An Effort to Address Antibiotic Resistance

Desmethyl Analogs of Telithromycin: An Effort to Address Antibiotic Resistance

A Dissertation Submitted to the Temple University Graduate Board

in Partial Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

Venkata Velvadapu

August, 2011

Examining Committee Members:

Dr. Rodrigo B. Andrade, Research Advisor, Chemistry Dr. Franklin A. Davis, Committee Chair, Chemistry Dr. William M. Wuest, Committee Member, Chemistry Dr. Kevin C. Cannon, External Committee Member, Chemistry

Venkata Velvadapu

2011

ABSTRACT

The development of antibiotic resistance has been an inevitable problem leading to an increased demand for novel antibacterial drugs. To address this need, we initiated a structurebased drug design program wherein desmethyl analogues (i.e., CH 3H) of the

3rd generation macrolide antibiotic telithromycin were prepared via chemical synthesis.

Our approach will determine the biological functions of the methyl groups present at the

C4, C8 and C10 position of the ketolide. These structural modifications were proposed based on the structural data interpreted by Steitz and coworkers after obtaining crystal structures of macrolides erythromycin and telithromycin bound to the 50S ribosomal subunits of H.marismortui. Steitz argued that in bacteria, A2058G mutations confer resistance due to a steric clash of the amino group of guanine 2058 with the C4 methyl group. In turn, we hypothesize that our desmethyl analogs are predicted to address antibiotic resistance arising from this mutation by relieving the steric clash.

To readily access the analogs, we proposed to synthesize, 4,8,10tridesmethyl telithromycin, 4,10didesmethyl telithromycin, 4,8didesmethyl telithromycin and 4 desmethyl telithromycin as four targeted desmethyl analogs of telithromycin. This thesis includes the total synthesis and biological evaluation of 4,8,10tridesmethyl telithromycin and 4,10didesmethyl telithromycin analogs and the progress towards the total synthesis of 4desmethyl telithromycin analog.

We employed NozakiHiyamaKishi (NHK) and ring closing metathesis (RCM) reactions as the two macrocyclization methods towards the total synthesis of these analogs. The RCM was superior compared to the NHK macrocyclization where in grams of these macrocycles were accessible. An optimized method for installing the desosamine iii

sugar onto the C5 alcohol using the Woodward’s thiopyrimidine donor was developed.

Baker’s onepot carbamoylation/intramolecular azaMichael method was utilized to install the oxazolidinone side chain of telithromycin.

The total synthesis of 4,8,10tridesmethyl telithromycin required 42 steps overall

(31 steps in the longest linear sequence). The analog 4,10didesmethyl telithromycin was synthesized in 44 steps overall (32 steps in the longest linear sequence). These analogs were able to inhibit bacterial growth, presumably by targeting the bacterial ribosome. In addition, 4,8,10tridesmethyl telithromycin analog was more potent than telithromycin against an A2058T mutant and 4,10didesmethyl telithromycin analog was more potent than 4,8,10tridesmethyl telithromycin against an A2058G mutant.

Also, a concise synthesis of Ddesosamine was accomplished in five steps and in

15% overall yield from commercial methyl αDglucopyranoside. Other efforts involved the contribution of key intermediates towards the total synthesis of 4,8didesmethyl telithromycin are described.

Dedication

This dissertation is dedicated to my wonderful wife Soujanya whose constant

support and encouragement made my tough journey possible.

ACKNOWLEDGMENTS

First and foremost I give my utmost thanks to my thesis advisor, Dr. Rodrigo B.

Andrade, for his support and guidance throughout the duration of my PhD career at

Temple University. His understanding, perception and handson expertise served as an example for my graduate career. I will always remember him for what he has done for me. His enthusiasm, scientific curiosity and innovative ideas are something I will strive for in my career. Most of all his fascination towards chemistry, Indian food and his clichés are something I will always cherish. I wish him the best and hope to see him continue being a great mentor.

I would like to give special thanks to Dr. Franklin A. Davis, as my defense committee chair and my mentor for my first years at Temple. I would like to thank Dr.

William M. Wuest and Dr. Kevin C. Cannon for their valuable suggestions, guidance, and willingness to serve on my doctoral dissertation committee.

I am grateful to Osmania University, MNR PG College faculty Dr. Srinivas

Reddy, Dr. Saritha Rajender and Dr. Sarbani Pal for providing constant encouragement, support, and motivation to pursue my research career.

I would like to thank Dr. Tapas Paul whose research expertise and practices in the lab supported me throughout my PhD. I would like to thank my fellow graduate students

Mr. Bharat Wagh, Mr. Gopal Sirasani, Mr. Justin Kaplan, Mr. Ian Glassford, Mr. Chary

Munagla, Mr. Praveen Kokkonda, Mr. Vijay Chatare and Ms. Miseon Lee for their co operation and support. Bharat, Ian and Justin deserve special mention, as they inspire me

through sharing scientific discussions as well as discussions about life. I would like to thank Ian and Justin for helping me in editing my thesis.

I feel fortunate to have interacted with other students like Dr. Goutham Kodali,

Dr. Sunil Kulkarni, Dr. Madhavan, Dr. Rajeshraman Madathingal and Dr. Ramakrishna

Edupuganti who have an interesting perspective towards science and life. I would like to thank Dr. Jaykumar Gilbert, Dr. Vassil Boiadjiev and Dr. Shiva Vaddypally for sharing their valuable insight. I would like to thank Dr. Alfred Findeisen for his constant support as a teaching lab coordinator during my teaching assignments. I would also like to thank

Dr. Charles DeBrosse for his support and guidance in the NMR facilities.

I would like to express my thanks to all the chemistry department staff present and past. I wish to express my deep gratitude to lost friends the late. Mr. Warren Muir, and Mr. George McCurdy.

I would like to thank Mr. Dave Plasket for helping to make the glassware. Not to mention, I really appreciate his sense of humor.

All this work would not have been possible without the financial support from

Temple University and NIH grant number (AI080968). In that regard, I would like to thank the Department of Chemistry at Temple University for their financial support through teaching and research assistantships and providing an opportunity to pursue my graduate studies.

Finally, I wish to express my deepest love and gratitude to my parents, Velvadapu

Vishnuvardhan Rao, Vijaya Lakshmi, Kumar, Sumona, Srikrishna Sai, Rammurthy,

vii

Priya, Soujanya, Chakri and Chennakeshava Rao garu for their constant support, guidance, patience and understanding.

I would like to thank my friends Mohit, Sandeep, Swapna, Sharavan, Shiva,

Ravichandra, Deepan, Shashi, Sid, Srikanth, Satish, and Sushma for sharing memorable moments.

Overall I feel nothing is possible without the blessing of “ Shiridi Saibaba ” to whom I owe everything.

