THE SYNTHESIS OF NOVEL, BIOLOGICALLY ACTIVE ISOFLAVONE ANALOGUES
A thesis submitted in fulfilment of the requirements for the degree of
DOCTOR OF PHILOSOPHY
By
ELEANOR JANE EIFFE
Supervisors A/Prof. Naresh Kumar Prof. David StC. Black
School of Chemistry University of New South Wales Kensington, Australia
September, 2012
ORIGINALITY STATEMENT
‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have 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.’
Signed ……………………………………………......
Date ……………………………………………......
ii ABSTRACT
This thesis explores the synthesis of novel isoflavone analogues, with a particular focus on isoflavonoid compounds that are substituted at C2 or C4.
Isoflavylium salts were prepared via the treatment of isoflavenes with tritylium hexafluorophosphate or thallium trifluoroacetate. The reactivity of these salts towards nucleophiles was exploited to generate a diverse series of 2-substituted isoflavenes. Isoflavylium salts reacted readily with alkylzinc reagents, primary and secondary amines, thiols, indoles and α-methyl ketones. Some of the isoflavenes generated in this manner were reduced to the corresponding isoflavans.
2-Substituted isoflavenes were also synthesised via an alternative route. 2-Substituted isoflavones were prepared via the cyclisation of deoxybenzoins with symmetrical anhydrides or acyl chlorides. Reduction of the 2-substituted isoflavones to the corresponding isoflavanols, followed by acid-catalysed dehydration afforded 2- substituted isoflavenes. 2-Substitituted isoflavones were also partially reduced to the corresponding isoflavanones, which can serve as precursors to the synthesis of 4- substituted isoflavonoid compounds.
Isoflavene epoxides were also explored as potential precursors to 4-substituted isoflavonoid species. Novel epoxides were prepared via the oxidation of isoflavenes with meta-chloroperbenzoic acid. This reaction was found to generate meta- chlorobenzoate ester side products. These esters were converted to the corresponding epoxides via treatment with acid.
The biological activity of 2-substitued isoflavenes was also investigated. A number of the analogues synthesised as part of this project exhibited promising anti-cancer activity.
iii ACKNOWLEDGEMENTS
I would like to thank my supervisor A/Prof Naresh Kumar for all of his assistance and support. This project has not always run smoothly and I am grateful for the opportunity to see it through to completion. I must also thank my co-supervisor Prof. David StC Black for his advice and support. Special thanks to Dr Andrew Heaton, my former co- supervisor, who was instrumental in getting this project started and has remained a valuable mentor since. Acknowledgement must also go to Novogen for their funding and support of this project in its early stages.
I also wish to thank the technical staff at the School of Chemistry at UNSW for their assistance in completing this project. Thanks to Dr Donald Thomas and Dr Douglas Lawes for all their help and advice with NMR spectroscopy. Thank you to Lewis Adler and Leanne Stephenson of the Bioanalytical Mass Spectrometry Facility for running the HRMS analysis for this project. Thanks also to Dr Mohan Bhadbhade for the X-ray crystallography.
Anti-inflammatory assays were performed by Dr Catherine Walker at Novogen. Anti- cancer screening was performed by Christopher Gardner. Thanks also to Persefoni Thomopoulou and Ljiljana Sokolic for their assistance with the synthesis of isoflavene epoxides.
To all my research group members, past and present, both at Novogen and UNSW, many thanks for all your help and friendship over the years. In particular, thank you to Dr Kasey Wood for helping me settle in at UNSW and for her valuable advice during the writing process.
To everyone who has made me dinner, invited me out for drinks or otherwise reminded me that there is a whole world outside my PhD project: thank you. I’m very fortunate to have friends like you to keep me sane and grounded. A special mention must go to Scott Wickens, who not only kept me motivated and entertained through many a late night writing session, but also introduced me to doom metal, under the influence of which much of this thesis was written. And many, many thanks my best friend, Dan Staines,
iv who has been a much appreciated source of support and companionship for the duration of this project – and has granted me access to the world’s greatest cat. On that note, I’d also like to thank Mordin, as well as Trent and Wednesday, for supervising the production of this thesis at various stages, often while purring on my lap.
Finally, a very big thank you to my parents, without whose love and support I couldn’t have finished this project. Thanks for helping me get this far. I hope I can make you proud.
v TABLE OF CONTENTS ORIGINALITY STATEMENT...... ii ABSTRACT...... iii ACKNOWLEDGEMENTS ...... iv TABLE OF CONTENTS...... vi PUBLICATIONS AND PRESENTATIONS ...... ix
CHAPTER ONE: INTRODUCTION...... - 1 - 1.1 Background ...... - 1 - 1.1.1 Isoflavones and Estrogen Receptors ...... - 1 - 1.1.2 Anti-Cancer Activity of Isoflavone Analogues ...... - 4 - 1.1.3 Anti-Inflammatory Activity of Isoflavone Analogues...... - 6 - 1.1.4 Other Biological Activities of Isoflavone Analogues ...... - 7 - 1.2 Synthesis of Isoflavonoid Compounds ...... - 8 - 1.2.1 Synthesis of Isoflavones...... - 8 - 1.2.2 Synthesis of Isoflavanols and Isoflavanones ...... - 12 - 1.2.3 Synthesis of Isoflavenes and Isoflavans...... - 13 - 1.2.4 Synthesis of 2-Substituted Isoflavonoid Compounds ...... - 14 - 1.2.5 Synthesis of 4-Substituted Isoflavans ...... - 16 - 1.3 Synthetic Targets...... - 20 - 1.4 Thesis Aims...... - 21 - 1.4.1 2-Substituted Isoflavenes via Isoflavylium Chemistry ...... - 21 - 1.4.2 2-Substituted Isoflavenes from 2-Substituted Isoflavones...... - 22 - 1.4.3 Synthesis of Isoflavene Epoxides ...... - 23 - CHAPTER TWO: SYNTHESIS OF ISOFLAVYLIUM SALTS ...... - 24 - 2.1 Background ...... - 24 - 2.1.1 Synthesis of Isoflavylium Salts...... - 26 - 2.2 Preparation of Isoflavylium Salts using Tritylium Hexafluorophosphate ...... - 31 - 2.3 Preparation of Isoflavylium Salts via 2-Hydroxyisoflavenes ...... - 34 - 2.4 Stability of Isoflavylium Salts...... - 36 - 2.5 Conclusion ...... - 36 -
vi CHAPTER THREE: SYNTHESIS OF 2-SUBSTITUTED ISOFLAVENES FROM ISOFLAVYLIUM SALTS ...... - 37 - 3.1 Background ...... - 37 - 3.2 Reactions of Isoflavylium Salts with Organozinc Compounds ...... - 40 - 3.3 Reactions of Isoflavylium Salts with Amines...... - 47 - 3.3.1 Reactions of Isoflavylium Salts with Dimethylanilines...... - 50 - 3.3.2 Reactions of Isoflavylium Salts with Nitrogen Heterocycles ...... - 53 - 3.4. Reactions of Isoflavylium Salts with Thiols...... - 55 - 3.5 Reactions of Isoflavylium Salts with Indoles ...... - 57 - 3.6 Reactions of Isoflavylium Salts with α-Methyl Ketones ...... - 60 - 3.6.1 Reactions of Isoflavylium Salts with Acetone...... - 61 - 3.6.2 Reaction of the Isoflavylium Salt 112 with 4-Methylpentan-2-one...... - 64 - 3.6.3 Reactions of Isoflavylium Salt 55 with Acetophenones ...... - 65 - 3.6.4 Reactions of Isoflavylium Salt 55 with Other Acetyl-Substituted Aromatics...... - 69 - 3.6.5 Derivatives of Carbonyl Compounds...... - 71 - 3.7 Reduction of 2-Substituted Isoflavenes to Isoflavans...... - 74 - 3.8 Conclusion ...... - 77 - CHAPTER FOUR: SYNTHESIS OF 2-SUBSTITUTED ISOFLAVENES FROM 2-SUBSTITUTED ISOFLAVONES ...... - 78 - 4.1 Background ...... - 78 - 4.1.1 Synthesis of Isoflavenes from Isoflavones...... - 78 - 4.1.2 Synthesis of 2-Substituted Isoflavones ...... - 78 - 4.2 Synthesis of 2-Substituted Isoflavones via Cyclisation of Deoxybenzoins..... - 80 - 4.3 Synthesis of 2-Substituted Isoflavanols ...... - 85 - 4.4. Dehydration of 2-Substituted Isoflavanols...... - 89 - 4.4 Synthesis of Isoflavanones...... - 91 - 4.5. Conclusion ...... - 92 - CHAPTER FIVE: PREPARATION OF ISOFLAVENE EPOXIDES...... - 93 - 5.1 Background ...... - 93 - 5.2 Synthesis of Isoflav-3-ene Epoxides...... - 96 - 5.2.1 Synthesis of Epoxides from Isoflavenes ...... - 96 - 5.2.2 Synthesis of Epoxides from Isoflavanol Esters...... - 99 - 5.3 Ring-Opening Reactions on Isoflavene Epoxides...... - 103 -
vii 5.4 Conclusion ...... - 104 - CHAPTER SIX: BIOLOGICAL ACTIVITY...... - 105 - 6.1 Introduction...... - 105 - 6.2 Anti-inflammatory Activity ...... - 105 - 6.2.1 Inhibition of Eicosanoid Synthesis...... - 106 - 6.2.2 Inhibition of Nitric Oxide Synthesis ...... - 110 - 6.3 Anti-Cancer Activity...... - 113 - 6.4 Conclusion ...... - 117 - CHAPTER SEVEN: CONCLUSIONS AND FUTURE WORK ...... - 118 - CHAPTER EIGHT: EXPERIMENTAL...... - 120 - 8.1. General Information...... - 120 - 8.2 Experimental Details...... - 122 - CHAPTER NINE: REFERENCES...... - 205 -
viii PUBLICATIONS AND PRESENTATIONS
Publications:
Eiffe, E., Heaton, A., Walker, C., Husband, A., 2-Substituted Isoflavonoid Compounds, Medicaments and Uses, PCT Int. Appl., 2009, WO 2009/003229.
Presentations:
Eiffe, E., Black, D. StC., Kumar, N., Synthesis of Novel, Biologically Active Isoflavone Analogues, UNSW Medicinal Chemistry/Drug Discovery Symposium, Sydney, NSW, November, 2011. (Poster presentation)
Eiffe, E., Heaton, A., Black, D. StC., Kumar, N., Synthesis of Novel, Biologically Active Isoflavone Analogues, RACI Natural Products One-day Symposium, Sydney, NSW, October, 2010. (Poster presentation)
Eiffe, E., Heaton, A., Black, D. StC., Kumar, N., Synthesis of Novel, Biologically Active Isoflavone Analogues, The NSW Southern Highlands Conference on Heterocyclic Chemistry, Moss Vale, NSW, August 2010. (Poster presentation)
Eiffe, E., Heaton, A., Black, D. StC., Kumar, N., Synthesis of Novel, Biologically Active Isoflavone Analogues, 30th RACI Organic Chemistry Division One-day Symposium, Sydney, NSW, 2 December, 2009. (Poster presentation)
Eiffe, E., Heaton, A., Black, D. StC., Kumar, N., Synthesis of Novel, Biologically Active Isoflavone Analogues, RACI Natural Products One-day Symposium, Newcastle, NSW, October, 2009. (Poster presentation, winner of best student poster award)
ix CHAPTER ONE
INTRODUCTION
1.1 Background The isoflavones are a class of γ-benzopyrones found in plants of the Leguminosae- Papilionoideae family, where they function as a defence against pathogens and play an essential role in the formation of root nodules by nitrogen-fixing bacteria.1-5 Isoflavonoid compounds are the subject of considerable research interest due to their biological activity in humans. Dietary intake of soy, which contains the isoflavones daidzein 1 and genistein 2, has been linked with a lower incidence of some cancers,6-13 as well as a reduced risk of cardiovascular disease.12-17
1.1.1 Isoflavones and Estrogen Receptors Isoflavones are classified as phytoestrogens, which are non-steroidal, plant-derived compounds that bind to estrogen receptors (ERs). This property of isoflavones was first discovered in the 1940s, when it was observed that sheep developed reproductive abnormalities after grazing on subterranean clover rich in genistein 2 and formononetin 3.18,19 The estrogenic properties of isoflavones have since been studied extensively.6- 13,17,20-30 The ability of isoflavones to bind to the ER active site can be attributed to their structural similarity to endogenous estrogens such as 17β-estradiol 4. While genistein 2 is the most potent of the isoflavone phytoestrogens, S-equol 5, an isoflavan metabolite of daidzein 1, has an ER binding affinity greater than that of genistein.13,27-29 It has been estimated that approximately 30–50% of humans possess the intestinal flora necessary to produce equol, while 80–90% of the population convert daidzein to O- desmethylangolensin 6.31-33,27 The latter metabolite (6) has also been found to bind to estrogen receptors in vitro.27
‐ 1 ‐
The so-called “clover disease” in sheep illustrated the ability of isoflavones to exert both estrogenic and antiestrogenic effects. Some sheep, including castrated males, developed pronounced udders and, in some cases, produced milk after eating clover. Ewes grazing in the same pastures were often infertile or had difficulty giving birth.18 Whether isoflavones act as estrogens or antiestrogens depends on a number of factors, including the concentration of isoflavones and their metabolites, as well as the relative concentration of endogenous ER ligands.11,21,24 Isoflavones are weaker ER agonists than 17β-estradiol 4 and other endogenous estrogens. Thus, the estrogenic effects of isoflavones are primarily observed when endogenous estrogen levels are low. When the concentration of endogenous estrogens is high, isoflavonoid compounds can exhibit antiestrogenic activity via competitive binding20,25 or other mechanisms.23,24 This phenomenon is thought to contribute to the chemoprotective effects of isoflavones against hormone-dependent cancers.13,20,25
Estrogen receptors exist as two subtypes: ERα, which is found in the adrenal glands, kidneys and testes, and ERβ, which is expressed in a variety of tissues, including the bones, brain, vasculature and prostate. ERα and ERβ are co-expressed in the breast, ovaries and uterus.21 Unlike 17β-estradiol, isoflavones and their metabolites differentiate between the two ER subtypes, with greater binding affinity for ERβ than ERα.11,13,20-23,25,27,29 This selectivity, as well as the capacity of isoflavones to act as both estrogens and antiestrogens, has led to the development of isoflavonoid selective estrogen receptor modulators, or SERMs. Unlike pure estrogens or antiestrogens, SERMs have the potential to exert estrogenic or antiestrogenic effects on a tissue- dependent basis.
Acolbifene 7, a SERM developed for the treatment of hormone-dependent breast cancer, is a potent antiestrogen in the tissues of the breast and uterus, but acts as an estrogen agonist elsewhere, notably in the bones.34-39 Similarly, ormeloxifene 8, initially
‐ 2 ‐ developed as a contraceptive due to its antiestrogenic activity in the female reproductive system, has been found to prevent bone loss in ovariectomised rats.40-46 The tissue- dependent activity of SERMs such as ormeloxifene means that these compounds can potentially be used to treat or prevent osteoporosis, while avoiding the side effects associated with conventional estrogen replacement therapy, such as uterine bleeding, endometrial hyperplasia and an increased risk of breast cancer.47 Ormeloxifene and another isoflavonoid SERM, CDRI-85/287 9, have also shown potential for the treatment of benign prostate hyperplasia and prostate cancer due to their interactions with ERβ.44 While most isoflavonoid compounds preferentially bind to ERβ, SERMs such as the 2,3-diarylbenzopyranone 10 have been developed as antiestrogens with a high degree of selectivity for ERα.48-50
MeO O O N R2 O 2
3 4 R1 R2 O N 7 R1 =Me,R2 =OH 8 9 R1 =R2 =H OH O N O HO O
O OH
O 10 11 R
Structurally, the SERMs described above share similarities beyond their isoflavonoid character. Compounds 7, 9 and 10 all feature a 2,3-diarylbenzopyran motif, and as such they could effectively be considered as 2-aryl isoflavonoids or 3-aryl flavonoids. Ormeloxifene 8 is substituted at C2 with non-aryl groups, instead bearing two methyl groups at that position. Acolbifene 7 and ormeloxifene 8 are substituted at C4 with a methyl group and a para-substituted phenyl ring, respectively. Kumar and co-workers51 sought to capitalise on the activity of both acolbifene and ormeloxifene by synthesising
‐ 3 ‐ a series of hybrid 2,3,4-triarylbenzopyrans 11 for the potential treatment of breast cancer. Interestingly, the analogues with the greatest anti-proliferative activity did not interact significantly with estrogen receptors, implying an ER-independent mechanism of action.
1.1.2 Anti-Cancer Activity of Isoflavone Analogues Natural and synthetic isoflavone analogues have demonstrated significant potential as anti-cancer agents. Genistein 2 has been reported to exhibit in vitro anti-proliferative activity against both ER-positive and ER-negative breast cancers,52,53 as well as pancreatic cancer,54 leukaemia,55 melanoma56 and neuroblastoma.57 Genistein, daidzein and biochanin A 12 have been shown to inhibit the growth of prostate cancer in vitro.9,58 Genistein and biochanin A have also demonstrated some in vitro activity against cancers of the gastrointestinal tract59. Another isoflavonoid natural product, mucronolactol 13, has demonstrated promising in vitro activity against lung cancer,60,skin cancer60 and leukemia61. Of the natural isoflavones, genistein has been the best studied in terms of its anti-cancer activity and mechanism of action. Genistein inhibits a number of biological targets, including protein tyrosine kinases52,62 and DNA- topoisomerases63. These actions result in cell cycle arrest and the induction of apoptosis. Additionally, the anti-angiogenic activity of genistein has been reported.64,65 Isoflavone natural products are attractive potential drug candidates, due their multiple modes of action and their low toxicity towards normal cells.7,54,65 While there is some evidence that dietary supplementation with daidzein, genistein and equol may be beneficial for men with recurrent prostate cancer,66 the limited bioavailability of most isoflavonoid compounds means that is often difficult or impossible to achieve the blood concentrations necessary for anti-cancer activity in vivo.7,54
While natural isoflavonoid compounds have so far proven to be of limited utility in the clinic, synthetic isoflavonoid compounds continue to attract the interest of the pharmaceutical industry. Phenoxodiol 14 is an isoflavene derived from daidzein. It has
‐ 4 ‐ demonstrated cytotoxic, anti-proliferative and anti-angiogenic activity against a variety of cancer types, notably ovarian and prostate cancers.7,54,67 As well as being an effective monotherapy, phenoxodiol can act as a chemosensitiser when paired with other treatments.7,68 Phenoxodiol disrupts the cell cycle and induces apoptosis via caspase- dependent and caspase-independent pathways. Like genistein, phenoxodiol is a potent inhibitor of protein tyrosine kinases and DNA-topoisomerases. Additionally, phenoxodiol inhibits sphingosine kinase. This mode of action is thought to contribute to phenoxodiol’s anti-angiogenic activity.7,67 Crucially, phenoxodiol’s cytotoxic and anti- proliferative actions are targeted almost exclusively at cancer cells. This selectivity is linked to cell surface proteins known as NADH oxidases (NOX). Cancer cells and normal cells express different NOX isoforms. Phenoxodiol binds selectively to the NOX isoforms expressed in cancer cells and thus exhibits little to no toxicity towards normal cells.7,54
The 4-arylisoflavan triphendiol 15 is a second generation isoflavonoid drug currently under investigation as a treatment for pancreatic and bile duct cancers. Like phenoxodiol 14, triphendiol inhibits tumour proliferation, arrests the cell cycle and induces apoptosis via caspase-dependent and caspase-independent pathways.54,69 Additionally, triphendiol acts synergistically with gemcitabine, the current standard of care for pancreatic cancer. Triphendiol therefore has considerable potential as a chemosensitiser for the treatment of refractory pancreaticobiliary tumours.
Recurrent and chemoresistant tumours present significant challenges in the treatment of many cancers. These phenomena are thought to be linked to cancer stem cells, which are long-lived, self-renewing cells with the capacity to differentiate into a number of
‐ 5 ‐ tumour cell types.70-72 Most chemotherapy drugs target the rapidly proliferating cells that make up the bulk of a tumour, leaving the more slowly dividing cancer stem cells unaffected. The surviving stem cells are then able to give rise to new tumours which are often more aggressive and resistant to treatment. Cancer stem cells are resistant to conventional chemotherapy, which typically activates the caspase-dependent apoptotic cascade. However, the mammalian target of rapamycin (mTOR) survival pathway plays an important role in stem cell biology and thus presents an alternative therapeutic target.73 Two isoflavonoid compounds, the 8-methyl-4-aryl isoflavan 16 and the isoflavone carbamate 17, inhibit mTOR and are thus able to induce death in ovarian cancer stem cells.71,72,74 The isoflavan 16 has also been shown to disrupt mitochondrial membrane potential, indicating a second mechanism for inducing cancer stem cell death.72 Isoflavone analogues 16 and 17 represent a promising new strategy for the treatment of recurrent and chemoresistant cancers.
1.1.3 Anti-Inflammatory Activity of Isoflavone Analogues Inflammation is both an essential physiological process and a characteristic of a number of disease states including arthritis, asthma and cardiovascular disease.75-79 Isoflavone analogues, both natural and synthetic, have been shown to exert anti-inflammatory activity in a variety of both in vitro and in vivo models. Irradiation by UV light induces an inflammatory response in mammalian skin cells. Genistein, equol and phenoxodiol protect skin cells from the damaging effects of UV-irradiation in vitro and in animals.80,81 Topical application of equol and the isoflavene NV-38 18 prevented UVB- induced skin damage in a mouse model.82 The anti-inflammatory activity of genistein has also been reported in animal models of arthritis83 and asthma.84 The anti- inflammatory properties of isoflavonoid compounds can also benefit the cardiovascular system in a number of ways. Genistein has been shown to prevent atherosclerosis in vitro by inhibiting monocyte adhesion to the endothelium.85 Furthermore, intravenous administration of genistein induced vasodilation in human subjects.15 Wu and co- workers86 reported a series of 2-substituted isoflavones that exhibited antihypertensive activity in rats. The most active analogue was the 2-phenyl isoflavone 19. This compound features the 2,3-diarylbenzopyran motif which is shared by several of the biologically active compounds discussed in Section 1.1.1.
‐ 6 ‐
Inflammation is a complex phenomenon involving multiple biochemical pathways. Isoflavonoid compounds have been reported to inhibit the production of a variety of inflammatory signalling molecules, such as interleukin (IL)-6, tumour necrosis factor (TNF)-α,16,82,83 and nitric oxide.15,16,87,88 Interactions between isoflavonoid compounds and peroxisome proliferator-activated receptor (PPAR)-γ are also thought to contribute to anti-inflammatory activity.85 In addition to these modes of action, isoflavonoid compounds can prevent tissue damage via their antioxidant capability.13,89-92 The polyphenolic character of many isoflavones facilitates both free radical scavenging91 and the chelation of transition metals.92
1.1.4 Other Biological Activities of Isoflavone Analogues Isoflavonoid compounds are known to exhibit a number of biological activities in addition to those discussed above. Genistein has demonstrated some potential for the treatment of cystic fibrosis and mucopolysaccharidosis due to its ability to reactivate defective proteins.93 Genistein, daidzein and biochanin A have been shown to influence lipid metabolism in ways that have positive implications for cardiovascular health14,94,95 and the treatment of diabetes.24,96,97 Additionally, Zhang and coworkers98 reported that puerarin, an 8-C-glycoside of daidzein, reverses insulin resistance in obese rats, indicating a potential anti-diabetic application for this compound. Other glycosides of daidzein and genistein have been reported to exhibit anti-allergic99 and antiviral100 activity. The isoflavanone violanone 20 has exhibited antifungal activity in vitro.61 Another natural product, dalparvone 21, is active against malaria and tuberculosis.60 A series of 2-substituted isoflavones 22 synthesised by Stachulski et al.101 exhibited anti- parasitic activity against Cryptosporidium parvum both in vitro and in vivo.
‐ 7 ‐
Novel isoflavonoid compounds continue to be isolated from natural sources and the development of methodology towards natural and synthetic analogues is an active area of research. It is anticipated that further exploration of isoflavone chemistry will lead to the discovery of new bioactive compounds. As many biologically active isoflavonoid compounds bear substituents at C2 and/or C4, the preparation of 2- and 4-substituted isoflavone analogues is of particular interest.
1.2 Synthesis of Isoflavonoid Compounds 1.2.1 Synthesis of Isoflavones The synthetic methodology for isoflavones is well-established. A typical synthesis of daidzein 1 begins with the condensation of resorcinol 23 and 4-hydroxyphenylacetic acid 24 via a Friedel-Crafts acylation reaction, which is followed by cyclisation of the deoxybenzoin intermediate 25 (Scheme 1-1). Isoflavones with different substitution patterns on rings A and B can be accessed by using appropriately substituted phenols and phenylacetic acids. The condensation step may be performed by heating the starting 37,102-108 materials in neat BF3·Et2O or by melting the solids together with one equivalent 109 of anhydrous ZnCl2. Deoxybenzoins have also been prepared via acylation reactions 110-112 of phenols with phenylacetyl chlorides using AlCl3 as the Lewis acid catalyst. Additionally, phenylacetonitriles have also been used in place of phenylacetic 101,104,113-117 acids. Cyclisation of the deoxybenzoin is typically achieved using BF3·Et2O and methanesulfonyl chloride in N,N-dimethylformamide.103,108,109,116,118-124 Alternative cyclisation reagents include dimethylformamide dimethylacetal,125,107,126,104 N,N- carbonyldiimidazole with formic acid,127 dimethoxydimethylaminomethane128 and ethyl orthoformate with morpholine,112,129 pyridine and piperidine115,130,131 or sodium. The condensation and cyclisation reactions may be performed as a “one-pot” procedure, as per the example of Wähälä and coworkers.103
‐ 8 ‐ HO OH HO OH HO i
+ O OH O OH 23 24 25
ii
8 HO O 2 A C 2' 6 3 3' 5 4 B O 6' OH 5' 1
Scheme 1-1: Reagents and conditions: i) BF3·Et2O, 100 °C; ii) BF3·Et2O, MeSO2Cl, N,N-DMF.
The cyclisation of deoxybenzoins is by no means the only synthetic route to the isoflavone scaffold. Several groups have reported the synthesis of isoflavones from chalcones.132-134 The synthesis of glycitein 26 by Nógrádi and Szöll ősy133 is a typical example of this methodology (Scheme 1-2). The chalcone 27 underwent oxidative rearrangement in the presence of thallium(III) nitrate to give the acetal intermediate 28. Subsequent deprotection and acid-catalysed cyclisation afforded the isoflavone product 26.
‐ 9 ‐
Scheme 1-2: Reagents and conditions: i) Tl(NO3)3·3H2O, trimethyl orthoformate,
methanol, rt, 1 h; ii) H2, Pd/C, methanol/acetone (1:1); iii) conc. HCl, methanol, 15 min, reflux.
Deesamer and coworkers61 reported the synthesis of 3′,7-dihydroxy-2′,4′- dimethoxyisoflavone 29 via the chromanone intermediate 30 (Scheme 1-3). The chromanone was prepared via the acylation of resorcinol 23 with 3-chloropropionyl chloride, followed by cyclisation under basic conditions. After protection of the phenol as a benzyl ether, the O-benzyl chromanone was brominated at C3 to give compound 31. Treatment with sodium hydride and thiophenol afforded the 3-phenylthio species 32. The aryllead triacetate 33 was introduced via a coupling reaction to give the intermediate 34. Cleavage of the phenylthio group under mild oxidative conditions, followed by hydrolysis of the benzyloxy protecting groups generated the isoflavone 29.
‐ 10 ‐
Scheme 1-3: Reagents and conditions: i) 3-chloropropionyl chloride, AlCl3, Et2O, 0 °C,
1 h; ii) aq. NaOH, rt, 2 h; iii) BnBr, K2CO3, acetone, reflux, overnight; iv) CuBr2,
EtOAc-CHCl3, reflux, overnight; v) PhSH, NaH, THF, 0 °C, 1 h; vi) pyridine, CHCl3, 55 °C, overnight; vii) MCPBA, EtOAc, 0 °C, then toluene, reflux; viii) 47% aq. HBr, 50 °C, overnight.
Li and coworkers135 reported a novel approach for the synthesis of daidzein 1 and formononetin 3 (Scheme 1-4). In a one-pot procedure, 4-benzyloxysalicylic aldehyde 35 was subjected to a Wittig reaction, O-alkylation and then a second Wittig reaction to generate the diene 36. The isoflavene 37 was formed via ring-closing metathesis using Grubbs (II) catalyst. Oxidation of the isoflavene 37 gave the isoflavanol 38, which underwent further oxidation to give the protected isoflavone 39. Selective removal of the benzyloxy group generated formononetin 3, while cleavage of both protecting groups gave daidzein 1.
‐ 11 ‐
Scheme 1-4: Reagents and conditions: i) a) MTPPB, t-BuOK, THF, 0 °C 2 h; b) 2- bromo-4′-methoxyacetophenone, reflux, 1 h; c) MTPPB, t-BuOK, THF, 0 °C, 1 h; ii) Grubbs (II), CH2Cl2, 40 °C, 8 h; iii) BH3–SMe2, THF, 0 °C, 4 h, then H2O, 10% NaOH, 37% H2O2, 30 min; iv) DDQ, 1,4-dioxane, reflux, 8 h; v) AlCl3, EtSH, CH2Cl2, 0 °C, 30 min.; vi) Pd(OH)2, EtOH, cyclohexene, reflux, 1 h.
1.2.2 Synthesis of Isoflavanols and Isoflavanones A variety of isoflavonoid scaffolds can be prepared via modification of the isoflavone C ring. Reduction of both the carbonyl group and the C2-C3 double bond via catalytic 136-138 hydrogenation or with a reducing agent such as NaBH4 affords isoflavanol 40 (Scheme 1-5). The isoflavanol is typically obtained as a mixture of diastereomers, with cis or trans relative stereochemistry about the C3-C4 bond. The precise ratio of these products depends on a number of factors, including the type and relative quantity of reducing agent or hydrogenation catalyst used.136,137 Selective reduction of the isoflavone C2-C3 double bond gives the corresponding isoflavanone 41. This has been accomplished with reducing agents such as diisobutylaluminium hydride137,139 and via catalytic hydrogenation under basic conditions136,139. Alternatively, isoflavanones may be prepared directly from deoxybenzoins via cyclisation with formaldehyde,106 or via the reduction of 3-phenylthiochromanones 34.61
‐ 12 ‐ HO O
O OH 1 i ii
HO O HO O
OH O OH OH 41 40
Scheme 1-5: Reagents and conditions: i) H2, Pd/C, EtOH; ii) H2, Pd/Al2O3, aq. KOH, EtOH.
1.2.3 Synthesis of Isoflavenes and Isoflavans Isoflav-3-enes such as phenoxodiol 14 can be synthesised via the acid-catalysed dehydration of the corresponding isoflavanol 40106,136,138 (Scheme 1-6). The C3-C4 double bond of the isoflavene is readily reduced to generate isoflavans such as equol 5.136,140 Isoflavans can also be obtained directly from isoflavones via hydrogenation.61,139,137
+ Scheme 1-6: Reagents and conditions: i) H2, Pd/C, EtOH; ii) H , reflux.
‐ 13 ‐ Isoflavenes have also been synthesised via other routes, such as the ring-closing metathesis approach outlined in Scheme 1-4135. Employing an alternative strategy, Burali and coworkers140 treated 1-aryl-2-(o-hydroxymethyl)phenoxyethanones 41 with triphenylphosphine hydrobromide to generate triphenylphosphonium bromide salts 42 (Scheme 1-7). Cyclisation with sodium ethoxide afforded isoflavenes 43.
Scheme 1-7: Reagents and conditions: i) PPh3·HBr, acetonitrile, reflux, 3 h; ii) EtONa, EtOH, rt, 12 h.
1.2.4 Synthesis of 2-Substituted Isoflavonoid Compounds The preparation of 2-substituted isoflavones 44 from deoxybenzoins 25 is well documented in the literature. The cyclisation may be performed with a symmetrical anhydride105,141-146 or acyl chloride117,147-151 in the presence of base (Scheme 1-8). Reactions of this type have also been carried out in the presence of a phase transfer catalyst.101,102,152-154 Protected deoxybenzoins 45 may also undergo Knovenagel condensation with benzaldehydes 46 to generate 2-arylisoflavanones 47.36,48-50,102,153-155
‐ 14 ‐ HO OH HO O R i, ii
O O OH OH 25 44
iii
R THPO OH THPO O R iv + H O O O OTHP OTHP 45 46 47
Scheme 1-8: Reagents and conditions: i) (RCO)2O, NaO2CR, reflux; ii) aq. KOH, reflux; iii) 3,4-dihydro-2H-pyran, TsOH, dichloromethane, 0 ° to rt; iv) piperidine, benzene, reflux.
2-Substituted isoflavenes have been prepared via a number of synthetic routes. Varma and Dahiya156 prepared a series of 2-N-heterocyclic isoflavanols 48 via the microwave- assisted condensation of salicylaldehydes 49 with enamines 50 (Scheme 1-9). The isoflavanols 48 were dehydrated in situ to generate 2-substituted isoflavenes 51.
Scheme 1-9: Reagents and conditions: NH4OAc, microwave.
‐ 15 ‐ In the aforementioned syntheses, the C2 substituent was incorporated into the isoflavonoid structure during the formation of Ring C. An alternative approach is to introduce the C2 substituent to a pre-formed 3-arylbenzopyrene scaffold. Grese and Pennington,157 and others,158-160 have synthesised 2-alkyl- and 2-arylisoflavenes 52 from coumarins 53 via Grignard chemistry on phenylacetal intermediate 54 (Scheme 1-10). Alternatively, Liepa161,162 and Faragalla et al.163,164 have treated isoflavylium salts 55, which are reactive cationic species that can be generated from isoflavenes, with a variety of nucleophiles to obtain 2-substituted isoflavenes 52.
TBSO O O TBSO O OPh
i, ii
53 OTBS 54 OTBS
iii, iv
+ - AcO O PF6 HO O R v, vi
55 OAc 52 OH
Scheme 1-10: Reagents and conditions: i) DIBAL-H, toluene, –78 °C; ii) phenol, chlorobenzene, reflux; iii) RMgBr, toluene, 0 °C to rt; iv) TBAF, THF; v) R-TMS, dichloromethane, rt; vi) imidazole, EtOH, reflux.
1.2.5 Synthesis of 4-Substituted Isoflavans 4-Substituted isoflavans such as triphendiol 15 have been synthesised by treating an appropriately protected isoflavanone 56 with a Grignard reagent38,138,165 (Scheme 1-11). Dehydration, reduction and deprotection of the Grignard adduct 57 affords the desired isoflavan.
‐ 16 ‐
Scheme 1-11: Reagents and conditions: i) H2, Pd/Al2O3, KOH(aq), EtOH; ii) TDMSCl,
imidazole, N,N-DMF; iii) p-MeOPhMgBr, THF; iv) P2O5, DCM; v) H2, Pd/C, EtOAc; vi) TBAF, AcOH, N,N-DMF.
In another approach, Bury and coworkers47 condensed 2,4′-dihydroxy-4- methoxybenzophenone 58 with phenylacetic acids 59 to generate the 4-substituted coumarin intermediates 60 (Scheme 1-12). These were reduced with lithium aluminium hydride and then treated with acid to generate the 4-substituted isoflavenes 61. Catalytic hydrogenation afforded isoflavans 62.
‐ 17 ‐
Scheme 1-12: Reagents and conditions: i) Ac2O, Et3N, 110 °C; ii) LiAlH4, THF; iii)
HCl, 65 °C; iv) H2, Pd/C, EtOH.
Additional strategies have been reported for the synthesis of 4-substituted isoflavenes, which are readily converted to 4-substituted isoflavans via reduction. Alberola and coworkers166 reported the synthesis of 2,4-disubstitued isoflavenes 63 from formononetin 3 (Scheme 1-13). The isoflavone was silylated and then treated with organometallic reagents to generate the ring-opened intermediates 64. Acid-catalysed cyclisation and deprotection afforded the isoflavenes 63.
Scheme 1-13: Reagents and conditions: i) hexamethyldisilazane, pyridine, 80 °C, 2 h; ii)
R3Al, benzene, rt, 24 h; iii) HCl, H2O.
4-Substituted isoflavenes have also been prepared from non-isoflavonoid precursors. Bernard and coworkers167 treated the cyclobutanone 65 with para-toluenesulfonic acid
‐ 18 ‐ to induce an intramolecular alkylation, followed by in situ ring opening of the intermediate 66 to generate the 4-substituted isoflavene 67 (Scheme 1-14).
Scheme 1-14: Reagents and conditions: p-toluenesulfonic acid, benzene, reflux, 30 min.
When 4-substituted isoflavans are prepared from 4-substituted isoflavenes, the relative stereochemistry of the product depends on the chosen method of reduction. In the examples described in Schemes 1-11 and 1-12, this step was performed by catalytic hydrogenation. Since these reactions take place at the catalyst surface, the two hydrogen atoms will always be added to the same face of the isoflavene. Thus, 4-substituted isoflavans prepared in this manner always exhibit cis-stereochemistry around the C3-C4 bond. 4-Substituted isoflavans with trans stereochemistry can be accessed via an alternative synthetic strategy. Treatment of an acetylated isoflavanol 68 with a catalytic amount of BF3·Et2O generates a reactive cationic species 69 (Scheme 1-15). Nucleophilic attack at C4 results in a trans 4-substituted isoflavan 70.168
Scheme 1-15: Reagents and conditions: BF3·Et2O, ArH, dichloromethane, rt.
‐ 19 ‐ 1.3 Synthetic Targets The primary aim of this project was to generate biologically active isoflavone analogues with potential therapeutic applications. To this end, the selection of synthetic targets was informed by an analysis of structure-activity relationships of isoflavonoid compounds with known biological activity. As discussed in Section 1.1, many bioactive isoflavone analogues fall in one of two categories: 2-aryl compounds, including SERMS such as acolbifene 7, and 4-aryl compounds, such the anti-cancer drug candidates triphendiol 15 and NV-128 16. It is predicted that novel isoflavone analogues that mimic key structural features of these compounds are likely to exhibit similar biological properties.
R O HO O N HO O
OH
OH OMe 7 15 R=H 16 R=Me
R
R HO O HO O X
OH OH 72 71
With this in mind, two types of structures were selected as synthetic targets. 2-Aryl benzopyrenes 71 feature the 2,3-diarylbenzopyran structure common to acolbifene 7 and other bioactive molecules. The second type of target structure 72 was designed to mimic 4-substituted isoflavans such as triphendiol 15. As illustrated in Figure 1-1, the superimposition of 2-benzylisoflavene 73 onto triphendiol 15 reveals significant overlap between the phenol groups and aromatic rings of the two structures. In addition to the targeted 2-substituted structures 71 and 72, alternative synthetic routes to 4-substituted isoflavans will also be explored.
‐ 20 ‐
Figure 1-1: Three-dimensional overlay of 2-benzylisoflavene 73 with triphendiol 15.
1.4 Thesis Aims The general aims of the present work were to generate a series of novel isoflavone analogues and to investigate various methodologies for their synthesis. The synthesis of 2-substituted and 4-susbtituted isoflavonoid compounds forms the basis of this thesis.
1.4.1 2-Substituted Isoflavenes via Isoflavylium Chemistry Isoflavenes such as phenoxodiol 14 are readily converted to isoflavylium salts 55 using reagents such as tritylium hexafluorophosphate163,164 (Scheme 1-16). Isoflavylium ions react with nucleophiles to generate 2-substituted isoflav-3-enes 52.161-164,169 This synthetic strategy can be used to introduce a diverse range of substituents at C2. The preparation of isoflavylium salts is explored in Chapter Two of this thesis. Chapter
‐ 21 ‐ Three details the reactions of these salts with nucleophiles to generate a variety of novel 2-substituted isoflavenes.
Scheme 1-16: Reagents and conditions: i) Ac2O, K2CO3, acetone, reflux; ii) tritylium hexafluorophosphate, dichloromethane, rt; iii) nucleophile, dichloromethane, rt.
1.4.2 2-Substituted Isoflavenes from 2-Substituted Isoflavones Isoflavenes are readily synthesised from isoflavones.139,136 It follows, therefore, that 2- substituted isoflavenes 52 could also be prepared in a similar fashion from 2-substituted isoflavones 44 (Scheme 1-17). Isoflavones with a variety of C2 substituents can be prepared via the cyclisation reaction of deoxybenzoin 25.36,48,50,101,102,105,117,141-155 Subsequent reduction and dehydration afford the corresponding isoflavenes 52. 2- Substituted isoflavones also provide a starting point for the synthesis of 2,4- disubstituted compounds 74 using Grignard chemistry. The preparation of 2-substituted isoflavones and their derivatives forms the basis of Chapter Four.
Scheme 1-17
‐ 22 ‐ 1.4.3 Synthesis of Isoflavene Epoxides Compounds such as the epoxide 75 are attractive synthetic targets because they provide a potential alternative route to a variety of 4-substituted isoflavans via ring-opening reactions. While the epoxides of various isoflavones have been reported in the literature,141,170-172 the epoxidation of isoflav-3-enes has not yet been documented. Chapter Five explores the synthesis of isoflavene epoxides as potential precursors to 4- substituted isoflavonoid compounds.
‐ 23 ‐ CHAPTER TWO
SYNTHESIS OF ISOFLAVYLIUM SALTS
2.1 Background 2-Substituted isoflavenes have been identified as synthetic targets with potential anti- cancer activity, as discussed in Section 1.3. A number of synthetic methods for 2- substitued isoflavonoid compounds have been reported, utilising key intermediates such as deoxybenzoins,36,48,50,101,102,105,117,141-155 coumarins157-160 and enamines.156 An alternative approach is to introduce the C2 substituent to the isoflavonoid scaffold via nucleophilic addition to an isoflavylium cation 76.161-164 The reactivity of isoflavylium ions and their parent benzopyrylium ions 77 is well known in the literature and has been exploited to generate a variety of heterocyclic scaffolds.
Jurd173 demonstrated that flavylium salts undergo rearrangement in the presence of acid and hydrogen peroxide to form benzofurans. Durani and Kapil174 used a similar approach to generate 2-aryl-3-aroylbenzofurans from a 2-aryl isoflavylium salt. Deschamps-Vallet et al.175 also synthesised benzofurans 78 in such a manner from isoflavylium salts 77 that lacked a 2-substitutent (Scheme 2-1). The authors’ proposed mechanism for the ring contraction begins with the nucleophilic addition of isopropanol at C2 to form acetal 79. Reaction with hydrogen peroxide generates the epoxide intermediate 80, which is ring-opened and undergoes an acid-catalysed rearrangement to give the cationic species 81. Elimination of water and formic acid generates the diol 82 which cyclises to form the benzofuran 78. It was observed that isoflavylium salts 76 exposed to acid and isopropanol in the absence of hydrogen peroxide formed ether- linked dimers 83, highlighting the reactivity of the C2 position.
‐ 24 ‐ + - O O O O ClO4 ii i O O
79 76
iii 83
O O OH OH OH iv -HCOOH -H2O O OH OH -H2O O OH 80 81 82 78
+ Scheme 2-1: Reagents and conditions: i) HCl, iPrOH; ii) iPrOH; iii) H2O2; iv) H ,
H2O.
Deschamps-Vallet et al.176 further exploited the reactivity of the C2 position by oxidising isoflavylium salts 84 to coumarins 85 using CrO3 and pyridine (Scheme 2-2). In the same paper, the authors reported the reduction of isoflavylium salts with potassium borohydride to give isoflavenes 86.
Scheme 2-2: Reagents and conditions: i) CrO3, pyridine; ii) KBH4, THF.
An examination of the isoflavylium ion’s contributing resonance structures indicates that the hydride ion can add to C2 or to C4, giving the isoflav-3-ene or -2-ene, respectively. Deschamps-Vallet et al. reported that the product was almost exclusively the isoflav-3-ene, indicating that C2 is the more reactive position.
‐ 25 ‐
Interestingly, when Liepa161 treated 5,7-dihydroxyisoflavylium chloride with sodium cyanoborohydride, an almost equimolar mixture of the isoflav-3-ene and the isoflav-2- ene was produced. In contrast, the reduction of the 4′,5,7-trihydroxy analogue predominantly yielded the isoflav-3-ene. Desbene and Cherton177 investigated the addition of hydride and azide ions to a variety of benzopyrylium salts. They too observed nucleophilic addition at both C2 and C4 and determined that the regiochemistry of the reaction was influenced by the substituents on the cation. In general, benzopyrylium ions with substituents at C3 and/or C4 underwent nucleophilic addition at C2, while those species with an aryl-substituted C2 and no other substituents on the pyrylium ring tended to react at C4. Doodeman et al.178 found that benzopyrylium ions with unsubstituted pyrylium rings underwent nucleophilic addition exclusively at C2.
In the case of isoflavylium ions, Liepa,161,162 Faragalla163,164 and others169,179,180 have demonstrated that nucleophiles, with the exception of hydride ions, add selectively to C2. This is not unexpected, as Faragalla et al.164 have indicated that 2-substituted isoflav-3-ene products are thermodynamically favoured due to their more highly conjugated C3-C4 double bond compared to the C2-C3 double bond in the 4-substituted product. The regioselectivity of nucleophilic addition reaction means that isoflavylium salts are viable precursors for the synthesis of 2-substituted isoflavenes.
2.1.1 Synthesis of Isoflavylium Salts Isoflavylium salts can be accessed via a number of methods. Broadly speaking, these various approaches can be classified into three categories: synthesis via acid-catalysed condensation; synthesis from 2-substituted isoflavenes; and synthesis via hydride
‐ 26 ‐ abstraction. The preparation of an isoflavylium perchlorate salt by Bouvier et al.181 is an example of the first type of strategy, wherein salicylaldehyde 87 was reacted with 2- phenylethyl acetal 88 in the presence of perchloric acid (Scheme 2-3). Loss of ethanol from the acetal results in the formation of an enol ether 89, which undergoes an addition reaction with the protonated salicylaldehyde 90 to form the benzopyran intermediate 91. Elimination of water and ethanol gives the isoflavylium salt 92.
+ - OH EtO OEt O ClO4 + CHO
87 88 92
-H O -EtOH 2 -EtOH
H H O OEt O+ OEt
H O+ OH H 90 89 91
Scheme 2-3: Reagents and conditions: HClO4, AcOH, –5 °C.
Liepa161 also adopted an acid-catalysed condensation approach utilising polyhydric phenols 93 and arylmalondialdehydes 94 (Scheme 2-4). Hydrochloric acid, phosphoryl chloride or perchloric acid were used as catalysts. While this method proved useful for the preparation of 5-hydroxy- and 5-methoxy-substituted isoflavylium salts 95, equivalent reactions with resorcinol were unsuccessful.
‐ 27 ‐ OH RO OH OHC RO O+
+ R
OR OR R R R 95 93 94
Scheme 2-4: Reagents and conditions: HCl, AcOH, rt or 45 °C; HClO4, AcOH, 40 °C;
or POCl3, ACN, 30 °C.
In order to access isoflavylium salts without a substituent at C5, Liepa162 proceeded via an alternative route involving the acid-catalysed dehydration of 2-hydroxyisoflav-3-enes 98 (Scheme 2-5). The 2-hydroxyisoflavenes were synthesised via the condensation of appropriately substituted glycidates 96 and salicylaldehydes 97. Protonation of the hydroxyl moiety followed by elimination of water gave isoflavylium salts 99.
Scheme 2-5: Reagents and conditions: i) various solvents, reflux; ii) HClO4, AcOH.
Doodeman et al.178 adopted an analogous strategy to generate benzopyrylium ions from acetal precursors. Vinyl-substituted phenols 100 were reacted with benzyloxy-1,2- propadiene 101 to give allylic acetals 102 which were then converted via ring closing metathesis to 2-benzyloxychromenes 103 (Scheme 2-6). The chromene acetals were
‐ 28 ‐ then treated with BF3·Et2O to give benzopyrylium ions 104 which were subsequently trapped via reaction with nucleophiles.
Scheme 2-6: Reagents and conditions: i) 5 mol % Pd(OAc)2, dppp, Et3N, ACN, rt; ii)
Grubbs’ catalyst, DCM, rt; iii) BF3·Et2O, DCM, 0 °C.
Like their acetal counterparts, isoflavene aminals can also serve as precursors to isoflavylium salts. Dean and Varma182 prepared 2-N-morpholinyl isoflavene 105 via the condensation of salicylaldehyde 87 and N-styrylmorpholine 106 (Scheme 2-7). Treatment of isoflavene 105 with trityl perchlorate cleaved the morpholine leaving group to generate the isoflavylium salt 107. Interestingly, the same transformation could not be achieved under the conditions used by Liepa162 to generate isoflavylium salts from 2-hydroxyisoflavenes. Instead, treatment of the 2-morpholinylisoflavene 105 with perchloric or other acids resulted in the formation of a symmetrical C2 ether-linked dimer 108. Presumably, the dimerisation observed by Dean and Varma proceeded via an isoflavylium intermediate, with water subsequently providing an additional oxygen atom to form the ether bridge. The resulting bisacetal 108 was readily converted to the isoflavylium salt 107 using trityl perchlorate. A similar dimerisation was observed by Deschamps-Vallet et al.175 when isoflavylium salts were treated with acid.
‐ 29 ‐
+ – Scheme 2-7: Reagents and conditions: i) Benzene, reflux; ii) Ph3C ClO4 , AcOH, 110– 130 °C; iii) H+.
Besides being able to liberate a good leaving group such morpholine, trityl reagents have also been used to abstract hydride from various pyrene species, resulting in the formation of pyrylium,183 benzopyrylium184 and isoflavylium salts.163,164,179 Anirudhan and coworkers179 treated isoflavenes with trityl perchlorate in acetic acid at reflux to generate the corresponding isoflavylium salts. More recently, Faragalla et al.163,164 used trityl hexafluorophosphate to effect a similar transformation at room temperature (Scheme 2-8). Diacetoxyphenoxodiol 109 was dissolved in dichloromethane and treated with the trityl compound to give the isoflavylium salt 110, which was then subjected to nucleophilic addition without being isolated from the reaction mixture.
+ – Scheme 2-8: Reagents and conditions: Ph3C PF6 , DCM, rt.
‐ 30 ‐ 2.2 Preparation of Isoflavylium Salts using Tritylium Hexafluorophosphate As the isoflavene phenoxodiol 14 was readily available from Novogen, it was decided that the hydride abstraction strategy employed by Faragalla et al.163,164 would be an appropriate starting point for the synthesis of 2-substituted isoflavenes via isoflavylium salts. In the literature example, phenoxodiol 14 was protected as the acetate diester 109 in order to eliminate the potential for nucleophilic addition reactions between the isoflavylium salt and free phenols, which could lead to the formation of dimers. Acetylation also deactivates Rings A and B towards electrophilic attack by the isoflavylium salt. Apart from the prevention of side reactions, there is an additional advantage to acetylating the starting material prior to salt formation. It has been observed in the present work that isoflavonoid acetates are more readily recrystallised compared to their phenolic counterparts. The use of an acetylated isoflavylium salt would therefore facilitate the purification of 2-substituted isoflavenes prepared by this method. The acetylation reaction itself is straightforward and involves the treatment of phenoxodiol 14 with excess acetic anhydride and two equivalents of potassium carbonate in acetone at reflux (Scheme 2-9). The acetylated isoflavene 109 was obtained as an off-white powder in 99% yield. The appearance of two 3H singlets at 2.31 and 2.29 ppm in the 1H NMR spectrum confirmed that the acetylation was successful.
Scheme 2-9: Reagents and conditions: Ac2O, K2CO3, acetone, reflux, 1 h.
The acetate-protected isoflavene 109 was treated with tritylium hexafluorophosphate in dichloromethane to generate the isoflavylium salt 55 (Scheme 2-10), which formed as a bright yellow precipitate. In the synthesis of 2-substituted isoflavenes as performed by Faragalla et al.,163,164 the nucleophile was added directly to the reaction mixture at this stage without isolation of the salt. In the present work, it was observed that such an approach gave rise to products contaminated with triphenylmethane 110, a side product
‐ 31 ‐ derived from the tritylium ion 111. This impurity proved difficult to remove by recrystallisation or chromatographic methods. Fortunately, this problem was easily circumvented. The isoflavylium salt 55 was insoluble in DCM and thus precipitated from the reaction mixture, while triphenylmethane 110 remained in solution. The isoflavylium salt could therefore be isolated from impurities simply by filtering the reaction mixture. Isoflavylium salt 55 was thus obtained in greater than 90% yield. Isolation of the salt in this manner also provided the opportunity for more complete characterisation.
Scheme 2-10: Reagents and conditions: DCM, rt, 1 h.
The 1H NMR spectrum of isoflavylium salt 55 in d-TFA was similar to that of the parent isoflavene 109, but with the aromatic protons shifted upfield. The largest upfield shift was observed for the signals associated with H2 and H4. In the isoflavene 109, the two protons at C2 gave rise to a signal at δ 5.15 which appeared as a fine doublet (J = 1.4 Hz) due to allylic coupling with H4. The H4 proton appeared as a broad singlet at δ 6.76. In the isoflavylium salt 55, H2 and H4 appeared as doublets (J = 2.0 Hz) at δ 9.93 and 9.85. The significant downfield shift observed for H2 and H4 relative to isoflavene 109 is consistent with the spectra of isoflavylium and benzopyrylium salts described in the literature.161,162,174,178,180-182 In those studies, chemical shift values for H2 and H4 were typically reported in the range of 8.5 to 10.0 ppm. As the chemical shifts of H2 and H4 were very close together in the spectrum of salt 55, it was difficult to assign these signals with certainty. HSQC indicated the protons at δ 9.93 and 9.85 correlated with 13C signals at δ 168.8 (C2) and 159.1 (C4), respectively. These 13C NMR signals have been assigned on the basis that C2 is expected to experience a greater degree of deshielding that C4, due to its proximity to the oxygen atom. Thus, it can be concluded
‐ 32 ‐ that H2 appeared at δ 9.93 while H4 appeared at δ 9.85. This is consistent with 1H NMR spectra of isoflavylium and benzopyrylium salts that have been reported in the literature, where the doublet further downfield was designated H2.162,180
Much of the present work has been focussed on the preparation of derivatives of phenoxodiol 14, due the availability of that starting material. However, it should be noted that trityl hexafluorophosphate can be used to prepare isoflavylium salts from isoflavenes with a variety of substitution patterns (Scheme 2-11). Isoflavenes 111 and 112 behaved similarly to diacetoxyphenoxodiol 109 and their corresponding salts 113 and 114 were isolated as bright yellow solids in 82% and 74% yields, respectively. Curiously, when the 7,3′-diacetoxy analogue 115 was treated with trityl hexafluorophosphate, the expected product 116 did not precipitate from dichloromethane and thus could not be isolated cleanly.
R1 R1 - AcO O AcO O+ PF6
R3 R3
R2 R2 R4 R4
111: R1 =Me,R2 =H,R3 =H,R4 =OAc 113: R1 =Me,R2 =H,R3 =H,R4 =OAc 112: R1 =H,R2 =Me,R3 =H,R4 =OAc 114: R1 =H,R2 =Me,R3 =H,R4 =OAc 1 2 3 4 1 2 3 4 115: R =H,R =H,R =OAc,R =H 116: R =H,R =H,R =OAc,R =H
+ – Scheme 2-11: Reagents and conditions: Ph3C PF6 , DCM, rt.
Contrary to the predictions of Faragalla et al.,163,164 hydride abstraction can also be performed on an unprotected phenolic substrate. Phenoxodiol 14 was treated with trityl hexafluorophosphate to generate the isoflavylium salt 117 as a dark red solid in 69% yield (Scheme 2-12). As with the acetylated salts, the product was isolated by filtration. The insolubility of the phenolic isoflavylium salt in the reaction medium may explain why the predicted dimerisation reactions were not observed. The formation of the salt 117 was confirmed by 1H NMR spectroscopy (Figure 2-1). H2 and H4 appeared as doublets (J = 2.1 Hz) at δ 9.44 and 9.46, respectively. These signals were assigned on the basis of HSQC correlations, as described for isoflavylium salt 55, above.
‐ 33 ‐
+ - HO O HO O PF6
OH OH 14 117
+ – Scheme 2-12: Reagents and conditions: Ph3C PF6 , DCM, rt.
Figure 2-1: 1H NMR spectrum of isoflavylium salt 117 in d-TFA
2.3 Preparation of Isoflavylium Salts via 2-Hydroxyisoflavenes As established in Section 2.1.1, hydride abstraction is not the only synthetic route to isoflavylium salts. Neither is it the only approach for which phenoxodiol 14 can serve as a starting material. Previous work in the Kumar group168 indicated that phenoxodiol 14 can be hydroxylated at the 2-position via reaction with thallic trifluoroacetate and trifluoroacetic acid (Scheme 2-13). As Liepa162 demonstrated, 2-hydroxyisoflavenes can be converted to isoflavylium salts via acidification. These two reactions were combined in the present work. Treatment of phenoxodiol 14 with thallic trifluoroacetate and trifluoroacetic acid yielded a solution of the 2-hydroxy intermediate 118 in ethyl acetate after extraction. Concentrated hydrochloric acid was added to the solution and the
‐ 34 ‐ resulting mixture was subsequently filtered to give the isoflavylium chloride salt 119 as a dark red-purple solid in 65% yield. As expected, the 1H and 13C NMR spectra of 119 were identical to those recorded for the hexafluorophosphate salt 117, above.
Scheme 2-13: Reagents and conditions: i) Tl(O2CCF3)3, TFA, rt, 30 min; ii) conc. HCl, EtOAc, rt, 10 min.
The method described above has also been used to synthesise the isoflavylium chloride salt of the 4-arylisoflavene 120, which was obtained from Novogen as the di-tert- butyldimethylsilyl ether (Scheme 2-14). The isoflavylium chloride salt 121 was obtained as dark red solid in 50% yield. Previous attempts had been made to generate an isoflavylium ion from 120 and tritylium hexafluorophosphate via the hydride abstraction method described in Section 2.2. In that reaction, however, the salt could not be isolated as it did not precipitate out from dichloromethane. Interestingly, the TBDMS groups were cleaved during the synthesis of 121, as indicated by the absence of signals at < 2 ppm in the 1H NMR spectrum. This deprotection is thought to have occurred in the first stage of the process, where the trifluoroacetic acid or the trifluoroacetate salt may have served as sources of fluoride, to generate the phenolic intermediate 122. As in the case of isoflavylium salts 117 and 119, subsequent precipitation of the nascent salt out of solution thus decreases the likelihood of interactions with the deprotected isoflavene.
‐ 35 ‐
Scheme 2-14: Reagents and conditions: i) Tl(O2CCF3)3, TFA, rt, 30 min; ii) conc. HCl, EtOAc, rt, 10 min.
2.4 Stability of Isoflavylium Salts The phenolic isoflavylium salts 117, 119 and 121 are stable to air and light and can be stored at room temperature. No changes were observed in the physical appearance of the compounds, while NMR analysis showed negligible evidence of degradation even 12 months after synthesis. The same cannot be said for acetylated salts such as 55. Within a week of synthesis, these salts change colour from bright yellow to dark purple and develop a strong odour of acetic acid. Protecting the salts from light, air and heat does little to slow the degradation process. HPLC and 1H NMR analysis of visibly degraded salts suggests that the decomposition products are the phenolic compound 117 as well as an intermediate monoacetoxy species.
2.5 Conclusion Six isoflavylium salts were generated from the corresponding isoflavenes. Hydride abstraction with tritylium hexafluorophosphate was performed on a variety of isoflavene scaffolds, including phenolic as well as acetylated species, to generate the corresponding salts in good to excellent yields. An alternative strategy, proceeding via a 2-hydroxyl isoflavene intermediate, was also investigated. Five of the isoflavylium salts described in this chapter, namely 113, 114, 117, 119 and 121, are entirely novel. While compound 55 has previously been reported as a reaction intermediate,163,164 this is the first time that the salt has been isolated and fully characterised. The reactions of these isoflavylium salts are discussed in Chapter Three.
‐ 36 ‐ CHAPTER THREE
SYNTHESIS OF 2-SUBSTITUTED ISOFLAVENES FROM ISOFLAVYLIUM SALTS
3.1 Background Isoflavonoid compounds have been shown to exhibit a variety of beneficial biological effects in humans.7,13,185 The primary aim of the present work was to generate novel isoflavonoids with the potential for medicinal applications. 2-Substituted isoflavenes have been identified as desirable synthetic targets, as discussed in Section 1.3. In particular, 2-substituted isoflavenes with structures such as 71 and 72 are expected to possess some degree of biological activity, as they share key structural features with compounds such as the SERM acolbifene 7 and the anti-cancer drug candidates triphendiol 15 and NV-128 16. Compounds 71 and 72 are, however, not the only synthetic targets. In order to effectively investigate the structure-activity relationships (SAR) of these isoflavonoids, it is desirable to construct a more structurally diverse learning set of compounds. One way to achieve this is via the introduction of a diverse array of substituents at C2, such as alkyl chains and substituents incorporating heteroatoms such as nitrogen and sulfur.
