g, 2.59 OMe MeO OH mmol) and ethanol (5 mL) was heated to 50 °C. A OMe solution of NaOH (2.0 g, 50% w/w, 25 mmol) was added in one lot and the heating was continued for further 30 min. The mixture was cooled to r.t. and acidified to pH 5 using

2M hydrochloric acid. The precipitated product was filtered, washed with water and air dried (0.75 g, 87%). This was used in the next step without further purification. M.p.

288 1 155-157 °C (from ether), lit. 154-156 °C; H NMR (300 MHz, CDCl3): 3.83 (s, 3H,

CH3O), 3.90 (s, 3H, CH3O), 3.92 (s, 3H, CH3O), 3.93 (s, 3H, CH3O), 5.95 and 6.10 (2 × d, J = 2.3 Hz, 2H, H3’, H5’), 6.89 (d, J = 8.3 Hz, 1H, H5), 7.12 (d, J = 1.5 Hz, 1H, H2),

7.21 (dd, J = 1.5, 8.3 Hz, 1H, H6), 7.75 and 7.82 (2 × d, J = 15.4 Hz, 2H, H, H), 14.38

13 (bs, 1H, OH); C NMR (75.6 MHz, CDCl3): 55.4 (CH3O), 55.7 (CH3O), 55.8 (CH3O),

225 91.2 (ArCH), 93.7 (ArCH), 106.3 (ArC), 110.4 (ArCH), 111.1 (ArCH), 122.5 (ArCH),

125.3 (ArCH), 128.5 (ArC), 142.5 (ArCH), 149.1 (ArC), 151.0 (ArC), 162.3 (ArC), 166.0

(ArC), 168.3 (ArC), 192.0 (C=O).

3’,4’,5,7-Tetramethoxyflavone (291)

A mixture of chalcone 290 (750 mg, 2.18 mmol) and OMe O DMSO (7.5 mL) was heated to 150 °C under an argon atmosphere. Iodine crystals (30 mg, 0.12 mmol) were OMe MeO O added in one lot and the heating was continued further OMe for 30 min. The mixture was cooled to r.t. and diluted with water (75 mL). Potassium metabisulfite solution (5% w/w) was added dropwise till the colour of iodine was just discharged. The solid was filtered, washed with water (25 mL × 2) and air dried (610 mg, 81%). M.p. 189-190 °C (from dichloromethane), lit.288 190-192 °C; 1H NMR (300

MHz, CDCl3): 3.92 (s, 3H, CH3O), 3.95 (s, 3H, CH3O), 3.96 (s, 3H, CH3O), 3.97 (s,

3H, CH3O), 6.37 (d, J = 2.3 Hz, 1H, H6), 6.56 (d, J = 2.3 Hz, 1H, H8), 6.68 (s, 1H, H3),

6.96 (d, J = 8.7 Hz, 1H, H5’), 7.32 (d, J = 2.3 Hz, 1H, H2’), 7.51 (dd, J = 2.3, 8.7 Hz,

13 1H, H6’); C NMR (75.6 MHz, CDCl3): 55.7 (CH3O), 55.9 (CH3O), 56.0 (CH3O), 56.3

(CH3O), 92.8 (ArCH), 96.0 (ArCH), 107.8 (ArCH), 108.5 (ArCH), 108.9 (ArC), 111.0

(ArCH), 119.4 (ArCH), 123.9 (ArC), 149.1 (ArC), 151.7 (ArC), 159.7 (ArC), 160.6 (ArC),

160.7 (ArC), 163.9 (ArC), 177.6 (C=O).

Attempted oxidative dimerization of tetramethoxyflavone 291

A stirred solution of flavone 291 (300 mg, 0.88 mmol) OMe O in dichloromethane (11 mL) was cooled to 5 °C under OMe an argon atmosphere. TTFA (520 mg, 0.96 mmol) MeO O I OMe was added followed by addition of BF3·OEt2 (0.3 mL).

The mixture was stirred at 5 °C for 1 h. TLC analysis showed the absence of any new product. The temperature was raised to r.t. when formation of new product was

226 observed on TLC. However, the progress of the reaction ceased after 3 h. The reaction was quenched by addition of aq. KI (10%, in 10 mL water) followed by stirring for 30 min. Sodium metabisulfite solution (500 mg dissolved in minimum amount of water) was added and stirring was continued further for 10 min. The yellow precipitate was filtered and washed with dichloromethane (10 mL × 3). The filtrate was collected and the organic layer was separated. The aqueous layer was extracted with dichloromethane (10 mL). The combined organic layer was dried with anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 2% ethyl acetate/dichloromethane) gave a yellow compound which was identified as 8- iodoluteolin tetramethyl ether 293. M.p. 263-264 °C (from pyridine), lit.289 268-270 °C;

1 H NMR (300 MHz, CDCl3): 3.96 (s, 3H, CH3O), 3.99 (s, 3H, CH3O), 4.03 (s, 6H, 2 ×

CH3O), 6.43 (s, 1H, H6), 6.70 (s, 1H, H3), 6.98 (d, J = 8.6 Hz, 1H, H5’), 7.64 (dd, J =

13 1.9, 8.6 Hz, 1H, H6’), 7.66 (d, J = 1.9 Hz, 1H, H2’); C NMR (75.6 MHz, CDCl3):

55.98 (CH3O), 56.04 (CH3O), 56.5 (CH3O), 56.7 (CH3O), 64.8 (C8), 91.7 (ArCH), 106.9

(ArCH), 109.2 (ArCH), 109.8 (ArC), 111.1 (ArCH), 119.9 (ArCH), 123.5 (ArC), 149.2

(ArC), 151.8 (ArC), 157.4 (ArC), 160.9 (ArC), 161.9 (ArC), 162.5 (ArC), 177.4 (C=O).

2’-Hydroxy-3,4-dimethoxychalcone (295)290,291

A stirred mixture of 2-hydroxyacetophenone 294 (408 mg, 3 O mmol), 3,4-dimethoxybenzaldehyde 289 (498 mg, 3 mmol) OH and ethanol (6 mL) was heated to 50 °C. A solution of OMe NaOH (2.4 g, 50% w/w, 30 mmol) was added in one lot and OMe the heating was continued further for 30 min. The mixture was cooled to r.t. and acidified to pH 5 using 2M hydrochloric acid. The precipitated product was filtered, washed with water and air dried (600 mg, 70%). This was used in the next step without

291 1 further purification. M.p. 115-117 °C, lit. 117 °C; H NMR (300 MHz, CDCl3): 3.94,

(s, 3H, 4 CH3O), 3.96 (s, 3H, 3 CH3O), 6.91 (d, J = 8.3 Hz, 1H, H5), 6.94 (ddd, J = 0.9,

7.7, 8.0 Hz, 1H, H5’), 7.02 (dd, J = 0.9, 8.3 Hz, 1H, H3’), 7.16 (d, J = 1.9 Hz, 1H, H2),

227 7.27 (dd, J = 1.9, 8.3 Hz, 1H, H6), 7.49 (ddd, J = 1.4, 7.7, 8.3 Hz, 1H, H4’), 7.52 (d, J =

15.4 Hz, 1H, H), 7.89 (d, J = 15.4 Hz, 1H, H), 7.93 (dd, J = 1.4, 8.0 Hz, 1H, H6’),

12.91 (s, 1H, 2’ OH).

3’,4’-Dimethoxyflavone (296) O A suspension of chalcone 295 (450 mg, 1.6 mmol) in

DMSO (4.5 mL) was immersed in a preheated oil bath at O

150 C. Iodine crystals (16 mg) were added in one lot and OMe OMe the mixture was heated under an argon atmosphere for 30 min. The mixture was cooled to r.t. and slowly diluted by dropwise addition of water (50 mL). Sodium metabisulfite solution was added dropwise till the colour of iodine was just discharged. The solid was filtered, washed with water (25 mL × 2) and air dried (400

292 1 mg, 88%). M.p. 154-155 °C, lit. 155-156 °C; H NMR (300 MHz, CDCl3): 3.96 (s,

3H, 3’ CH3O), 3.98 (s, 3H, 4’ CH3O), 6.78 (s, 1H, H3), 6.98 (d, J = 8.4 Hz, H5’), 7.38 (d,

J = 2.4 Hz, 1H, H2’), 7.43 (dd, J = 2.4, 8.4 Hz, 1H, H6’), 7.54 (m, 2H, H6, H8), 7.68

(ddd, J = 1.6, 7.1, 8.4 Hz, 1H, H7), 8.22 (dd, J = 1.6, 8.1 Hz, 1H, H5).

4’,7-Dihydroxy-3’-iodoisoflavone (246)

To a suspension of 4’,7-diacetoxyisoflavone 310 (2.0 g, OH O 5.91 mmol) in methanol (100 mL) was added powdered I

KOH (6.0 g, 107 mmol) and the mixture was stirred HO O under argon for 30 min. A solution of iodine (2.3 g, 10 mmol) in methanol (40 mL) was added dropwise over 1 h and the mixture was stirred at ambient temperature for 1 h.

Again a solution of iodine (0.22 g, 0.86 mmol) in methanol (20 mL) was added over 30 min and stirring was continued further for 30 min. The mixture was poured into water

(400 mL) and acidified to pH 2 using conc. hydrochloric acid. The precipitated solid was filtered, washed with water and air dried (2.0 g, 88%). M.p. >300°C °C; IR (KBr) max:

2600-3500 (br), 1623, 1577, 1457, 1419, 1264, 1195, 1099, 784 cm-1; 1H NMR (300 228 MHz, acetone-d6): 6.89 (d, J = 2.3 Hz, 1H, H8), 6.99 (d, J = 8.3 Hz, 1H, H5’), 6.99

(dd, J = 2.3, 8.7 Hz, 1H, H6), 7.48 (dd, J = 2.3, 8.3 Hz, 1H, H6’), 8.01 (d, J = 2.3 Hz,

1H, H2’), 8.04 (d, J = 8.7 Hz, 1H, H5), 8.21 (s, 1H, H2), 9.50 (bs, 2H, 2 × OH); 13C NMR

(75.6 MHz, acetone-d6): 83.0 (ArC), 102.1 (ArCH), 114.3 (ArCH), 115.0 (ArCH), 117.1

(ArC), 122.8 (ArC), 125.2 (ArC), 127.4 (ArCH), 130.1 (ArCH), 139.3 (ArCH), 152.8

(ArCH), 156.5 (ArC), 157.9 (ArC), 162.7 (ArC), 170.5 (C=O); HRMS (ESI) m/z Calcd.

+ for C15H9O4INa (M + Na) , 402.9438. Found 402.9440.

4’,7-Dimethoxy-3’-iodoisoflavone (311)

To a stirred suspension of iodoisoflavone 246 (2.0 g, OMe O

5.3 mmol) in DMSO (6 mL) was added a solution of I

KOH (0.9 g, 16 mmol) in water (1 mL) under an MeO O argon atmosphere. The mixture was stirred for 15 min and then methyl iodide (3.0 g,

21.1 mmol) was added in one lot. The stirring was continued further for 2 h. The mixture was poured into water (200 mL) and the solid was filtered, washed with water and air dried. Iodoisoflavone 311 was obtained as a white solid (1.2 g, 55%). M.p. 190-

192 °C (from dichloromethane/hexane); IR (KBr) max: 1626, 1593, 1491, 1439, 1283,

-1 1 1254, 1044, 802 cm ; H NMR (300 MHz, CDCl3): 3.91 (s, 6H, 2 × CH3O), 6.85 (d, J

= 2.6 Hz, 1H, H8), 6.88 (d, J = 8.7 Hz, 1H, H5’), 6.99 (dd, J = 2.6, 9.1 Hz, 1H, H6), 7.57

(dd, J = 1.9, 8.7 Hz, 1H, H6’), 7.91 (s, 1H, H2), 7.94 (d, J = 9.0 Hz, 1H, H2’), 8.19 (d, J

13 = 9.1 Hz, 1H, H5); C NMR (75.6 MHz, CDCl3): 55.8 (CH3O), 56.4 (CH3O), 85.7

(ArC), 100.1 (ArCH), 110.6 (ArCH), 114.6 (ArCH), 118.2 (ArC), 123.5 (ArC), 126.1

(ArC), 127.7 (ArCH), 130.3 (ArCH), 139.4 (ArCH). 152.2 (ArCH), 157.9 (ArC), 158.0

+ (ArC), 164.0 (ArC), 175.4 (C=O); HRMS (ESI) m/z Calcd. for C17H13O4INa (M + Na) ,

430.9751. Found 430.9752; Anal. Calcd. for C17H13IO4: C, 50.02; H, 3.21. Found: C,

50.10; H, 3.30.

229 4’,7-Dimethoxy-3’-(2-(trimethylsilyl)ethynyl)isoflavone (312)

To a mixture of iodoisoflavone 311 (610 mg, 1.5 O OMe mmol), CuI (5 mg, 0.025 mmol), PdCl2(PPh3)2 (10 SiMe3 mg, 0.015 mmol), triethylamine (3 mL) and DMF MeO O

(2 mL) was added ethynyltrimethylsilane 308 (316 L, 2.24 mmol). The mixture was heated under an argon atmosphere at 90 °C for 5 h. TLC analysis showed the presence of unreacted isoflavone 311. More ethynyltrimethylsilane 308 (158 L, 1.12 mmol) and PdCl2(PPh3)2 (10 mg, 0.015 mmol) were added and the reaction was continued further for 2 h. Triethylamine was distilled off under vacuum and the mixture was diluted with water (30 mL). The solid was filtered, washed with water (25 mL) and air dried. Chromatography (SiO2, 20% ethyl acetate/hexane) gave isoflavone 312 as white crystals (320 mg, 56%). M.p. 193-194 °C (from dichloromethane/hexane); UV

-1 -1 -1 -1 -1 -1 (MeOH): max 248 ( 63637 cm M ), 256 ( 56435 cm M ) sh, 302 ( 21143 cm M ) nm; IR (KBr): max 3078, 2958, 2154, 1634, 1606, 1502, 1441, 1264, 1250, 1025, 862,

-1 1 840 cm ; H NMR (300 MHz, CDCl3): 0.25 (s, 9H, Si(CH3)3), 3.90 (s, 6H, 2 × CH3O),

6.83 (d, J = 2.6 Hz, 1H, H8), 6.90 (d, J = 8.6 Hz, 1H, H5’), 6.97 (dd, J = 2.6, 9.0 Hz, 1H,

H6), 7.54 (dd, J = 2.3, 8.6 Hz, 1H, H6’), 7.60 (d, J = 2.3 Hz, 1H, H2’), 7.91 (s, 1H, H2),

13 8.18 (d, J = 9.0 Hz, 1H, H5); C NMR (75 .6 MHz, CDCl3): -0.01 (Si(CH3)3), 55.7

(CH3O), 55.9 (CH3O), 98.6 (-C), 100.0 (ArCH), 100.9 (ArC), 110.7 (ArCH), 112.4

(ArCH), 114.5 (ArC), 118.2 (ArC), 124.01 (ArC), 124.03 (ArC), 127.7 (ArCH), 130.7

(ArCH), 134.2 (ArCH), 152.1 (ArCH), 157.8 (ArC), 160.1 (ArC), 163.9 (ArC), 175.5

+ (C=O); HRMS (ESI) m/z Calcd. for C22H22O4NaSi (M + Na) 401.1180. Found

401.1174; Anal. Calcd. for C22H22O4Si: C, 69.84; H, 5.82. Found: C, 69.90; H, 6.02.