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TABLE OF CONTENTS

ABSTRACT ……………………………………………………………………………..iii

ACKNOWLEDGEMENTS …………………………………………………………….vi

LIST OF TABLES ……………………………………………………………………..xiii

LIST OF FIGURES ……………………………………………………………………xiv

LIST OF SCHEMES………………………………………………………………….xvii

CHAPTER

1. Concise Syntheses of D-Desosamine, 2-Thiopyrimidinyl Desosamine Donors

and Methyl Desosaminide Analogues from D-Glucose ………………………..1

1.1 Introduction...... 1

1.2 Background...... 2

1.3 Korte’s Synthesis of Desosamine (1962)……………………………………...4

1.4 Richardson’s Synthesis of Desosamine (1964)...... 5

1.5 Newman’s Degradation and Synthesis of Desosamine (1974)………………..6

1.6 Tietze’s Synthesis of Desosamine (1974)…………………….……………….8

1.7 Bauer’s Asymmetric Synthesis of Desosamine (1997)……………………….8

1.8 McDonald’s Asymmetric Formal Synthesis of Desosamine (2004)………….9

1.9 Crotti’s Ring Opening of 2,3Anhydrosugars (2002)………………………..10

1.10 Present Study……………………………………………………………….11

2. Desmethyl Analogs of Telithromycin to Address Antibiotic Resistance:

Synthesis and Biological Evaluation of (-)-4,8,10-Tridesmethyl Telithromycin

2.1 Background…………………………………………………………………..17

2.2 Macrolide Antibiotics………………………………………………………..20

2.3 Erythromycin……………………………………………………………...... 21

2.4 Spectrum of Activity…………………………………………………………22

2.5 Drawbacks……………………………………………………………………23

2.6 Second Generation Macrolide Antibiotics…………………………………...24

2.7 Mechanism of Action………………………………………………………...28

2.8 Mechanism of Antibiotic Resistance………………………………………...32

2.8.1 Ribosome Mutation and Modification……………………………………..33

2.8.2 Ribosome Methylation……………………………………………………..33

2.8.3 Efflux of Macrolides……………………………………………………….34

2.8.4 Inactivating Enzymes………………………………………………………34

2.9 Ketolides and Discovery of Telithromycin…………………………………..35

2.10 Third Generation Ketolide Antibiotics……………………………………..41

2.11 Present Study: Desmethylation as a Strategy for Overcoming Antibiotic

Resistance………………………………………………………………………..42

2.12 Steitz’s Explanation of Antibiotic Resistance from Structural Data……….44

2.13 Desmethylation Strategy and Proposed Desmethyl Analogs of

Telithromycin…………………………………………………………………….46

2.14 Molecular Modeling of Macrolide Conformations…………………………50

2.15 Fecikˈs Synthesis of Narbonolide…………………………………………..54

2.16 Kang’s Synthesis of Narbonolide…………………………………………..56

2.17 Total Synthesis of ()4,8,10Tridesmethyl Telithromycin…………………58

2.17.1 First Generation Approach……………………………………………….60

2.17.2 Second Generation Approach……………………………………………67

2.17.3 Installation of C5 Desosamine…………………………………………..71

2.17.4 Installation of Telithromycin Side Chain………………………………...76

2.18 Biological Evaluation of ()4,8,10Tridesmethyl Telithromycin………….78

3. Synthesis and Biological Evaluation of (-)-4,10-Didesmethyl Telithromycin

3.1 Introduction...………………………………………………………………...80

3.2 Molecular Modeling of 4,10Didesmethyl Telithromycin …………………..80

3.3 Retrosynthetic Plan…………………………………………………………..82

3.4 Forward Synthesis……………………………………………………………84

3.5 Biological Evaluation of ()4,10Didesmethyl Telithromycin……………...95

4. Progress towards the synthesis of 4-Desmethyl Telithromycin

4.1 Introduction...………………………………………………………………...97

4.2 Retrosynthetic Plan…………………………………………………………..97

4.3 Present Study…………………….…………………………………………..99

5. EXPERIMENTAL SECTION ………………………………………………..102

REFERENCES ……………………...... 186

BIBLIOGRAPHY ……………………………………………………………………..200

APPENDIX …………………………………………………………………………….213

xii

LIST OF TABLES

Table 1.1 Synthesis of C3 amino analogs of desosamine ………………………………15

Table 2.1 MIC data for ketolide Narbomycin……………………………………………36

Table 2.2 MIC data for ketolide 2.13 …………………………………………………….37

Table 2.3 MIC data of Oxazolidinones with various side chains including TEL ……….40

Table 2.4 MIC data of 2.31 using 1.6 as the baseline …………………………………...79

Table 3.1 Comparison of Overlap Coefficient of 2.31 , 2.32 with TEL …………………81

Table 3.2 Optimization of C6 Omethylation …………………………………………..88

Table 3.3 MIC data of 2.32 with 2.31 and 1.6 as the baseline…………………………...95

xiii

LIST OF FIGURES

Figure 1.1 Structure of Ddesosamine and Picromycin …………………………………..1

Figure 1.2 Macrolide antibiotics containing desosamine ………………………………...2

Figure 1.3 Structures of mycaminose, amosamine and rhodosamine …………………….3

Figure 1.4 Interactions of macrolide with the 50s subunit of D.radiodurans ……………..4

Figure 1.5 Structures of ethyl desosaminide and epoxide 1.19 …………………………...6

Figure 1.6 Structure showing the C3 and C2 attack of dimethylamine ………………...7

Figure 1.7 Nucleophilic ring opeing of 2,3Anhydrosugars …………………………….10

Figure 1.8 Woodward and Tatsuta desosamine donors …………………………………11

Figure 1.9 Nucleophilic attack onto the epoxide 1.45 …………………………………...12

Figure 2.1 Macrolide antibiotics with different ring sizes ………………………………20

Figure 2.2 Structural description of Erythromycin A …………………………………...21

Figure 2.3 Structure of Clarithromycin ………………………………………………….24

Figure 2.4 Structure of Azithromycin ………………………………………………...... 26

Figure 2.5 Structures of Roxithromycin and Dirithromycin …………………………….27

Figure 2.6 Structure of macrolide bound to the 50s ribosomal subunit of Hma ………...29

Figure 2.7 ERY and TEL bound to 50s subunit of Hma (pdb:1YI2 and 1YIJ)………….31

Figure 2.8 Cartoon showing antibiotic resistance………………………………………..32

Figure 2.9 Enzyme inactivation of macrolide …………………………………………...35

Figure 2.10 Ketolides and C3 hydroxy erythromycin A ……………………………….35

Figure 2.11 Key analogs of TEL ………………………………………………………...41

Figure 2.12 Ketolide antibiotics …………………………………………………………42

Figure 2.13 Graph showing number of new antibiotics …………………………………43 xiv

Figure 2.14 Selected distances of the C4 methyl and proposed steric clash……………45

Figure 2.15 Additional binding of the biaryl side chain ………………………………...46

Figure 2.16 C4 desmethylation to address antibiotic resistance ………………………..47

Figure 2.17 Wenders bryostatin analog ………………………………………………....48

Figure 2.18 Discodermolide analogs by Smith ……………………………………….....49

Figure 2.19 Desmethyl Telithromycin analogs ………………………………………….49

Figure 2.20 CSP data for 4,8,10tridesmethyl telithromycin…………………………….51

Figure 2.21 Structures of key intermediates …………………………………………….52

Figure 2.22 Structures of narbonolide and picronolide ………………………………....54

Figure 2.23 Retrosynthesis for the synthesis of the oxazolidinone ……………………..58

Figure 2.24 Retrosynthesis for installing desosamine onto C5…………………………59

Figure 2.25 Macrocyclization strategies…………………………………………………59

Figure 2.26 Retrosynthesis for acid 2.65 , diols 2.63 and 2.64 …………………………...60

Figure 2.27 Xray crystal structure of macrocycle 2.88 …………………………………66

Figure 2.28 Structures of GII and HGII ……………………………………………….69

Figure 3.1 Structure of 4,10didesmethyltelithromycin …………………………………80

Figure 3.2 CSP data of 2.32 ………………...... 81

Figure 3.3 CSP of 2.31 in Blue and CSP of 2.32 in Red ………………………………..82

Figure 3.4 Retrosynthesis of 2.32 to install the side chain………………………………82

Figure 3.5 Retrosynthesis of enone 3.3 ……………………………………………….....83

Figure 3.6 Retrosynthesis of macrocycle 3.4 ……………………………………………83

Figure 3.7 Retrosynthesis of acid 3.6 ……………………………………………………84

Figure 3.8 Structure of enone 3.9 ………………………………………………………..84

Figure 4.1 Structure of 4desmethyl telithromycin ……………………………………...97

Figure 4.2 Strategy for RCM across C10,11 with the C10 methyl…………………….98

Figure 4.3 RCM catalyst used …………………………………………………………...98

Figure 4.4 NHK cyclization with the C10methyl and C5 sugar……………………….99

xvi

LIST OF SCHEMES

Scheme 1.1 Korte’s Synthesis of racemic desosamine …………………………………..5

Scheme 1.2 Desosamine synthesis from methyl46ObenzylidineαD glucopyranoside………………………………………………………………………...... 5