‐ 37 ‐
2-Substituted isoflavenes can be synthesised from isoflavylium salts, the synthesis and reactivity of which were discussed in Chapter Two. The electrophilic nature of the isoflavylium cation means that these species have the potential to react with a variety of nucleophiles, thus allowing for the introduction of a variety of substituents. Within the literature, there are a number of examples of isoflavylium and benzopyrylium ions participating in this type of reaction, which suggests that nucleophilic addition to isoflavylium salts is versatile method for generating new 2-substituted isoflavenes.
Isoflavylium salts readily undergo addition reactions with heteroatoms bearing lone pairs of electrons. In an early example of this methodology, Oluwadiya and coworkers180 generated 2-aminosubstituted products from isoflavylium salts via the nucleophilic addition of di-isopropylamine. In a similar fashion, Liepa162 treated isoflavylium salts 123 with 3-mercaptopropionic acid in order to generate isoflavenes with an acid-terminated alkyl chain at C2 (Scheme 3-1). The nucleophile was chosen on the basis of the reactivity of the thiol group, as well as the relative stability of the thioacetal products 124. Alcohols can also undergo nucleophilic addition reaction with isoflavylium salts to generate acetals, as demonstrated by Faragalla et al.163,164
‐ 38 ‐
Scheme 3-1: Reagents and conditions: R=H: 3-mercaptopropionic acid, AcOH, rt; R=OMe: 3-mercaptopropionic acid, AcOH, ethyldiisopropylamine, rt.
The electrophilic properties of isoflavylium salts have also been exploited to form new carbon-carbon bonds. Oluwadiya et al.180 observed that reactions of salts 125 with aniline 126 proceeded via an electrophilic aromatic substitution mechanism to generate the 2-p-aminophenyl species 127 (Scheme 3-2). Reactions were also observed between the isoflavylium cation and the double bond of 1,3-diarylpropenes 128. Subsequent acid-catalysed cyclisation gave the 2-flavan-3-yl isoflavenes 129.
Scheme 3-2: Reagents and conditions: 1% HCl-methanol, 50–60 °C.
In a further example of carbon-carbon bond formation by isoflavylium ions, Facklam et al.186 reported the synthesis of 2-diazomethyl isoflavenes via electrophilic diazoalkane substitution of diazomethyl phosphoryl compounds with an isoflavylium
‐ 39 ‐ tetrafluoroborate salt. More recently, Doodeman and coworkers178 treated benzopyrylium salts with a number of π-nucleophiles to generate 2-allyl, 2-cyano, 2- propargyl and 2-phenacetyl products. Faragalla et al.163,164 applied this methodology to generate 2-substituted isoflavenes 130 from the reaction of the isoflavylium salt 55 with trimethylsilyl- and tributyltin-substituted nucleophiles (Scheme 3-3).
+ - AcO O PF6 AcO O R
55 OAc 130 OAc
Nucleophile Product R = S S TMS N N TMS
TMS N(Boc)2 NHBoc
(Bu)3Sn Scheme 3-3: Reagents and conditions: DCM, rt.
Literature has shown that isoflavylium salts react with a broad range of nucleophiles and this reactivity can therefore be exploited to introduce a diverse variety of substituents at C2.161-164,180,186 It should be noted that the introduction of a 2-substitutent introduces a stereocentre to the isoflavene scaffold. Since the isoflavylium cation is achiral, nucleophilic addition at C2 will always produce racemic mixtures. Stereochemistry is an important consideration when developing new compounds for medicinal applications, and a drug candidate should ideally be synthesised as a single stereoisomer. However, the present work comprises only the preliminary stages of a drug development programme. At this point, the key research priority is the generation of a structurally diverse learning set. As has been demonstrated above, the chemistry of isoflavylium salts appears to be well-suited to this goal.
3.2 Reactions of Isoflavylium Salts with Organozinc Compounds Isoflavenes with phenyl and benzyl substituents have previously been identified as synthetic targets with the potential to exhibit interesting biological activity, particularly anti-cancer activity. From an SAR perspective, it would also be desirable to synthesise a
‐ 40 ‐ series of 2-alkylisoflavenes in order to investigate the impact of hydrophobic substituents of varying chain length and steric bulk on the biological activity of isoflavenes. Both alkyl and aryl substituents can be installed by treating isoflavylium salts with organometallic reagents. Grignard reagents were considered for this purpose as they have previously been used for the alkylation of pyrylium species.183 However, Grignard reagents are not suitable for the preparation of phenolic isoflavenes, such as those derived from phenoxodiol, due to the lack of suitable protecting groups. Silyl protecting groups are incompatible with the conditions used to generate isoflavylium hexafluorophosphate salts,163 while the removal of benzyl ethers requires hydrogenation, a process which would also reduce the isoflavene C2-C3 double bond. In contrast, organozinc compounds such as dialkyl zinc and aryl zinc halides do not require protection of phenols in such a fashion. Nevertheless, phenolic isoflavenes were protected as acetate esters prior to isoflavylium salt generation, as doing so improves solubility in organic solvents and facilitates the purification of products via recrystallisation. Acetate esters can be cleaved under relatively mild conditions to afford the corresponding phenolic isoflavenes.
Methylation of isoflavylium salts with dimethyl zinc proceeded in a straightforward manner. A solution of the isoflavylium salt 55 (prepared from diacetoxyphenoxodiol, as described in Section 2.2) was treated with dimethyl zinc solution at 0 °C and allowed to warm to room temperature (Scheme 3-4). Workup by extraction afforded the isoflavene 131 in 71% yield. Isoflavylium salts 113 and 114 were similarly methylated to give the dimethyl isoflavenes 132 and 133 in 21% and 26% yields, respectively. The yields of 132 and 133 were lower than that of 131 as the crude products did not readily form solids upon evaporation of solvent and thus had to be recrystallised. Deacetylation with potassium hydroxide afforded the phenolic compounds 134–136 in yields of 50–80%.
‐ 41 ‐
Scheme 3-4: Reagents and conditions: i) dimethylzinc solution (1.0 M in heptane, 1.3 eq.), dichloromethane, 0 °C → rt, 18 h; ii) KOH (1 M, aq, 2 eq.), methanol, rt, 1–2 h.
The introduction of the methyl group at C2 was confirmed by 1H NMR spectroscopy. In the spectrum of compound 131 (Figure 3-1), the H2 proton appeared as a quartet (1H, J = 6.6 Hz) at δ 5.45 (cf. the H2 protons in diacetoxyphenoxodiol, which appeared as a fine doublet (J = 1.4 Hz) at δ 5.15). The methyl group appeared as a doublet (3H, J = 6.6 Hz) at δ 1.39. Equivalent signals were also observed in the spectra of compounds 132–136 (Table 3-1). Multiplicities and coupling constants for 131 were identical to those reported. Apart from the H2 proton and the 2-methyl group, the spectra of 131– 136 were largely identical to those of the corresponding 2-unsubstituted isoflavenes.
Figure 3-1: 1H NMR spectrum of compound 131 in CDCl3
‐ 42 ‐
Table 3-1: Characteristic 1H NMR chemical shifts for 2-methylisoflavenes 131–136.
δ H2 δ CH3 131 5.45 1.39 132 5.70 1.29 133 5.41 1.38 134 5.43 1.23 135 5.58 1.28 136 5.38 1.22
The 2-ethyl isoflavene 137 was synthesised in a similar fashion to the 2-methyl analogues described above. Diethylzinc was added to a solution of the isoflavylium salt 55 at 0 °C and the reaction mixture was stirred at room temperature for 2.5 hours. The product 137 was obtained after extractive workup and recrystallisation from ethyl acetate (Scheme 3-5). The acetate protecting groups were removed with potassium hydroxide to give the phenolic isoflavene 138.
Scheme 3-5: Reagents and conditions: i) diethylzinc solution (1.0 M in hexanes, 1.3 eq.), dichloromethane, 0 °C → rt, 2.5 h; ii) KOH (1 M, aq, 2.7 eq.), methanol, rt, 2 h.
The 1H NMR spectrum of 137 (Figure 3-2) was similar to that of the corresponding 2- methyl analogue 131, but was slightly more complex due to the presence of diastereotopic protons on the ethyl group. As such, H2 appeared as a doublet of doublets (1H, J = 3.3 Hz, 9.6 Hz) at δ 5.20, while the ethyl CH2 protons appeared as separate multiplets at δ 1.83 and δ 1.60. The CH3 protons gave rise to a doublet of doublets (apparent triplet, 3H, J = 7.6 Hz) at δ 1.00. A similar pattern was observed in the spectrum of the phenolic analogue 138, where the H2, CH2 and CH3 protons appeared at δ 5.18, 1.63/1.45 and 0.93, respectively.
‐ 43 ‐
1 Figure 3-2: H NMR spectrum of compound 137 in CDCl3
The 2-ethyl isoflavene 137 was obtained in a lower yield (47%) than the corresponding methyl analogue 131 (71%). To some extent, this can be attributed to the fact that compound 137, unlike compound 131, had to be purified by recrystallisation. 1H NMR analysis of crude product 137 also indicated one major isoflavonoid impurity, which was identified as the 4-ethylisoflav-2-ene 139. The H4 proton of 139 appeared as a doublet of doublets (apparent triplet, 1H, J = 4.7 Hz) at δ 4.02, while the H2 proton appeared as a broad singlet at δ 6.89, which is consistent with an isoflav-2-ene scaffold.161 The remainder of the spectrum was very similar to that of the 2-substituted isomer. Consideration of the isoflavylium cation’s resonance structures offers some insight into how the 4-substituted isoflav-2-ene may be formed (Scheme 3-6). As discussed in Section 2.1, isoflavylium salts preferentially undergo nucleophilic addition at C2 to give 2-substituted isoflav-3-enes. However, addition reactions at C4 have also been reported in the literature.161,176,177
‐ 44 ‐ -CH CH AcO O 2 3 AcO O+ AcO O
- CH3CH2 OAc 55 OAc OAc
AcO O AcO O
OAc OAc 138 139
Scheme 3-6
The formation of the 4-substituted side product became significantly more pronounced as increasingly sterically demanding substituents were introduced. When the isoflavylium salt 55 was treated with diisopropyl zinc or phenylzinc bromide the crude product contained an equimolar mixture of the 2-substituted and 4-substituted isomers (Scheme 3-7). These mixtures could not be separated via recrystallisation or chromatographic means. When 55 was treated with benzylzinc bromide, the 4- substituted isoflav-2-ene 145 was the major product. Recrystallisation from acetonitrile afforded pure 145 in 10% yield. Compound 145 was treated with potassium hydroxide to give the phenolic isoflavene 146.
‐ 45 ‐
Scheme 3-7: Reagents and conditions: i) R2Zn or RZnBr, dichloromethane, 0 °C → rt, 1–3 h; ii) KOH, MeOH, rt, 1 h.
The 1H NMR spectra of isoflav-2-enes 145 and 146 bore many similarities to that of the corresponding 4-ethyl species 139. In the spectrum of compound 145 in CDCl3 (Figure 3-3), H2 appeared as a broad singlet at δ 6.81, while H4 appeared as a doublet of doublets (J = 4.0 Hz, 6.9 Hz) at δ 4.23. The diastereotopic CH2 protons of the benzyl moiety appeared as doublets of doublets at δ 2.99 (J = 4.0 Hz, 13.2 Hz) and δ 2.77 (J =
6.9 Hz, 13.2 Hz). Similarly, in the spectrum of compound 146, in d6-DMSO, H2, H4 and the CH2 protons appeared at δ 6.88, 4.26 and 2.87/2.64, respectively.
‐ 46 ‐
1 Figure 3-3: H NMR spectrum of compound 145 in CDCl3
3.3 Reactions of Isoflavylium Salts with Amines Nitrogenous functional groups are ubiquitous in biologically active molecules. Approximately 85% of known drugs incorporate at least one nitrogen atom into their structure.187 Additionally, the protonation of nitrogen atoms to form salts is a common procedure in the formulation of organic molecules into pharmaceutical preparations. With that in mind, the introduction of nitrogen-containing substituents to isoflavonoid compounds was an obvious avenue of investigation in the pursuit of biologically active compounds. Amines are good nucleophiles and they have been shown to react with isoflavylium salts to form 2-substituted isoflavenes.180 In the present work, this methodology has been applied in the synthesis of a series of novel, nitrogen-containing isoflavenes.
The addition of primary amines to the isoflavylium salt 55 was performed following a procedure similar to that used for the addition of organozinc compounds. As the amines were less reactive than the organozinc species, they could be added at room temperature. Thus, ethylamine solution was added to a solution of isoflavylium salt 55 in dichloromethane and the mixture was stirred for one hour at room temperature (Scheme 3-8). Workup by extraction followed by recrystallisation from ethyl acetate afforded the
‐ 47 ‐ 2-ethylamino isoflavene 147 in 49% yield. The benzylamino analogue 148 was prepared in a similar fashion in a yield of 52% using benzylamine. 4-Substituted side products such as those described in Section 3.2 were not observed.
Scheme 3-8: Reagents and conditions: RNH2 (1.3 eq.), DCM, 1–3 h, rt.
As was the case for the 2-alkyl compounds discussed in Section 3.2, the 1H NMR spectra of 147 and 148 in CDCl3 were similar to that of the parent isoflavene, diacetoxyphenoxodiol 109, apart from the signals associated with H2 and the newly introduced substituent. The introduction of an electronegative heteroatom adjacent to C2 resulted in a downfield shift in the signal of the H2 proton, which appeared as a broad singlet at δ 5.95 and 5.75 in the spectra of 147 and 148, respectively (cf. δ 5.15 in the spectrum of diacetoxyphenoxodiol). The NH proton was not visible in either case. In the spectrum of the ethylamino analogue 147, the CH2 protons were diastereotopic and appeared as doublets of quartets (each J = 7.1 Hz, 9.8 Hz) at δ 4.00 and 3.79. The CH3 protons appeared as a doublet of doublets (apparent triplet, 3H, J = 7.1 Hz) at δ 1.25. In the spectrum of the benzylamino compound 148, the CH2 protons appeared as doublets (each J = 10.1 Hz) at δ 4.17 and 4.11 while the protons of the additional phenyl ring appeared as a multiplet at δ 7.28.
Acetylated isoflavenes require deprotection prior to biological screening. While this procedure was straightforward in the case of the 2-alkylisoflavenes, deacetylation of 147 and 148 was problematic (Scheme 3-9). Any attempt to remove the acetate groups, even under relatively mild conditions, led to the formation of significant quantities of an isoflavonoid impurity which appeared to be lacking the 2-amino substituent. In some cases, the “impurity” was the only product isolated from the reaction. The compound formed when 147 and 148 were treated with potassium hydroxide in methanol was
‐ 48 ‐ identified as the 2-methoxy species 149. When deacetylation was attempted using imidazole in ethanol at reflux, the impurity was identified as the ethoxy compound 150. 1 Key H NMR signals for 149 and 150 in d6-DMSO are summarised in Table 3-2.
Scheme 3-9: Reagents and conditions: KOH, methanol, rt 1 h; or imidazole, ethanol, reflux, 2 h.
Table 3-2: Characteristic spectroscopic data of 2-alkoxyisoflavenes 149 and 150.
δ H2 δ CH2 δ CH3 149 5.90 (1H, br s) - 3.44 (3H, s) 150 5.96 (1H, br s) 3.81 (2H, m) 1.07 (3H, dd (app. t), J = 7.1 Hz)
The decomposition of compounds 147 and 148 was not without precedent. Dean and Varma182 previously demonstrated that isoflavene hemiaminal ethers can act as precursors to isoflavylium salts. In the literature example, trityl perchlorate was used to liberate a morpholine leaving group from C2, generating the reactive isoflavylium species. It appears that a similar process may have occurred when 147 and 148 were exposed to hydroxide or imidazole (Scheme 3-10). Cleavage of the amine group regenerated the isoflavylium cation, which reacted with the alcoholic solvent to give the isoflavene acetals 151 and 152. Subsequent deacetylation in the basic reaction conditions gave the phenolic compounds 149 and 150. The synthesis of 151 and 152 was replicated by stirring the diacetoxy isoflavylium salt 55 in methanol or ethanol at room temperature in the absence of base. Furthermore, thermal decomposition of the isoflavene hemiaminals 147 and 148 was observed in the absence of base. Attempts to recrystallise these compounds from boiling ethanol resulted in the formation of the 2- ethoxy species 152.
‐ 49 ‐
Scheme 3-10
3.3.1 Reactions of Isoflavylium Salts with Dimethylanilines Oluwadiya et al.180 reported that isoflavylium salts react with aniline via an electrophilic aromatic substitution mechanism to give 2-p-aminophenyl-substituted products. The introduction of an aniline moiety to the isoflavene scaffold is therefore a potential route to the 2,3-diarylbenzopyran structures 71 that have been identified as desirable synthetic targets. As the isoflavylium salt reacts at the phenyl ring rather than via the nitrogen atom, reactions with anilines also provide a way to introduce nitrogen to the isoflavene scaffold while avoiding the formation of unstable hemiaminal ethers.
When compound 55 was treated with 2,6-dimethylaniline, the salt reacted para to the amino group of the aniline to give the 2-aryl isoflavene 153, which was obtained in 52% yield after recrystallisation from ethyl acetate (Scheme 3-11). Isoflavene 153 was deacetylated with potassium hydroxide in methanol to give product 154 in 64% yield.
‐ 50 ‐
Scheme 3-11: Reagents and conditions: i) 2,6-dimethylaniline, DCM, rt, 45 min; ii) KOH (1 M, aq), methanol, rt, 15 min.
1 The H NMR spectra of compounds 153 and 154, in CDCl3 and d6-DMSO, respectively, were consistent with the introduction of a symmetrically-substituted phenyl ring at C2. The chemically equivalent H2″ and H6″ protons appeared as a broad singlet at δ 6.99 in the spectrum of compound 153 and at δ 6.82 in the spectrum of compound 154. Likewise, the protons of the two methyl groups at C3″ and C5″ appeared as a singlet at δ 2.09 and δ 1.96 in the spectra of compounds 153 and 154, respectively. These and other characteristic 1H NMR signals are summarised in Table 3-3.
Table 3-3: Characteristic 1H NMR data for compounds 153 and 154.
δ H2 δ NH2 δ H2″,6″ δ CH3 153 6.09 (1H, br s) 3.48 (2H, br s) 6.99 (2H, br s) 2.09 (6H, s) 154 6.04 (1H, br s) 4.59 (2H, br s) 6.82 (2H, br s) 1.96 (6H, s)
The isoflavylium salt 55 was also treated with 2,4-dimethylaniline (Scheme 3-12). In 2,4-dimethylaniline, the position para to the amine is occupied by a methyl group, leaving C6 as the most likely site for electrophilic aromatic substitution. However, the isoflavylium salt instead reacted via the nitrogen atom, generating the isoflavene 155 in 65% yield. Interestingly, when the isoflavylium salt was treated with 3,5- dimethylaniline, in which the position para to the amine group is unsubstituted, the reaction also occurred at the nitrogen atom to give 156 in 66% yield. While the isoflavylium salt 55 is a planar molecule, it is nonetheless a relatively large electrophile. The 6-position on 2,4-dimethylaniline faces minor steric hindrance from the neighbouring amine group. The 4-position on 3,5-dimethylaniline is somewhat
‐ 51 ‐ sterically hindered by the two adjacent methyl groups, while the 2-position of this compound faces minor steric hindrance from the neighbouring methyl and amine groups. Thus, when treated with 2,4-dimethylaniline or 3,5-dimethylaniline, the isoflavylium salt preferentially reacted with the more accessible amine group. Due to the instability of the hemiaminal ether moiety, which was discussed above, compounds 155 and 156 were not deacetylated.
5" 3" NH 2 6" 8 AcO O 2 NH 2' 6 3' 5 4 PF - 6' AcO O+ 6 OAc 155 5'
4" OAc 55 2" 6" 8 NH2 AcO O 2 NH 2' 6 3' 5 4 6' OAc 5' 156
Scheme 3-12: Reagents and conditions: ethyl acetate, reflux, 18 h.
1 In the H NMR spectra of compounds 155 and 156 in CDCl3, the H2 and NH protons appeared as doublets with J values consistent with vicinal coupling (Table 3-4). The H3″, H5″ and H6″ protons of compound 155 appeared at δ 6.83, 6.96 and 7.27, respectively, while the two methyl groups appeared as singlets at δ 2.19 and 1.91. The spectrum of compound 156 featured fewer additional signals due to the symmetrical substitution pattern on the aniline ring. The H2″ and H6″ protons appeared as a broad singlet at δ 6.60 while the H4″ proton appeared as a broad singlet at δ 6.37. The methyl protons appeared as a singlet at δ 2.18.
‐ 52 ‐ Table 3-4: Characteristic 1H NMR data for compounds 155 and 156. δ H2 δ NH 155 5.57 (1H, d, J = 9.7 Hz) 6.52 (1H, d, J = 9.7 Hz) 156 6.56 (1H, d, J = 9.4 Hz) 6.79 (1H, d, J = 9.4 Hz)
3.3.2 Reactions of Isoflavylium Salts with Nitrogen Heterocycles The reactions of isoflavylium salts with secondary amines were also investigated. Isoflavylium salt 55 was reacted with N-trimethylsilylpyrrolidine to give isoflavene 157 in 12% yield (Scheme 3-13). The poor yield of 157 was due in part to the formation of a 4-substituted side product, analogous to those observed in the synthesis of the alkylated isoflavenes discussed in Section 3.2. It was also apparent that isoflavene 157 underwent some degree of decomposition during the recrystallisation process, a phenomenon which was also observed during the purification of the 2-ethylamino and 2-benzylamino hemiaminal analogues 147 and 148. Decomposition of the product may also have occurred in the reaction of 55 with N-trimethylsilylmorpholine. The 2-N-morpholinyl product 158 was obtained in 26% yield.
2" 3"
8 4" AcO O 2 N 5" 2' 6 3' 5 4 N - 6' OAc + PF6 TMS AcO O 157 5'
OAc 3" 2" 55 O O 8 N AcO O 2 N 5" TMS 6" 2' 6 3' 5 4 6' OAc 5' 158
Scheme 3-13: Reagents and conditions: DCM, rt, 3 h (157), 22 h (158).
‐ 53 ‐ Addition of N-heterocycles at C2 induced a marked downfield shift of the H2 proton in the 1H NMR spectrum. H2 appeared at δ 5.96 and 5.74 in the spectra of compounds 157 and 158, respectively, compared to the equivalent signal at δ 5.15 in the parent diacetoxyisoflavene. In the spectrum of compound 157, the H2″ and H5″ protons appeared as a multiplet at δ 3.01, while H3″ and H4″ appeared as a multiplet at δ 2.82. The spectrum of compound 158 was somewhat more complex, as the H2″ and H6″ protons were diastereotopic. These four protons appeared as two multiplets (each 2H) at δ 3.03 and 2.64. The H3″ and H5″ protons appeared as a doublet of doublets (apparent triplet, 4H, J = 4.7 Hz) at δ 3.61.
N-Trimethylsilylpyrrolidone was also reacted with the isoflavylium salt 55 to give the 2-substituted product 159 in 78% yield (Scheme 3-14). The cyclic amide species proved to be more chemically robust than the amine-derived products 157 and 158. Isoflavene 159 was readily deacetylated with potassium hydroxide to give the phenolic product 160 in 97% yield.
Scheme 3-14: Reagents and conditions: i) 1-trimethylsilyl-2-pyrrolidinone, DCM, rt, 22 h; ii) KOH (1 M, aq), methanol, rt, 45 min.
The introduction of an amide moiety adjacent to C2 induced a significant downfield shift of the H2 signal in the 1H NMR spectra of compounds 159 and 160. The H2 proton appeared as a singlet at δ 7.16 in the spectrum of 159 and δ 6.98 in the spectrum of 160. This proton is shifted further downfield than the equivalent signal in the spectra of the 2-amino substituted isoflavenes 147, 148 and 155–158. In the spectrum of 159, the H3″, H4″ and H5″ protons appeared as multiplets (each 2H) at δ 2.45, 1.83 and 3.12, respectively. In the spectrum of 160, it was apparent that the H5″ protons were non- equivalent as they appeared as two distinct multiplets (each 1H) at δ 3.16 and 3.03. The H3″ and H4″ protons appeared as multiplets (each 2H) at δ 2.27 and 1.82.
‐ 54 ‐ 3.4. Reactions of Isoflavylium Salts with Thiols Thiols are good nucleophiles, and previous work by Liepa162 indicated that thiol- functionalised compounds add readily to isoflavylium salts. Thus, treating isoflavylium salts with thiols may be an efficient way to generate new 2-substituted analogues. In the first instance, the isoflavylium salt 55 was treated with ethanethiol and benzylthiol (Scheme 3-15) to generate thiol-derived equivalents of the 2-ethylamino and 2- benzylamino analogues previously described in Section 3.3. The thioacetals 161 and 162 were obtained in 53% and 63% yield, respectively. The reactions of isoflavylium salts with thiophenols are of particular interest as they provide an access to the target 2,3-diaryl structure 72. Thus, compound 55 was also treated with 4-chlorothiophenol to generate thioacetal 163 in 64% yield.
Scheme 3-15: Reagents and conditions: RSH, DCM, rt, 2–18 h.
The addition of a thiol group to the isoflavene scaffold induced a significant downfield shift of the H2 signal in the 1H NMR spectra of compounds 161–163. This proton appeared as a singlet at δ 6.47, 6.22, and 6.58 in the spectra of compounds 161, 162 and 163, respectively (cf. δ 5.15 in the spectrum of the parent isoflavene). The shift is greater in magnitude than that observed after the addition of primary amine-derived compounds discussed in the previous section. In the spectrum of compound 161, the
CH2 protons appeared as a multiplet at δ 2.76 while the CH3 protons appeared as a triplet (3H, J = 7.4 Hz) at δ 1.35. In the case of the benzyl analogue 162, the diastereotopic CH2 protons appeared at δ 4.00 and 3.77 as doublets (each 1H, J = 13.6 Hz) due to geminal coupling. The phenyl protons of compound 162 appeared as a multiplet at δ 7.35. In compound 163, the H3″, H5″, H2″ and H6″ protons appeared as two doublets (each 2H, J = 8.5 Hz) at δ 7.45 and 7.29.
‐ 55 ‐ The isoflavene thioacetals 161 and 162 decomposed to the 2-methoxy species 149 upon treatment with potassium hydroxide in methanol. However, they proved to be relatively stable to deacetylation with imidazole (Scheme 3-16), suggesting that the thioacetals were more stable than their corresponding hemiaminal ethers. The phenolic ethyl analogue 164 was obtained in 97% yield, while the relatively poor yield of the benzyl analogue 165 (38%) suggests that some decomposition may have occurred. However, the thiophenol adduct 163 could not be deacetylated cleanly.
Scheme 3-16: Reagents and conditions: imidazole (6 eq.), ethanol, reflux, 3–5 h.
As deacetylation of compound 163 proved difficult, an alternative approach was devised involving the addition of the thiophenol to a phenolic isoflavylium salt, thereby bypassing the need for deprotection. The preparation of the phenolic isoflavylium salt 117 was discussed in Section 2.3. The salt and 4-chlorothiophenol were stirred in glacial acetic acid using a method adapted from the literature162 (Scheme 3-17). The product 166 was obtained in 50% yield. In a similar fashion, propanethiol was added to isoflavylium salt 117 to give isoflavene 167 in 65% yield.
Scheme 3-17: Reagents and conditions: RSH, glacial acetic acid, rt, 1 h.
‐ 56 ‐ 3.5 Reactions of Isoflavylium Salts with Indoles The indole moiety is present in a great number of biologically significant molecules. As such, indoles and indole derivatives continue to attract considerable attention in the research community.188-190 Previous work in our group has investigated the synthesis of indole-flavonoid hybrids such as compound 168 in an attempt to capitalise on the biological activity of both classes of compounds.191 These hybrid compounds feature a 3-nitrochromene moiety attached to the C7 position of a 4,6-dimethoxyindole. It was predicted that the analogous isoflavonoid-indole hybrid 169 could be synthesised by reacting the isoflavylium salt 55 with an appropriately substituted indole. However, any attempts to perform such a reaction resulted only in the recovery of starting material. It is thought that the steric bulk of the two reactants may have prevented electrophilic attack at the indole C7 position.
OMe Ph OMe Ph 4 3 5 Ph Ph 6 2 MeO N MeO N 7 1 H H O O2N O OH HO
168 169
While the formation of C2-C7 linked isoflavene-indole adducts appeared to be unfeasible, there remained the possibility of attaching the isoflavene to other positions on the indole scaffold. 3-Substituted indoles, such as skatole, are activated towards electrophilic attack at C2. Indeed, when skatole was reacted with the isoflavylium salt 55 (Scheme 3-18), the C2-C2 linked adduct 170 was obtained in 36% yield after purification. In a similar manner, the addition of indole-3-acetonitrile to the salt 55 generated compound 171 in a yield of 42%. Compounds 170 and 171 were deacetylated with potassium hydroxide to give phenolic products 172 and 173, both in 59% yield, respectively.
‐ 57 ‐
Scheme 3-18: Reagents and conditions: i) 3-R-indole, DCM, rt, 19–22 h; ii) KOH (1 M, aq), methanol, rt, 48 h.
As in the case of other 2-substituted isoflavenes, the 1H NMR spectra of the 2-indoyl compounds 170–173 exhibited a considerable downfield shift in the H2 proton relative to the unsubstituted isoflavene (Table 3-5). The introduction of an indole moiety caused the spectra of 170–173 to become somewhat convoluted in the aromatic region. However, it was clear in each case that the isoflavene-indole adducts contained four more aromatic protons than were accounted for by the isoflavene scaffold, as well as a broad singlet corresponding to the indole NH. Crucially, the only singlets observed in the aromatic region of each spectrum were those attributable to the NH, H2 and H4 protons. Had the isoflavylium salt reacted at a position other than the indole C2, an additional broad singlet corresponding to the indole H2 would have been observed ca. δ 7.15, as in the 1H NMR spectrum of skatole.
Table 3-5: Characteristic 1H NMR chemical shifts for isoflavene-indole adducts 170– 173. δ H2 δ NH 170 6.51 7.90 171 7.00 7.39 172 6.57 8.04 173 7.03 7.68
While 3-substituted indoles are reactive towards electrophilic attack at C2, 2-substituted indoles undergo reactions at C3. Thus, C2-C3 linked isoflavene-indole adducts can be prepared by treating isoflavylium salts with 2-substituted indoles. Thus, the treatment of
‐ 58 ‐ isoflavylium salt 55 with 2-phenylindole (Scheme 3-19) generated the adduct 174 in 48% yield.
Scheme 3-19: Reagents and conditions: 2-phenylindole, DCM, rt, 19 h.
As in the 1H NMR spectra of indole adducts 170–173, the H2 proton of compound 174 was shifted downfield relative to H2 of the parent isoflavene, appearing as a broad singlet at δ 6.89. As expected, nine additional aromatic protons were observed due to the phenylindole moiety, as well as a broad singlet at δ 8.19 corresponding to the indole NH. The phenyl protons appeared as a multiplet at δ 7.66.
Given the reactivity of isoflavylium salts with the C2 and C3 positions of indoles, it follows that the salts may also react with pyrroles to generate isoflavenes with a less bulky heterocyclic substituent at C2. However, attempts to react isoflavylium salt 55 with pyrrole resulted in the formation of substantial mixtures. The sticky, amorphous appearance of the product was suggested that di- or polymerisation reactions may have occurred. The reaction between salt 55 and 2-acetylpyrrole was more successful (Scheme 3-20) and the product 175 was obtained in 38% yield after recrystallisation. Compound 175 was deacetylated with potassium hydroxide to give the phenolic product 176 in 65% yield.
‐ 59 ‐
Scheme 3-20: Reagents and conditions: i) 2-acetyl pyrrole, DCM, rt, 22 h; ii) KOH (1 M, aq), methanol, rt, 48 h.
The H2 proton appeared as a broad singlet at δ 6.19 and 6.20 in the 1H NMR spectra of compounds 175 and 176, respectively. While this represents a significant downfield shift relative to the 2-unsubstituted isoflavene, the effect was less pronounced than for the 2-indolyl substituted compounds 170–174. The H4″ and H5″ protons appeared as multiplets at δ 6.93 and 6.87 in the spectrum of compound 175 and as overlapping multiplets at δ 6.83 in the spectrum of compound 176. These chemical shifts are consistent with those reported for H3 and H4 in the 1H NMR spectrum of 2- acetylpyrrole,192 indicating that the isoflavylium salt indeed reacted at C5 on the pyrrole ring. The structure of compound 175 contains two acetate groups and one methyl ketone, which gave rise to singlets at δ 2.36, 2.30 and 2.25, respectively. In the spectrum of the phenolic compound 176, the protons of the methyl ketone appeared as a singlet at δ 2.24.
3.6 Reactions of Isoflavylium Salts with α-Methyl Ketones Given the instability of isoflavene hemiaminal ethers and thioacetals as noted above, the investigation turned towards nucleophiles that could form carbon-carbon bonds with the isoflavylium ion. Enolate anions are good nucleophiles which react through their α- carbon atom. Therefore, the addition of enolate anions to isoflavylium salts provides a means to access a variety of stable 2-substituted isoflavenes. Reactions with enolates also introduce a carbonyl group to the isoflavene scaffold, which provides a potential starting point for further chemical elaboration. Enolate anions can be generated via the deprotonation of ketones at the α-position. α-Methyl ketones were chosen as enolate precursors in this study in order to minimise steric hindrance around the nucleophilic α- carbon.
‐ 60 ‐ 3.6.1 Reactions of Isoflavylium Salts with Acetone Acetone, being the simplest example of an α-methylketone, was selected as a model for the investigation of enolate addition to isoflavylium salts. Thus, salt 55 was dissolved in acetone along with one equivalent of imidazole (Scheme 3-21). The reaction proceeded at room temperature to give product 177 in 70% yield. During optimisation experiments, it was discovered that compound 177 was also formed in the absence of any added base. Merely stirring salt 55 in acetone at room temperature gave compound 177 in 68% yield after recrystallisation. Isoflavene 177 was deacetylated with potassium hydroxide to give the phenolic product 178 in a yield of 72%.
Scheme 3-21: Reagents and conditions: i) acetone, imidazole, rt, 18 h, or acetone, rt 21 h; ii) KOH (1 M, aq), methanol, rt, 30 min.
The structure of isoflavene 177 was confirmed by examination of its 1H NMR spectrum (Figure 3-4). The chemical shift of the H2 proton (δ 5.93) is downfield of the corresponding signal (δ 5.15) in the spectrum of the parent isoflavene, which is consistent with the introduction of a substituent at C2. As in the case of the 2-ethyl analogue 137, the methylene protons adjacent to C2 are diastereotopic. Thus, these protons, as well as H2, appeared as doublets of doublets. The acetyl protons appeared as a singlet at δ 2.17. The 1H NMR spectrum of the deacetylated compound 178 was very similar. Key signals are detailed in Table 3.6.
‐ 61 ‐
1 Figure 3-4: H NMR spectrum of compound 177 in CDCl3
Table 3-6: Characteristic 1H NMR data for compounds 177 and 178. 177 178 δ H2 5.93 (dd, J = 2.1 Hz, 10.2 Hz) 6.74 (dd, J = 2.3 Hz, 10.1 Hz) δ CHa 3.16 (dd, J = 10.2 Hz, 16.5 Hz) 2.89 (dd, J = 10.1 Hz, 15.9 Hz) δ CHb 2.36 (dd, J = 2.1 Hz, 16.5 Hz) 2.36 (dd, J = 2.3 Hz, 15.9 Hz)
δ CH3 2.17 2.13
The observation that acetone reacted with the isoflavylium salt 55 in the absence of added base raised questions about the reaction mechanism. Acetone itself is a poor nucleophile, and reactions through the α-carbon are unlikely to occur unless the ketone tautomerises to the corresponding enol or is deprotonated to generate an enolate anion. Both of these processes require initiation by a base (or an acid, in the case of tautomerisation) yet at least one of them must have occurred in the presence of the – – isoflavylium salt alone. The isoflavylium counterion (PF6 or Cl ) is a weak base and is unlikely to deprotonate the ketone. Another possibility is that the isoflavylium cation initiated the formation of the enolate ion by first coordinating to the acetone oxygen atom (Scheme 3-22). This increases the acidity of the acetone moiety, which is deprotonated by water (the reaction was performed in air) to give an acetal intermediate.
‐ 62 ‐ The intermediate then decomposes to produce the enolate ion while regenerating the isoflavylium cation.
Scheme 3-22
After the successful formation of the desired product 177 from the reaction of isoflavylium salt 55 with acetone, the reaction was repeated with another isoflavylium salt. The 4-substituted isoflavylium chloride salt 121 was stirred in acetone at room temperature for 3 days (Scheme 3-23). The solvent was evaporated to approximately 20% of its initial volume and the product 179 was obtained by filtration in a yield of 72%.
Scheme 3-23: Reagents and conditions: acetone, rt, 3 d.
The addition of the acetone-derived substituent at C2 was confirmed by 1H NMR spectroscopy. As expected, the spectrum of the 4-substituted compound 179 shared some similarities with the spectra of analogues 177 and 178, which bore the same C2
‐ 63 ‐ substituent. H2 appeared as a doublet of doublets (1H, J = 2.5 Hz, 10.2 Hz) at δ 5.56. The diastereotopic methylene protons appeared as doublets of doublets at δ 3.19 (1H, J
= 10.2 Hz, 15.8 Hz) and δ 2.57 (1H, J = 2.5 Hz, 15.8 Hz). The CH3 protons appeared as a singlet at δ 2.15.
3.6.2 Reaction of the Isoflavylium Salt 112 with 4-Methylpentan-2-one Once the reactivity of acetone towards isoflavylium salts had been established, more complex α-methyl ketones were investigated. The reaction of 55 with 4-methylpentan- 2-one at reflux in ethyl acetate afforded the isoflavene 180 in 27% yield after purification (Scheme 3-24). Compound 180 was deacetylated with potassium hydroxide to give the phenolic product 181 in a yield of 88%.
Scheme 3-24: Reagents and conditions: i) 4-methylpentan-2-one, ethyl acetate, reflux, 1 h; ii) KOH (1 M, aq), ethanol, rt, 18 h.
Unlike acetone, 4-methylpentan-2-one is asymmetrically substituted about the carbonyl group. While reactions of the corresponding enolate are expected to occur via the less sterically hindered C1, there is also the possibility that the reaction may proceed via the other α-carbon, C3. In the 1H NMR spectra of compounds 180 and 181, the H2 proton appeared as a doublet of doublets (Table 3-7). This splitting pattern indicated that H2 was coupling to two protons, which can only occur if there is a methylene group adjacent to C2. Therefore, the reaction with 4-methylpentan-2-one must have occurred via the C1 α-methyl group. The chemical shifts and splitting patterns observed for the methylene protons adjacent to C2 are similar to those reported for the acetone-derived compounds described above, except that one of the methylene protons appeared as a multiplet and was obscured by other signals. Other 1H NMR signals arising from the 2- substituent are summarised in Table 3-7. The two methyl groups are diastereotopic.
‐ 64 ‐ They appeared as distinct doublets (each 3H, J = 6.7 Hz) in the spectra of compounds 180 and 181.
Table 3-7: Characteristic 1H NMR data for compounds 180 and 181. 180 181 δ H2 5.97 (dd, J = 2.3 Hz, 10.1 Hz) 5.75 (dd, J = 2.5 Hz, 9.9 Hz) δ CHaCO 3.14 (dd, J = 10.1 Hz, 16.3 Hz) 2.91 (dd, J = 9.9 Hz, 15.8 Hz) δ CHbCO 2.29 (m) 2.29 (m)
δ CH2CH(CH3)2 2.26 (d, J = 6.9 Hz) 2.33 (d, J = 7.1 Hz)
δ CH2CH(CH3)2 2.10 (m) 2.31 (m) a δ CH3 0.90 (d, J = 6.5 Hz) 0.86 (d, J = 6.6 Hz) b δ CH3 0.88 (d, J = 6.5 Hz) 0.84 (d, J = 6.6 Hz)
3.6.3 Reactions of Isoflavylium Salt 55 with Acetophenones As outlined in Sections 1.3 and 3.1, isoflavenes with aryl substituents at C2 are of particular interest due to their structural similarity to known biologically active molecules. In compound 182, which could be generated from the reaction between the isoflavylium salt 55 and acetophenone, the phenyl ring is one bond length further away from the isoflavene core than in the target 2,3-diaryl isoflavene 72. However, as indicated by the three-dimensional overlay in Figure 3-5, there is still considerable structural similarity between compound 182 and the anti-cancer drug candidate triphendiol 15. Therefore, it is predicted that isoflavene analogues of this type could exhibit the desired biological activity.
‐ 65 ‐
Figure 3-5: Three-dimensional overlay of analogue 182 with triphendiol 15.
Isoflavene 183 was synthesised from salt 55 and acetophenone using the method described for compound 180 previously (Scheme 3-25). The product was obtained in 73% yield. Deacetylation of compound 183 with potassium hydroxide gave the product 182 in a yield of 83%.
Scheme 3-25: Reagents and conditions: i) acetophenone, ethyl acetate, reflux, 1 h; ii) KOH (1 M, aq), ethanol, rt, 18 h.
The attachment of acetophenone to C2 of the isoflavene scaffold was confirmed by 1H NMR spectroscopy (Table 3-8). The spectra of compounds 182 and 183 exhibited
‐ 66 ‐ similar patterns to the other spectra discussed in this section. H2 and the adjacent methylene protons appeared as doublets of doublets at chemical shifts consistent with those observed previously. The protons of the phenyl ring gave rise to three additional signals in the aromatic region. H2″ and H6″ appeared as a doublet of doublets, as did H3″ and H5″. The H4″ proton appeared as a triplet of triplets.
Table 3-8: Characteristic 1H NMR data for compounds 182 and 183. 183 182 δ H2 6.18 (dd, J = 2.2 Hz, 9.6 Hz) 5.91 (dd, J = 2.1 Hz, 9.9 Hz) δ CHaCO 3.82 (dd, J = 9.6 Hz, 16.5 Hz) 3.63 (dd, J = 9.6 Hz, 16.4 Hz) δ CHbCO 2.76 (dd, J = 2.2 Hz, 16.5 Hz) 2.82 (dd, J = 2.1 Hz, 16.4 Hz) δ H2″, H6″ 7.85 (dd, J = 1.4 Hz, 7.9 Hz) 7.85 (dd, J = 1.3 Hz, 8.0 Hz) δ H3″, H5″ 7.42 (dd, J = 7.6 Hz, 7.9 Hz) 7.48 (dd, J = 7.5 Hz, 8.0 Hz) δ H4″ 7.52 (tt, J = 1.4 Hz, 7.6 Hz) 7.63 (tt, J = 1.3 Hz, 7.5 Hz)
After the successful synthesis of analogue 182, substituted acetophenones were investigated as a means of generating more isoflavene analogues with aryl substituents at C2. Reactions with para-substituted acetophenones were uniformly successful. Compounds 184–188 were obtained in yields of 50–75% after recrystallisation (Scheme 3-26). Deacetylation with potassium hydroxide gave phenolic products 189–193 in 80– 95% yield. The isoflavylium salt 55 was also treated with a number of ortho- and meta- substituted acetophenones. However, these reactions resulted in mixtures from which the 2-substituted isoflavenes could not be isolated. This have may have been due to deactivation of the acetyl group and/or side reactions on the acetophenone aromatic ring. The reaction of salt 55 with 2-acetyl pyridine was also investigated, but this process only ever led to the recovery of starting material.
‐ 67 ‐
Scheme 3-26: Reagents and conditions: i) 4-R-acetophenone, ethyl acetate, reflux, 1 h; ii) KOH (1 M, aq), ethanol, rt, 18 h
Characteristic signals in the 1H NMR spectra of compounds 184–193 are summarised in Table 3-9 below. The H2 and methylene protons appeared as doublets of doublets, as in the spectra of the other α-methyl ketone-derived isoflavenes described above. H2″ and H6″ appeared as a doublet in the aromatic region, as did H3″ and H5″ (each 2H, J = 8.5- 9.0 Hz). The spectra of compounds 184–186 and 189–191 included additional signals arising from the substituent on the phenyl ring. The methyl group appeared as a singlet at δ 2.39 in the spectrum of compound 184 and at δ 2.36 in spectrum of compound 189. The ethyl group appeared as a quartet (2H, J = 7.6 Hz) at δ 2.68 and a triplet (3H, J = 7.6 Hz) at δ 1.24 in the spectrum of compound 185 and as a quartet (2H, J = 7.5 Hz) at δ 2.66 and a triplet (3H, J = 7.5 Hz) at δ 1.18 in the spectrum of compound 190. The methoxy group appeared as a singlet at δ 3.85 in the spectrum of compound 186 and at δ 3.89 in the spectrum of compound 191.
Table 3-9: Characteristic 1H NMR data for compounds 189–198. δ H2 δ CHaCO δ CHbCO 184 6.17 3.79 2.73 (dd, J =2.1 Hz, 9.6 Hz) (dd, J =9.6 Hz, 16.5 Hz) (dd, J =2.1 Hz, 16.5 Hz) 185 6.17 3.79 2.74 (dd, J =2.2 Hz, 9.7 Hz) (dd, J =9.7 Hz, 16.4 Hz) (dd, J =2.2 Hz, 16.4 Hz) 186 6.16 3.78 2.69 (dd, J =2.1 Hz, 9.6 Hz) (dd, J =9.6 Hz, 16.4 Hz) (dd, J =2.1 Hz, 16.4 Hz) 187 6.13 3.76 2.72 (dd, J =2.2 Hz, 9.6 Hz) (dd, J =9.6 Hz, 16.3 Hz) (dd, J =2.2 Hz, 16.3 Hz)
‐ 68 ‐ 188 6.13 3.78 2.72 (dd, J =2.3 Hz, 9.6 Hz) (dd, J =9.6 Hz, 16.1 Hz) (dd, J =2.3 Hz, 16.1 Hz) 189 5.89 3.61 2.75 (dd, J =2.1 Hz, 9.8 Hz) (dd, J =9.8 Hz, 16.2 Hz) (dd, J =2.1 Hz, 16.2 Hz) 190 5.90 3.61 2.77 (dd, J =2.1 Hz, 9.7 Hz) (dd, J =9.7 Hz, 16.3 Hz) (dd, J =2.1 Hz, 16.3 Hz) 191 6.03 3.77 2.72 (dd, J =2.1 Hz, 9.6 Hz) (dd, J =9.6 Hz, 16.3 Hz) (dd, J =2.1 Hz, 16.3 Hz) 192 5.88 3.60 2.84 (dd, J =2.4 Hz, 9.7 Hz) (dd, J =9.7 Hz, 16.3 Hz) (dd, J =2.4 Hz, 16.3 Hz) 193 5.91 3.62 2.68 (dd, J =2.0 Hz, 9.7 Hz) (dd, J =9.7 Hz, 16.3 Hz) (dd, J =2.0 Hz, 16.3 Hz)
3.6.4 Reactions of Isoflavylium Salt 55 with Other Acetyl-Substituted Aromatics In a similar fashion to the preparation of phenyl-substituted compounds 184–188 from acetophenones, enolate chemistry was also used to introduce a naphthyl moiety to the isoflavene scaffold (Scheme 3-27). Isoflavylium salt 55 and 1-acetylnaphthalene were combined in dichloromethane at room temperature. An extractive workup afforded a viscous golden brown oil, which was triturated with ethyl acetate to give product 194 as an amorphous solid in 49% yield. Isoflavene 194 was deacetylated with potassium hydroxide to give the phenolic compound 195 in a yield of 84%.
Scheme 3-27: Reagents and conditions: i) 1-acetylnaphthalene, DCM, rt, 1 d; ii) KOH (1 M, aq), ethanol, rt, 18 h.
‐ 69 ‐ In the 1H NMR spectra of compounds 194 and 195, H2 and the neighbouring methylene protons exhibited the characteristic splitting pattern described previously in this section (Table 3-10). The naphthyl group appeared as seven distinct signals in the aromatic region.
Table 3-10: Characteristic 1H NMR data for compounds 194 and 195. 194 195 δ H2 6.23 (dd, J =2.3 Hz, 9.8 Hz) 5.90 (dd, J =2.4 Hz, 10.1 Hz) δ CHaCO 3.85 (dd, J =9.8 Hz, 16.1 Hz) 3.53 (dd, J =10.1 Hz, 15.8 Hz) δ CHbCO 2.91 (dd, J =2.3 Hz, 16.1 Hz) 3.12 (dd, J =2.4 Hz, 15.8 Hz) δ H2″ 7.71 (dd, J =1.2 Hz, 7.2 Hz) 7.88 (dd, J =1.1 Hz, 7.2 Hz) δ H3″ 7.45 (dd, J =7.2 Hz, 8.2 Hz) 7.54 (dd, J =7.2 Hz, 8.3 Hz) δ H4″ 7.98 (m) 8.14 (m) δ H5″ 7.87 (m) 8.01 (m) δ H6″ 7.60 (m) 7.65 (m) δ H7″ 7.53 (m) 7.60 (m) δ H8″ 8.61 (dd, J =1.2 Hz, 8.2 Hz) 8.44 (dd, J =1.5 Hz, 8.2 Hz)
As discussed in Section 3.5, the reaction between the isoflavylium salt 55 and 2- acetylpyrrole occurred via electrophilic aromatic substitution at the pyrrole C5 position to generate compound 177. In contrast, when salt 55 was treated with 2-acetylfuran, the reaction proceeded via an enolate mechanism to generate isoflavene 196 in 30% yield (Scheme 3-28). Given the low yield of compound 196, it is possible that a reaction also occurred at the furan C5, but that the corresponding product could not be isolated. Compound 196 was deacetylated with potassium hydroxide to give the phenolic product 197 in a yield of 64%.
‐ 70 ‐
Scheme 3-28: Reagents and conditions: i) 2-acetylfuran, DCM, rt, 1 d; ii) KOH (1 M, aq), ethanol, rt, 18 h.
The structures of compounds 201 and 202 were confirmed by 1H NMR spectroscopy. Each spectrum included three doublets of doublets corresponding to H2 and the adjacent methylene group (Table 3-11) which confirmed that the reaction with 2- acetylfuran occurred at the methyl group. The protons on the furan ring appeared as three additional signals in the aromatic region. Chemical shifts and coupling constants are summarised in Table 3-11.
Table 3-11: Characteristic 1H NMR data for compounds 196 and 197. 196 197 δ H2 6.06 (dd, J =2.4 Hz, 10.1 Hz) 5.85 (dd, J =2.4 Hz, 10.1 Hz) δ CHaCO 3.63 (dd, J =10.1 Hz, 15.4 Hz) 3.63 (dd, J =10.1 Hz, 15.4 Hz) δ CHbCO 2.67 (dd, J =2.4 Hz, 15.4 Hz) 2.65 (dd, J =2.4 Hz, 15.4 Hz) δ H3″ 7.56 (dd, J =0.7 Hz, 1.7 Hz) 7.98 (dd, J =0.7 Hz, 1.7 Hz) δ H4″ 6.50 (dd, J =1.7 Hz, 3.7 Hz) 6.68 (dd, J =1.7 Hz, 3.6 Hz) δ H5″ 7.10 (dd, J =0.7 Hz, 3.7 Hz) 7.30 (dd, J =0.7 Hz, 3.6 Hz)
3.6.5 Derivatives of Carbonyl Compounds The carbonyl group on the C2 substituent can serve as a starting point for further chemical elaboration. One facile example is the formation of a hydrazone. The acetone adduct 177 was treated with 2,4-dinitrophenylhydrazine at reflux in ethanol to give the hydrazone 198 in 67% yield (Scheme 3-29). The phenolic analogue 199 was obtained in 91% yield by deacetylation of compound 198 with potassium hydroxide.
‐ 71 ‐
5" O2N O2N 6"
NH 3" NH
O NO2 N NO2 N 8 AcO O AcO O HO O 2 i ii 2' 6 3' 5 4 OAc OAc 6' OH 5' 177 198 199
Scheme 3-29: Reagents and conditions: i) 2,4-dinitrophenylhydrazine, ethanol, reflux, 16 h; ii) KOH (1 M, aq), ethanol, rt, 2 d.
Formation of the hydrazone induced only small changes in the 1H NMR signals of H2 and the adjacent methylene protons (Table 3-12, cf. δ 5.93 (H2) and 3.16/2.36
(CH2COCH3) for the precursor 177). The protons on rings A and B were unaffected. The hydrazone NH appeared as a broad singlet at δ 11.02 in the spectrum of compound
198 (in CDCl3) and at δ 10.80 in the spectrum of compound 199 (in d6-DMSO). The protons on the dinitrophenyl ring appeared as three additional signals in the aromatic region (Table 3-12).
Table 3-12: Characteristic 1H NMR data for compounds 198 and 199. 198 199 δ H2 5.69 (dd, J =3.1 Hz, 9.7 Hz) 5.73 (dd, J =3.1 Hz, 9.6 Hz) δ CHaCO 2.95 (dd, J =9.7 Hz, 14.5 Hz) 2.77 (dd, J =9.6 Hz, 14.5 Hz) δ CHbCO 2.60 (dd, J =3.1 Hz, 14.5 Hz) 2.59 (dd, J =3.1 Hz, 14.5 Hz) δ H3″ 9.14 (d, J =2.6 Hz) 8.89 (d, J =2.5 Hz) δ H5″ 8.33 (dd, J =2.6 Hz, 9.6 Hz) 8.35 (dd, J =2.5 Hz, 9.6 Hz) δ H6″ 7.89 (d, J =9.6 Hz) 7.78 (d, J =9.6 Hz) δ NH 11.02 (br s) 10.80 (br s)
Another relatively simple transformation is the reduction of the carbonyl group to the corresponding alcohol. This was achieved by treating the acetophenone-derived analogue 182 with sodium borohydride in ethanol at reflux (Scheme 3-30). The reaction
‐ 72 ‐ not only reduced the carbonyl group on C2, but also removed the acetate protecting groups to give product 200 in 77 % yield.
Scheme 3-30: Reagents and conditions: NaBH4, ethanol, reflux, 19 h.
The 1H NMR spectrum of compound 200 indicated that two products had been obtained, in a ratio of 2:1. It is believed that the two compounds are diastereomers. 2-Substituted isoflavenes such as compound 182 possess a stereocentre at C2. Reduction of the carbonyl group introduces a second stereocentre adjacent to the oxygen. Thus the reduced product 200 was obtained as a mixture of diastereomers 200a and 200b and their respective enantiomers. It was not possible to determine which isomer was the major product, due to the considerable overlap between the spectra of the two compounds, which could not be separated chromatographically.
Key 1H NMR signals for the major and minor products are summarised in Table 3-13 below. Reduction of the carbonyl group was confirmed by the appearance of new signals corresponding to the OH and neighbouring CH protons, as well as upfield shifts in the signals corresponding to H2 and the methylene group (cf. δ 5.91 (H2) and
3.63/2.82 (CH2COPh) in the acetophenone-substituted isoflavene 182. The absence of the characteristic acetate singlets ca. δ 2.30, as well as the appearance of two broad
‐ 73 ‐ singlets at δ 9.40 and 9.37 corresponding to the phenolic OH protons, confirmed that compound 200 was deacetylated.
Table 3-13: Characteristic 1H NMR data for compound 200. Major product Minor product δ H2 5.12 (dd, J =2.0 Hz, 5.0 Hz) 5.18 (m) δ CHaCHOH 3.44 (m) 3.12 (m) δ CHbCHOH 1.99 (m) 1.90 (m)
δ CH2CHOH 4.85 (dd, J =5.7 Hz, 10.1 4.85 (dd, J =5.7 Hz, 10.1 Hz) Hz)
δ CH2CHOH 4.48 (br s) 4.19 (br d, J =10.0 Hz)
3.7 Reduction of 2-Substituted Isoflavenes to Isoflavans Isoflave-3-enes are readily reduced to the corresponding isoflavan scaffold by means of catalytic hydrogenation.140,136 In the present work, this methodology was applied to 2- substituted isoflavenes. As detailed in Chapter Six, the isoflavans described here did not possess any desirable biological activity. Therefore, only a few examples of 2- substituted isoflavans were synthesised.
The acetylated isoflavenes 131 and 137 were hydrogenated at atmospheric pressure with
5% Pd/Al2O3 as the catalyst (Scheme 3-31). The corresponding isoflavans 201 and 202 were obtained in 84% and 85% yield, respectively. The 2-N-pyrrolidinone-substituted compound 159 was not reduced when hydrogenated with Pd/Al2O3. However, hydrogenation with 5% Pd/C paste gave the desired isoflavan 203 in 59% yield. The isoflavans were deacetylated with potassium hydroxide to give phenolic products 204– 206 in 77–91% yield.
‐ 74 ‐
Scheme 3-31: Reagents and conditions: i) 5% Pd/Al2O3 or 5% Pd/C , ethyl acetate, H2, rt, 1–4 h; ii) KOH (1 M, aq), ethanol, rt, 1–3 h.
The 1H NMR spectrum of compound 203 is characteristic of these six 2-substituted isoflavans. Reduction of the chromene ring had little impact on the aromatic protons, apart from an upfield shift (δ 7.53 to δ 7.16) in the signal for H2′ and H6′. The protons on the 2-substituent were unaffected. More significant changes were observed for the protons of Ring C. These included a considerable upfield shift in the H2 proton, which appears at δ 6.10 (cf. δ 7.16 in the spectrum of the isoflavene 159). The H2 proton appears as a doublet (1H, J = 3.2 Hz) due to coupling with the newly introduced H3. The two H4 protons, designated H4a and H4b, are diastereotopic. H4a appeared as a doublet of doublets (1H, J = 6.9 Hz, 16.3 Hz) at δ 3.45, while H4b appeared as a doublet of doublets (1H, J = 3.0 Hz, 16.3 Hz) at δ 2.96. The coupling constants are consistent with vicinal coupling to H3 and geminal coupling between the two H4 protons. H3 appeared at δ 3.48 (ddd, J = 3.0 Hz, 3.2 Hz, 6.9 Hz).
2-Substituted isoflavenes such as compounds 131, 137 and 164 possess a chiral centre at C2. As these compounds were prepared from achiral isoflavylium salts in a non- stereoselective manner, they were obtained as racemic mixtures. Reduction of the C3- C4 bond, as described above, introduces a second stereocentre at C3. While hydrogenation adds two hydrogen atoms via the same face of the molecule – guaranteeing a cis configuration about C3-C4 – the hydrogen atoms can be added syn or anti to the C2-substitutent, which leads to the formation of cis and trans diasteromers such as 203a and 203b. However, the 1H NMR results discussed above indicate that hydrogenation of the three isoflavenes led to the formation of only one racemic product in each case.
‐ 75 ‐
O O
AcO O N AcO O N
OAc OAc 203a 203b H R H R O R O H O R O H H R R H R H H R 1 2 1 2
In order to determine the stereochemistry of the product, conformational isomers must also be considered. 3-D molecular modelling indicates that the chroman ring adopts a pseudo-chair confirmation. The C2 and C3 substituents can therefore occupy equatorial or axial positions, as indicated above. The four conformers can be distinguished on the basis of the dihedral torsion angles between H2, H3 and H4. The angles predicted by energy-minimised 3-D models of the conformers were compared with values obtained from 1H NMR coupling constants and the Karplus equation (Table 3-14). Based on these data, it appeared as though the product was a racemic the trans diaxial isomer 203b-2 and its enantiomer. This was expected, as the trans-diaxial conformer is the most stable, since it minimises steric hindrance.
Table 3-14: Calculated dihedral torsion angles for conformational isomers of isoflavan 203. Karplus 203a-1 203a-2 203b-1 203b-2 H2-C2-C3-H3 60° or 117° 54° 53° 171° 76° H3-C3-C4a-H4a 43° or 133° 34° 177° 171° 47° H3-C3-C4b-H4b 60° or 116° 84° 58° 53° 71°
‐ 76 ‐ 3.8 Conclusion Isoflavylium salts such as the diacetoxyphenooxodiol-derived species 55 are versatile precursors to 2-substituted isoflavenes. Compound 55 reacted with a diverse range of nucleophiles, including organometallics, amines, thiols, indoles and α-methylketones, to generate a variety of novel 2-substituted isoflav-3-enes, as well as the 4-benzyl isoflav- 2-enes 145 and 146. 2-Substituted isoflavenes were readily converted to novel 2- substituted isoflavans via catalytic hydrogenation. While the 2-alkyl isoflavenes 131, 134, 137 and 138 have been reported previously,157,193 the isoflavylium salt approach represents a novel synthetic route to these products.