4’,7-Dimethoxy-3’-ethynylisoflavone (313)

A mixture of isoflavone 312 (310 mg, 0.82 mmol) O OMe H and K2CO3 (30 mg, 0.2 mmol) in methanol (10 mL)

MeO O

230 was stirred overnight at r.t. Solvent was evaporated under vacuum and the residue was diluted with water (25 mL). The solid was filtered, washed with water (15 mL) and air dried. The title compound 313 was obtained as an off-white solid (240 mg, 95%). M.p.

-1 -1 -1 -1 190-192 °C; UV (MeOH): max 238 ( 47234 cm M ), 265 ( 28653 cm M ) sh, 299 (

-1 -1 16563 cm M ) nm; IR (KBr): max 3285, 2328, 1632, 1602, 1500, 1440, 1263, 1249,

-1 1 1129, 1018, 825, 549 cm ; H NMR (300 MHz, CDCl3): 3.31 (s, 1H, CH), 3.91 (s,

3H, CH3O), 3.93 (s, 3H, CH3O), 6.85 (d, J = 2.3 Hz, 1H, H8), 6.96 (d, J = 9.0 Hz, 1H,

H5’), 6.99 (dd, J = 2.3, 8.7 Hz, 1H, H6), 7.60 (dd, J = 2.3, 9.0 Hz, 1H, H6’), 7.61 (d, J =

2.3 Hz, 1H, H2’), 7.92 (s, 1H, H2), 8.19 (d, J = 8.7 Hz, H5); 13C NMR (75.6 MHz,

CDCl3): 55.7 (CH3O), 55.9 (CH3O), 79.7 (-C), 81.3 (CH), 100.1 (ArCH), 110.6

(ArCH), 111.3 (ArC), 114.6 (ArCH), 118.2 (ArC), 124.0 (ArC), 124.2 (ArC), 127.7

(ArCH), 131.1 (ArCH). 134.2 (ArCH), 152.2 (ArCH), 157.9 (ArC), 160.4 (ArC), 164.0

+ (ArC), 175.5 (C=O); HRMS (ESI) m/z Calcd. for C19H14O4Na (M + Na) 329.0784.

Found 329.0783; Anal. Calcd. for C19H14O4: C, 74.50; H, 4.60. Found: C, 74.13; H,

4.79.

1,2-Bis-(4’,7-dimethoxyisoflavone-3’-yl)ethyne (314)

A mixture of isoflavone 313 5' O 6' OMe 5 8'' (100 mg, 0.32 mmol), 6 2'' O OMe 2' 2''' isoflavone 311 (130 mg, 0.32 2 6'' MeO 8 O 5'' 6''' O MeO mmol) and triethylamine (2 mL) 5''' in DMF (2 mL) was heated at 80 °C for 30 min with the headspace being continuously purged with argon. CuI (5 mg, 0.025 mmol) and PdCl2(PPh3)2 (5 mg, 0.0075 mmol) were added and heating was continued for 11 h. The mixture was cooled to r.t. and diluted with hydrochloric acid (2M, 10 mL) followed by water (25 mL). The solid was filtered, washed with water (25 mL) and air dried. The product was found to be insoluble in all solvents and therefore it was purified by leaching with THF. The title compound 314 was obtained as a grey solid (145 mg, 75%). M.p. 320-321 °C; UV

231 spectrum could not be obtained due to extremely low solubility. IR (KBr): max 3076,

2832, 1629, 1604, 1508, 1440, 1273, 1240, 1153, 1020, 856, 823 cm-1; 1H NMR (300

MHz, CDCl3): 3.87 (s, 6H, 2 × CH3O), 3.88 (s, 6H, 2 × CH3O), 7.08 (dd, J = 2.6, 9.0

Hz, 2H, H6, H6’’), 7.15 (d, J = 8.7 Hz, 2H, H5’, H5’’’), 7.16 (d, J = 2.6 Hz, 2H, H8, H8’’),

7.59 (dd, J = 2.3, 8.7 Hz, 2H, H6’, H6’’’), 7.67 (d, J = 2.3 Hz, 2H, H2’, H2’’’), 8.02 (d, J =

13 9.0 Hz, 2H, H5, H5’’), 8.51 (s, 2H, H2, H2’’); C NMR (150 MHz, DMSO-d6, 26000 scans ): 56.8 (CH3O), 57.0 (CH3O), 101.5 (ArCH), 112.3 (ArCH), 115.8 (ArC), 116.9

(ArC), 118.4 (ArCH), 123.4 (ArC), 124.0 (ArC), 125.0 (ArC), 127.8 (ArCH), 131.6

(ArCH), 134.1 (ArCH), 154.9 (ArCH), 158.4 (ArC), 160.1 (ArC), 164.7 (ArC), 175.5

+ (C=O); HRMS (ESI) m/z Calcd. for C36H26O8Na (M + Na) 609.1511. Found 609.1524;

Anal. Calcd. for C36H26O8·H2O: C, 71.52; H, 4.67. Found: C, 72.26; H, 4.58.

3-Iodo-4-methoxybenzaldehyde (319) OMe To a solution of 4-methoxybenzaldehyde 318 (6.1 g, 44.8 mmol) in acetic I acid (42 mL) was added iodine monochloride (4.7 mL, 93 mmol). The mixture was heated at 80 °C for 24 h, cooled to r.t. and poured into a CHO solution of potassium metabisulfite (5.0 g, 22.6 mmol) in water (250 mL). The suspension was stirred for 10 min, filtered, washed with water and air dried.

Iodobenzaldehyde 319 was obtained as a light pink solid (10.5 g, 89%). M.p. 105-107

293 1 °C, lit. 106-107 °C; H NMR (300 MHz, CDCl3): 3.96 (s, 3H, CH3O), 6.91 (d, J = 8.3

Hz, 1H, H5), 7.84 (dd, J = 2.3, 8.3 Hz, 1H, H6), 8.29 (d, J = 2.3 Hz, 1H, H2), 9.81 (s,

13 1H, CHO); C NMR (75.6 MHz, CDCl3): 56.7 (CH3O), 86.3 (ArC), 110.4 (ArCH),

131.3 (ArC), 132.0 (ArCH), 141.0 (ArCH), 162.5 (ArC), 189.4 (CHO).

1,2-Bis-(2-methoxy-5-formylphenyl)ethyne (322) OMe OMe A solution of 3-iodo-4-methoxybenzaldehyde 319 (262 mg, 1 mmol) in triethylamine (2 mL) and DMF (2 mL) was

CHO CHO

232 deoxygenated by heating at 80 °C for 30 min with the headspace being purged continuously with argon. The mixture was cooled to r.t. and ethynyltrimethylsilane 308

(0.17 mL, 1.2 mmol), PdCl2(PPh3)2 (20 mg, 0.03 mmol) and CuI (10 mg, 0.05 mmol) were added. Heating was continued at 80 °C for 1.5 h. DBU (0.91 mL, 6 mmol) and another equivalent of aldehyde 319 (262 mg, 1 mmol) was added and the heating was continued further for 1.5 h. The mixture was cooled to r.t. and poured into hydrochloric acid (2M, 50 mL) and stirred for 10 min. The solid was filtered, washed with water and air dried. Chromatography (SiO2, 30% hexane/dichloromethane) gave dialdehyde 322

-1 - (251 mg, 86%). M.p. 209-211 °C (from MeOH); UV (MeOH): max 263 ( 67931 cm M

1 -1 -1 -1 -1 ), 304 ( 24235 cm M ) sh, 328 ( 19352 cm M ) nm; IR (KBr): max 2842, 2752,

1674, 1597, 1500, 1290, 1273, 1244, 1170, 1139, 1019, 822 cm-1; 1H NMR (300 MHz,

CDCl3): 4.02 (s, 6H, 2 × CH3O), 7.03 (d, J = 8.7 Hz, 2H, H3, H3’), 7.86 (dd, J = 2.3,

8.7 Hz, 2H, H4, H4’), 8.05 (d, J = 2.3 Hz, 2H, H6, H6’), 9.89 (s, 2H, 2 × CHO); 13C NMR

(75.6 MHz, CDCl3): 56.3 (CH3O), 89.3 (CC), 110.7 (ArCH), 113.2 (ArC), 129.5 (ArC),

131.9 (ArCH), 135.5 (ArCH), 164.4 (ArC), 190.1 (CHO); HRMS (ESI) m/z Calcd. for

+ 1 C18H14O4Na (M + Na) 317.0784. Found 317.0782; Anal. Calcd. for C18H14O4· /3H2O: C,

72.0; H, 4.88. Found: C, 72.11; H, 4.73.

1,2-Bis-(4’,7-dimethoxyisoflavone -3’-yl)ethyne (314) (One-pot procedure)

A solution of iodoflavone 311 O OMe (243 mg, 0.6 mmol) in O OMe triethylamine (3 mL) and DMF MeO O O (3 mL) was deoxygenated by MeO heating at 80 °C for 30 min with the headspace being purged continuously with argon.

The mixture was quickly cooled to r.t. and ethynyltrimethylsilane 308 (0.1 mL, 0.7 mmol), PdCl2(PPh3)2 (20 mg, 0.03 mmol) and CuI (7 mg, 0.03 mmol) were added.

Heating was continued at 80 °C for 1.5 h. DBU (0.54 mL, 3.6 mmol) and another equivalent of isoflavone 311 (243 mg, 0.6 mmol) were added and the heating was

233 continued at 80 °C for another 1.5 h and then at 100 °C for 30 min. The mixture was cooled to r.t., poured into a mixture of hydrochloric acid (2M, 50 mL) and ethyl acetate

(25 mL) and stirred for 10 min. The solid was filtered, washed with water (25 mL) and air dried (260 mg, 75%). Purification was done by leaching with THF. M.p. 318-320 °C;

1 H NMR (300 MHz, CDCl3): 3.87 (s, 6H, 2 × CH3O), 3.88 (s, 6H, 2 × CH3O), 7.08 (dd,

J = 2.6, 9.0 Hz, 2H, H6, H6’’), 7.15 (d, J = 8.7 Hz, 2H, H5’, H5’’’), 7.16 (d, J = 2.6 Hz,

2H, H8, H8’’), 7.59 (dd, J = 2.3, 8.7 Hz, 2H, H6’, H6’’’), 7.67 (d, J = 2.3 Hz, 2H, H2’,

H2’’’), 8.02 (d, J = 9.0 Hz, 2H, H5, H5’’), 8.51 (s, 2H, H2, H2’’).

2’-Hydroxy-3-iodo-4-methoxychalcone (323)

To a solution 2’-hydroxyacetophenone 294 (2.31 g, 17 O mmol) and 3-iodo-4-methoxybenzaldehyde 319 (4.50 g, I OH 17.17 mmol) in 95% ethanol (180 mL) was added a solution OMe of KOH (36.0 g, 642 mmol) in water (24 mL). The mixture was stirred at ambient temperature for 30 min and then left at r.t. for 3 days. The mixture was cooled to 15 °C and acidified to pH 4 by addition of hydrochloric acid (2M, ~350 mL). The precipitated product was filtered, washed with water (50 mL) and air dried. Recrystallization from ethanol gave chalcone 323 as a yellow solid (3.83 g, 60%). M.p. 165-167 °C (from

294 1 EtOH), lit. 169 °C; H NMR (300 MHz, CDCl3): 3.94 (s, 3H, CH3O), 6.85 (d, J = 8.3

Hz, 1H, H5), 6.95 (t, J = 7.9 Hz, 1H, H5’), 7.03 (d, J = 8.7 Hz, 1H, H3’), 7.50 (ddd, J =

1.1, 7.9, 8.7 Hz, 1H, H4’), 7.53 (d, J = 15.5 Hz, 1H, H), 7.59 (dd, J = 1.9, 8.3 Hz, 1H,

H6), 7.79 (d, J = 15.5 Hz, 1H, H), 7.92 (dd, J = 1.1, 7.9 Hz, 1H, H6’), 8.14 (d, J = 1.9

13 Hz, 1H, H2), 12.82 (s, 1H, OH); C NMR (75.6 MHz, CDCl3): 56.5 (CH3O), 86.7 (C3),

110.7 (ArCH), 118.5 (ArCH), 118.6 (ArCH), 118.8 (ArCH), 119.9 (ArC), 129.2 (ArC),

129.5 (ArCH), 131.1 (ArCH), 136.3 (ArCH), 139.0 (ArCH), 143.4 (ArCH), 160.1 (ArC),

163.5 (ArC), 193.3 (C=O).

234 3’-Iodo-4’-methoxyflavone (324) O A suspension of chalcone 323 (3.80 g, 10.0 mmol) and

DMSO (38 mL) under an argon atmosphere was immersed I O in an oil bath preheated at 160 °C. After 5 min iodine crystals OMe (0.15 g, 0.6 mmol) were added and heating was continued further for 45 min. The mixture was cooled to 60 °C and potassium metabisulfite solution (5 mL, 10% w/v) was added to the mixture. The stirring was continued for 2 min and the mixture was diluted with water (100 mL). The resulting solid was filtered, washed with water (50 mL) and air

294 1 dried (3.46 g, 91%). M.p. 189-191 °C, lit. 192 °C; H NMR (300 MHz, CDCl3): 3.95

(s, 3H, CH3O), 6.71 (s, 1H, H3), 6.91 (d, J = 8.6 Hz, 1H, H5’), 7.40 (t, J = 7.5 Hz, 1H,

H6), 7.55 (d, J = 8.3 Hz, 1H, H8), 7.69 (dd, J = 7.5, 8.3 Hz, 1H, H7), 7.86 (dd, J = 1.5,

8.6 Hz, 1H, H6’), 8.20 (d, J = 7.5 Hz, 1H, H5), 8.34 (d, J = 1.5 Hz, 1H, H2’); 13C NMR

(75.6 MHz, CDCl3): 56.6 (CH3O), 86.4 (C3’), 106.6 (ArCH), 110.7 (ArCH), 118.0

(ArCH), 123.8 (ArC), 125.2 (ArCH), 125.6 (ArCH), 125.8 (ArC), 128.0 (ArCH), 133.7

(ArCH), 137.4 (ArCH), 156.0 (ArC), 160.2 (ArC), 161.7 (ArC), 178.2 (C=O).

2’-Hydroxy-3-iodo-4,6’-dimethoxychalcone (325)

This was synthesized following the procedure for chalcone OMe O

323 using 2’-hydroxy-6’-methoxyacetophenone 77 (2.0 g, I OH 12.0 mmol), 3-iodo-4-methoxybenzaldehyde 319 (3.14 g, OMe 12 mmol), 95% ethanol (120 mL), KOH (24.0 g, 428 mmol) and water (16 mL). The title compound 325 was obtained as a yellow solid (3.2 g, 64%). M.p. 148-150 °C; UV

-1 -1 -1 -1 -1 -1 (MeOH): max 204 ( 44871 cm M ), 222 ( 24492 cm M ), 256 ( 14466 cm M ), 346

-1 -1 ( 33861 cm M ) nm; IR (KBr): max 1628, 1608, 1578, 1548, 1487, 1474, 1453, 1237,

-1 1 1204, 1088, 1045, 863, 810, 750 cm ; H NMR (300 MHz, CDCl3): 3.93 (s, 3H,

CH3O), 3.95 (s, 3H, CH3O), 6.42 and 6.61 (2 × d, J = 8.3 Hz, 2H, H3’ and H5’), 6.83 (d,

J = 8.7 Hz, 1H, H5), 7.35 (t, J = 8.3 Hz, 1H, H4’), 7.55 (dd, J = 1.9, 8.7 Hz, 1H, H6),

7.69 (d, J = 15.4 Hz, 1H, H), 7.72 (d, J = 1.5 Hz, 1H, H), 8.06 (d, J = 1.9 Hz, 1H, H2); 235 13 C NMR (75.6 MHz, CDCl3): 55.9 (CH3O), 56.4 (CH3O), 86.5 (C3), 101.5 (ArCH),

110.7 (ArCH), 110.9 (ArCH), 111.9 (ArC), 126.3 (ArCH), 130.0 (ArC), 130.5 (ArCH),

135.8 (ArCH), 139.1 (ArCH), 141.0 (ArCH), 159.6 (ArC), 160.8 (ArC), 164.8 (ArC),

+ 194.0 (C=O); HRMS (ESI) m/z Calcd. for C17H15O4INa (M + Na) 432.9907. Found 432.