Scheme 1.3 Racemic desosamine synthesis from epoxide 1.20 …………………………..6

Scheme 1.4 Acidic ring opening of epoxide 1.24 …………………………………………7

Scheme 1.5 Racemic synthesis of desosamine starting with 1.26 ………………………...8

Scheme 1.6 Conversion of 1.28 to desosamine …………………………………………..8

Scheme 1.7 Formal synthesis of methyl desosaminide starting from 1.31 ………………..9

Scheme 1.8 Asymmetric synthesis of desosamine starting from aldehyde 1.38 ………….9

Scheme 1.9 Synthesis of 1.54 from glucal 1.51 ………………………………………….12

Scheme 1.10 Synthesis of unexpected isomer 1.58 ……………………………………...13

Scheme 1.11 Synthesis of desosamine starting from glucose 1.55 ………………………14

Scheme 1.12 Synthesis of desosamine donors …………………………………………..15

Scheme 2.1 Degradation of ERY in acidic medium …………………………………….23

Scheme 2.2 Synthesis of CLA …………………………………………………………..25

Scheme 2.3 Synthesis of AZY …………………………………………………………..26

Scheme 2.4 Synthesis of ketolide from CLA …………………………………………....37

Scheme 2.5 Synthesis of C11, 12 Oxazolidinones ……………………………………..38

Scheme 2.6 Synthesis of Telithromycin ………………………………………………...39

Scheme 2.71 Regioselective glycosylation by Tatsuta ………………………………….52

Scheme 2.72 Final steps of Tatsuta ……………………………………………………...53

Scheme 2.8 Fecik’s synthesis of narbonolide……………………………………………55 xvii

Scheme 2.9 Kang’s synthesis of narbonolide……………………………………………56

Scheme 2.10 Synthesis of diols 2.64 and 2.63 …………………………………………...61

Scheme 2.11 Synthesis of regioisomer of 2.77 …………………………………………..62

Scheme 2.12 Synthesis of iodoester 2.84 ………………………………………………...63

Scheme 2.13 Synthesis of macrocycle 2.88 via NHK…………………………………...64

Scheme 2.14 Synthesis of macrocycle 2.88 via RCM …………………………………..65

Scheme 2.15 Synthesis of regioisomers 2.93 and 2.94 …………………………………..67

Scheme 2.16 Synthesis of NHK precursor 2.99 …………………………………………68

Scheme 2.17 Synthesis of the macrocycle 2.103 via NHK ……………………………..69

Scheme 2.18 Synthesis of macrocycle 2.103 via RCM …………………………………70

Scheme 2.19 Unexpected ketal formation between C9 carbonyl and C5 alcohol …….71

Scheme 2.20 Unsuccessful regioselective glycosylation with 2.111 …………………….72

Scheme 2.21 Attempt to isolate C5 alcohol and C9 keto compound 2.113 ……………72

Scheme 2.22 Unexpected C12 glycosylation …………………………………………..73

Scheme 2.23 Successful C5 glycosylation ……………………………………………..75

Scheme 2.24 Installation of TEL side chain …………………………………………….76

Scheme 2.25 Deprotection of the C3 TBS ……………………………………………..77

Scheme 2.26 C3 oxidation and methanolysis…………………………………...... 78

Scheme 3.1 Macrocyclic stereocontrolled methylation …………………………………85

Scheme 3.2 Macrocyclic methylation of 3.12 …………………………………………...85

Scheme 3.3 Synthesis of lactone 3.8 with the C8 methyl ………………………………86

Scheme 3.4 Xray structure of 3.15 ……………………………………………………...86

Scheme 3.5 Synthesis of C6 OMe 3.7 with the C8 methyl ……………………………87

xviii

Scheme 3.6 Synthesis of acid 3.6 ………………………………………………………..89

Scheme 3.7 Synthesis of ester 3.21 ………………………………………………………90

Scheme 3.81 Alternative method to synthesize 3.21 ……………………………………90

Scheme 3.82 Optimized synthesis of fragment 3.22 ……………………………………..91

Scheme 3.9 Synthesis of macrocycle 3.5 ………………………………………………...91

Scheme 3.10 Synthesis of C5 sugar 3.28 ……………………………………………….92

Scheme 3.11 Synthesis of enone with sugar 3.29 ……………………………………….93

Scheme 3.12 Installation of side chain: 3.30 ……………………………………………94

Scheme 3.13 The end game for the synthesis of 2.32 …………………………………...94

Scheme 4.1 Synthesis of C4 desmethyl macrocycle 4.9 ………………………………100

Scheme 4.2 Synthesis of NHK fragment 4.13 ………………………………………….100

Scheme 4.3 Unsuccessful NHK cyclization of 4.15 ……………………………………101

xix

CHAPTER 1: Concise Syntheses of DDesosamine, 2Thiopyrimidinyl Desosamine

Donors and Methyl Desosaminide Analogs from DGlucose

1.1 Introduction

Organic compounds that consist of carbon (C), oxygen (O) and hydrogen (H) with an empirical formula of C m(H 2O) n are called carbohydrates. Carbohydrates are also referred to as saccharides, which comes from the Greek word for sugar. 1 In general carbohydrates or saccharides with low molecular weights are called sugars. Replacement of one or more hydroxyl groups on the sugar with an amine group results in an amino sugar.1

It has been over one hundred and eighty years since the first amino sugars were discovered. 2 Amino sugars are ubiquitous in nature, occurring in plants, mammals, invertebrates and microorganisms. 3,4,5 Considerable interest in these sugars arose several decades ago when researchers determined that they were components of the antibiotic streptomycin. 4,5 They were also found to be the constituents of blood, antigenic determinants, glycolipids, calicheamycins and esperamycins. 5

Figure 1.1 Structure of Ddesosamine and Picromycin

Me 9 Me Me HO 11 Me 6 O 12 NMe2 Me N Me HO 2 Et O O O Me HO OH 3 O O Me Ddesosamine (1.1 ) Picromycin ( 1.2 )

Desosamine ( 1.1 ) is an amino sugar found in various natural products having a range of biological activity. It was originally named picrocin, after the first isolated macrolide antibiotic, picromycin (1.2 ) (Figure 1.1). 6 It is a 3,4,6trideoxy3dimethyl

aminohexose whose structure was elucidated using a combination of degradation studies

and NMR experiments during the period 1961 to 1964.7

1.2 Background

Desosamine is the basic nitrogencontaining component of the macrolide antibiotics such as erythromycin ( 1.3 ), clarithromycin (1.4 ), azithromycin ( 1.5 ), and

telithromycin ( 6) (Figure 1.2).4,5 The absence of desosamine renders these macrolides biologically inactive. 5

Figure 1.2 Macrolide antibiotics containing desosamine

O O Me Me 9 Me Me Me Me Me Me HO OH 11 OH HO OMe 12 6 NMe OH 2 NMe Me HO 2 Et O O O Me Me HO Et O O O Me

O O OMe O O OMe Me Me Me Me O OH O OH Me Me Erythromycin ( 1.3 ) Clarithromycin ( 1.4 )