‐ 77 ‐ CHAPTER FOUR
SYNTHESIS OF 2-SUBSTITUTED ISOFLAVENES FROM 2-SUBSTITUTED ISOFLAVONES
4.1 Background 4.1.1 Synthesis of Isoflavenes from Isoflavones The synthesis of 2-substituted isoflavenes from isoflavylium salts was discussed in Chapters Two and Three. While this synthetic strategy was used to introduce a variety of substituents at C2, it did not provide access to a number of target compounds, including 2-phenyl- and 2-benzylisoflavenes, as well as isoflavenes with alkyl substituents larger than ethyl groups, due to competing reactions at C4 when isoflavylium salts were treated with organometallic reagents. Since the aforementioned substituents could not be introduced directly to the isoflavene scaffold, an alternative synthetic route was explored. It has been demonstrated106,136,139 that isoflavenes can be readily synthesised from isoflavones via reduction and dehydration of the resulting isoflavanol. It follows that 2-substituted isoflavenes could be synthesised from 2- substituted isoflavones in a similar fashion (Scheme 4-1). According to this strategy, the substituent at C-2 has to be introduced during the formation of the isoflavone scaffold.
Scheme 4-1
4.1.2 Synthesis of 2-Substituted Isoflavones The synthesis of 2-substituted isoflavones is well documented in the literature, and typically involves a cyclisation reaction with a 2-hydroxydeoxybenzoin. In an early example of this methodology, Baker and Robinson142 treated deoxybenzoins 207 with a series of symmetrical anhydrides and their corresponding sodium carboxylate salts to generate the 2-substituted isoflavones 208 after a hydrolytic workup. Many others have adopted similar approaches using an anhydride105,141,143-146 or acyl chloride117,147-151,194
‐ 78 ‐ in the presence of a base such as triethylamine or pyridine. Reactions of this type are sometimes carried out using a phase transfer catalyst.101,152-154.
2 2 Scheme 4-2: Reagents and conditions: i) (R CO)2O, NaO2CR , reflux; ii) KOH (aq), reflux.
While the synthesis of 2-substituted isoflavones from deoxybenzoins is typically performed as a one-pot procedure, the reaction involves multiple steps. Baker and coworkers194 proposed a mechanism whereby polyhydroxydeoxybenzoins underwent acylation at C2, followed by reaction and cyclization at the benzylic methylene group and then dehydration to form the isoflavone scaffold. Esters formed from the acylation of other phenol groups besides C2 in the first step could be cleaved with dilute acid or base to obtain the free phenol. The acylation and cyclisation reactions have also been performed as separate steps, as in the isoflavone synthesis reported by Pelter et al.149,150 (Scheme 4-3). The methoxy-protected deoxybenzoin 209 was treated with an acyl chloride to generate the intermediate 210. Cyclisation was initiated by treating 210 with trimethylsilyl chloride, which converted the ketone to a silyl enolate 211. Intramolecular cyclisation gave the acetal intermediate 212, which was dehydrated in situ to generate the isoflavone 213.
‐ 79 ‐
Scheme 4-3: Reagents and conditions: i) ClOC(CH2)nCO2R, pyridine, rt, 3 d; ii) DMF,
TMSCl, Et3N, reflux.
The acylation-cyclisation approach described above has been used to generate a variety of 2-substituted isoflavones where the substituent is attached to C2 via a carbon-carbon bond. Reactions with deoxybenzoin can also be used to introduce a heteroatom at this position. Kim and coworkers102,195-197 have reported numerous syntheses of 2- (alkylthio)isoflavones from the treatment of 2-hydroxydeoxybenzoins with carbon disulfide and alkyl halides in the presence of a phase transfer catalyst. In another example, Alaimo et al.198 demonstrated that 2-N-morpholinyl isoflavones can be prepared from deoxybenzoins using a morpholinium salt.
4.2 Synthesis of 2-Substituted Isoflavones via Cyclisation of Deoxybenzoins In the present work, a series of 2-substituted isoflavones were prepared via an acylation- cyclisation approach, using conditions adapted from Lévai et al.143 This strategy provided access to a variety of alkyl and aryl substituents via reactions with appropriately substituted anhydrides or acyl chlorides. Friedel-Crafts acylation of resorcinols 23 and 214 with 4-hydroxyphenylacetic acid 24 gave deoxybenzoins 25 and 215 in good to excellent yields (Scheme 4-4). These deoxybenzoins were reacted at reflux with symmetrical anhydrides and acyl chlorides in triethylamine to generate the isoflavone diesters 216–227, which were immediately treated with aqueous sodium hydroxide to afford the phenolic isoflavones 228–239.
‐ 80 ‐
Scheme 4-4: Reagents and conditions: i) ZnCl2, 130 °C, 1.5 h (25); BF3·OEt2, 80 °C, 2 2 3.5 h (220); ii) (R CO)2O or R COCl, triethylamine, reflux, 22 h; iii) NaOH, MeOH, reflux, 0.5–2 h.
Cyclisation of the deoxybenzoins was confirmed by 1H NMR spectroscopy. The spectrum of the 2-propyl analogue 230 (Figure 4-1) is typical of compounds 228-239. The formation of the isoflavone ring C induced a slight downfield shift in some of the protons on Ring A. The H5, H6 and H8 protons of the isoflavone 230 appeared at δ 7.85, 6.88 and 6.82, respectively while the corresponding protons (H6, H5 and H3) in the deoxybenzoin appeared at δ 7.94, 6.43 and 6.32. Additionally, the benzylic methylene protons of deoxybenzoin 25 appeared as a characteristic singlet at δ 4.16. This signal was not present in the spectrum of the cyclised product 230. Cleavage of the esters and formation of the 7- and 4′- phenolic groups was confirmed by the appearance of two broad singlets at δ 10.73 and 9.48, corresponding to the OH protons,. The spectra of compounds 228–232 and 234–239 also included signals corresponding to the newly introduced 2-substituent. These are summarised in Table 4-1, below.
‐ 81 ‐
Figure 4-1: 1H NMR spectrum of isoflavone 230 in d6-DMSO.
Table 4-1: Characteristic 1H NMR data for 2-substituted isoflavones. R2 δ
228 2.23 (3H, s, CH3)
229 2.49 (2H, q, J = 7.2 Hz, CH2CH3), 1.15 (3H, t, J = 7.2 Hz, CH2CH3)
230 2.46 (2H, t, J = 7.2 Hz, CH2CH2CH3), 1.62 (2H, qt, app. sextet, J = 7.2 Hz,
CH2CH2CH3), 0.83 (3H, t, J = 7.6 Hz, CH2CH2CH3)
231 2.99 (1H, septet, J = 6.9 Hz, CH(CH3)2), 1.25 (6H, d, J = 6.9 Hz,
CH(CH3)2)
232 2.57 (2H, t, J = 7.2 Hz, CH2CH2CH2CH3), 1.68 (2H, tt, apparent quintet, J
= 7.2 Hz, CH2CH2CH2CH3), 1.31 (2H, qt, apparent sextet, J = 7.2 Hz,
CH2CH2CH2CH3), 0.84 (3H, t, J = 7.2 Hz, CH2CH2CH2CH3) 234 7.35 (5H, m, ArH) 235 8.56 (2H, d, J = 6.1 Hz, H3″,5″), 7.32 (2H, d, J = 6.1 Hz, H2″,6″)
236 2.23 (3H, s, CH3)
237 2.55 (2H, q, J = 7.2 Hz, CH2CH3), 1.20 (3H, t, J = 7.2 Hz, CH2CH3)
238 2.50 (2H, t, J = 7.2 Hz, CH2CH2CH3), 1.67 (2H, sextet, J = 7.2 Hz,
CH2CH2CH3), 0.85 (3H, t, J = 7.6 Hz, CH2CH2CH3) 239 7.38 (5H, m, ArH)
‐ 82 ‐ Steric and electronic factors appeared to play a role in determining the success of the cyclisation reaction. The 8-methylisoflavones 236–239, as well as the 2-phenyl and 2- pyridyl analogues 234 and 235, were obtained in poor overall yields due to the extensive purification required to remove unreacted or partially reacted starting material. Attempts to synthesise 2-t-butyl and 2-benzylisoflavones (using trimethylacetic anhydride and phenylacetyl chloride, respectively) were unsuccessful, resulting only in the recovery of the deoxybenzoin 25.
The overall synthesis of 2-substituted isoflavones proceeds via acylation of the deoxybenzoin 25 or 215, followed by an intramolecular cyclisation and subsequent dehydration to form ring C of the isoflavone scaffold149,194 (Scheme 4-5). Treatment of the resulting isoflavone diester 240 with sodium hydroxide gives the phenolic isoflavone 241. Mechanistically, acylation of the deoxybenzoin occurs first at the relatively activated 4- and 4′-OH groups, forming the diester 242. It was observed that when R2 = phenyl, the deoxybenzoin diester species had limited solubility in triethylamine, which may have contributed to the relatively poor yield of the 2- phenylisoflavones. For cyclisation to occur, the intermediate 242 must subsequently be acylated at either at the 2-OH group149 or at the benzylic methylene position.194 Bulky anhydrides or acyl chlorides may have limited access to these relatively hindered positions. If cyclisation has not occurred, the reaction of the deoxybenzoin 242 or its subsequent intermediates with sodium hydroxide affords the starting deoxybenzoin 25 or 215.
‐ 83 ‐
2 2 Scheme 4-5: Reagents and conditions: i) (R CO)2O or R COCl, triethylamine, reflux; ii) NaOH, MeOH, reflux.
Isoflavones 228–235 were acetylated at this stage in the isoflavene synthesis. The reasons for performing this step were twofold. Firstly, it had been observed in the present work that acetylated isoflavonoid compounds tend to form powders or crystalline solids, while their phenolic counterparts often formed sticky solids or oils. Furthermore, acetylation improves the solubility of these compounds in the solvents to be employed in subsequent reactions. Thus, isoflavones 228–235 were treated at reflux with acetic anhydride and potassium carbonate in acetone to give the acetylated compounds 243–248 in moderate to good yields (Scheme 4-6). Acetylation was confirmed by 1H NMR spectroscopy. The acetate groups appeared as two sharp singlets ca. δ 2.36 and 2.32, while the phenolic protons were no longer visible.
‐ 84 ‐ HO O R AcO O R
O O OH OAc 228: R=Pr 243: R=Pr(46%) 229: R=iPr 244: R=iPr(77%) 230: R=Bu 245: R=Bu(52%) 231: R=CF3 246: R=CF3 (71%) 232: R=Ph 247: R=Ph(70%) 233: R=4-Py 248: R=4-Py(70%)
Scheme 4-6: Reagents and conditions: Ac2O, K2CO3, acetone, reflux, 1 h.
4.3 Synthesis of 2-Substituted Isoflavanols Isoflavones 243–247 were reduced to the corresponding isoflavanols 249–253 via hydrogenation with 5% palladium on charcoal (Scheme 4-7). The hydrogenation of analogue 247 was complete within 24 hours, while the hydrogenation of compounds 243–246 took between six and seven days to reach completion. This was considerably longer than the reaction times reported for the hydrogenation of diacetoxydaidzein136. Additionally, the 2-substituted isoflavones were treated with significantly more palladium on charcoal than the 2-unsubstituted compound (400–500% by mass versus 15–20%). It appears as though the presence of a substituent at C2 may hinder the interaction between the isoflavone and the catalyst surface, thus decreasing the rate of the reaction. Palladium catalysts were found to be unsuitable for the hydrogenation of the pyridyl analogue 248. This is thought to be due to a coordination interaction between the pyridyl nitrogen and the palladium. Hydrogenation with platinum(IV) oxide gave the pyridyl isoflavanol 254 in moderate yield. The reaction was complete within eight hours.
‐ 85 ‐
Scheme 4-7: Reagents and conditions: H2 (1 atm), 5% Pd/C (243–247), PtO2 (248), EtOAc, rt, 8 h–7 d.
The reduction of the C2–C3 double bond introduces two new stereocentres to the isoflavonoid scaffold. The reduction of the carbonyl group introduces a third stereocentre at C4. While eight isoflavanol stereoisomers are possible, only four (255– 258) are generated via hydrogenation. The hydrogenation reaction occurs at the catalyst surface, which means that the two hydrogen atoms will always add to the double bond from the same face of the molecule. For this reason, the substituents at C2 and C3 must always be cis relative to one another, while substitution about the C3–C4 bond may be cis or trans. As the next synthetic step would convert C3 and C4 to sp2 hybridisation, thus removing these two stereocentres, the isoflavanol diastereomers were not separated.
The 1H NMR spectrum of the C2-propyl substituted compound 249 is representative of isoflavanols 249–254. The aromatic protons of analogue 249 were shifted slightly upfield relative to the parent isoflavone, with very little difference in chemical shift between the cis and trans isomers. The newly-introduced H2 appeared as a doublet of doublet of doublets at δ 4.43 for the cis isomer and 4.23 for the trans isomer. This
‐ 86 ‐ proton is coupled to H3, as well as to the diastereotopic methylene protons adjacent to C2. H3 appeared as a doublet of doublets at δ 3.36 (cis) and 2.85 (trans), while H4 appeared as a broad doublet at δ 5.18 (cis) and 4.14 (trans). The exchangeable 4-OH proton was not observed in any of the isoflavanol 1H NMR spectra, which were acquired in CDCl3. However, coupling between H4 and the OH was observed in the spectra of analogues 251 and 252, with H4 of the cis isomer appearing as a doublet of doublets in each case. The chemical shifts and coupling constants for H2, H3 and H4 in the spectra of isoflavanols 249–254 are summarised in Table 4-2. The trans isomers of products 253 and 254 were present only in small amounts and their spectra could not be assigned fully.
Table 4-2: Characteristic 1H NMR data for isoflavanols 249–254. δ H2 δ H3 δ H4 249 cis 4.43 (ddd, J = 2.3 Hz, 4.9 3.36 (dd, J = 2.3 Hz, 5.18 (br d, Hz, 8.1 Hz) 7.0 Hz) J = 7.0 Hz) 249 trans 4.26 (ddd, J = 2.5 Hz, 6.4 2.85 (dd, J = 10.3 Hz, 4.94 (br d, Hz, 10.1 Hz) 10.1 Hz) J = 10.3 Hz) 250 cis 4.18 (dd, J = 2.2 Hz, 11.0 3.54 (dd, J = 2.1 Hz, 5.13 (br d, Hz) 7.0 Hz) J = 7.0 Hz) 250 trans 3.96 (dd, J = 2.1 Hz, 10.1 2.95 (dd, J = 10.0 Hz, 4.93 (br d, Hz) 10.1 Hz) J = 10.0 Hz) 251 cis 4.41 (ddd, J = 2.3 Hz, 5.1 3.37 (dd, J = 2.3 Hz, 5.18 (br dd, J = Hz, 7.4 Hz) 7.0 Hz) 7.0 Hz, 8.1 Hz) 251 trans 4.26 (ddd, J = 3.2 Hz, 7.7 2.85 (dd, J = 10.3 Hz, 4.94 (br d, Hz, 10.7 Hz) 10.7 Hz) J = 10.3 Hz) 252 cis 4.83 (dq, J = 2.5 Hz, 6.5 Hz) 3.72 (dd, J = 2.5 Hz, 5.25 (br dd, J = 6.9 Hz) 6.9 Hz, 9.7 Hz) 252 trans 4.72 (dq, J = 6.5 Hz, 11.5 3.21 (dd, J = 10.3 Hz, 4.99 (br d, Hz) 11.5 Hz) J = 10.3 Hz) 253 cis 5.59 (br d, J = 2.1 Hz) 3.65 (dd, J = 2.1 Hz, 5.45 (br d, 7.1 Hz) J = 7.1 Hz) 254 cis 5.56 (br d, J = 2.4 Hz) 3.67 (dd, J = 2.4 Hz, 5.45 (br d, 7.0 Hz) J = 7.1 Hz)
‐ 87 ‐ 3 As expected, JH3-H4 differed considerably between the cis and trans isomers of each isoflavanol, reflecting the different spatial relationship between H3 and H4 in each case. 3 Interestingly, JH2-H3 also differed between the two isomers, despite the fact that the stereochemistry about the C2-C3 bond must always be cis for mechanistic reasons. Using the 2-propyl isoflavanol 249 as an example, the Karplus equation predicts H3- C3-C4-H4 dihedral torsion angles of 42° for the cis isomer and 146° for the trans isomer. The predicted H2-C2-C3-H3 dihedral torsion angles for the cis and trans isomers are 64° and 28°, respectively. These values suggest that in the case of cis isoflavanols 255, the pyran ring adopts a pseudo-chair conformation, with the 2- substituent and the 4-OH in equatorial positions. The trans isoflavanols 256 appear to adopt a more planar conformation, situating the C2 and C3 substituents approximately in the same plane as the benzopyran ring system. These conclusions are consistent with the conformational analysis of 2-unsubstituted isoflavanols reported by Kim et al.. It was determined the cis-isoflavanols adopted a pseudo-chair conformation, while the trans-isomers adopted a flatter, half-chair conformation.
O R O R
OH OH
255 256
H H H O H R O R OH H Ph HO H Ph
The ratio of cis to trans isoflavanol diastereomers varied according to the C2 substituent. For the alkyl substituted isoflavanols, the cis:trans ratio was typically around 3:1, which is consistent with that observed in the hydrogenation of daidzein.136 For the aryl substituted analogues, the ratio was approximately 10:1. This selectivity can be accounted for by considering the mechanism of the hydrogenation reaction. The reduction of isoflavones to isoflavanols is a two-step process whereby the C2-C3 double bond is reduced prior to the carbonyl group. Due to the requirement for cis geometry
‐ 88 ‐ about the C2-C3 bond in catalytic hydrogenation, one face of the resulting isoflavanone intermediate 257 is more sterically hindered than the other (Scheme 4-7). As the less hindered face has better access to the catalyst surface, hydrogenation of the carbonyl group is more likely to occur from the face opposite the C2 and C3 substituents, resulting in cis stereochemistry about the C3-C4 bond. The stereoselectivity of the hydrogenation was more pronounced in the case of the 2-aryl isoflavanols 253 and 254. This is thought to be due to the more sterically demanding nature of the phenyl and pyridyl substituents, but may also be influenced by interactions between the aromatic substituents on C2 and C3.
Scheme 4-7
4.4. Dehydration of 2-Substituted Isoflavanols Isoflavanols 249–253 were dehydrated with phosphoric acid in toluene at reflux to give isoflavenes 258–262 in moderate to excellent yields (Scheme 4-8). Isoflavenes 258 and 259 required purification by preparative HPLC, resulting in poor recovery of these products. Compounds 258–262 were treated with potassium hydroxide in methanol to generate the phenolic isoflavenes 263–265 in moderate to good yields.
Scheme 4-8: Reagents and conditions: i) H3PO4, toluene, reflux, 2–5 h; ii) KOH (1 M, aq), MeOH, rt, 10–20 min.
‐ 89 ‐ Attempts to dehydrate the pyridyl analogue 255 using the method above were unsuccessful. It is likely that the phosphoric acid protonated the pyridyl nitrogen atom, thus decreasing the compound’s solubility in toluene. Phosphorus pentoxide was found to be a more suitable dehydration reagent (Scheme 4-9). Treatment of the isoflavanol 255 with phosphorous pentoxide at room temperature generated the isoflavene 268 in 84% yield. Compound 268 was treated with potassium hydroxide in methanol to give the deprotected compound 269 in a yield of 36%.
Scheme 4-9: Reagents and conditions: i) P2O5, DCM, rt, 20 h; ii) KOH (1 M, aq), MeOH, rt, 10–20 min.
The 1H NMR spectrum of the C2-trifluoromethyl substituted compound 266 (Figure 4-2) is typical of the isoflavenes 263–267 and 269. The signals of the aromatic protons were largely unaffected by dehydration, but significant changes were observed for the protons of ring C. H2 appeared as a quartet (J = 2.9 Hz, 9.8 Hz) at δ 6.25, due to coupling with the flourine atoms on the 2-substituent. The allylic H4 appeared as a broad singlet at δ 7.03. These chemical shifts are consistent with those observed for the 2-substituted isoflavenes described in Chapter 3. The deshielding effect of 2-substitutents of analogues 266, 267 and 269, resulted in a greater downfield shift for H2 than was observed in the 2-alkyl isoflavenes 263-265. Key chemical shifts for isoflavenes 263– 267 and 269 are summarised in Table 4-3.
‐ 90 ‐ Table 4-3: Characteristic 1H NMR data for isoflavenes 263–267 and 269. δ H2 δ H4 263 5.26 (dd, J = 2.9 Hz, 9.8 Hz) 6.70 (br s) 264 5.15 (d, J = 5.9 Hz) 6.66 (br s) 265 5.25 (dd, J = 2.5 Hz, 9.5 Hz) 6.69 (br s) 266 6.25 (q, J = 7.2 Hz) 7.03 (br s) 267 6.33 (br s) 7.05 (br s) 269 6.42 (br s) 7.07 (br s)
4.4 Synthesis of Isoflavanones 4-Substituted isoflavans such as triphendiol and the related compound NV-128 exhibit potent activity against a number of cancer cell lines.54,69,71 These compounds have been synthesised via Grignard addition to the carbonyl group of an isoflavanone.38,138,165 Isoflavanones can be prepared via partial hydrogenation of isoflavones136,139,165. It follows, therefore, that 2-substituted analogues of triphendiol can be prepared from 2- substituted isoflavones in a similar fashion (Scheme 4-10).
Scheme 4-10
Isoflavones 228–230 and 238 were dissolved in a mixture of ethanol and aqueous potassium hydroxide and hydrogenated at room temperature with 10% Pd/Al2O3 as a catalyst (Scheme 4-11). The hydrogenation of daidzein to dihydrodaidzein is typically complete within 72 h.139 However, the conversion of isoflavones 228–230 and 238 to the corresponding isoflavanones proceeded at a much slower rate, likely due to steric hindrance from the substituent at C2. After two weeks under hydrogen, the reactions of 228–230 and 238 afforded a mixture of starting material and the desired product. Isoflavanones 270–273 were isolated by chromatographic means. No further chemistry was performed on products 270–273, as the compounds were obtained in insufficient
‐ 91 ‐ quantities. Hydrogenation of isoflavones 234, 236 and 237 was also attempted, but these reactions failed to generate significant quantities of the desired isoflavanones. Even after several weeks under hydrogen, the product mixtures isolated from the hydrogenations contained >90% starting material.
Scheme 4-11: Reagents and conditions: H2 (1 atm), 10% Pd/Al2O3, EtOH, KOH (1 M, aq), rt, 1–3 weeks.
The 1H NMR spectrum of the C2-ethyl substituted analogue 271 is typical of isoflavanones 270–273. The newly-introduced H2 proton appeared as a doublet of triplets (J = 5.2 Hz, 10.2 Hz) at δ 4.56. H3 appeared as a doublet (J = 10.2 Hz) at δ 3.74. The aromatic protons appeared at similar chemical shifts compared to those of the parent isoflavone, with only a slight upfield shift observed for H6. An upfield shift was observed in the signal of the ethyl CH2 protons, which appeared as a doublet of quartets
(J = 5.2 Hz, 7.2 Hz) at δ 1.48. The CH3 protons appeared as a triplet (J = 7.2 Hz) at δ 0.92.
4.5. Conclusion Twelve 2-substituted isoflavones, ten of them novel, were prepared via the cyclisation of deoxybenzoins. Six of these analogues were converted to 2-substituted isoflavenes via reduction and subsequent dehydration of the corresponding isoflavanols. This synthetic strategy provides a route to 2-substituted isoflavenes that are not readily accessible via the reactions of isoflavylium salts discussed in Chapter Three. Four 2- substituted isoflavones were also partially reduced to generate the corresponding isoflavanones, which may serve as a starting point for further elaboration of the 2- substituted isoflavonoid scaffold.
‐ 92 ‐ CHAPTER FIVE
PREPARATION OF ISOFLAVENE EPOXIDES
5.1 Background The 4-substituted isoflavans triphendiol 15 and NV-128 16 exhibit cytotoxic and anti- proliferative activity against a number of cancer cell lines.54,69,71,72 As discussed in Section 1.1.2, compound 16 is of particular interest due to its ability to target cancer stem cells. This type of activity has significant implications for the treatment of recurrent and chemoresistant tumours.70 4-Aryl isoflavans are thus attractive synthetic targets given the promising biological activity associated with this scaffold. Isoflavans 15 and 16 are both cis-substituted about the C3-C4 bond. This stereochemistry can be achieved via catalytic hydrogenation of the corresponding 4-aryl isoflav-3-enes 274, in turn derived from isoflavanones 275 via Grignard chemistry38,139,165 (Scheme 5-1). While the synthesis of 4-aryl isoflavans via the hydrogenation of isoflavenes guarantees cis stereochemistry about the C3-C4 bond, the product generated is a racemic mixture. It is therefore desirable to explore alternative synthetic approaches to 4-substituted isoflavans, particularly where there is the potential to introduce the 4-substitutent in a stereocontrolled fashion.
One alternative approach to 4-substituted isoflavans is to introduce the C4 substituent via nucleophilic addition to epoxides 276. Epoxides 276 could be generated via the oxidation of isoflav-3-enes 275. Enantioselective epoxide synthesis can be achieved via catalytic techniques such as the Sharpless and Jacobsen epoxidation reactions. Therefore, exploration of isoflavene epoxide chemistry may potentially be used to establish a stereoselective route to 4-substituted isoflavans. Additionally, isoflav-3-ene epoxides are themselves interesting synthetic targets, as they have not yet been reported in the literature.
‐ 93 ‐
Scheme 5-1
While 3,4-epoxy isoflavonoid species such as 276 have not yet been described in the literature, a number of research groups have reported the synthesis of 2,3-epoxy derivatives of isoflavones,141,143,199-202 flavones171 and chromones.172,203 Bezuidenhoudt and co-workers201 demonstrated that isoflavones 278 readily formed epoxides 279 when treated with hydrogen peroxide under basic conditions (Scheme 5-2). Acid-catalysed methanolysis of epoxides 279 generated products 280 and 281. It was determined that the regioselectivity of the ring-opening reaction depended on the substitution pattern on ring B of the isoflavone.
Scheme 5-2: Reagents and conditions: i) H2O2, KOH, H2O, EtOH, dioxane, 0 °C; ii) MeOH, p-toluenesulfonic acid, 2,2,2-trifluoroethanol, rt.
‐ 94 ‐ Adam and co-workers141,143,199,202 generated several series of isoflavone epoxides using a variety of oxidising agents, including dimethyldioxirane, hydrogen peroxide and sodium hypochlorite. Asymmetric epoxidation was initially achieved using Jacobsen’s Mn(III) salen complexes in conjunction with dimethyldioxirane.199,202 It was later determined that epoxidation of isoflavones 282 under Weitz-Scheffer conditions, in conjunction with an optically active phase transfer catalyst 283, afforded epoxides 284 in superior yields and with a greater degree of enantioselectivity than other methods141 (Scheme 5-3).
RO N+
N H
R R1O O R3 R1O O R3 R2 283 R2 O
O O 282 284
Scheme 5-3: Reagents and conditions: cumyl hydroperoxide, KOH, H2O, toluene, 0 → 20°C.
Direct oxidation of an alkene is not the only method by which epoxides can be generated. Donnelly and Maloney172 demonstrated an alternative approach in their synthesis of chromone epoxides 285 (Scheme 5-4). Treatment of α- bromoacetophenones 286 with sodium hydroxide resulted in cyclisation to give the anionic intermediate 287. The epoxide moiety was then formed via an intramolecular nucleophilic substitution mechanism, with the bromine on C3 acting as a leaving group.
‐ 95 ‐
Scheme 5-4: Reagents and conditions: NaOH (aq), MeOH, rt, 1 h.
While 3,4-epoxy benzopyran systems have not been reported in the literature, previous work in our group204 demonstrated the epoxidation of stilbenes 288, which differ from isoflav-3-enes only in the absence of an oxygen atom in ring C. The epoxide species 289 were generated by oxidising stilbenes 288 with meta-chloroperbenzoic acid (mCPBA) or with hydrogen peroxide and manganese sulphate (Scheme 5-5). One aim of the present work is to apply these reaction conditions in the synthesis of novel isoflavene epoxides.
Scheme 5-5: Reagents and conditions: mCPBA, DCM, rt; or H2O2, MnSO4, NaHCO3 (aq), t-BuOH, rt.
5.2 Synthesis of Isoflav-3-ene Epoxides 5.2.1 Synthesis of Epoxides from Isoflavenes In the present study, diacetoxyphenoxodiol 109 was treated with mCPBA in dichloromethane at room temperature to give the isoflavene epoxide 290 in 27% yield after column chromatography (Scheme 5-6). Deacetylation with imidazole in ethanol at reflux afforded the phenolic product 291 in a yield of 92%.
‐ 96 ‐
Scheme 5-6: Reagents and conditions: i) mCPBA, DCM, rt, 24 h; ii) imidazole, EtOH, reflux, 45 min.
The structures of epoxides 290 and 291 were confirmed by 1H NMR spectroscopy. Epoxidation of the C3-C4 double bond led to significant changes in the signals associated with ring C. The H4 singlet shifted upfield from δ 6.76 in the spectrum of isoflavene 111 to δ 3.87 in the spectrum of epoxide 290 in CDCl3. By comparison, the
H4 singlet appeared at δ 5.77 in the spectrum of the phenolic epoxide 291 in d6-DMSO. The presence of the epoxide moiety in compounds 290 and 291 means that the H2 protons are diastereotopic. These protons appeared as overlapping doublets (J = 11.8 Hz) at δ 4.36 and 4.31 in the spectrum of acetylated epoxide 290. In the spectrum of epoxide 291, the H2 protons appeared as doublets (J = 11.6 Hz) at δ 4.50 and 3.96. Additionally, an X-ray crystal structure of acetate epoxide 290 was obtained, proving definitively that the epoxidation of 109 was successful (Figure 5-1).
‐ 97 ‐
Figure 5-1: ORTEP diagram of epoxide 280.
Two more isoflavenes, 292 and 293, were treated with mCPBA in the same manner as diacetoxyphenoxodiol (Scheme 5-7). The acetoxy epoxides 294 and 295 were not isolated from their respective reaction mixtures, but were deprotected in situ to give the phenolic products 296 and 297 in overall yields of 72% and 77%, respectively.
R R R AcO O AcO O HO O
OMe i OMe ii OMe O O OMe OMe OMe 292: R=H 294: R=H 296: R=H 293: R=Me 295: R=Me 297: R=Me Scheme 5-7: Reagents and conditions: i) mCPBA, DCM, rt, 24 h; ii) imidazole, EtOH, reflux, 45 min.
1 The H NMR spectra of epoxides 296 and 296 (acquired in d6-DMSO) were similar to that of epoxide 291. H4 appeared as a broad singlet at δ 5.84 in the spectra of both compound 296 and compound 297. The H2 protons appeared as doublets (J = 11.6 Hz)
‐ 98 ‐ at δ 4.56 and 3.98 in the spectrum of epoxide 296 and at δ 4.59 and 4.08 in the spectrum of epoxide 297.
Epoxidation of isoflavenes was also attempted using other oxidising reagents. Attempted epoxidation of isoflavenes with alkaline hydrogen peroxide, using a method adapted from Lévai et al.,143 resulted in the cleavage of acetate protecting groups, where present, but no epoxide species were obtained. Diacetoxyphenoxodiol 109 was also treated with dimethyldioxirane under the conditions used by Compton and co- workers171 for the epoxidation of acetoxyflavones. However, there was no evidence of epoxide formation and the starting material was recovered from the reaction mixture unchanged.
5.2.2 Synthesis of Epoxides from Isoflavanol Esters It was observed that the treatment of diacetoxyphenoxodiol 109 or dimethoxyphenoxodiol 298 with mCPBA often led to the formation of a product other than the desired epoxide. These side products were identified as the meta- chlorobenzoate esters 299 and 300 (Scheme 5-8). It is believed that these esters were formed as the result of the acid-catalysed ring-opening of the epoxide intermediates 290 and 301, with the benzoate anion attacking the epoxide at the less sterically hindered C4 position.
‐ 99 ‐ RO O RO O
O OR OR H 109: R=Ac 290: R=Ac O 298: R=Me 301: R=Me O
Cl
RO O 2 RO O OH 4 3 O+ O O O O- OR H OR
2" 6"
Cl 5" Cl 4"
299: R=Ac(51%) 300: R = Me (81%)
Scheme 5-8: Reagents and conditions: mCPBA, DCM, rt, 24–72 h.
Isoflavanol esters 299 and 300 were characterised by 1H NMR spectroscopy (Figure 5- 2). Key signals are summarised in Table 5-1. As in the case of the epoxides described above, the H2 protons of esters 299 and 300 were diastereotopic and appeared as doublets at ca. δ 4.3. In contrast, the H4 proton exhibited a significant downfield shift upon ring-opening. In deuterated chloroform, H4 appeared as a broad singlet at δ 6.72 in the spectrum of compound 299, compared with δ 3.87 in the spectrum of epoxide 290.
‐ 100 ‐
1 Figure 5-2: H NMR spectrum of compound 299 in CDCl3
Table 5-1: Characteristic 1H NMR data for isoflavanol esters 299 and 300 (Solvent:
CDCl3). 299 300 δ H2a 4.38 (1H, d, J = 12.0 Hz) 4.36 (1H, d, J = 12.0 Hz) δ H2b 4.30 (1H, d, J = 12.0 Hz) 4.33 (1H, d, J = 12.0 Hz) δ H4 6.72 (1H, br s) 6.72 (1H, br s) δ OH 2.68 (1H, br s) 2.62 (1H, br s) δ H2ʺ 7.97 (1H, dd (app. t) J = 1.7 Hz, 7.92 (1H, dd (app. t) J = 1.7 Hz, 1.8 Hz) 1.8 Hz) δ H4ʺ 7.88 (1H, ddd, J = 1.2 Hz, 1.7 Hz, 7.89 (1H, ddd, J = 1.2 Hz, 1.7 Hz, 7.8 Hz) 7.9 Hz) δ H5ʺ 7.39 (1H, dd (app. t) J = 7.8 Hz, 7.38 (1H, dd (app. t) J = 7.9 Hz, 8.0 Hz) 8.1 Hz) δ H6ʺ 7.54 (1H, ddd, J = 1.2 Hz, 1.8 Hz, 7.54 (1H, ddd, J = 1.2 Hz, 1.8 Hz, 8.0 Hz) 8.1 Hz)
‐ 101 ‐ An X-ray crystal structure was obtained for the diacetoxyisoflavanol ester 299 (Figure 5-2). The X-ray crystallograph confirmed the structure assigned on the basis of 1H NMR spectroscopy.
Figure 5-2: ORTEP diagram of compound 299.
Compounds 299 and 300 were treated with phosphoric acid in toluene at 80 °C in an attempt to generate isoflav-3-enes 302 and 303 via dehydration (Scheme 5-9). Interestingly, the major products of these reactions were determined to be the epoxides 290 and 301. Acid-catalysed cleavage of the meta-chlorobenzoate ester forms the diol species 304 and 305. Protonation of one of the alcohol groups creates an oxonium intermediate, which eliminates water upon cyclisation and formation of a new C-O bond. Subsequent deprotonation affords the epoxides 290 and 301. The dimethoxy epoxide 301 was obtained in 88% yield. The crude acetoxy analogue 290 required purification by column chromatography to remove unreacted starting material, and was obtained in a yield of 31%.
‐ 102 ‐ RO O RO O OH
O O O O OR OR
299: R=Ac 302: R=Ac Cl 300: R=Me Cl 303: R=Me
H+ RO O OH
OH OR 304: R=Ac 305: R=Me
RO O RO O OH -H+ 2 O O OR H OR 290: R=Ac 301: R=Me
Scheme 5-9: Reagents and conditions: H3PO4 (85% in H2O), toluene, 80 °C, 16–24 h.
The structure of epoxide 301 was confirmed by 1H NMR spectroscopy in deuterated chloroform. The diastereotopic H2 protons appeared as doublets (J = 12.5 Hz) at δ 4.56 and 4.46. H4 appeared as a broad singlet at δ 4.66.
5.3 Ring-Opening Reactions on Isoflavene Epoxides The dimethoxy epoxide 301 was treated with various nucleophiles in an attempt to generate the 4-substituted compounds 306–308 (Scheme 5-10). However, the reactions of compound 307 with Grignard reagents, 4-bromophenol and diethylamine resulted in complex mixtures that could not be separated chromatographically. Analysis of the reaction mixtures by TLC indicated that the epoxide starting material was being consumed in each case. This suggests that the desired ring-opening reactions may have occurred but that further optimisation is needed to prevent unwanted side reactions.
‐ 103 ‐
Scheme 5-10: Reagents and conditions: i) R-PhMgBr, THF, 0 °C → rt; ii) 4- bromophenol, THF, 60 °C; iii) diethylamine, DCM, rt.
5.4 Conclusion Five novel isoflavene epoxides were prepared using two synthetic routes: direct oxidation of isoflav-3-enes and an acid-catalysed de-esterification/epoxidation procedure. To our knowledge, this is the first time that the synthesis of 3,4-epoxy isoflavonoid compounds has been reported. While attempts to generate 4-substituted isoflavans via ring-opening reactions were unsuccessful, there is nonetheless some scope to develop this chemistry further.
‐ 104 ‐ CHAPTER SIX
BIOLOGICAL ACTIVITY
6.1 Introduction The biological activity of isoflavonoid compounds has been emphasised throughout this thesis. A number of the compounds synthesised in this project were selected for preliminary screening.
6.2 Anti-inflammatory Activity Inflammation is a physiological response to irritation or injury and an essential part of the body’s healing process. However, excessive or prolonged inflammation is associated with a number of disorders including arthritis, asthma and cardiovascular disease.75-79 The anti-inflammatory properties of isoflavonoid compounds are well documented in the literature.81,82,85,86,88,185,205 It was anticipated that the 2-substituted isoflavenes described in this thesis would also exhibit some degree of anti-inflammatory activity. Fifteen compounds, including thirteen isoflavenes and two isoflavans, were submitted for testing (Figure 6-1). As inflammation is a complex phenomenon involving multiple biochemical pathways, the selected compounds were screened for their ability to inhibit a number of inflammatory mediators.
Figure 6-1: Compounds selected for anti-inflammatory screening.
‐ 105 ‐ 6.2.1 Inhibition of Eicosanoid Synthesis The metabolism of arachidonic acid, a fatty acid released from membrane phospholipids, generates a variety of inflammatory mediators, collectively known as eicosanoids (Figure 6-2). Of particular interest are products of the cyclooxygenase (COX) pathway, namely, prostaglandins and thromboxanes. Many non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen and celecoxib, prevent the release of inflammatory mediators via COX inhibition.77,206-213 COX exists as two isoforms: COX-1, which is constitutively expressed and COX-2, which is induced by inflammatory stimuli. COX-1 is responsible for the synthesis of gastroprotective prostaglandins in the stomach lining. NSAIDs which inhibit COX-1 can cause gastrointestinal irritation, bleeding and ulcers.206-213 On the other hand, the selective inhibition of COX-2 has been associated with an increased risk of serious cardiovascular events, such as myocardial infarction and stroke.214-216 It is therefore desirable to investigate anti-inflammatory mechanisms other than COX inhibition. Overproduction of thromboxane A2 (TXA2) is associated with a number of disease states affecting the lungs, kidneys and cardiovascular system.76,78 It follows, then, that thromboxane synthase (TXS) is potentially a useful biological target.
Arachidonic acid
Lipooxygenases Cyclooxygenases
Hydroperoxyeicosatetraenoic acids Prostaglandin G2 Leukotrienes
Prostaglandin H Isomerases 2 Thromboxane synthase Prostaglandin D2 Prostaglandin E2 Prostacyclin synthase Thromboxane A2 Prostaglandin F2
t1/2 =30s
Prostaglandin I2 (Prostacyclin) Thromboxane B2
Figure 6-2: Metabolism of arachidonic acid.
‐ 106 ‐ The test compounds were examined for their ability to inhibit the synthesis of two eicosanoids, namely prostaglandin E2 (PGE2) and thromboxane B2 (TXB2), in cells undergoing an inflammatory response. Both PGE2 and TXB2 are products of the COX pathway (Figure 6-2). TXB2 is the stable metabolite formed after the non-enzymatic decomposition of TXA2. A decrease in the synthesis of both PGE2 and TXB2 indicates that the test compound possesses COX-inhibitory activity. Selective inhibition of TXB2 suggests that the test compound is acting on TXS.
RAW 264.7 mouse macrophage cells were treated with the test compound (10 μM in 0.025% DMSO) or with vehicle alone. After one hour, the cells were stimulated with 50 ng/mL lipopolysaccharide (LPS) to induce an inflammatory response. The culture media was collected after 24 hours. Levels of PGE2 and TXB2 were measured by
ELISA. The assays were conducted in duplicate. The results for PGE2 and TXB2 inhibition are summarised in Figure 6-3, as well as Tables 6-1 and 6-2.
120.0
100.0
80.0
60.0
40.0
20.0
0.0
-20.0
-40.0 % Change relativeto control
-60.0
-80.0
-100.0
-120.0 134 135 136 138 149 150 164 204 205 263 264 265 266 267 269 Compound PGE2 TXB2 Figure 6-3: Effect of 2-substituted isoflavonoid compounds at 10 μM on the production
of PGE2 and TXBs in RAW 264.7 cells
‐ 107 ‐ Table 6-1: The effect of 2-substituted isoflavonoid compounds on LPS-induced PGE2 production in RAW 264.7 murine macrophages.
%Change relative %Change relative SD SD to control to control 134 –71.5 1.8 205 +53.9 7.2 135 –22.5 2.4 263 –74.1 4.3 136 –52.8 1.0 264 –51.5 1.0 138 –84.9 5.6 265 –39.8 5.6 149 –54.0 2.1 266 –53.7 9.4 150 –60.1 3.0 267 –49.8 0.4 164 –73.2 1.1 269 –21.1 1.6 204 +25.5 3.4
All of the 13 isoflavenes tested inhibited the synthesis of PGE2, while the isoflavans
204 and 205 induced an increase in PGE2 synthesis relative to the experimental control
(Table 6-1). A structure-based pharmacophore model for PGE2 inhibition was developed using Accelrys Discovery Studio software (Figure 6-4). The model indicates that three structural features are important for PGE2 inhibitory activity: two hydrogen bond donors and a hydrophobic moiety two to three bond lengths away from the isoflavene core. As observed in the superimposition of the pharmacophoric model with the most active compound 138 (Figure 6-3), the hydrogen bond donors map to the phenols at positions 7 and 4′, while the hydrophobic region maps to the substituent on C2.
‐ 108 ‐
Figure 6-4: Pharmacophore for PGE2 inhibition superimposed with the most active compound 138.
The majority of the compounds tested exhibited some degree of anti-thrombotic activity, with the exception of analogues 135, 136, 204 and 205 which induced an increased synthesis of TXB2 relative to the experimental control (Table 6-2). The results for 204 and 205 indicate that, as observed in the PGE2 assay, 2-substituted isoflavans are poor anti-inflammatory agents compared to the corresponding isoflavenes. The substitution pattern on ring A of the isoflavene scaffold may also be significant. The 2-methyl isoflavene 134 inihibts TXB2 production, while the dimethyl species 135 and 136 induced an increased synthesis of TXB2.
‐ 109 ‐ Table 6-2: The effect of 2-substituted isoflavonoid compounds on LPS-induced TXB2 production in RAW 264.7 murine macrophages.
%Change relative %Change relative SD SD to control to control 134 –7.4 5.7 205 +91.0 9.4 135 +32.0 10.0 263 –55.6 0.8 136 +25.6 9.2 264 –38.4 6.9 138 –18.3 7.4 265 –28.0 11.8 149 –41.0 1.2 266 –31.2 10.6 150 –39.0 3.9 267 –31.1 5.1 164 –39.2 5.4 269 –25.2 4.9 204 +57.2 8.8
As indicated above, PGE2 and TXB2 are both products of the COX pathway, sharing a common precursor in prostaglandin H2. Most of the compounds tested inhibited PGE2
to a greater extent than TXB2, which suggests that that the compounds acted mainly via the inhibition of COX. The only compound to inhibit TXB2 to a greater extent than
PGE2 was the 2-(4-pyridyl)isoflavene 269, albeit with only a small difference between the two results (–25.2% TXB2 versus –21.1% PGE2). Analogue 269 is the compound that most closely matches the established pharmacophore for TXS inhibition, wherein a basic nitrogen atom is located 8–10 Ǻ from an acidic OH group.78,217 The distance between the pyridyl nitrogen of compound 269 and the 7-OH group was calculated to be 8.8 Ǻ in an energy-minimised model. While this compound possesses only modest anti-inflammatory activity, it may serve as a starting point for future investigations of TXS inhibitors.
6.2.2 Inhibition of Nitric Oxide Synthesis Nitric oxide (NO) is a molecular messenger involved in a number of physiological processes in mammals. NO is synthesised from L-arginine and molecular oxygen by nitric oxide synthase (NOS). Three isoforms of NOS are known: neuronal (nNOS) and endothelial (eNOS), which are constitutively expressed, and inducible (iNOS) which is involved in the inflammatory response. NO production by eNOS is essential to the
‐ 110 ‐ function of the cardiovascular system. However, overproduction of NO by nNOS or iNOS can lead to tissue damage and has been implicated in a number of disease states, such as arthritis, osteoporosis and Alzheimer’s disease.75,79,218 Therefore, compounds that inhibit NO production by iNOS and/or nNOS may have useful therapeutic applications.
RAW 264.7 mouse macrophage cells were treated with the test compound (10 μM in 0.025% DMSO) or vehicle alone. After one hour, the cells were stimulated with 50 ng/mL LPS to induce an inflammatory response. The culture media was collected after 24 hours. Nitrite concentration, determined via the Griess reaction, was used as a quantitative indicator of NO production.218 The assay was performed in duplicate.
134 135 136 138 149 150 164 204 205 263 264 265 266 267 269 60
40
20
0
-20
-40
-60 % Change relative to control -80
-100
-120
-140 Compound
Figure 6-5: Effect of 2-substituted isoflavonoid compounds at 10 μM on the production - of NO2 in RAW 264.7 cells
‐ 111 ‐ Table 6-3: The effect of 2-substituted isoflavonoid compounds on LPS-induced nitric oxide synthesis in RAW 264.7 murine macrophages.
% Change relative % Change relative SD SD to control to control 134 –98.9 8.7 205 +1.2 27.1 135 –7.8 6.4 263 –28.5 33.6 136 –79.5 9.9 264 –0.9 4.5 138 –88.7 11.8 265 –12.5 14.6 149 –94.1 10.2 266 –11.1 46.9 150 –92.5 15.4 267 –1.4 46.9 164 –94.8 33.6 269 –6.9 7.2 204 –1.1 23.2
The test compounds exhibited a range of NO-inhibitory activity (Figure 6-5, Table 6-3). The 2-methyl- and 2-ethyl- substituted isoflavenes 134, 136 and 138 were effective NO inhibitors, as were compounds 149, 150 and 164, which feature an electronegative heteroatom adjacent to C2. Compounds 263–267 and 269, which possess bulky alkyl or aromatic substituents, were less effective NO inhibitors. As in the eicosanoid assays, the isoflavans 204 and 205 performed poorly. Interestingly, compounds 135 and 136, which differ only by the position of a methyl group on Ring A, exhibited markedly different inhibitory activities. At present, the learning set is too small and structurally homogenous to establish the significance of this result. The synthesis and screening of additional analogues (particularly those with different substitution patterns on ring A) may help to illuminate the mechanisms by which these compounds inhibit NO production.
Overall, the 2-substituted isoflavenes described in this section exhibited fairly similar anti-inflammatory activity. For this reason, it was decided that further biological testing of 2-substituted isoflavenes should focus on anti-cancer activity.
‐ 112 ‐ 6.3 Anti-Cancer Activity Both natural and synthetic isoflavonoid compounds have been reported to possess anti- proliferative activity against a variety of cancer types.6-9,52-54,60-65,69,71,72 Notable examples of isoflavonoid anti-cancer drugs include phenoxodiol 14, triphendiol 15 and acolbifene 7. One of the aims of the present work was to reproduce the anti-cancer activity of these compounds by synthesising isoflavene analogues with aromatic substituents at position 2.
Seventeen novel isoflavene analogues were selected for screening against the breast cancer cell line MDA-MB-231, as well as the neuroblastoma cell line SY-SH5Y (Figure 6-4). The cancer cells were seeded at a concentration of 6 × 103 cells per well for MDA- MB-231 and 4 × 104 cells per well for SY-SH5Y. After 24 hours, the cells were exposed to the test compounds at concentrations of 0, 5, 10, 15, 20 and 25 μM. After 96 h incubation, cell viability was measured by addition of a 10× solution of Alamar Blue. Comparative 0 and 5 h values were recorded by measuring the absorbance at 570 nm using a Perkin-Elmer Victor 3 multilabel plate reader. The cell viability of each plate was calculated as a percentage of that for the vehicle only control.
‐ 113 ‐
R1 = 154 172 173 176
NH2
178, 179 181 182 189
190 191 192 193 Et Br Cl O O O
195 197 199 200
HO
Figure 6-6: Compounds selected for anticancer screening.
The test compounds exhibited a range of anti-proliferative activity against MDA-MB- 231 cells (Table 6-4). While most of the compounds were moderately active at best, four compounds were found to have IC50 values of less than 10 μM. Three of these active compounds, analogues 191–193, contained para-substituted acetophenone moieties with an electronegative heteroatom on the phenyl ring The fourth active compound, analogue 199, is a dinitrophenyl hydrazone derived from acetone-substituted
‐ 114 ‐ compound 178. Like compounds 191–193, analogue 199 features a CH2C=X -moiety on the 2-substituent as well as a phenyl ring with electronegative substituents.
The anti-cancer activity of these four compounds could be rationalised by comparison of their structures with the anti-cancer compound triphendiol 15. Using analogue 191 as an example, it can be observed that structures of this type can be readily superimposed onto the structure of triphendiol 15 (Figure 6-7). Key structural features, particularly the 7 and 4′ phenol groups and the methoxy group on the pendant ring, adopt a similar relative configuration in both compound 191 and triphendiol, indicating that the two compounds could interact with similar biological targets.
Table 6-4: IC50 values of 2-substituted isoflavenes against MDA-MB-231 cells.
IC50/μM IC50/μM IC 50/μM 154 > 25 181 16.7 193 6.00 172 17.5 182 12.0 195 > 25 173 19.5 189 16.2 197 > 25 176 21.6 190 20.6 199 7.24 178 > 25 191 3.78 200 > 25 179 > 25 192 3.70
OMe
HO
O OH 15 (yellow) OMe
O
HO O
191 OH
Figure 6-7: Three-dimensional overlay of compound 191 with triphendiol 15.
‐ 115 ‐ The test compounds generally exhibited greater anti-proliferative activity against SH- SY5Y than MDA-MB-231 cells (Table 6-5). As in the previous results, compounds
191–193 were the most active and exhibited IC50 values of less than 2 μM. Six more analogues, compounds 154, 181, 182, 189, 190 and 199, were found to have IC50 values of less than 5 μM. Most of the active compounds have closely related structures. Analogues 182 and 189–193 are all derived from reactions between an isoflavylium salt and acetophenones, differing only in the substituent at the para-position of the pendant phenyl ring. Interestingly, compound 200, an acetophenone derivative in which the carbonyl group was reduced to a hydroxyl, displayed very low activity against both cell lines tested, while the parent isoflavene 182 was moderately active against MDA-MB- 231 and was one of the most active analogues against SH-SY5Y cells. This suggests that some degree of rigidity may be required in the 2-substituent in order to maintain the optimal orientation of key structural features. The potent anti-proliferative activities exhibited by compound 195, prepared from 1-acetylnaphthalene, and the hydrazone 199 suggests that the CH2COPh moiety may not be essential for anti-proliferative activity against SH-SY5Y. Indeed, compounds 154 and 181 were both determined to have IC50 values of less than 5 μM despite the fact that compound 154 lacks a carbonyl group while compound 181 does not possess an aromatic substituent on C2.
Table 6-5: IC50 values of 2-substituted isoflavenes against SH-SY5Y cells.
IC50/μM IC50/μM IC50/μM 154 4.97 181 2.49 193 1.73 172 11.4 182 2.14 195 6.47 173 5.09 189 3.71 197 > 25 176 7.78 190 3.26 199 2.52 178 6.68 191 1.46 200 > 25 179 24.5 192 1.30
In order to assess the therapeutic potential of these novel isoflavenes, it is instructive to compare the IC50 values of the isoflavenes in the present work with the corresponding data for those compounds that are currently used to treat breast cancer and neuroblastoma in a clinical setting. Compound 192 was the most active isoflavene analogue against MDA-MB-231, with an IC50 value of 3.70 μM. This means that
‐ 116 ‐ compound 192 is approximately 1000 times less potent against this cell line than the 219 220 220 drugs vinblastine, paclitaxel and docetaxel, which have IC50 values of 2.3 nM, 2.4 nM and 0.8 nM, respectively. The results for the neuroblastoma cell line were more encouraging. Analogue 192 has an IC50 value of 1.30 μM against SH-SY5Y, which is comparable to the values reported for cisplatin (1.1 μM), irinocetan (1.4 μM) and vincristine (0.54 μM).221
6.4 Conclusion Many of the isoflavene analogues generated throughout this thesis exhibited promising activity in the selected biological assays. The results of the anti-inflammatory assays highlight the ability of 2-substituted isoflavenes to inhibit both eicosanoid production and the synthesis of nitric oxide. As predicted in Chapter 1, isoflavenes with aromatic substituents at C2 also exhibited significant anti-cancer activity.
While the preliminary results reported here are encouraging, further research is required to develop these novel compounds for pharmaceutical applications. The synthesis and screening of additional analogues, particularly those with alternative substitution patterns about rings A and B, would establish a more robust learning set for the analysis of structure-activity relationships. Future work should also include a comprehensive evaluation of the compounds’ toxicity against normal cells, as well as pharmacokinetic investigations. Additionally, as the compounds described here were screened as racemic mixtures, it will eventually be necessary to separate and/or selectively synthesise the enantiomers of lead analogues in order to investigate their activity and toxicity profiles separately.
‐ 117 ‐ CHAPTER SEVEN
CONCLUSIONS AND FUTURE WORK
It has been demonstrated in this thesis that isoflavylium salts can be readily obtained from the corresponding isoflavenes in good to excellent yields. Five of these salts described in the present work were entirely novel, while one had been previously reported only as a reaction intermediate.163,164 Hydride abstraction with tritylium hexafluorophosphate was used to generate salts from isoflavenes with a variety of substitution patterns on ring A. While it has been suggested previously that phenolic isoflavenes must be protected before undergoing hydride abstraction, the reaction was also performed on a phenolic isoflavene to generate the corresponding isoflavylium salt in good yield. There is potential to apply this methodology to a greater variety of isoflavene starting materials than those described in this thesis. Isoflavylium salts were also prepared via an alternative strategy, proceeding via a 2-hydroxyisoflavene intermediate. This route may provide access to isoflavylium salts which cannot be generated via the hydride abstraction method.
Isoflavylium salts have previously been shown to react with a variety of nucleophiles, such as amines,180 thiols,162 alcohols and trimethylsilanes,163,164 to generate 2-substituted isoflavenes. In the present work, the scope of this methodology has been expanded considerably, resulting in the synthesis of more than 30 novel isoflavenes. These compounds included new examples of alcohol, thiol and amine derivatives, as well as new classes of products such as isoflavene-indole adducts and carbonyl compounds derived from reactions with α-methyl ketones. The introduction of a carbonyl moiety to the isoflavene scaffold provides a starting point for further structural modification. Some simple examples, namely hydrozone formation and reduction of the ketone to an alcohol, were reported in this thesis. Other reactions, such as reductive amination or Grignard addition, could be explored as part of future work. The formation of 4- substituted isoflav-2-enes such as compound 145 also warrants further investigation.
Twelve 2-substituted isoflavones, ten of them novel, were prepared via the cyclisation of deoxybenzoins. Six of these analogues were converted to 2-substituted isoflavenes
‐ 118 ‐ via reduction and subsequent dehydration of the corresponding isoflavanols. It was also demonstrated that 2-substituted isoflavones can be partially reduced to generate the corresponding isoflavanones. Three of the four isoflavanones prepared in this manner had not been reported previously. These isoflavanones could be treated with Grignard reagents to generate 2,4-disubstituted species. There is also potential to perform further chemistry on 2-substituted isoflavanols generated as part of the isoflavene synthesis. For example, it has been demonstrated previously168 that isoflavanols can be treated with Lewis acid and nucleophiles to generate 4-substituted isoflavans. The isoflavans thus obtained have trans geometry about the C3-C4 bond. It may be interesting to compare these compound with the cis substituted products synthesised via the Grignard route.
While 2,3-epoxy isoflavones are known in the literature,141,143,199,202 the five novel isoflavene epoxides described in this thesis are, to our knowledge, the first reported examples of 3,4-epoxy isoflavonoid compounds. Two novel isoflavanol meta- chlorobenzoate esters were also isolated and fully characterised. While attempts to ring- open the epoxides with nucleophiles were unsuccessful, there is nonetheless some scope to develop this chemistry as a route to 4-substituted isoflavonoid species. Future work could also be directed towards stereoselective epoxidation, which may form part of a stereocontrolled synthesis of 4-substituted isoflavans.
Many of the isoflavene analogues reported in this these exhibited promising biological activity in anti-inflammatory and anti-cancer assays. A number of 2-substituted isoflavenes were shown to inhibit both eicosanoid production and the synthesis of nitric oxide. Other analogues, particularly those with aromatic substituents at C2, exhibited significant anti-proliferative activity against MDA-MB-231 and SH-SY5Y cells. Analysis of structure activity relationships has been limited by the small size of the learning set. Future work should be directed towards the expansion of the learning set via the synthesis and screening of additional analogues. The toxicity of these compounds towards normal cells should also be investigated, along with pharmacokinetic properties. As the 2-substituted isoflavenes were screened as racemic mixtures, the activity of pure enantiomers of lead analogues should also be investigated.
‐ 119 ‐ CHAPTER EIGHT
EXPERIMENTAL
8.1. General Information 1H and 13C NMR spectra were obtained in the designated solvents on a Bruker DPX 300 spectrometer. Chemical shifts (δ) are in parts per million and internally referenced relative to the solvent nuclei. Multiplicities are assigned as singlet (s), doublet (d), doublet of doublet (dd), doublet of triplet (dt), triplet (t), quartet (q), multiplet (m), broad doublet (br d) and broad singlet (br s) where appropriate and the observed coupling constants (J) are described in Hertz.
Melting points were measured using a Mel-Temp melting point apparatus and are uncorrected. Infrared spectra were recorded on a Thermo Nicolet Avatar Series FTIR spectrophotometer as KBr disks. Peak intensties are labelled as strong (s), medium (m) or weak (w). Ultraviolet spectra were measured using a Varian Cary 100 spectrophotometer in the designated solvents and data reported as wavelength (λ) in nm and adsorption coefficient (ε) in cm-1M-1.
High-resolution [+ESI] mass spectra were recorded by the Bioanalytical Mass Spectrometry Facility, UNSW on an Orbitrap LTQ XL ion trap mass spectrometer using a nanospray (nano-electrospray) ionization source.
Ajax Finechem Silica 200-325 mesh was used for column chromatography and Merck silica gel 60H was used for flash chromatography. 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. Reverse-phase HPLC was carried out on an Agilent HP 1100 semi-preparative system.
Commercially available reagents were purchased from Fluka, Aldrich, Acros Organics, Alfa Aesar and Lancaster and used without further purification. All reactions requiring anhydrous conditions were performed under a nitrogen atmosphere. Anhydrous solvents were obtained using a PureSolv MD Solvent Purification System. The isoflavenes 14,
‐ 120 ‐ 111, 112 and 120 were obtained from Novogen, Sydney and used without further purification. Isoflavenes 293 and 294 are known compounds which were prepared according to literature methods136.
‐ 121 ‐ 8.2 Experimental Details 4-(7-Acetoxy-2H-chromen-3-yl)phenyl acetate (109) Phenoxodiol 14 (20.69 g, 86.12 mmol) and potassium 8 AcO O 2 carbonate (22.32 g, 161.5 mmol) were dissolved in 2' 6 3' acetone (200 mL). Acetic anhydride (32 mL, 340 5 4 6' OAc mmol) was added. The mixture was heated at reflux for 5' 90 minutes. The cooled reaction mixture was poured into water (600 mL). The precipitate was collected to give the title compound 109 (27.67 g, 99%) as a white 163 1 powder. M.p. 184–187 °C. Lit M.p 177–178 °C H NMR (300 MHz, CDCl3): δ 7.42 (2H, d, J = 8.8 Hz, H2′,6′), 7.12 (2H, d, J = 8.8 Hz, H3′,5′), 7.06 (1H, d, J = 8.1 Hz, H5), 6.76 (1H, br s, H4), 6.65 (1H, dd, J = 2.3 Hz, 8.1 Hz, H6), 6.61 (1H, d, J = 2.3 Hz, H8),
5.15 (2H, d, J = 1.4 Hz, H2), 2.31 (3H, s, COCH3), 2.29 (3H, s, COCH3).