9914; Anal. Calcd. for C17H15IO4: C, 49.78; H, 3.69. Found: C, 49.58; H 3.64.

3’-Iodo-4’,5-dimethoxyflavone (326) OMe O This was synthesized following the procedure for flavone I 324 using chalcone 325 (3.20 g, 7.8 mmol), DMSO (32 mL) O and iodine crystals (0.128 g, 0.5 mmol). The title compound OMe was obtained as off-white crystals (2.95 g, 92%). M.p. 210-212 °C; UV (MeOH): max

204 ( 34868 cm-1M-1), 223 ( 29577 cm-1M-1), 247 ( 25995 cm-1M-1), 325 ( 25995 cm-

1 -1 -1 1 M ); IR (KBr): max 1650, 1594, 1474, 1396, 1276, 1261, 1102, 1046, 1027 cm ; H

NMR (300 MHz, CDCl3): 3.95 (s, 3H, CH3O), 3.99 (s, 3H, CH3O), 6.61 (s, 1H, H3),

6.82 and 7.12 (2 × d, J = 8.3 Hz, 2H, H6 and H8), 6.90 (d, J = 8.7 Hz, 1H, H5’), 7.56 (t,

J = 8.3 Hz, 1H, H7), 7.82 (dd, J = 2.3, 8.7 Hz, 1H, H6’), 8.30 (d, J = 2.3 Hz, 1H, H2’);

13 C NMR (75.6 MHz, CDCl3): 56.4 (CH3O), 56.5 (CH3O), 86.3 (C3’), 106.4 (ArCH),

108.1 (ArCH), 110.0 (ArCH), 110.6 (ArCH), 114.4 (ArC), 125.5 (ArC), 127.6 (ArCH),

133.6 (ArCH), 137.2 (ArCH), 158.1 (ArC), 159.4 (ArC), 159.7 (ArC), 160.4 (ArC), 178.0

+ (C=O); HRMS (ESI) m/z Calcd. for C17H13O4INa (M + Na) 430.9751. Found 430.9745;

Anal. Calcd. for C17H13O4I: C, 50.0; H, 3.18. Found: C, 50.12; H, 3.28.

2’-Hydroxy-3-iodo-4,4’-dimethoxychalcone (327)295 O The title compound was synthesized following the procedure for chalcone 323 using 2’-hydroxy-4’- I MeO OH methoxyacetophenone 80 (2.5 g, 15 mmol), 3-iodo-4- OMe methoxybenzaldehyde 319 (3.9 g, 15 mmol), 95% ethanol (150 mL), KOH (30.0 g, 535 mmol) and water (20 mL). The title compound 327 was obtained as a yellow solid (3.1

236 1 g, 50%). M.p. 238 °C; H NMR (300 MHz, CDCl3): 3.86 (s, 3H, CH3O), 3.93 (s, 3H,

CH3O), 6.46 (d, J = 2.3 Hz, 1H, H3’), 6.48 (dd, J = 2.3, 8.7 Hz, 1H, H5’), 6.84 (d, J = 8.3

Hz, 1H, H5), 7.43 (d, J = 15.5 Hz, 1H, H), 7.57 (dd, J = 2.3, 8.3 Hz, 1H, H6), 7.75 (d, J

= 15.5 Hz, 1H, H), 7.83 (d, J = 8.7 Hz, 1H, H6’), 8.11 (d, J = 2.3 Hz, 1H, H2), 13.43 (s,

13 1H, OH); C NMR (75.6 MHz, CDCl3): 55.5 (CH3O), 56.5 (CH3O), 86.6 (C3), 101.0

(ArCH), 107.7 (ArCH), 110.7 (ArCH), 114.0 (ArC), 118.8 (ArCH), 129.4 (ArC), 130.9

(ArCH), 131.1 (ArCH), 138.8 (ArCH), 142.4 (ArCH), 159.9 (ArC), 166.1 (ArC), 166.6

(ArC), 191.4 (C=O).

3’-Iodo-4’,7-dimethoxyflavone (328)

The title compound was synthesized following the O procedure for flavone 324 using chalcone 327 (3.1 g, I MeO O 7.5 mmol), DMSO (31 mL) and iodine (125 mg, 0.5 OMe mmol). The title compound 328 was obtained as an off-white solid (2.96 g, 95%). M.p.

296 1 219-221 °C, lit. 219 °C; H NMR (300 MHz, CDCl3): 3.94 (s, 3H, 7 CH3O), 3.96 (s,

3H, 4’ CH3O), 6.66 (s, 1H, H3), 6.91 (d, J = 8.7 Hz, 1H, H5’), 6.96 (d, J = 2.3 Hz, 1H,

H8), 6.98 (dd, J = 2.3, 9.4 Hz, 1H, H6), 7.84 (dd, J = 2.3, 8.6 Hz, 1H, H6’), 8.11 (d, J =

13 9.4 Hz, 1H, H5), 8.34 (d, J = 2.3 Hz, 1H, H2’); C NMR (75.6 MHz, CDCl3): 55.8

(CH3O), 56.5 (CH3O), 86.3 (C3’), 100.3 (ArCH), 106.5 (ArCH), 110.7 (ArCH), 114.4

(ArCH), 117.6 (ArC), 125.9 (ArC), 127.0 (ArCH), 127.8 (ArCH), 137.2 (ArCH), 157.8

(ArC), 160.5 (ArC), 161.4 (ArC), 164.1 (ArC), 177.5 (C=O).

2’-Hydroxy-3-iodo-4,4’,6’-trimethoxychalcone (329)

The title compound was synthesized following the OMe O procedure for chalcone 323 using acetophenone 288 I MeO OH (0.37 g, 1.9 mmol), 3-iodo-4-methoxybenzaldehyde OMe 319 (0.50 g, 1.9 mmol), absolute ethanol (20 mL),

KOH (1.25 g, 22.3 mmol) and water (1.25 mL). The title compound 329 was obtained

237 as a yellow solid (0.50 g, 50%). M.p. 152-154 °C, lit.297 154-155 °C; 1H NMR (300 MHz,

CDCl3): 3.83 (s, 3H, CH3O), 3.92 (s, 6H, 2 × CH3O), 5.96 and 6.10 (2 × d, J = 2.6 Hz,

2H, H3’, H5’), 6.83 (d, J = 8.3 Hz, 1H, H5), 7.53 (dd, J = 2.3, 8.3 Hz, 1H, H6), 7.65 (d, J

13 = 15.5 Hz, 1H, H), 7.75 (d, J = 15.5 Hz, 1H, H), 8.04 (d, J = 2.3 Hz, 1H, H2); C NMR

(75.6 MHz, CDCl3): 55.5 (CH3O), 55.8 (CH3O), 56.4 (CH3O), 86.4 (ArC), 91.2 (ArCH),

93.7 (ArCH), 106.2 (ArC), 110.7 (ArCH), 126.2 (ArCH), 130.27 (ArC), 130.29 (ArCH),

139.0 (ArCH), 140.4 (ArCH), 159.4 (ArC), 162.4 (ArC), 166.1 (ArC), 168.3 (ArC), 192.2

(C=O).

3’-Iodo-5,7,4’-trimethoxyflavone (330)

The title compound was synthesized following the OMe O procedure for flavone 324 using chalcone 329 (400

I mg, 0.06 mmol), DMSO (4 mL) and iodine (16 mg, MeO O

0.06 mmol). The title compound was obtained as an OMe off-white solid (380 mg, 95%). M.p. 206-208 °C, lit.297 206-208 °C; 1H NMR (300 MHz,

CDCl3): 3.92 (s, 3H, CH3O), 3.95 (s, 6H, 2 × CH3 O), 6.37 and 6.58 (2 × d, J = 2.3 Hz,

1H, H6, H8), 6.68 (s, 1H, H3), 6.90 (d, J = 8.7 Hz, 1H, H5’), 7.81 (dd, J = 2.3, 8.7 Hz,

1H, H6’), 8.30 (d, J = 2.3 Hz, 1H, H2’).

1,2-Bis-(4’-methoxyflavon-3’-yl)ethyne (331)

A solution of iodoflavone 324 (225 mg, O MeO 0.6 mmol) in triethylamine (3 mL) and O

DMF (3 mL) was deoxygenated by O heating at 80 °C for 30 min with the OMe O headspace being purged continuously with argon. The mixture was quickly cooled to r.t. and ethynyltrimethylsilane 308 (0.1 mL, 0.7 mmol), PdCl2(PPh3)2 (20 mg, 0.03 mmol) and CuI (7 mg, 0.03 mmol) were added. Heating was continued at 80 °C for 1.5 h. DBU

(0.54 mL, 3.6 mmol) and another equivalent of iodoflavone 324 (225 mg, 0.6 mmol)

238 was added and the heating was continued at 80 °C for another 1.5 h and then at 100

°C for 30 min. The mixture was cooled to r.t., poured into a mixture of hydrochloric acid

(2M, 50 mL) and ethyl acetate (25 mL) and stirred for 10 min. The pale yellow solid was filtered, washed with water (25 mL) and air dried (306 mg, 80%). An analytical sample was prepared by flash chromatography (SiO2, 2% MeOH/dichloromethane). M.p. 262-

-1 -1 -1 -1 264 °C; UV (MeOH): max 218 ( 46330 cm M ), 250 ( 51947 cm M ), 308 ( 74406

-1 -1 - cm M ) nm; IR (KBr): max 1640, 1602, 1499, 1466, 1369, 1279, 1153, 1128, 1022 cm

1 1 ; H NMR (300 MHz, CDCl3): 4.05 (s, 6H, 4’ CH3O, 4’’’ CH3O), 6.84 (s, 2H, H3, H3’’),

7.06 (d, J = 8.6 Hz, 2H, H5’, H5’’’), 7.43 (t, J = 7.9 Hz, 2H, H6, H6’’), 7.92 (d, J = 7.9 Hz,

2H, H8, H8’’), 7.69 (td, J = 1.5, 7.9 Hz, 2H, H7, H7’’), 7.91 (dd, J = 1.9, 8.6 Hz, 2H, H6’,

H6’’’), 8.16 (d, J = 1.9 Hz, 2H, H2’, H2’’’), 8.24 (dd, J = 1.5, 7.9 Hz, 2H, H5, H5’’); 13C

NMR (75.6 MHz, CDCl3): 56.3 (CH3O), 89.6 (-C), 106.4 (ArCH), 111.0 (ArCH), 113.2

(ArC), 118.0 (ArCH), 123.8 (ArC), 124.0 (ArC), 125.2 (ArCH), 125.6 (ArCH), 128.2

(ArCH), 131.6 (ArCH), 133.7 (ArCH), 156.1 (ArC), 162.4 (ArC), 162.6 (ArC), 178.2

+ (C=O); HRMS (ESI) m/z Calcd. for C34H22O6Na (M + Na) 549.1309. Found 549.1304;

Anal. Calcd. for C34H22O6: C, 77.56; H, 4.18. Found: C, 77.45; H, 4.23.

1,2-Bis-(4’,5-dimethoxyflavon-3’-yl)ethyne (332)

The title compound was synthesized OMe O MeO following the procedure for dimer 331 O using iodoflavone 326 (243 mg + 243 O mg), triethylamine (3 mL), DMF (3 mL), OMe O OMe

PdCl2(PPh3)2 (20 mg, 0.03 mmol), CuI (7 mg, 0.03 mmol), ethynyltrimethylsilane 308

(0.1 mL, 0.7 mmol) and DBU (0.54 mL, 3.6 mmol). The title compound 332 was obtained as an off-white solid (314 mg, 90%). An analytical sample was prepared by flash chromatography (SiO2, 2% MeOH/dichloromethane). M.p. 277-279 °C; IR (KBr):

-1 1 max 1637, 1602, 1476, 1439, 1404, 1278, 1264, 1099, 1038 cm ; H NMR (300 MHz,

CDCl3): 4.00 (s, 6H, 2 × CH3O), 4.03 (s, 6H, 2 × CH3O), 6.64 (s, 2H, H3, H3’’), 6.82 239 and 7.15 (2 × d, J = 8.3 Hz, 4H, H6, H6’’, H8, H8’’), 7.03 (d, J = 9.0 Hz, 2H, H5’, H5’’’),

7.57 (t, J = 8.3 Hz, 2H, H7, H7’’), 7.85 (dd, J = 2.3, 9.0 Hz, 2H, H6’, H6’’’), 8.10 (d, J =

13 2.3 Hz, 2H, H2’, H2’’’); C NMR (75.6 MHz, CDCl3): 56.2 (CH3O), 56.4 (CH3O), 89.6

(CC), 106.4 (ArCH), 108.1 (ArCH), 110.1 (ArCH), 110.9 (ArCH), 113.2 (ArC), 114.5

(ArC), 123.8 (ArC), 127.9 (ArCH), 131.4 (ArCH), 133.6 (ArCH), 158.2 (ArC), 159.7

(ArC), 160.2 (ArC), 162.2 (ArC), 178.1 (C=O); HRMS (ESI) m/z Calcd. for C36H26O8Na

+ 1 (M + Na) 609.1520. Found 609.1520; Anal. Calcd. for C36H26O8· /2H2O: C, 72.60; H,

4.53. Found: C, 72.62; H, 4.57.

1,2-Bis-(4’,7-dimethoxy flavon-3’-yl)ethyne (333)

The title compound was O MeO synthesized following the O OMe procedure for dimer 331 MeO O OMe using iodoflavone 328 (243 O mg + 243 mg), triethylamine (3 mL), DMF (3 mL), PdCl2(PPh3)2 (20 mg, 0.03 mmol),

CuI (7 mg, 0.03 mmol), ethynyltrimethylsilane 308 (0.1 ml, 0.7 mmol) and DBU (0.54 mL, 3.6 mmol). The title compound 333 was obtained as a pale yellow solid (314 mg,

90%). An analytical sample was prepared by flash chromatography (SiO2, 2%

MeOH/dichloromethane). M.p. 274-276 °C; IR (KBr): max 1646, 1628, 1603, 1496,

-1 1 1440, 1280, 1164, 1018, 832 cm ; H NMR (300 MHz, CDCl3): 3.94 (s, 6H, 2 ×

CH3O), 4.04 (s, 6H, 2 × CH3O), 6.73 (s, 2H, H3, H3’’), 6.98 (dd, J = 2.3, 9.4 Hz, 2H, H6,

H6’’), 6.99 (d, J = 2.3 Hz, 2H, H8, H8’’), 7.05 (d, J = 9.0 Hz, 2H, H5’, H5’’’), 7.88 (dd, J =

2.3, 9.0 Hz, 1H, H6’, H6’’’), 8.12 (d, J = 2.3 Hz, 2H, H2’, H2’’’), 8.13 (d, J = 9.4 Hz, 2H,

13 H5, H5’’); C NMR (150 MHz, DMSO-d6, 60 °C): 57.0 (CH3O), 57.3 (CH3O), 90.5,

102.0, 106.8, 113.2, 113.4, 115.5, 118.1, 124,6, 127.1, 129.7, 131.7, 158.4, 162.4,

+ 163.3, 164.9, 177.2 (C=O); HRMS (ESI) m/z Calcd. for C36H26O8Na (M + Na)

609.1520. Found 609.1530; Anal. Calcd. for C36H26O8: C, 73.72; H, 4.43. Found: C,

73.74; H 4.52.