Me N N Me 9 Me O N Me Me N ( ) Me 4 Me HO OH O 11 OH 6 NMe N 9 12 2 Me Me HO O O Me 11 OMe Et O O 6 Me 12 NMe2 HO O O OMe Et O O O Me 3 Me Me Me O O O OH Me Me

Azithromycin ( 1.5 ) Telithromycin ( 1.6 )

It was during the period of 19611965 that scientists realized that various amino sugars were present as a structural component of antibiotics (Figure 1.3). Along with desosamine ( 1.1 ) other amino sugars include mycaminose (3,6dideoxy3 dimethylaminohexose) ( 1.7 ), amosamine (2,4,6dideoxy3dimethylaminohexose) ( 1.8 ), and rhodosamine (2,3,6trideoxy3dimethylaminohexose) ( 1.9 ) in magnamycin

(carbomycin), amicetin and rhodomycin, respectively. 6

Figure 1.3 Structures of mycaminose, amosamine and rhodosamine

OH Me Me Me O O HO HO O Me N 2 Me2N Me2N HO OH OH OH mycaminose ( 1.7 ) amosamine ( 1.8 ) rhodosamine ( 1.9 )

In 1962, NMR studies by Harry S. Mosher proved it belonged to the Dfamily of

sugars. In the same year, Stacey and Newman provided chemical evidence to establish a

trans relationship between the C2’ hydroxyl and the C3’dimethylamino group. 6 In

1964, degradation studies were performed by Newman where 1 was converted to 2

ethoxy3,4epoxy6methyltetrahydrofuran and the reconversion of the latter to

desosamine were done. 7

Macrolide antibiotics inhibit bacterial protein synthesis by reversibly binding to the 50S ribosome within the 23S ribosomal RNA and various other proteins. 8 Crystal

structures of the 50S ribosomal subunit of D.radiodurans bound with erythromycin strongly suggests that the 2’hydroxyl group of the desosamine moiety forms hydrogen bonds with nitrogen atoms N1 of 23S rRNA residue A2058 and A2059 in the peptidyl transferase center (E.coli numbering). The protonated form of the 3’dimethyl amino

group of desosamine interacts with the backbone oxygen of guanosine 2505 in the peptidyl transferase centre through ionic interactions (Figure 1.4). 9

Figure 1.4 Interactions of macrolide with the 50s subunit of D.radiodurans

Since its structural elucidation by chemical degradation and NMR studies, D desosamine has elicited considerable synthetic interest. Many of these syntheses were reported in the early 1960s.

1.3 Korte’s Synthesis of Desosamine (1962)

In 1962, Korte and coworkers reported a racemic synthesis of desosamine starting from 6methyl5,6dihydro4Hpyran3carboxylate ( 1.10). Allylic bromination of rac1.10 with NBS followed by the treatment with aqueous dimethylamine gave 1.11 with the amine at the C3 (Scheme 1.1) position. Dihydroxylation with hydrogen peroxide followed by decarboxylation gave desosamine ( 1.1 ).10

Scheme 1.1 Korte’s Synthesis of racemic desosamine

N(CH3)2 N(CH3)2 COOR NBS COOR COOR HN(CH3)2 H2O2 OH rac1.1

H3C O H3C O H3C O OH rac1.10 1.11 1.12

1.4 Richardson’s Synthesis of Desosamine (1964)

In 1964, Richardson reported another synthesis starting from methyl46O

benzylidineαDglucopyranoside 1.13. Acetylation of 1.13 with a mixture of hot acetic

Scheme 1.2 Desosamine synthesis from methyl46ObenzylidineαDglucopyranoside

I 1) Ac2O, Pyridine Ph O 2) 50% CH3COOH HO 1) CH SO Cl, Pyridine O O O 3 2 HO 2) NaI, KSCN I O AcHN AcHN AcHN HO OMe 95% AcO 81% AcO OMe OMe 1.13 1.14 1.15

1) Raney Ni H3C 1) HCOOH, HCOH 2) Hot NaOH O 2) HCl H 2 N 1.1 AcO 90% OMe 30% 1.16

anhydride and pyridine in DMF gave the 2Oacetate, which was then treated with hot

50% aqueous acetic acid to give 3acetamido2Oacetyl3deoxyαDglucopyranoside

(1.14) in 95% yield (Scheme 1.2). Reaction with methanesulfonyl chloride in pyridine

followed by the treatment of potassium thiocyanate and NaI gave the bisiodide 1.15 in

81% yield. Reductive removal of the iodosubstituents with Raney nickel in presence of

hydrogen and subsequent treatment with hot sodium hydroxide to give 3,4,6trideoxy3

diemthylaminoαDxylo hexopyranoside (1.16). The amine 1.16 was reductively

dimethylated under EschweilerClarke conditions (formic acid and formaldehyde) and

subsequent hydrolysis using concentrated hydrochloric acid yielded 1.1 .11

1.5 Newman’s Degradation and Synthesis of Desosamine (1974)

It 1964, Newman reported the degradation of 1.1 to 2ethyl3,4epoxy6methyl

tetrahydropyran (1.19) and the reconversion of the latter to racemic desosamine (Figure

1.5). Ethyl desosaminide (1.17) was degraded to epoxide 1.19 by pyrolysis of its

quaternary hydroxide derivative 1.18, which was in turn prepared from the corresponding

methiodide. 7

Figure 1.5 Structures of ethyl desosaminide and epoxide 1.19 .

Me Me Me O O O Me N - + 2 HO Me3N HO OEt HO OH O OEt

1.17 1.18 1.19

Racemic 1.19 was synthesized by the treatment of lithium acetylide 1.21 with propylene oxide ( 1.20) to give 1,1diethoxy5hydroxyhex2yne ( 1.23) in 60% yield.

Hydrogenation in presence of acid gave the dihydropyran 1.24 as a major trans isomer in

85% yield (Scheme 1.3).

Scheme 1.3 Racemic desosamine synthesis from epoxide 1.20 .

OH Me OEt OEt O BuLi H Me OEt 1.23 OEt

1.20 1.21 1) H2 /Pd 2) H+

H3C O OEt 1.24

Epoxidation of 1.24 was investigated with perbenzoic acid. An anomeric mixture

of epoxides in which the epoxide is trans to the C5 methyl group was found to be the

Scheme 1.4 Acidic ring opening of epoxide 1.24

H H OEt Peracid OEt O Me Me

H H O O 1.24 1.25 major product (Figure 1.6). Attack of the peracid would occur from the side that is less sterically hindered, thus giving epoxide 1.25.7 Treatment of 1.25 with aqueous

dimethylamine gave the ring opened product (Scheme 1.4). The epoxide ring opens

regioselectivity at C3 as nucleophilic attack takes the position furthest from C1. Though

attack at C2 position is favored stereoelectronically, it proceeds through a high energy

twist boat transition state and is less favorable. Nucleophilic attack at C3 is favorable as

it proceeds through a lower energy chair transition state. Thus 1.25 when treated with

aqueous dimethylamine solution in ethanol gave racemic ethyl desosaminide 1.17α with

a major α anomer. 7

Figure 1.6 Structure showing the C3 and C2 attack of dimethylamine

H C3 attack Me OEt O Me O Me2N H C -3 Attack HO OEt O 1.17α

C -2 Attack 1.25

Hydrolysis of synthetic 1.17α gave an identical compound to 1.17 thus confirming the synthesis of desosamine. 7 Later in 1974, Baer and Chiu reported the synthesis of L

Desosamine the enantiomer of DDesosamine. 7

1.4 Tietze’s racemic Synthesis of Desosamine (1974)

In 1990, Tietze employed a heteroDielsAlder reaction to access the amino frame

work of 1.1 (Scheme 1.5). Racemic phenylthioactivated enamino ketone 1.26 underwent