7-Acetoxy-3-(4-acetoxyphenyl)chromenylium - 8 PF6 AcO O+ hexafluorophosphate(V) (55) 2 2' Diacetoxyphenoxodiol 109 (5.01 g, 15.4 mmol) and 6 3' 5 4 tritylium hexafluorophosphate (6.57 g, 16.9 mmol) 6' OAc 5' were dissolved in dichloromethane (250 mL). The mixture was stirred at room temperature for 45 minutes, under nitrogen. Filtration afforded the title compound 55 (6.53 g, 91%) as a bright yellow powder. M.p. 124–126 °C. 1H NMR (300 MHz, d- TFA): δ 9.92 (1H, d, J = 2.0 Hz, H2), 9.84 (1H, d, J = 2.0 Hz, H4), 8.59 (1H, d, J = 9.3 Hz, H5), 8.42 (1H, d, J = 1.8 Hz, H8), 8.01 (1H, dd, J = 1.8 Hz, 9.3 Hz, H6), 7.86 (2H, d, J = 8.4 Hz, H2′,6′), 7.46 (2H, d, J = 8.4 Hz, H3′,5′), 2.57 (3H, s, COCH3), 2.49 (3H, s, 13 COCH3). C NMR (75 MHz, d-TFA): δ 177.4 (CO or ArC), 173.9 (CO or ArC), 173.4 (CO or ArC), 168.7 (C2), 159.1 (C4), 156.2 (ArC), 136.1 (ArC), 135.3 (ArC), 133.4 (ArC), 131.2 (ArC), 127.3 (ArC), 125.8 (ArC), 115.4 (ArC), 114.1 (ArC) 104.8 (ArC),
21.8 (COCH3), 21.6 (COCH3). IR (KBr): νmax 3435 (m), 3128 (w), 1778 (m), 1753 (s), 1625 (s), 1589 (w), 1505 (m), 1434 (w), 1369 (m), 1308 (w), 1289 (w), 1276 (w), 1244 (m), 1206 (s), 1174 (s), 1111 (m), 1007 (m), 942 (w), 917 (w), 896 (w), 839 (s) cm-1. -1 -1 UV-vis (CH3CN): λmax 318 nm (ε 6,954 cm M ), 206 (8,558). HRMS (+ESI): Found + m/z 323.0914, [M] ; C19H15O5 required 323.0914.
‐ 122 ‐ 7-Acetoxy-3-(4-acetoxyphenyl)-8-methylchromenylium hexafluorophosphate(V) (113)
8-Methyldiacetoxyphenoxodiol 111 (203 mg, 0.600 - + PF6 AcO O 2 mmol) and tritylium hexafluorophosphate (313 g, 2' 6 3' 0.806 mmol) were dissolved in dichloromethane (10 5 4 6' OAc mL). The mixture was stirred at room temperature for 5' one hour, under nitrogen. Filtration afforded the title compound 113 (237 mg, 82%) as a bright yellow powder. M.p. 120–122 °C. 1H NMR (300 MHz, d-TFA): δ 10.05 (1H, d, J = 2.4 Hz, H2), 9.89 (1H, d, J = 2.4 Hz, H4), 8.47 (1H, d, J = 8.9 Hz, H5), 8.07 (1H, d, J = 8.9 Hz, H6), 7.93 (2H, d, J = 9.0 Hz, H2′,6′), 7.52 (2H, d, J = 9.0 Hz, H3′,5′), 2.83 13 (3H, s, 8-CH3), 2.67 (3H, s, COCH3), 2.55 (3H, s, COCH3). C NMR (75 MHz, d- TFA): δ 177.3 (CO or ArC), 174.1 (CO or ArC), 168.5 (CO or ArC), 161.7 (CO or ArC), 159.4 (ArC), 155.2 (ArC), 144.4 (ArC), 136.9 (ArC), 132.5 (ArC), 132.1 (ArC), 130.4
(ArC), 125.4 (ArC), 117.8 (ArC), 115.5 (ArC), 114.1 (ArC), 21.6 (COCH3), 21.3
(COCH3), 9.8 (CH3). IR (KBr): νmax 3422 (m), 2918 (w), 1762 (m), 1670 (w), 1648 (m), 1654 (m), 1637 (m), 1629 (s), 1509 (w), 1211 (s), 1165 (s), 1092 (s), 1003 (s), 844 (m) -1 -1 -1 cm . UV-vis (CH3CN): λmax 321 nm (ε 5,354 cm M ). HRMS (+ESI): Found m/z + 337.1063, [M] ; C20H17O5 required 337.1071.
7-Acetoxy-3-(4-acetoxyphenyl)-5-methylchromenylium hexafluorophosphate(V) (114)
5-Methyldiacetoxyphenoxodiol 112 (206 mg, 0.609 PF - 8 + 6 AcO O 2 mmol) and tritylium hexafluorophosphate (317 mg, 2' 6 3' 0.816 mmol) were dissolved in dichloromethane (10 4 6' OAc mL). The mixture was stirred at room temperature for 5' one hour, under nitrogen. Filtration afforded the title compound 114 (210 mg, 74%) as a bright yellow powder. M.p. 118–120 °C. 1H NMR (300 MHz, d-TFA): δ 9.91 (1H, d, J = 2.1 Hz, H2), 9.87 (1H, d, J = 2.1 Hz, H4), 8.26 (1H, d, J = 1.5 Hz, H8), 7.87 (2H, d, J = 8.7 Hz, H2′,6′), 7.84 (1H, d, J = 1.5 Hz, H6), 7.48 (2H, d, J = 8.7 Hz, H3′,5′), 3.04 13 (3H, s, 5-CH3), 2.58 (3H, s, COCH3), 2.52 (3H, s, COCH3). C NMR (75 MHz, d- TFA): δ 167.7 (CO or ArC), 162.3 (CO or ArC), 155.7 (ArC), 155.0 (ArC), 146.3 (ArC), 136.3 (ArC), 131.3 (ArC), 130.7 (ArC), 129.6 (ArC), 125.7 (ArC), 119.2 (ArC), 117.8
(ArC), 115.4 (ArC), 114.0 (ArC), 111.3 (ArC), 21.8 (COCH3), 21.6 (COCH3), 18.8
(CH3). IR (KBr): νmax 3448 (m), 2927 (w), 1762 (w), 1757 (m), 1701 (w), 1686 (w),
‐ 123 ‐ 1655 (s), 1647 (m), 1637 (s), 1629 (s), 1618 (m), 1560 (m), 1508 (m), 1206 (s), 1170 (s), -1 - 1124 (s), 1014 (m), 914 (w), 842 (s) cm . UV-vis (CH3CN): λmax 321 nm (ε 6,196 cm 1 -1 + M ). HRMS (+ESI): Found m/z 337.1062, [M] ; C20H17O5 required 337.1071.
7-Hydroxy-3-(4-hydroxyphenyl)chromenylium hexafluorophosphate(V) (117) Phenoxodiol 14 (1.02 g, 4.25 mmol) and tritylium PF - 8 + 6 hexfluorophosphate (2.07 g, 5.33 mmol) were HO O 2 2' suspended in dry dichloromethane (80 mL). The mixture 6 3' 5 4 was stirred at room temperature for two hours, under 6' OH 5' nitrogen. Filtration afforded the title compound 117 (1.13 g, 69%) as a bright red powder. M.p. 126–129 °C. 1H NMR (300 MHz, d-TFA): δ 9.46 (1H, d, J = 2.1 Hz, H4), 9.44 (1H, d, J = 2.1 Hz, H2), 8.35 (1H, d, J = 9.3 Hz, H5), 7.78 (1H, dd, J = 2.1 Hz, 9.3 Hz, H6), 7.71–7.68 (3H, m, H8, H2′,6′), 7.29 (2H, d, J = 8.7 Hz, H3′,5′). 13C NMR (75 MHz, d-TFA): δ 173.3 (ArC), 163.0 (ArC), 158.5 (ArC), 155.9 (ArC), 135.8 (ArC), 130.9 (ArC), 127.1 (ArC), 126.1 (ArC), 124.9 (ArC), 119.3 (ArC), 117.8 (ArC), 115.4
(ArC), 104.7 (ArC). IR (KBr): νmax 3650 (m), 3546 (s), 3441 (w), 3053 (w), 2849 (w), 1634 (s), 1592 (m), 1567 (w), 1514 (s), 1478 (s), 1441 (w), 1406 (w), 1375 (m), 1330 (s), 1287 (m), 1255 (w), 1229 (m), 1203 (m), 1180 (s), 1158 (w), 1119 (s), 1083 (m), -1 -1 -1 961 (w), 939 (w), 838 (s) cm . UV-vis (CH3CN): λmax 445 nm (ε 1,402 cm M ), 323 + (24,032), 210 (24,070). HRMS (+ESI): Found m/z 239.0698, [M] ; C15H11O3 required 239.0703.
7-Hydroxy-3-(4-hydroxyphenyl)chromenylium chloride (119) - Phenoxodiol 14 (2.17 g, 9.03 mmol), was suspended in 8 + Cl HO O 2 trifluoroacetic acid (40 mL) and stirred at room 2' 6 3' temperature for ten minutes. Thallic trifluoroacetate (4.63 5 4 6' OH g, 8.52 mmol) was added and the mixture was stirred at 5' room temperature for a further 30 minutes. Water (60 mL) was added and the mixture was extracted with ethyl acetate (2 × 100 mL). The combined extracts were neutralised by washing with saturated NaHCO3 solution, dried over MgSO4 and evaporated in vacuuo to a total volume of approximately 60 mL. To this solution 36% HCl (40 mL) was added slowly, resulting in the formation of a precipitate. Filtration afforded the title compound 119 (1.61 g, 65%) as a reddish-purple solid. M.p. 144–146 °C (decomp.). 1H NMR (300 MHz, d-TFA): δ 9.46 (1H, d, J = 2.1 Hz, H4), 9.44 (1H, d, J = 2.1 Hz, H2),
‐ 124 ‐ 8.35 (1H, d, J = 9.3 Hz, H5), 7.78 (1H, dd, J = 2.1 Hz, 9.3 Hz, H6), 7.71–7.68 (3H, m, H8, H2′,6′), 7.29 (2H, d, J = 8.7 Hz, H3′,5′). 13C NMR (75 MHz, d-TFA): δ 173.3 (ArC), 163.0 (ArC), 158.5 (ArC), 155.9 (ArC), 135.8 (ArC), 130.9 (ArC), 127.1 (ArC), 126.1 (ArC), 124.9 (ArC), 119.3 (ArC), 117.8 (ArC), 115.4 (ArC), 104.7 (ArC). IR (KBr):
νmax 3570, 3408 (s), 2597 (w), 1631 (s), 1610 (s), 1589 (s), 1511 (s), 1479 (m), 1460 (w), 1443 (m), 1398 (w), 1373 (m), 1342 (m), 1312 (s), 1272 (s), 1228 (m), 1199 (m), -1 - 1180 (s), 1155 (w), 1115 (m), 837 (m) cm . UV-vis (CH3CN): λmax 486 nm (ε 858 cm 1 -1 + M ) 322 (22,751), 209 (25,547). HRMS (+ESI): Found m/z 239.0698, [M] ; C15H11O3 required 239.0703.
7-Hydroxy-3-(4-hydroxyphenyl)-4-(4-methoxyphenyl)chromenylium chloride (121) Cl- 7,4ʹ-di(tert-butyldimethylsilyl)oxy-4-(4-methoxyphenyl)- 8 + HO O 2 phenoxodiol 120 (1.02 g, 1.77 mmol), was suspended in 2' 6 3' 5 trifluoroacetic acid (40 mL) and stirred at room 6' 6'' 2'' OH temperature for ten minutes. Thallic trifluoroacetate (1.43 5' 5'' 3'' g, 2.63 mmol) was added and the mixture was stirred at OMe room temperature for a further 30 minutes. Water (60 mL) was added and the mixture was extracted with ethyl acetate (3 × 50 mL). The combined extracts were neutralised by washing with saturated NaHCO3 solution, dried over
MgSO4 and evaporated in vacuuo to give a dark red oil, with was redissolved in ethyl acetate (40 mL). To this solution 36% HCl (10 mL) was added slowly, resulting in the formation of a precipitate. Filtration afforded the title compound 121 (337 mg, 50%) as a dark red solid. M.p. 179–181 °C (decomp.). 1H NMR (300 MHz, d-TFA): δ 9.02 (1H, br s, H4), 9.44 (1H, d, J = 2.1 Hz, H2), 8.18 (1H, d, J = 9.3 Hz, H5), 7.78 (1H, dd, J = 2.1 Hz, 9.3 Hz, H6), 7.64 (1H, d, J = 1.8 Hz, H8), 7.33 (2H, d, J = 8.7 Hz, H2″,6″) 7.16–7.01 (8H, m, ArH), 4.01 (3H, br s, OMe). 13C NMR (75 MHz, d-TFA): δ 180.1 (ArC), 171.4 (ArC), 170.8 (ArC), 164.7 (ArC), 162.8 (ArC), 157.4 (ArC), 135.3 (ArC), 135.0 (ArC), 133.9 (ArC), 126.4 (ArC), 125.7 (ArC), 122.9 (ArC), 119.2 (ArC), 117.8
(ArC), 116.9 (ArC), 114.1 (ArC), 105.1 (ArC), 57.2 (OMe). IR (KBr): νmax 3136 (s), 2837 (w), 2687 (w), 2560 (m), 1796 (w), 1606 (s), 1510 (s), 1462 (m), 1462 (w), 1429 (w), 1416 (m), 1382 (s), 1332 (m), 1288 (s), 1227 (m), 1258 (s), 1176 (s), 1112 (m), -1 -1 -1 1062 (w), 1026 (m), 834 (m) cm . UV-vis (CH3CN): λmax 312 nm (ε 10,463 cm M ), + 201 (33,512). HRMS (+ESI): Found m/z 345.1117, [M] ; C22H17O4 required 345.1121.
‐ 125 ‐ 4-(7-Acetoxy-2-methyl-2H-chromen-3-yl)phenyl acetate (131)
8 Diacetoxyphenoxodiol 109 (1.00 g, 3.08 mmol) and AcO O 2 tritylium hexafluorophosphate (1.42 g, 3.66 mmol) 3 2' 6 3' were dissolved in dichloromethane (100 mL). The 5 4 6' OAc mixture was stirred at room temperature for one hour. 5' Filtration afforded the isoflavylium salt 55 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Dimethyl zinc solution (1.0 M in heptane, 4.0 mL, 4.0 mmol) was added slowly at 0 °C, under an atmosphere of nitrogen. The mixture was stirred at room temperature for 18 hours before being quenched with saturated NH4Cl solution. The dichloromethane layer was collected, washed with water (2 × 50 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 131 (0.74 g, 71%) as a pale green solid. M.p. 177–178 193 1 °C, Lit 112-115 °C. H NMR (300 MHz, CDCl3) δ 7.47 (2H, d, J = 8.6 Hz, H2′,6′), 7.12 (2H, d, J = 8.6 Hz, H3′,5′), 7.07 (1H, d, J = 7.9 Hz, H5), 6.70–6.63 (3H, m, H4, H6,
H8), 5.45 (1H, q, J = 6.5 Hz, H2), 2.31 (3H, s, COCH3), 2.29 (3H, s, COCH3), 1.39 (3H, d, J = 6.5 Hz, CH3).
4-(7-Acetoxy-2,8-dimethyl-2H-chromen-3-yl)phenyl acetate (132) AcO O 2 8-Methyldiacetoxyphenoxodiol 111 (1.07 g, 3.16 mmol) 3 2' 6 3' and tritylium hexafluorophosphate (1.33 g, 3.43 mmol) 5 4 6' OAc were dissolved in dichloromethane (100 mL). The 5' mixture was stirred at room temperature for one hour, under nitrogen. Filtration afforded the isoflavylium salt 113 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Dimethylzinc solution (1.0 M in heptane, 4.0 mL, 4.0 mmol) was added slowly at 0 °C, under an atmosphere of nitrogen. The mixture was stirred at room temperature for 18 hours before being quenched with saturated NH4Cl solution. The dichloromethane layer was collected, washed with water
(2 × 50 mL) and dried over MgSO4. The solvent was evaporated in vacuo and the crude product recrystallised from ethyl acetate to give the title compound 132 (0.24 g, 21%) as 1 small, off-white crystals. M.p. 104-108 °C. H NMR (300 MHz, CDCl3) δ 7.47 (2H, d, J = 8.8 Hz, H2′,6′), 7.11 (2H, d, J = 8.8 Hz, H3′,5′), 6.94 (lH, d, J = 8.1 Hz, H5), 6.69 (1H, br s, H4), 6.61 (1H, d, J = 8.1 Hz, H6), 5.51 (lH, q, J = 6.6 Hz, H2), 2.32 (3H, s,
COCH3), 2.31 (3H, s, acetate CH3), 2.05 (3H, s, 8-CH3), 1.38 (3H, d, J = 6.6 Hz, 2-
‐ 126 ‐ 13 CH3). C NMR (75 MHz, d6-DMSO): δ 169.1 (CO), 168.9 (CO), 150.1 (ArC), 149.5 (ArC), 149.5 (ArC), 134.5 (ArC), 133.3 (ArC), 126.2 (ArC), 124.4 (ArC), 122.2 (ArC),
119.7 (ArC), 118.2 (ArC), 117.9 (ArC), 114.8 (ArC), 71.6 (C2), 20.8 (COCH3), 20.5
(COCH3), 19.4 (CH3), 8.8 (CH3). IR (KBr): νmax 3425 (m), 2977 (w), 2919 (w), 1754 (s), 1629 (w), 1602 (m), 1510 (m), 1483 (w), 1434 (w), 1365 (m), 1279 (w), 1230 (s), 1198 (s), 1173 (m), 1156 (w), 1113 (w), 1090 (m), 1071 (m), 1015 (w), 939 (w), 907 -1 -1 -1 (m), 848 (m) cm . UV-vis (MeOH): λmax 329 nm (ε 14,482 cm M ), 297 (13,543), 244 + (15,880), 209 (23,046). HRMS (+ESI): Found m/z 353.1376, [M+H] ; C21H21O5 required 353.1384.
4-(7-Acetoxy-2,5-dimethyl-2H-chromen-3-yl)phenyl acetate (133)
8 5-Methyldiacetoxyphenoxodiol 112 (510 mg, 1.51 AcO O 2 mmol) and tritylium hexafluorophosphate (670 mg, 3 2' 6 3' 1.73 mmol) were dissolved in dichloromethane (50 4 6' OAc mL). The mixture was stirred at room temperature for 5' one hour. Filtration afforded the isoflavylium salt 114 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (50 mL). Dimethylzinc solution (1.0 M in heptane, 2.0 mL, 2.0 mmol) was added slowly at 0 °C, under an atmosphere of nitrogen. The mixture was stirred at room temperature for 18 hours before being quenched with saturated NH4Cl solution. The dichloromethane layer was collected, washed with water (2 × 50 mL) and dried over MgSO4. The solvent was evaporated in vacuo and the crude product recrystallised from ethyl acetate to give the title compound 133 (138 mg, 26%) as small, beige crystals. M.p. 147–151 °C. 1H NMR (300 MHz,
CDCl3) δ 7.48 (2H, d, J = 8.8 Hz, H2′,6′), 7.12 (2H, d, J = 8.8 Hz, H3′,5′), 6.82 (1H, br s, H4), 6.52 (1H, d, J = 2.2 Hz, H6), 6.50 (1H, d, J = 2.2 Hz, H8), 5.41 (1H, q, J = 6.6
Hz, H2), 2.36 (3H, s, 5-CH3), 2.32 (3H, s, COCH3), 2.27 (3H, s, COCH3), 1.38 (3H, d, 13 J = 6.6 Hz, 2-CH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.4 (CO), 152.3 (ArC), 150.6 (ArC), 150.3 (ArC), 135.3 (ArC), 134.9 (ArC), 126.4 (ArC), 121.9 (ArC),
118.9 (ArC), 116.1 (ArC), 115.9 (ArC), 108.0 (ArC), 72.5 (C2), 21.2 (COCH3), 19.4
(CH3), 18.7 (CH3). IR (KBr): νmax 3439 (m), 2971 (w), 2924 (w), 1755 (s), 1634 (w), 1602 (w), 1589 (w), 1509 (m), 1479 (w), 1449 (w), 1426 (w), 1368 (m), 1319 (w), 1292 (w), 1208 (s), 1191 (s), 1168 (s), 1125 (s), 1072 (m), 1011 (m), 906 (m), 889 (m), 847 -1 -1 -1 (w) cm . UV-vis (MeOH): λmax 333 nm (ε 12, 157 cm M ), 308 (15,691), 242
‐ 127 ‐ + (17,651), 210 (22,231). HRMS (+ESI): Found m/z 353.1378, [M+H] ; C21H21O5 required 353.1384. 3-(4-Hydroxyphenyl)-2-methyl-2H-chromen-7-ol (134)157
8 The isoflavene 131 (122 mg, 0.361 mmol) was suspended HO O 2 in methanol (5 mL). Aqueous KOH (1 M, 0.7 mL, 0.7 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 5 4 6' OH room temperature for 1 hour before being neutralised 5' with 1 M acetic acid and diluted to 20 mL with water. Filtration afforded the title compound 134 (62 mg, 68%) as a pale green solid. M.p. 228–230 °C. 1H NMR (300
MHz, d6-DMSO): δ 9.56 (1H, br s, OH), 9.50 (1H, br s, OH), 7.39 (2H, d, J = 8.7 Hz, H2′,6′), 6.95 (1H, d, J = 8.2 Hz, H5), 6.77 (2H, d, J = 8.7 Hz, H3′,5′), 6.71 (1H, br s, H4), 6.32 (1H, dd, J = 2.4 Hz, 8.2 Hz, H6), 6.24 (1H, d, J = 2.4 Hz, H8), 5.43 (1H, q, J
= 6.5 Hz, H2), 1.23 (3H, d, J = 6.5 Hz, CH3).
3-(4-Hydroxyphenyl)-2,8-dimethyl-2H-chromen-7-ol (135) The isoflavene 132 (67 mg, 0.19 mmol) was suspended HO O 2 in methanol (3 mL). Aqueous KOH (1 M, 1.0 mL, 1.0 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 5 4 6' OH room temperature for one hour before being neutralised 5' with 1 M acetic acid and diluted to 20 mL with water. Filtration afforded the title compound 135 (41 mg, 80%) as a red-brown solid. M.p. 158–163 °C. 1H NMR (300
MHz, d6-DMSO): δ 9.57 (1H, br s, OH), 9.41 (1H, br s, OH), 7.37 (2H, d, J = 8.8 Hz, H2′,6′), 6.81–6.72 (3H, m, H5, H3′,5′), 6.70 (1H, br s, H4), 6.38 (1H, d, J = 8.1 Hz, H6), 13 5.50 (1H, q, J = 6.2 Hz, H2), 1.97 (3H, s, 8-CH3), 1.21 (3H, d, J = 6.2 Hz, 2-CH3). C
NMR (75 MHz, d6-DMSO): δ 158.2 (ArC), 157.3 (ArC), 153.9 (ArC), 136.8 (ArC), 133.1 (ArC), 128.0 (ArC), 126.2 (ArC), 116.5 (ArC), 114.1 (ArC), 112.2 (ArC), 108.1
(ArC), 100.2 (ArC), 71.0 (C2), 19.0 (CH3), 8.7 (CH3). IR (KBr): νmax 3384 (m), 2963 (m), 1736 (w), 1655 (w), 1648 (w), 1608 (m), 1514 (m), 1459 (w), 1439 (m), 1367 (w), 1262 (s), 1223 (m), 1168 (m), 1090 (s), 1023 (s), 865 (w), 801 (s) cm-1. UV-vis (MeOH): -1 -1 λmax 329 nm (ε 9,670 cm M ), 283 (13,762), 203 (31,681). HRMS (+ESI): Found m/z + 269.1167, [M+H] ; C17H17O3 required 269.1172.
‐ 128 ‐ 3-(4-Hydroxyphenyl)-2,5-dimethyl-2H-chromen-7-ol (136)
8 The isoflavene 133 (111 mg, 0.315 mmol) was suspended HO O 2 in methanol (6 mL). Aqueous KOH (1 M, 0.8 mL, 0.8 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 4 6' OH room temperature for 90 minutes before being neutralised 5' with 1 M acetic acid and diluted to 20 mL with water. Filtration afforded the title compound 136 (45 mg, 53%) as a brown solid. M.p. 225–229 °C. 1H NMR (300 MHz, d6-DMSO): δ 9.56 (1H, br s, OH), 9.41 (1H, br s, OH), 7.40 (2H, d, J = 8.4 Hz, H2′,6′), 6.79–6.76 (3H, m, H4, H3′,5′), 6.19 (1H, d, J = 2.2 Hz, H6), 6.10 (1H, d, J = 2.2 Hz,
H8), 5.38 (1H, q, J = 6.6 Hz, H2), 2.25 (3H, s, 5-CH3), 1.22 (3H, d, J = 6.6 Hz, 2-CH3). 13 C NMR (75 MHz, d6-DMSO): δ 157.5 (ArC), 156.9 (ArC), 151.9 (ArC), 134.9 (ArC), 132.0 (ArC), 127.5 (ArC), 126.0 (ArC), 115.5 (ArC), 113.1 (ArC), 112.8 (ArC), 110.1
(ArC), 101.1 (ArC), 71.0 (C2), 18.9 (CH3), 18.4 (CH3). IR (KBr): νmax 3352 (s), 2968 (m), 2923 (w), 1611 (s), 1594 (s), 1514 (s), 1503 (m), 1468 (m), 1434 (m), 1365 (m), 1303 (s), 1249 (s), 1224 (s), 1196 (m), 1179 (m), 1143 (s), 1111 (m), 1070 (w), 1081 -1 -1 -1 (w), 995 (m), 827 (s) cm . UV-vis (MeOH): λmax 333 nm (ε 11,057 cm M ), 253 + (5,244), 216 (3,963). HRMS (+ESI): Found m/z 269.1166, [M+H] ; C17H17O3 required 269.1172.
4-(7-Acetoxy-2-ethyl-2H-chromen-3-yl)phenyl acetate (137)
8 Diacetoxyphenoxodiol 109 (1.00 g, 3.08 mmol) and AcO O 2 tritylium hexafluorophosphate (1.43 g, 3.68 mmol) 3 2' 6 3' were dissolved in dichloromethane (100 mL). The 5 4 6' OAc mixture was stirred at room temperature for one hour. 5' Filtration afforded the isoflavylium salt 55 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Diethylzinc solution (1.0 M in hexanes, 4.0 mL, 4.0 mmol) was added slowly at 0 °C, under an atmosphere of nitrogen. The mixture was stirred at room temperature for 2.5 hours before being quenched with saturated NH4Cl solution and extracted with dichloromethane (2 × 50 mL). The dichloromethane extracts were washed with saturated NH4Cl solution (50 mL) and evaporated in vacuo to give a yellow oil, which solidified on cooling. The crude product was recrystallised from ethyl acetate to give the title compound 137 (0.51 g, 47%) as off-white needles. M.p. 150–153 °C. Lit193. 153–156 °C. 1H NMR (300 MHz,
CDCl3): δ 7.46 (2H, d, J = 8.9 Hz, H2′,6′), 7.11 (2H, d, J = 8.9 Hz, H3′,5′), 7.06 (1H, d,
‐ 129 ‐ J = 8.8 Hz, H5), 6.68 (1H, br s, H4), 6.67-6.63 (2H, m, H6, H8), 5.20 (1H, dd, J = 3.2
Hz, 9.5 Hz, H2), 2.31 (3H, s, COCH3), 2.29 (3H, s, COCH3), 1.91–1.75 (1H, m, a b CH CH3), 1.68–1.51 (1H, m, CH CH3), 1.00 (3H, dd (app t), J = 7.6 Hz, CH2CH3).
2-Ethyl-3-(4-hydroxyphenyl)-2H-chromen-7-ol (138)157
8 The isoflavene 137 (510 mg, 1.45 mmol) was suspended HO O 2 in methanol (10 mL). Aqueous KOH (1 M, 4.0 mL, 4.0 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 5 4 6' OH room temperature for 2 hours before being neutralised 5' with 1 M acetic acid. The mixture was reduced to ~15 mL in vacuo, poured into water (75 mL) and extracted with ethyl acetate (3 × 20 mL). The extracts were combined, washed with brine and evaporated in vacuo to give the title compound 138 (390 mg, 1 94%) as a pale orange solid. M.p. 224–228 °C. H NMR (300 MHz, d6-DMSO): δ 9.54 (1H, br s, OH), 9.48 (1H, br s, OH), 7.36 (2H, d, J = 8.7 Hz, H2′,6′), 6.93 (1H, d, J = 8.1 Hz, H5), 6.76 (2H, d, J = 8.7 Hz, H3′,5′), 6.71 (1H, br s, H4), 6.31 (1H, dd, J = 2.3 Hz, 8.1 Hz, H6), 6.25 (1H, d, J = 2.3 Hz, H8), 5.18 (1H, dd, J = 3.1 Hz, 9.4 Hz, H2), 1.72– a b 1.54 (1H, m, CH CH3), 1.53–1.37 (1H, m, CH CH3), 0.93 (3H, dd (app.t), J = 7.3 Hz,
CH2CH3).
4-(7-Acetoxy-4-benzyl-4H-chromen-3-yl)phenyl acetate (145) Diacetoxyphenoxodiol 109 (1.28 g, 3.95 mmol) and 8 AcO O 2 tritylium hexafluorophosphate (1.78 g, 4.58 mmol) 2' 6 3 3' 5 were dissolved in dichloromethane (100 mL). The 2" 3" 6' OAc mixture was stirred at room temperature for 45 minutes. 5' 4" 6" Filtration afforded the isoflavylium salt 55 as a bright 5" yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Benzylzinc bromide solution (0.5 M in THF, 9.0 mL, 4.5 mmol) was added slowly under an atmosphere of nitrogen. The mixture was stirred at room temperature for 80 minutes before being quenched with saturated NH4Cl solution. The dichloromethane layer was collected, washed with water (2 × 50 mL) and brine (50 mL) and dried over
MgSO4. The solvent was evaporated in vacuo to give a yellow oil, which was recrystallised from acetonitrile to give the title compound 145 (171 mg, 10%) as fine 1 white crystals. M.p. 150–153 °C. H NMR (300 MHz, CDCl3): δ 7.45 (2H, d, J = 8.8 Hz, H2′,6′), 7.15–7.11 (5H, m, ArH), 6.82 (1H, d, J = 8.4 Hz, H5), 6.81 (1H, br s, H2),
‐ 130 ‐ 6.75–6.70 (3H, m, H6, H3′,5′), 6.64 (1H, d, J = 2.3 Hz, H8), 4.23 (1H, dd, J = 4.2 Hz, 7.1 Hz, H4), 2.99 (1H, dd, J = 4.2 Hz, 13.2 Hz, CHaPh), 2.77 (1H, dd, J = 7.1 Hz, 13.2 b 13 Hz, CH Ph), 2.32 (3H, s, COCH3), 2.29 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.5 (CO), 169.2 (CO), 151.9 (ArC), 149.7 (ArC), 149.7 (ArC), 137.9 (ArC), 134.7 (ArC), 129.9 (ArC), 129.6 (ArC), 127.8 (ArC), 126.5 (ArC), 126.2 (ArC), 122.0 (ArC),
118.7 (ArC), 116.4 (ArC), 109.4 (ArC), 43.0 (CH2), 38.8 (CH2), 21.2 (COCH3), 21.1
(COCH3). IR (KBr): νmax 3434 (w), 3027 (w), 2927 (w), 1754 (s), 1664 (w), 1617 (w), 1589 (w), 1508 (m), 1496 (m), 1454 (w), 1430 (w), 1374 (m), 1249 (w), 1204 (s), 1164 -1 (s), 1093 (w), 1014 (m), 915 (m), 898 (w), 847 (w) cm . UV-vis (MeOH): λmax 228 nm -1 -1 + (ε 25,632 cm M ). HRMS (+ESI): Found m/z 415.1531, [M+H] ; C26H23O5 required 415.1540.
4-Benzyl-3-(4-hydroxyphenyl)-4H-chromen-7-ol (146) The isoflavene 145 (118 mg, 0.285 mmol) and imidazole 8 HO O 2 (250 mg, 3.7 mmol) were dissolved in ethanol (5 mL). 2' 6 3 3' 5 The mixture was heated at reflux for 4 hours. After 2" 3" 6' OH cooling, the mixture was poured into water (15 mL). 5' 4" 6" Filtration afforded the title compound 146 (45 mg, 48%) 5" 1 as a pale pink solid. M.p. 191–192 °C. H NMR (300 MHz, d6-DMSO): δ 9.42 (1H, br s, OH), 9.35 (1H, br s, OH), 7.35 (2H, d, J = 8.7 Hz, H2′,6′), 7.10–7.08 (3H, m, ArH), 6.87 (1H, br s, H2), 6.81–6.78 (3H, m, H5 H3′,5′), 6.67–6.64 (2H, m, ArH), 6.42 (1H, dd, J = 2.4 Hz, 8.3 Hz, H6), 6.16 (1H, d, J = 2.4 Hz, H8), 4.26 (1H, dd, J = 3.9 Hz, 5.8 Hz, H4), 2.87 (1H, dd, J = 3.9 Hz, 13.2 Hz, CHaPh), 2.64 (1H, dd, J = 5.8 Hz, 13.2 Hz, b 13 CH Ph), C NMR (75 MHz, d6-DMSO): δ 156.5 (ArC), 156.4 (ArC), 151.6 (ArC), 138.2 (ArC), 137.1 (ArC), 129.6 (ArC), 127.4 (ArC), 127.1 (ArC), 126.3 (ArC), 125.8
(ArC), 116.3 (ArC), 115.6 (ArC), 113.1 (ArC), 110.7 (ArC), 101.7 (ArC), 41.7 (CH2),
36.5 (CH2). IR (KBr): νmax 3384 (s), 3028 (w), 2922 (w), 2860 (w), 1662 (w), 1628 (m), 1601 (m), 1507 (s), 1459 (s), 1371 (w), 1342 (w), 1242 (m), 1225 (m), 1170 (s), 1090 -1 (w), 1008 (w), 956 (m), 831 (m), 813 (m) cm . UV-vis (MeOH): λmax 288 nm (ε 13,661 cm-1M-1), 239 (7,731), 212 (10,720). HRMS (+ESI): Found m/z 331.1327, [M+H]+;
C22H19O3 required 331.1329.
‐ 131 ‐ 4-(7-Acetoxy-2-(ethylamino)-2H-chromen-3-yl)phenyl acetate (147)
Diacetoxyphenoxodiol 109 (1.02 g, 3.14 mmol) and 8 H AcO O 2 N tritylium hexafluorophosphate (1.43 g, 3.68 mmol) 3 2' 6 3' were dissolved in dichloromethane (100 mL). The 5 4 6' OAc mixture was stirred at room temperature for one hour. 5' Filtration afforded the isoflavylium salt 55 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Ethylamine solution (2.0 M in THF, 2.0 mL, 4.0 mmol) was added under an atmosphere of nitrogen. The mixture was stirred at room temperature for one hour, during which time it became clear and colourless. The mixture was washed with water (2 × 50 mL) and brine (50 mL) and evaporated in vacuo to give a pale yellow amorphous solid. The crude product was recrystallised from ethyl acetate to give the title compound 147 (0.56 g, 49%) as fine 1 white crystals. M.p. 134–138 °C. H NMR (300 MHz, CDCl3): δ 7.53 (2H, d, J = 8.8 Hz, H2′,6′), 7.23 (1H, d, J = 8.1 Hz, H5), 7.12 (2H, d, J = 8.8 Hz, H3′,5′), 6.98 (1H, br s, H4), 6.82 (1H, d, J = 2.3 Hz, H8), 6.77 (1H, dd, J = 2.3 Hz, 8.1 Hz, H6), 5.95 (1H, br s, a H2), 4.00 (1H, dq, J = 7.1 Hz, 9.8 Hz, CH CH3), 3.79 (1H, dd, J = 7.1 Hz, 9.8 Hz, b CH CH3), 2.31 (3H, s, COCH3), 2.30 (3H, s, COCH3), 1.25 (3H, dd (app. t), J = 7.1 Hz, 13 CH2CH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.2 (CO), 151.2 (ArC), 150.9 (ArC), 150.4 (ArC), 134.5 (ArC), 129.6 (ArC), 127.8 (ArC), 126.8 (ArC), 126.7 (ArC), 121.9 (ArC), 121.9 (ArC), 121.3 (ArC), 119.4 (ArC), 115.2 (ArC), 110.1 (ArC), 97.0
(C2), 63.8 (CH2), 21.2 (COCH3), 15.3 (CH2CH3). IR (KBr): νmax 3440 (m), 2976 (w), 2934 (w), 1752 (s), 1610 (m), 1586 (w), 1509 (s), 1497 (s), 1434 (m), 1368 (s), 1281 (w), 1260 (m), 1208 (s), 1173 (s), 1140 (s), 1116 (s), 1075 (m), 1013 (s), 989 (m), 948 -1 -1 -1 (w), 907 (m), 846 (w) cm . UV-vis (MeOH): λmax 267 nm (ε 25,994 cm M ). HRMS + (+ESI): Found m/z 368.1486, [M+H] ; C21H22NO5 required 368.1492.
4-(7-Acetoxy-2-(benzylamino)-2H-chromen-3-yl)phenyl acetate (148) Diacetoxyphenoxodiol 109 (1.09 g, 3.36 mmol) and 3" 2" 4" H tritylium hexafluorophosphate (1.47 g, 3.79 mmol) 8 2 AcO O N 5" 6" were dissolved in dichloromethane (100 mL). The 3 2' 6 3' mixture was stirred at room temperature for one hour. 5 4 6' OAc Filtration afforded the isoflavylium salt 55 as a bright 5' yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Benzylamine (0.50 mL, 4.6 mmol) was added under an atmosphere of nitrogen. The
‐ 132 ‐ mixture was stirred at room temperature for 2.5 hours, during which time it became clear and colourless. The mixture was quenched with saturated NH4Cl solution, washed with water (2 × 50 mL) and brine (50 mL) and evaporated in vacuo to give the title compound 148 (750 mg, 52%) as a pale yellow amorphous solid. M.p. 233–236 °C. 1H
NMR (300 MHz, CDCl3): δ 7.58 (2H, d, J = 8.7 Hz, H2′,6′), 7.36–7.17 (5H, m, ArH), 7.14 (1H, d, J = 8.4 Hz, H5), 7.08 (2H, d, J = 8.7 Hz, H3′,5′), 6.88 (1H, br s, H4), 6.79 (1H, d, J = 2.2 Hz, H8), 6.72 (1H, dd, J = 2.2 Hz, 8.4 Hz, H6), 5.69 (1H, br s, H2), 4.07 13 (2H, dd, J = 13.5 Hz, 24.2 Hz, CH2Ph), 2.32 (3H, s, COCH3), 2.30 (3H, s, COCH3). C
NMR (75 MHz, CDCl3): δ 170.0 (CO), 168.3 (CO), 162.1 (ArC), 156.7 (ArC), 142.4 (ArC), 140.7 (ArC), 138.2 (ArC), 130.8 (ArC), 129.7 (ArC), 127.8 (ArC), 126.5 (ArC), 118.2 (ArC), 115.7 (ArC), 118.7 (ArC), 115.7 (ArC), 109.2 (ArC), 104.5 (ArC), 85.5
(C2), 48.6 (CH2), 23.3 (COCH3). IR (KBr): νmax 3436 (m), 2997 (m), 2977 (m), 2886 (w), 2756 (w), 2690 (w), 2574 (w), 1664 (w), 1655 (m), 1648 (m), 1638 (s), 1629 (s), 1618 (s), 1598 (s), 1571 (m), 1534 (w), 1546 (w), 1499 (m), 1492 (w), 1478 (s), 1467 (s), 1454 (m), 1383 (m), 1216 (s), 1164 (m), 1113 (s), 1059 (s), 1031 (w), 970 (w), 919 -1 -1 -1 (w), 881 (w), 745 (s) cm . UV-vis (MeOH): λmax 368 nm (ε 3,336 cm M ), 346 (3,336), 266 (2,791), 205 (15,461). HRMS (+ESI): Found m/z 430.1641, [M+H]+;
C26H24NO5 required 430.1649.
3-(4-Hydroxyphenyl)-2-methoxy-2H-chromen-7-ol
8 (149) HO O 2 O The isoflavene 147 (107 mg, 0.29 mmol) was suspended 2' 6 3' in methanol (5 mL). Aqueous KOH (1 M, 0.7 mL, 0.7 5 4 6' OH mmol) was added dropwise. The mixture was stirred at 5' room temperature for 30 minutes before being neutralised with 1 M acetic acid. Water (10 mL) was added. Filtration afforded the title compound 149 (52 mg, 66%) as a pink 1 powder. M.p. 188–191 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.61 (2H, br s, OH), 7.37 (2H, d, J = 8.8 Hz, H2′,6′), 7.10 (1H, d, J = 8.8 Hz, H5), 6.96 (1H, br s, H4), 6.79 (2H, d, J = 8.8 Hz, H3′,5′), 6.47-6.42 (2H, m, H6, H8), 5.90 (1H, br s, H2), 3.44 13 (3H, s, OCH3). C NMR (75 MHz, d6-DMSO): δ 158.3 (ArC), 157.0 (ArC), 150.8 (ArC), 127.7 (ArC), 127.2 (ArC), 126.6 (ArC), 126.2 (ArC), 118.4 (ArC), 115.5 (ArC),
113.9 (ArC), 109.3 (ArC), 103.1 (ArC), 97.3 (C2), 54.3 (OCH3). IR (KBr): νmax 3359 (s), 3204 (m), 3033 (w), 2945 (w), 2821 (w), 1754 (w), 1617 (s), 1513 (s), 1462 (s), 1442 (m), 1402 (w), 1372 (m), 1309 (w), 1290 (m), 1249 (s), 1226 (s), 1183 (m), 1163
‐ 133 ‐ (s), 1117 (s), 1069 (w), 1022 (s), 993 (w), 956 (m), 943 (m), 914 (m), 833 (m), 805 (w), -1 -1 -1 740 (w) cm . UV-vis (MeOH): λmax 324 nm (ε 3,336 cm M ), 237 (6,642), 210 + (12,777). HRMS (+ESI): Found m/z 293.0781, [M+Na] ; C16H14O4Na required 293.0784.
2-Ethoxy-3-(4-hydroxyphenyl)-2H-chromen-7-ol (150)
8 The isoflavene 147 (145 mg, 0.39 mmol) and imidazole HO O 2 O
(277 mg, 4.07 mmol) were dissolved in absolute ethanol 3 2' 6 3' (5 mL). The mixture was heated at reflux, under nitrogen, 5 4 6' OH for 4 hours. Once cooled, the reaction mixture was 5' poured into water (15 mL). Filtration afforded the title compound 150 (58 mg, 52%) as 1 an off-white powder. M.p. 206–208 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.84 (1H, br s, OH), 9.52 (1H, br s, OH), 7.23 (2H, d, J = 8.8 Hz, H2′,6′), 7.11 (1H, d, J = 8.8 Hz, H5), 7.01 (1H, br s, H4), 6.67–6.64 (2H, m, H6, H8), 6.60 (2H, d, J = 8.8 Hz,
H3′,5′), 5.96 (1H, br s, H2), 3.85–3.79 (2H, m, OCH2), 1.07 (3H, dd (app. t), J = 7.1 Hz, 13 CH3). C NMR (75 MHz, d6-DMSO): δ 158.0 (ArC), 156.8 (ArC), 151.2 (ArC), 128.2 (ArC), 127.3 (ArC), 126.6 (ArC), 126.1 (ArC), 117.5 (ArC), 115.4 (ArC), 113.9 (ArC),
108.7 (ArC), 103.0 (ArC), 96.2 (C2), 62.6 (OCH2), 15.2 (CH3). IR (KBr): νmax 3384 (s), 1617 (s), 1595 (m), 1515 (s), 1462 (m), 1401 (w), 1376 (w), 1355 (w), 1287 (m), 1249 (s), 1183 (w), 1152 (m), 1121 (m), 1063 (w), 1022 (w), 996 (w), 978 (w), 959 (m), 908 -1 -1 -1 (m), 830 (m), 804 (w) cm . UV-vis (MeOH): λmax 272 nm (ε 11,259 cm M ). HRMS + (+ESI): Found m/z 307.0935, [M+Na] ; C17H16O4Na required 307.0941.
4-(7-Acetoxy-2-methoxy-2H-chromen-3-yl)phenyl acetate (151)
8 Isoflavylium salt 55 (100 mg, 0.21 mmol) was AcO O 2 O dissolved in methanol (10 mL). The mixture was stirred 3 2' 6 3' at room temperature for 20 minutes and filtered to give 5 4 6 OAc the title compound 151 (29 mg, 39 %) as pale pink 5' 163 1 needles. M.p. 147-150 °C, Lit 149–151 °C. H NMR (300 MHz, CDCl3): δ 7.52 (2H, d, J = 8.8 Hz, H2′,6′), 7.23 (1H, d, J = 8.2 Hz, H5), 7.12 (2H, d, J = 8.8 Hz, H3′,5′), 6.98 (1H, br s, H4), 6.85 (1H, d, J = 2.2 Hz, H8), 6.77 (1H, dd, J = 2.2 Hz, 8.2 Hz, H6), 5.85
(1H, br s, H2), 3.58 (3H, s, OCH3), 2.32 (3H, s, COCH3), 2.30 (3H, s, COCH3).
‐ 134 ‐ 4-(7-Acetoxy-2-ethoxy-2H-chromen-3-yl)phenyl acetate (152)
8 Isoflavylium salt 55 (460 mg, 0.97 mmol) was AcO O 2 O dissolved in ethanol (10 mL). The mixture was stirred 3 2' 6 3' at room temperature for 19 hours and filtered to give 5 4 6' OAc the title compound (87 mg, 24%) as white needles. M.p. 5' 163 1 133–135 °C, Lit 134–136 °C. H NMR (300 MHz, CDCl3) δ 7.53 (2H, d, J = 8.8 Hz, H2′,6′), 7.23 (1H, d, J = 8.3 Hz, H5), 7.12 (2H, d, J = 8.8 Hz, H3′,5′), 6.98 (1H, br s, H4), 6.82 (1H, d, J = 2.3 Hz, H8), 6.77 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 5.95 (1H, br s, a b H2), 4.07–3.94 (1H, m, OCH CH3), 3.84–3.74 (1H, m, OCH CH3), 2.32 (3H, s,
COCH3), 2.20 (3H, s, COCH3), 1.25 (3H, dd (app t), J = 7.1 Hz, OCH2CH3).
4-(7-Acetoxy-2-(4-amino-3,5-dimethylphenyl)-2H-chromen-3-yl)phenyl acetate (153) Diacetoxyphenoxodiol 109 (1.00 g, 3.08 mmol) and 2" NH2 tritylium hexafluorophosphate (1.43 g, 3.68 mmol) 8 AcO O 2 were dissolved in dichloromethane (100 mL). The 6" 3 2' 6 3' mixture was stirred at room temperature for 45 minutes. 5 4 6' OAc Filtration afforded the isoflavylium salt 55 as a bright 5' yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). 2,6-Dimethylaniline (0.75 mL, 6.6 mmol) was added under an atmosphere of nitrogen. The mixture was stirred at room temperature for 15 minutes, during which time it became clear and colourless, then pale purple and cloudy. The pale purple precipitate was collected by filtration. The crude product was recrystallised from ethyl acetate to give the title compound 153 (711 mg, 52%) as small purple crystals. M.p. 220–222 °C. 1 H NMR (300 MHz, CDCl3): δ 7.38 (2H, d, J = 8.7 Hz, H2′,6′), 7.12 (1H, d, J = 8.3 Hz, H5), 7.04 (1H, br s, H4), 7.03–6.97 (4H, m, H3′,5′, H2″,6″), 6.62 (1H, dd, J = 2.2 Hz,
8.3 Hz, H6), 6.49 (1H, d, J = 2.2 Hz, H8), 6.09 (1H, br s, H2), 3.48 (2H, br s, NH2), 13 2.28 (3H, s, COCH3), 2.23 (3H, s, COCH3), 2.09 (6H, s, CH3). C NMR (75 MHz,
CDCl3): δ 169.6 (CO), 169.4 (CO), 152.5 (ArC), 151.5 (ArC), 150.3 (ArC), 143.6 (ArC), 135.2 (ArC), 131.8 (ArC), 129.2 (ArC), 127.4 (ArC), 127.3 (ArC), 126.8 (ArC), 121.9 (ArC), 121.8 (ArC), 120.8 (ArC), 120.3 (ArC), 114.4 (ArC), 110.2 (ArC), 78.6
(C2), 21.3 (COCH3), 18.0 (CH3). IR (KBr): νmax 3481 (m), 3394 (m), 3075 (w), 2966 (w), 2930 (w), 2850 (w), 1757 (s), 1655 (w), 1625 (m), 1609 (m), 1513 (m), 1492 (m), 1431 (w), 1368 (m), 1306 (w), 1257 (w), 1207 (s), 1193 (s), 1180 (s), 1153 (m), 1137
‐ 135 ‐ (s), 1111 (m), 1019 (m), 984 (w), 961 (w), 907 (m), 875 (w), 849 (m) cm-1. UV-vis -1 -1 (MeOH): λmax 333 nm (ε 7,908 cm M ), 295 (7,462), 246 (13,304), 209 (20,179). + HRMS (+ESI): Found m/z 444.1797, [M+H] ; C27H26NO5 required 444.1805.
2-(4-Amino-3,5-dimethylphenyl)-3-(4-hydroxyphenyl)-2H-chromen-7-ol (154) The isoflavene 153 (100 mg, 0.23 mmol) was NH suspended in methanol (10 mL). Aqueous KOH (1 M, 2" 2 8 HO O 2 2.0 mL, 2.0 mmol) was added dropwise. The mixture 6" 3 2' was stirred at room temperature for 15 minutes before 6 3' 5 4 being neutralised with 2 M HCl. Water (15 mL) was 6' OH 5' added. Filtration afforded the title compound 154 (53 mg, 64%) as a pale purple powder. 1 M.p. 208–212 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.46 (2H, br s, OH), 7.26 (2H, d, J = 8.7 Hz, H2′,6′), 7.01 (1H, br s, H4), 6.99 (1H, d, J = 8.3 Hz, H5), 6.82 (2H, s, H2″,6″), 6.68 (2H, d, J = 8.8 Hz, H3′,5′), 6.26 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6),
6.04 (1H, br s, H2), 6.03 (1H, d, J = 2.3 Hz, H8), 4.59 (2H, br s, NH2), 1.96 (6H, s, 13 CH3). C NMR (75 MHz, d6-Acetone) δ 159.2 (ArC), 157.8 (ArC), 153.9 (ArC), 143.6 (ArC), 130.7 (ArC), 130.1 (ArC), 129.1 (ArC), 128.2 (ArC), 127.8 (ArC), 127.3 (ArC), 121.9 (ArC), 118.7 (ArC), 116.9 (ArC), 116.2 (ArC), 109.0 (ArC), 104.3 (ArC), 79.0
(C2), 18.1 (CH3). IR (KBr): νmax 3395 (s), 2959 (w), 2923 (m), 2852 (w), 1655 (w), 1618 (s), 1591 (m), 1561 (w), 1516 (s), 1487 (m), 1460 (m), 1376 (w), 1274 (m), 1242 (m), 1182 (m), 1157 (s), 1118 (s), 1028 (w), 984 (w), 875 (w), 832 (m), 810 (w), 744 (w) -1 -1 -1 cm . UV-vis (MeOH): λmax 337 nm (ε 13,100 cm M ), 245 (12,957), 207 (28,591). + HRMS (+ESI): Found m/z 360.1587, [M+H] ; C23H22NO3 required 360.1594.
4-(7-Acetoxy-2-((2,4-dimethylphenyl)amino)-2H- chromen-3-yl)phenyl acetate (155) 5" 3" 2,4-Dimethylaniline (0.15 mL, 1.2 mmol) was added to 6" a suspension of isoflavylium salt 55 (500 mg, 1.06 8 AcO O 2 NH mmol) in ethyl acetate (50 mL). The mixture was 3 2' 6 3' heated to 50 °C for 18 hours. Once cooled, the mixture 5 4 6' OAc was washed with water (2 × 30 mL) and brine (30 mL) 5' and dried over MgSO4. Solvent was evaporated in vacuo to give the title compound 155 (304 mg, 65%) as a golden brown amorphous solid. M.p. 164–167 °C. 1H NMR (300
MHz, d6-DMSO): δ 7.62 (2H, d, J = 8.7 Hz, H2′,6′), 7.38 (1H, d, J = 8.3 Hz, H5), 7.31
‐ 136 ‐ (1H, br s, H4), 7.27 (1H, d, J = 8.3 Hz, H6″), 7.16 (2H, d, J = 8.7 Hz, H3′,5′), 6.96 (1H, dd, J = 1.1 Hz, 8.3 Hz, H5″), 6.83 (1H, d, J = 1.1 Hz, H3″), 6.78 (1H, dd, J = 2.1 Hz, 8.3 Hz, H6), 6.65 (1H, d, J = 2.1 Hz, H8), 6.52 (1H, d, J = 9.7 Hz, NH), 5.57 (1H, d, J =
9.7 Hz, H2), 2.27 (3H, s, COCH3), 2.22 (3H, s, COCH3), 2.19 (3H, s, 4″-CH3), 1.91 13 (3H, s, 2″-CH3). C NMR (75 MHz, CDCl3): δ 171.8 (CO), 168.8 (CO), 164.7 (ArC), 152.8 (ArC), 152.0 (ArC), 150.1 (ArC), 139.5 (ArC), 134.0 (ArC), 132.9 (ArC), 130.1 (ArC), 128.5 (ArC), 127.0 (ArC), 122.3 (ArC), 119.6 (ArC), 117.2 (ArC), 115.5 (ArC),
106.8 (ArC), 105.3 (ArC), 103.0 (ArC), 89.9 (ArC), 81.3 (C2), 26.7 (CH3), 21.4 (CH3),
14.5 (CH3). IR (KBr): νmax 3432 (m), 3022 (w), 2917 (w), 2860 (w), 1755 (s), 1612 (m), 1510 (s), 1434 (w), 1368 (m), 1301 (w), 1258 (m), 1197 (s), 1170 (s), 1154 (m), 1113 (m), 1096 (w), 1015 (m), 980 (m), 905 (m), 847 (w), 807 (w) cm-1. UV-vis (MeOH): -1 -1 λmax 322 nm (ε 6,393 cm M ), 291 (6,431), 238 (8,500), 204 (19,403). HRMS (+ESI): + Found m/z 444.1796, [M+H] ; C27H26NO5 required 444.1805.
4-(7-Acetoxy-2-((3,5-dimethylphenyl)amino)-2H- chromen-3-yl)phenyl acetate (156) 4" 3,5-Dimethylaniline (0.10 mL, 0.8 mmol) was added to 2" 6" 8 a suspension of isoflavylium salt 55 (250 mg, 0.53 AcO O 2 NH mmol) in THF (10 mL). The mixture was heated to 60 3 2' 6 3' °C for 2 hours. Water (20 mL) was added. Filtration 5 4 6' OAc afforded the title compound 156 (140 mg, 66%) as a 5' 1 golden brown amorphous solid. M.p. 140–143 °C. H NMR (300 MHz, d6-DMSO): δ 7.57 (2H, d, J = 8.7 Hz, H2′,6′), 7.36 (1H, d, J = 8.3 Hz, H5), 7.28 (1H, br s, H4), 7.14 (2H, d, J = 8.7 Hz, H3′,5′), 6.77 (1H, d, J = 9.4 Hz, NH), 6.72 (1H, dd, J = 2.1 Hz, 8.3 Hz, H6), 6.64 (1H, d, J = 2.1 Hz, H8), 6.58 (2H, br s, H2″,6″), 6.54 (1H, d, J = 9.4 Hz,
H2) 6.35 (1H, br s, H4″), 2.25 (3H, s, COCH3), 2.19 (3H, s, COCH3), 2.16 (6H, s, CH3). 13 C NMR (75 MHz, CDCl3): δ 169.6 (CO), 169.3 (CO), 153.9 (ArC), 150.6 (ArC), 141.1 (ArC), 132.2 (ArC), 128.1 (ArC), 126.9 (ArC), 126.8 (ArC), 122.0 (ArC), 121.9 (ArC), 116.2 (ArC), 110.0 (ArC), 108.8 (ArC), 105.3 (ArC), 97.3 (ArC), 95.5 (ArC),
91.6 (ArC), 74.7 (C2), 21.2 (CH3), 21.0 (CH3). IR (KBr): νmax 3358 (m), 3022 (w), 2917 (w), 2860 (w), 1753 (s), 1662 (m), 1612 (s), 1601 (s), 1531 (w), 1509 (s), 1497 (m), 1431 (m), 1367 (m), 1330 (m), 1280 (w), 1258 (w), 1198 (s), 1169 (s), 1143 (m), 1106 (s), 1015 (m), 976 (m), 912 (w), 899 (w), 841 (m), 826 (m) cm-1. UV-vis (MeOH):
‐ 137 ‐ -1 -1 λmax 326 nm (ε 6,208 cm M ), 282 (6,800), 205 (24,391). HRMS (+ESI): Found m/z + 444.1797, [M+H] ; C27H26NO5 required 444.1805.
4-(7-Acetoxy-2-(pyrrolidin-1-yl)-2H-chromen-3-yl)phenyl acetate (157)
Diacetoxyphenoxodiol 109 (1.09 g, 3.36 mmol) and 2" 3" 8 tritylium hexafluorophosphate (1.53 g, 3.94 mmol) AcO O 2 N 4" 5" 3 2' were dissolved in dichloromethane (100 mL). The 6 3' 5 4 mixture was stirred at room temperature for one hour. 6' OAc Filtration afforded the isoflavylium salt 55 as a bright 5' yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). 1- Trimethylsilylpyrollidine (1.0 mL, 5.7 mmol) was added under an atmosphere of nitrogen. The mixture was stirred at room temperature for three hours, during which time it became clear and colourless. The mixture was quenched with saturated NH4Cl solution, washed with water (2 × 50 mL) and brine (50 mL) and evaporated in vacuo to give an off-white amorphous solid. The crude product was recrystallised from ethyl acetate and then triturated with acetonitrile to give the title compound 157 (155 mg, 1 12%) as a tan powder. M.p. 110–112 °C. H NMR (300 MHz, CDCl3): δ 7.65 (2H, d, J = 8.8 Hz, H2′,6′), 7.13–7.06 (3H, m, H5, H3′,5′), 6.92 (1H, br s, H4), 6.69–6.61 (2H, m, H6, H8), 5.96 (1H, br s, H2), 3.06–2.96 (4H, m, H2″, H5″), 2.86–2.78 (4H, m, H3″, 13 H4″), 2.29 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.5 (CO), 169.3 (CO), 151.3 (ArC), 150.2 (ArC), 144.0 (ArC), 142.9 (ArC), 138.0 (ArC), 135.6 (ArC), 129.9 (ArC), 127.5 (ArC), 127.2 (ArC), 126.8 (ArC), 121.6 (ArC), 119.1 (ArC), 113.5 (ArC),
108.4 (ArC), 87.4 (C2), 46.2 (C2″,5″), 24.4 (C3″,4″), 21.1 (COCH3). IR (KBr): νmax 3433 (m), 2967 (w), 2842 (w), 1755 (s), 1632 (w), 1610 (m), 1539 (w), 1511 (s), 1497 (m), 1432 (m), 1369 (s), 1309 (w), 1235 (s), 1207 (s), 1172 (s), 1139 (m), 1112 (s), 1041 (w), 1016 (s), 982 (m), 964 (w), 911 (m), 897 (w), 847 (m), 805 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 328 nm (ε 15,655 cm M ), 292 (16,934), 239 (16,687), 205 (27,229). + HRMS (+ESI): Found m/z 394.1640, [M+H] ; C23H24NO5 required 394.1649.