240 1,2-Bis-(4’,5,7-trimethoxyflavon-3’-yl)ethyne (334)

The title compound was OMe O MeO synthesized following the O OMe MeO O procedure for dimer 331 OMe O OMe using iodoflavone 330 (260 mg + 260 mg), triethylamine (3 mL), DMF (5 mL), PdCl2(PPh3)2 (20 mg, 0.03 mmol),

CuI (7 mg, 0.03 mmol), ethynyltrimethylsilane 308 (0.1 mL, 0.7 mmol) and DBU (0.54 mL, 3.6 mmol). The title compound 334 was obtained as a pale yellow solid (322 mg,

84%). An analytical sample was prepared by flash chromatography (SiO2, 1.5%

MeOH/dichloromethane). M.p. 308-310 °C; IR (KBr): max 1639, 1605, 1494, 1342,

-1 1 1164, 1120 cm ; H NMR (300 MHz, CDCl3): 3.92 (s, 6H, 2 × CH3O), 3.96 (s, 6H, 2 ×

CH3O), 4.03 (s, 6H, 2 × CH3O), 6.38 (d, J = 2.3 Hz, 2H, H6, H6’’), 6.60 (d, J = 2.3 Hz,

2H, H8, H8’’), 6.64 (s, 2H, H3, H3’’), 7.02 (d, J = 9.0 Hz, 2H, H5’, H5’’’), 7.83 (dd, J =

2.3, 9.0 Hz, 2H, H6’, H6’’’), 8.09 (d, J = 2.3 Hz, 2H, H2’, H2’’’); 13C NMR (Due to very low solubility of compound 334 13C NMR could not be obtained); HRMS (ESI) m/z

+ Calcd. for C38H30O10Na (M + Na) 669.1731. Found 669.1746; Anal. Calcd. for

C38H30O10·H2O: C, 69.61; H, 4.73. Found: C, 69.41; H, 4.73.

1,2-Bis[4-(4,6-dimethoxyindol-3-yl)phenyl]ethyne (335)

The title compound was MeO 5 5'' OMe OMe MeO 6' 5' 5''' 6''' synthesized following the 7 7''

HN NH procedure for dimer 331 using 2 2' 3' 3''' 2''' 2'' bromoindole 110 (300 mg + 300 mg), triethylamine (3 mL), DMF (3 mL), PdCl2(PPh3)2

(35 mg, 0.05 mmol), CuI (15 mg, 0.08 mmol), ethynyltrimethylsilane 308 (0.15 mL, 1.06 mmol) and DBU (0.54 mL, 3.6 mmol). The heating in this case was done for 2 h instead of 1.5 h. The title compound 335 was obtained as a pale yellow solid (267 mg, 56%).

An analytical sample was prepared by flash chromatography (SiO2, 10% hexane/dichloromethane). M.p. 295 °C (from dichloroethane/hexane); IR (KBr): max 241 3394, 2926, 2832, 1625, 1607, 1583, 1551, 1511, 1332, 1215, 1199, 1161, 1146, 1125,

-1 1 1091, 1045, 965, 843 cm ; H NMR (300 MHz, acetone-d6): 3.80 (s, 6H, 2 × CH3O),

3.83 (s, 6H, 2 × CH3O), 6.26 (d, J = 1.9 Hz, 2H, H5, H5’’), 6.61 (d, J = 1.9 Hz, 2H, H7,

H7’’), 7.24 (d, J = 1.5 Hz, 2H, H2, H2’’), 7.49 and 7.65 (2 × d, J = 8.3 Hz, 8H, H2’, H3’,

H5’, H6’, H2’’’, H3’’’, H5’’’, H6’’’), 10.32 (bs, 2H, 2 × NH); 13C NMR (75.6 MHz, acetone- d6): 54.3 (CH3O), 54.7 (CH3O), 87.1 (ArCH), 89.5 (CC), 91.9 (ArCH), 109.9 (ArC),

117.4 (ArC), 119.8 (ArC), 121.5 (ArCH), 129.1 (ArCH), 130.4 (ArCH), 137.0 (ArC),

139.1 (ArC), 154.5 (ArC), 157.6 (ArC); HRMS (ESI) m/z Calcd. for C34H28N2O4Na (M +

+ 1 Na) 551.1941. Found 551.1936; Anal. Calcd. for C34H28N2O4· /2H2O: C, 75.97; H, 5.40;

N, 5.21. Found: C, 76.14; H, 5.42; N, 5.09.

1-(4’,7-Dimethoxyisoflavon-3’-yl)-2-(4’’’,7’’-dimethoxyflavon-3’’’-yl)ethyne (341)

A solution of iodoflavone 328 5' OMe O 6' O (204 mg, 0.5 mmol) in 5 5'' 6 3'' 6'' 2' 2''' triethylamine (2.5 mL) and 2 MeO O O OMe MeO 6''' DMF (5 mL) was deoxygenated 5''' by heating at 80 °C for 30 min with the headspace being purged continuously with argon. The mixture was quickly cooled to r.t. and ethynyltrimethylsilane 308 (84 L, 0.6 mmol), PdCl2(PPh3)2 (25 mg, 0.035 mmol) and CuI (8 mg, 0.04 mmol) were added.

Heating was continued at 80 °C for 1.5 h. DBU (0.54 mL, 3.6 mmol) and isoflavone 311

(204 mg, 0.6 mmol) were added and the heating was continued at 80 °C for another 1.5 h and then at 100 °C for 30 min. The mixture was cooled to r.t. and poured into a mixture of hydrochloric acid (2M, 50 mL) and ethyl acetate (25 mL) and stirred for 10 min. The solid was filtered, washed with water (25 mL) and air dried (270 mg, 82%). An analytical sample was prepared by flash chromatography (SiO2, 2%

MeOH/dichloromethane). M.p. 239-241 °C (from dichloroethane/hexane); IR (KBr): max

2929, 2835, 1626, 1630, 1604, 1502, 1440, 1278, 1201, 1162, 1095, 1021 cm-1; 1H

NMR (300 MHz, CDCl3): 3.91 (s, 3H, CH3O), 3.92 (s, 3H, CH3O), 3.98 (s, 3H, CH3O),

242 3.99 (s, 3H, CH3O), 6.69 (s, 1H, H3’’), 6.85 (d, J = 2.3 Hz, 1H, H8), 6.99 (m, 5H, H5’,

H6, H5’’’, H6’’, H8’’), 7.59 (dd, J = 2.3, 8.7 Hz, 1H, H6’), 7.74 (d, J = 2.3 Hz, 1H, H2’),

7.81 (dd, J = 2.3, 8.8 Hz, 1H, H6’’’), 7.97 (s, 1H, H2), 8.11 (d, J = 8.6 Hz, 1H, H5’’), 8.11

13 (d, J = 2.3 Hz, 1H, H2’’’), 8.21 (d, J = 9.0 Hz, 1H, H5); C NMR (75.6 MHz, CDCl3):

55.7 (CH3O), 55.8 (CH3O), 56.1 (CH3O), 56.2 (CH3O), 88.8 and 90.6 (CC), 100.1

(ArCH), 100.3 (ArCH), 106.3 (ArCH), 110.8 (ArCH), 110.9 (ArCH), 112.4 (ArC), 113.7

(ArC), 114.3 (ArCH), 114.6 (ArCH), 117.7 (ArC), 118.3 (ArC), 124.0 (ArC), 124.1 (ArC),

124.2 (ArC), 126.9 (ArCH), 127.6 (ArCH), 127.7 (ArCH), 130.8 (ArCH), 131.3 (ArCH),

133.8 (ArCH), 152.2 (ArCH), 157.9 (ArC), 159.8 (ArC), 162.1 (ArC), 162.2 (ArC). 164.0

+ (ArC), 175.6 (C=O), 177.7 (C=O); HRMS (ESI) m/z Calcd. for C36H26O8Na (M + Na)

1 609.1520. Found 609.1515; Anal. Calcd. for C36H26O8· /2H2O: C, 72.60; H, 4.53. Found:

C, 72.08; H, 4.50.

1-(4’,7-Dimethoxyisoflavon-3’-yl)-2-(4’’’,5’’-dimethoxyflavon-3’’’-yl)ethyne (344)

A solution of iodoflavone 326 (243 5' OMe O 6' OOMe 5 mg, 0.6 mmol) in triethylamine (3 6 3'' 6'' 2' 2''' 2 7'' mL) and DMF (3 mL) was MeO O O MeO 6''' deoxygenated by heating at 80 °C 5''' for 30 min with the headspace being purged continuously with argon. The mixture was quickly cooled to r.t. and ethynyltrimethylsilane 308 (100 L, 0.7 mmol), PdCl2(PPh3)2

(30 mg, 0.042 mmol) and CuI (10 mg, 0.05 mmol) were added. Heating was continued at 80 °C for 1.5 h. DBU (0.54 mL, 3.6 mmol) and iodoisoflavone 311 (243 mg, 0.6 mmol) were added and the heating was continued at 80 °C for another 1.5 h and then at 100 °C for 30 min. The mixture was cooled to r.t. and poured into a mixture of hydrochloric acid (2M, 50 mL) and ethyl acetate (25 mL) and stirred for 10 min. The solid was filtered, washed with water (25 mL) and air dried (272 mg, 76%). An analytical sample was prepared by flash chromatography (SiO2, 2%

MeOH/dichloromethane). M.p. 168 °C (from dichloroethane/hexane); IR (KBr): max

243 3075, 2832, 1638, 1634, 1603, 1503, 1475, 1439, 1279, 1265, 1106, 1094, 1038, 1020

-1 1 cm ; H NMR (300 MHz, CDCl3): 3.92 (s, 3H, CH3O), 3.99 (3 × s, 9H, 3 × CH3O),

6.67 (s, 1H, H3’’), 6.82 (d, J = 8.3 Hz, 1H, H6’’), 6.86 (d, J = 2.3 Hz, 1H, H8), 6.99 (m,

3H, H6, H5’’’, H5’), 7.16 (d, J = 8.3 Hz, 1H, H8’’), 7.56 (t, J = 8.3 Hz, 1H, H7’’), 7.62 (dd,

J = 2.3, 8.6 Hz, 1H, H6’), 7.72 (d, J = 2.3 Hz, 1H, H2’), 7.81 (dd, J = 2.3, 8.7 Hz, 1H,

H6’’’), 7.97 (s, 1H, H2), 8.09 (d, J = 2.3 Hz, 1H, H2’’’), 8.21 (d, J = 9.0 Hz, 1H, H5); 13C

NMR (75.6 MHz, CDCl3): 55.7 (CH3O), 56.1 (CH3O), 56.2 (CH3O), 56.4 (CH3O), 88.8 and 90.6 (CC), 100.1 (ArCH), 106.3 (ArCH), 108.0 (ArCH), 110.1 (ArCH), 110.7

(ArCH), 110.9 (ArCH), 112.4 (ArC), 113.6 (ArC), 114.6 (ArCH), 118.3 (ArC), 123.6

(ArC), 124.1 (ArC), 124.2 (ArC), 127.5 (ArCH), 127.7 (ArCH), 130.8 (ArCH), 131.3

(ArCH), 133.5 (ArCH), 133.6 (ArCH), 152.2 (ArCH), 157.9 (ArC), 158.2 (ArC), 159.7

(ArC), 159.9 (ArC), 160.3 (ArC), 162.1 (ArC), 164.0 (ArC), 171.3 (ArC), 175.6 (C=O),

+ 178.2 (C=O); HRMS (ESI) m/z Calcd. for C36H26O8Na (M + Na) 609.1520. Found

1 609.1527; Anal. Calcd. for C36H26O8· /2H2O: C, 72.60; H, 4.53. Found: C, 71.97; H,

4.47.

2,2’-Dimethoxydiphenyl-5,5’-dicarbaldehyde (351)

A mixture of iodobenzaldehyde 319 (2.0 g, 7.6 mmol), copper powder OMe OMe

(4.0 g, 62.9 mmol) and DMF (10 mL) was heated under an argon atmosphere at 150 °C for 24 h. The mixture was cooled to r.t. filtered CHO CHO through a Celite® bed which was then washed with acetone. The combined filtrate was concentrated under vacuum, diluted with water (50 mL) and the product extracted with ethyl acetate (25 mL × 4). The combined organic extracts were dried over sodium sulfate and concentrated. Chromatography (SiO2, 30% ethyl acetate/hexane) gave dicarbaldehyde 351 as off-white crystals (0.68 g, 66%). M.p. 131-133 °C, lit.293 134 °C;

1 H NMR (300 MHz, CDCl3): 3.86 (s, 6H, 2 × CH3O), 7.09 (d, J = 8.3 Hz, 2H, H3, H3’),

7.77 (d, J = 2.3 Hz, 2H, H6, H6’), 7.91 (dd, J = 2.3, 8.3 Hz, 2H, H4, H4’), 9.92 (s, 2H, 2

244 13 × CHO); C NMR (75.6 MHz, CDCl3): 55.9 (CH3O), 110.8 (ArCH), 127.1 (ArC), 129.5

(ArC), 131.8 (ArCH), 133.0 (ArCH), 161.9 (ArC), 190.7 (CHO).

Attempted dimerization of iodoisoflavone 311

A mixture of iodoisoflavone 311 (100 mg, 0.25 mmol), OMe O copper powder (100 mg, 1.5 mmol) and dry DMF (1 mL) was heated at 155 °C for 14 h under an argon MeO O atmosphere. TLC analysis showed formation of a product at the same Rf as the starting material (having stronger iodine absorption). The mixture was cooled to r.t. poured into water (10 mL) and extracted with DCM (10 mL × 2). The combined extract was filtered through Celite® and concentrated under vacuum. Purification by preparative chromatography (SiO2, 30% ethyl acetate/hexane) gave a white solid which was characterized as dimethoxyisoflavone 262. M.p. 163-165 °C (from acetone), lit.284 162-

1 163 °C; H NMR (300 MHz, DMSO-d6): 3.79 (s, 3H, CH3O), 3.90 (s, 3H, CH3O), 6.99

(d, J = 8.4 Hz, 2H, H3’, H5’), 7.07 (dd, J = 2.5, 8.8 Hz, 1H, H6), 7.14 (d, J = 2.5 Hz, 1H,

H8), 7.52 (d, J = 8.4 Hz, 2H, H2’, H6’), 8.02 (d, J = 8.8 Hz, 1H, H5), 8.40 (s, 1H, H2).

Copper(I) thiophenecarboxylate (CuTC) (355)298

A 100 mL round bottomed flask was charged with thiophene-2- S COOCu carboxylic acid 354 (10.0 g, 78 mmol), Cu2O (2.8 g, 19.6 mmol) and toluene (80 mL). The flask was then fitted with a Dean-Stark trap and condenser and the mixture refluxed overnight with azeotropic removal of water. The mixture was cooled to 60 °C and the product was filtered under a nitrogen atmosphere. The solid was washed under a nitrogen atmosphere successively with methanol (50 mL), dry ether (30 mL) and hexane (20 mL). The solid was transferred to a round bottomed flask and dried under high vacuum. The title compound was obtained as a light green powder and was used further without purification (5.5 g, 73 %).