Scheme 1.5 Racemic synthesis of desosamine starting with 1.26

NPht NPht NPht

PhS OAc Toluene/CH2Cl2/ 1:1 OAc OAc 4 230h/ 125 °C/ 4 3 3

MeO2C O EtO MeO2C O OEt 97% MeO2C O OEt 1.26 1.27 1.28 1.29

DielsAlder cyclization with 2ethyoxyvinylacetate ( 1.27) with the desired 3,4trans

configuration in 9:1 selectivity. 12 Dihydropyran 1.28 was reduced with Raney nickel in

methanol followed by NaBH 4 and acetic acid affording the N,N desmethylated

desosamine derivate 1.30 (Scheme 1.6). 12

Scheme 1.6 Conversion of 1.28 to desosamine

Me NaBH4 /IPA /H2O Me AcOH/ 90 °C Raney-Ni/MeOH O OEt O OEt 1.28 PhtN HOAc H2N 65% AcO 71% HO

1.29 1.30

1.5 Bauer’s Asymmetric Formal Synthesis of Methyl Desosaminide (1997)

In 1997, Bauer reported syntheses of a methyl desosaminide (glycoside of

desosamine). Synthesis began with enantiomerically pure 6hydroxymethyl2methoxy

5,6dihydro2Hpyran (1.31 ). Tosylation followed by LAH reduction furnished 1.32 ,

which upon epoxidation with mCPBA gave a mixture of epoxides 1.33 and 1.34 in a 2:1

ratio (Scheme 1.7). 13

Scheme 1.7 Formal synthesis of methyl desosaminide starting from 1.31

1) TsCl, Py Me Me Me OH 2) LAH, THF m-CPBA O O O O O O

OMe OMe OMe OMe 1.31 1. 32 1.33 1.34

Me N Me HO Me Me 0.2 N MeONa/ MeOH 2 O 40% aq Me2NH O O O HO Me2N 60% OMe OMe OMe 1.34 1.36 1.37

Treatment of epoxide 1.35 with MeONa and aqueous dimethylamine gave methyldesosaminide 1.36 in 60% yield and 15% of 1.37 .13

1.6 McDonald’s Asymmetric Synthesis of Desosamine (2004)

The most recent synthesis of Ddesosamine was reported in 2004 by Mc Donald and coworkers. The stereoselective synthesis of Ddesosamine was achieved from a glycal generated by tungsten carbonylcatalyzed cycloisomerization of the corresponding amino alkynol 1.42 giving 1.43 (Scheme 1.8). The amino alkynol 1.42 is prepared from

aldehyde 1.38 . Treatment of 1.43 with NaH and MeI followed by LAH gave the C3

dimethyl amino functionality of 1.44. Dihydroxylation of the olefin using modified

Sharpless protocol gave Ddesosamine. 14

Scheme 1.8 Asymmetric synthesis of desosamine starting from aldehyde 1.38

Zn(OTf)2 (+)-N-methylephidrine 1) MsCl Me OTBS Me OTBS TMS-acetylene Me OTBS 2) NaN3 TMS 3) LAH TMS H

O OH NH2 1.38 1.39 1.40 Me OTBS 1) (Boc) 2O Me OH TMS 2) TBAF H

NH2 NHBoc 1.41 1.42 9

Modified Me OH Me O 1) NaH, MeI Me O Sharpless H 5% W(CO)6, DABCO, hν dihydroxylation 2) LAH, THF 1.1 90% 90% NHBoc NHBoc NMe2 1.42 1.43 1.44

1.7 Crotti’s Ring Opening of 2,3Anhydrosugars (2002)

An extensive study of the regioselective opening of 2,3anhydrosugars was made

by Crotti in 2002. Stereoelectronic trans 1,2diaxial products are formed, when

nucleophilic attack takes place at the C2 position in 1.45 . This can be achieved with the

use of a metal that chelates onto the C1 and the epoxide oxygen forcing a conformation

in which the C6 methyl group is trans to the oxirane ring. Attack at the C3 position is

electronically favored though the transition state involves an unfavorable 1,3diaxial

interaction with the methyl group (Figure 1.7).

Figure 1.7 Nucleophilic ring opening of 2,3Anhydrosugars : Nucleophiles (Nu: O, N, S) Standard Conditions:

C - 3 Me Nu C - 2 Me attack Me attack O O O Nu OH O HO OMe OMe OMe 1.47 1.45 1.46 (1020%) (6085%) Chelating Conditions:

Nu C - 2 Me Nu C - 3 Me Me attack Me attack O O O O Nu OH O O HO OMe OMe OMe OMe M + 1.47 1.45 1.46 (2030%) (60%)

Under standard nonchelation conditions, nucleophilic attack depends mainly on the product stability, thus a C2 axial attack is disfavored as it leads to an unstable trans diaxial product. When a metal chelates to both anomeric and oxirane oxygens the regiochemistry gets slightly modified and 2030% of C2 attack takes place. 15

1.7 Present Study

Our interest in macrolide antibiotics led us to the syntheses of desosamine and analogs of the C3 amino derivatives of macrolide antibiotics. With this idea, we wanted to develop a concise, inexpensive and scalable route for the synthesis of Ddesosamine

(1.1 ). Crotti and coworkers showed that nucleophilic substitution onto 2,3

anhydrosugars occurs largely onto the C3 position with a variety of nucleophiles. Hence,

we wanted to access the same intermediate 1.45 from which we can synthesize C3

amino analogs and convert them into known desosamine donors (Figure 1.8). Woodward

and Tatsuta developed 2thiopyrimidinyl donors 1.48 and 1.49 which were utilized as

desosamine donors in the synthesis of erythromycin A (Woodward and Tatsuta) and

erythromycin B (Martin et al). 16, 17, 28, 29

Figure 1.8 Woodward and Tatsuta desosamine donors

Me Me Me O O N O Me2N Me2N R2N HO OH RO S N HO OMe

R = CO2Me R = Ac 1.1 1.48, 1.49 1.50

Furthermore, this intermediate could be utilized in the synthesis of TDPαD desosamine, the glycosyl donor used in the biosynthesis of desosaminecontaining natural

products. 18 Thus, strategies were considered to access methyl 2,3anhydro4,6dideoxyα

Dribo hexopyranoside (1.45) on a preparative scale (Figure 1.9).

Figure 1.9 Nucleophilic attack onto the epoxide 1.45

Nu= Dimethylamine, Pyrrolidine,

Piperidine, Morpholine

Me Me Nu O O Nu Desosamine donors O HO 1.45 OMe OMe

Two different approaches were attempted prior to adopting the Richardson and

Crotti procedures for the synthesis of 1.45 from Dglucose.