‐ 138 ‐ 4-(7-Acetoxy-2-morpholino-2H-chromen-3-yl)phenyl acetate (158) 4-Trimethylsilylmorpholine (0.27 mL, 1.5 mmol) was 3" added to a suspension of isoflavylium salt 55 (500 mg, 2" O 8 AcO O 2 N 1.07 mmol) in dichloromethane (30 mL). The mixture 5" 6" 3 2' 6 was stirred at room temperature for 22 hours before 3' 5 4 being quenched with saturated NH4Cl solution, washed 6' OAc 5' with water (2 × 10 mL) and brine (10 mL) and evaporated in vacuo to give an off-white amorphous solid. The crude product was recrystallised from ethanol to give the title compound 158 (116 mg, 26%) as white 1 plates. M.p. 105–106 °C. H NMR (300 MHz, CDCl3): δ 7.70 (2H, d, J = 8.8 Hz, H2′,6′), 7.14–7.08 (3H, m, H5, H3′,5′), 7.03 (1H, br s, H4), 6.70 (1H, d, J = 2.2 Hz, H8), 6.67 (1H, dd, J = 2.2 Hz, 8.1 Hz, H6), 5.74 (1H, br s, H2), 3.61 (4H, dd (app t), J = 4.7 a b Hz, OCH2), 3.08–2.97 (2H, m, NCH ), 2.69–2.58 (2H, m, NCH ), 2.32 (3H, s, COCH3), 13 2.29 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.7 (CO), 169.4 (CO), 154.5 (ArC), 151.8 (ArC), 150.5 (ArC), 135.5 (ArC), 127.8 (ArC), 127.5 (ArC), 127.3 (ArC), 123.2 (ArC), 121.9 (ArC), 119.0 (ArC), 114.3 (ArC), 108.7 (ArC), 91.1 (C2), 67.3
(OCH2), 47.2 (NCH2), 21.4 (COCH3). IR (KBr): νmax 3446 (m), 2951 (w), 2920 (w), 2851 (w), 1756 (s), 1734 (w), 1716 (w), 1699 (w), 1684 (m), 1653 (s), 1647 (m), 1635 (s), 1616 (m), 1576 (w), 1558 (s), 1540 (m), 1507 (s), 1497 (m), 1472 (w), 1456 (m), 1435 (w), 1371 (m), 1254 (w), 1199 (s), 1173 (s), 1138 (m), 1109 (s), 1068 (w), 1036 -1 (w), 1016 (m), 992 (w), 910 (w), 844 (w) cm . UV-vis (MeOH): λmax 326 nm (ε 6,141 -1 -1 + cm M ), 203 (11,873). HRMS (+ESI): Found m/z 410.1592, [M+H] ; C22H24NO6 required 410.1598.
4-(7-Acetoxy-2-(2-oxopyrrolidin-1-yl)-2H-chromen-3-yl)phenyl acetate (159)
1-Trimethylsilyl-2-pyrollidinone (0.24 mL, 1.5 mmol) O 3"
8 4" was added to a suspension of isoflavylium salt 55 (500 AcO O 2 N 5" mg, 1.07 mmol) in dichloromethane (30 mL). The 3 2' 6 3' mixture was stirred at room temperature for 22 hours 5 4 6' OAc 5' before being quenched with saturated NH4Cl solution, washed with water (2 × 10 mL) and brine (10 mL) and evaporated in vacuo to give the title compound 159 (476 mg, 78%) as a white powder. M.p. 188–191 °C. 1H NMR (300
MHz, CDCl3): δ 7.53 (2H, d, J = 8.8 Hz, H2′,6′), 7.19–7.14 (3H, m, H2, H4, H5), 7.11 (2H, d, J = 8.8 Hz, H3′,5′), 6.75–6.71 (2H, m, H6, H8), 3.21–3.03 (2H, m, H5″), 2.57–
‐ 139 ‐ 2.33 (2H, m, H3″), 2.31 (3H, s, COCH3), 2.29 (3H, s, COCH3), 1.96–1.70 (2H, m, H4″). 13 C NMR (75 MHz, CDCl3): δ 175.3 (CO), 169.6 (CO), 169.4 (CO), 152.9 (ArC), 151.8 (ArC), 150.9 (ArC), 133.1 (ArC), 127.9 (ArC), 126.7 (ArC), 126.2 (ArC), 122.4 (ArC), 122.0 (ArC), 118.4 (ArC), 115.3 (ArC), 109.5 (ArC), 75.8 (C2), 43.1 (C5″), 31.3 (C3″),
21.3 (COCH3), 18.0 (C4″). IR (KBr): νmax 3448 (m), 2975 (w), 1753 (s), 1690 (s), 1648 (w), 1638 (w), 1612 (m), 1585 (w), 1561 (w), 1513 (m), 1499 (m), 1460 (w), 1408 (s), 1367 (m), 1281 (m), 1258 (s), 1232 (s), 1208 (s), 1173 (s), 1141 (m), 1117 (s), 1038 (m), -1 1017 (s), 971 (m), 918 (m), 894 (w), 848 (m) cm . UV-vis (MeOH): λmax 326 nm (ε 5,408 cm-1M-1), 304 (4,546), 239 (4,981), 206 (7,722). HRMS (+ESI): Found m/z + 408.1434, [M+H] ; C23H22NO6 required 408.1442.
1-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)pyrrolidin-2-one (160)
The isoflavene 159 (13 mg, 0.032 mmol) was suspended O 3"
8 in methanol (1 mL). Aqueous KOH (1 M, 0.1 mL, 0.1 HO O 2 N 4" 5" mmol) was added dropwise. The mixture was stirred at 3 2' 6 3' room temperature for 45 minutes before being neutralised 5 4 6' OH with 1 M acetic acid. Water (3 mL) was added. Filtration 5' afforded the title compound 160 (10 mg, 97%) as an off-white powder. M.p. 219–221 1 °C (decomp.). H NMR (300 MHz, d6-Acetone): δ 8.62 (1H, br s, OH), 8.54 (1H, br s, OH), 7.41 (2H, d, J = 8.8 Hz, H2′,6′), 7.18 (1H, br s, H4), 7.11 (1H, d, J = 8.3 Hz, H5), 6.98 (1H, br s, H2), 6.84 (2H, d, J = 8.8 Hz, H3′,5′), 6.49 (1H, dd, J = 2.4 Hz, 8.3 Hz, H6), 6.39 (1H, d, J = 2.4 Hz, H8), 3.20–3.11 (1H, m, H5″a), 3.08–2.98 (1H, m, H5″b), 13 2.38–2.15 (2H, m, H3″), 1.96–1.67 (2H, m, H4″). C NMR (75 MHz, d6-Acetone): δ 175.1 (CO), 159.8 (ArC), 158.4 (ArC), 159.2 (ArC), 129.0 (ArC), 128.2 (ArC), 126.9 (ArC), 125.3 (ArC), 121.0 (ArC), 116.6 (ArC), 114.7 (ArC), 110.0 (ArC), 103.1 (ArC),
76.6 (C2), 43.6 (C5″), 31.6 (C3″), 18.8 (C4″). IR (KBr): νmax 3372 (m), 3163 (m), 2813 (w), 1656 (s), 1614 (s), 1592 (m), 1519 (s), 1459 (m), 1436 (m), 1417 (m), 1400 (w), 1375 (w), 1290 (s), 1230 (m), 1183 (m), 1149 (s), 1120 (s), 1047 (m), 1024 (w), 970 (w), -1 937 (w), 917 (w), 879 (w), 854 (w), 827 (m), 741 (w) cm . UV-vis (MeOH): λmax 333 nm (ε 5,096 cm-1M-1), 241 (2,856), 211 (4,904). HRMS (+ESI): Found m/z 346.1045, + [M+Na] ; C19H17NO4Na required 346.1050.
‐ 140 ‐ 4-(7-Acetoxy-2-(ethylthio)-2H-chromen-3-yl)phenyl acetate (161)
8 Diacetoxyphenoxodiol 109 (1.22 g, 3.76 mmol) and AcO O 2 S tritylium hexafluorophosphate (1.77 g, 4.56 mmol) 3 2' 6 3' were dissolved in dichloromethane (100 mL). The 5 4 6' OAc mixture was stirred at room temperature for one hour. 5' Filtration afforded the isoflavylium salt 55 as a bright yellow solid, which was immediately suspended in fresh dichloromethane (100 mL). Ethanethiol (0.50 mL, 6.8 mmol) was added under an atmosphere of nitrogen. The mixture was stirred at room temperature for 2.5 hours before being quenched with saturated NH4Cl solution. The dichloromethane layer was washed with water (2 × 50 mL) and brine (50 mL) and evaporated in vacuo to give a yellow-brown amorphous solid. The crude product was recrystallised from ethyl acetate to give the title compound 161 (0.77 g, 53%) as white 1 plates. M.p. 107–109 °C. H NMR (300 MHz CDCl3): δ 7.61 (2H, d, J = 8.9 Hz, H2′,6′), 7.17 (1H, d, J = 8.3 Hz, H5), 7.13 (2H, d, J = 8.9 Hz, H3′,5′), 6.86 (1H, br s, H4), 6.81–
6.75 (2H, m, H6, H8), 6.47 (1H, s, H2), 2.88–2.64 (2H, m, SCH2CH3), 2.31 (3H, s, 13 COCH3), 2.29 (3H, s, COCH3), 1.35 (3H, dd (app t), J = 7.4 Hz, CH2CH3). C NMR
(75 MHz, CDCl3): δ 169.5 (CO), 169.3 (CO), 151.7 (ArC), 150.8 (ArC), 150.7 (ArC), 133.7 (ArC), 130.7 (ArC), 127.7 (ArC), 126.8 (ArC), 122.1 (ArC), 121.4 (ArC), 121.3
(ArC), 115.9 (ArC), 111.1 (ArC), 82.7 (C2), 25.5 (SCH2CH3), 21.3 (COCH3), 15.3
(SCH2CH3). IR (KBr): νmax 3432 (m), 2971 (w), 2956 (w), 2925 (w), 1754 (s), 1653 (w), 1608 (m), 1585 (w), 1510 (m), 1497 (m), 1450 (w), 1429 (w), 1368 (m), 1262 (m), 1216 (s), 1198 (s), 1173 (s), 1138 (s), 1110 (s), 1043 (w), 1025 (m), 1016 (m), 974 (m), -1 910 (m), 904 (w), 844 (w), 801 (w), 753 (w) cm . UV-vis (MeOH): λmax 329 nm (ε 11,649 cm-1M-1), 240 (10,380), 205 (16,570). HRMS (+ESI): Found m/z 407.0917, + [M+Na] ; C21H20O5SNa required 407.0924.
4-(7-Acetoxy-2-(benzylthio)-2H-chromen-3- yl)phenyl acetate (162) 3" 2" 4" Diacetoxyphenoxodiol 109 (1.02 g, 3.14 mmol) and 5" 8 6" tritylium hexafluorophosphate (1.44 g, 3.71 mmol) AcO O 2 S were dissolved in dichloromethane (100 mL). The 3 2' 6 3' mixture was stirred at room temperature for 90 minutes. 5 4 6' OAc Filtration afforded the isoflavylium salt 55 as a bright 5' yellow solid, which was immediately suspended in fresh dichloromethane (100 mL).
‐ 141 ‐ Benzylthiol (1.00 mL, 8.50 mmol) was added under an atmosphere of nitrogen. The mixture was stirred at room temperature for 3 hours. The mixture was washed with water (2 × 50 mL) and brine (50 mL) and evaporated in vacuo to give an off-white amorphous solid. The crude product was recrystallised from ethyl acetate to give the title compound 162 (0.88 g, 63%) as fine white crystals. M.p. 163–165 °C. 1H NMR
(300 MHz, CDCl3): δ 7.43–7.27 (7H, m, ArH), 7.17 (1H, d, J = 8.3 Hz, H5), 7.00 (2H, d, J = 8.8 Hz, H3′,5′), 6.88 (1H, br s, H4), 6.79 (1H, dd, J = 2.2 Hz, 8.3 Hz, H6), 6.73 (1H, d, J = 2.2 Hz, H8), 6.22 (1H, s, H2), 4.00 (1H, d, J = 13.6 Hz, SCHaPh), 3.77 (1H, b 13 d, J = 13.6 Hz, SCH Ph), 2.31 (3H, s, COCH3), 2.30 (3H, s, COCH3). C NMR (75
MHz, CDCl3): δ 169.5 (CO), 169.3 (CO), 151.7 (ArC), 150.8 (ArC), 150.6 (ArC), 137.9 (ArC), 133.1 (ArC), 130.1 (ArC), 129.4 (ArC), 128.8 (ArC), 127.7 (ArC), 127.4 (ArC), 126.5 (ArC), 122.0 (ArC), 121.4 (ArC), 121.3 (ArC), 116.0 (ArC), 111.2 (ArC), 81.2
(C2), 35.2 (SCH2Ph), 21.4 (COCH3). IR (KBr): νmax 3433 (w), 3065 (w), 3026 (w), 2931 (w), 1763 (s), 1603 (m), 1584 (w), 1572 (w), 1506 (m), 1489 (m), 1454 (w), 1426 (m), 1369 (m), 1307 (w), 1283 (w), 1254 (m), 1206 (s), 1198 (s), 1167 (s), 1134 (s), 1106 (s), 1029 (m), 1015 (m), 980 (s), 915 (m), 900 (m), 871 (w), 844 (m), 771 (m) cm- 1 -1 -1 . UV-vis (MeOH): λmax 331 nm (ε 15,985 cm M ), 238 (16,007), 207 (27,784). + HRMS (+ESI): Found m/z 469.1072, [M+Na] ; C26H22O5SNa required 469.1080.
4-(7-Acetoxy-2-((4-chlorophenyl)thio)-2H-chromen-3-yl)phenyl acetate (163) 4-Chlorothiophenol (200 mg, 1.38 mmol) was added to Cl a suspension of isoflavylium salt 55 (500 mg, 1.07 3" 5" mmol) in dichloromethane (30 mL). The mixture was 2" 6" 8 2 stirred at room temperature for 18 hours before being AcO O S 3 2' quenched with water (50 mL). The dichloromethane 6 3' 5 4 layer was collected, dried over MgSO4 and evaporated 6' OAc 5' in vacuo to give a pink amorphous solid. The crude product was recrystallised from ethyl acetate to give the title compound 163 (411 mg, 1 64%) as small pink plates. M.p. 108–111 °C. H NMR (300 MHz, CDCl3): δ 7.63 (2H, d, J = 8.7 Hz, H2′,6′), 7.45 (2H, d, J = 8.5 Hz, H3″,5″), 7.29 (2H, d, J = 8.5 Hz, H2″,6″), 7.21–7.13 (3H, m, H5, H3′,5′), 6.90 (1H, br s, H4), 6.82–6.77 (2H, m, H6, H8), 6.58 13 (1H, s, H2), 2.33 (3H, s, COCH3), 2.31 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.1 (CO), 151.6 (ArC), 150.7 (ArC), 150.5 (ArC), 134.6 (ArC), 134.5 (ArC), 133.2 (ArC), 131.9 (ArC), 129.7 (ArC), 129.4 (ArC), 129.1 (ArC), 127.6 (ArC),
‐ 142 ‐ 126.6 (ArC), 122.1 (ArC), 121.9 (ArC), 121.0 (ArC), 116.1 (ArC), 111.1 (ArC), 85.9
(C2), 21.4 (COCH3). IR (KBr): νmax 3436 (m), 1754 (s), 1612 (m), 1510 (m), 1496 (m), 1473 (m), 1432 (w), 1370 (m), 1216 (s), 1170 (m), 1137 (m), 1112 (s), 1093 (w), 1050 -1 -1 -1 (w), 1014 (w), 977 (w), 849 (w) cm . UV-vis (MeOH): λmax 326 nm (ε 10,350 cm M ), 307 (9,572), 242 (13,440), 206 (20,756). HRMS (+ESI): Found m/z 489.0527, [M+Na]+;
C25H19ClO5SNa required 489.0534.
2-(Ethylthio)-3-(4-hydroxyphenyl)-2H-chromen-7-ol (164)
8 The isoflavene 161 (161 mg, 0.42 mmol) and imidazole HO O 2 S
(273 mg, 4.01 mmol) were dissolved in ethanol (5 mL). 3 2' 6 3' The mixture was heated at reflux, under nitrogen, for 3 5 4 6' OH hours. Once cooled, the reaction mixture was poured into 5' water (80 mL). Filtration afforded the title compound 164 (123 mg, 97%) as an off- 1 white powder. M.p. 175–182 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.66 (1H, br s, OH), 9.54 (1H, br s, OH), 7.37 (2H, d, J = 8.7 Hz, H2′,6′), 7.09 (1H, d, J = 8.1 Hz, H5), 6.94 (1H, br s, H4), 6.78 (2H, d, J = 8.7 Hz, H3′,5′), 6.55–6.32 (2H, m, H6,
H8), 6.00 (1H, s, H2), 3.95-3.63 (2H, m, SCH2CH3), 1.12 (3H, dd (app t), J = 7.3 Hz, 13 SCH2CH3). C NMR (75 MHz, d6-DMSO): δ 158.3 (ArC), 156.9 (ArC), 150.9 (ArC), 131.6 (ArC), 127.7 (ArC), 127.3 (ArC), 126.7 (ArC), 126.1 (ArC), 118.4 (ArC), 115.5
(ArC), 113.9 (ArC), 109.2 (ArC), 96.2 (C2), 62.7 (CH2CH3), 15.2 (CH2CH3). IR (KBr):
νmax 3417 (s), 3033 (w), 2943 (w), 1617 (s), 1514 (s), 1463 (m), 1401 (w), 1374 (w), 1289 (w), 1249 (s), 1227 (s), 1183 (w), 1162 (m), 1154 (m), 1118 (m), 1022 (m), 956 -1 -1 -1 (m), 943 (w), 914 (w), 833 (m) cm . UV-vis (MeOH): λmax 324 nm (ε 6,893 cm M ), + 212 (5,391). HRMS (+ESI): Found m/z 323.3603, [M+Na] ; C17H17O3SNa required 323.3614.
2-(Benzylthio)-3-(4-hydroxyphenyl)-2H-chromen-7-ol (165) The isoflavene 162 (50 mg, 0.11 mmol) and imidazole 3" 2" 4" (47 mg, 0.69 mmol) were dissolved in acetone (5 mL). 5" 8 6" The mixture was heated at reflux for 5 hours. Once HO O 2 S cooled, the reaction mixture was poured into water (50 3 2' 6 3' mL). Filtration afforded the title compound 165 (15 mg, 5 4 6' OH 38%) as a pale pink powder. M.p. 110–114 °C (decomp.). 5' 1 H NMR (300 MHz, d6-DMSO): δ 9.69 (1H, br s, OH), 9.57 (1H, br s, OH), 7.38–7.26
‐ 143 ‐ (5H, m, ArH), 7.24 (2H, d, J = 8.8 Hz, H2′,6′), 7.03 (1H, d, J = 8.4 Hz, H5), 6.91 (1H, br s, H4), 6.69 (2H, d, J = 8.8 Hz, H3′,5′), 6.46 (1H, br s, H2), 6.44 (1H, dd, J = 2.2 Hz, 8.4 Hz, H6), 6.32 (1H, d, J = 2.2 Hz, H8), 3.98 (1H, d, J = 13.1 Hz, SCHaPh), 3.91 (1H, b 13 d, J = 13.1 Hz, SCH Ph). C NMR (75 MHz, CDCl3): δ 158.6 (ArC), 157.1 (ArC), 150.5 (ArC), 138.4 (ArC), 137.3 (ArC), 129.4 (ArC), 129.0 (ArC), 128.4 (ArC), 127.6 (ArC), 127.3 (ArC), 126.8 (ArC), 126.1 (ArC), 125.9 (ArC), 118.7 (ArC), 115.4 (ArC),
109.7 (ArC), 104.1 (ArC), 81.4 (C2), 34.3 (SCH2Ph). IR (KBr): νmax 3427 (s), 1614 (s), 1592 (m), 1514 (s), 1454 (m), 1374 (w), 1284 (s), 1246 (s), 1180 (m), 1150 (s), 1115 (s), -1 1030 (w), 975 (m), 831 (s), 762 (w), 701 (m) cm . UV-vis (MeOH): λmax 324 nm (ε 4,023 cm-1M-1), 211 (4,277). HRMS (+ESI): Found m/z 385.0867, [M+Na]+;
C22H18O3SNa required 385.0869.
2-((4-Chlorophenyl)thio)-3-(4-hydroxyphenyl)-2H-chromen-7-ol (166) 4-Chlorothiophenol (150 mg, 1.04 mmol) was added to a Cl suspension of isoflavylium salt 117 (250 mg, 1.30 mmol) 3" 5" in glacial acetic acid (5 mL). The mixture was stirred at 2" 6" 8 room temperature for one hour before being quenched HO O 2 S 3 2' with water. Filtration afforded the crude product as a dark 6 3' 5 4 pink solid, which was recrystallised from acetonitrile to 6' OH 5' give the title compound 166 (198 mg, 50 %) as a pink 1 powder. M.p. 208–211 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.85 (1H, br s, OH), 9.53 (1H, br s, OH), 7.54 (2H, d, J = 8.9 Hz, H3″,5″), 7.47 (2H, d, J = 8.9 Hz, H2″,6″), 7.24 (2H, d, J = 8.8 Hz, H2′,6′), 7.11 (1H, d, J = 8.4 Hz, H5), 7.02 (1H, br s, H4), 6.66 (1H, br s, H2), 6.65 (1H, d, J = 2.3 Hz, H8), 6.60 (2H, d, J = 8.8 Hz, H3′,5′), 13 6.50 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6). C NMR (75 MHz, d6-DMSO): δ 158.6 (ArC), 156.9 (ArC), 150.2 (ArC), 134.5 (ArC), 132.5 (ArC), 129.5 (ArC), 129.2 (ArC), 127.9 (ArC), 126.5 (ArC), 126.1 (ArC), 125.2 (ArC), 118.8 (ArC), 115.3 (ArC), 113.6 (ArC),
109.8 (ArC), 103.4 (ArC), 91.3 (C2). IR (KBr): νmax 3317 (s), 3076 (w), 1658 (w), 1615 (s), 1516 (s), 1469 (s), 1385 (m), 1323 (w), 1284 (s), 1253 (s), 1182 (m), 1153 (s), 1121 (m), 1094 (m), 1062 (w), 1018 (w), 1011 (m), 977 (m), 955 (s), 940 (m), 907 (s), 886 -1 -1 -1 (m), 828 (s), 816 (s), 742 (w) cm . UV-vis (MeOH): λmax 323 nm (ε 10,829 cm M ), 241 (10,064), 206 (15,040). HRMS (+ESI): Found m/z 405.0311, [M+Na]+;
C21H15ClO3SNa required 405.0328.
‐ 144 ‐ 3-(4-Hydroxyphenyl)-2-(propylthio)-2H-chromen-7-ol (167)
8 1-Propanethiol (0.10 mL, 1.1 mmol) was added to a HO O 2 S suspension of isoflavylium salt 117 (250 mg, 1.30 mmol) 3 2' 6 3' in glacial acetic acid (5 mL). The mixture was stirred at 5 4 6' OH room temperature for one hour before being quenched 5' with water. Filtration afforded the crude product as a dark pink solid, which was recrystallised from acetonitrile to give the title compound 167 (204 mg, 65%) as a pink 1 powder. M.p. 144–149 °C (decomp.). H NMR (300 MHz, d6-DMSO) δ 9.66 (1H, br s, OH), 9.58 (1H, br s, OH), 7.46 (2H, d, J = 8.7 Hz, H2′,6′), 7.04 (1H, d, J = 8.3 Hz, H5), 6.88 (1H, br s, H4), 6.78 (2H, d, J = 8.7 Hz, H3′,5′), 6.65 (1H, br s, H2), 6.44 (1H, dd, J
= 2.4 Hz, 8.3 Hz, H6), 6.33 (1H, d, J = 2.4 Hz, H8), 2.73–2.61 (2H, m, SCH2CH2CH3), 13 1.67–1.55 (2H, m, SCH2CH2CH3), 0.90 (3H, t, J = 7.1 Hz, SCH2CH2CH3). C NMR
(75 MHz, d6-DMSO): δ 158.5 (ArC), 156.6 (ArC), 150.2 (ArC), 132.9 (ArC), 129.1 (ArC), 126.1 (ArC), 126.0 (ArC), 118.8 (ArC), 115.3 (ArC), 113.8 (ArC), 103.7 (ArC),
82.0 (C2), 54.5 (CH2CH2CH3), 24.5 (CH2CH2CH3), 11.9 (CH2CH2CH3). IR (KBr):
νmax 3415 (s), 2961 (w), 2907 (w), 1614 (s), 1514 (s), 1462 (m), 1377 (w), 1354 (w), 1286 (m), 1247 (s), 1180 (m), 1151 (s), 1120 (m), 976 (w), 959 (m), 941 (w), 907 (m), -1 -1 -1 829 (m) cm . UV-vis (MeOH): λmax 325 nm (ε 18,778 cm M ), 308 (17,206), 211 + (19,681). HRMS (+ESI): Found m/z 315.1046, [M+H] ; C18H19O3S required 315.1049.
4-(7-Acetoxy-2-(3-methyl-1H-indol-2-yl)-2H-chromen-3-yl)phenyl acetate (170) 3-Methylindole (31 mg, 0.24 mmol) was added to a 6" 5" suspension of isoflavylium salt 55 (100 mg, 0.21 mmol) 4" 8 AcO O 2 in dichloromethane (10 mL). The mixture was stirred at N 3" 3 H 2' room temperature for 22 hours before the solvent was 6 3' 5 4 evaporated in vacuo to give a brown amorphous solid. 6' OAc 5' The crude product was recrystallised from ethyl acetate to give the title compound 170 (34 mg, 36%) as small, pale orange crystals. M.p. 205– 1 206 °C. H NMR (300 MHz, CDCl3): δ 7.90 (1H, br s, NH), 7.57 (1H, d, J = 8.0 Hz, Indole ArH), 7.36 (2H, d, J = 8.7 Hz, H2′,6′), 7.21 (1H, d, J = 8.4 Hz, H5), 7.17–7.13 (2H, m, indole ArH), 7.12–7.07 (2H, m, H4, indole ArH), 7.01 (2H, d, J = 8.7 Hz, H3′,5′), 6.70 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 6.55 (1H, d, J = 2.3 Hz, H8), 6.51 (1H, br 13 s ,H2), 2.49 (3H, s, CH3), 2.28 (3H, s, COCH3), 2.23 (3H, s, COCH3). C NMR (75
MHz, CDCl3) δ 169.1 (CO), 168.9 (CO), 152.0 (ArC), 151.1 (ArC), 150.1 (ArC), 135.4
‐ 145 ‐ (ArC), 133.8 (ArC), 131.4 (ArC), 129.2 (ArC), 128.4 (ArC), 128.0 (ArC), 126.3 (ArC ), 122.1 (ArC), 121.9 (ArC), 121.0 (ArC), 119.8 (ArC), 118.5 (ArC), 114.7 (ArC), 111.7
(ArC), 109.4 (ArC), 109.0 (ArC), 69.8 (C2), 20.8 (COCH3), 8.4 (CH3). IR (KBr): νmax 3411 (m), 3031 (w), 2919 (w), 1764 (s), 1651 (w), 1611 (m), 1584 (w), 1510 (m), 1495 (m), 1455 (w), 1428 (w), 1370 (m), 1334 (w), 1306 (w), 1267 (w), 1257 (w), 1207 (s), 1172 (s), 1141 (s), 1116 (m), 1017 (m), 977 (w), 936 (w), 910 (m), 886 (w), 842 (w), -1 -1 -1 739 (m) cm . UV-vis (MeOH): λmax 294 nm (ε 6,893 cm M ), 224 (14,013), 208 + (13,741). HRMS (+ESI): Found m/z 454.1645, [M+H] ; C28H24NO5 required 454.1649.
4-(7-Acetoxy-2-(3-(cyanomethyl)-1H-indol-2-yl)-2H-chromen-3-yl)phenyl acetate (171) Indole-3-acetonitrile (36 mg, 0.23 mmol) was added to 6" 5" a suspension of isoflavylium salt 55 (100 mg, 0.21 NC 4" 8 AcO O 2 mmol) in dichloromethane (20 mL). The mixture was N 3" 3 H 2' stirred at room temperature for 19 hours before the 6 3' 5 4 solvent was evaporated in vacuo to give a brown 6' OAc 5' amorphous solid. The crude product was recrystallised from aqueous methanol to give the title compound 171 (42 mg, 42%) as a light brown 1 powder. M.p. 206–208 °C. H NMR (300 MHz, CDCl3): δ 7.81 (1H, br d, J = 8.5 Hz, Indole ArH), 7.58 (1H, ddd, J = 0.8 Hz, 1.1 Hz, 8.0 Hz, indole ArH), 7.42 (1H, ddd, J = 1.1 Hz, 7.1 Hz, 8.0 Hz, indole ArH), 7.39 (1H, br s, NH), 7.34–7.26 (5H, m, H4, H5, H2′,6′, indole ArH), 7.04 (2H, d, J = 8.8 Hz, H3′,5′), 7.00 (1H, br s ,H2), 6.79 (1H, dd, J
= 2.3 Hz, 8.3 Hz, H6), 6.59 (1H, d, J = 2.3 Hz, H8), 3.66 (2H, s, CH2CN), 2.28 (3H, s, 13 COCH3), 2.22 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.1 (CO), 168.8 (CO), 151.5 (C7), 150.5 (C8a), 150.4 (C4′), 135.5 (ArC), 132.7 (ArC), 128.5 (ArC), 127.4 (ArC), 126.5 (ArC), 126.3 (C2′,6′), 123.5 (ArC), 123.2 (C4), 122.9 (C4a), 122.4 (C3′, 5′), 120.8 (ArC), 119.0 (ArC or CN), 118.7 (ArC or CN), 118.6 (ArC or CN), 110.1
(ArC), 106.4 (ArC), 77.7 (C2), 20.8 (COCH3), 13.1 (CH2CN). IR (KBr): νmax 3435 (m), 1755 (s), 1612 (m), 1585 (w), 1512 (m), 1496 (w), 1458 (s), 1432 (w), 1410 (w), 1371 (m), 1351 (w), 1258 (w), 1213 (s), 1198 (s), 1174 (s), 1140 (m), 1113 (m), 1045 (w), -1 1021 (m), 978 (w), 906 (m), 851 (w), 743 (m) cm . UV-vis (MeOH): λmax 283 nm (ε 4,546 cm-1M-1), 219 (7,417). HRMS (+ESI): Found m/z 479.1595, [M+H]+;
C29H23N2O5 required 479.1601.
‐ 146 ‐ 3-(4-Hydroxyphenyl)-2-(3-methyl-1H-indol-2-yl)-2H-chromen-7-ol (172) The isoflavene 170 (25 mg, 0.055 mmol) was suspended 6" 5" in methanol (5 mL). Aqueous KOH (1 M, 0.4 mL, 0.4 4" 8 HO O 2 mmol) was added dropwise. The mixture was stirred at N 3" H 3 2' room temperature for 48 hours before being neutralised 6 5 4 3' with 1 M HCl. Water (15 mL) was added. Filtration 6' OH 5' afforded the title compound 172 (12 mg, 59%) as a light 1 brown powder. M.p. 168–172 °C (decomp.). H NMR (300 MHz, d6-DMSO) δ 10.39 (1H, br s, NH), 9.49 (1H, br s, OH), 9.45 (1H, br s OH), 7.42 (1H, br d, J = 7.7 Hz, indole ArH), 7.29 (2H, d, J = 8.8 Hz, H2′,6′), 7.23 (1H, br d, J = 7.7 Hz, indole ArH), 7.07–6.97 (3H, m, H4, H5, indole ArH), 6.95–6.89 (1H, m, indole ArH), 6.68 (2H, d, J = 8.8 Hz, H3′,5′), 6.57 (1H, br s, H2), 6.31 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.09 (1H, d, 13 J = 2.3 Hz, H8), 2.31 (3H, s, CH3). C NMR (75 MHz, d6-DMSO) δ 157.9 (ArC), 154.6 (ArC), 151.9 (ArC), 145.4 (ArC), 143.6 (ArC), 141.8 (ArC), 138.3 (ArC), 132.9 (ArC), 130.0 (ArC), 128.5 (ArC), 126.1 (ArC), 122.9 (ArC), 121.1 (ArC), 118.1 (ArC),
117.8 (ArC), 115.3 (ArC), 109.5 (ArC), 106.8 (ArC), 72.4 (C2), 8.8 (CH3). IR (KBr):
νmax 3389 (s), 2928 (w), 1612 (s), 1556 (w), 1515 (s), 1504 (m), 1487 (m), 1454 (s), 1382 (w), 1359 (w), 1335 (m), 1238 (s), 1174 (s), 1151 (s), 1114 (m), 1025 (w), 976 (w), -1 -1 -1 835 (m), 747 (m) cm . UV-vis (MeOH): λmax 287 nm (ε 5,702 cm M ), 203 (16,947). + HRMS (+ESI): Found m/z 392.1259, [M+H] ; C24H19NO3Na required 392.1263.
2-(2-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-1H-indol-3-yl)acetonitrile (173) The isoflavene 171 (25 mg, 0.052 mmol) was suspended 6" 5" in methanol (5 mL). Aqueous KOH (1 M, 0.4 mL, 0.4 NC 4" 8 HO O 2 mmol) was added dropwise. The mixture was stirred at N 3" 3 H 2' room temperature for 48 hours before being neutralised 6 5 4 3' with 1 M HCl. Water (15 mL) was added. Filtration 6' OH 5' afforded the title compound 173 (12 mg, 59%) as a 1 pinkish brown powder. M.p. 167–169 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.67 (1H, br s, OH), 9.59 (1H, br s OH), 8.04 (1H, br d, J = 8.3 Hz, indole ArH), 7.68 (1H, br s, NH), 7.56 (1H, br d, J = 7.9 Hz, indole ArH), 7.41 (1H, br s, H4), 7.38–7.27 (3H, m, H2′,6′, indole ArH), 7.25–7.16 (2H, m, H5, indole ArH), 7.03 (1H, br s, H2), 6.70 (2H, d, J = 8.8 Hz, H3′,5′), 6.44 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.12 (1H, d, J =
‐ 147 ‐ 13 2.3 Hz, H8), 3.92 (2H, br s, CH2CN). C NMR (75 MHz, d6-DMSO): δ 158.9 (ArC), 156.6 (ArC), 151.8 (ArC), 145.3 (ArC), 143.9 (ArC), 141.6 (ArC), 137.6 (ArC), 131.1 (ArC), 130.0 (ArC), 128.2 (ArC), 126.6 (ArC), 123.1 (ArC), 119.7 (ArC), 116.6 (ArC or CN), 116.1 (ArC or CN), 114.9 (ArC or CN), 109.8 (ArC), 105.5 (ArC), 73.9 (C2),
17.1 (CH2CN). IR (KBr): νmax 3434 (s), 2963 (w), 2916 (w), 2845 (w), 1753 (m), 1736 (w), 1701 (m), 1676 (m), 1655 (s), 1638 (s), 1629 (m), 1618 (s), 1561 (m), 1545 (w), 1509 (m), 1439 (w), 1411 (w), 1370 (w), 1262 (s), 1213 (s), 1174 (s), 1141 (s), 1112 (s), -1 1095 (s), 1023 (s), 905 (w), 852 (w), 802 (s), 741 (w) cm . UV-vis (MeOH): λmax 346 nm (ε 5,028 cm-1M-1), 265 (4,733), 205 (16,271). HRMS (+ESI): Found m/z 395.1388, + [M+H] ; C25H19N2O3 required 395.1390.
4-(7-Acetoxy-2-(2-phenyl-1H-indol-3-yl)-2H-chromen-3-yl)phenyl acetate (174) 2-Phenylindole (46 mg, 0.23 mmol) was added to a suspension of isoflavylium salt 55 (100 mg, 0.21 mmol) NH 8 4" in dichloromethane (5 mL). The mixture was stirred at AcO O 2 5" 3 room temperature for 19 hours before the solvent was 6 evaporated in vacuo to give a brown amorphous solid. 5 4 2' OAc The crude product was recrystallised from ethyl acetate 3' to give the title compound 174 (52 mg, 48%) as a dark purple powder. M.p. 231–233 °C 1 (decomp.). H NMR (300 MHz, CDCl3): δ 7.81 (1H, br d, J = 8.5 Hz, indole ArH), 7.58 (1H, ddd, J = 0.8 Hz, 1.1 Hz, 8.0 Hz, indole ArH), 7.42 (1H, ddd, J = 1.1 Hz, 7.1 Hz, 8.0 Hz, indole ArH), 7.39 (1H, br s, NH), 7.34–7.26 (5H, m, H4, H5, H2′,6′, indole ArH), 7.04 (2H, d, J = 8.8 Hz, H3′,5′), 7.00 (1H, br s ,H2), 6.79 (1H, dd, J = 2.3 Hz, 8.3
Hz, H6), 6.59 (1H, d, J = 2.3 Hz, H8), 3.66 (2H, s, CH2CN), 2.28 (3H, s, COCH3), 2.22 13 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.3 (CO), 169.2 (CO), 153.8 (ArC), 151.3 (ArC), 149.9 (ArC), 138.5 (ArC), 135.9 (ArC), 132.2 (ArC), 129.0 (ArC), 128.9 (ArC), 127.2 (ArC), 126.6 (ArC), 124.5 (ArC), 122.5 (ArC), 121.2 (ArC), 120.6 (ArC),
114.2 (ArC), 111.3 (ArC), 109.6 (ArC), 72.7 (C2), 21.2 (COCH3), 21.1 (COCH3). IR
(KBr): νmax 3433 (m), 1755 (s), 1650 (w), 1632 (m), 1613 (m), 1504 (m), 1494 (m), 1426 (m), 1371 (m), 1200 (s), 1164 (s), 1138 (s), 1110 (s), 1029 (m), 1014 (m), 981 (w), -1 -1 -1 913 (w), 743 (w) cm . UV-vis (MeOH): λmax 300 nm (ε 6,280 cm M ), 206 (12,724). + HRMS (+ESI): Found m/z 516.1800, [M+H] ; C33H26NO5 required 516.1805.
‐ 148 ‐ 4-(7-Acetoxy-2-(5-acetyl-1H-pyrrol-2-yl)-2H-chromen-3-yl)phenyl acetate (175) 2-Acetylpyrrole (27 mg, 0.25 mmol) was added to a O suspension of isoflavylium salt 55 (100 mg, 0.21 mmol) HN 8 in dichloromethane (10 mL). The mixture was stirred at AcO O 2 4" 5" 3 2' room temperature for 22 hours before the solvent was 6 3' evaporated in vacuo to give a brown amorphous solid. 5 4 6' OAc The crude product was recrystallised from ethyl acetate 5' to give the title compound 175 (34 mg, 38%) as small beige crystals. M.p. 255–259 °C 1 (decomp.). H NMR (300 MHz, CDCl3): δ 9.12 (1H, br s, NH), 7.44 (2H, d, J = 8.8 Hz, H2′,6′), 7.14 (1H, d, J = 8.2 Hz, H5), 7.07 (2H, d, J = 8.8 Hz, H3′,5′), 6.98 (1H, br s, H4), 6.95–6.91 (1H, m, H4″), 6.88–6.85 (1H, m, H5″), 6.66 (1H, dd, J = 2.2 Hz, 8.2 Hz,
H6), 6.57 (1H, d, J = 2.3 Hz, H8), 6.19 (1H, br s, H2), 2.36 (3H, s, COCH3), 2.30 (3H, s, 13 COCH3), 2.25 (3H, s, COCH3). C NMR (75 MHz, d6-DMSO): δ 187.1 (CO), 169.1 (CO), 168.9 (CO), 151.7 (ArC), 151.0 (ArC), 150.1 (ArC), 133.8 (ArC), 132.2 (ArC), 132.1 (ArC), 127.4 (ArC), 126.4 (ArC), 124.7 (ArC), 122.7 (ArC), 122.1 (ArC), 120.7
(ArC), 118.9 (ArC), 114.7 (ArC), 110.2 (ArC), 93.4 (ArC), 70.7 (C2), 25.6 (COCH3),
20.1 (COCH3). IR (KBr): νmax 3441 (m), 3277 (m), 1758 (s), 1641 (s), 1562 (m), 1509 (m), 1493 (w), 1433 (w), 1397 (m), 1370 (w), 1248 (w), 1212 (s), 1190 (s), 1168 (s), -1 1137 (s), 1112 (s), 1022 (m), 946 (w), 851 (w), 733 (s) cm . UV-vis (MeOH): λmax 333 nm (ε 5,393 cm-1M-1), 291 (6,471), 205 (11,110). HRMS (+ESI): Found m/z 432.1434, + [M+H] ; C25H22NO6 required 432.1442.
1-(5-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-1H-pyrrol-2-yl)ethanone (176) The isoflavene 175 (25 mg, 0.058 mmol) was suspended O in methanol (5 mL). Aqueous KOH (1 M, 0.4 mL, 0.4 HN 8 mmol) was added dropwise. The mixture was stirred at HO O 2 4" 5" 3 2' room temperature for 48 hours before being neutralised 6 3' with 1 M HCl. Water (15 mL) was added. Filtration 5 4 6' OH afforded the title compound 176 (13 mg, 65%) as a light 5' 1 brown powder. M.p. 142–145 °C. H NMR (300 MHz, d6-DMSO): δ 11.67 (1H, br s, NH), 9.52 (1H, br s, OH), 9.44 (1H, br s OH), 7.33 (2H, d, J = 8.7 Hz, H2′,6′), 7.00 (1H, d, J = 8.3 Hz, H5), 6.93 (1H, br s, H4), 6.85–6.81 (2H, m, H4″, H5″), 6.72 (2H, d, J = 8.7 Hz, H3′,5′), 6.29 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 6.20 (1H, br s, H2), 6.13 (1H, d,
‐ 149 ‐ 13 J = 2.3 Hz, H8), 2.24 (3H, s, COCH3). C NMR (75 MHz, d6-DMSO): δ 187.0 (CO), 158.2 (ArC), 156.9 (ArC), 152.0 (ArC), 133.8 (ArC), 132.0 (ArC), 132.1 (ArC), 129.8 (ArC), 126.1 (ArC), 124.5 (ArC), 122.6 (ArC), 116.5 (ArC), 115.8 (ArC), 115.4 (ArC),
114.4 (ArC), 109.8 (ArC), 103.3 (ArC), 70.7 (C2), 25.5 (COCH3). IR (KBr): νmax 3417 (s), 2924 (w), 1703 (w), 1697 (w), 1614 (s), 1556 (w), 1514 (s), 1504 (m), 1462 (m), 1454 (w), 1402 (m), 1368 (w), 1286 (m), 1265 (m), 1177 (m), 1152 (s), 1115 (s), 1025 -1 -1 -1 (w), 965 (w), 944 (w), 834 (m) cm . UV-vis (MeOH): λmax 333 nm (ε 9,292 cm M ), 294 (11,515), 251 (7,850), 203 (14,745). HRMS (+ESI): Found m/z 348.1225, [M+H]+;
C21H18NO4 required 348.1230.
4-(7-Acetoxy-2-(2-oxopropyl)-2H-chromen-3-yl)phenyl acetate (177) Diacetoxyphenoxodiol 109 (5.01 g, 15.4 mmol) and O 8 tritylium hexafluorophosphate (6.61 g, 17.0 mmol) AcO O 2
3 2' were dissolved in dichloromethane (250 mL). The 6 3' 5 4 mixture was stirred at room temperature for 30 minutes. 6' OAc Filtration afforded the isoflavylium salt 55 as a bright 5' yellow solid, which was immediately dissolved in acetone (250 mL). The mixture was stirred at room temperature for 18 hours. Solvent was evaporated in vacuo and the crude product recrystallised from ethyl acetate to give the title compound 177 (3.98 g, 68%) as 1 an off-white solid. M.p. 143–145 °C. H NMR (300 MHz, CDCl3): δ 7.49 (2H, d, J = 8.7, H2′,6′), 7.12 (2H, d, J = 8.7 Hz, H3′,5′), 7.10 (1H, d, J = 8.3 Hz, H5), 6.76 (1H, br s, H4), 6.70 (1H, dd, J = 2.4 Hz, 8.3 Hz, H6), 6.62 (1H, d, J = 2.4 Hz, H8), 5.93 (1H, dd, J a = 2.1 Hz, 10.2 Hz, H2), 3.16 (1H, dd, J = 10.2 Hz, 16.5 Hz, CH COCH3), 2.36 (1H, dd, b J = 2.1 Hz, 16.5 Hz, CH COCH3), 2.32 (3H, s, COCH3), 2.29 (3H, s, COCH3), 2.17 13 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 205.8 (CO), 169.4 (CO), 169.2 (CO), 151.5 (ArC), 151.4 (ArC), 150.6 (ArC), 133.6 (ArC), 133.2 (ArC), 127.4 (ArC), 126.4 (ArC), 122.2 (ArC), 120.1 (ArC), 119.4 (ArC), 115.1 (ArC), 110.4 (ArC), 72.6 (C2),
45.9 (CH2), 31.1 (COCH3), 20.1 (COCH3). IR (KBr): νmax 3415 (w), 3057 (w), 2961 (w), 1765 (s), 1715(s), 1629 (w), 1607 (w), 1584 (w), 1511 (m), 1496 (m), 1431 (w), 1368 (m), 1258 (w), 1227 (m), 1207 (s), 1194 (s), 1173 (s), 1141 (s), 1115 (m), 1066 -1 (w), 1014 (m), 949 (w), 905 (m), 849 (m), 750 (w) cm . UV-vis (MeOH): λmax 330 nm (ε 10,093 cm-1M-1), 240 (10,169), 205 (14,544). HRMS (+ESI): Found m/z 403.1154, + [M+Na] ; C22H20O6Na required 403.1152.
‐ 150 ‐ 1-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)propan-2-one (178) The isoflavene 177 (370 mg, 0.97 mmol) was suspended O 8 in methanol (10 mL). Aqueous KOH (1 M, 3.0 mL, 3.0 HO O 2
3 2' mmol) was added dropwise. The mixture was stirred at 6 3' 5 4 room temperature for 48 hours before being neutralised 6' OH with 1 M HCl. Water (15 mL) was added. Filtration 5' afforded the title compound 178 (218 mg, 72%) as a greenish yellow powder. M.p. 174– 1 177 °C. H NMR (300 MHz, d6-DMSO): δ 9.59 (1H, br s, OH), 9.57 (1H, br s, OH), 7.35 (2H, d, J = 8.8, H2′,6′), 6.97 (1H, d, J = 8.4 Hz, H5), 6.77 (1H, br s, H4), 6.76 (2H, d, J = 8.8 Hz, H3′,5′), 6.34 (1H, dd, J = 2.3 Hz, 8.4 Hz, H6), 6.18 (1H, d, J = 2.3 Hz, H8), 6.74 (dd, J = 2.3 Hz, 10.1 Hz, H2), 2.89 (1H, dd, J = 10.1 Hz, 15.9 Hz, a b CH COCH3), 2.36 (1H, dd, J = 2.3 Hz, 15.9 Hz, CH COCH3), 2.13 (3H, s, COCH3). 13 C NMR (75 MHz, d6-DMSO): δ 205.9 (CO), 158.4 (ArC), 157.2 (ArC), 151.2 (ArC), 130.0 (ArC), 127.5 (ArC), 126.6 (ArC), 126.0 (ArC), 116.6 (ArC), 115.7 (ArC), 114.4
(ArC), 108.9 (ArC), 103.3 (ArC), 71.8 (C2), 45.7 (CH2), 30.3 (COCH3). IR (KBr): νmax 3359 (s), 3038 (w), 2960 (w), 1704 (s), 1619 (s), 1584 (m), 1517 (s), 1506 (s), 1459 (m), 1447 (m), 1372 (w), 1356 (m), 1336 (m), 1288 (m), 1269 (s), 1232 (m), 1186 (m), 1159 (s), 1148 (s), 1114 (s), 1063 (w), 1043 (w), 1006 (w), 952 (w), 916 (w), 874 (w), 845 -1 (m), 836 (m), 816 (w), 792 (w), 736 (w) cm . UV-vis (MeOH): λmax 333 nm (ε 12,813 cm-1M-1), 242 (8,629), 211 (14,176). HRMS (+ESI): Found m/z 297.1117, [M+H]+;
C18H17O4 required 297.1121.
1-(7-Hydroxy-3-(4-hydroxyphenyl)-4-(4-methoxyphenyl)-2H-chromen-2- yl)propan-2-one (179) The isoflavylium salt 121 (50 mg, 0.13 mmol) was O 8 dissolved in acetone (25 mL) and stirred at room HO O 2
3 2' temperature for 3 days. Solvent was evaporated in vacuo 6 3' 4 to a volume of approximately 5 mL. Filtration afforded 5 2" 6' OH the title compound 179 (38 mg, 72%) as a dark green 5' 3" 1 solid. M.p. 99–104 °C (decomp.). H NMR (300 MHz, OMe d6-acetone): δ 8.56 (1H, br s, OH), 8.35 (1H, br s, OH), 7.05 (2H, d, J = 8.4 Hz, H2″,6″), 6.98 (2H, d, J = 8.7, H2′,6′), 6.86 (2H, d, J = 8.4 Hz, H3″,5″), 6.66 (1H, d, J = 8.4 Hz, H5), 6.64 (2H, d, J = 8.7 Hz, H3′,5′), 6.39–6.30 (3H, m, H6, H8), 5.56 (1H, dd, J = 2.5 a Hz, 10.2 Hz, H2), 3.78 (3H, s, OMe), 3.19 (1H, dd, J = 10.2 Hz, 15.8 Hz, CH COCH3),
‐ 151 ‐ b 13 2.57 (1H, dd, J = 2.5 Hz, 15.8 Hz, CH COCH3), 2.15 (3H, s, COCH3). C NMR (75
MHz, d6-acetone): δ 205.6 (CO), 159.5 (ArC), 159.3 (ArC), 156.9 (ArC), 153.4 (ArC), 132.2 (ArC), 131.6 (ArC), 131.3 (ArC), 130.4 (ArC), 130.3 (ArC), 130.1 (ArC), 127.9 (ArC), 117.8 (ArC), 115.6 (ArC), 114.3 (ArC), 109.1 (ArC), 104.4 (ArC), 76.5 (C2),
55.3 (OMe), 46.4 (CH2), 30.6 (COCH3). IR (KBr): νmax 3384 (s), 3033 (w), 2932 (w), 2835 (w), 1701 (w), 1608 (s), 1510 (s), 1455 (m), 1367 (m), 1246 (s), 1172 (s), 1117 -1 (m), 1030 (w), 1012 (w), 971 (w), 832 (m), 794 (w) cm . UV-vis (MeOH): λmax 285 nm (ε 4,165 cm-1M-1), 204 (12,073). HRMS (+ESI): Found m/z 425.1350, [M+Na]+;
C25H22O5Na required 425.1359.
4-(7-Acetoxy-2-(4-methyl-2-oxopentyl)-2H-chromen-3-yl)phenyl acetate (180) 4-Methylpentan-2-one (0.20 mL, 1.6 mmol) was added O 8 to a suspension of isoflavylium salt 55 (500 mg, 1.07 AcO O 2
3 2' mmol) in ethyl acetate (10 mL). The mixture was 6 3' heated at reflux for one hour. Solvent was evaporated 5 4 6' OAc in vacuo and the crude product recrystallised from 5' aqueous methanol to give the title compound 180 (183 mg, 27 %). M.p. 97–101 °C. 1H
NMR (300 MHz, CDCl3): δ 7.49 (2H, d, J = 8.8, H2′,6′), 7.11 (2H, d, J = 8.8 Hz, H3′,5′), 7.09 (1H, d, J = 8.4 Hz, H5), 6.75 (1H, br s, H4), 6.68 (1H, dd, J = 2.3 Hz, 8.4 Hz, H6), 6.58 (1H, d, J = 2.3 Hz, H8), 5.97 (1H, dd, J = 2.3 Hz, 10.1 Hz, H2), 3.14 (1H, a b dd, J = 10.1 Hz, 16.3 Hz, CH CO), 2.35–2.22 (3H, m, CH COCH2), 2.31 (3H, s,
COCH3), 2.28 (3H, s, COCH3), 2.17–2.03 (1H, m, CH2CH(CH3)2), 0.90 (3H, d, J = 6.5 13 Hz, CHCH3), 0.88 (3H, d, J = 6.5 Hz, CHCH3). C NMR (75 MHz, CDCl3): δ 207.6 (CO), 169.3 (CO), 169.2 (CO), 151.5 (ArC), 151.3 (ArC), 150.6 (ArC), 133.5 (ArC), 133.2 (ArC), 127.3 (ArC), 126.3 (ArC), 122.1 (ArC), 120.1 (ArC), 119.3 (ArC), 115.0
(ArC), 110.3 (ArC), 72.6 (C2), 53.0 (CH2), 45.3 (CH2), 24.3 (CH), 22.5 (CH3), 22.4
(CH3), 21.1 (CH3). IR (KBr): νmax 3413 (w), 3065 (w), 2959 (m), 2871 (w), 1759 (s), 1710 (s), 1610 (m), 1585 (w), 1509 (s), 1495 (m), 1467 (w), 1431 (m), 1369 (s), 1312 (w), 1259 (m), 1205 (s), 1170 (s), 1140 (s), 1116 (s), 1072 (w), 1043 (w), 1014 (s), 979 -1 (w), 961 (w), 909 (m), 847 (m), 752 (w) cm . UV-vis (MeOH): λmax 331 nm (ε 10,322 cm-1M-1), 240 (10,083), 205 (16,899). HRMS (+ESI): Found m/z 445.1610, [M+Na]+;
C25H26O6Na required 445.1622.
‐ 152 ‐ 1-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-4-methylpentan-2-one (181) The isoflavene 180 (30 mg, 0.071 mmol) was dissolved O 8 in ethanol (5 mL). Aqueous KOH (1 M, 0.3 mL, 0.3 HO O 2
3 2' mmol) was added dropwise. The mixture was stirred at 6 3' room temperature for 18 hours before being neutralised 5 4 6' OH with 1 M HCl. Water (15 mL) was added. The mixture 5' was extracted with ethyl acetate (3 × 10 mL). The combined extracts were washed with brine (10 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 181 (21 mg, 88%) as a dark brown solid. M.p. 92–96 °C (decomp.). 1H
NMR (300 MHz, d6-DMSO): δ 9.59 (1H, br s, OH), 9.57 (1H, br s, OH), 7.36 (2H, d, J = 8.8, H2′,6′), 6.98 (1H, d, J = 8.4 Hz, H5), 6.81–6.76 (3H, m, H3′,5′, H4), 6.36 (1H, dd, J = 2.3 Hz, 8.4 Hz, H6), 6.17 (1H, d, J = 2.3 Hz, H8), 5.75 (1H, dd, J = 2.5 Hz, 9.9 Hz, H2), 2.91 (1H, dd, J = 9.9 Hz, 15.8 Hz, CHaCO), 2.33 (2H, d, J = 7.1 Hz, b COCH2CH(CH3)2), 2.31–2.20 (3H, m, CH COCH2CH(CH3)2), 0.86 (3H, d, J = 6.5 Hz, 13 CHCH3), 0.84 (3H, d, J = 6.5 Hz, CHCH3). C NMR (75 MHz, d6-DMSO): δ 207.5 (CO), 158.4 (ArC), 157.1 (ArC), 151.1 (ArC), 130.0 (ArC), 127.5 (ArC), 126.5 (ArC), 125.9 (ArC), 116.7 (ArC), 115.6 (ArC), 114.4 (ArC), 108.9 (ArC), 103.1 (ArC), 72.1
(C2), 51.5 (CH2), 45.2 (CH2), 23.7 (CH), 22.4 (CH3), 22.2 (CH3). IR (KBr): νmax 3426 (s), 3952 (w), 1658 (m), 1640 (m), 1619 (s), 1612 (s), 1513 (m), 1502 (w), 1462 (w), -1 1444 (w), 1224 (s), 1150 (s), 1112 (s), 909 (m) cm . UV-vis (MeOH): λmax 271 nm (ε 15,651 cm-1M-1), 203 (14,890). HRMS (+ESI): Found m/z 339.1582, [M+H]+;
C21H23O4 required 339.1591.
4-(7-Acetoxy-2-(2-oxo-2-phenylethyl)-2H-chromen-3-yl)phenyl acetate (183) Acetophenone (0.02 mL, 0.03 mmol) was added to a 3" 2" 4" suspension of isoflavylium salt 55 (100 mg, 0.214 O 5" 8 6" mmol) in ethyl acetate (2 mL). The reaction mixture AcO O 2 was heated at reflux for 30 minutes and stirred at room 3 2' 6 3' temperature for a further 16 hours. Solvent was 5 4 6' OAc evaporated in vacuo and the crude product 5' recrystallised from aqueous methanol to give the title compound 183 (68 mg, 73%) as 1 small white needles. M.p. 158–160 °C. H NMR (300 MHz, CDCl3): δ 7.85 (2H, dd, J = 1.4 Hz, 7.9 Hz, H2″,6″), 7.56 (2H, d, J = 8.7 Hz, H2′,6′), 7.52 (1H, tt, J = 1.4 Hz, 7.6 Hz, H4″), 7.42 (2H, dd, J = 7.6 Hz, 7.9 Hz, H3″,5″), 7.15–7.10 (3H, m, H3′,5′, H5),
‐ 153 ‐ 6.83 (1H, br s, H4), 6.69 (1H, dd, J = 2.2 Hz, 8.2 Hz, H6), 6.49 (1H, d, J = 2.2 Hz, H8), 6.18 (1H, dd, J = 2.2 Hz, 9.6 Hz, H2), 3.82 (1H, dd, J = 9.6 Hz, 16.5 Hz, CHaCOPh), b 2.76 (1H, dd, J = 2.2 Hz, 16.5 Hz, CH COPh), 2.31 (3H, s, COCH3), 2.25 (3H, s, 13 COCH3). C NMR (75 MHz, CDCl3): δ 197.2 (CO), 169.4 (CO), 169.2 (CO), 151.7 (ArC), 151.4 (ArC), 150.6 (ArC), 136.8 (ArC), 133.6 (ArC), 133.4 (ArC), 133.3 (ArC), 128.6 (ArC), 127.4 (ArC), 126.4 (ArC), 122.2 (ArC), 120.2 (ArC), 119.5 (ArC), 115.1
(ArC), 110.6 (ArC), 72.9 (C2), 41.2 (CH2), 21.1 (COCH3), 21.1 (COCH3). IR (KBr):
νmax 3438 (w), 3061 (w), 2930 (w), 1762 (s), 1673 (s), 1630 (w), 1599 (m), 1582 (w), 1509 (m), 1494 (m), 1449 (m), 1431 (w), 1371 (s), 1348 (w), 1314 (w), 1289 (w), 1270 (m), 1256 (m), 1211 (s), 1170 (s), 1138 (s), 1115 (s), 1043 (m), 1013 (m), 976 (w), 961 -1 -1 -1 (w), 903 (m), 847 (m), 758 (w) cm . UV-vis (MeOH): λmax 328 nm (ε 9,513 cm M ), 293 (7,459), 241 (15,929), 203 (25,473). HRMS (+ESI): Found m/z 465.1297, [M+Na]+;
C27H22O6Na required 465.1309.
2-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2- yl)-1-phenylethanone (182) 3" 2" 4" The isoflavene 183 (50 mg, 0.10 mmol) was dissolved in O 5" 8 6" ethanol (15 mL). Aqueous KOH (1 M, 1.0 mL, 1.0 mmol) HO O 2 was added dropwise. The mixture was stirred at room 3 2' 6 3' temperature for 18 hours before being neutralised with 1 5 4 6' OH M HCl. Water (25 mL) was added. The mixture was 5' extracted with ethyl acetate (3 × 10 mL). The combined extracts were washed with brine (10 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 182 (31 mg, 83%) as a tan solid. M.p. 231–234 °C (decomp.). 1H NMR
(300 MHz, d6-DMSO): δ 9.59 (1H, br s OH), 9.50 (1H, br s OH), 7.85 (2H, dd, J = 1.3 Hz, 8.0 Hz, H2″,6″), 7.63 (1H, tt, J = 1.3 Hz, 7.5 Hz, H4″), 7.48 (2H, dd, J = 7.6 Hz, 7.9 Hz, H3″,5″), 7.39 (2H, d, J = 8.7Hz, H2′,6′), 7.01 (1H, d, J = 8.3 Hz, H5), 6.85 (1H, br s, H4), 6.79 (2H, d, J = 8.7 Hz, H3′,5′), 6.35 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 6.03 (1H, d, J = 2.3 Hz, H8), 5.91 (1H, dd, J = 2.1 Hz, 9.9 Hz, H2), 3.63 (1H, dd, J = 9.6 Hz, 16.4 Hz, CHaCOPh), 2.82 (1H, dd, J = 2.1 Hz, 16.4 Hz, CHbCOPh). 13C NMR (75 MHz,
CDCl3): δ 197.2 (CO), 158.4 (ArC), 157.2 (ArC), 151.2 (ArC), 136.7 (ArC), 133.4 (ArC), 129.9 (ArC), 128.7 (ArC), 128.1 (ArC), 127.6 (ArC), 126.6 (ArC), 126.0 (ArC), 116.9 (ArC), 115.7 (ArC), 114.4 (ArC), 109.0 (ArC), 103.2 (ArC), 72.1 (C2), 40.8
(CH2). IR (KBr): νmax 3432 (s), 1743 (w), 1612 (s), 1513 (s), 1448 (m), 1370 (w), 1263
‐ 154 ‐ (m), 1214 (s), 1172 (s), 1112 (m), 1041 (w), 1014 (w), 836 (w) cm-1. UV-vis (MeOH): -1 -1 + λmax 278 nm (ε 11,194 cm M ). HRMS (+ESI): Found m/z 381.1091, [M+Na] ;
C23H18O4Na required 381.1097.