245 Attemped dimerization of (330)

A mixture of iodoflavone 330 (200 mg, 0.45 mmol) and OMe O copper powder (200 mg, 3.1 mmol) was heated under argon at 230 °C for 3 h. The mixture was cooled to r.t. MeO O and extracted with chloroform. The combined OH chloroform extract was filtered through a Celite® bed, concentrated under vacuum and chromatographed (SiO2, 30% ethyl acetate/hexane). The isolated compound was identified as 4’-hydroxy-5,7-dimethoxyflavone 356 (80 mg, 60%). M.p. 298-301 °C,

299 1 lit. 301-303 °C; H NMR (300 MHz, CDCl3): 3.88 and 3.89 (2 × s, 6H, 2 × CH3O),

6.36 and 6.48 (2 × d, J = 2.3 Hz, 2H, H6, H8), 6.57 (s, 1H, H3), 7.01 (d, J = 9.0 Hz, 2H,

H2’, H6’), 7.84 (d, J = 9.0 Hz, 2H, H3’, H5’).

2,2’-Dimethoxydiphenyl-5,5’-dicarbaldehyde (351) (Suzuki-Miyaura coupling)

A mixture of 3-iodo-4-methoxybenzaldehyde 319 (131 mg, 0.5 OMe OMe mmol), PdCl2(dppf) (20 mg, 0.025 mmol), bis(pinacolato)diboron

357 (127 mg, 0.5 mmol) and potassium acetate (180 mg, 1.8 mmol) CHO CHO in dry DMF (2 mL) was heated under argon at 100 °C for 2 h. Another equivalent of aldehyde 319 (131 mg, 0.5 mmol) was added followed by addition of Pd(PPh3)4 (25 mg,

0.04 mmol), and solution of NaOH (40 mg, 1 mmol) in water (0.4 mL). The reaction was continued further for 4 h, cooled to r.t., diluted with water (50 mL) and stirred for 10 min.

The product was filtered, washed with water (25 mL) and air dried. Column chromatography initially using 100% dichloromethane and then with dichloromethane/ethyl acetate (90:10) gave pure dicarbaldehyde 351 as an off-white

293 1 solid (105 mg, 77%). M.p. 131-133 °C, lit. 134 °C; H NMR (300 MHz, CDCl3): 3.86

(s, 6H, 2 × CH3O), 7.09 (d, J = 8.3 Hz, 2H, H3, H3’), 7.77 (d, J = 2.3 Hz, 2H, H6, H6’),

7.91 (dd, J = 2.3, 8.3 Hz, 2H, H4, H4’), 9.92 (s, 2H, 2 × CHO).

246 4’,4’’’-Dimethoxy-3’,3’’’-biflavone (361)

A mixture of 3’-iodo-4’-methoxyflavone 324 O 5 5''' 3 MeO 6''' (dppf) (20 mg, (190 mg, 0.5 mmol), PdCl2 2' 8'' O 7 O 0.025 mmol, 5 mol %), bis(pinacolato) 8 2''' 6' 3'' 5' OMe 5'' diboron 357 (127 mg, 0.5 mmol) and O potassium acetate (180 mg, 1.8 mmol) in dry DMF (2 mL) was heated under argon at

100 °C for 2 h. Another equivalent of iodoflavone 324 (190 mg, 0.5 mmol) was added followed by addition of Pd(PPh3)4 (25 mg, 0.04 mmol) and a solution of NaOH (40 mg, 1 mmol) in water (0.4 mL). The reaction was continued further for 3.5 h, cooled to r.t., diluted with water (50 mL) and stirred for 10 min. The product was filtered, washed with water (25 mL) and air dried. Chromatography (SiO2, 70% dichloromethane/ethyl acetate) gave pure biflavone 361 as a pale yellow solid (160 mg, 63%). M.p. 322 °C,

294 -1 1 lit. 327 °C; IR (KBr): max 1653, 1605, 1465, 1493, 1269, 1248 cm ; H NMR (300

MHz, CDCl3 + CD3OD): 3.81 (s, 6H, 4’ CH3O, 4’’’ CH3O), 6.74 (s, 2H, H3, H3’’), 7.08

(d, J = 9.0 Hz, 2H, H5’, H5’’’), 7.35 (td, J = 1.4, 7.9 Hz, 2H, H6, H6’’), 7.51 (dd, J = 1.1,

7.9 Hz, 2H, H8, H8’’), 7.63 (ddd, J = 1.5, 7.9, 8.3 Hz, 2H, H7, H7’’), 7.81 (d, J = 2.6 Hz,

2H, H2’, H2’’’), 7.94 (dd, J = 2.6, 9.0 Hz, 2H, H6’, H6’’’), 8.12 (dd, J = 1.5, 7.9 Hz, 2H,

13 H5, H5’’); C NMR (75.6 MHz, CDCl3 + CD3OD): 55.8 (CH3O), 105.8 (ArCH), 111.3

(ArCH), 117.9 (ArCH), 123.5 (ArC), 125.2 (ArCH), 125.2 (ArCH), 127.4 (ArC), 127.9

(ArCH), 129.4 (ArCH), 133.8 (ArCH), 156.1 (ArC), 160.0 (ArC), 163.9 (ArC), 179.0

+ (ArC); MS (ESI) m/z for C32H22O6Na (M + Na) 525.11.

4’,4’’’,5,5’’-Tetramethoxy-3’,3’’’-biflavone (362)

The title compound was synthesized OMe O MeO following the procedure for biflavone 361 O using 3’-iodo-4’,5-dimethoxyflavone 326 O OMe (204 mg (0.5 mmol) + 204 mg (0.5 mmol)), O OMe bis(pinacolato)diboron 357 (150 mg, 0.6 mmol), PdCl2(dppf) (20 mg, 0.025 mmol),

247 potassium acetate (180 mg, 1.8 mmol), NaOH (40 mg, 1 mmol) and Pd(PPh3)4 (25 mg,

0.04 mmol). Biflavone 362 was obtained as a pale yellow solid (165 mg, 59%). M.p.

-1 -1 -1 -1 321-323 °C; UV (MeOH): max 209 ( 29995 cm M ), 264 ( 23149 cm M ), 328 (

-1 -1 -1 1 28283 cm M ) nm; IR (KBr): max 1633, 1601, 1475, 1262, 1102, 1023, 803 cm ; H

NMR (300 MHz, CDCl3 + CD3OD): 3.84 (s, 6H, 4’ CH3O, 4’’’ CH3O), 3.96 (s, 6H, 5

CH3O, 5’’ CH3O), 6.72 (s, 2H, H3, H3’’), 6.80 (d, J = 8.3 Hz, 2H, H6, H6’’), 7.09 (d, J =

8.3 Hz, 2H, H5’, H5’’’), 7.11 (d, J = 8.3 Hz, 2H, H8, H8’’), 7.52 (t, J = 8.3 Hz, 2H, H7,

H7’’), 7.80 (d, J = 1.9 Hz, 2H, H2’, H2’’’), 7.92 (dd, J = 1.9, 8.3 Hz, 2H, H6’, H6’’’); 13C

NMR (75.6 MHz, CDCl3 + CD3OD): 55.8 (CH3O), 56.1 (CH3O), 106.4 (ArCH), 107.4

(ArCH), 110.0 (ArCH), 111.2 (ArCH), 114.1 (ArC), 123.2 (ArC), 127.4 (ArC), 127.6

(ArCH), 129.2 (ArCH), 133.8 (ArCH), 158.1 (ArC), 159.6 (ArC), 159.8 (ArC), 161.6

+ (ArC), 178.9 (C=O); MS (ESI) m/z for C34H26O8Na (M + Na) 585.12; Anal. Calcd. for

C34H26O8·2H2O: C, 68.22; H, 5.05. Found: C, 68.19; H, 4.85.

4,4’-Biindole (364)

A mixture of 4-bromoindole 363 (196 mg, 1.0 mmol), PdCl2(dppf) HN NH

(40 mg, 0.05 mmol), bis(pinacolato)diboron 357 (254 mg, 1.0 mmol) and potassium acetate (180 mg, 1.8 mmol) in dry DMF (3 mL) was heated under argon at 100 °C for 3 h. Another equivalent of 4-bromoindole

363 (196 mg, 1.0 mmol) was added followed by addition of Pd(PPh3)4 (56 mg, 0.08 mmol), and a solution of NaOH (80 mg, 2 mmol) in water (0.8 mL). The reaction was continued further for 12 h, cooled to r.t. and diluted with water (25 mL). The product was extracted with dichloromethane (25 mL × 3). The combined organic extract was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography

(SiO2, 20% ethyl acetate/hexane) gave biindole 364 as grey crystals (96 mg, 41%).

-1 -1 M.p. 258-260 °C (from MeOH); UV (MeOH): max 219 ( 31918 cm M ), 300 ( 13800

-1 -1 -1 1 cm M ); IR (KBr): max 3395, 1426, 1403, 1333, 758 cm ; H NMR (300 MHz, CDCl3):

6.60 (dd, J = 0.8, 1.9 Hz, 2H, H3, H3’), 7.17-7.56 (m, 8H, H2, H2’, H5, H5’, H6, H6’, 248 13 H7, H7’), 8.23 (br, 2H, 2 × NH); C NMR (75.6 MHz, CDCl3): 103.1 (ArCH), 109.8

(ArCH), 120.6 (ArCH), 122.0 (ArCH), 123.7 (ArCH), 126.8 (ArC), 133.8 (ArC), 136.2

+ (ArC); HRMS (TOF-ESI) m/z Calcd. for C16H12N2Na (M + Na) 255.0893. Found

255.1544; Anal. Calcd. for C16H12N2: C, 82.73; H, 5.21; N, 12.06. Found: C, 82.31; H,

5.40, N, 11.84.

5,5’-Biindole (365)

The title compound was synthesized following the HN NH procedure for biindole 364 using 5-bromoindole 337 (196 mg + 196 mg), PdCl2(dppf) (40 mg, 0.05 mmol), bis(pinacolato)diboron 357 (254 mg,

1.0 mmol), potassium acetate (180 mg, 1.8 mmol), dry DMF (3 mL), Pd(PPh3)4 (56 mg,

0.08 mmol), and a solution of NaOH (80 mg, 2 mmol) in water (0.8 mL).

Chromatography (SiO2, 30% ethyl acetate/hexane) gave the title compound as grey

300 crystals (85 mg, 37%). M.p. 214 °C, lit. 212-215 °C; IR (KBr): max 3396, 1465, 1454,

-1 1 1416, 1027, 875, 804, 730 cm ; H NMR (300 MHz, acetone-d6): 6.50 (m, 2H, H3,

H3’), 7.30-7.50 (m, 6H, H2, H2’, H6, H6’, H7, H7’), 7.80 (s, 2H, H4, H4’), 10.18 (bs, 2H,

13 2 × NH); C NMR (75.6 MHz, acetone-d6): 101.7 (ArC), 111.2 (ArCH), 118.4 (ArCH),

121.3 (ArCH), 124.9 (ArCH), 125.0 (ArCH), 128.7 (ArC), 134.1 (ArC).

6,6’-Biindole (367)

The title compound was synthesized following the procedure for biindole 364 using 6-bromoindole 366 (196 mg + 196 mg), N N PdCl2(dppf) (40 mg, 0.05 mmol), bis(pinacolato)diboron 357 H H

(254 mg, 1.0 mmol), potassium acetate (180 mg, 1.8 mmol), dry DMF (3 mL),

Pd(PPh3)4 (56 mg, 0.08 mmol), and a solution of NaOH (80 mg, 2 mmol) in water (0.8 mL). Chromatography (SiO2, 30% ethyl acetate/hexane) gave the title compound as

-1 -1 grey needles (102 mg, 44%). M.p. 285 (dec); UV (MeOH): max 211 ( 33037 cm M ),

-1 -1 -1 -1 243 ( 47980 cm M ), 304 ( 27387 cm M ) nm; IR (KBr): max 3385, 1453, 1096, 249 -1 1 1061, 807, 722, 528 cm ; H NMR (300 MHz, acetone-d6): 6.46 (m, 2H, H3, H3’),

7.32 (m, 2H, H2, H2’), 7.36 (dd, J = 1.9, 8.3 Hz, 2H, H5, H5’), 7.61 (d, J = 8.3 Hz, 2H,

13 H4, H4’), 7.69 (m, 2H, H7, H7’); C NMR (75.6 MHz, acetone-d6): 101.2 (ArCH),

109.4 (ArCH), 119.1 (ArCH), 120.2 (ArCH), 124.8 (ArCH), 127.0 (ArC), 136.1 (ArC),

+ 137.0 (ArC); HRMS (TOF-ESI) m/z Calcd. for C16H12N2Na (M + Na) 255.0893. Found

255.1547; Anal. Calcd. for C16H12N2: C, 82.73; H, 5.21; N, 12.06. Found: C, 82.30; H,

5.35; N, 11.72.

7,7’-Biindole (369)

The title compound was synthesized following the procedure for NH HN biindole 364 using 7-bromoindole 368 (196 mg + 196 mg),

PdCl2(dppf) (40 mg, 0.05 mmol), bis(pinacolato)diboron 357 (254 mg, 1.0 mmol), potassium acetate (180 mg, 1.8 m mol), dry DMF (3 mL), Pd(PPh3)4 (56 mg, 0.08 mmol), and a solution of NaOH (80 mg, 2 mmol) in water (0.8 mL).

Chromatography (SiO2, 30% ethyl acetate/hexane) gave the title compound as grey

48 crystals (114 mg, 50%). M.p. 252 °C, lit. 244-245 °C; UV (MeOH): max 217 ( 28529

-1 -1 -1 -1 cm M ), 293 ( 13086 cm M ) nm; IR (KBr): max 3389, 1423, 1410, 1337, 804, 779,

-1 1 728 cm ; H NMR (300 MHz, acetone-d6): 6.54 (m, 2H, H3, H3’), 7.13 (dd, J = 7.1,

7.5 Hz, 2H, H5, H5’), 7.25 (dd, J = 1.1, 7.1 Hz, 2H, H6, H6’), 7.29 (m, 2H, H2, H2’),

7.61 (dd, J = 1.1, 7.5 Hz, 2H, H4, H4’), 9.91 (br, 2H, 2 × NH); 13C NMR (75.6 MHz, acetone-d6): 101.8 (ArCH), 119.4 (ArCH), 119.6 (ArCH), 121.6 (ArCH), 122.7 (ArC),

125.1 (ArCH), 128.8 (ArC), 134.1 (ArC).