The first approach involved the Ferrier rearrangement of commercially available triO-acetylDglucal ( 1.51 ) with BF 3 Et 2O in the presence of BnOH to furnish 1.52 quantitatively (Scheme 1.9). 19 Saponification of the C4 and C6 acetates followed by mesylation and reduction with LiAlH 4 yielded 1.53 in 50% over three steps. Epoxidation

of 1.53 with either mCPBA or dimethyldioxirane (DMDO) yielded 1.54 as a 2:1 mixture

of inseparable diasteromers, with the undesired β epoxide being the major isomer. 20

Scheme 1.9 Synthesis of 1.54 from glucal 1.51

OAc OAc 1) NaOMe 2) Mscl, Et3N Me m -CPBA Me BnOH, BF Et O O 3 2 3) LiAlH4, Et2O O DMDO O AcO AcO O AcO OBn Quantitative OBn 50% OBn O β:α = 2:1 1.51 1.52 1.53 1.54

The second approach involved a benzylidene protection of the C4 and C6 hydroxyls followed by benzylation of C2 and C3 hydroxyls of methyl αD glucopyranoside (1.55 ) to furnish 1.56 in 60% (Scheme 1.10). 21 Acidic deprotection by p

TsOH removed benzylidene giving back the C4, C6 hydroxyl groups. While mesylation of the diol and subsequent LiAlH4 reduction was expected to give 1.57 , alcohol 1.58 was obtained 80% yield (2 steps).22

Scheme 1.10 Synthesis of unexpected isomer 1.58

1) PhCH(OMe)2, p-TsOH 1)PTSA, MeOH HO 2) BnBr, NaH 2) MsCl, Et3N Me O O HO Ph O 3) LiAlH4, Et2O O HO O BnO BnO HO X OMe 60% BnO 80% BnO OMe OMe 1.55 1.56 1.57 expected Me HO O BnO BnO OMe

1.58 isolated

With these unsuccessful attempts, recourse was made to the Richardson and Crotti methods. Treatment of 1.55 with sulfuryl chloride in pyridine/chloroform followed by aqueous sodium iodide in methanol and subsequent hydrogenation of dichloride 1.59 with Raney nickel in the presence of potassium hydroxide to afford diol 1.60 in 47%

yield over two steps.23,24 Subjection of diol 1.60 to Mitsunobu conditions furnished 2,3

anhydrosugar 1.45 (Scheme 1.11). 15,25

Aminolysis of 1.45 with aqueous dimethylamine afforded a 6:1 ratio of

chromatographically separable regioisomers (C3/C2) wherein the C3 isomer, methyl

desosaminide ( 1.23), was isolated in 76% yield. 13 Hydrolysis of 1.23 with under standard

acidic conditions followed by basic workup (Amberlyst A26 hydroxide form) delivered

Ddesosamine ( 1.1 ) in 74% yield. The overall yield for the synthesis of 1.1 from 1.55 was

15% over 5 steps.

Scheme 1.11 Synthesis of desosamine starting from glucose 1.55

1) SO Cl , pyr/CHCl OH 2 2 3 Cl Cl Me 2) NaI, H O, MeOH H2, Raney-Ni, KOH O HO O 2 O HO HO HO 55% HO HO HO OMe OMe OMe 1.55 1.59 82% 1.60

6N HCl (aq.) PPh , DEAD 3 Me Me 4 Å MS Me 2 NH (aq.) Amberlyst A-26 O O resin (OH form) Me 2 N 1.1 O HO 74% OMe OMe 60% 1.45 76% 1.61

With ready access to 1.55 , attention was directed at preparing known donors 1.48 and 1.49 . Activation of the anomeric hydroxyl of desosamine under Mitsunobu conditions with tributylphosphine and DEAD in the presence of 2mercaptopyrimidine led to a 7:1 mixture of (β/α) anomers in 64% yield after flash column chromatography

(Scheme 1.12).26 Treatment of alcohol 1.62 with methyl chloroformate in a mixture of

Scheme 1.12 Synthesis of desosamine donors

Me Me PBu3, DEAD, HSPyrm O O N Me2N PhMe Me2N HO OH -40 °C → rt HO S N 64% 1.1 7:1 ( β/α) 1.62

Me ClCO2Me O N Me2N THF/NaHCO (aq.) 3 S N MeO2CO 82% 1.62 7:1 (β/α) 1.48

Me Ac O, Et N 2 3 O N Me2N CH 2 Cl 2 AcO S N 76% 1.49 7:1 (β/α)

THF and aqueous sodium bicarbonate yielded Woodward’s desosamine donor 1.48 in

82% yield. 16,27 Alternatively, acetylation of the C2 hydroxyl under standard conditions

afforded Tatsuta’s desosamine donor 1.49 in 76% yield.17,26

The C3 amino analogs of desosamine, particularly those analogs inaccessible from desosamine derived from natural sources (e.g., erythromycin) can be accessed using intermediate 1.45 . Regioselective ringopening at the C3 position with various secondary

amines like pyrrolidine ( 1.63 ), piperidine ( 1.65 ), and morpholine ( 1.67 ) proceeded in a

highly regioselective manner in alcoholic solvents either at ambient temperature or reflux

to afford exclusively C3 analogs of methyl desosaminide 1.64 , 1.66 , 1.68 in good yields

after chromatography (Table 1). 13, 15

Table 1.1 Synthesis of C3 amino analogs of desosamine

Me Me R NH O 2 O R N EtOH 2 O HO OMe 80 °C OMe 1.45 72 h 1.50

Entry R2NH Product Yield (%)

Me 1 NH O 86 N HO 1.63 1.64 OMe

Me 2 O N NH 83 HO OMe 1.65 1.66

Me O O O 3 N 78 NH HO OMe 1.67 1.68

Accordingly, hydrolysis of these glycosides and transformation into novel 2 thiopyrimidinyl donors via two steps would deliver novel C3 desosamine analogs donors for future study .

CHAPTER 2: Desmethyl Analogs of Telithromycin to Address Antibiotic

Resistance: Synthesis and Biological Evaluation of (-)-4,8,10-Tridesmethyl

Telithromycin

2.1 Background

The word antibiotic originated from the term ‘ antibiosis’, which in Latin means

“against life”. 31 It was first described by Pasteur and Koch in 1877 when an airborne bacillus inhibited the growth of Bacillus anthracis . Later in 1942 Waksman used the term

“antibiotic” to describe microorganisms that antagonize the growth of other microorganisms even under high dilutions. Those substances that kill bacteria

(microorganism or synthetically derived) were excluded from the defintion. 32 Today, the term has come to describe chemical agents under 2000 Daltons that either kill or inhibit the growth of bacteria.

The first antibiotic substance penicillin was discovered in 1928 by a Scottish biologist, Sir Alexander Fleming, which defined new horizons for the discovery of modern antibiotics. 33

“One sometimes finds what one is not looking for.”

(Sir Alexander Fleming, after penicillin discovery)

His serendipitous discovery of penicillin from the fungus penicillium notatum enabled the treatment of bacterial infections such as syphilis, gangrene and tuberculosis.33,34 While experimenting on the influenza virus in 1928, Fleming noted that, Penicillium notatum had destroyed bacteria in a Staphylococcus culture plate. Upon closer scrutiny, he found that the culture had developed a bacteriafree zone that inhibited the growth of

Staphylococci . This newly discovered active substance was effective even when diluted

up to 800 times. 34 He named it penicillin, which later became the first antibiotic. With this discovery, Fleming was awarded Nobel Prize in Physiology or Medicine in 1945 thus revolutionizing the field of antibiotic medical sciences. 33,34 In the 1930s, Bayer AG in

Germany showed that synthetic sulfonamides possessed antibiotic properties. With the discovery and use of sulfonamides and penicillin, the mortality rate associated with bacterial infections especially during and after the era of World War II decreased tremendously. Since then, antibiotics have saved millions of lives by treating the infections caused by the pathogenic bacteria. 34

Many antibiotics have been discovered since the discovery of sulfonamides. Most

of the antibacterial agents are either natural products or potent semisynthetic variants. 35

Different classes of antibiotics evolved through significant contributions from both

Industry and Academia. 34 Modifications of the natural products via decoration,

substitution or degradation led to improved drugs. Sulfonamides (1935), βlactams,