4-(7-Acetoxy-2-(2-oxo-2-(p-tolyl)ethyl)-2H-chromen- 3" 2" 3-yl)phenyl acetate (184) O 5" 8 6" 4-Methylacetophenone (0.31 mL, 2.3 mmol) was added AcO O 2 to a suspension of isoflavylium salt 55 (1.00 g, 2.14 3 2' 6 3' mmol) in dichloromethane (40 mL). The reaction 5 4 6' OAc mixture was stirred at room temperature for 18 hours. 5' Solvent was evaporated in vacuo and the crude product recrystallised from aqueous ethanol to give the title compound 184 (713 mg, 73%) as a yellow-green powder. M.p. 1 126–130 °C. H NMR (300 MHz, CDCl3): δ 7.75 (2H, d, J = 8.8 Hz, H2″,6″), 7.55 (2H, d, J = 8.8 Hz, H3″,5″), 7.21 (2H, d, J = 8.8, H2′,6′), 7.15–7.09 (3H, m, H3′,5′, H5), 6.82 (1H, br s, H4), 6.69 (1H, dd, J = 2.4 Hz, 8.2 Hz, H6), 6.49 (1H, d, J = 2.4 Hz, H8), 6.17 (1H, dd, J = 2.2 Hz, 9.6 Hz, H2), 3.79 (1H, dd, J = 9.6 Hz, 16.5 Hz, CHaCOAr), 2.73 b (1H, dd, J = 2.1 Hz, 16.5 Hz, CH COAr), 2.39 (3H, s, CH3), 2.31 (3H, s, COCH3), 2.25 13 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 196.9 (CO), 169.5 (CO), 169.3 (CO), 151.7 (ArC), 151.3 (ArC), 150.6 (ArC), 144.3 (ArC), 134.4 (ArC), 133.6 (ArC), 133.4 (ArC), 129.3 (ArC), 128.5 (ArC), 127.4 (ArC), 126.4 (ArC), 122.1 (ArC), 120.2 (ArC),
119.4 (ArC), 115.1 (ArC), 110.6 (ArC), 72.9 (C2), 41.0 (CH2), 21.7 (CH3), 21.2 (CH3),
21.1 (CH3). IR (KBr): νmax 3473 (w), 3048 (w), 2978 (w), 2941 (w), 1755 (s), 1743 (s), 1672 (s), 1640 (w), 1603 (s), 1573 (w), 1510 (s), 1493 (m), 1430 (m), 1371 (s), 1347 (w), 1314 (w), 1288 (m), 1259 (m), 1201 (s), 1169 (s), 1138 (s), 1110 (s), 1042 (m), 1013 (m), 978 (w), 958 (w), 907 (m), 886 (w), 847 (m), 824 (m) cm-1. UV-vis (MeOH): -1 -1 λmax 329 nm (ε 13,272 cm M ), 294 (10,362), 247 (20,713), 208 (25,872). HRMS + (+ESI): Found m/z 457.1636, [M+H] ; C28H25O6 required 457.1646.
‐ 155 ‐ 4-(7-Acetoxy-2-(2-(4-ethylphenyl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (185) 4-Ethylacetophenone (0.35 mL, 2.4 mmol) was added 3" 2" to a suspension of isoflavylium salt 55 (1.03 g, 2.20 O 5" 8 6" mmol) in dichloromethane (40 mL). The reaction AcO O 2 mixture was stirred at room temperature for 18 hours. 3 2' 6 3' Solvent was evaporated in vacuo and the crude 5 4 6' OAc product recrystallised from aqueous ethanol to give 5' the title compound 185 (847 mg, 75%) as a pale green powder. M.p. 118–124 °C. 1H
NMR (300 MHz, CDCl3): δ 7.77 (2H, d, J = 8.8 Hz, H2″,6″), 7.55 (2H, d, J = 8.8 Hz, H3″,5″), 7.23 (2H, d, J = 8.8, H2′,6′), 7.14–7.10 (3H, m, H3′,5′, H5), 6.82 (1H, br s, H4), 6.69 (1H, dd, J = 2.4 Hz, 8.2 Hz, H6), 6.48 (1H, d, J = 2.4 Hz, H8), 6.17 (1H, dd, J = 2.2 Hz, 9.7 Hz, H2), 3.79 (1H, dd, J = 9.4 Hz, 16.4 Hz, CHaCOAr), 2.74 (1H, dd, J = b 2.1 Hz, 16.4 Hz, CH COAr), 2.66 (2H, q, J = 7.4 Hz, CH2CH3), 2.31 (3H, s, COCH3), 13 2.25 (3H, s, COCH3), 1.23 (2H, q, J = 7.4 Hz, CH2CH3). C NMR (75 MHz, CDCl3): δ 196.8 (CO), 169.4 (CO), 169.2 (CO), 151.7 (ArC), 151.3 (ArC), 150.4 (ArC), 144.5, (ArC), 134.7 (ArC), 133.6 (ArC), 133.4 (ArC), 128.6 (ArC), 128.1 (ArC), 127.3 (ArC), 126.4 (ArC), 122.2 (ArC), 120.2 (ArC), 119.4 (ArC), 115.1 (ArC), 110.6 (ArC), 72.9
(C2), 41.1 (CH2), 29.2 (CH2), 21.2 (CH3), 21.1 (CH3), 15.2 (CH3). IR (KBr): νmax 3392 (w), 3048 (w), 2968 (m), 2930 (w), 2871 (w), 1745 (s), 1668 (s), 1604 (s), 1567 (w), 1511 (s), 1494 (m), 1455 (w), 1431 (w), 1370 (m), 1343 (w), 1313 (w), 1287 (m), 1260 (m), 1203 (s), 1169 (s), 1138 (s), 1110 (s), 1039 (m), 1015 (m), 979 (w), 959 (w), 949 -1 (w), 908 (m), 890 (w), 874 (w), 846 (m), 803 (w) cm . UV-vis (MeOH): λmax 328 nm (ε 16,277 cm-1M-1), 248 (24,769), 209 (29,149). HRMS (+ESI): Found m/z 493.1606, + [M+Na] ; C29H26O6Na required 493.1622.
4-(7-Acetoxy-2-(2-(4-methoxyphenyl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (186) 4-Methoxyacetophenone (311 mg, 2.4 mmol) was 3" 2" O added to a suspension of isoflavylium salt 55 (1.02 g, O 5" 8 6" 2.18 mmol) in dichloromethane (40 mL). The AcO O 2 reaction mixture was stirred at room temperature for 3 2' 6 3' 18 hours. Solvent was evaporated in vacuo and the 5 4 6' OAc 5'
‐ 156 ‐ crude product recrystallised from aqueous ethanol to give the title compound 186 (536 1 mg, 52%) as a brownish green powder. M.p. 116–117 °C. H NMR (300 MHz, CDCl3): δ 7.83 (2H, d, J = 8.8 Hz, H2″,6″), 7.56 (2H, d, J = 8.8 Hz, H2′,6′), 7.15–7.10 (3H, m, H3′,5′, H5), 6.89 (2H, d, J = 8.8, H3″,5″), 6.83 (1H, br s, H4), 6.69 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 6.44 (1H, d, J = 2.3 Hz, H8), 6.16 (1H, dd, J = 2.1 Hz, 9.4 Hz, H2), 3.85 (3H, s, OMe), 3.78 (1H, dd, J = 9.4 Hz, 16.4 Hz, CHaCOAr), 2.72 (1H, dd, J = 2.1 Hz, b 13 16.4 Hz, CH COAr), 2.31 (3H, s, COCH3), 2.25 (3H, s, COCH3). C NMR (75 MHz,
CDCl3): δ 195.6 (CO), 169.4 (CO), 169.2 (CO), 163.7 (ArC), 151.7 (ArC), 151.3 (ArC), 150.6 (ArC), 133.6 (ArC), 133.5 (ArC), 130.8 (ArC), 130.1 (ArC), 127.3 (ArC), 126.4 (ArC), 122.2 (ArC), 120.3 (ArC), 119.3 (ArC), 115.0 (ArC), 113.8 (ArC), 110.7 (ArC),
73.1 (C2), 55.5 (OMe), 41.1 (CH2), 21.1 (CH3), 21.1 (CH3). IR (KBr): νmax 3441 (s), 1750 (s), 1666 (s), 1650 (w), 1642 (w), 1631 (m), 1602 (s), 1580 (m), 1510 (m), 1495 (w), 1433 (w), 1371 (m), 1312 (w), 1289 (w), 1258 (s), 1232 (s), 1212 (s), 1170 (m), -1 1142 (m), 1113 (m), 1046 (w), 1027 (w), 934 (w), 845 (w) cm . UV-vis (MeOH): λmax 327 nm (ε 8,009 cm-1M-1), 284 (14,033), 243 (10,844), 208 (15,828). HRMS (+ESI): + Found m/z 495.1398, [M+Na] ; C28H24O7Na required 495.1414.
4-(7-Acetoxy-2-(2-(4-bromophenyl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (187) 4-Bromoacetophenone (480 mg, 2.4 mmol) was added 3" 2" Br to a suspension of isoflavylium salt 55 (1.00 g, 2.14 O 5" 8 6" mmol) in dichloromethane (40 mL). The reaction AcO O 2 mixture was stirred at room temperature for 17 hours. 3 2' 6 3' Solvent was evaporated in vacuo and the crude product 5 4 6' OAc recrystallised from aqueous ethanol to give the title 5' compound 187 (748 mg, 67%) as a pale yellow powder. M.p. 128–133 °C. 1H NMR
(300 MHz, CDCl3): δ 7.70 (2H, d, J = 8.7 Hz, H2″,6″), 7.56 (2H, d, J = 8.7, H3″,5″), 7.54 (2H, d, J = 8.8 Hz, H2′,6′), 7.15–7.10 (3H, m, H3′,5′, H5), 6.82 (1H, br s, H4), 6.70 (1H, dd, J = 2.0 Hz, 8.2 Hz, H6), 6.44 (1H, d, J = 2.0 Hz, H8), 6.13 (1H, dd, J = 2.2 Hz, 9.6 Hz, H2), 3.76 (1H, dd, J = 9.6 Hz, 16.3 Hz, CHaCOAr), 2.72 (1H, dd, J = 2.2 Hz, b 13 16.3 Hz, CH COAr), 2.32 (3H, s, COCH3), 2.27 (3H, s, COCH3). C NMR (75 MHz,
CDCl3): δ 196.3 (CO), 169.4 (CO), 169.2 (CO), 151.5 (ArC), 151.4 (ArC), 150.7 (ArC), 135.6 (ArC), 133.5 (ArC), 133.2 (ArC), 132.0 (ArC), 130.0 (ArC), 128.7 (ArC), 127.4 (ArC), 126.4 (ArC), 122.2 (ArC), 120.1 (ArC), 119.5 (ArC), 115.2 (ArC), 110.6 (ArC),
‐ 157 ‐ 73.0 (C2), 41.1 (CH2), 21.1 (CH3), 21.1 (CH3). IR (KBr): νmax 3433 (w), 3060 (w), 2933 (w), 1755 (s), 1670 (s), 1612 (w), 1585 (m), 1510 (m), 1493 (w), 1432 (w), 1396 (w), 1371 (s), 1289 (w), 1261 (m), 1209 (s), 1170 (s), 1141 (s), 1114 (s), 1071 (w), 1045 -1 (m), 1011 (m), 962 (w), 908 (m), 844 (w) cm . UV-vis (MeOH): λmax 324 nm (ε 13,243 cm-1M-1), 247 (15,406), 204 (27,424). HRMS (+ESI): Found m/z 543.0404, [M+Na]+;
C27H21BrO6Na required 543.0414.
4-(7-Acetoxy-2-(2-(4-chlorophenyl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (188) 4-Chloroacetophenone (0.30 mL, 2.3 mmol) was added 3" 2" Cl to a suspension of isoflavylium salt 55 (1.01 g, 2.16 O 5" 8 6" mmol) in dichloromethane (40 mL). The reaction AcO O 2 mixture was stirred at room temperature for 17 hours. 3 2' 6 3' Solvent was evaporated in vacuo and the crude product 5 4 6' OAc recrystallised from ethyl acetate to give the title 5' compound 188 (649 mg, 63%) as a pale yellow powder. M.p. 172–174 °C. 1H NMR
(300 MHz, CDCl3): δ 7.78 (2H, d, J = 8.8 Hz, H2″,6″), 7.54 (2H, d, J = 8.8 Hz, H2′,6′), 7.40 (2H, d, J = 8.8, H3″,5″), 7.15–7.10 (3H, m, H3′,5′, H5), 6.82 (1H, br s, H4), 6.70 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.44 (1H, d, J = 2.3 Hz, H8), 6.13 (1H, dd, J = 2.3 Hz, 9.6 Hz, H2), 3.78 (1H, dd, J = 9.6 Hz, 16.1 Hz, CHaCOAr), 2.72 (1H, dd, J = 2.3 Hz, b 13 16.1 Hz, CH COAr), 2.32 (3H, s, COCH3), 2.26 (3H, s, COCH3). C NMR (75 MHz,
CDCl3): δ 196.1 (CO), 169.4 (CO), 169.2 (CO), 151.5 (ArC), 151.4 (ArC), 150.7 (ArC), 139.9 (ArC), 135.3 (ArC), 133.5 (ArC), 133.2 (ArC), 129.8 (ArC), 129.0 (ArC), 127.4 (ArC), 126.4 (ArC), 122.2 (ArC), 120.1 (ArC), 119.5 (ArC), 115.2 (ArC), 110.6 (ArC),
73.0 (C2), 41.1 (CH2), 21.1 (CH3), 21.1 (CH3). IR (KBr): νmax 3441 (w), 1755 (s), 1670 (s), 1611 (w), 1585 (m), 1510 (m), 1497 (w), 1432 (w), 1398 (w), 1371 (s), 1337 (w), 1313 (w), 1289 (w), 1261 (m), 1211 (s), 1169 (m), 1142 (s), 1113 (m), 1093 (m), 1045 (m), 1013 (m), 962 (w), 950 (w), 907 (m), 844 (m), 826 (w), 796 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 327 nm (ε 13,449 cm M ), 294 (10,791), 246 (22,462), 208 (25,670). + HRMS (+ESI): Found m/z 499.0908, [M+Na] ; C27H21ClO6Na required 499.0919.
‐ 158 ‐ 2-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-1-(p-tolyl)ethanone (189) The isoflavene 184 (50 mg, 0.11 mmol) was dissolved in 3" 2" ethanol (10 mL). Aqueous KOH (1 M, 0.5 mL, 0.5 mmol) O 5" 8 6" was added dropwise. The mixture was stirred at room HO O 2 temperature for 18 hours before being neutralised with 1 3 2' 6 3' M HCl. Water (25 mL) was added. The mixture was 5 4 6' OH extracted with ethyl acetate (3 × 10 mL). The combined 5' extracts were washed with brine (10 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 189 (34 mg, 83%) as an orange solid. 1 M.p. 114–118 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.60 (1H, br s OH), 9.50 (1H, br s OH), 7.75 (2H, d, J = 8.8 Hz, H2″,6″), 7.39 (2H, d, J = 8.8 Hz, H2′,6′), 7.28 (2H, d, J = 8.8 Hz, H3″,5″), 7.01 (1H, d, J = 8.3 Hz, H5), 6.84 (1H, br s, H4), 6.79 (2H, d, J = 8.8 Hz, H3′,5′), 6.35 (1H, dd, J = 2.4 Hz, 8.3 Hz, H6), 6.03 (1H, d, J = 2.4 Hz, H8), 5.89 (1H, dd, J = 2.1 Hz, 9.8 Hz, H2), 3.61 (1H, dd, J = 9.8 Hz, 16.2 Hz, a b 13 CH COAr), 2.75 (1H, dd, J = 2.1 Hz, 16.2 Hz, CH COAr), 2.36 (3H, s, CH3). C NMR
(75 MHz, d6-DMSO): δ 196.8 (CO), 158.4 (ArC), 156.9 (ArC), 151.3 (ArC), 134.4 (ArC), 129.9 (ArC), 129.3 (ArC), 128.3 (ArC), 127.7 (ArC), 126.7 (ArC), 126.0 (ArC), 116.1 (ArC), 115.7 (ArC), 114.6 (ArC), 114.2 (ArC), 109.1 (ArC), 103.6 (ArC), 72.5
(C2), 31.1 (CH2), 21.3 (CH3). IR (KBr): νmax 3376 (s), 3026 (w), 2956 (w), 2922 (w), 1643 (s), 1619 (s), 1602 (s), 1578 (m), 1514 (s), 1460 (m), 1441 (m), 1406 (w), 1384 (w), 1365 (w), 1335 (m), 1290 (s), 1277 (m), 1253 (s), 1228 (s), 1181 (s), 1173 (s), 1152 (s), 1118 (s), 1036 (w), 1017 (w), 1007 (w), 832 (m), 817 (w), 802 (w) cm-1. UV- -1 -1 vis (MeOH): λmax 277 nm (ε 14,152 cm M ). HRMS (+ESI): Found m/z 395.1245, + [M+Na] ; C24H20O4Na required 395.1254.
1-(4-Ethylphenyl)-2-(7-hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)ethanone (190) The isoflavene 185 (50 mg, 0.11 mmol) was dissolved 3" 2" in ethanol (15 mL). Aqueous KOH (1 M, 0.5 mL, 0.5 O 5" 8 6" mmol) was added dropwise. The mixture was stirred at HO O 2 room temperature for 16 hours before being 3 2' 6 3' neutralised with 1 M HCl. Water (25 mL) was added. 5 4 6' OH The mixture was extracted with ethyl acetate (3 × 15 5' mL). The combined extracts were washed with brine (15 mL) and dried over MgSO4.
‐ 159 ‐ The solvent was evaporated in vacuo to give the title compound 190 (36 mg, 85%) as a 1 dark yellow solid. M.p. 129–131 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.60 (1H, br s OH), 9.50 (1H, br s OH), 7.78 (2H, d, J = 8.8 Hz, H2″,6″), 7.39 (2H, d, J = 8.8 Hz, H2′,6′), 7.32 (2H, d, J = 8.8 Hz, H3″,5″), 7.01 (1H, d, J = 8.3 Hz, H5), 6.84 (1H, br s, H4), 6.79 (2H, d, J = 8.8 Hz, H3′,5′), 6.35 (1H, dd, J = 2.4 Hz, 8.3 Hz, H6), 6.03 (1H, d, J = 2.4 Hz, H8), 5.90 (1H, dd, J = 2.1 Hz, 9.7 Hz, H2), 3.61 (1H, dd, J = 9.7 Hz, 16.3 Hz, CHaCOAr), 2.75 (1H, dd, J = 2.1 Hz, 16.3 Hz, CHbCOAr), 2.66 (2H, q, J = 7.7 Hz, 13 CH2 CH3) 1.18 (3H, t, J = 7.7 Hz, CH2CH3). C NMR (75 MHz, d6-DMSO): δ 196.8 (CO), 158.3 (ArC), 157.1 (ArC), 151.3 (ArC), 150.1 (ArC), 140.4 (ArC), 134.7 (ArC), 129.9 (ArC), 128.3 (ArC), 128.1 (ArC), 127.6 (ArC), 126.0 (ArC), 116.9 (ArC), 115.7
(ArC), 114.5 (ArC), 108.6 (ArC), 100.6 (ArC), 72.4 (C2), 28.2 (CH2), 20.2 (CH2), 15.1
(CH3). IR (KBr): νmax 3415 (s), 2925 (w), 2848 (w), 1693 (w), 1657 (m), 1620 (s), 1556 (w), 1514 (s), 1498 (w), 1462 (m), 1440 (w), 1389 (w), 1371 (w), 1266 (m), 1226 (s), -1 1166 (s), 1154 (s), 1117 (s), 1092 (m), 1024 (w), 834 (w) cm . UV-vis (MeOH): λmax 282 nm (ε 9,056 cm-1M-1), 203 (18,846). HRMS (+ESI): Found m/z 409.1406, [M+Na]+;
C25H22O4Na required 409.1410.
2-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-1-(4- methoxyphenyl)ethanone (191) The isoflavene 186 (50 mg, 0.11 mmol) was dissolved 3" 2" O in ethanol (15 mL). Aqueous KOH (1 M, 0.5 mL, 0.5 O 5" 8 6" mmol) was added dropwise. The mixture was stirred at HO O 2 room temperature for 16 hours before being 3 2' 6 3' neutralised with 1 M HCl. Water (25 mL) was added. 5 4 6' OH The mixture was extracted with ethyl acetate (3 × 15 5' mL). The combined extracts were washed with brine (15 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 191 (9 mg, 85%) as a 1 brown solid. M.p. 196–200 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 8.66 (2H, br s, OH), 7.91 (2H, d, J = 9.0 Hz, H2″,6″), 7.47 (2H, d, J = 8.8 Hz, H2′,6′), 7.04 (1H, d, J = 8.5 Hz, H5), 7.00 (2H, d, J = 9.0, H3″,5″), 6.89 (2H, d, J = 8.8 Hz, H3′,5′), 6.86 (1H, br s, H4), 6.45 (1H, dd, J = 2.3 Hz, 8.1 Hz, H6), 6.16 (1H, d, J = 2.3 Hz, H8), 6.03 (1H, dd, J = 2.1 Hz, 9.6 Hz, H2), 3.89 (3H, s, OCH3), 3.77 (1H, dd, J = 9.6 Hz, 16.3 Hz, a b 13 CH COAr), 2.72 (1H, dd, J = 2.1 Hz, 16.3 Hz, CH COAr). C NMR (75 MHz, d6- DMSO): δ 195.5 (CO), 163.5 (ArC), 158.3 (ArC), 157.1 (ArC), 151.3 (ArC), 130.4
‐ 160 ‐ (ArC), 130.0 (ArC), 129.6 (ArC), 127.9 (ArC), 126.6 (ArC), 125.9 (ArC), 119.1 (ArC), 116.8 (ArC), 115.7 (ArC), 114.4 (ArC), 113.8 (ArC), 103.6 (ArC), 72.4 (C2), 55.8
(OCH3), 37.8 (CH2). IR (KBr): νmax 3374 (s), 3016 (w), 2933 (w), 2830 (w), 1642 (s), 1621 (s), 1589 (s), 1514 (s), 1457 (w), 1442 (m), 1368 (w), 1335 (m), 1290 (m), 1265 (s), 1231 (s), 1171 (s), 1152 (s), 1117 (s), 1037 (w), 1023 (m), 983 (w), 962 (w), 867 -1 -1 -1 (w), 834 (m), 800 (w) cm . UV-vis (MeOH): λmax 327 nm (ε 15,595 cm M ), 283 + (16,935), 203 (26,800). HRMS (+ESI): Found m/z 411.1196, [M+Na] ; C24H20O5Na required 411.1203.
1-(4-Bromophenyl)-2-(7-hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)ethanone (192) The isoflavene 187 (50 mg, 0.11 mmol) was dissolved 3" 2" Br in ethanol (5 mL). Aqueous KOH (1 M, 0.2 mL, 0.2 O 5" 8 6" mmol) was added dropwise. The mixture was stirred at HO O 2 room temperature for 16 hours before being neutralised 3 2' 6 3' with 1 M HCl. Water (15 mL) was added. Filtration 5 4 6' OH afforded the title compound 192 (45 mg, 94%) as a 5' 1 beige powder. M.p. 132–136 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 8.60 (1H, br s, OH), 8.51 (1H, br s, OH), 7.86 (2H, d, J = 8.8 Hz, H2″,6″), 7.68 (2H, d, J = 8.8, H3″,5″), 7.45 (2H, d, J = 8.8 Hz, H2′,6′), 7.03 (1H, d, J = 8.4 Hz, H5), 6.88 (2H, d, J = 8.8 Hz, H3′,5′), 6.85 (1H, br s, H4), 6.44 (1H, dd, J = 2.4 Hz, 8.1 Hz, H6), 6.44 (1H, d, J = 2.4 Hz, H8), 6.13 (1H, dd, J = 2.4 Hz, 9.8 Hz, H2), 3.76 (1H, dd, J = 9.8 Hz, 16.3 a b 13 Hz, CH COAr), 2.84 (1H, dd, J = 2.4 Hz, 16.3 Hz, CH COAr). C NMR (75 MHz, d6- DMSO): δ 196.5 (CO), 158.3 (ArC), 157.1 (ArC), 151.2 (ArC), 135.6 (ArC), 131.7 (ArC), 130.1 (ArC), 129.8 (ArC), 127.6 (ArC), 127.5 (ArC), 126.6 (ArC), 126.0 (ArC), 116.9 (ArC), 115.7 (ArC), 114.4 (ArC), 109.0 (ArC), 103.3 (ArC), 72.1 (C2), 40.9
(CH2). IR (KBr): νmax 3406 (s), 1754 (w), 1745 (w), 1731 (w), 1668 (s), 1643 (w), 1613 (s), 1584 (s), 1568 (w), 1556 (w), 1515 (s), 1485 (w), 1461 (w), 1454 (w), 1433 (w), 1396 (m), 1370 (m), 1332 (w), 1289 (s), 1267 (m), 1243 (s), 1223 (s), 1178 (s), 1158 (m), 1114 (m), 1071 (m), 1032 (w), 1006 (w), 984 (w), 958 (w), 833 (s) cm-1. UV-vis -1 -1 (MeOH): λmax 330 nm (ε 13,720 cm M ), 252 (17,027), 205 (25,390). HRMS (+ESI): + Found m/z 459.0195, [M+Na] ; C23H17BrO4Na required 459.0202.
‐ 161 ‐ 1-(4-Chlorophenyl)-2-(7-hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)ethanone (193) The isoflavene 188 (30 mg, 0.063 mmol) was dissolved 3" 2" Cl in ethanol (5 mL). Aqueous KOH (1 M, 0.3 mL, 0.3 O 5" 8 6" mmol) was added dropwise. The mixture was stirred at HO O 2 room temperature for 18 hours before being neutralised 3 2' 6 3' with 1 M HCl. Water (15 mL) was added. Filtration 5 4 6' OH afforded the title compound 193 (22 mg, 89%) as a red 5' 1 powder. M.p. 224–227 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.62 (1H, br s, OH), 9.53 (1H, br s, OH), 7.88 (2H, d, J = 8.8 Hz, H2″,6″), 7.57 (2H, d, J = 8.8 Hz, H2′,6′), 7.40 (2H, d, J = 8.8, H3″,5″), 7.03 (1H, d, J = 8.2 Hz), 6.86 (1H, br s, H4), 6.81 (2H, d, J = 8.8 Hz, H3′,5′), 6.37 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.04 (1H, d, J = 2.3 Hz, H8), 5.91 (1H, dd, J = 2.0 Hz, 9.7 Hz, H2), 3.62 (1H, dd, J = 9.7 Hz, 16.3 Hz, a b 13 CH COAr), 2.86 (1H, dd, J = 2.0 Hz, 16.3 Hz, CH COAr). C NMR (75 MHz, d6- DMSO): δ 196.3 (CO), 158.4 (ArC), 157.1 (ArC), 151.1 (ArC), 138.3 (ArC), 135.3 (ArC), 130.0 (ArC), 129.8 (ArC), 128.8 (ArC), 127.6 (ArC), 126.6 (ArC), 126.0 (ArC), 116.9 (ArC), 115.7 (ArC), 114.4 (ArC), 109.0 (ArC), 103.3 (ArC), 72.1 (C2), 40.9
(CH2). IR (KBr): νmax 3434 (s), 1651 (m), 1615 (s), 1589 (m), 1557 (w), 1539 (w), 1514 (m), 1456 (m), 1398 (w), 1372 (w), 1268 (m), 1216 (s), 1173 (s), 1114 (m), 1092 (s), -1 -1 -1 1012 (m), 833 (m) cm . UV-vis (MeOH): λmax 278 nm (ε 10,174 cm M ). HRMS + (+ESI): Found m/z 415.0704, [M+Na] ; C23H17ClO4Na required 415.0708.
4-(7-Acetoxy-2-(2-(naphthalen-1-yl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (194) 1-Acetylnapthalene (0.65 mL, 4.3 mmol) was added to 4" 3" 5" a suspension of isoflavylium salt 55 (1.48 g, 3.16 mmol) 2" 6" in dichloromethane (75 mL). The reaction mixture was O 7" 8 8" stirred at room temperature for 18 hours. Water (100 AcO O 2 mL) was added. The resulting mixture was extracted 3 2' 6 3' with dichloromethane (2 × 50 mL). The combined 5 4 6' OAc extracts were dried over MgSO4 Solvent was 5' evaporated in vacuo to give the title compound 194 (772 mg, 49%) as a dark yellow 1 amorphous solid. M.p. 46–50 °C (decomp.). H NMR (300 MHz, CDCl3): δ 8.61 (1H, dd, J =1.2 Hz, 8.2 Hz, H8″), 8.03–7.93 (1H, m, H4″), 7.90–9.84 (1H, m, H5″), 7.71 (1H,
‐ 162 ‐ dd, J = 1.2 Hz, 7.2 Hz, H2″), 7.64–7.50 (4H, m, H6″, H7″, H2′,6′), 7.45 (1H, dd, J = 7.2 Hz, 8.2 Hz, H3″), 7.14 (2H, d, J = 8.9 Hz, H3′,5′), 7.11 (1H, d, J = 8.3 Hz, H5), 6.81 (1H, br s, H4), 6.69 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.50 (1H, d, J = 2.3 Hz, H8), 6.23 (1H, dd, J = 2.3 Hz, 9.8 Hz, H2), 3.85 (1H, dd, J = 9.8 Hz, 16.1 Hz, CHaCOAr), 2.91 b (1H, dd, J = 2.3 Hz, 16.1 Hz, CH COAr), 2.32 (3H, s, COCH3), 2.27 (3H, s, COCH3). 13 C NMR (75 MHz, CDCl3): δ 201.0 (CO), 169.4 (CO), 169.1 (CO), 151.7 (ArC), 151.3 (ArC), 150.6 (ArC), 135.7 (ArC), 133.9 (ArC), 133.6 (ArC), 133.3 (ArC), 133.0 (ArC), 128.4 (ArC), 128.3 (ArC), 128.1 (ArC), 127.4 (ArC), 126.5 (ArC), 126.0 (ArC), 125.8 (ArC), 124.4 (ArC), 122.2 (ArC), 121.9 (ArC), 120.2 (ArC), 119.5 (ArC), 115.1 (ArC),
110.5 (ArC), 73.4 (C2), 44.9 (CH2), 21.1 (CH3), 21.1 (CH3). IR (KBr): νmax 3433 (m), 3047 (w), 2930 (w), 1756 (s), 1677 (m), 1611 (m), 1508 (s), 1496 (m), 1461 (w), 1432 (w), 1369 (m), 1311 (w), 1280 (w), 1201 (s), 1169 (s), 1141 (s), 1115 (m), 1044 (w), -1 1014 (m), 947 (w), 907 (m), 846 (w), 804 (m), 778 (m) cm . UV-vis (MeOH): λmax 322 nm (ε 14,222 cm-1M-1), 214 (35,326). HRMS (+ESI): Found m/z 515.1452, [M+Na]+;
C31H24O6Na required 515.1465.
2-(7-Hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)-1-(naphthalen-1-yl)ethanone (195) The isoflavene 194 (200 mg, 0.41 mmol) was dissolved 4" 3" 5" in ethanol (15 mL). Aqueous KOH (1 M, 1.0 mL, 1.0 2" 6" mmol) was added dropwise. The mixture was stirred at O 7" 8 8" room temperature for 18 hours before being neutralised HO O 2 with 1 M HCl. Water (25 mL) was added. The mixture 3 2' 6 3' was extracted with ethyl acetate (3 × 15 mL). The 5 4 6' OH combined extracts were washed with brine (15 mL) and 5' dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 195 1 (141 mg, 84%) as a tan solid. M.p. 95–98 °C (decomp.). H NMR (300 MHz, d6- DMSO): δ 9.64 (1H, br s, OH), 9.55 (1H, br s, OH), 8.44 (1H, dd, J =1.5 Hz, 8.2 Hz, H8″), 8.19–8.11 (1H, m, H4″), 8.06–7.99 (1H, m, H5″), 7.88 (1H, dd, J = 1.1 Hz, 7.2 Hz, H2″), 7.71–7.58 (2H, m, H6″, H7″), 7.54 (1H, dd, J = 7.2 Hz, 8.3 Hz, H3″), 7.42 (2H, d, J = 8.9 Hz, H2′,6′), 7.01 (1H, d, J = 8.3 Hz, H5), 6.86–6.81 (3H, m, H4, H3′,5′), 6.36 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.07 (1H, d, J = 2.3 Hz, H8), 5.90 (1H, dd, J = 2.4 Hz, 10.1 Hz, H2), 3.53 (1H, dd, J = 10.1 Hz, 15.8 Hz, CHaCOAr), 3.12 (1H, dd, J = b 13 2.4 Hz, 15.8 Hz, CH COAr). C NMR (75 MHz, d6-DMSO): δ 201.5 (CO), 158.4
‐ 163 ‐ (ArC), 157.2 (ArC), 151.1 (ArC), 135.7 (ArC), 133.4 (ArC), 132.4 (ArC), 129.8 (ArC), 129.3 (ArC), 128.5 (ArC), 127.7 (ArC), 127.6 (ArC), 126.6 (ArC), 126.5 (ArC), 126.4 (ArC), 126.0 (ArC), 125.3 (ArC), 124.8 (ArC), 116.9 (ArC), 115.7 (ArC), 114.3 (ArC),
109.0 (ArC), 103.2 (ArC), 72.8 (C2), 44.8 (CH2). IR (KBr): νmax 3404 (s), 2924 (w), 1691 (w), 1664 (m), 1649 (w), 1612 (s), 1553 (w), 1513 (s), 1460 (m), 1452 (m), 1357 (m), 1268 (s), 1232 (s), 1169 (s), 1117 (s), 1046 (w), 987 (w), 957 (w), 833 (m), 803 -1 -1 -1 (m), 776 (m) cm . UV-vis (MeOH): λmax 318 nm (ε 15,256 cm M ), 212 (47,013). + HRMS (+ESI): Found m/z 431.1245, [M+Na] ; C27H20O4Na required 431.1254.
4-(7-Acetoxy-2-(2-(furan-2-yl)-2-oxoethyl)-2H-chromen-3-yl)phenyl acetate (196)
3" 2-Acetylfuran (23 mg, 0.21 mmol) was added to a O suspension of isoflavylium salt 55 (100 mg, 0.21 mmol) O 4" 8 5" in dichloromethane (5 mL). The reaction mixture was AcO O 2
3 2' stirred at room temperature for 19 hours. Water (10 mL) 6 3' 5 4 was added. The resulting mixture was extracted with 6' OAc dichloromethane (2 × 5 mL). The combined extracts 5' were dried over MgSO4 Solvent was evaporated in vacuo and the crude product rexrystallised from ethyl acetate to give the title compound 196 (27 mg, 30%) as an off- 1 white powder. M.p. 158–161 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 7.96 (1H, dd, J = 0.7 Hz, 1.7 Hz, H3″), 7.68 (2H, d, J = 8.8 Hz, H2′,6′), 7.31 (1H, dd, J = 0.7 Hz, 3.7 Hz, H5″), 7.29 (2H, d, J = 8.4 Hz, H5), 7.21 (2H, d, J = 8.8 Hz, H3′,5′), 7.15 (1H, br s, H4), 6.74 (1H, dd, J = 2.2 Hz, 8.2 Hz, H6), 6.66 (1H, dd, J = 1.7 Hz, 3.7 Hz, H4″), 6.47 (1H, d, J = 2.2 Hz, H8), 6.04 (1H, dd, J = 2.4 Hz, 10.1 Hz, H2), 3.48 (1H, dd, J = 10.1 Hz, 15.4 Hz, CHaCOAr), 2.75 (1H, dd, J = 2.4 Hz, 15.4 Hz, CHbCOAr), 2.29 13 (3H, s, COCH3), 2.23 (3H, s, COCH3). C NMR (75 MHz, d6-DMSO): δ 184.6 (CO), 169.1 (CO), 168.9 (CO), 151.8 (ArC), 151.1 (ArC), 150.9 (ArC), 148.2 (ArC), 143.8 (ArC), 132.4 (ArC), 129.0 (ArC), 128.3 (ArC), 127.6 (ArC), 126.3 (ArC), 122.3 (ArC), 119.9 (ArC), 119.2 (ArC), 115.2 (ArC), 112.7 (ArC), 110.1 (ArC), 72.2 (C2), 41.2
(CH2), 20.8 (CH3). IR (KBr): νmax 3432 (w), 3133 (w), 3063 (w), 2929 (w), 1759 (s), 1664 (s), 1607 (w), 1586 (w), 1567 (w), 1509 (m), 1494 (m), 1466 (m), 1445 (w), 1431 (w), 1417 (w), 1372 (m), 1345 (w), 1313 (w), 1294 (w), 1255 (w), 1211 (s), 1168 (s), 1136 (m), 1115 (s), 1038 (m), 1014 (m), 982 (w), 961 (w), 926 (w), 906 (w), 848 (w), -1 -1 -1 773 (w), 762 (w) cm . UV-vis (MeOH): λmax 333 nm (ε 6,962 cm M ), 278 (9,946),
‐ 164 ‐ + 242 (8,562), 207 (12,173). HRMS (+ESI): Found m/z 455.1090, [M+Na] ; C25H20O7Na required 455.1101.
1-(Furan-2-yl)-2-(7-hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-yl)ethanone (197)
3" The isoflavene 196 (40 mg, 0.093 mmol) was dissolved O in ethanol (15 mL). Aqueous KOH (1 M, 1.0 mL, 1.0 O 4" 8 5" mmol) was added dropwise. The mixture was stirred at HO O 2
3 2' room temperature for 18 hours before being neutralised 6 3' 5 4 with 1 M HCl. Water (25 mL) was added. The mixture 6' OH was extracted with ethyl acetate (3 × 15 mL). The 5' combined extracts were washed with brine (15 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the title compound 197 (21 mg, 64%) as a brown solid. 1 M.p. 148–152 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.62 (1H, br s, OH), 9.54 (1H, br s, OH), 7.98 (1H, dd, J = 0.7 Hz, 1.7 Hz, H3″), 7.48 (2H, d, J = 8.8 Hz, H2′,6′), 7.30 (1H, dd, J = 0.7 Hz, 3.7 Hz, H5″), 7.14 (2H, d, J = 8.8 Hz, H3′,5′), 7.01 (1H, d, J = 8.2 Hz, H5), 6.81 (1H, br s, H4), 6.68 (1H, dd, J = 1.7 Hz, 3.7 Hz, H4″), 6.28 (1H, d, J = 2.2 Hz, H8), 6.40 (1H, dd, J = 2.2 Hz, 8.2 Hz, H6), 5.85 (1H, dd, J = 2.4 Hz, 10.1 Hz, H2), 3.63 (1H, dd, J = 10.1 Hz, 15.4 Hz, CHaCOAr), 2.65 (1H, dd, J = b 13 2.4 Hz, 15.4 Hz, CH COAr). C NMR (75 MHz, d6-DMSO): δ 181.9 (CO), 163.8 (ArC), 158.5 (ArC), 154.0 (ArC), 147.2 (ArC), 140.7 (ArC), 132.3 (ArC), 129.1 (ArC), 128.5 (ArC), 124.6 (ArC), 123.4 (ArC), 120.0 (ArC), 119.5 (ArC), 114.5 (ArC), 112.1
(ArC), 111.9 (ArC), 101.8 (ArC), 71.5 (C2), 37.7 (CH2). IR (KBr): νmax 3435 (s), 2919 (w), 2851 (w), 1658 (m), 1650 (s), 1614 (s), 1566 (w), 1556 (w), 1514 (m), 1494 (w), 1462 (m), 1393 (w), 1369 (w), 1263 (m), 1228 (s), 1210 (s), 1170 (s), 1116 (m), 1080 -1 (w), 977 (w), 883 (w), 834 (m), 759 (w), 700 (w) cm . UV-vis (MeOH): λmax 274 nm (ε 5,574 cm-1M-1), 203 (22,294). HRMS (+ESI): Found m/z 371.0890, [M+Na]+;
C21H16O5Na required 371.0895.
‐ 165 ‐ 4-(7-Acetoxy-2-(2-(2-(2,4-dinitrophenyl)hydrazono)propyl)-2H-chromen-3- yl)phenyl acetate (198) A solution of the isoflavene 177 (299 mg, 0.768 3" O2N NO2 mmol) in ethanol (200 mL) was added dropwise N N 5" 8 H 6" to a solution of 2,4-dinitrophenylhydrazine (178 AcO O 2 mg, 0.898 mmol) in ethanol (100 mL). The 3 2' 6 3' mixture was heated at reflux for 19 hours. 5 4 6' OAc Solvent was evaporated in vacuo and the crude 5' product recrystallised from ethyl acetate to afford the title compound 198 (288 mg, 67%) 1 as orange-red needles. M.p. 192–194 °C. H NMR (300 MHz, CDCl3): δ 11.02 (1H, br s, NH), 9.14 (1H, d, J =2.6 Hz, H3″), 8.33 (1H, dd, J =2.6 Hz, 9.6 Hz, H5″), 7.89 (1H, d, J =9.6 Hz, H6″), 7.51 (2H, d, J = 8.7, H2′,6′), 7.15–7.11 (3H, m, H3′,5′, H5), 6.80 (1H, br s, H4), 6.72 (1H, dd, J = 2.2 Hz, 8.1 Hz, H6), 6.49 (1H, d, J = 2.2 Hz, H8), 5.69 (1H, dd, J = 3.1 Hz, 9.7 Hz, H2), 2.95 (1H, dd, J = 9.7 Hz, 14.5 Hz, CHaCN), 2.36 (1H, b dd, J = 3.1 Hz, 14.5 Hz, CH CN), 2.33 (3H, s, COCH3), 2.28 (3H, s, COCH3), 2.11 (3H, 13 s, CNCH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.3 (CO), 153.7 (ArC or CN), 151.5 (ArC or CN), 150.6 (ArC or CN), 145.1 (ArC), 138.0 (ArC), 134.0 (ArC), 133.5 (ArC), 130.1 (ArC), 129.8 (ArC), 129.3 (ArC), 127.5 (ArC), 126.5 (ArC), 123.4 (ArC), 122.4 (ArC), 120.3 (ArC), 119.4 (ArC), 116.7 (ArC), 115.2 (ArC), 110.5 (ArC), 74.7
(C2), 42.1 (CH2), 21.2 (CH3), 21.1 (CH3), 16.6 (CH3). IR (KBr): νmax 3431 (w), 3316 (m), 3110 (w), 2923 (w), 1769 (s), 1754 (s), 1618 (s), 1594 (s), 1508 (s), 1423 (m), 1369 (m), 1336 (s), 1314 (s), 1291 (m), 1259 (w), 1195 (s), 1170 (s), 1137 (s), 1116 (s), 1097 (w), 1045 (m), 1013 (w), 958 (w), 943 (w), 922 (w), 910 (m), 877 (w), 839 (m), -1 -1 -1 743 (w) cm . UV-vis (MeOH): λmax 338 nm (ε 15,904 cm M ), 276 (8,674), 239 + (15,862), 208 (17,600). HRMS (+ESI): Found m/z 583.1431, [M+Na] ; C28H24N4O9Na required 583.1435.
‐ 166 ‐ 2-(2-(2-(2,4-Dinitrophenyl)hydrazono)propyl)-3-(4-hydroxyphenyl)-2H-chromen- 7-ol (199) The isoflavene hydrazone 198 (50 mg, 0.089 3" O2N NO2 mmol) was dissolved in ethanol (15 mL). N N 5" 8 H 6" Aqueous KOH (1 M, 1.0 mL, 1.0 mmol) was HO O 2 added dropwise. The mixture was stirred at room 3 2' 6 3' temperature for 18 hours before being 5 4 6' OH neutralised with 1 M HCl. Water (25 mL) was 5' added. Filtration afforded the title compound 199 (39 mg, 91%) as a dark red solid. M.p. 228–230 °C. 1H NMR (300 MHz, d6-DMSO): δ 10.80 (1H, br s, NH), 8.89 (1H, d, J = 2.5 Hz, H3″), 8.35 (1H, dd, J =2.5 Hz, 9.6 Hz, H5″), 7.78 (1H, d, J = 9.6 Hz, H6″), 7.45 (2H, d, J = 8.7, H2′,6′), 7.14 (2H, d, J = 8.8 Hz, H3′,5′), 7.01 (1H, d, J = 8.2 Hz, H5), 6.86 (1H, br s, H4), 6.39 (1H, dd, J = 2.2 Hz, 8.1 Hz, H6), 6.23 (1H, d, J = 2.2 Hz, H8), 5.73 (1H, dd, J = 3.1 Hz, 9.6 Hz, H2), 2.77 (1H, dd, J = 9.6 Hz, 14.5 Hz, CHaCN), 2.59 b 13 (1H, dd, J = 3.1 Hz, 14.5 Hz, CH CN), 2.12 (3H, s, CNCH3). C NMR (75 MHz, d6- DMSO): δ 158.7 (ArC or CN), 156.5 (ArC or CN), 151.2 (ArC or CN), 145.1 (ArC), 138.0 (ArC), 134.0 (ArC), 133.5 (ArC), 130.1 (ArC), 129.8 (ArC), 129.3 (ArC), 127.6 (ArC), 126.4 (ArC), 123.0 (ArC), 122.4 (ArC), 119.8 (ArC), 115.7 (ArC), 114.3 (ArC),
109.0 (ArC), 103.2 (ArC), 75.0 (C2), 41.9 (CH2), 16.8 (CH3). IR (KBr): νmax 3428 (s), 2927 (w), 1748 (w), 1618 (s), 1592 (s), 1536 (w), 1515 (s), 1462 (w), 1422 (m), 1365 (w), 1334 (s), 1312 (m), 1284 (m), 1211 (m), 1173 (w), 1116 (m), 1096 (w), 1061 (w), -1 1040 (w), 1014 (w), 920 (w), 833 (m), 741 (w) cm . UV-vis (MeOH): λmax 341 nm (ε 10,839 cm-1M-1), 211 (16,684). HRMS (+ESI): Found m/z 499.1222, [M+Na]+;
C24H20N4O7Na required 499.1224.
2-(2-Hydroxy-2-phenylethyl)-3-(4-hydroxyphenyl)- 2H-chromen-7-ol (200) 3" 2" 4" To a solution of the isoflavene 183 (52 mg, 0.12 mmol) HO 5" 8 6" in ethanol (10 mL) sodium borohydride (33 mg, 0.87 HO O 2 mmol) was added. The mixture was heated at reflux 3 2' 6 3' under an atmosphere of nitrogen, for 16 hours. The 5 4 6' OH reaction was quenched with water (30 mL) and 5' neutralised with 1 M HCl. Filtration afforded the title compound 200 (33 mg, 77%) as a 1 brown powder. M.p. 120–124 °C. H NMR (300 MHz, d6-DMSO): δ 9.39 (2H, br s
‐ 167 ‐ OH), 7.52–6.99 (8H, m, ArH, H2′,6′, H5), 6.89 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6 minor product), 6.80 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6 major product), 6.79 (2H, d, J = 8.7Hz, H3′,5′), 6.39 (2H, m, H4, H8), 5.18 (1H, m, H2 minor product), 5.12 (1H, dd, J = 2.0 Hz,
5.0 Hz, H2 major product), 4.85 (1H, dd, J = 5.7 Hz, 10.1 Hz, CH2CHOH), 4.48 (1H, br s, CH2CHOH major product), 4.19 (1H, br d, J = 10.0 Hz, CH2CHOH major product), 3.44 (1H, m, CHaCHOH major product), 3.12 (1H, m, CHaCHOH minor product), 1.99 (1H, m, CHbCHOH major product), 1.90 (1H, m, CHbCHOH minor product). 13C NMR
(75 MHz, d6-DMSO): δ 156.1 (ArC), 153.7 (ArC), 149.9 (ArC), 142.4 (ArC), 136.5 (ArC), 133.5 (ArC), 132.3 (ArC), 128.3 (ArC), 127.2 (ArC), 126.4 (ArC), 121.1 (ArC), 118.4 (ArC), 116.9 (ArC), 113.1 (ArC), 110.7 (ArC), 109.0 (ArC) 79.2 (C2), 50.4
(COH), 38.0 (CH2). IR (KBr): νmax 3446 (s), 2975 (w), 2925 (w), 2848 (w), 1868 (w), 1844 (w), 1830 (w), 1792 (w), 1772 (w), 1749 (m), 1734 (m), 1717 (w), 1699 (w), 1684 (m), 1653 (s), 1647 (m), 1635 (m), 1570 (w), 1558 (s), 1540 (s), 1507 (s), 1497 (w), 1489 (w), 1473 (w), 1457 (m), 1437 (w), 1374 (w), 1219 (m), 1172 (s), 1151 (m), 1116 -1 (m), 1068 (w), 1034 (w), 836 (w), 765 (w), 697 (m) cm . UV-vis (MeOH): λmax 280 nm (ε 2,469 cm-1M-1), 203 (13,749). HRMS (+ESI): Found m/z 383.1254, [M+Na]+;
C23H20O4Na required 383.1254.
4-(7-Acetoxy-2-methylchroman-3-yl)phenyl acetate (201)
8 The isoflavene 131 (160 mg, 0.47 mmol) and Pd/Al2O3 AcO O 2
(5 %, 480 mg) were suspended in absolute ethanol (10 3 2' 6 3' mL). The mixture was stirred under hydrogen (1 atm) 5 4 6' OAc for 90 minutes and then filtered through a plug of 5' Celite. The solvent was evaporated in vacuo to give the title compound 201 (136 mg, 1 84%) as an off-white solid. M.p. 46–50 °C. H NMR (300 MHz CDCl3): δ 7.18 (2H, d, J = 8.4 Hz, H2′,6′), 7.08 (lH, d, J = 8.1 Hz, H5), 7.00 (2H, d, J = 8.4 Hz, H3′,5′), 6.64 (lH, dd, J = 2.2 Hz, 8.1 Hz, H6), 6.60 (1H, d, J = 2.2 Hz, H8), 4.52–4.45 (lH, m, H2),
3.29–3.24 (1H, m, H3), 3.17–2.99 (2H, m, H4), 2.30 (3H, s, COCH3), 2.28 (3H, 13 COCH3), 1.13 (3H, d, J = 6.6 Hz, CH3). C NMR (75 MHz, CDCl3): δ 169.5 (CO), 169.3 (CO), 154.7 (ArC), 149.8 (ArC), 149.5 (ArC), 138.0 (ArC), 130.1 (ArC), 129.5 (ArC), 126.3 (ArC), 121.5 (ArC), 113.9 (ArC), 110.2 (ArC), 74.3 (C2), 41.2 (C3), 28.9
(C4), 21.1 (CH3), 16.4 (CH3). IR (KBr): νmax 3439 (m), 3061 (w), 3023 (w), 2979 (w), 2931 (w), 1760 (s), 1615 (m), 1591 (m), 1507 (s), 1497 (s), 1429 (m), 1369 (s), 1333 (w), 1305 (w), 1253 (m), 1211 (s), 1169 (m), 1139 (s), 1115 (s), 1064 (w), 1043 (w),
‐ 168 ‐ 1015 (m), 948 (w), 912 (w), 891 (w), 849 (w), 804 (w), 757 (w), 734 (w), 700 (m) cm-1. -1 -1 UV-vis (MeOH): λmax 277 nm (ε 2,359 cm M ), 218 (10,054). HRMS (+ESI): Found + m/z 363.1200, [M+Na] ; C20H20O5Na required 363.1208.
4-(7-Acetoxy-2-ethylchroman-3-yl)phenyl acetate (202)
8 The isoflavene 137 (120 mg, 0.34 mmol) and Pd/Al2O3 AcO O 2
(5 %, 450 mg) were suspended in absolute ethanol (10 3 2' 6 3' mL). The mixture was stirred under hydrogen (1 atm) 5 4 6' OAc for 90 minutes and then filtered through a plug of 5' Celite. The solvent was evaporated in vacuo to give the title compound 202 (103 mg, 1 85%) as an off-white solid. M.p. 56–61 °C. H NMR (300 MHz CDCl3): δ 7.17 (2H, d, J = 8.4 Hz, H2′,6′), 7.07 (1H, d, J = 9.1 Hz, H5), 6.98 (2H, d, J = 8.4 Hz, H3′,5′), 6.65– 6.62 (2H, m, H6, H8), 4.18–4.12 (1H, m, H2), 3.33–3.27 (1H, m, H3), 3.25–2.89 (2H, a m, H4), 2.29 (3H, s, COCH3), 2.28 (3H, s, COCH3), 1.54–1.45 (1H, m, CH CH3), b 13 1.40–1.32 (1H, m, CH CH3), 0.96 (3H, dd (app. t), J = 7.3 Hz, CH2CH3). C NMR (75
MHz, CDCl3): δ 169.6 (CO), 169.3 (CO), 155.0 (ArC), 149.8 (ArC), 149.5 (ArC), 138.3 (ArC), 130.2 (ArC), 129.3 (ArC), 121.4 (ArC), 119.1 (ArC), 113.9 (ArC), 110.2 (ArC),
79.9 (C2), 40.3 (C3), 29.4 (C4), 23.8 (CH2), 21.1 (CH3), 10.4 (CH3). IR (KBr): νmax 3439 (m), 3060 (w), 2977 (m), 2935 (m), 2883 (w), 1763 (s), 1613 (m), 1591 (m), 1507 (m), 1497 (m), 1458 (w), 1429 (m), 1367 (m), 1255 (m), 1205 (s), 1170 (m), 1143 (s), 1111 (s), 1060 (w), 1038 (w), 1010 (m), 998 (m), 983 (w), 958 (w), 944 (w), 912 (m), -1 -1 -1 855 (m), 806 (w), 732 (w) cm . UV-vis (MeOH): λmax 278 nm (ε 5,007 cm M ), 219 + (15,315). HRMS (+ESI): Found m/z 377.1352, [M+Na] ; C21H22O5Na required 377.1365.
4-(7-Acetoxy-2-(2-oxopyrrolidin-1-yl)chroman-3-yl)phenyl acetate (203)
The isoflavene 159 (143 mg, 0.35 mmol) was dissolved O 3"
8 in ethyl acetate (20 mL) and added to Pd/C paste (5 %, AcO O 2 N 4" 5" 0.71 g). The mixture was stirred under hydrogen (1 atm) 3 2' 6 3' for 4 hours and then filtered through a plug of Celite. 5 4 6' OAc The solvent was evaporated in vacuo to give the title 5' compound 203 (114 mg, 59%) as a pale grey solid. M.p. 107–111 °C. 1H NMR (300
MHz CDCl3): δ 7.17–7.09 (3H, m, H5, H2′,6′), 6.97 (2H, d, J = 8.7 Hz, H3′,5′), 6.71 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.67 (1H, d, J = 2.3 Hz, H8), 6.10 (1H, d, J = 3.1 Hz,
‐ 169 ‐ H2), 3.53–3.35 (3H, m, H3, H4a, H5″a), 3.31–3.22 (1H, m, H5″b), 2.96 (1H, dd, J = 2.6 Hz, 16.1 Hz, H4b), 2.53–2.44 (1H, m, H3″a), 2.37–2.28 (1H, m, H3″b), 2.30 (3H, s, 13 COCH3), 2.27 (3H, s, COCH3), 1.90–1.67 (2H, m, H4″). C NMR (75 MHz, CDCl3) δ 176.0 (CO), 169.6 (CO), 154.6 (ArC), 150.2 (ArC), 150.1 (ArC), 137.4 (ArC), 130.2 (ArC), 129.7 (ArC), 121.9 (ArC), 118.4 (ArC), 115.3 (ArC), 110.3 (ArC), 80.9 (C2),
44.3 (C3), 40.6 (C5″), 31.3 (C3″), 30.4 (C4), 21.4 (COCH3), 18.9 (C4″). IR (KBr): νmax 3207 (w), 3031 (w), 2963 (m), 2927 (m), 1762 (s), 1689 (s), 1661 (s), 1617 (m), 1593 (m), 1510 (m), 1461 (w), 1418 (m), 1370 (m), 1319 (w), 1289 (m), 1261 (s), 1208 (s), 1143 (m), 1108 (s), 1018 (s), 911 (w), 900 (w), 887 (w), 801 (s) cm-1. UV-vis (MeOH): -1 -1 λmax 281 nm (ε 2,862 cm M ), 223 (6,183). HRMS (+ESI): Found m/z 410.1590, + [M+H] ; C23H24NO6 required 410.1598.
3-(4-Hydroxyphenyl)-2-methylchroman-7-ol (204)
8 The isoflavan 201 (66 mg, 0.19 mmol) was dissolved in HO O 2 methanol (3 mL). Aqueous KOH (1 M, 0.5 mL, 0.5 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 5 4 6' OH room temperature for one hour before being neutralised 5' with 1 M acetic acid. Water (20 mL) was added. Filtration afforded the title compound 1 204 (37 mg, 77%) as an off-white solid. M.p. 61–66 °C. H NMR (300 MHz, d6- DMSO): δ 9.22 (2H, br s, OH), 6.97 (2H, d, J = 8.4 Hz, H2′,6′), 6.87 (1H, d, J = 8.1 Hz, H5), 6.65 (2H, d, J = 8.4 Hz, H3′,5′), 6.29 (1H, dd, J = 2.2 Hz, 8.1 Hz, H6), 6.17 (1H, d, J = 2.2 Hz, H8), 4.14–4-03 (1H, m, H2), 3.11–3.06 (1H, m, H3), 2.96–2.78 (2H, m, H4), 13 0.99 (3H, d, J = 6.6 Hz, 2-CH3). C NMR (75 MHz, CDCl3): δ 156.5 (ArC), 155.9 (ArC), 154.4 (ArC), 130.0 (ArC), 129.0 (ArC), 128.3 (ArC), 126.2 (ArC), 114.9 (ArC),
111.7 (ArC), 102.7 (ArC), 73.6 (C2), 40.3 (C3), 23.5 (C4), 16.2 (CH3). IR (KBr): νmax 3447 (s), 2978 (w), 2931 (w), 1625 (s), 1513 (s), 1456 (m), 1380 (w), 1248 (m), 1231 (m), 1157 (s), 1140 (m), 1118 (s), 1062 (w), 1004 (w), 985 (w), 840 (m), 735 (w), 700 -1 -1 -1 (w) cm . UV-vis (MeOH): λmax 283 nm (ε 1,235 cm M ), 210 (6,564). HRMS (+ESI): + Found m/z 279.0992, [M+Na] ; C16H16O3Na required 279.0997.
2-Ethyl-3-(4-hydroxyphenyl)chroman-7-ol (205) 8 HO O 2 The isoflavan 202 (66 mg, 0.19 mmol) was dissolved in 3 2' methanol (3 mL). Aqueous KOH (1 M, 0.4 mL, 0.4 mmol) 6 3' 5 4 6' OH 5' ‐ 170 ‐ was added dropwise. The mixture was stirred at room temperature for one hour before being neutralised with 1 M acetic acid. Water (20 mL) was added. Filtration afforded the title compound 205 (42 mg, 81%) as an off-white solid. M.p. 74–78 °C. 1H NMR
(300 MHz, d6-DMSO): δ 9.18 (2H, br s, OH), 6.94 (2H, d, J = 8.4 Hz, H2′,6′), 6.83 (IH, d, J = 8.1 Hz, H5), 6.61 (2H, d, J = 8.4 Hz, H3′,5′), 6.26 (1H, dd, J = 2.6 Hz, 8.1 Hz, H6), 6.16 (1H, d, J = 2.6 Hz, H8), 4.10-–4.00 (1H, m, H2), 3.14–3.09 (1H, m, H3),
2.94–2.72 (2H, m, H4), 1.39–1.16 (2H, m, CH2), 0.85 (3H, dd (app. t), J = 7.3 Hz, CH3). 13 C NMR (75 MHz, CDCl3): δ 155.9 (ArC), 154.8 (ArC), 151.7 (ArC), 129.0 (ArC), 123.4 (ArC), 122.2 (ArC), 118.8 (ArC), 116.2 (ArC), 111.7 (ArC), 102.7 (ArC), 80.1
(C2), 40.3 (C3), 23.5 (C4), 23.7 (CH2), 10.1 (CH3). IR (KBr): νmax 3430 (s), 3026 (w), 2965 (m), 2929 (m), 2876 (w), 1656 (w), 1620 (s), 1598 (s), 1513 (s), 1461 (m), 1367 (w), 1304 (w), 1240 (m), 1176 (w), 1157 (s), 1134 (w), 1114 (m), 1037 (w), 997 (m), -1 -1 -1 831 (m) cm . UV-vis (MeOH): λmax 282 nm (ε 838 cm M ), 223 (2,752), 206 (5,428). + HRMS (+ESI): Found m/z 293.1151, [M+H] ; C17H18O3Na required 293.1154.