4,4’-Bis(4,6-dimethoxyindol-3-yl)biphenyl (370)

A mixture of 3-(4-bromophenyl)-4,6-dimethoxyindole 110 MeO OMe

(166 mg, 0.5 mmol), PdCl2(dppf) (20 mg, 0.025 mmol),

HN bis(pinacolato)diboron 357 (127 mg, 0.5 mmol) and 2 potassium acetate (180 mg, 1.8 mmol) in dry DMF (2 mL) was heated under argon at

250 100 °C for 3 h. Another equivalent of indole 110 (166 mg, 0.5 mmol) was added followed by addition of Pd(PPh3)4 (28 mg, 0.04 mmol) and a solution of NaOH (40 mg,

1 mmol) in water (0.4 mL). The reaction was continued further for 12 h, cooled to r.t. and diluted with water (25 mL). The product was extracted with dichloromethane (25 mL × 3). The combined organic extract was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 50% ethyl acetate/hexane) gave

-1 - pure dimer 370 (92 mg, 37%). M.p. 291-294 °C; UV (MeOH): max 206 ( 41775 cm M

1 -1 -1 -1 -1 ), 224 ( 41595 cm M ), 324 ( 19084 cm M ) nm; IR (KBr): max 3413, 3348, 1624,

-1 1 1545, 1334, 1214, 1162, 1143 cm ; H NMR (300 MHz, acetone-d6): 3.80 (s, 6H, 2 ×

CH3O), 3.83 (s, 6H, 2 × CH3O), 6.25 (d, J = 1.9 Hz, 2H, H5, H5’’), 6.61 (d, J = 1.9 Hz,

2H, H7, H7’’), 7.22 (m, 2H, H2, H2’’), 7.67 and 7.69 (2 × d, J = 8.7 Hz, 8H, H2’, H2’’’,

H3’, H3’’’, H5’, H5’’’, H6, H6’’’), 10.23 (brs, 2H, 2 × NH); 13C NMR (75.6 MHz, acetone- d6): 54.3 (CH3O), 54.7 (CH3O), 87.1 (ArCH), 91.8 (ArCH), 117.6 (ArC), 117.7 (ArC),

120.9 (ArC), 121.0 (ArC), 125.4 (ArCH), 129.6 (ArCH), 135.6 (ArC), 137.6 (ArC), 154.7

+ (ArC), 157.5 (ArC); MS (ESI) m/z for C32H28N2O4 (M ) 504.17; Anal. Calcd. for

C32H28N2O4: C, 76.17; H, 5.59; N, 5.55. Found: C, 76.51; H, 5.72; N, 5.32.

4,4’-Bis-(4,6-dimethoxybenzofuran-3-yl)biphenyl (371)

The title compound was synthesized following the MeO OMe procedure for dimer 370 using 3-(4-bromophenyl)-4,6- dimethoxybenzofuran 103 (166 mg + 166 mg), PdCl 2 O

(dppf) (20 mg, 0.025 mmol), bis(pinacolato)diboron 357 2

(127 mg, 0.5 mmol) and potassium acetate (90 mg, 0.9 mmol), dry DMF (2 mL),

Pd(PPh3)4 (28 mg, 0.04 mmol) and a solution of NaOH (40 mg, 1 mmol) in water (0.4 mL). Chromatography (SiO2, 20% ethyl acetate/hexane) gave pure dimer 371 as a

-1 -1 white solid (105 mg, 42%). M.p. 232-235 °C; UV (MeOH): max 212 ( 93646 cm M ),

-1 -1 -1 -1 260 ( 54888 cm M ), 298 ( 40444 cm M ) nm; IR (KBr): max 1623, 1592, 1500,

251 -1 1 1333, 1165, 1147, 1093, 1084 cm ; H NMR (300 MHz, acetone-d6): 3.87 (s, 12H, 2

× CH3O), 6.46 (d, J = 1.9 Hz, 2H, H7, H7’’), 6.77 (d, J = 1.9 Hz, 2H, H5, H5’’), 7.76 (s,

8H, H2’, H2’’’, H3’, H3’’’, H5’, H5’’’, H6’, H6’’’), 7.80 (s, 2H, H2, H2’’); 13C NMR (75.6

MHz, acetone-d6): 54.8 (CH3O), 55.0 (CH3O), 88.2 (ArCH), 94.5 (ArCH), 118.3

(ArCH), 122.3 (ArC), 126.0 (ArCH), 129.5 (ArCH), 131.4 (ArC), 139.1 (ArC), 140.2

(ArC), 145.2 (ArC), 154.6 (ArC), 158.0 (ArC), 159.6 (ArC); MS (ESI) m/z for C32H26O6

+ (M+1) 507.16; Anal. Calcd. for C32H26O6: C, 75.88; H, 5.17. Found: C, 75.88; H, 5.17.

2-(4-Bromophenyl)-4,6-dimethoxyindole (372)

A mixture of bromophenylketone 107 (2.0 g, 5.7 OMe mmol), 3,5-dimethoxyaniline 104 (1.5 g, 1 mmol), 3,5- Br MeO N dimethoxyaniline hydrochloride (80 mg, 0.42 mmol) H and silicone oil (10 mL) was heated at 130 °C under an argon atmosphere for 1 h. The mixture was cooled to r.t., diluted with hexane (40 mL), stirred for 10 min and the hexane layer was decanted. The residue was triturated with hexane (25 mL) and decanted. This was repeated twice to completely remove silicone oil. The residue was dissolved in a mixture of dilute hydrochloric acid (2M, 50 mL) and ether (50 mL). The organic layer was separated. The aqueous layer was extracted with ether (25 mL). The combined organic layer was dried over anhydrous sodium sulfate and concentrated under vacuum. Chromatography (SiO2, 10% ethyl acetate/hexane) gave indole 372 (1.0 g, 53%). M.p. 135-137 °C (from chloroform/hexane), lit.268 135-137 °C; 1H NMR (300

MHz, CDCl3): 3.84 (s, 3H, CH3O), 3.93 (s, 3H, CH3O), 6.23 (d, J = 1.9 Hz, 1H, H5),

6.49 (d, J = 1.9 Hz, 1H, H7), 6.83 (m, 1H, H3), 7.43 and 7.52 (2 × d, J = 8.3 Hz, 4H,

13 H2’, H3’, H5’, H6’), 8.16 (br, 1H, NH); C NMR (75.6 MHz, acetone-d6): 54.5 (CH3O),

54.7 (CH3O), 86.7 (ArCH), 91.5 (ArCH), 97.1 (ArCH), 114.4 (ArC), 119.4 (ArC), 126.0

(ArCH), 131.7 (ArCH), 132.1 (ArC), 133.6 (ArC), 138.9 (ArC), 153.7 (ArC), 158.1 (ArC).

252 4,4’-Bis(4,6-dimethoxyindol-2-yl)biphenyl (373)

The title compound was synthesized following the OMe procedure for dimer 370 using 2-(4-bromophenyl)-4,6-

MeO N dimethoxyindole 372 (168 mg + 168 mg), PdCl2(dppf) (20 H 2 mg, 0.025 mmol), bis(pinacolato)diboron 357 (127 mg, 0.5 mmol), potassium acetate (180 mg, 1.8 mmol), dry DMF (2 mL), Pd(PPh3)4 (28 mg,

0.04 mmol), and a solution of NaOH (40 mg, 1 mmol) in water (0.4 mL).

Chromatography (SiO2, 50% ethyl acetate/hexane) gave pure dimer 373 as an off-white

-1 -1 solid (90 mg, 36%). M.p. 220 °C; UV (MeOH): max 215 ( 52808 cm M ), 258 ( 23419

-1 -1 -1 -1 cm M ), 366 ( 44757 cm M ) nm; IR (KBr): max 2933, 2836, 1623, 1602, 1275, 1217,

-1 1 1149, 1127, 797 cm ; H NMR (300 MHz, acetone-d6): 3.79 (s, 6H, 2 × CH3O), 3.91

(s, 6H, 2 × CH3O), 6.20 (d, J = 1.9 Hz, 2H, H5, H5’’), 6.56 (d, J = 1.1 Hz, 2H, H3, H3’’),

6.89 (d, J = 1.9 Hz, 2H, H7, H7’’), 7.76 and 7.87 (2 × d, J = 8.3 Hz, 8H, H2’, H2’’’, H3’,

13 H3’’’, H5’, H5’’’, H6’, H6’’’), 10.52 (br, 2H, 2 × NH); C NMR (75.6 MHz, acetone-d6):

54.5 (CH3O), 54.7 (CH3O), 86.8 (ArCH), 91.4 (ArCH), 96.6 (ArCH), 114.5 (ArC), 124.7

(ArCH), 126.8 (ArCH), 131.9 (ArC), 134.6 (ArC), 138.3 (ArC), 138.9 (ArC), 153.6 (ArC),

+ 157.9 (ArC); MS (MALDI-ESI) m/z Calcd. for C32H28N2O4 (M) 504.57. Found 504.12;

Anal. Calcd. for C32H28N2O4: C, 76.17; H, 5.59; N, 5.55. Found: C, 74.35; H, 5.82, N,

5.50.

1-(4-Bromophenyl)-2-(3,4,5-trimethoxyphenyl)ethanone (376)

A mixture of 4-bromophenacylbromide 101 (1.5 g, 5.4 Br OMe mmol), 3,4,5-trimethoxyphenol 88 (1.0 g, 5.4 mmol), MeO O potassium bicarbonate (1.0 g, 10 mmol) and dioxane MeO O (20 mL) was refluxed for 20 h. The solvent was removed under vacuum and the residue was dissolved in dichloromethane (30 mL). The dichloromethane layer was washed with water, dried over anhydrous sodium sulfate and concentrated under vacuum. The title compound was obtained as a brown solid and was used in the next step without

253 further purification (1.8 g, 58%). M.p. 130-132 °C, lit.269 137-139 °C; 1H NMR (300 MHz,

CDCl3): 3.77 (s, 3H, CH3O), 3.81 (s, 6H, 2 × CH3O), 5.13 (s, 2H, OCH2), 6.18 (s, 2H,

H2’’, H6’’), 7.64 (d, J = 8.2 Hz, 2H, H2’, H6’), 7.87 (d, J = 8.2 Hz, 2H, H3’, H5’).

3-(4-Bromophenyl)-4,5,6-trimethoxybenzofuran (374) Br A mixture of crude ketone 376 (1.8 g, 4.7 mmol) and TFA (3.6 mL, 48.3 mmol) was stirred for 18 h at r.t. The mixture was OMe MeO poured on crushed ice (50.0 g) and stirred for 15 min. The precipitated solid was filtered, washed with water (50 mL) and MeO O air dried. Chromatography (SiO2, 30% dichloromethane/hexane) gave trimethoxybenzofuran 374 (0.6 g, 35%). M.p 95-97 °C, lit.269 95-97 °C; 1H NMR (300

MHz, CDCl3): 3.64 (s, 3H, CH3O), 3.88 (s, 3H, CH3O), 3.92 (s, 3H, CH3O), 6.87 (s,

1H, H7), 7.52 (m, 5H, H2, H2’, H3’, H5’, H6’).

4,4’-Bis-(4,5,6-trimethoxybenzofuran-3-yl)-biphenyl (375)

The title compound was synthesized following the OMe MeO procedure for dimer 370 using 3-(4-bromophenyl)-4,5,6- OMe trimethoxybenzofuran 374 (181 mg + 181 mg), PdCl2 O 2 (dppf) (20 mg, 0.025 mmol), bis(pinacolato)diboron 357

(127 mg, 0.5 mmol), potassium acetate (180 mg, 1.8 mmol), dry DMF (2 mL),

Pd(PPh3)4 (28 mg, 0.04 mmol) and solution of NaOH (40 mg, 1 mmol) in water (0.4 mL). Chromatography (SiO2, 35% ethyl acetate/hexane) gave dimer 375 as a white

-1 -1 solid (117 mg, 39%). M.p. 206-208 °C; UV (MeOH): max 209 ( 82879 cm M ), 257 (

-1 -1 -1 -1 39939 cm M ), 293 ( 47836 cm M ) nm; IR (KBr): max 2962, 2937, 1614, 1569,

-1 1 1469, 1195, 1121 cm ; H NMR (300 MHz, CDCl3): 3.70 (s, 6H, 2 × CH3O), 3.91 (s,

6H, 2 × CH3O), 3.93 (s, 6H, 2 × CH3O), 6.90 (s, 2H, H7, H7’’), 7.59 (s, 2H, H2, H2’’),

13 7.74 (m, 8H, H2’, H2’’’, H3’, H3’’’, H5’, H5’’’, H6’, H6’’’); C NMR (75.6 MHz, CDCl3):

56.2 (CH3O), 61.4 (CH3O), 61.6 (CH3O), 91.5 (ArCH), 112.9 (ArC), 122.3 (ArC), 126.6

254 (ArCH), 129.3 (ArCH), 131.0 (ArC), 138.9 (ArC), 139.5 (ArC), 140.6 (ArCH), 147.1

+ (ArC), 152.4 (ArC), 152.7 (ArC); MS (MALDI-ESI) m/z Calcd. for C34H30O8 (M) 566.59.

Found 566.19; Anal. Calcd. for C34H30O8: C, 72.07; H, 5.34. Found: C, 72.37; H, 5.50.

3-Bromoindole (377)

To a stirred solution of indole 121 (1.17 g, 10 mmol) in DMF (50 mL) was Br added a solution of bromine (1.76 g, 11 mmol) in DMF (50 mL) over 10 N H min. After addition the reaction mixture was poured into an ice-cold solution of potassium metabisulfite (0.50 g, 2.2 mmol) and ammonium hydroxide (2.5 mL, 33% w/v) in water (500 mL). The mixture was stirred for 15 min. and the solid was filtered, washed with water and dried. 3-Bromoindole 377 was obtained as off-white crystals (1.15 g, 65%). M.p. 67-68 °C (from ethyl acetate/hexane), lit.270 65 °C; 1H NMR

(300 MHz, DMSO-d6): 6.80-7.70 (m, 5H, H2, H4, H5, H6, H7), 11.5 (brs, 1H, NH).

3-Bromo-2-phenylindole (380)

To a stirred solution of 2-phenylindole 379 (1.54 g, 8 mmol) in DMF Br

(40 mL) was added a solution of bromine (0.41 mL, 8.1 mmol) in DMF Ph N (40 mL) in 10 min at r.t. The mixture was stirred further for 5 min and H then poured into ice-cold solution (400 mL) of potassium metabisulfite (400 mg, 1.8 mmol) and ammonia (4 mL, 33% w/v). The mixture was stirred for 10 min and filtered.

The solid was washed with water (25 mL × 2) and air dried (1.86 g, 85%). M.p. 76-78

270 1 °C (from hexane/ethyl acetate), lit. 78-79 °C; H NMR (300 MHz, CDCl3): 7.20 (m,

9H, H4, H5, H6, H7, H2’, H3’, H4’, H5’, H6’), 8.29 (brs, 1H, NH).

1-Methylindole (382)271

Indole 121 (2.34 g, 20 mmol) was added to a suspension of crushed KOH

(4.48 g, 80 mmol) in DMSO (40 mL). The dark mixture was stirred at r.t. N Me for 45 min and then cooled to 15 °C. Methyl iodide (5 mL, 85.3 mmol) was added in

255 about 5 min, and then cooling bath was removed. The mixture was stirred for 45 min and poured in water (250 mL). The product was extracted with ether (25 mL × 3) and the combined organic extract was washed with water (25 mL × 3), dried over anhydrous sodium sulfate and concentrated under vacuum. 1-Methylindole 382 was obtained as a brown oil and was used in the next step without further purification (2.60

1 g, 99%). H NMR (300 MHz, CDCl3): 3.80 (s, 3H, NCH3), 6.50 (d, J = 3.0 Hz, 1H, H3),

7.05 (d, J = 3.0 Hz, 1H, H2), 7.11-7.66 (m, 4H, H4, H5, H6, H7).

3-Bromo-1-methylindole (383) Br To a stirred solution of 1-methylindole 382 (1.31 g, 10 mmol) in DMF (5 mL) was added a solution of bromine (0.52 mL, 10.1 mmol) in DMF (5 mL) N in 5 min. The mixture was stirred for further 2 min and then poured into Me ice-cold solution (75 mL) of potassium metabisulfite (100 mg, 0.45 mmol) and ammonium hydroxide (2 mL, 33% w/v). The mixture was stirred for 2 min and extracted with ether (20 mL × 2). The combined organic extract was washed with water (20 mL ×

2), dried over anhydrous sodium sulfate and concentrated under vacuum. Bromoindole

383 was obtained as a brown oil (1.84 g, 87%). The product decomposed completely in

1 30 min resulting in a fuming brown solid. H NMR (300 MHz, CDCl3): 3.77 (s, 3H, N-

CH3), 7.07 (s, 1H, H2), 7.16-7.58 (m. 4H, H4, H5, H6, H7).