(1940), polyketides (1949), phenylpropanoids (1949), aminoglycosides (1950),

macrolides (1952), glycopepetides (1952), quinolones (1962), streptogramins (2000),

oxazolidinones (2003), lipopeptides (2003) were among the classes of new antibiotics

discovered and used in antimicrobial chemotherapy. 34

By early 1970, there was an abundance of antibiotics present on the market. The early success of antibiotic research and development by the pharmaceutical companies had become commonplace in society. 36 Unfortunately, this translated into a decreased demand for new antibiotics and thus drug development in this area declined. Soon microorganisms evolved and treatment became a challenge with existing antibiotic

therapies. Bacterial resistance was spreading rapidly particularly in hospitals as they work with wide variety of bacterial strains. 37 “If they become resistant to Vancomycin, they will

become resistant to everything. The cycle of resistance is inevitable.” Christopher

Walsh, Harvard Medical School. 37 By 1980, pathogens resistant to one or more

antibiotics began emerging that rendered existing therapies ineffective. 37 As stated before, pharmaceutical companies began curtailing their antibacterial research allowing the pipeline for new antibiotics to run dry. This increased the risk of elderly and immune compromised patients to acquire infections caused by resistant bacteria. This confluence of issues led the Infectious Diseases Society of America (IDSA) to reestablish antibiotic research programs.37 The report entitled “ Bad Bugs, No Drugs” raised a concern to the

US Congress and federal regulatory agencies to step in with financial incentives for

companies and agencies to get back into the antimicrobial business. 37

During this renaissance in antimicrobial drug development, many antibiotics were

discovered through an iterative process wherein structurally related compounds (i.e.,

analogs) were synthesized and introduced to the market with the incremental

improvement in the antibiotic activity relative to the preexisting member(s) of the

class.35 Macrolide antibiotics, a subgroup of polyketide natural products, were the most important class of therapeutic agents that evolved during this period and were used against community acquired therapeutic respiratory infections such as community acquired pneumonia (CAP), acute bacterial exacerbations of chronic bronchitis, acute sinusitis, otitis media and tonsillitis/pharyngitis. Synthetic modifications using semi synthesis of these of macrolide antibiotics led to the discovery of more important classes which were active against resistant pathogens. 38

2.2 Macrolide antibiotics

Macrolide antibiotics such as Erythromycin A, ERY (1.3 ) and their semisynthetic derivatives are polyketidederived natural products (Figure 2.1).39 The term “macrolide” was originally coined by R. B. Woodward in 1957 to abbreviate a class of natural products composed of

Figure 2.1 Macrolide antibiotics with different ring sizes

O Me Me Me N 9 Me 9 Me Me Me Me Me HO OH 11 OH HO OH 12 6 11 OH NMe2 6 12 NMe2 Me HO O O O Me Me HO Et O O O Me 3 Me O O OMe O O OMe Me Me Me Me O OH O OH Me Me Erythromycin A ( 1.3 ) Azithromycin ( 1.6)

14membered ring 15membered ring (semisynthetic)

Me Me O N O Me Me O 8

NMe2 HO MeO O OH O O O Me 4 Me OH Me O OH O Me

Josamycin ( 2.1 )

16membered ring

a macrocyclic lactone with one or more deoxysugars attached. 40 Many naturally occurring macrolides are produced by the bacteria in the actinomycete order and are characterized by a twelve to sixteenmembered macrolactone rings.39

Macrolide antibiotics are used to treat infections caused by Grampositive bacteria such as Streptococcus pneumonia and Haemophilus influenza that affect the respiratory tract and soft tissues. 39 They are common substitutes for patients with penicillin allergy.

Some of the FDA approved macrolide antibiotics are Azithromycin (Zithromax), CLA

(Crixan), Dirithromycin (Dynabac), Erythromycin, Roxithromycin (Xthrocin).

2.3 Erythromycin

Erythromycin A ( 1.3 ) or ERY, is a widely used broad spectrum antibiotic. It is a secondary metabolite produced by soil inhabiting actinomycete bacteria

Saccharopolyspora erythraea.42

Figure 2.2 Structural description of Erythromycin A

Me Me 9 Me Me HO 11 OH 12 OH 6 NMe2 Me HO Desosamine O O O Me 3 Me O O OMe Me Me Cladinose O OH Me Erythromycin A ( 1.3 )

ERY was isolated in 1952 by J. M. Mc Guire and coworkers at Eli Lilly from soil

collected in the Philippines. 41 That same year it was introduced to the market. ERY is a

14memebred lactone with two sugars, cladinose and desosamine, attached at C3 and C 21

5 positions, respectively (Figure 2.2).44 The first complete structural elucidation of 1.3 was done by Wiley and coworkers in 1957 by using degradation methods. 40 The

structural assignment was confirmed by Harris and coworkers in 1965 when they

45 reported the xray structure of 1.3 . ERY and its derivatives are slightly basic (p Ka = 8.8) by the virtue of the dimethylamino group which enables purification via acid and base

treatment. ERY solubility in water is 2 mg/mL. 44 The robust lactone ring is capable of

withstanding many synthetic transformations. For example, it is resistant to nucleophilic

reactions due to the steric hindrance around the C1 carbonyl group. Reactivity of the five

hydroxyl groups varies due to steric, neighboring groups and the conformations of the

molecule. In acetylation reactions, the C2ˈ hydroxyl group of desosamine is most

reactive, followed by the C4ˈˈ of cladinose. These differences in reactivity enable

selective transformations for semisynthetic modifications. 44

2.4 Spectrum of Activity

ERY inhibits the growth of bacteria by blocking bacterial protein synthesis. An x ray crystal structure of a ribosomeerythromycin complex revealed that ERY binds to the

50S ribosomal subunit and consequently blocks protein translation and the presence of the desosamine is a key to the antibacterial activity. The mode of action is described in more detail in section 2.7.46 It is used to treat infections of the respiratory tract, skin, soft

tissues and urogenital tract. It is mainly active against Grampositive pathogens such as

macrolidesusceptible S.aureus , S. pneumonia, and S. pyogenes .44 However, use of erythromycin became problematic when several of ERY resistant pathogens S. pneumonia, and S. pyogenes were isolated. The spectrum of activity is not as broad as 22

compared to other classes such as penicillins, cephalosporins, quniolones and tetracyclines. 44

2.5 Drawbacks

Since its discovery, ERY suffered poor bioavailability and acidic stability. 39 This has a major impact on its halflife and oral activity, thus requiring multiple does per day. 44 ERY degrades in acidic conditions found in the stomach and produces inactive by

Scheme 2.1 Degradation of ERY in acidic medium

O OH

Me Me Me Me 9 9 Me Me Me Me HO 11 OH O OH 6 A HO 11 12 NMe 12 OH 6 2 NMe2 Me HO O Me Me HO O O O O O Me 3 3 Me Me O O OMe O O OMe Me Me Me Me OH O O OH 1.3 Me 2.2 Me

B Me Me 9 Me Me OH O HO 11 12 OH 6 Me Me NMe2 Me HO MeHO Me O O O Me O OH 3 NMe Me 2 O O OMe 12 Me 6 HO O O O Me Me Me Me 3 O OH O O OMe 2.4 Me Me Me O OH 2.3 Me

A= hemiketal C6 OH and C9 Keto: B= hemiketal C12 OH and C9 Keto

products which causes gastrointestinal side effects. This degradation involves sequential reaction of the C6 and C12 hydroxyl groups and the C9 ketone, forming hemiacetals and later enolethers that are no longer bioactive.39

2.6 Second Generation Macrolide Antibiotics

Modifications to the macrolactone of ERY were made to address issues of acidic instability. Key modifications were done to the reacting functional groups at C6 and C

12 hydroxyls and the C9 ketone functionalities. 39 Methylation of the C6 hydroxyl was

successfully done by a group of researchers at the Japanese drug company Taisho

Pharmaceuticals. 47 It was difficult to alkylate the C6 hydroxyl selectively in the presence of other hydroxyl groups. Analog 6Omethyl erythromycin A was named