1-(7-Hydroxy-3-(4-hydroxyphenyl)chroman-2- yl)pyrrolidin-2-one (206) O 3"
8 The isoflavan 203 (83 mg, 0.20 mmol) was dissolved in HO O 2 N 4" 5" methanol (10 mL). Aqueous KOH (1 M, 1.0 mL, 1.0 3 2' 6 3' mmol) was added dropwise. The mixture was stirred at 5 4 6' OH room temperature for one hour before being neutralised 5' with 1 M acetic acid. Water (20 mL) was added. Filtration afforded the title compound 206 (59 mg, 91 %) as a grey solid. M.p. 284–288 °C (decomp.). 1H NMR (300 MHz, d6-DMSO): δ 9.32 (1H, br s, OH), 9.28 (1H, br s, OH), 7.01 (2H, d, J = 8.7 Hz, H2′,6′), 6.92 (1H, d, J = 8.2 Hz, H5), 6.65 (2H, d, J = 8.7 Hz, H3′,5′), 6.36 (1H, dd, J = 2.3 Hz, 8.2 Hz, H6), 6.25 (1H, d, J = 2.3 Hz, H8), 5.92 (1H, d, J = 3.1 Hz, H2), 3.13–2.96 (3H, m, H3, H4a, H5″a), 3.03–2.84 (2H, m, H5″b, H4b), 2.74–2.70 (1H, m, H3″a), 2.19–2.09 b 13 (1H, m, H3″ ), 1.82–1.69 (2H, m, H4″). C NMR (75 MHz, d6-DMSO): δ 174.9 (CO), 156.8 (ArC), 156.3 (ArC), 154.1 (ArC), 130.1 (ArC), 129.8 (ArC), 129.1 (ArC), 115.1 (ArC), 111.1 (ArC), 108.9 (ArC), 102.4 (C8), 79.3 (C2), 48.6 (C3), 43.9 (C5″), 30.1
(C3″), 28.9 (C4), 18.1 (C4″). IR (KBr): νmax 3428 (s), 3013 (w), 2929 (m), 2863 (w), 1656 (s), 1624 (s), 1596 (s), 1556 (w), 1516 (w), 1460 (m), 1434 (m), 1421 (w), 1377 (w), 1318 (w), 1291 (m), 1280 (m), 1269 (m), 1248 (m), 1229 (m), 1199 (w), 1176 (w), 1149 (s), 1110 (s), 1055 (m), 1014 (w), 910 (w), 889 (w), 853 (w), 831 (w), 807 (w),
‐ 171 ‐ -1 -1 -1 775 (w), 740 (w), 706 (w) cm . UV-vis (MeOH): λmax 281 nm (ε 987 cm M ), 223 + (3,514), 207 (6,157). HRMS (+ESI): Found m/z 348.1211, [M+H] ; C19H19NO4Na required 348.1212.
1-(2,4-Dihydroxyphenyl)-2-(4-hydroxyphenyl)ethanone (25) Resorcinol 23 (40.03 g, 0.3635 mol), 4- 3' hydroxyphenylacetic acid 24 (55.85 g, 0.3671 mol) and HO OH 2 2'' 1 anhydrous zinc chloride (59.00 g, 0.4328 mol) were 5' 3'' 6' melted at 130 oC for 1.5 hours. The cooled reaction O 6'' OH 5'' mixture was then dissolved in methanol (500 mL) and poured into water (1500 mL). The precipitate was collected to give the title compound 25 (53.90 g, 61%) as an orange powder: M.p. 187-190 °C, Lit222 189–191 °C. 1H NMR
(300 MHz, d6-acetone): δ 12.76 (1H, br s, OH), 9.64 (1H, br s, OH), 8.34 (1H, br s, OH), 7.94 (1H, d, J = 8.9 Hz, H6′), 7.16 (2H, d, J = 8.7 Hz, H2″,6″), 6.78 (2H, d, J = 8.7 Hz, H3″,5″), 6.43 (1H, dd, J = 2.4 Hz, 8.8 Hz, H5′), 6.32 (1H, d, J = 2.4 Hz, H3′), 4.16 (2H, s, H2).
1-(2,4-Dihydroxy-3-methylphenyl)-2-(4-hydroxyphenyl)ethanone (218)103 2-Methylresorcinol 217 (10.04 g, 80.94 mmol) and 4- HO OH hydroxyphenylacetic acid 24 (12.19 g, 80.12 mmol) were 2 2'' 5' 1 3'' dissolved in boron trifluoride diethyletherate. The 6' O 6'' OH mixture was heated to 80 °C, under an atmosphere of 5'' nitrogen, for 90 minutes. Once cooled, the reaction mixture was poured into water (500 mL). The precipitate was collected to give the title compound 218 (18.05 g, 87%) as a 1 bright yellow powder: M.p. 178–182 °C. H NMR (300 MHz, d6-acetone): δ 13.00 (1H, br s, OH), 10.56 (1H, br s, OH), 9.28 (1H, br s, OH), 7.79 (1H, d, J = 8.9 Hz, H6′), 7..05 (2H, d, J = 8.5 Hz, H2″,6″), 6.67 (2H, d, J = 8.5 Hz, H3″,5″), 6.43 (1H, d, J = 8.9 Hz,
H5′), 4.16 (s, 2H, H2), 1.92 (3H, s, CH3).
7-Hydroxy-3-(4-hydroxyphenyl)-2-methyl-4H-chromen-4-one (228)
8 The deoxybenzoin 25 (1.99 g, 8.15 mmol) was dissolved HO O 2 in triethylamine (20 mL). Acetic anhydride (3.0 mL, 32 3 2' 6 3' 5 mmol) was added. The mixture was heated at reflux for O 6' OH 5'
‐ 172 ‐ 20 hours. The cooled reaction mixture was poured into water (200 mL) and the resulting mixture acidified to pH 5 with 2 M HCl. The precipitate was collected and suspended in methanol (10 mL). To this suspension was added 1 M NaOH (25 mL). The mixture was heated at reflux for 2 hours. Once cooled, the reaction mixture was poured into water (100 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 228 (1.36 g, 62%) as an orange-brown powder. M.p. 222 1 311–314 °C, Lit 315–317 °C. H NMR (300 MHz, d6-DMSO): δ 9.52 (1H, br s, OH), 9.20 (1H, br s, OH), 8.40 (1H, d, J = 8.6 Hz, H5), 7.57 (2H, d, J=8.7 Hz, H2′,6′), 7.40-
7.31 (4H, m, H6, H8, H-3′,5′), 2.50 (3H, s, CH3).
2-Ethyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one (229)
8 The deoxybenzoin 25 (2.01 g, 8.24 mmol) was dissolved HO O 2 in triethylamine (20 mL). Propionic anhydride (4.5 mL, 3 2' 6 3' 5 35 mmol) was added. The mixture was heated at reflux O 6' OH for 26 hours. The cooled reaction mixture was poured 5' into water (150 mL) and the resulting mixture acidified to pH 6 with 2 M HCl. The precipitate was and suspended in methanol (10 mL). To this suspension was added 2 M NaOH (5 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (200 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 229 (902 mg, 138 1 39%) as a tan powder. M.p. 257–260 °C, Lit 266 °C. H NMR (300 MHz, d6-DMSO): δ 10.20 (1H, br s, OH), 9.54 (1H, br s, OH), 7.99 (1H, d, J = 8.6 Hz, H5), 7.03 (2H, d, J = 8.7 Hz, H2′,6′), 6.99 (1H, dd, J = 2.3 Hz, 8.7 Hz, H6), 6.91-6.86 (3H, m, H-3′,5′, H8),
2.51 (2H, q, J = 7.6 Hz, CH2CH3), 1.14 (3H, t, J = 7.6 Hz, CH2CH3).
7-Hydroxy-3-(4-hydroxyphenyl)-2-propyl-4H-chromen-4-one (230)
8 The deoxybenzoin 25 (1.04 g, 4.27 mmol) was dissolved HO O 2 in triethylamine (10 mL). Butyric anhydride (2.20 mL, 3 2' 6 3' 13.4 mmol) was added. The mixture was heated at reflux 5 O 6' OH for 22 hours. The cooled reaction mixture was poured 5' into water (60 mL) and the resulting mixture acidified to pH 5 with 2M HCl. The precipitate was collected and suspended in methanol (10 mL). To this suspension was added 2 M NaOH (5 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (50 mL) and the resulting mixture
‐ 173 ‐ neutralised with 2 M HCl. The precipitate was collected to give the title compound 230 1 (886 mg, 70%) as an orange-brown powder. M.p. 222–224 °C. H NMR (300 MHz, d6- acetone): δ 9.55 (1H, br s, OH), 8.40 (1H, br s, OH), 7.96 (1H, d, J = 8.6 Hz, H5), 7.09 (2H, d, J = 8.7 Hz, H2′,6′), 6.94 (1H, dd, J = 2.3 Hz, 8.7 Hz, H6), 6.91-6.85 (3H, m, H-
3′,5′, H8), 2.54 (2H, t, J = 7.6 Hz, CH2CH2CH3), 1.72 (2H, sextet, J = 7.6 Hz, 13 CH2CH2CH3), 0.90 (3H, t, J = 7.6 Hz, CH2CH2CH3). C NMR (75 MHz, d6-acetone): δ 176.5 (CO), 166.1 (ArC), 163.2 (ArC), 158.6 (ArC), 157.8 (ArC), 132.7 (ArC), 128.3 (ArC), 125.6 (ArC), 123.8 (ArC), 117.7 (ArC), 115.8 (ArC), 115.2 (ArC), 103.1 (ArC),
35.0 (CH2CH2CH3), 21.5 (CH2CH2CH3), 14.1 (CH2CH2CH3). IR (KBr): νmax 3481 (s), 3413 (s), 3123 (m), 2967 (m), 2929 (m), 2870 (w), 1653 (w), 1625 (s), 1616 (s), 1558 (s), 1541 (s), 1517 (s), 1508 (s), 1457 (m), 1436 (m), 1395 (m), 1263 (s), 1231 (m), 1173 (m), 1125 (m), 1005 (w), 956 (w), 854 (m), 835 (w), 785 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 297 nm (ε 7,511 cm M ), 241 (14,508), 212 (13,380), 202 (13,676). + HRMS (+ESI): Found m/z 297.1117, [M+H] ; C18H17O4 required 297.1121.
7-Hydroxy-3-(4-hydroxyphenyl)-2-ispropyl-4H-chromen-4-one (231)
The deoxybenzoin 25 (0.983 g, 4.02 mmol) was 8 HO O 2 dissolved in triethylamine (10 mL). Isobutyric anhydride 3 2' 6 3' (2.20 mL, 13.3 mmol) was added. The mixture was 5 O 6' OH heated at reflux for 22 hours. The cooled reaction mixture 5' was poured into water (60 mL) and the resulting mixture acidified to pH 5 with 2 M HCl. The precipitate was collected and suspended in methanol (10 mL). To this suspension was added 2 M NaOH (5 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (50 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 231 (855 mg, 72%) as a tan powder. M.p. 280–283 °C. 1H NMR (300
MHz, d6-acetone): δ 9.38 (1H, br s, OH), 8.48 (1H, br s, OH), 7.95 (1H, d, J = 8.8 Hz, H5), 7.09 (2H, d, J = 8.7 Hz, H2′,6′), 6.97-6.86 (4H, m, H3′,5′, H6, H8), 2.99 (1H, 13 septet, J = 6.9 Hz, CH(CH3)2), 1.25 (6H, d, J = 6.9 Hz, CH(CH3)2). C NMR (75 MHz, d6-acetone): δ 176.7 (CO), 169.7 (ArC), 163.7 (ArC), 158.7 (ArC), 157.8 (ArC), 132.6 (ArC), 128.3 (ArC), 125.6 (ArC), 122.2 (ArC), 117.7 (ArC), 115.9 (ArC), 115.2 (ArC),
103.1 (ArC), 31.8 (CH(CH3)2), 20.4 (CH(CH3)2). IR (KBr): νmax 3245 (s), 2976 (m), 2876 (w), 1618 (s), 1594 (s), 1571 (s), 1515 (s), 1459 (m), 1401 (m), 1377 (m), 1328 (w), 1264 (m), 1238 (s), 1172 (m), 1115 (m), 1062 (w), 991 (m), 955 (w), 845 (w), 805
‐ 174 ‐ -1 -1 -1 (w), 792 (w) cm . UV-vis (MeOH): λmax 296 nm (ε 7,704 cm M ), 241 (15,557), 230 + (15,230), 202 (17,453). HRMS (+ESI): Found m/z 297.1116, [M+H] ; C18H17O4 required 297.1121.
2-Butyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one (232)
8 The deoxybenzoin 25 (1.05 g, 4.28 mmol) was dissolved HO O 2 in triethylamine (10 mL). Valeric anhydride (2.70 mL, 3 2' 6 3' 5 13.7 mmol) was added. The mixture was heated at reflux O 6' OH for 22 hours. The cooled reaction mixture was poured 5' into water (60 mL) and the resulting mixture acidified to pH 5 with 2 M HCl. The precipitate was collected and suspended in methanol (10 mL). To this suspension was added 2 M NaOH (5 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (50 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 232 1 (1.12 g, 84%) as a tan powder. M.p. 198–202 °C. H NMR (300 MHz, d6-acetone): δ 9.54 (1H, br s, OH), 8.40 (1H, br s, OH), 7.95 (1H, d, J = 8.7 Hz, H5), 7.10 (2H, d, J = 8.7 Hz, H2′,6′), 6.94 (1H, dd, J = 2.3 Hz, 8.7 Hz, H6), 6.91-6.86 (3H, m, H3′,5′, H8),
2.57 (2H, t, J = 7.6 Hz, CH2CH2CH2CH3), 1.68 (2H, tt (app. quintet), J = 7.6 Hz,
CH2CH2CH2CH3), 1.31 (2H, tq (app. sextet), J=7.6 Hz, CH2CH2CH2CH3), 0.84 (3H, t, 13 J = 7.6 Hz, CH2CH2CH2CH3). C NMR (75 MHz, d6-acetone): δ 176.5 (CO), 166.3 (ArC), 162.1 (ArC), 158.6 (ArC), 157.8 (ArC), 132.7 (ArC), 128.3 (ArC), 125.6 (ArC), 123.6 (ArC), 117.7 (ArC), 115.8 (ArC), 115.2 (ArC), 103.8 (ArC), 32.8
(CH2CH2CH2CH3), 27.0 (CH2CH2CH2CH3), 23.0 (CH2CH2CH2CH3), 14.1
(CH2CH2CH2CH3). IR (KBr): νmax 3430 (s), 3128 (s), 2958 (m), 2932 (m), 2860 (w), 1625 (s), 1611 (s), 1545 (s), 1517 (s), 1475 (w), 1459 (w), 1437 (w), 1401 (m), 1291 (w), 1271 (s), 1260 (s), 1230 (s), 1172 (m), 1124 (m), 1020 (w), 1008 (w), 854 (m), 833 -1 -1 -1 (w), 795 (w) cm . UV-vis (MeOH): λmax 297 nm (ε 8,245 cm M ), 241 (16,469), 203 + (16,293). HRMS (+ESI): Found m/z 311.1273, [M+H] ; C19H19O4 required 311.1278.
7-Hydroxy-3-(4-hydroxyphenyl)-2-trifluoromethyl-4H-chromen-4-one (233)
The deoxybenzoin 25 (2.23 g, 9.13 mmol) was dissolved 8 2 HO O CF3 in triethylamine (20 mL). Trifluoroacetic anhydride (4.00 3 2' 6 3' 5 mL, 28.8 mmol) was added. The mixture was heated at O 6' OH 5'
‐ 175 ‐ 1 6-DMSO): δ 9.84 (1H, br s, OH), 9.60 (1H, br s, OH), 7.89 (1H, d, J = 8.7 Hz, H5), 7.02 (2H, d, J = 8.5 Hz, H2′,6′), 6.97 (1H, dd, J = 1.9, 8.7 Hz, H6), 6.89 (1H, d, J = 1.9 Hz, H8), 6.78 (2H, d, J = 8.6 Hz, H3′,5′). 13 C NMR (75 MHz, d6-DMSO): δ 175.5 (CO), 163.7 (ArC), 157.6 (ArC), 154.7 (ArC),
153.8 (ArC), 131.1 (ArC), 127.5 (ArC), 119.7 (ArC or CF3), 116.2 (ArC or CF3), 115.4
(ArC), 114.7 (ArC), 102.1 (ArC). IR (KBr): νmax 3379 (s), 3205 (m), 2861 (w), 1657 (w), 1631 (s), 1611 (s), 1583 (s), 1555 (w), 1518 (m), 1503 (w), 1461 (w), 1443 (w), 1396 (w), 1267 (s), 1250 (s), 1223 (s), 1202 (s), 1191 (s), 1174 (m), 1157 (s), 1146 (m), -1 1108 (m), 1056 (w), 943 (m), 848 (w), 828 (w), 775 (w) cm . UV-vis (MeOH): λmax 308 nm (ε 8,862 cm-1M-1), 242 (19,286), 209 (21,252). HRMS (+ESI): Found m/z + 323.0520, [M+H] ; C16H10F3O4 required 323.0526.
7-Hydroxy-3-(4-hydroxyphenyl)-2-phenyl-4H- chromen-4-one (234) 3'' 2'' 4''
The deoxybenzoin 25 (2.00 g, 8.19 mmol) was dissolved 8 2 HO O 5'' 6'' in triethylamine (30 mL). Benzoyl chloride (3.00 mL, 3 2' 6 25.8 mmol) was added. The mixture was heated at reflux 5 3' O 6' OH for 22 hours. The cooled reaction mixture was poured 5' into water (200 mL). The precipitate was collected and suspended in methanol (30 mL). To this suspension was added 1 M NaOH (25 mL). The mixture was heated at reflux for 2 hours. Once cooled, the reaction mixture was poured into water (300 mL) and the resulting mixture neutralised with 1 M HCl. The precipitate was collected to give the title compound 234 (1.18 g, 44%) as a pale brown powder. M.p. 292–295 °C. 1H NMR
(300 MHz, d6-acetone) δ 9.38 (1H, br s, OH), 8.48 (1H, br s, OH), 8.03 (1H, d, J = 8.6 Hz, H5), 7.49-7.29 (5H, m, ArH), 7.06-6.95 (4H, m, ArH), 6.74 (2H, d, J = 8.7 Hz, 13 H3′,5′). C NMR (75 MHz, d6-acetone): δ 176.8 (CO), 163.4 (ArC), 161.5 (ArC), 158.8 (ArC), 157.7 (ArC), 135.0 (ArC), 133.6 (ArC), 130.6 (ArC), 130.5 (ArC), 129.0 (ArC), 128.5 (ArC), 125.3 (ArC), 123.2 (ArC), 117.7 (ArC), 115.7 (ArC), 115.6 (ArC),
‐ 176 ‐ 103.3 (ArC). IR (KBr): νmax 3419 (s), 3281 (s), 1620 (s), 1563 (s), 1515 (s), 1491 (w), 1452 (s), 1391 (m), 1327 (w), 1270 (s), 1231 (m), 1173 (s), 1114 (w), 1053 (w), 1001 (w), 963 (w), 929 (w), 827 (w), 809 (w), 788 (w), 779 (w), 758 (w), 695 (w) cm-1. UV- -1 -1 vis (MeOH): λmax 308 nm (ε 5,153 cm M ), 203 (18,432). HRMS (+ESI): Found m/z + 331.0961, [M+H] ; C21H15O4 required 331.0965.
7-Hydroxy-3-(4-hydroxyphenyl)-2-(pyridin-4-yl)-4H-chromen-4-one (235) The deoxybenzoin 25 (1.06 g, 4.35 mmol) was dissolved 3'' 2'' N in triethylamine (10 mL). Isonicotinic anhydride (3.23 g, 8 2 HO O 5'' 6'' 14.1 mmol) was added. The mixture was heated at reflux 3 2' 6 3' 5 for 22 hours. The cooled reaction mixture was poured O 6' OH into water (60 mL) and the resulting mixture acidified to 5' pH 5 with 2M HCl. The precipitate was collected and suspended in methanol (10 mL). To this suspension was added 2 M NaOH (5 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (50 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 235 (832 mg, 58%) as a pale yellow powder. M.p. 302–306 °C 1 (decomp.). H NMR (300 MHz, d6-DMSO): δ 10.82 (1H, br s, OH), 9.53 (1H, br s, OH), 8.56 (2H, d, J = 6.1 Hz, H3″,5″), 7.94 (1H, d, J = 8.7 Hz, H5), 7.32 (2H, d, J = 6.1 Hz, H2″,6″), 6.98-6.90 (4H, m, H2′,6′, H6, H8), 6.69 (2H, d, J = 8.7 Hz, H3′,5′). 13C NMR
(75 MHz, d6-DMSO): δ 175.6 (CO), 163.0 (ArC), 159.7 (ArC), 157.3 (ArC), 157.0 (ArC), 149.7 (ArC), 132.2 (ArC), 130.0 (ArC), 127.4 (ArC), 127.2 (ArC), 123.3 (ArC),
122.4 (ArC), 115.5 (ArC), 115.2 (ArC), 115.0 (ArC), 102.2 (ArC). IR (KBr): νmax 3427 (s), 3255 (m), 2918 (w), 2849 (w), 2802 (w), 2685 (w), 2628 (w), 1627 (s), 1605 (s), 1569 (s), 1516 (s), 1460 (m), 1417 (m), 1389 (m), 1285 (s), 1262 (s), 1254 (s), 1237 (m), 1174 (m), 1109 (w), 1070 (w), 1051 (w), 1010 (w), 934 (w), 845 (w), 827 (w), 785 (w) -1 -1 -1 cm . UV-vis (MeOH): λmax 316 nm (ε 6,626 cm M ), 274 (10,437), 237 (14,909), 203 + (20,277). HRMS (+ESI): Found m/z 332.0912, [M+H] ; C20H14NO4 required 332.0917.
7-Hydroxy-3-(4-hydroxyphenyl)-2,8-dimethyl-4H-chromen-4-one (236) The deoxybenzoin 218 (1.04 g, 4.27 mmol) was HO O 2 dissolved in triethylamine (20 mL). Acetic anhydride (4.5 3 2' 6 3' mL, 48 mmol) was added. The mixture was heated at 5 O 6' OH 5'
‐ 177 ‐ 2, 80 % DCM/ethyl acetate) gave the title compound 236 (157 mg, 13%) as a beige powder. M.p. 1 312–314 °C (decomp.). H NMR (300 MHz, d6-DMSO): δ 10.59 (1H, br s, OH), 9.45 (1H, br s, OH), 7.75 (1H, d, J = 8.6 Hz, H5), 7.09 (2H, d, J = 8.7 Hz, H2′,6′), 6.94 (1H, d, J = 8.6 Hz, H6), 6.80 (2H, d, J = 8.7 Hz, H3′,5′), 2.31 (3H, s, CH3), 2.24 (3H, s, CH3). 13 C NMR (75 MHz, d6-DMSO): δ 175.6 (CO), 165.8 (ArC), 159.7 (ArC), 156.7 (ArC), 155.2 (ArC), 131.5 (ArC), 123.5 (ArC), 123.2 (ArC), 121.1 (ArC), 115.6 (ArC), 114.9
(ArC), 113.5 (ArC), 110.4 (ArC), 12.8 (CH3), 11.6 (CH3). IR (KBr): νmax 3251 (s), 2976 (w), 2929 (w), 1654 (w), 1628 (w), 1579 (w), 1514 (w), 1432 (w), 1381 (w), 1359 (w), 1342 (w), 1326 (w), 1273 (s), 1250 (m), 1224 (s), 1173 (m), 1110 (w), 1093 (m), 1059 (w), 1017 (w), 977 (w), 969 (w), 885 (w), 842 (w), 832 (w), 803 (m), 793 (m), 775 -1 -1 -1 (w) cm . UV-vis (MeOH): λmax 300 nm (ε 11,101 cm M ), 249 (19,302). HRMS + (+ESI): Found m/z 305.0788, [M+Na] ; C17HO14 4Na required 305.0790.
2-Ethyl-7-hydroxy-3-(4-hydroxyphenyl)-8-methyl-4H-chromen-4-one (237) The deoxybenzoin 218 (2.00 g, 7.44 mmol) was HO O 2 dissolved in triethylamine (20 mL). Propionyl chloride 3 2' 6 3' (2.5 mL, 29 mmol) was added. The mixture was heated at 5 O 6' OH reflux for 24 hours. The cooled reaction mixture was 5' poured into water (200 mL) and the resulting mixture was neutralised with 1 M HCl. The precipitate was collected by vacuum filtration and suspended in methanol (20 mL). To this suspension was added 1 M NaOH (20 mL). The mixture was heated at reflux for one hour. Once cooled, the reaction mixture was poured into water (300 mL) and the resulting mixture neutralised with 2 M HCl. The resulting precipitate was collected.
Chromatography (SiO2, 80 % DCM/ethyl acetate) gave the title compound 237 (507 mg, 1 23%) as a beige powder. M.p. 294–296 °C. H NMR (300 MHz, d6-DMSO): δ 10.53 (1H, br s, OH), 9.46 (1H, br s, OH), 7.73 (1H, d, J = 8.6 Hz, H5), 7.03 (2H, d, J = 8.7 Hz, H2′,6′), 6.98 (1H, d, J = 8.6 Hz, H6), 6.78 (2H, d, J = 8.7 Hz, H3′,5′), 2.52 (2H, q, 13 2.31 J = 7.6 Hz, CH2CH3), 2.24 (3H, s, CH3), 1.19 (3H, t, J = 7.6 Hz, CH2CH3). C
‐ 178 ‐ 6 (ArC), 123.6 (ArC), 123.5 (ArC), 121.1 (ArC), 115.6 (ArC), 114.9
(ArC), 113.5 (ArC), 110.6 (ArC), 25.6 (CH2CH3), 11.6 (CH3), 7.9 (CH2CH3). IR (KBr):
νmax 3421 (s), 2975 (w), 2927 (w), 1654 (w), 1621 (s), 1581 (s), 1534 (w), 1515 (s), 1491 (w), 1432 (m), 1407 (m), 1373 (w), 1316 (w), 1272 (m), 1227 (m), 1175 (w), 1093 -1 (m), 1016 (w), 847 (w), 830 (w), 794 (w) cm . UV-vis (MeOH): λmax 304 nm (ε 7,319 -1 -1 + cm M ), 251 (8,389). HRMS (+ESI): Found m/z 319.0945, [M+Na] ; C18H16O4Na required 319.0946.
7-Hydroxy-3-(4-hydroxyphenyl)-8-methyl-2-propyl-4H-chromen-4-one (238) The deoxybenzoin 218 (2.04 g, 7.88 mmol) was HO O 2 dissolved in triethylamine (20 mL). Butyric anhydride 3 2' 6 3' (4.5 mL, 28 mmol) was added. The mixture was heated at 5 O 6' OH reflux for 26 hours. The cooled reaction mixture was 5' poured into water (150 mL) and the resulting mixture acidified to pH 6 with 2M HCl. The precipitate was collected and suspended in methanol (20 mL). To this suspension was added 1 M NaOH (12 mL). The mixture was heated at reflux for 45 minutes. Once cooled, the reaction mixture was poured into water (200 mL) and the resulting mixture neutralised with 2 M HCl. The precipitate was collected to give the title compound 238 (1.30g, 53%) as a dark pink powder. M.p. 269–272 °C (decomp.). 1H NMR (300 MHz, d6-DMSO): δ 10.64 (1H, br s, OH), 9.48 (1H, br s, OH), 7.73 (1H, d, J = 8.6 Hz, H5), 7.03 (2H, d, J = 8.7 Hz, H2′,6′), 6.98 (1H, d, J = 8.6 Hz, H6), 6.76 (2H, d, J = 8.7 Hz,
H3′,5′), 2.50 (2H, t, J = 7.2 Hz, CH2CH2CH3), 2.24 (3H, s, CH3), 1.67 (2H, sextet, J = 13 7.2 Hz, CH2CH2CH3), 0.85 (3H, t, J = 7.6 Hz, CH2CH2CH3). C NMR (75 MHz, d6- DMSO): δ 175.7 (CO), 164.7 (ArC), 160.0 (ArC), 156.6 (ArC), 155.1 (ArC), 131.5 (ArC), 123.6 (ArC), 123.5 (ArC), 121.8 (ArC), 115.4 (ArC), 114.9 (ArC), 113.5 (ArC),
110.5 (ArC), 33.7 (CH2CH2CH3), 20.1 (CH2CH2CH3), 13.5 (CH3), 7.9 (CH2CH2CH3).
IR (KBr): νmax 3424 (s), 2963 (w), 2929 (m), 1660 (w), 1622 (s), 1580 (s), 1557 (w), 1515 (s), 1507 (w), 1434 (s), 1402 (m), 1360 (w), 1271 (m), 1230 (m), 1174 (w), 1095 -1 -1 -1 (m), 791 (w) cm . UV-vis (MeOH): λmax 302 nm (ε 8,886 cm M ), 244 (18,734), 204 + (16,003). HRMS (+ESI): Found m/z 311.1274, [M+H] ; C19H19O4 required 311.1278.
‐ 179 ‐ 7-Hydroxy-3-(4-hydroxyphenyl)-8-methyl-2-phenyl-4H-chromen-4-one (239) The deoxybenzoin 218 (2.01 g, 7.78 mmol) was 3" 2" 4" dissolved in triethylamine (30 mL). Benzoyl chloride (2.5 2 HO O 5" 6" mL, 29 mmol) was added. The mixture was heated at 3 2' 6 3' 5 reflux for 48 hours. The cooled reaction mixture was O 6' OH poured into water (300 mL) and the resulting mixture 5' was neutralised with 2 M HCl. The precipitate was collected by vacuum filtration and suspended in methanol (30 mL). To this suspension was added 1 M NaOH (25 mL). The mixture was heated at reflux for one hour. Once cooled, the reaction mixture was poured into water (300 mL) and the resulting mixture neutralised with 2M HCl. The resulting precipitate was collected to give the title compound 239 (488 mg, 19%) as a 1 beige powder. M.p. 341–344 °C ( decomp). H NMR (300 MHz, d6-DMSO): δ 10.64 (1H, br s, OH), 9.48 (1H, br s, OH), 7.73 (1H, d, J = 8.6 Hz, H5), 7.42–7.32 (5H, m, ArH), 7.03 (2H, d, J = 8.7 Hz, H2′,6′), 6.96 (1H, d, J = 8.6 Hz, H6), 6.74 (2H, d, J = 8.7 13 Hz, H3′,52.24 (3H, s, CH3). C NMR (75 MHz, d6-DMSO): δ 176.1 (CO), 160.2 (ArC), 159.8 (ArC), 156.6 (ArC), 155.3 (ArC), 133.6 (ArC), 132.2 (ArC), 129.8 (ArC), 129.2 (ArC), 128.1 (ArC), 123.4 (ArC), 121.2 (ArC), 114.9 (ArC), 113.9 (ArC), 110.9 (ArC),
8.1 (CH3). IR (KBr): νmax 3270 (s), 2927 (w), 1658 (w), 1626 (s), 1604 (s), 1591 (s), 1567 (m), 1536 (w), 1515 (s), 1492 (w), 1435 (s), 1392 (s), 1350 (m), 1333 (w), 1277 (s), 1261 (m), 1223 (s), 1176 (m), 1152 (w), 1094 (m), 1053 (w), 929 (w), 841 (w), 832 -1 (w), 795 (w), 787 (w), 771 (w), 757 (w) cm . UV-vis (MeOH): λmax 311 nm (ε 7,232 cm-1M-1), 254 (15,909), 202 (25,930). HRMS (+ESI): Found m/z 345.1115, [M+H]+;
C22H17O4 required 345.1121.
7-Acetoxy-3-(4-acetoxyphenyl)-2-propyl-4H-chromen-4-one (243)
8 A mixture of isoflavone 230 (1.67 g, 5.63 mmol), AcO O 2 potassium carbonate (1.74 g, 12.6 mmol) and acetic 3 2' 6 3' 5 anhydride (1.90 mL, 20.1 mmol) was heated at reflux O 6' OAc in acetone (15 mL) for one hour. The cooled reaction 5' mixture was neutralised with 2 M HCl and poured into water (25 mL). The precipitate was collected to give the title compound 243 (976 mg, 46%) as a pale orange powder. 1 M.p. 112–115 °C. H NMR (300 MHz, CDCl3) δ 8.23 (1H, d, J = 8.7 Hz, H5), 7.30- 7.24 (3H, m, H H2′,6′, H8), 7.17 (2H, d, J = 8.7 Hz, H3′,5′), 7.12 (1H, dd, J = 2.2 Hz,
8.7 Hz, H6), 2.56 (2H, t, J = 7.4 Hz, CH2CH2CH3), 2.36 (3H, s, OAc), 2.32 (3H, s,
‐ 180 ‐ OAc), 1.73 (2H, sextet, J = 7.4 Hz, CH2CH2CH3), 0.93 (3H, t, J = 7.4 Hz, 13 CH2CH2CH3). C NMR (75 MHz, CDCl3) δ 173.7 (C4), 169.5 (CO), 168.9 (CO), 167.0 (ArC), 156.6 (ArC), 154.6 (ArC), 150.6 (ArC), 131.7 (ArC), 130.5 (ArC), 127.9 (ArC), 123.2 (ArC), 121.8 (ArC), 121.4 (ArC), 119.3 (ArC), 110.9 (ArC), 34.6
(CH2CH2CH3), 21.4 (COCH3), 21.0 (CH2CH2CH3), 13.9 (CH2CH2CH3). IR (KBr):
νmax 3456 (w), 3080 (w), 2968 (w), 2876 (w), 1767 (s), 1647 (s), 1619 (s), 1573 (w), 1507 (m), 1438 (m), 1370 (m), 1329 (w), 1301 (w), 1254 (w), 1217 (s), 1194 (s), 1167 (m), 1147 (s), 1114 (w), 1064 (w), 1038 (w), 1012 (m), 993 (m), 958 (w), 909 (m), 868 -1 -1 -1 (w), 836 (w), 805 (w), 780 (w) cm . UV-vis (MeOH): λmax 295 nm (ε 8,901 cm M ), 232 (20,969), 209 (19,143). HRMS (+ESI): Found m/z 403.1141, [M+Na]+;
C22H20O6Na required 403.1152.
7-Acetoxy-3-(4-acetoxyphenyl)-2-isopropyl-4H-chromen-4-one (244)
A mixture of isoflavone 231 (779 mg, 2.63 mmol), 8 AcO O 2 potassium carbonate (801 mg, 5.80 mmol) and acetic 3 2' 6 3' anhydride (0.90 mL, 9.5 mmol) was heated at reflux in 5 O 6' OAc acetone (15 mL) for one hour. The cooled reaction 5' mixture was neutralised with 2 M HCl and poured into water (25 mL). The precipitate was collected to give the title compound 244 (775 mg, 77%) as a pale brown powder. 1 M.p. 210–212 °C. H NMR (300 MHz, CDCl3): δ 8.23 (1H, d, J = 8.7 Hz, H5), 7.32 (1H, d, J = 2.1 Hz, H8), 7.26 (2H, d, J = 8.8 Hz, H2′,6′), 7.17 (2H, d, J = 8.8 Hz, H3′,5′),
7.12 (1H, dd, J = 2.1 Hz, 8.7 Hz, H6), 3.00 (1H, septet, J = 6.8 Hz, CH(CH3)2), 2.36 13 (3H, s, OAc), 2.32 (3H, s, OAc), 1.25 (6H, d, J=6.8 Hz, CH(CH3)2). C NMR (75
MHz, CDCl3): δ 176.7 (C4), 170.7 (CO), 169.6 (CO), 168.9 (ArC), 156.6 (ArC), 154.6 (ArC), 150.5 (ArC), 131.6 (ArC), 130.5 (ArC), 127.9 (ArC), 121.8 (ArC), 121.5 (ArC),
119.3 (ArC), 110.9 (ArC), 31.4 (CH(CH3)2), 21.4 (COCH3), 20.4 (CH(CH3)2). IR
(KBr): νmax 3440 (w), 3061 (w), 2971 (w), 2936 (w), 2876 (w), 1765 (s), 1650 (s), 1615 (s), 1573 (w), 1507 (m), 1468 (w), 1439 (m), 1395 (w), 1370 (m), 1328 (w), 1246 (m), 1223 (s), 1203 (s), 1166 (m), 1148 (s), 1112 (m), 1056 (w), 1013 (m), 988 (w), 958 (w), -1 909 (w), 877 (w), 857 (w), 819 (w), 796 (w), 775 (w) cm . UV-vis (MeOH): λmax 320 nm (ε 4,469 cm-1M-1), 233 (14,607), 205 (14,892). HRMS (+ESI): Found m/z 403.1141, + [M+Na] ; C22H20O6Na required 403.1152.
‐ 181 ‐ 7-Acetoxy-3-(4-acetoxyphenyl)-2-butyl-4H-chromen-4-one (245)
8 A mixture of isoflavone 232 (1.07 g, 3.43 mmol), AcO O 2 potassium carbonate (1.11 g, 8.03 mmol) and acetic 3 2' 6 3' 5 anhydride (1.10 mL, 11.6 mmol) was heated at reflux O 6' OAc in acetone (15 mL) for one hour. The cooled reaction 5' mixture was neutralised with 2 M HCl and poured into water (25 mL). The precipitate was collected to give the title compound 245 (699 mg, 52%) as a tan powder. M.p. 85– 1 88 °C. H NMR (300 MHz, CDCl3): δ 8.23 (1H, d, J = 8.7 Hz, H5), 7.29 (1H, d, J = 2.1 Hz, H8), 7.26 (2H, d, J = 8.7 Hz, H2′,6′), 7.17 (2H, d, J = 8.7 Hz, H3′,5′), 7.12 (1H, dd,
J = 2.1 Hz, 8.7 Hz, H6), 2.60 (2H, t, J = 7.4 Hz, CH2CH2CH2CH3), 2.36 (3H, s, OAc),
2.32 (3H, s, OAc), 1.67 (2H, quintet, J = 7.4 Hz, CH2CH2CH2CH3), 1.32 (2H, sextet, J 13 = 7.4 Hz, CH2CH2CH2CH3), 0.86 (3H, t, J = 7.4 Hz, CH2CH2CH2CH3). C NMR (75
MHz, CDCl3): δ 176.5 (C4), 169.5 (CO), 168.9 (CO), 167.3 (ArC), 156.6 (ArC), 154.5 (ArC), 150.5 (ArC), 131.7 (ArC), 130.5 (ArC), 127.9 (ArC), 123.0 (ArC), 121.7 (ArC),
121.4 (ArC), 119.3 (ArC), 110.9 (ArC), 32.4 (CH2CH2CH2CH3), 29.7
(CH2CH2CH2CH3), 22.5 (CH2CH2CH2CH3), 21.4 (COCH3), 13.9 (CH2CH2CH2CH3).
IR (KBr): νmax 3428 (w), 3066 (w), 2958 (w), 2870 (w), 1757 (s), 1645 (s), 1623 (s), 1577 (w), 1509 (m), 1468 (w), 1439 (m), 1371 (m), 1248 (m), 1230 (s), 1209 (s), 1193 (s), 1167 (s), 1146 (s), 1121 (w), 1044 (w), 1017 (m), 964 (w), 921 (w), 904 (w), 853 -1 (w), 837 (w, 795 (w), 785 (w), 773 (w) cm . UV-vis (MeOH): λmax 295 nm (ε 7,790 cm-1M-1), 233 (18,360), 210 (16,329). HRMS (+ESI): Found m/z 395.1480, [M+H]+;
C23H23O6 required 395.1489.
7-Acetoxy-3-(4-acetoxyphenyl)-2-trifluoromethyl-4H-chromen-4-one (246)
A mixture of isoflavone 233 (1.63 g, 5.06 mmol), 8 2 AcO O CF3 potassium carbonate (3.04 g, 22.0 mmol) and acetic 3 2' 6 3' 5 anhydride (4.0 mL, 42 mmol) was heated at reflux in O 6' OAc acetone (45 mL) for one hour. The cooled reaction 5' mixture was neutralised with 2 M HCl and poured into water (150 mL). The precipitate was collected to give the title compound 246 (1.46 g, 71%) as a bright yellow powder. 1 M.p. 148–151 °C. H NMR (300 MHz, CDCl3): δ 8.28 (1H, d, J = 8.7 Hz, H5), 7.47 (1H, d, J = 2.1 Hz, H8), 7.34-7.28 (3H, m, H2′,6′, H6), 7.24 (2H, d, J = 8.8 Hz, H3′,5′), 13 2.41 (3H, s, OAc), 2.36 (3H, s, OAc). C NMR (75 MHz, CDCl3): δ 176.3 (C4), 169.2 (CO), 168.5 (CO), 155.7 (ArC), 151.4 (ArC), 131.2 (ArC), 129.5 (ArC), 128.1 (ArC),
‐ 182 ‐ 126.2 (ArC), 122.6 (ArC), 121.6 (ArC or CF3), 121.1 (ArC or CF3), 120.9 (ArC or CF3),
111.9 (ArC), 21.4 (COCH3). IR (KBr): νmax 3431 (w), 3060 (w), 1763 (w), 1695 (w), 1655 (s), 1616 (s), 1511 (m), 1441 (m), 1400 (w), 1371 (m), 1249 (s), 1199 (s), 1172 (s), 1142 (s), 1051 (w), 1013 (m), 942 (w), 901 (w), 846 (w), 788 (w), 732 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 306 nm (ε 5,842 cm M ), 208 (16,951). HRMS (+ESI): Found m/z + 429.0544, [M+Na] ; C20H13F3O6Na required 429.0556.
4-(7-Acetoxy-4-oxo-2-phenyl-4H-chromen-3-yl)phenyl acetate (247) A mixture of isoflavone 234 (710 mg, 2.15 mmol), 3'' 2'' 4'' potassium carbonate (663 mg, 4.80 mmol) and acetic 8 2 AcO O 5'' 6'' anhydride (0.70 mL, 7.4 mmol) was heated at reflux in 3 2' 6 3' acetone (18 mL) for one hour. The cooled reaction 5 O 6' OAc mixture was neutralised with 2 M HCl and poured into 5' water (20 mL). The precipitate was collected to give the title compound 247 (626 mg, 1 70%) as a pale brown powder. M.p. 109–113 °C. H NMR (300 MHz, CDCl3): δ 8.30 (1H, d, J = 8.7 Hz, H5), 7.46-7.24 (6H, m, ArH), 7.22 (2H, d, J = 8.8 Hz, H2′,6′), 7.17 (1H, dd, J = 2.1 Hz, 8.7 Hz, H6), 7.05 (2H, d, J = 8.8 Hz, H3′,5′), 2.37 (3H, s, OAc), 13 2.28 (3H, s, OAc). C NMR (75 MHz, CDCl3) δ 174.9 (C4), 169.1 (CO), 168.6 (CO), 162.0 (ArC), 156.5 (ArC), 154.6 (ArC), 150.2 (ArC), 130.3 (ArC), 130.2 (ArC), 130.0(ArC), 129.6 (ArC), 128.6 (ArC), 128.2 (ArC), 127.8 (ArC), 121.5 (ArC), 121.4
(ArC), 121.3 (ArC), 119.4 (ArC), 110.9 (ArC), 21.4 (COCH3). IR (KBr): νmax 3439 (s), 1762 (s), 1741 (m), 1686 (w), 1639 (s), 1619 (s), 1561 (w), 1508 (w), 1440 (m), 1373 (m), 1264 (m), 1198 (s), 1159 (s), 1110 (w), 1081 (w), 1061 (m), 1018 (w), 967 (w), -1 -1 -1 908 (w), 765 (w), 705 (m) cm . UV-vis (MeOH): λmax 305 nm (ε 4,994 cm M ), 236 + (11,023), 203 (16,027). HRMS (+ESI): Found m/z 415.1167, [M+H] ; C25H19O6 required 415.1176.
7-Acetoxy-3-(4-acetoxyphenyl)-2-(pyridin-4-yl)-4H-chromen-4-one (248)
A mixture of isoflavone 235 (723 mg, 2.18 mmol), 3'' 2'' N potassium carbonate (664 mg, 4.80 mmol) and acetic 8 2 AcO O 5'' anhydride (0.70 mL, 7.4 mmol) was heated at reflux in 6'' 3 2' 6 3' acetone (15 mL) for one hour. The cooled reaction 5 O 6' OAc mixture was neutralised with 2 M HCl and poured into 5' water (25 mL). The precipitate was collected to give the title compound 248 (637 mg,
‐ 183 ‐ 70%) as a pale yellow powder. M.p. 163–166 °C (decomp.). 1H NMR (300 MHz,
CDCl3) δ 8.59 (2H, d, J = 6.1 Hz, H3″,5″), 8.31 (1H, d, J = 8.8 Hz, H5), 7.40 (1H, d, J = 2.1 Hz, H8), 7.26 (2H, d, J = 6.1 Hz, H2″,6″), 7.24-7.18 (3H, m, H2′,6′, H6), 7.10 (2H, 13 d, J = 8.7 Hz, H3′,5′), 2.38 (3H, s, OAc), 2.30 (3H, s, OAc). C NMR (75 MHz, CDCl3) δ 176.4 (C4), 169.1 (CO), 168.7 (CO), 162.6 (ArC), 156.6 (ArC), 155.1 (ArC), 151.0 (ArC), 150.1 (ArC), 133.1 (ArC), 132.3 (ArC), 129.1 (ArC), 127.9 (ArC), 123.5 (ArC),
122.0 (ArC), 121.5 (ArC), 120.0 (ArC), 115.8 (ArC), 111.2 (ArC), 21.4 (COCH3). IR
(KBr): νmax 3436 (w), 3113 (w), 2917 (w), 1752 (s), 1631 (s), 1619 (s), 1573 (w), 1542 (w), 1505 (w), 1488 (w), 1442 (m), 1418 (w), 1369 (m), 1216 (s), 1163 (s), 1138 (w), 1111 (w), 1044 (m), 1020 (m), 967 (w), 913 (w), 837 (w), 706 (w), 675 (w) cm-1. UV- -1 -1 vis (MeOH): λmax 307 nm (ε 4,777 cm M ), 217 (11,589). HRMS (+ESI): Found m/z + 416.1121, [M+H] ; C24H18NO6 required 416.1129.
4-(7-Acetoxy-4-hydroxy-2-propylchroman-3-yl)phenyl acetate (249)
8 A suspension of isoflavone 243 (517 mg, 1.36 mmol) AcO O 2 and 5% palladium on charcoal (2.76 g) in ethyl acetate 3 2' 6 3' (10 mL) was stirred under hydrogen (1 atm) for 7 days 5 OH 6' OAc at room temperature. The reaction mixture was filtered 5' through a plug of Celite and evaporated in vacuo to give the title compound 249 (336 1 mg, 64%) as a beige solid. M.p. 74–77 °C. H NMR (300 MHz, CDCl3) δ 7.51 (1H, d, J = 8.5 Hz, trans H5), 7.49 (1H, d, J = 8.4 Hz, cis H5), 7.22 (2H, d, J = 8.6 Hz, trans H2',6'), 7.14 (2H, d, J = 8.7 Hz, cis H2',6'), 7.01 (2H, d, J = 8.7 Hz, cis H-3',5'), 6.99 (2H, d, J = 8.7 Hz, trans H3',5'), 6.71 (lH, dd, J = 2.3, 8.4 Hz, trans H6), 6.69 (lH, dd, J = 2.3, 8.4 Hz, cis H-6), 6.64 (lH, d, J = 2.3 Hz, trans H-8), 6.63 (lH, d, J = 2.3 Hz, cis H8), 5.18 (1H, br d, J = 6.9 Hz, cis H4), 4.94 (lH, d, J =10.0 Hz, trans H4), 4.43 (lH, dd, J = 2.2, 4.9, 8.1 Hz, cis H2), 4.26 (1H, ddd, J = 2.5, 6.4, 8.1 Hz, trans H2), 3.36 (lH, dd, J = 2.3, 7.1 Hz, cis H3), 2.85 (1H, dd, J = 10.3, 10.3 Hz, trans H-3), 2.32 (3H, s, trans
COCH3), 2.30 (3H, s, cis COCH3), 2.29 (3H, s, trans COCH3), 2.27 (3H, s, cis
COCH3), 1.62–1.30 (8H, m, cis and trans CH2CH2CH3), 0.92 (3H, t, J = 7.4 Hz, cis 13 CH2CH2CH3), 0.89 (3H, t, J = 7.4 Hz, trans CH2CH2CH3). C NMR (75 MHz,
CDCl3): δ 168.7 (CO), 166.9 (CO), 156.6 (ArC), 154.4 (ArC), 150.4 (ArC), 131.2 (ArC), 130.3 (ArC), 127.7 (ArC), 123.0 (ArC), 121.8 (ArC), 119.1 (ArC), 110.7 (ArC),
94.1 (C2), 76.5 (C4), 34.4 (C3, CH2CH2CH3), 21.3 (COCH3), 21.2 (COCH3), 20.8
(CH2CH2CH3), 13.7 (CH2CH2CH3). IR (KBr): νmax 3436 (m), 3077 (w), 2963 (w),
‐ 184 ‐ 2935 (w), 2873 (w), 1765 (s), 1687 (w), 1647 (s), 1618 (s), 1573 (m), 1508 (m), 1462 (w), 1438, (m), 1370 (m), 1329 (w), 1301 (w), 1195 (s), 1167 (s), 1146 (s), 1115 (m), 1063 (w), 1037 (w), 1012 (m), 993 (w), 958 (w), 909 (m), 868 (w), 835 (w), 804 (w), -1 -1 -1 677 (w) cm . UV-vis (MeOH): λmax 294 nm (ε 4,642 cm M ), 243 (6,816), 224 + (6,547). HRMS (+ESI): Found m/z 407.1454, [M+Na] ; C22H24O6Na required 407.1465.
4-(7-Acetoxy-4-hydroxy-2-isopropylchroman-3-yl)phenyl acetate (250)
A suspension of isoflavone 244 (497 mg, 1.31 mmol) 8 AcO O 2 and 5% palladium on charcoal (2.44 g) in ethyl acetate 3 2' 6 3' (10 mL) was stirred under hydrogen (1 atm) for 7 days 5 OH 6' OAc at room temperature. The reaction mixture was filtered 5' through a plug of Celite and evaporated in vacuo to give the title compound 250 (381 1 mg, 76%) as a beige solid. M.p. 76–81 °C. H NMR (300 MHz, CDCl3) δ 7.50 (1H, d J = 8.2 Hz, trans H5), 7.46 (1H, d J = 8.2 Hz, cis H5), 7.26 (2H, d, J = 8.7 Hz, trans H2',6'), 7.17 (2H, d, J = 8.7 Hz, cis H2',6'), 6.99 (2H, d, J = 8.8 Hz, cis H3',5'), 6.97 (2H, d, J = 8.9 Hz, trans H3',5'), 6.69 (1H, dd, J = 2.3, 8.1 Hz, cis H-6), 6.68 (1H, dd, J = 2.3, 8.2 Hz, trans H6), 6.67 (1H, d, J = 2.1 Hz, cis H8), 6.65 (1H, d, J = 2.2 Hz, trans H-8), 5.13 (1H, br d, J = 7.0 Hz, cis H4), 4.93 (1H, br d, J =10.0 Hz, trans H4), 4.18 (1H, dd, J = 2.0, 11.0 Hz, cis H-2), 3.96 (1H, dd, J = 2.1, 10.1 Hz, trans H-2), 3.54 (1H, dd, J = 2.4, 6.8 Hz, cis H3), 2.95 (1H, dd, J = 10.4, 10.4 Hz, trans H3), 2.32 (3H, s, trans
COCH3), 2.30 (3H, s, cis COCH3), 2.29 (3H, s, trans COCH3), 2.26 (3H, s, cis
COCH3), 1.69 (1H, d septet, J = 7.4, 12.3 Hz, trans CH(CH3)2), 1.58 (1H, d septet, J =
2.6, 7.0 Hz, cis CH(CH3)2), 1.07 (6H, d, J = 6.8 Hz, cis CH(CH3)2), 1.03 (6H, d, J = 13 7.0 Hz, trans CH(CH3)2). C NMR (75 MHz, CDCl3): 169.3 (CO), 162.4 (CO), 156.8 (ArC), 131.4 (ArC), 130.3 (ArC), 129.7 (ArC), 122.0 (ArC), 121.9 (ArC), 121.7 (ArC), 121.3 (ArC), 115.9 (ArC), 110.9 (ArC), 86.6 (C2), 58.5 (C4), 53.7 (C3), 29.4 (CH),
21.2 (COCH3), 19.3 (CH3), 18.4 (CH3). IR (KBr): νmax 3434 (s), 2965 (w), 2933 (w), 2873 (w), 1763 (s), 1686 (m), 1611 (s), 1560 (w), 1541 (w), 1507 (m), 1490 (w), 1472 (w), 1464 (w), 1443 (m), 1370 (m), 1201 (s), 1169 (m), 1144 (m), 1124 (m), 1112 (m), -1 1052 (w), 1013 (w), 994 (w), 912 (w), 851 (w), 762 (w) cm . UV-vis (MeOH): λmax 305 nm (ε 3,956 cm-1M-1), 251 (6,723). HRMS (+ESI): Found m/z 407.1465, [M+Na]+;
C22H24O6Na required 407.1465.
‐ 185 ‐ ‐ 186 ‐ 4-(7-Acetoxy-2-butyl-4-hydroxychroman-3-yl)phenyl acetate (251)
8 A suspension of isoflavone 245 (435 mg, 1.10 mmol) AcO O 2 and 5% palladium on charcoal (2.42 g) in ethyl acetate 3 2' 6 3' 5 (10 mL) was stirred under hydrogen (1 atm) for 6 days OH 6' OAc at room temperature. The reaction mixture was filtered 5' through a plug of Celite and evaporated in vacuo to give the title compound 251 (274 1 mg, 63%) as an orange solid. M.p. 48–50 °C. H NMR (300 MHz, CDCl3) δ 7.51 (1H, d, J = 8.7 Hz, trans H5), 7.49 (1H, d, J = 8.5 Hz, cis H5), 7.22 (2H, d, J = 8.6 Hz, trans H2',6'), 7.17 (2H, d, J = 8.7 Hz, cis H2',6'), 6.99 (2H, d, J = 8.7 Hz, cis H3',5'), 6.98 (2H, d, J = 8.8 Hz, trans H3',5'), 6.71 (1H, dd, J = 2.3, 8.4 Hz, cis H6), 6.69 (lH, dd, J = 2.3, 8.5 Hz, trans H6), 6.64 (1H, d, J = 2.3 Hz, cis H8), 6.63 (1H, d, J = 2.3 Hz, trans H8), 5.18 (1H, br dd, J = 8.1, 8.1 Hz, cis H4), 4.94 (1H, br d, J = 10.1 Hz, trans H4), 4.41 (1H, ddd, J = 2.3, 5.1, 7.4 Hz, cis H2), 4.26 (1H, ddd, J = 3.2, 7.7, 10.7 Hz, trans H2), 3.37 (1H, dd, J = 2.3, 7.0 Hz, cis H3), 2.85 (1H, dd, J = 10.3, 10.3 Hz, trans H3), 2.32
(3H, s, trans COCH3), 2.30 (3H, s, cis COCH3), 2.29 (3H, s, trans COCH3), 2.27 (3H, s, cis COCH3), 1.60–1.15 (12H, m, cis and trans CH2CH2CH2CH3), 0.87 (3H, t, J = 7.2 13 Hz, cis CH2CH2CH2CH3), 0.82 (3H, t, J = 7.3 Hz, trans CH2CH2CH2CH3). C NMR
(75 MHz, CDCl3): δ 169.6 (CO), 169.5 (CO), 154.9 (ArC), 151.5 (ArC), 150.5 (ArC), 135.0 (ArC), 128.0 (ArC), 127.7 (ArC), 121.6 (ArC), 115.2 (ArC), 111.4 (ArC), 109.8
(ArC), 85.6 (C2), 73.8 (C4), 60.7 (C3), 28.4 (CH2CH2CH2CH3), 22.7
(CH2CH2CH2CH3), 21.3 (COCH3), 20.9 (CH2CH2CH2CH3), 14.2 (CH2CH2CH2CH3).
IR (KBr): νmax 3448 (m), 2958 (m), 2932 (m), 2871 (w), 1763 (s), 1686 (w), 1677 (w), 1612 (s), 1592 (m), 1508 (s), 1459 (w), 1433 (m), 1370 (s), 1260 (s), 1203 (s), 1169 (s), -1 1144 (s), 1110 (s), 1016 (s), 912 (w), 848 (w), 804 (w) cm . UV-vis (MeOH): λmax 276 nm (ε 1,654 cm-1M-1), 206 (9,654). HRMS (+ESI): Found m/z 421.1608, [M+Na]+;
C23H26O6Na required 421.1622.
4-(7-Acetoxy-4-hydroxy-2-(trifluoromethyl)chroman-3-yl)phenyl acetate (252) A suspension of isoflavone 246 (463 mg, 1.13 mmol) 8 2 AcO O CF3 and 5% palladium on charcoal (2.59 g) in ethyl acetate 3 2' 6 3' (10 mL) was stirred under hydrogen (1 atm) for 6 days 5 OH 6' OAc at room temperature. The reaction mixture was filtered 5' through a plug of Celite and evaporated in vacuo to give the title compound 252 (335 1 mg, 72%) as a yellow solid. M.p. 74–78 °C. H NMR (300 MHz, CDCl3): δ 7.52 (1H, d,
‐ 187 ‐ J = 8.4 Hz, cis H5), 7.47 (1H, d, J = 8.4 Hz, trans H5), 7.17 (2H, d, J=8.6 Hz, cis H2′,6′), 7.14 (2H, d, J = 8.6 Hz, cis H2′,6′), 6.99 (2H, d, J = 8.7 Hz, cis H3′,5′), 6.98 (2H, d, J = 8.7 Hz, trans H3′,5′), 6.87 (1H, dd, J = 2.3 Hz, 8.4 Hz, trans H6), 6.82 (1H, dd, J = 2.3 Hz, 8.4 Hz, cis H6), 6.79 (1H, d, J=2.2 Hz, cis H8), 6.78 (1H, d, J = 2.3 Hz, trans H8), 5.24 (1H, br d, J = 7.1 Hz, cis H4), 4.99 (1H, br d, J = 10.4 Hz, trans H4), 4.83 (1H, dq, J = 2.5, 6.5 Hz, cis H2), 4.72 (1H, dq, J = 6.5, 11.5 Hz, trans H2), 3.72 (1H, dd, J = 2.5, 6.9 Hz, cis H3), 3.21 (1H, dd, J = 10.3, 10.3 Hz, trans H-3), 2.32 (3H, s, trans COCH3), 2.31 (3H, s, cis COCH3), 2.30 (3H, s, trans COCH3), 2.27 (3H, s, cis 13 COCH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 168.7 (CO), 153.0 (ArC), 151.4 (ArC), 150.7 (ArC), 131.6 (ArC), 129.7 (ArC), 129.5 (ArC), 128.6 (ArC), 122.4 (ArC or CF3), 121.9 (ArC or CF3), 116.4 (ArC or CF3), 109.4 (ArC), 66.7 (C2), 47.3 (C4),
42.5 (C3), 21.2 (CH3). IR (KBr): νmax 3444 (m), 2936 (w), 1764 (s), 1697 (w), 1617 (m), 1593 (w), 1552 (w), 1509 (m), 1498 (w), 1434 (m), 1372 (m), 1289 (m), 1207 (s), 1172 (s), 1152 (s), 1140 (s), 1046 (w), 1020 (m), 997 (w), 947 (w), 905 (w), 852 (w), 819 (w), -1 -1 -1 774 (w), 706 (w) cm . UV-vis (MeOH): λmax 273 nm (ε 3,024 cm M ), 215 (11,912). + HRMS (+ESI): Found m/z 433.0858, [M+Na] ; C20H17F3O6Na required 433.0869.
4-(7-Acetoxy-4-hydroxy-2-phenylchroman-3-yl)phenyl acetate (253) A suspension of isoflavone 247 (254 mg, 0.613 mmol) 3" and 5% palladium on charcoal (1.41 g) in ethyl acetate 2" 4" 8 2 (10 mL) was stirred under hydrogen (1 atm) for 24 AcO O 5" 6" 3 2' 6 hours at room temperature. The reaction mixture was 3' 5 OH filtered through a plug of Celite and evaporated in 6' OAc 5' vacuo to give the title compound 253 (166 mg, 65%) as a brown solid. M.p. 58–60 °C. 1 H NMR (300 MHz, CDCl3): δ 7.60 (1H, d, J = 8.4 Hz, H5), 7.26-7.10 (5H, m, ArH), 6.93 (2H, d, J = 8.7 Hz, H2',6'), 6.86 (2H, d, J = 8.8 Hz, H-3',5'), 6.81 (1H, dd, J = 2.2, 8.4 Hz, H6), 6.77 (1H, d, J = 2.1 Hz, H8), 5.59 (1H, br d, J = 2.1 Hz, H2), 5.45 (1H, br d, J = 7.1 Hz, H4), 3.65 (1H, dd, J = 2.1, 7.0 Hz, H3), 2.32 (3H, s, COCH3), 2.23 (3H, s, 13 COCH3). C NMR (75 MHz, CDCl3) δ 169.5 (CO), 169.0 (CO), 165.5 (ArC), 160.2 (ArC), 156.7 (ArC), 147.7 (ArC), 132.5 (ArC), 132.1 (ArC), 130.4 (ArC), 129.8 (ArC), 128.7 (ArC), 127.9 (ArC), 123.3 (ArC), 121.7 (ArC), 114.7 (ArC), 110.0 (ArC), 80.1
(C2), 77.4 (C4), 50.6 (C3), 21.3 (CH3). IR (KBr): νmax 3440 (m), 3063 (w), 2929 (w), 2856 (w), 1761 (s), 1740 (s), 1616 (s), 1559 (w), 1507 (m), 1497 (w), 1451 (w), 1437 (w), 1371 (m), 1315 (w), 1202 (s), 1167 (s), 1146 (s), 1116 (m), 1080 (w), 1055 (w),
‐ 188 ‐ -1 - 1017 (m), 912 (w), 845 (w), 705 (w) cm . UV-vis (MeOH): λmax 227 nm (ε 7,059 cm 1 -1 + M ). HRMS (+ESI): Found m/z 441.1297, [M+Na] ; C25H22O6Na required 441.1309.