256

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275 APPENDIX

CRYSTAL STRUCTURE

DATA

276 Introduction

The X-ray crystallography data shown in the appendix were obtained by Don Craig at the University of New South Wales, Sydney.

Structure determination:

Reflection data were measured with an Enraf-Nonius CAD-4 diffractometer in 2/ scan mode using nickel filtered copper radiation ( 1.5418 Å). Reflections with I>3(I) were considered observed. The structures were determined by direct phasing and Fourier methods. Hydrogen atoms were included in calculated positions and were assigned thermal parameters equal to those of the atom to which they were bonded. Positional and anisotropic thermal parameters for the non-hydrogen atoms were refined using full

2 matrix least squares. Reflection weights used were 1/ (Fo), with (Fo) being derived

2 2 1/2 2 from (Io) = [ (Io) +(0.04Io) ] . The weighted residual is defined as Rw = (w /

2 1/2 wFo ) . Atomic scattering factors and anomalous dispersion parameters were from

International Tables for X-ray crystallography.1 Structure solutions were performed by

SIR9223 and refinements used RAELS. ORTEP II4 running on Macintosh was used for the structural diagrams.

1) Ibres, J. A. and Hamilton, W. C. (Eds). Internatioanal tables for X-ray

Crystallography Vol. 4, Kynoch Press, Birmingham, 1974.

2) Altomare, A. Burla, M. C., Camalli, M., Cascarano, G., Giacovazzo, C.,

Guagliardi, A., Polidori, G., J. Appl. Cryst., 1994, 27, 435.

3) Rae, A. D. Comprehensive constrained least squares refinement program,

University of New South Wales, 1989.

4) Johnson, C. K., ‘ORTEP-II’, Oak Ridge National Laboratory, Tennessee, U. S.

A., 1976.

277 data_dnk24

Formula C31H25BrO6, CDCl3; Formula weight, 692.8; Crystal system, monoclinic; Space

3 group, P21/c; a/Å, 11.435(4); b/Å, 24.743(7); c/Å, 12.355(4); /°, 111.03(2); V/Å ,

-3 -1 3263(2); Z, 4; Dc/Mgm , 1.41; (Mo-K) / Å, 0.71073; /mm , 1.536; Max/°, 25;

Observed reflections (I>2(I)), 2320; No. of refined parameters, 215; R1, 0.079; wR2,

0.107; GoF, 1.57.

ATOMIC COORDINATES AND DISPLACEMENT PARAMETERS

Br 0.75243(15) 0.69043(6) 0.43359(16) 0.0969(8) Uani Br 1.0 O1 0.8193(7) 0.3552(3) 0.4416(5) 0.043(1) Uani O 1.0 O2 0.6712(7) 0.3579(4) 0.7450(6) 0.067(3) Uani O 1.0 O3 1.0870(6) 0.3325(3) 0.9939(6) 0.050(2) Uani O 1.0 O4 0.2177(9) 0.4235(4) 0.1238(7) 0.091(3) Uani O 1.0 O5 0.8883(8) 0.4797(3) 0.1936(6) 0.066(2) Uani O 1.0 O6 0.9746(8) 0.2961(3) 0.1445(6) 0.065(3) Uani O 1.0 C1 0.7914(9) 0.4062(4) 0.4703(8) 0.038(1) Uani C 1.0 C2 0.8109(9) 0.4441(4) 0.3978(8) 0.039(1) Uani C 1.0 C3 0.8515(9) 0.4143(4) 0.3173(8) 0.038(1) Uani C 1.0 C4 0.8904(10) 0.4274(4) 0.2239(8) 0.047(1) Uani C 1.0 C5 0.9297(11) 0.3864(4) 0.1707(9) 0.050(2) Uani C 1.0 C6 0.9309(11) 0.3327(4) 0.2054(9) 0.050(1) Uani C 1.0 C7 0.8958(11) 0.3183(4) 0.2976(9) 0.050(2) Uani C 1.0 C8 0.8571(10) 0.3612(4) 0.3495(8) 0.040(1) Uani C 1.0 C9 0.7413(9) 0.4096(4) 0.5637(8) 0.039(2) Uani C 1.0 C10 0.6202(10) 0.3751(5) 0.5390(9) 0.050(2) Uani C 1.0 C11 0.5801(11) 0.3793(6) 0.6398(10) 0.069(4) Uani C 1.0 C12 0.7937(9) 0.3666(5) 0.7625(8) 0.046(2) Uani C 1.0 C13 0.8763(10) 0.3453(5) 0.8667(9) 0.050(2) Uani C 1.0 C14 1.0012(10) 0.3518(4) 0.8917(8) 0.042(1) Uani C 1.0 C15 1.0465(9) 0.3765(4) 0.8127(8) 0.042(2) Uani C 1.0 C16 0.9634(10) 0.3951(4) 0.7095(8) 0.039(2) Uani C 1.0 C17 0.8365(9) 0.3904(4) 0.6814(8) 0.037(2) Uani C 1.0 C18 0.5166(10) 0.3895(5) 0.4263(9) 0.049(3) Uani C 1.0 C19 0.4859(12) 0.4418(5) 0.3855(10) 0.065(3) Uani C 1.0 C20 0.3872(13) 0.4521(5) 0.2844(10) 0.072(3) Uani C 1.0 C21 0.3146(12) 0.4105(6) 0.2216(10) 0.073(2) Uani C 1.0 C22 0.3413(13) 0.3593(5) 0.2647(10) 0.078(3) Uani C 1.0 C23 0.4404(11) 0.3480(5) 0.3659(10) 0.062(3) Uani C 1.0 C24 0.7946(10) 0.5032(4) 0.4044(9) 0.044(2) Uani C 1.0 C25 0.8481(10) 0.5306(4) 0.5106(10) 0.049(2) Uani C 1.0 C26 0.8355(11) 0.5854(5) 0.5196(11) 0.059(2) Uani C 1.0 C27 0.7683(11) 0.6140(5) 0.4224(12) 0.061(3) Uani C 1.0 C28 0.7102(11) 0.5883(5) 0.3148(11) 0.064(4) Uani C 1.0 C29 0.7252(11) 0.5338(5) 0.3084(9) 0.055(3) Uani C 1.0 C30 0.9210(20) 0.4920(5) 0.0938(13) 0.124(7) Uani C 1.0 C31 0.9796(18) 0.2415(5) 0.1734(14) 0.108(6) Uani C 1.0

278 C1Ch 0.5112(25) 0.1627(9) 0.5735(26) 0.208(6) Uani C 0.29 Cl1Ch 0.5925(15) 0.2271(10) 0.6368(17) 0.142(6) Uani Cl 0.29 Cl2Ch 0.3736(18) 0.1932(15) 0.4571(32) 0.234(9) Uani Cl 0.29 Cl3Ch 0.6056(28) 0.1460(15) 0.4820(31) 0.289(9) Uani Cl 0.29 C1Ch' 0.5488(14) 0.1587(7) 0.5673(13) 0.213(6) Uani C 0.46 Cl1Ch' 0.3791(13) 0.1759(8) 0.4976(21) 0.249(9) Uani Cl 0.46 Cl2Ch' 0.5406(24) 0.0885(6) 0.5092(21) 0.404(9) Uani Cl 0.46 Cl3Ch' 0.6050(16) 0.1930(7) 0.4605(17) 0.250(9) Uani Cl 0.46 C1Ch'' 0.5950(13) 0.1865(7) 0.5485(13) 0.188(6) Uani C 0.25 Cl1Ch'' 0.5524(26) 0.1186(7) 0.5895(20) 0.320(9) Uani Cl 0.25 Cl2Ch'' 0.4509(18) 0.1978(9) 0.4179(14) 0.213(7) Uani Cl 0.25 Cl3Ch'' 0.5481(16) 0.2275(8) 0.6533(15) 0.143(6) Uani Cl 0.25 H1O3 1.0464 0.3194 1.0484 0.060 Uani H 1.0 H1O4 0.1719 0.3916 0.0783 0.112 Uani H 1.0 HC5 0.9583 0.3952 0.1052 0.060 Uani H 1.0 HC7 0.8982 0.2801 0.3248 0.064 Uani H 1.0 HC9 0.7201 0.4482 0.5719 0.047 Uani H 1.0 HC10 0.6432 0.3365 0.5332 0.054 Uani H 1.0 H1C11 0.4999 0.3589 0.6222 0.091 Uani H 1.0 H2C11 0.5659 0.4183 0.6525 0.077 Uani H 1.0 HC13 0.8443 0.3257 0.9213 0.067 Uani H 1.0 HC15 1.1387 0.3806 0.8315 0.052 Uani H 1.0 HC16 0.9961 0.4126 0.6531 0.049 Uani H 1.0 HC19 0.5367 0.4726 0.4307 0.088 Uani H 1.0 HC20 0.3681 0.4901 0.2562 0.094 Uani H 1.0 HC22 0.2870 0.3288 0.2215 0.111 Uani H 1.0 HC23 0.4568 0.3100 0.3951 0.077 Uani H 1.0 HC25 0.8966 0.5095 0.5816 0.060 Uani H 1.0 HC26 0.8749 0.6042 0.5958 0.077 Uani H 1.0 HC28 0.6592 0.6094 0.2448 0.085 Uani H 1.0 HC29 0.6849 0.5152 0.2321 0.071 Uani H 1.0 H1C30 0.9160 0.5319 0.0803 0.124 Uani H 1.0 H2C30 1.0083 0.4793 0.1079 0.124 Uani H 1.0 H3C30 0.8614 0.4732 0.0241 0.124 Uani H 1.0 H1C31 1.0131 0.2204 0.1219 0.108 Uani H 1.0 H2C31 1.0359 0.2366 0.2561 0.108 Uani H 1.0 H3C31 0.8936 0.2284 0.1631 0.108 Uani H 1.0 H1Ch 0.4975 0.1345 0.6257 0.308 Uani H 0.29 H1Ch' 0.5928 0.1654 0.6521 0.225 Uani H 0.46 H1Ch'' 0.6793 0.1921 0.5431 0.262 Uani H 0.25

Br 0.094(1) 0.0508(8) 0.164(2) 0.0029(9) 0.069(1) 0.001(1) Br O1 0.059(3) 0.043(2) 0.032(2) -0.004(2) 0.022(2) 0.002(2) O O2 0.043(2) 0.122(6) 0.041(2) -0.010(3) 0.019(2) 0.017(3) O O3 0.055(3) 0.058(4) 0.028(2) -0.008(3) 0.006(2) 0.001(2) O O4 0.088(5) 0.086(5) 0.061(3) -0.002(4) -0.021(3) 0.012(3) O O5 0.122(6) 0.045(2) 0.053(3) 0.004(4) 0.058(4) 0.007(3) O O6 0.112(6) 0.046(3) 0.058(4) 0.002(3) 0.058(4) 0.003(3) O C1 0.044(3) 0.044(2) 0.027(2) -0.004(2) 0.013(2) 0.002(2) C C2 0.047(3) 0.044(2) 0.026(2) -0.001(2) 0.014(2) 0.003(2) C C3 0.046(3) 0.044(2) 0.025(2) -0.002(2) 0.013(2) 0.002(2) C C4 0.071(3) 0.045(2) 0.035(2) -0.001(2) 0.028(2) 0.003(2) C C5 0.075(5) 0.045(2) 0.039(3) -0.003(2) 0.032(3) 0.002(2) C C6 0.076(3) 0.045(2) 0.041(2) -0.002(2) 0.034(2) 0.002(2) C C7 0.075(4) 0.044(2) 0.040(2) -0.001(2) 0.033(3) 0.003(2) C

279 C8 0.049(3) 0.043(2) 0.028(2) -0.004(2) 0.016(2) 0.002(2) C C9 0.040(2) 0.050(3) 0.026(2) -0.005(2) 0.011(1) -0.003(2) C C10 0.039(2) 0.071(4) 0.035(2) -0.011(2) 0.009(2) 0.005(2) C C11 0.039(2) 0.126(7) 0.045(3) -0.004(2) 0.017(2) 0.015(4) C C12 0.041(2) 0.072(3) 0.028(2) -0.007(2) 0.015(2) 0.003(2) C C13 0.048(2) 0.075(4) 0.028(2) -0.010(2) 0.014(2) 0.006(2) C C14 0.046(2) 0.053(3) 0.026(2) -0.007(2) 0.010(1) -0.001(2) C C15 0.040(2) 0.054(3) 0.029(2) -0.008(2) 0.009(2) -0.001(2) C C16 0.038(2) 0.053(3) 0.027(2) -0.009(2) 0.011(1) -0.001(2) C C17 0.038(2) 0.048(3) 0.025(2) -0.006(2) 0.013(1) -0.003(2) C C18 0.037(4) 0.064(5) 0.042(3) -0.002(3) 0.009(3) 0.004(3) C C19 0.064(5) 0.065(4) 0.048(3) -0.007(4) -0.001(3) 0.008(3) C C20 0.076(5) 0.067(4) 0.050(3) 0.000(3) -0.005(3) 0.007(3) C C21 0.069(4) 0.073(4) 0.052(3) -0.002(3) -0.009(3) 0.007(3) C C22 0.078(5) 0.071(3) 0.053(3) -0.010(4) -0.015(3) 0.007(3) C C23 0.060(5) 0.064(4) 0.045(3) -0.003(4) -0.002(3) 0.002(3) C C24 0.048(5) 0.044(3) 0.046(4) 0.003(3) 0.023(4) 0.002(3) C C25 0.045(5) 0.049(3) 0.052(4) 0.001(3) 0.016(4) -0.004(3) C C26 0.053(5) 0.050(3) 0.075(4) -0.003(4) 0.025(4) -0.013(3) C C27 0.063(7) 0.043(3) 0.091(6) 0.003(3) 0.044(6) 0.004(3) C C28 0.078(7) 0.056(3) 0.068(4) 0.015(4) 0.040(5) 0.021(4) C C29 0.069(6) 0.057(4) 0.046(4) 0.010(4) 0.028(4) 0.009(3) C C30 0.277(9) 0.052(9) 0.100(9) 0.016(9) 0.139(9) 0.014(8) C C31 0.208(9) 0.047(8) 0.123(9) 0.022(9) 0.125(9) 0.004(8) C C1Ch 0.196(9) 0.202(9) 0.231(9) 0.013(7) 0.082(7) 0.031(6) C Cl1Ch 0.073(7) 0.206(9) 0.178(8) 0.035(7) 0.084(6) 0.036(7) Cl Cl2Ch 0.119(6) 0.286(9) 0.277(9) 0.010(7) 0.048(7) -0.024(9) Cl Cl3Ch 0.240(9) 0.339(9) 0.277(9) 0.138(9) 0.077(9) -0.054(9) Cl C1Ch' 0.198(9) 0.206(9) 0.225(9) 0.050(7) 0.065(7) 0.022(7) C Cl1Ch' 0.142(6) 0.290(9) 0.316(9) -0.041(8) 0.084(8) -0.021(9) Cl Cl2Ch' 0.502(9) 0.232(9) 0.356(9) 0.105(9) 0.007(9) -0.033(9) Cl Cl3Ch' 0.194(9) 0.369(9) 0.246(9) 0.068(9) 0.151(9) -0.025(9) Cl C1Ch'' 0.121(6) 0.251(9) 0.212(9) 0.068(8) 0.085(6) 0.006(8) C Cl1Ch'' 0.403(9) 0.201(9) 0.293(9) 0.052(8) 0.048(9) 0.026(7) Cl Cl2Ch'' 0.181(9) 0.259(9) 0.192(8) 0.060(9) 0.060(6) 0.005(7) Cl Cl3Ch'' 0.089(8) 0.204(9) 0.175(8) 0.024(7) 0.095(6) 0.043(7) Cl