4-(7-Acetoxy-4-hydroxy-2-(pyridin-4-yl)chroman-3-yl)phenyl acetate (254) A suspension of isoflavone 248 (611 mg, 1.47 mmol) 3" 2" N 8 and platinum(IV) oxide (1.77 g) in ethyl acetate (20 mL) 2 AcO O 5" 6" was stirred under hydrogen (1 atm) for 8 hours at room 3 2' 6 temperature. The reaction mixture was filtered through 5 3' OH 6' OAc a plug of Celite and evaporated in vacuo to give the 5' title compound 254 (267 mg, 43%) as a yellow solid. M.p. 153–156 °C (decomp.). 1H
NMR (300 MHz, CDCl3): δ 8.46 (2H, d, J = 6.0 Hz, H3",5"), 7.60 (1H, d, J = 8.4 Hz, H5), 7.11 (2H, d, J = 5.6 Hz, H2",6"), 6.92 (2H, d, J = 8.8 Hz, H2',6'), 6.85 (2H, d, J = 8.9 Hz, H-3',5'), 6.83 (1H, dd, J = 2.2, 8.5 Hz, H6), 6.79 (1H, d, J = 2.3 Hz, H8), 5.56 (1H, br d, J = 2.4 Hz, H-2), 5.45 (1H, br d, J = 7.1 Hz, H4), 3.67 (IH, dd, J = 2.5, 7.0 Hz, 13 H3), 2.32 (3H, s, COCH3), 2.23 (3H, s, COCH3). C NMR (75 MHz, CDCl3) δ 167.1 (CO), 165.3 (CO), 158.5 (ArC), 156.1 (ArC), 153.1 (ArC), 149.9 (ArC), 145.4 (ArC), 136.8 (ArC), 131.8 (ArC), 129.7 (ArC), 125.5 (ArC), 124.3 (ArC), 122.6 (ArC), 115.1
(ArC), 108.9 (ArC), 76.0 (C2), 56.4 (C4), 45.1 (C3), 21.4 (CH3). IR (KBr): νmax 3428 (s), 2961 (w), 2925 (w), 2849 (w), 1758 (w), 1657 (w), 1619 (s), 1612 (s), 1552 (w), 1513 (m), 1461 (m), 1452 (m), 1422 (w), 1370 (m), 1261 (s), 1203 (s), 1167 (s), 1117 -1 (m), 1067 (w), 1017 (w), 843 (w), 805 (w), 766 (w) cm . UV-vis (MeOH): λmax 278 nm (ε 1,611 cm-1M-1), 210 (5,823). HRMS (+ESI): Found m/z 442.1249, [M+Na]+;
C24H21NO6Na required 442.1261.
4-(7-Acetoxy-2-propyl-2H-chromen-3-yl)phenyl acetate (258)
8 A suspension of isoflavanol 249 (305 mg, 0.792 mmol) AcO O 2 and 85 wt. % phosphoric acid (0.75 mL, 11 mmol) in 3 2' 6 3' toluene (7.5 mL) was heated at reflux for 3 hours. The 5 4 6' OAc cooled reaction mixture was neutralised with saturated 5' sodium hydrogen carbonate solution (10 mL) and extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo. The residue was dissolved in 95% ethanol (5 mL) and poured into water (30 mL). The precipitate was collected and purified by semi-preparative HPLC to give the title compound 258 (48 mg, 16%) as an off-white 1 powder. M.p. 102–105 °C. H NMR (300 MHz, CDCl3): δ 7.46 (2H, d, J = 8.8 Hz,
‐ 189 ‐ H2',6'), 7.11 (2H, d, J = 8.8 Hz, H3',5'), 7.06 (1H, d, J = 8.0 Hz, H5), 6.68 (1H, br s, H4), 6.65 (1H, dd, J = 2.3, 8.0 Hz, H6), 6.63 (1H, d, J = 2.2 Hz, H8), 5.29 (1H, dd, J = 2.5,
9.9 Hz, H2), 2.32 (3H, s, COCH3), 2.29 (3H, s, COCH3), 1.90–1.79 (1H, m, a b CH CH2CH3), 1.50–1.38 (3H, m, CH CH2CH3), 0.89 (3H, t, J = 7.2 Hz, CH2CH2CH3). 13 C NMR (75 MHz, CDCl3): δ 165.0 (CO), 163.5 (CO), 157.6 (ArC), 153.8 (ArC), 149.3 (ArC), 138.0 (ArC), 130.0 (ArC), 128.5 (ArC), 126.6 (ArC), 122.2 (ArC), 120.8
(ArC), 116.0 (ArC), 114.8 (ArC), 107.1 (ArC), 76.6 (C2), 38.0 (CH2CH2CH3), 31.2
(CH2CH2CH3), 21.4 (COCH3), 16.3 (CH2CH2CH3). IR (KBr): νmax 3437 (m), 2961 (w), 2927 (w), 2871 (w), 1754 (w), 1743 (w), 1727 (w), 1710 (w), 1691 (w), 1657 (m), 1620 (s), 1612 (s), 1513 (m), 1502 (w), 1461 (m), 1452 (m), 1370 (w), 1263 (m), 1230 (s), 1203 (s), 1166 (s), 1136 (m), 1110 (m), 1018 (w), 836 (w), 801 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 326 nm (ε 4,763 cm M ), 275 (5,679), 203 (25,282). HRMS (+ESI): + Found m/z 389.1364, [M+Na] ; C22H22O5Na required 389.1365.
4-(7-Acetoxy-2-isopropyl-2H-chromen-3-yl)phenyl acetate (259)
A suspension of isoflavanol 250 (300 mg, 0.779 mmol) 8 AcO O 2 and 85 wt. % phosphoric acid (0.75 mL, 11 mmol) in 3 2' 6 3' toluene (7.5 mL) was heated at reflux for 3 hours. The 5 4 6' OAc cooled reaction mixture was neutralised with saturated 5' sodium hydrogen carbonate solution (10 mL) and extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo. The residue was dissolved in 95% ethanol (5 mL) and poured into water (30 mL). The precipitate was collected and purified by semi-preparative HPLC to give the title compound 259 (49 mg, 17%) as an off-white 1 powder. M.p. 118–122 °C. H NMR (300 MHz, CDCl3): δ 7.45 (2H, d, J = 8.8 Hz, H2',6'), 7.10 (2H, d, J = 8.8 Hz, H3',5'), 7.08 (1H, d, J = 8.0 Hz, H5), 6.67 (1H, dd, J = 2.3, 8.0 Hz, H6), 6.62 (1H, br s, H4), 6.59 (1H, d, J = 2.1 Hz, H8), 5.15 (1H, d, J = 5.6
Hz, H2), 2.32 (3H, s, COCH3), 2.29 (3H, s, COCH3), 1.95 (1H, d septet, J = 5.6, 7.1 Hz, a b CH(CH3)2), 0.88 (3H, d, J = 6.8 Hz, CH(CH3) ), 0.85 (3H, d, J = 6.9 Hz, CH(CH3) ). 13 C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.3 (CO), 154.0 (ArC), 151.2 (ArC), 150.2 (ArC), 136.5 (ArC), 134.3 (ArC), 128.2 (ArC), 127.0 (ArC), 126.6 (ArC), 121.9
(ArC), 120.5 (ArC), 114.0 (ArC), 109.1 (ArC), 81.6 (C2), 33.1 (CH), 21.2 (COCH3),
19.3 (CH3), 17.4 (CH3). IR (KBr): νmax 3448 (m), 2964 (w), 2927 (w), 1763 (m), 1736 (w), 1701 (w), 1686 (w), 1648 (w), 1655 (m), 1618 (s), 1561 (m), 1545 (w), 1535 (w), 1509 (m), 1459 (m), 1439 (m), 1400 (w), 1370 (m), 1261 (s), 1201 (s), 1170 (s), 1139
‐ 190 ‐ -1 (m), 1111 (s), 1019 (m), 897 (w), 841 (w), 806 (m) cm . UV-vis (MeOH): λmax 327 nm (ε 8,550 cm-1M-1), 286 (7,634), 203 (10,046). HRMS (+ESI): Found m/z 389.1365, + [M+Na] ; C22H22O5Na required 389.1365.
4-(7-Acetoxy-2-butyl-2H-chromen-3-yl)phenyl acetate (260)
8 A suspension of isoflavanol 251 (244 mg, 0.610 mmol) AcO O 2 and 85 wt.% phosphoric acid (0.75 mL, 11 mmol) in 3 2' 6 3' toluene (7.5 mL) was heated at reflux for 3 hours. The 5 4 6' OAc cooled reaction mixture was neutralised with saturated 5' sodium hydrogen carbonate solution (10 mL) and extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo. The residue was dissolved in 95% ethanol (5 mL) and poured into water (30 mL). The precipitate was collected to give the title compound 260 (138 mg, 59%) as an off-white powder. M.p. 75–78 °C. 1H NMR (300
MHz, CDCl3): δ 7.46 (2H, d, J = 8.9 Hz, H2',6'), 7.11 (2H, d, J = 8.9 Hz, H3',5'), 7.06 (1H, d, J = 7.9 Hz, H5), 6.68 (1H, br s, H4), 6.66 (1H, dd, J = 2.3, 7.9 Hz, H6), 6.64
(1H, d, J = 2.3 Hz, H8), 5.27 (1H, dd, J = 2.5, 9.9 Hz, H2), 2.32 (3H, s, COCH3), 2.29 a (3H, s, COCH3), 1.91–1.79 (1H, m, CH CH2CH2CH3), 1.52–1.50 (5H,m, b 13 CH CH2CH2CH3), 0.85 (3H, t, J = 7.3 Hz, CH2CH2CH2CH3). C NMR (75 MHz,
CDCl3): δ 169.5 (CO), 169.4 (CO), 152.9 (ArC), 151.2 (ArC), 150.3 (ArC), 135.1 (ArC), 134.9 (ArC), 127.1 (ArC), 126.7 (ArC), 126.4 (ArC), 121.9 (ArC), 120.8 (ArC),
118.8 (ArC), 114.4 (ArC), 110.1 (ArC), 77.6 (C2), 32.9 (CH2CH2CH2CH3), 27.8
(CH2CH2CH2CH3), 22.3 (CH2CH2CH2CH3), 21.2 (COCH3), 14.0 (CH2CH2CH2CH3).
IR (KBr): νmax 3429 (m), 2956 (w), 2931 (w), 2860 (w), 1759 (s), 1685 (w), 1655 (w), 1611 (s), 1509 (s), 1496 (m), 1459 (m), 1425 (w), 1370 (m), 1201 (s), 1169 (s), 1140 (s), -1 1110 (s), 1046 (w), 1016 (m), 973 (w), 910 (w), 846 (w) cm . UV-vis (MeOH): λmax 327 nm (ε 7,037 cm-1M-1), 203 (19,497). HRMS (+ESI): Found m/z 403.1520, [M+Na]+;
C23H24O5Na required 403.1521.
4-(7-Acetoxy-2-(trifluoromethyl)-2H-chromen-3-yl)phenyl acetate (261)
8 A suspension of isoflavanol 252 (200 mg, 0.487 mmol) 2 AcO O CF3 and 85 wt. % phosphoric acid (0.50 mL, 7.2 mmol) in 3 2' 6 3' toluene (5 mL) was heated at reflux for 4.5 hours. The 5 4 6' OAc cooled reaction mixture was poured into water (5 mL) 5' and extracted with ethyl acetate (3 × 5 mL). The solvent was evaporated in vacuo to
‐ 191 ‐ give the title compound 261 (164 mg, 85%) as a yellow solid. M.p. 138–142 °C. 1H
NMR (300 MHz, CDCl3): δ 7.48 (2H, d, J = 8.8 Hz, H2',6'), 7.15 (2H, d, J = 8.8 Hz, H3',5'), 7.14 (1H, d, J = 8.0 Hz, H5), 6.93 (1H, br s, H4), 6.76 (1H, d, J = 2.3 Hz, H8), 6.75 (1H, dd, J = 2.5, 7.0 Hz, H6), 5.68 (1H, quartet, J = 6.7 Hz, H2), 2.32 (3H, s, 13 COCH3), 2.29 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.1 (CO), 152.1 (ArC), 151.8 (ArC), 150.7 (ArC), 134.6 (ArC), 134.2 (ArC), 127.9 (ArC), 126.8
(ArC), 123.0 (ArC), 122.0 (ArC), 118.8 (ArC), 115.8 (ArC or CF3), 115.6 (ArC or CF3),
109.4 (ArC), 103.0 (C2), 21.2 (CH3). IR (KBr): νmax 3448 (m), 2960 (w), 2926 (w), 2874 (w), 2860 (w), 1753 (m), 1619 (s), 1511 (m), 1493 (w), 1460 (m), 1377 (m), 1262 (m), 1206 (s), 1174 (s), 1137 (s), 1117 (s), 1068 (w), 1015 (w), 906 (w), 851 (w), 725 -1 -1 -1 (w) cm . UV-vis (MeOH): λmax 326 nm (ε 7,258 cm M ), 235 (5,512), 205 (9,926). + HRMS (+ESI): Found m/z 415.0768 [M+Na] ; C20H15F3O5Na required 415.0769.
4-(7-Acetoxy-2-phenyl-2H-chromen-3-yl)phenyl acetate (262)
A suspension of isoflavanol 253 (160 mg, 0.383 mmol) 3" 2" 4" and 85 wt. % phosphoric acid (0.50 mL, 7.2 mmol) in 8 2 AcO O 5" toluene (5 mL) was heated at reflux for 2 hours. The 6" 3 2' 5 3' cooled reaction mixture was neutralised with saturated 5 4 6' OAc sodium hydrogen carbonate solution (5 mL) and 5' extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo to give the title compound 262 (148 mg, 97%) as an orange solid. M.p. 78–81 °C. 1H NMR
(300 MHz, CDCl3): δ 7.39 (2H, d, J = 8.8 Hz, H2',6'), 7.19–7.15 (5H, m, ArH), 7.13 (1H, d, J = 8.4 Hz, H5), 7.06 (1H, br s, H4), 7.04 (2H, d, J = 8.8 Hz, H3',5'), 6.64 (1H, dd, J = 2.2, 8.2 Hz, H6), 6.53 (1H, d, J = 2.3 Hz, H8), 6.24 (1H, s, H2), 2.29 (3H, s, 13 COCH3), 2.23 (3H, s, COCH3). C NMR (75 MHz, CDCl3): δ 169.4 (CO), 169.2 (CO), 152.2 (ArC), 151.4 (ArC), 150.3 (ArC), 138.0 (ArC), 134.8 (ArC), 130.2 (ArC), 129.1 (ArC), 128.9 (ArC), 128.7 (ArC), 128.3 (ArC), 126.5 (ArC), 125.3 (ArC), 121.8 (ArC),
120.6 (ArC), 114.6 (ArC), 110.1 (ArC), 77.9 (C2), 21.1 (CH3). IR (KBr): νmax 3426 (m), 2927 (w), 2854 (w), 1738 (s), 1613 (s), 1509 (m), 1495 (w), 1452 (w), 1370 (m), 1263 (s), 1202 (s), 1169 (s), 1143 (m), 1113 (m), 1061 (w), 1024 (w), 980 (w), 912 (w), 848 -1 -1 -1 (w), 807 (w), 757 (w), 701 (w) cm . UV-vis (MeOH): λmax 328 nm (ε 4,604 cm M ), + 201 (27,429). HRMS (+ESI): Found m/z 423.1209, [M+Na] ; C25H20O5Na required 423.1208.
‐ 192 ‐ 3-(4-Hydroxyphenyl)-2-propyl-2H-chromen-7-ol (263)
8 The isoflavene 258 (48 mg, 0.13 mmol) was dissolved in HO O 2 methanol (5 mL). Aqueous KOH (1 M, 0.5 mL) was 3 2' 6 3' added. The mixture was stirred for 10 minutes at room 5 4 6' OH temperature and then neutralised with 1 M acetic acid. 5' Water (20 mL) was added and the resulting mixture was extracted with ethyl acetate (3 × 5 mL). The solvent was evaporated in vacuo to give the title compound 263 (27 mg, 1 74%) as a tan solid. M.p. 99–101 °C. H NMR (300 MHz, d6-DMSO): δ 9.56 (1H, br s, OH), 9.52 (1H, br s, OH), 7.36 (2H, d, J = 8.8 Hz, H2',6'), 6.93 (1H, d, J = 8.2 Hz, H5), 6.77 (1H, d J = 8.8 Hz, H3',5'), 6.70 (1H, br s, H4), 6.31 (1H, dd, J = 2.3, 8.1 Hz, H6), 6.24 (1H, d, J = 2.2 Hz, H8), 5.26 (1H, dd, J = 2.9, 9.8 Hz, H2), 1.51–1.27 (4H, m, 13 CH2CH2CH3), 0.85 (3H, t, J = 7.3 Hz, CH2CH2CH3). C NMR (75 MHz, d6-DMSO): δ 157.5 (ArC), 155.7 (ArC), 151.7 (ArC), 130.6 (ArC), 127.8 (ArC), 125.4 (ArC), 123.1 (ArC), 120.5 (ArC), 115.3 (ArC), 112.9 (ArC), 108.9 (ArC), 103.2 (ArC), 79.5 (C2),
36.1 (CH2CH2CH3), 26.0 (CH2CH2CH3), 15.9 (CH2CH2CH3). IR (KBr): νmax 3422 (s), 2960 (m), 2928 (m), 2871 (w), 1686 (w), 1664 (w), 1654 (w), 1637 (m), 1624 (s), 1618 (s), 1612 (s), 1571 (w), 1509 (m), 1500 (w), 1474 (w), 1466 (m), 1459 (m), 1369 (w), 1266 (m), 1216 (s), 1160 (s), 1123 (s), 1018 (w), 912 (w), 833 (w) cm-1. UV-vis -1 -1 (MeOH): λmax 328 nm (ε 5,647 cm M ), 270 (7,058), 205 (25,974). HRMS (+ESI): + Found m/z 283.1324, [M+H] ; C18H19O3 required 283.1329.
3-(4-Hydroxyphenyl)-2-isopropyl-2H-chromen-7-ol (264)157
The isoflavene 259 (49 mg, 0.13 mmol) was dissolved in 8 HO O 2 methanol (5 mL). Aqueous KOH (1 M, 0.5 mL) was 3 2' 6 3' added. The mixture was stirred for 10 minutes at room 5 4 6' OH temperature and then neutralised with 1 M acetic acid. 5' Water (20 mL) was added and the resulting mixture was extracted with ethyl acetate (3 × 5 mL). The solvent was evaporated in vacuo to give the title compound 264 (31 mg, 1 84%) as a light brown solid. M.p. 201–204 °C. H NMR (300 MHz, d6-DMSO): δ 9.52 (1H, br s, OH), 9.47 (1H, br s, OH), 7.37 (2H, d, J = 8.8 Hz, H2',6'), 6.90 (1H, d, J = 8.1 Hz, H5), 6.75 (1H, d J = 8.8 Hz, H3',5'), 6.665 (1H, br s, H4), 6.27 (1H, dd, J = 2.4, 8,1 Hz, H6), 6.22 (1H, d, J = 2.4Hz, H8), 5.15 (1H, d, J = 5.9 Hz, H2), 1.90–1.72 (1H, m, a b CH(CH3)2), 0.84 (3H, d, J = 6.8 Hz, CH(CH3) ), 0.79 (3H, d, J = 6.9 Hz, CH(CH3) ).
‐ 193 ‐ 2-Butyl-3-(4-hydroxyphenyl)-2H-chromen-7-ol (265)
8 The isoflavene 260 (138 mg, 0.363 mmol) was dissolved HO O 2 in methanol (5 mL). Aqueous KOH (1 M, 0.5 mL) was 3 2' 6 3' added. The mixture was stirred for 10 minutes at room 5 4 6' OH temperature and then neutralised with 1 M acetic acid. 5' Water (20 mL) was added and the resulting mixture was extracted with ethyl acetate (3 × 5 mL). The solvent was evaporated in vacuo to give the title compound 265 (77 mg, 1 72%) as a brown solid. M.p. 87–92 °C. H NMR (300 MHz, d6-DMSO): δ 9.56 (1H, br s, OH), 9.51 (1H, br s, OH), 7.35 (2H, d, J = 8.7 Hz, H2',6'), 6.93 (1H, d, J = 8.2 Hz, H5), 6.78 (2H, d, J = 8.7 Hz, H3',5'), 6.69 (1H, br s, H4), 6.32 (1H, dd, J = 2.2, 8.1 Hz, H6), 6.25 (1H, d, J = 2.1 Hz, H8), 5.25 (1H, dd, J = 2.5, 9.5 Hz, H2), 1.77–1.57 (1H, m, a b CH CH2CH2CH3), 1.52–1.25 (5H, m, CH CH2CH2CH3), 0.81 (3H, t, J = 7.3 Hz, 13 CH2CH2CH2CH3). C NMR (75 MHz, CDCl3): δ 158.7 (ArC), 157.7 (ArC), 152.5 (ArC), 132.2 (ArC), 129.5 (ArC), 127.8 (ArC), 126.4 (ArC), 116.4 (ArC), 116.1 (ArC),
115.4 (ArC), 108.8 (ArC), 103.6 (ArC), 75.7 (C2), 32.7 (CH2CH2CH2CH3), 27.7
(CH2CH2CH2CH3), 22.3 (CH2CH2CH2CH3), 14.4 (CH2CH2CH2CH3). IR (KBr): νmax 3339 (s), 3028 (w), 2953 (m), 2925 (m), 2853 (m), 1612 (s), 1514 (s), 1459 (s), 1376 (m), 1339 (w), 1286 (m), 1245 (s), 1179 (m), 1156 (s), 1111 (m), 1047 (w), 1019 (w), -1 -1 -1 831 (m) cm . UV-vis (MeOH): λmax 328 nm (ε 13,356 cm M ), 308 (12,042), 217 + (22,622). HRMS (+ESI): Found m/z 297.1480, [M+H] ; C19H21O3 required 297.1485.
3-(4-Hydroxyphenyl)-2-(trifluoromethyl)-2H-chromen-7-ol (266)
8 The isoflavene 261 (146 mg, 0.372 mmol) was dissolved 2 HO O CF3 in methanol (10 mL). Aqueous KOH (1 M, 1 mL) was 3 2' 6 3' added. The mixture was stirred for 15 minutes at room 5 4 6' OH temperature and then neutralised with 1 M acetic acid 5' and poured into water (30 mL). The precipitate was collected to give the title compound 1 266 (63 mg, 54%) as a yellow solid. M.p. 157–161 °C. H NMR (300 MHz, d6-DMSO): δ 9.80 (1H, br s, OH), 9.63 (1H, br s, OH), 7.48 (2H, d, J = 8.8 Hz, H2',6'), 7.05 (1H, d, J = 8.3 Hz, H5), 7.03 (1H, br s, H4), 6.77 (2H, d, J = 8.9 Hz, H3',5'), 6.40 (1H, dd, J = 2.3, 8.2 Hz, H6), 6.35 (1H, d, J = 2.2 Hz, H8), 6.25 (1H, q, J = 7.4 Hz, H2). 13C NMR
(75 MHz, CDCl3): δ 159.3 (ArC), 157.8 (ArC), 152.5 (ArC), 128.7 (ArC), 127.5 (ArC),
127.1 (ArC), 122.5 (ArC), 122.1 (ArC), 116.0 (ArC or CF3), 113.7 (ArC or CF3), 109.9
(ArC), 102.6 (C2). IR (KBr): νmax 3349 (s), 3031 (w), 2959 (w), 2919 (m), 2850 (w),
‐ 194 ‐ -1 -1 -1 max 328 nm (ε 18,115 cm M ), 209 (20,591). HRMS + (+ESI): Found m/z 309.0727, [M+H] ; C16H12F3O3 required 309.0733.
3-(4-Hydroxyphenyl)-2-phenyl-2H-chromen-7-ol (267)157 The isoflavene 262 (148 mg, 0.351 mmol) was dissolved 3" 2" 4" 8 in methanol (5 mL). Aqueous KOH (1 M, 0.8 mL) was 2 HO O 5" 6" added. The mixture was stirred for 20 minutes at room 3 2' 6 3' temperature and then neutralised with 1 M acetic acid. 5 4 6' OH Water (20 mL) was added and the resulting mixture was 5' extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo to give the title compound 267 (83 mg, 75%) as a brown solid. M.p. 128–133 °C. 1H NMR (300
MHz, d6-DMSO): δ 7.43–7.22 (5H, m, ArH), 7.32 (2H, d, J = 8.9 Hz, H2',6'), 7.05 (1H, br s, H4), 6.99 (1H, d, J = 8.3 Hz, H5), 6.71 (2H, d, J = 8.8 Hz, H3',5'), 6.33 (1H, br s, H2), 6.29 (1H, dd, J = 2.3, 8.2 Hz, H6), 6.12 (1H, d, J = 2.4 Hz, H8).
4-(7-acetoxy-2-(pyridin-4-yl)-2H-chromen-3-yl)phenyl acetate (268) A suspension of isoflavanol 254 (101 mg, 0.241 mmol) 3" 2" N 8 and phosphorous pentoxide (880 mg, 6.20 mmol) in 2 AcO O 5" 6" dichloromethane (5 mL) was stirred for 20 hours at 3 2' 6 3' room temperature. Methanol (20 mL), water (100 mL) 5 4 6' OAc and saturated sodium hydrogen carbonate solution (20 5' mL) were added to the reaction mixture, which was subsequently extracted with ethyl acetate (3 × 20 mL). The solvent was evaporated in vacuo to give the title compound 1 268 (81 mg, 84%) as a yellow solid. M.p. 104–108 °C. H NMR (300 MHz, d6-DMSO): δ 8.51 (2H, d, J = 6.1 Hz, H3",5"), 7.65 (2H, d, J = 8.8 Hz, H2',6'), 7.41 (1H, br s, H4), 7.34 (2H, d, J = 6.2 Hz, H2",6"), 7.30 (1H, d, J = 8.3 Hz, H5), 7.16 (2H, d, J = 8.8 Hz, H3',5'), 6.71 (1H, dd, J = 2.2, 8.1 Hz, H6), 6.67 (1H, d, J = 2.3 Hz, H8), 6.66 (1H, br s, 13 H2), 2.26 (3H, s, COCH3), 2.21 (3H, s, COCH3). C NMR (75 MHz, d6-DMSO): δ 167.4 (CO), 167.2 (CO), 158.8 (ArC), 154.6 (ArC), 152.8 (ArC), 151.3 (ArC), 144.8 (ArC), 142.7 (ArC), 136.2 (ArC), 129.4 (ArC), 126.7 (ArC), 123.1 (ArC), 120.5 (ArC),
116.9 (ArC), 114.5 (ArC), 113.1 (ArC), 108.9 (ArC), 81.0 (C2), 21.1 (CH3). IR (KBr):
νmax 3430 (m), 2931 (m), 2855 (w), 1735 (w), 1706 (s), 1678 (w), 1655 (w), 1619 (s),
‐ 195 ‐ 1554 (w), 1509 (m), 1451 (m), 1370 (w), 1261 (s), 1203 (s), 1164 (m), 1097 (s), 1019 -1 -1 -1 (s), 916 (w), 895 (w), 802 (m) cm . UV-vis (MeOH): λmax 344 nm (ε 1,807 cm M ), + 270 (4,315), 202 (28,299). HRMS (+ESI): Found m/z 402.1340, [M+H] ; C24H20NO3 required 402.1341.
3-(4-Hydroxyphenyl)-2-(pyridin-4-yl)-2H-chromen-7-ol (269) The isoflavene 268 (81 mg, 0.20 mmol) was dissolved in 3" 2" N 8 methanol (3 mL). Aqueous KOH (1 M, 0.2 mL) was 2 HO O 5" 6" added. The mixture was stirred for 15 minutes at room 3 2' 6 3' temperature and then neutralised with 1 M acetic acid. 5 4 6' OH Water (10 mL) was added. The precipitate was collected 5' to give the title compound 269 (23 mg, 36%) as a pale yellow solid. M.p. 163–166 °C 1 (decomp.). H NMR (300 MHz, d6-DMSO): δ 9.6l (1H, br s, OH), 9.52 (1H, br s, OH), 8.47 (2H, d, J = 6.1 Hz, H3",5"), 7.38 (2H, d, J = 8.9 Hz, H2',6'), 7.26 (2H, d, J = 6.1 Hz, H2",6"), 7.07 (1H, br s, H4), 7.01 (1H, d, J = 8.3 Hz, H5), 6.74 (2H, d, J = 8.8 Hz, H-3',5'), 6.42 (1H, br s, H2), 6.32 (1H, dd, J = 2.3, 8.2 Hz, H6), 6.22 (1H, d, J = 2.3 Hz, 13 H8). C NMR (75 MHz, d6-DMSO): δ 159.6 (ArC), 157.3 (ArC), 154.3 (ArC), 141.2 (ArC), 139.8 (ArC), 138.6 (ArC), 129.7 (ArC), 128.2 (ArC), 127.5 (ArC), 124.1 (ArC), 122.3 (ArC), 118.7 (ArC), 116.0 (ArC), 114.5 (ArC), 108.3 (ArC), 78.6 (C2). IR (KBr):
νmax 3435 (s), 2960 (w), 2926 (m), 2855 (w), 1640 (m), 1621 (s), 1614 (s), 1537 (w), 1514 (m), 1504 (m), 1485 (w), 1462 (m), 1454 (m), 14515 (w), 1371 (w), 1261 (s), 1239 (m), 1161 (s), 1118 (s), 1095 (m), 1018 (w), 841 (w), 759 (w), 808 (w) cm-1. UV- -1 -1 vis (MeOH): λmax 348 nm (ε 1,634 cm M ), 267 (3,142), 202 (13,646). HRMS (+ESI): + Found m/z 318.1119, [M+H] ; C20H16NO3 required 318.1125.
7-Hydroxy-3-(4-hydroxyphenyl)-2-methylchroman-4-one (270)
8 A suspension of the isoflavone 228 (520 mg, 1.94 mmol) HO O 2 and 10% Pd/Al2O3 (1.42 g) in ethanol (27 mL) and 1 M 3 2' 6 3' 5 aqueous KOH (3 mL) was stirred under hydrogen (1 atm) O 6' OH for 8 days. The reaction mixture was filtered through a 5' plug of Celite. The filtrate was neutralised with 1 M HCl and poured into water (100 mL). The resulting mixture was extracted with ethyl acetate (3 × 30 mL). The combined extracts were dried over MgSO4 and the solvent was evaporated in vacuo. The crude product was purified by semi-preparative HPLC to give the title compound 270 (178 mg,
‐ 196 ‐ 138 1 34%) as an off-white powder. M.p. 263-265 °C, Lit 266 °C. H NMR (300 MHz, d6- DMSO): δ 10.60 (1H, br s, OH), 9.31 (1H, br s, OH), 7.84 (1H, d, J = 8.4 Hz, H5), 7.04 (2H, d, J = 8.7 Hz, H2′,6′), 6.77 (2H, d, J = 8.7 Hz, H3′,5′), 6.52 (1H, dd, J = 2.2 Hz, 8.4 Hz, H6), 6.36 (1H, d, J = 2.2 Hz, H8), 4.72 (1H, dq, J = 5.3 Hz, 10.1 Hz, H2), 3.70 (1H, d, J = 10.1 Hz, H3), 1.19 (3H, s, CH3).
2-Ethyl-7-hydroxy-3-(4-hydroxyphenyl)chroman-4-one (271)
8 A suspension of the isoflavone 229 (507 mg, 1.80 mmol) HO O 2 and 10% Pd/Al2O3 (1.48 g) in ethanol (27 mL) and 1 M 3 2' 6 3' aqueous KOH (3 mL) was stirred under hydrogen (1 atm) 5 O 6' OH for 14 days. The reaction mixture was filtered through a 5' plug of Celite. The filtrate was neutralised with 1 M HCl and poured into water (100 mL). The resulting precipitate was collected to give the title compound 271 (228 mg, 1 45%) as an off-white powder. M.p. 166–169 °C. H NMR (300 MHz, d6-DMSO): δ 10.67 (1H, br s, OH), 9.36 (1H, br s, OH), 7.63 (1H, d, J = 8.4 Hz, H5), 6.91 (2H, d, J = 8.7 Hz, H2′,6′), 6.66 (2H, d, J = 8.7 Hz, H3′,5′), 6.51 (1H, dd, J = 2.2 Hz, 8.4 Hz, H6), 6.39 (1H, d, J = 2.2 Hz, H8), 4.56 (1H, dt, J = 5.2 Hz, 10.2 Hz, H2), 3.74 (1H, d, J =
10.2 Hz, H3), 1.48 (2H, dq, J = 5.2 Hz, 7.2 Hz, CH2CH3), 0.92 (3H, t, J = 7.2 Hz, 13 CH2CH3). C NMR (75 MHz, d6-DMSO): δ 190.3 (CO), 165.3 (ArC), 163.6 (ArC), 157.1 (ArC), 130.5 (ArC), 129.8 (ArC), 126.4 (ArC), 125.4 (ArC), 115.9 (ArC), 115.2
(ArC), 102.9 (ArC), 56.6 (C2), 49.1 (C3), 19.1 (CH2CH3), 10.0 (CH2CH3). IR (KBr):
νmax 3388 (m), 3242 (s), 2965 (w), 2938 (w), 2875 (w), 1657 (w), 1621 (s), 1611 (s), 1598 (s), 1587 (s), 1556 (w), 1514 (s), 1460 (s), 1408 (w), 1365 (w), 1313 (w), 1280 (m), 1252 (s), 1219 (s), 1172 (m), 1161 (s), 1124 (m), 1059 (w), 1020 (w), 1010 (w), -1 - 952 (w), 846 (w), 831 (w), 786 (w) cm . UV-vis (MeOH): λmax 278 nm (ε 11,756 cm 1M-1), 212 (18,992), 202 (18,878). HRMS (+ESI): Found m/z 307.0934, [M+Na]+;
CHO17 16 4Na required 307.0941.
‐ 197 ‐ 7-Hydroxy-3-(4-hydroxyphenyl)-2-propylchroman-4-one (272)
8 A suspension of the isoflavone 230 (504 mg, 1.70 mmol) HO O 2 and 10% Pd/Al2O3 (1.44 g) in ethanol (27 mL) and 1 M 3 2' 6 3' aqueous KOH (3 mL) was stirred under hydrogen (1 atm) 5 O 6' OH for 8 days. The reaction mixture was filtered through a 5' plug of Celite. The filtrate was neutralised with 1 M HCl and poured into water (100 mL). The resulting precipitate was collected to give the title compound 272 (410 mg, 1 81%) as an off-white powder. M.p. 125–132 °C. H NMR (300 MHz, d6-DMSO): δ 10.64 (1H, br s, OH), 9.38 (1H, br s, OH), 7.61 (1H, d, J = 8.3 Hz, H5), 6.90 (2H, d, J = 8.7 Hz, H2′,6′), 6.66 (2H, d, J = 8.7 Hz, H3′,5′), 6.51 (1H, dd, J = 2.2 Hz, 8.3 Hz, H6), 6.38 (1H, d, J = 2.2 Hz, H8), 4.60 (1H, m, H2), 3.70 (1H, d, J = 10.1 Hz, H3), 1.60– 13 1.12 (4H, m, CH2CH2CH3), 0.89 (3H, t, J = 7.2 Hz, CH2CH3). C NMR (75 MHz, d6- DMSO): δ 190.9 (CO), 164.8 (ArC), 163.1 (ArC), 156.6 (ArC), 131.5 (ArC), 130.0 (ArC), 125.0 (ArC), 115.4 (ArC), 114.9 (ArC), 111.0 (ArC), 101.9 (ArC), 56.0 (C2),
48.5 (C3), 33.4 (CH2CH2CH3), 18.9 (CH2CH2CH3), 13.8 (CH2CH2CH3). IR (KBr):
νmax 3411 (s), 2959 (m), 2931 (m), 2871 (w), 1654 (m), 1647 (w), 1612 (s), 1514 (s), 1464 (m), 1362 (w), 1362 (w), 1242 (s), 1162 (m), 1124 (m), 830 (w), 813 (w) cm-1. -1 -1 UV-vis (MeOH): λmax 279 nm (ε 6,304 cm M ), 204 (14,628). HRMS (+ESI): Found + m/z 321.1092, [M+Na] ; C18H18O4Na required 321.1097.
7-Hydroxy-3-(4-hydroxyphenyl)-8-methyl-2-propylchroman-4-one (273) A suspension of the isoflavone 238 (527 mg, 1.70 mmol) HO O 2 and 10% Pd/Al2O3 (1.64 g) in ethanol (27 mL) and 1 M 3 2' 6 3' aqueous KOH (3 mL) was stirred under hydrogen (1 atm) 5 O 6' OH for 10 days. The reaction mixture was filtered through a 5' plug of Celite. The filtrate was neutralised with 1 M HCl and poured into water (100 mL). The resulting precipitate was collected and purified by semi-preparative HPLC to give the title compound 273 (248 mg, 60%) as an off-white powder. M.p. 257–259 °C 1 (decomp.). H NMR (300 MHz, d6-DMSO): δ 10.64 (1H, br s, OH), 9.34 (1H, br s, OH), 7.48 (1H, d, J = 8.4 Hz, H5), 6.90 (2H, d, J = 8.7 Hz, H2′,6′), 6.66 (2H, d, J = 8.7 Hz, H3′,5′), 6.52 (1H, d, J = 8.4 Hz, H6), 4.58 (1H, m, H2), 3.70 (1H, d, J = 10.1 Hz, H3),
2.24 (3H, s, CH3), 1.82–1.21 (4H, m, CH2CH2CH3), 0.85 (3H, t, J = 7.2 Hz, CH2CH3). 13 C NMR (75 MHz, d6-DMSO): δ 191.7 (C4O), 162.0 (ArC), 160.0 (ArC), 156.3 (ArC), 130.2 (ArC), 126.9 (ArC), 125.3 (ArC), 115.2 (ArC), 113.4 (ArC), 111.0 (ArC), 109.3
‐ 198 ‐ (ArC), 81.1 (ArC), 55.9 (C2), 40.3 (C3), 35.0 (CH2CH2CH3), 17.9 (CH2CH2CH3),
13.7 (CH3), 7.9 (CH2CH2CH3). IR (KBr): νmax 3342 (s), 3022 (w), 2958 (w), 2930 (w), 2872 (w), 1655 (s), 1610 (s), 1593 (s), 1555 (w), 1517 (m), 1447 (m), 1354 (m), 1299 (w), 1251 (m), 1222 (s), 1179 (w), 1123 (w), 1110 (w), 1090 (m), 1018 (w), 965 (w), -1 -1 -1 842 (w), 808 (w) cm . UV-vis (MeOH): λmax 284 nm (ε 5,636 cm M ), 221 (9,854). + HRMS (+ESI): Found m/z 335.1258, [M+Na] ; C19H20O4Na required 335.1259.
4-(5-Acetoxy-2,7b-dihydro-1aH-oxireno[2,3-c]chromen-1a-yl)phenyl acetate (290) To a solution of diacetoxyphenoxodiol 111 (0.50 g, 1.5 4 AcO O 2 mmol) in dichloromethane (10 mL) was added a 1a 2' 6 3' solution of m-chloroperbenzoic acid (0.29 g, 1.7 mmol) 7 7b O 6' OAc in dichloromethane (5 mL). The resulting mixture was 5' stirred at room temperature for 18 hours before being quenched with 10% sodium sulfite solution (15 mL). The organic layer was washed with water (20 mL) and brine
(20 mL) and dried over MgSO4. The solvent was evaporated in vacuo to give the crude product. Chromatography (SiO2, 50% DCM/ethyl acetate) afforded the title compound 290 (0.14 g, 27%) as a white solid. M.p. 158–161 °C (decomp.). 1H NMR (300 MHz,
CDCl3): δ 7.45 (2H, d, J = 8.8 Hz, H2′,6′), 7.34 (1H, d, J = 7.9 Hz, H7), 7.13 (2H, d, J = 8.8 Hz, H3′,5′), 6.74–6.69 (2H, m, H6, H4), 4.36 (1H, d, J = 11.8 Hz, H2a), 4.31 (1H, d, b J = 11.8 Hz, H2 ), 3.87 (1H, br s, H7b), 2.31 (3H, s, COCH3), 2.29 (3H, s, COCH3). 13 C NMR (75 MHz, CDCl3): δ 169.2 (CO), 169.1 (CO), 165.1 (ArC), 154.6 (ArC), 151.8 (ArC), 150.6 (ArC), 137.0 (ArC), 134.6 (ArC), 133.5 (ArC), 130.8 (ArC), 130.0 (ArC), 129.8 (ArC), 127.9 (ArC), 126.9 (ArC), 121.8 (ArC), 116.9 (ArC), 114.9 (ArC),
110.1 (ArC), 103.1 (ArC), 72.4 (C3), 55.6 (C4 or C2), 55.4 (C4 or C2), 21.2 (CH3). IR
(KBr): νmax 3426 (m), 3038 (w), 2914 (w), 1751 (s), 1712 (w), 1658 (w), 1612 (m), 1586 (w), 1510 (m), 1496 (m), 1460 (w), 1453 (w), 1434 (w), 1368 (m), 1286 (w), 1206 (s), 1195 (s), 1168 (s), 1142 (s), 1116 (s), 1049 (w), 1013 (m), 975 (w), 959 (w), 909 -1 -1 -1 (m), 878 (w), 842 (w) cm . UV-vis (MeOH): λmax 286 nm (ε 5,632 cm M ), 242 + (5,684), 207 (9,427). HRMS (+ESI): Found m/z 363.0841, [M+Na] ; C19H16O6Na required 363.0845.
‐ 199 ‐ 1a-(4-Hydroxyphenyl)-2,7b-dihydro-1aH-oxireno[2,3-c]chromen-5-ol (291) The epoxide 290 (86 mg, 0.25 mmol) and imidazole (210 4 HO O 2 mg, 3.1 mmol) were dissolved in ethanol (2 mL). The 1a 2' 6 3' mixture was heated at reflux for 45 minutes. Once cooled, 7 7b O 6' OH the solution was concentrated in vacuo to approximately 5' 0.5 mL. Water (2 mL) was added dropwise. The resulting precipitate was collected to give the title compound 291 (59 mg, 92%) as an off-white solid. M.p. 188–191 °C. 1H
NMR (300 MHz, d6-DMSO): δ 9.46 (1H, br s, OH), 9.33 (1H, br s OH), 7.21 (2H, d, J = 8.8 Hz, H2′,6′), 6.66 (2H, d, J = 8.8 Hz, H3′,5′), 6.34–6.15 (3H, m, H7, H6, H4), 5.77 (1H, br s, H7b), 4.50 (1H, d, J = 11.6 Hz, H2a), 3.96 (1H, d, J = 11.6 Hz, H2b), 13C
NMR (75 MHz, d6-DMSO): δ 159.2 (ArC), 154.6 (ArC), 151.8 (ArC), 150.6 (ArC), 137.0 (ArC), 134.6 (ArC), 133.5 (ArC), 130.8 (ArC), 130.0 (ArC), 129.8 (ArC), 127.9 (ArC), 126.9 (ArC), 121.8 (ArC), 116.9 (ArC), 113.2 (ArC), 109.4 (ArC), 102.3 (ArC),
72.4 (C3), 69.5 (C4), 60.3 (C2). IR (KBr): νmax 3398 (s), 2931 (w), 2801 (w), 2575 (w), 1656 (w), 1619 (s), 1594 (m), 1514 (s), 1480 (s), 1458 (m), 1415 (w), 1381 (w), 1321 (w), 1259 (m), 1240 (s), 1171 (s), 1139 (w), 1120 (m), 1109 (s), 1082 (m), 1042 (w), 976 (w), 855 (w), 836 (w), 817 (w), 792 (w), 741 (w), 661 (w) cm-1. UV-vis (MeOH): -1 -1 λmax 281 nm (ε 4,753 cm M ), 224 (21,423), 210 (29,545). HRMS (+ESI): Found m/z + 257.0802, [M+H] ; C15H13O4 required 257.0808.
1a-(3,4-Dimethoxyphenyl)-2,7b-dihydro-1aH-oxireno[2,3-c]chromen-5-ol (296) To a solution of the isoflavene 292 (0.25 g, 0.88 mmol) 4 HO O 2 in dichloromethane (5 mL) was added a solution of m- 1a 2' 6 OMe chloroperbenzoic acid (0.15 g, 0.87 mmol) in 7 7b O 6' OMe dichloromethane (5 mL). The resulting mixture was 5' stirred at room temperature for 18 hours before being quenched with 10% sodium sulfite solution (10 mL). The organic layer was washed with water (10 mL) and brine
(10 mL) and dried over MgSO4. The solvent was evaporated in vacuo and the resulting solid dissolved in ethanol (4 mL). Imidazole (0.50 g, 7.4 mmol) was added and the mixture was heated at reflux for 45 minutes. Once cooled, the solution was concentrated in vacuo to approximately 0.5 mL. Water (2 mL) was added dropwise. The resulting precipitate was collected to give the title compound 296 (0.19 g, 72%) as a brown solid. 1 M.p. 164–176 °C. H NMR (300 MHz, d6-DMSO): δ 9.33 (1H, br s OH), 7.11–6.95 (3H, m, H5, H2′,H6′), 6.89 (1H, d, J = 8.4 Hz, H5′), 6.38–6.26 (2H, m, H6, H8), 5.84
‐ 200 ‐ (1H, br s, H4), 4.56 (1H, d, J = 11.6 Hz, H2a), 3.98 (1H, d, J = 11.6 Hz, H2b), 3.72 (3H, 13 s, OMe), 3.69 (3H, s, OMe). C NMR (75 MHz, d6-DMSO): δ 157.8 (ArC), 154.5 (ArC), 148.2 (ArC), 148.1 (ArC), 134.3 (ArC), 131.3 (ArC), 128.0 (ArC), 127.0 (ArC), 121.6 (ArC), 120.4 (ArC), 117.6 (ArC), 113.1 (ArC), 111.2 (ArC), 110.9 (ArC),
109.7(ArC), 108.9 (ArC), 102.4 (ArC), 72.1 (C3), 69.5 (C4), 60.3 (C2), 55.4 (OCH3).
IR (KBr): νmax 3447 (s), 3128 (w), 3012 (w), 2962 (w), 2936 (w), 2838 (w), 2677 (w), 2593 (w), 1621 (s), 1592 (m), 1513 (s), 1475 (s), 1416 (w), 1374 (w), 1330 (w), 1294 (w), 1259 (w), 1229 (m), 1170 (s), 1128 (s), 1114 (m), 1074 (m), 1048 (w), 1023 (m), -1 847 (w), 810 (w), 784 (w), 764 (w), 749 (w), 738 (w) cm . UV-vis (MeOH): λmax 275 nm (ε 6,832 cm-1M-1), 205 (20,106). HRMS (+ESI): Found m/z 301.1066, [M+H]+;
C17H17O5 required 301.1071.
1a-(3,4-Dimethoxyphenyl)-4-methyl-2,7b-dihydro-1aH-oxireno[2,3-c]chromen-5-ol (297) To a solution of the isoflavene 293 (0.25 g, 0.74 mmol) HO O 2 in dichloromethane (5 mL) was added a solution of m- 1a 2' 6 OMe chloroperbenzoic acid (0.15 g, 0.87 mmol) in 7 7b O 6' OMe dichloromethane (5 mL). The resulting mixture was 5' stirred at room temperature for 18 hours before being quenched with 10 % sodium sulfite solution (10 mL). The organic layer was washed with water (10 mL) and brine
(10 mL) and dried over MgSO4. The solvent was evaporated in vacuo and the resulting solid dissolved in ethanol (4 mL). Imidazole (0.50 g, 7.4 mmol) was added and the mixture was heated at reflux for 45 minutes. Once cooled, the solution was concentrated in vacuo to approximately 0.5 mL. Water (2 mL) was added dropwise. The resulting precipitate was collected to give the title compound 297 (0.18 g, 77%) as a brown solid. 1 M.p. 119–125 °C. H NMR (300 MHz, d6-DMSO): δ 9.33 (1H, br s OH), 7.01–6.93 (2H, m, H2′, H5′), 6.63 (1H, dd, J = 2.3 Hz, 8.4 Hz, H6′), 6.38 (1H, d, J = 8.3 Hz, H5), 6.09 (1H, d, J = 8.3 Hz, H6), 5.84 (1H, br s, H4), 4.59 (1H, d, J = 11.6 Hz, H2a), 4.08 (1H, d, J = 11.6 Hz, H2b), 3.70 (3H, s, OMe), 3.67 (3H, s, OMe). 13C NMR (75 MHz, d6-DMSO): δ 157.8 (ArC), 154.5 (ArC), 148.2 (ArC), 148.1 (ArC), 134.3 (ArC), 131.3 (ArC), 128.0 (ArC), 127.0 (ArC), 121.6 (ArC), 120.4 (ArC), 117.6 (ArC), 113.1 (ArC), 111.2 (ArC), 110.9 (ArC), 109.7(ArC), 108.9 (ArC), 102.4 (ArC), 72.1 (C3), 69.5 (C4),
60.3 (C2), 55.4 (OCH3). IR (KBr): νmax 3315 (m), 3122 (m), 3007 (m), 2934 (m), 2836 (m), 2698 (w), 1609 (s), 1516 (s), 1467 (s), 1440 (s), 1416 (m), 1375 (w), 1329 (w),
‐ 201 ‐ 1259 (s), 1211 (w), 1143 (m), 1095 (s), 1065 (s), 1024 (m), 929 (w), 862 (w), 815 (w), -1 -1 -1 794 (w), 761 (m), 661 (m) cm . UV-vis (MeOH): λmax 278 nm (ε 5,359 cm M ), 212 + (39,590). HRMS (+ESI): Found m/z 315.1222, [M+H] ; C18H18O5 required 315.1227.
7-Methoxy-3-(4-methoxyphenyl)-2H-chromene (298) To a mixture of phenoxodiol 14 (2.03 g, 8.43 mmol) 8 MeO O 2 and potassium carbonate (1.73 g, 12.5 mmol) in 2' 6 3' acetone (20 mL) was added methyl iodide (10.4 mL, 5 4 6' OMe 167 mmol). The mixture was heated at reflux for 17 5' hours. The solvent was evaporated in vacuo and the residue dispersed in water (40 mL). The resulting mixture was extracted with dichloromethane (2 × 20 mL). The extracts were dried over MgSO4. Solvent was evaporated in vacuo to give the title compound 298 (2.06 g, 91%) as an orange solid. M.p. 161–164 °C, Lit223 161 °C. 1H NMR (300
MHz, CDCl3): δ 7.42 (2H, d, J = 8.8 Hz, H2',6'), 6.99 (1H, d, J = 8.4 Hz, H5), 6.89 (2H, d, J = 8.8 Hz, H-3',5'), 6.68 (1H, br s, H4), 6.50–6.42 (3H, m, H6, H8), 5.12 (2H, d, J = 1.4 Hz, H2), 3.82 (3H, s, OMe), 3.79 (3H, s, OMe).
4-(7-Acetoxy-4-(2-(3-chlorophenyl)-2-oxoethyl)-3-hydroxychroman-3-yl)phenyl acetate (299) To a solution of diacetoxyphenoxodiol 111 (500 mg, 8 AcO O 2 OH 2' 1.54 mmol) in dichloromethane (10 mL) was added m- 6 3' 5 chloroperbenzoic acid (300 mg, 1.74 mmol) in portions, O O 6' OAc over a period of 5 minutes. The reaction mixture was 5' 2" 6" stirred at room temperature for 4 days before being Cl 5" quenched with 10 % sodium sulfite solution (10 mL). 4" The organic layer was washed with water (10 mL) and brine (10 mL) and dried over
MgSO4. The solvent was evaporated in vacuo. Chromatography (SiO2, CHCl3) afforded the title compound 299 (390 mg, 51%) as a white, crystalline solid. M.p. 190– 1 193 °C. H NMR (300 MHz, CDCl3): δ 7.97 (1H, dd (app. t), J = 1.7 Hz, 1.8 Hz, H2″), 7.88 (1H, ddd, J = 1.2 Hz, 1.7 Hz, 7.8 Hz, H4″), 7.61 (2H, d, J = 8.8 Hz, H2ʹ,6ʹ), 7.54 (1H, ddd, J = 1.2 Hz, 1.8 Hz, 8.0 Hz, H6″), 7.39 (1H, dd (app. t), J = 7.8 Hz, 8.0 Hz, H5″), 7.19 (1H, d, J = 8.3 Hz, H5), 7.09 (2H, d, J = 8.8 Hz, H3ʹ,5ʹ), 6.72 (1H, br s, H4), 6.71–6.67 (2H, m, H6, H8), 4.38 (1H, d, J = 12.0 Hz, H2a), 4.30 (1H, d, J = 12.0 Hz, b 13 H2 ), 2.68 (1H, br s, OH), 2.29 (3H, s, COCH3), 2.27 (3H, s, COCH3). C NMR (75
‐ 202 ‐ MHz, CDCl3): δ 169.2 (CO), 169.1 (CO), 165.2 (CO), 154.7 (ArC), 152.0 (ArC), 150.7 (ArC), 137.1 (ArC), 134.8 (ArC), 133.6 (ArC), 130.9 (ArC), 130.1 (ArC), 129.9 (ArC), 128.0 (ArC), 127.0 (ArC), 121.9 (ArC), 117.0 (ArC), 115.1 (ArC), 110.2 (ArC), 71.6
(C3), 71.1 (C4), 70.6 (C2), 21.1 (CH3). IR (KBr): νmax 3449 (s), 3076 (w), 2988 (w), 2958 (w), 1760 (s), 1700 (s), 1619 (m), 1594 (m), 1574 (w), 1504 (s), 1468 (m), 1436 (m), 1429 (m), 1397 (w), 1369 (s), 1333 (m), 1291 (s), 1280 (m), 1253 (s), 1204 (s), 1173 (s), 1151 (s), 1127 (s), 1112 (m), 1077 (s), 1033 (s), 1017 (m), 961 (w), 942 (w), 930 (w), 915 (m), 892 (w), 856 (w), 840 (w), 823 (w), 760 (w), 750 (m), 735 (w), 687 -1 -1 -1 (w), 670 (w) cm . UV-vis (MeOH): λmax 282 nm (ε 2,345 cm M ), 206 (27,577). + HRMS (+ESI): Found m/z 519.0805, [M+Na] ; C26H21ClO8Na required 519.0817.
1-(3-Chlorophenyl)-2-(3-hydroxy-7-methoxy-3-(4-methoxyphenyl)chroman-4- yl)ethanone (300) To a solution of dimethoxyphenoxodiol 298 (0.60 g, 8 MeO O 2 OH 2' 2.3 mmol) in dichloromethane (6 mL) was added a 6 3' 5 solution of m-chloroperbenzoic acid (0.60 g, 3.5 mmol) O O 6' OMe in dichloromethane (7 mL). The reaction mixture was 5' 2" 6" stirred at room temperature for 4 days before being Cl 5" quenched with 10 % sodium sulfite solution (10 mL). 4" The organic layer was washed with water (10 mL) and brine (10 mL) and dried over
MgSO4. The solvent was evaporated in vacuo to give the title compound 300 (0.83 g, 1 81%) as an orange solid. M.p. 140–143 °C. H NMR (300 MHz, CDCl3): δ 7.91 (1H, dd (app. t), J = 1.7 Hz, 1.8 Hz, H2″), 7.89 (1H, ddd, J = 1.2 Hz, 1.7 Hz, 7.8 Hz, H4″), 7.55–7.50 (3H, m, H2ʹ,6ʹ, H6″), 7.39 (1H, dd (app. t), J = 7.8 Hz, 8.0 Hz, H5″), 7.12 (1H, d, J = 8.3 Hz, H5), 6.87 (2H, d, J = 8.8 Hz, H3ʹ,5ʹ), 6.62 (1H, br s, H4), 6.50 (1H, dd, J = 2.3 Hz, 8.3 Hz, H6), 6.46 (1H, d, J = 2.3 Hz, H8), 4.36 (1H, d, J = 12.0 Hz, H2a), 4.33 (1H, d, J = 12.0 Hz, H2b), 3.77 (6H, s, OMe), 2.62 (1H, br s, OH). 13C NMR (75
MHz, CDCl3): δ 165.5 (CO), 161.5 (ArC), 159.7 (ArC), 155.3 (ArC), 134.8 (ArC), 133.6 (ArC), 132.1 (ArC), 131.5 (ArC), 130.7 (ArC), 130.0 (ArC), 128.1 (ArC), 127.1 (ArC), 114.17 (ArC), 111.7 (ArC), 108.8 (ArC), 110.3 (ArC), 72.4 (C3), 70.7 (C4), 70.6
(C2), 55.5 (OCH3), 55.4 (OCH3). IR (KBr): νmax 3441 (m), 3072 (w), 3002 (w), 2957 (w), 2936 (w), 2913 (w), 2837 (w), 1724 (w), 1679 (w), 1615 (s), 1578 (m), 1513 (s), 1464 (w), 1443 (w), 1426 (w), 1273 (s), 1252 (s), 1196 (m), 1184 (m), 1162 (s), 1115 (m), 1072 (m), 1030 (s), 954 (w), 907 (w), 828 (m), 747 (w) cm-1. UV-vis (MeOH):
‐ 203 ‐ -1 -1 λmax 286 nm (ε 5,089 cm M ), 204 (20,974). HRMS (+ESI): Found m/z 441.1084, + [M+H] ; C24H22ClO6 required 441.1099.
5-Methoxy-1a-(4-methoxyphenyl)-2,7b-dihydro-1aH-oxireno[2,3-c]chromone (301) To a solution of the isoflavanol ester 300 (0.57 g, 1.3 4 MeO O 2 mmol) in toluene (25 mL) was added 85% phosphoric 1a 2' 6 3' acid. The mixture was heated to 80 °C for 18 hours. 7 7b O 6' OMe Once cooled the reaction mixture was neutralised with 5' saturate d NaHCO3 solution (20 mL). The organic layer was washed with water (20 mL) and brine (20 mL ) and dried over MgSO4. Solvent was evaporated in vacuo to give the title compound 301 (0.33 g, 88%) as a brown amorphous solid. M.p. 104–104 °C 1 (decom p.). H NMR (300 MHz, CDCl3): δ 7.07 (2H, d, J = 8.8 Hz, H2′,6′), 6.90 (1H, d, J = 8.2 Hz, H5), 6.86 (2H, d, J = 8.8 Hz, H3′,5′), 6.67 (1H, d, J = 2.1 Hz, H8), 6.63 (1H, dd, J = 2.1 Hz, 8.2 Hz, H6), 4.66 (1H, br s, H4), 4.56 (1H, d, J = 12.5 Hz, H2a), 4.46 (1H, d, J = 12.5 Hz, H2b), 3.82 (3H, s, OMe), 3.78 (3H, s, OMe). 13C NMR (75 MHz,
CDCl3): δ 165.0 (ArC), 159.2 (ArC), 155.6 (ArC), 130.4 (ArC), 129.8 (ArC), 128.5 (ArC), 117.0 (ArC), 114.5 (ArC), 110.1 (ArC), 103.2 (ArC), 72.2 (C3), 55.6 (C4 or C2),
55.4 (C4 or C2), 55.0 (OCH3). IR (KBr): νmax 3436 (m), 3005 (w), 2962 (w), 2936 (w), 2837 (w), 1738 (w), 1609 (s), 1577 (m), 1514 (s), 1504 (s), 1456 (m), 1443 (m), 1275 (m), 1251 (s), 1200 (m), 1184 (m), 1161 (s), 1114 (m), 1072 (w), 1025 (s), 970 (w), 953 -1 (w), 926 (w), 825 (s), 777 (w), 748 (w), 723 (w) cm . UV-vis (MeOH): λmax 285 nm (ε -1 -1 + 5,721 cm M ), 205 (20,289). HRMS (+ESI): Found m/z 285.1129, [M+H] ; C17H16O4 required 285.1121.
‐ 204 ‐ CHAPTER NINE
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