MOLECULAR GEOMETRY

Br C27 1.911(11) 1_555 1_555 no O1 C1 1.380(11) 1_555 1_555 no O1 C8 1.362(11) 1_555 1_555 no O2 C11 1.445(13) 1_555 1_555 no O2 C12 1.355(12) 1_555 1_555 no O3 C14 1.377(11) 1_555 1_555 no O4 C21 1.353(13) 1_555 1_555 no O5 C4 1.344(11) 1_555 1_555 no O5 C30 1.444(14) 1_555 1_555 no O6 C6 1.382(12) 1_555 1_555 no O6 C31 1.393(14) 1_555 1_555 no C1 C2 1.368(12) 1_555 1_555 no C1 C9 1.463(12) 1_555 1_555 no C2 C3 1.441(13) 1_555 1_555 no C2 C24 1.482(13) 1_555 1_555 no C3 C4 1.416(13) 1_555 1_555 no

280 C3 C8 1.368(13) 1_555 1_555 no C4 C5 1.368(13) 1_555 1_555 no C5 C6 1.394(14) 1_555 1_555 no C6 C7 1.384(13) 1_555 1_555 no C7 C8 1.393(13) 1_555 1_555 no C9 C10 1.560(14) 1_555 1_555 no C9 C17 1.546(13) 1_555 1_555 no C10 C11 1.478(14) 1_555 1_555 no C10 C18 1.512(14) 1_555 1_555 no C12 C13 1.399(13) 1_555 1_555 no C12 C17 1.394(13) 1_555 1_555 no C13 C14 1.358(14) 1_555 1_555 no C14 C15 1.399(13) 1_555 1_555 no C15 C16 1.367(12) 1_555 1_555 no C16 C17 1.370(13) 1_555 1_555 no C18 C19 1.387(15) 1_555 1_555 no C18 C23 1.379(15) 1_555 1_555 no C19 C20 1.374(15) 1_555 1_555 no C20 C21 1.373(16) 1_555 1_555 no C21 C22 1.367(16) 1_555 1_555 no C22 C23 1.382(15) 1_555 1_555 no C24 C25 1.406(14) 1_555 1_555 no C24 C29 1.390(14) 1_555 1_555 no C25 C26 1.373(15) 1_555 1_555 no C26 C27 1.367(16) 1_555 1_555 no C27 C28 1.406(16) 1_555 1_555 no C28 C29 1.366(15) 1_555 1_555 no C1Ch Cl1Ch 1.868(6) 1_555 1_555 no C1 O1 C8 106.7(7) 1_555 1_555 1_555 no C11 O2 C12 117.1(8) 1_555 1_555 1_555 no C4 O5 C30 117.1(9) 1_555 1_555 1_555 no C6 O6 C31 119.1(8) 1_555 1_555 1_555 no O1 C1 C2 110.5(8) 1_555 1_555 1_555 no O1 C1 C9 116.5(8) 1_555 1_555 1_555 no C2 C1 C9 132.8(9) 1_555 1_555 1_555 no C1 C2 C3 105.7(9) 1_555 1_555 1_555 no C1 C2 C24 125.9(9) 1_555 1_555 1_555 no C3 C2 C24 128.4(9) 1_555 1_555 1_555 no C2 C3 C4 136.0(9) 1_555 1_555 1_555 no C2 C3 C8 106.4(8) 1_555 1_555 1_555 no C4 C3 C8 117.5(9) 1_555 1_555 1_555 no O5 C4 C3 117.9(9) 1_555 1_555 1_555 no O5 C4 C5 123.7(9) 1_555 1_555 1_555 no C3 C4 C5 118.4(9) 1_555 1_555 1_555 no C4 C5 C6 121.8(9) 1_555 1_555 1_555 no O6 C6 C5 115.1(9) 1_555 1_555 1_555 no O6 C6 C7 123.2(9) 1_555 1_555 1_555 no C5 C6 C7 121.7(10) 1_555 1_555 1_555 no C6 C7 C8 114.6(9) 1_555 1_555 1_555 no O1 C8 C3 110.6(8) 1_555 1_555 1_555 no O1 C8 C7 123.3(9) 1_555 1_555 1_555 no C3 C8 C7 126.0(9) 1_555 1_555 1_555 no C1 C9 C10 112.7(8) 1_555 1_555 1_555 no C1 C9 C17 112.4(8) 1_555 1_555 1_555 no C10 C9 C17 107.1(8) 1_555 1_555 1_555 no

281 C9 C10 C11 108.5(9) 1_555 1_555 1_555 no C9 C10 C18 113.5(9) 1_555 1_555 1_555 no C11 C10 C18 112.5(9) 1_555 1_555 1_555 no O2 C11 C10 113.0(10) 1_555 1_555 1_555 no O2 C12 C13 113.8(9) 1_555 1_555 1_555 no O2 C12 C17 124.2(9) 1_555 1_555 1_555 no C13 C12 C17 121.7(9) 1_555 1_555 1_555 no C12 C13 C14 118.1(10) 1_555 1_555 1_555 no O3 C14 C13 120.8(9) 1_555 1_555 1_555 no O3 C14 C15 118.0(9) 1_555 1_555 1_555 no C13 C14 C15 121.1(10) 1_555 1_555 1_555 no C14 C15 C16 119.3(9) 1_555 1_555 1_555 no C15 C16 C17 121.8(9) 1_555 1_555 1_555 no C9 C17 C12 119.7(9) 1_555 1_555 1_555 no C9 C17 C16 122.5(9) 1_555 1_555 1_555 no C12 C17 C16 117.8(9) 1_555 1_555 1_555 no C10 C18 C19 124.5(10) 1_555 1_555 1_555 no C10 C18 C23 117.2(10) 1_555 1_555 1_555 no C19 C18 C23 118.0(10) 1_555 1_555 1_555 no C18 C19 C20 121.5(11) 1_555 1_555 1_555 no C19 C20 C21 120.4(12) 1_555 1_555 1_555 no O4 C21 C20 117.5(12) 1_555 1_555 1_555 no O4 C21 C22 124.4(12) 1_555 1_555 1_555 no C20 C21 C22 118.0(11) 1_555 1_555 1_555 no C21 C22 C23 122.4(12) 1_555 1_555 1_555 no C18 C23 C22 119.5(11) 1_555 1_555 1_555 no C2 C24 C25 120.4(9) 1_555 1_555 1_555 no C2 C24 C29 122.3(10) 1_555 1_555 1_555 no C25 C24 C29 117.3(10) 1_555 1_555 1_555 no C24 C25 C26 121.8(11) 1_555 1_555 1_555 no C25 C26 C27 118.8(11) 1_555 1_555 1_555 no Br C27 C26 119.1(10) 1_555 1_555 1_555 no Br C27 C28 119.4(9) 1_555 1_555 1_555 no C26 C27 C28 121.6(11) 1_555 1_555 1_555 no C27 C28 C29 118.3(11) 1_555 1_555 1_555 no C24 C29 C28 122.2(11) 1_555 1_555 1_555 no Cl1Ch C1Ch Cl2Ch 97.7(3) 1_555 1_555 1_555 no

C8 O1 C1 C2 0.0(11) 1_555 1_555 1_555 1_555 no C8 O1 C1 C9 176.5(8) 1_555 1_555 1_555 1_555 no C1 O1 C8 C3 -1.3(11) 1_555 1_555 1_555 1_555 no C1 O1 C8 C7 178.5(10) 1_555 1_555 1_555 1_555 no C12 O2 C11 C10 37.8(15) 1_555 1_555 1_555 1_555 no C11 O2 C12 C13 179.3(10) 1_555 1_555 1_555 1_555 no C11 O2 C12 C17 -6.0(16) 1_555 1_555 1_555 1_555 no C30 O5 C4 C3 -176.3(12) 1_555 1_555 1_555 1_555 no C30 O5 C4 C5 4.7(18) 1_555 1_555 1_555 1_555 no C31 O6 C6 C5 179.8(13) 1_555 1_555 1_555 1_555 no C31 O6 C6 C7 2.5(18) 1_555 1_555 1_555 1_555 no O1 C1 C2 C3 1.1(11) 1_555 1_555 1_555 1_555 no O1 C1 C2 C24 -178.1(9) 1_555 1_555 1_555 1_555 no C9 C1 C2 C3 -174.6(10) 1_555 1_555 1_555 1_555 no C9 C1 C2 C24 6.2(18) 1_555 1_555 1_555 1_555 no O1 C1 C9 C10 -56.8(11) 1_555 1_555 1_555 1_555 no O1 C1 C9 C17 64.3(11) 1_555 1_555 1_555 1_555 no

282 C2 C1 C9 C10 118.7(12) 1_555 1_555 1_555 1_555 no C2 C1 C9 C17 -120.2(12) 1_555 1_555 1_555 1_555 no C1 C2 C3 C4 -177.7(12) 1_555 1_555 1_555 1_555 no C1 C2 C3 C8 -1.8(11) 1_555 1_555 1_555 1_555 no C24 C2 C3 C4 1.5(20) 1_555 1_555 1_555 1_555 no C24 C2 C3 C8 177.3(10) 1_555 1_555 1_555 1_555 no C1 C2 C24 C25 48.9(16) 1_555 1_555 1_555 1_555 no C1 C2 C24 C29 -130.0(12) 1_555 1_555 1_555 1_555 no C3 C2 C24 C25 -130.1(11) 1_555 1_555 1_555 1_555 no C3 C2 C24 C29 51.0(16) 1_555 1_555 1_555 1_555 no C2 C3 C4 O5 -2.8(18) 1_555 1_555 1_555 1_555 no C2 C3 C4 C5 176.3(11) 1_555 1_555 1_555 1_555 no C8 C3 C4 O5 -178.3(9) 1_555 1_555 1_555 1_555 no C8 C3 C4 C5 0.8(15) 1_555 1_555 1_555 1_555 no C2 C3 C8 O1 2.0(11) 1_555 1_555 1_555 1_555 no C2 C3 C8 C7 -177.8(10) 1_555 1_555 1_555 1_555 no C4 C3 C8 O1 178.7(9) 1_555 1_555 1_555 1_555 no C4 C3 C8 C7 -1.1(16) 1_555 1_555 1_555 1_555 no O5 C4 C5 C6 179.6(11) 1_555 1_555 1_555 1_555 no C3 C4 C5 C6 0.6(17) 1_555 1_555 1_555 1_555 no C4 C5 C6 O6 -179.2(10) 1_555 1_555 1_555 1_555 no C4 C5 C6 C7 -1.9(18) 1_555 1_555 1_555 1_555 no O6 C6 C7 C8 178.6(10) 1_555 1_555 1_555 1_555 no C5 C6 C7 C8 1.5(17) 1_555 1_555 1_555 1_555 no C6 C7 C8 O1 -179.8(9) 1_555 1_555 1_555 1_555 no C6 C7 C8 C3 0.0(17) 1_555 1_555 1_555 1_555 no C1 C9 C10 C11 177.7(9) 1_555 1_555 1_555 1_555 no C1 C9 C10 C18 -56.4(12) 1_555 1_555 1_555 1_555 no C17 C9 C10 C11 53.6(11) 1_555 1_555 1_555 1_555 no C17 C9 C10 C18 179.4(9) 1_555 1_555 1_555 1_555 no C1 C9 C17 C12 -149.5(9) 1_555 1_555 1_555 1_555 no C1 C9 C17 C16 29.4(13) 1_555 1_555 1_555 1_555 no C10 C9 C17 C12 -25.2(12) 1_555 1_555 1_555 1_555 no C10 C9 C17 C16 153.7(10) 1_555 1_555 1_555 1_555 no C9 C10 C11 O2 -62.5(13) 1_555 1_555 1_555 1_555 no C18 C10 C11 O2 171.0(10) 1_555 1_555 1_555 1_555 no C9 C10 C18 C19 -40.6(15) 1_555 1_555 1_555 1_555 no C9 C10 C18 C23 145.8(10) 1_555 1_555 1_555 1_555 no C11 C10 C18 C19 83.1(14) 1_555 1_555 1_555 1_555 no C11 C10 C18 C23 -90.5(13) 1_555 1_555 1_555 1_555 no O2 C12 C13 C14 179.7(10) 1_555 1_555 1_555 1_555 no C17 C12 C13 C14 4.9(17) 1_555 1_555 1_555 1_555 no O2 C12 C17 C9 1.1(16) 1_555 1_555 1_555 1_555 no O2 C12 C17 C16 -177.9(10) 1_555 1_555 1_555 1_555 no C13 C12 C17 C9 175.4(10) 1_555 1_555 1_555 1_555 no C13 C12 C17 C16 -3.6(16) 1_555 1_555 1_555 1_555 no C12 C13 C14 O3 178.9(9) 1_555 1_555 1_555 1_555 no C12 C13 C14 C15 -3.6(17) 1_555 1_555 1_555 1_555 no O3 C14 C15 C16 178.7(9) 1_555 1_555 1_555 1_555 no C13 C14 C15 C16 1.1(16) 1_555 1_555 1_555 1_555 no C14 C15 C16 C17 0.3(16) 1_555 1_555 1_555 1_555 no C15 C16 C17 C9 -178.0(9) 1_555 1_555 1_555 1_555 no C15 C16 C17 C12 0.9(15) 1_555 1_555 1_555 1_555 no C10 C18 C19 C20 -177.4(11) 1_555 1_555 1_555 1_555 no C23 C18 C19 C20 -3.8(19) 1_555 1_555 1_555 1_555 no

283 C10 C18 C23 C22 177.5(11) 1_555 1_555 1_555 1_555 no C19 C18 C23 C22 3.4(18) 1_555 1_555 1_555 1_555 no C18 C19 C20 C21 1.1(21) 1_555 1_555 1_555 1_555 no C19 C20 C21 O4 179.0(12) 1_555 1_555 1_555 1_555 no C19 C20 C21 C22 2.0(21) 1_555 1_555 1_555 1_555 no O4 C21 C22 C23 -179.1(13) 1_555 1_555 1_555 1_555 no C20 C21 C22 C23 -2.4(22) 1_555 1_555 1_555 1_555 no C21 C22 C23 C18 -0.4(21) 1_555 1_555 1_555 1_555 no C2 C24 C25 C26 179.5(10) 1_555 1_555 1_555 1_555 no C29 C24 C25 C26 -1.6(16) 1_555 1_555 1_555 1_555 no C2 C24 C29 C28 179.9(11) 1_555 1_555 1_555 1_555 no C25 C24 C29 C28 1.1(17) 1_555 1_555 1_555 1_555 no C24 C25 C26 C27 0.5(17) 1_555 1_555 1_555 1_555 no C25 C26 C27 Br -179.1(8) 1_555 1_555 1_555 1_555 no C25 C26 C27 C28 1.2(18) 1_555 1_555 1_555 1_555 no Br C27 C28 C29 178.6(9) 1_555 1_555 1_555 1_555 no C26 C27 C28 C29 -1.8(18) 1_555 1_555 1_555 1_555 no C27 C28 C29 C24 0.6(18) 1_555 1_555 1_555 1_555 no

284