Clarithromycin, CLA ( 1.4 ) and launched as a drug called Clarith in Japanese market in

1991 (Figure 2.3). 47,44 CLA is acid stable and orally active as it tolerates the acidic

Figure 2.3 Structure of Clarithromycin

O Me Me 9 Me Me HO 11 OMe 12 OH 6 NMe2 Me HO O O O Me 3 Me O O OMe

Me Me O OH Me Clarithromycin ( 1.4 ) environment of the stomach. By 1985, Abbott laboratories partnered with Taisho and obtained the international rights. In 1991, it was FDA approved and was launched in the

US market as Biaxin. 47 CLA is synthesized from ERY in six steps. CLA displays better

activity against Mycoplasma pneumoniae and Chlamydia trachomatis, in addition to

improved pharmacokinetic profiles over ERY. Additionally, CLA exhibited good activity

against Helicobacter pylori and is used for the treatment of peptic ulcer disease. 44

The synthesis of CLA ( 1.4 ) began with converting the C9 keto of ERY to an oxime (Scheme 2.2). 48 Protection of both C2ˈ and the C4ˈˈ hydroxyls as TMS ethers afforded 2.5 , which was then treated with MeI in DMSO/THF mixture to give C6 O methylation along with other products. Subsequent removal of the protecting groups yielded CLA.

Scheme 2.2 Synthesis of CLA

O Cl O N

Me Me Me Me 9 9 Me Me Me Me HO 11 OH HO 11 OH 12 OH 6 12 OH 6 NMe2 NMe2 1) H2NOCH2PhCl, Py TMSO Me HO 2) TMSCl, Imidazole Me O O O Me O O O Me 3 3 Me Me O O OMe O O OMe Me Me Me Me 1.3 O OH 2.5 O OTMS Me Me 3) MeI, DMSO/THF 4) H2/Pd -C, NH4COOH, 5) HCOOH 6) NaHSO3

1.4

Inspired by the biological activity of CLA, many scientists worked on introduction of various alkyl groups at the C6 hydroxyl position. Modification of the C9 keto was done by Djokic and coworkers at Pliva Pharmaceuticals (Croatia). They were able to employ the Beckmann rearrangement regiospecifically onto the aglycone of the 14macrolide and successfully introduced a nitrogen into the ring making a 15membered macrolactone. 49

This led to the discovery of Azithromycin (AZY) (Figure 2.4). In 1986, Pfizer 25

collaborated with Pliva, which gave Pfizer exclusive rights to the sale of AZY in Western

Europe and the U.S. Pfizer launched AZY under the brand name of Zithromax in 1991.50

AZY was significantly more potent than ERY and CLA against gramnegative pathogens

H. influenza . It is acid stable, orally active and is readily absorbed in the stomach. 50

Figure 2.4 Structure of Azithromycin

Me N Me 9 Me

Me Me HO OH 11 OH 6 12 NMe2 Me HO Et O O O Me

O O OMe

Me Me O OH Me Azithromycin ( 1.5 )

Synthesis of AZY started with converting the C9 keto of ERY was to an oxime 2.5 using

hydroxylamine hydrochloride (Scheme 2.3). Treatment of 2.6 with TsCl and pyridine

Scheme 2.3 Synthesis of AZY

OH O N Me Me Me Me 9 9 Me Me Me Me Ts-Cl, Py HO 11 OH NH2OH.HCl, Py HO 11 OH 12 OH 6 12 OH 6 NMe2 NMe2 -TsOH Me HO Me HO O O O O Me O O Me 3 3 Me Me O O OMe O O OMe Me Me Me Me OH O OH O 1.3 Me 2.6 Me

Me HN Me N Me Me 9 9 Me O Me Me HO 11 HO OH HCOOH 12 OH 6 Pt/H 11 OH Me NMe 2 6 HCHO 2 12 NMe2 Me HO 1.5 O Me Me HO O O Et O O O Me 3 Me O O OMe O O OMe Me Me Me Me OH O O OH Me Me 2.7 2.8 26

effected the Beckmann rearrangement where the intermediate nitrilium ion was trapped by the C6 hydroxyl. The iminoether 2.7 was reduced under high pressure in presence of

Pt catalyst to furnish an intermediate amine 2.8 which was methylated under Eschweiler

Clarke conditions to afford AZY (1.5 ).

Other important structural modifications that evolved as drugs are roxithromycin

(2.9) and dirithromycin (2.10 ) (Figure 2.5). 51

Figure 2.5 Structures of Roxithromycin and Dirithromycin

O O O N OMe N OMe Me Me Me Me O 9 Me Me Me Me HO 11 OMe 12 6 HO OMe NMe2 11 OH 12 6 NMe Me HO 2 O Me Me HO O O O O O Me 3 Me 3 Me O O OMe O O OMe Me Me Me Me O OH O OH Me Me Roxithromycin ( 2.9) Dirithromycin ( 2.10 )

Second generation macrolides overcame many issues plaguing EM, but the

development of resistance to antibiotics is a constant, unending struggle. Many infectious

diseases have been brought under control, yet newer bacteria resistant to existing

therapies keep evolving.35 The ability of pathogens to grow despite the presence of antibiotics, through the development of antibiotic resistance, has rendered victims as vulnerable as patients from the preantibiotic era. The development of resistance is inevitable following the introduction of a new antibiotic. However modern uses of antibiotics have caused a huge increase in the number of resistant bacteria. In fact, within eight to twelve years of widespread use strains resistant to multiple drugs have emerged.35

All of these led to the critical question: How do bacteria become resistant to antibiotics and what are the biochemical mechanisms that they use? Several mechanisms have been developed by bacteria in order to deal with antibiotics but all require either the modification of existing genetic material or the acquisition of new genetic material. An understanding of the mechanisms employed by bacteria to evade antibiotics is the first step toward addressing this inevitable problem.52

2.7 Mechanism of Action

Protein synthesis or translation is a multistep process involving various biochemical processes in the cell. Codonanticodon pairings on ribosome through tRNA and mRNA results in the formation of amino acids. The incoming tRNA with the amino acid enters a site on the ribosome termed the A (Acceptor) site. Adjacent to the A site is the P (peptidyl) site, where the tRNA has been attached to the growing peptide chain.

During the process of protein synthesis, the peptide chain on the P site of tRNA is transferred to the amino acid on the A site of tRNA, in a reaction termed peptidyl transfer. The ribosome translates down the mRNA, and in the process, the tRNA in the A site is moved into the P site. The empty tRNA that was previously in the P site moves into the A site and this process is repeated until protein synthesis is complete. 44, 53

The structural differences in ribosomes of bacteria, archaea and eukaryotes allow

macrolide antibiotics to selectively bind these ribosomes while leaving eukaryotic

ribosomes unaffected. 54 Prokaryotes have 70S ribosomes each made of larger 50S and smaller 30S subunits. The 50S subunit is composed of a 5S RNA subunit, a 23S RNA subunit and 34 proteins. 54 High resolution structure of the 50S subunit using xray

crystallography was used to understand the mechanisms of these macrolides. 44 This data

not only corroborated the prior experimental details but offered new insights into the

ribosome function, antibiotic action and resistance. Macrolides enter into the cell by a passive diffusion across the bacterial cell membrane and bind reversibly with high

affinity. They inhibit bacterial protein biosynthesis by binding to the peptidyl transferase

center and blocking the exit tunnel that channels nascent peptides, preventing synthesis

(Figure 2.6). 55

Figure 2.6 Structure of macrolide bound to the 50s ribosomal subunit of Hma

The figure shows the crosssection of 50S subunit, peptidyl transfer center, the macrolide binding site and the peptide exit tunnel. The details of macrolide antibiotics interactions

with the ribosome have been clarified by the solution of the high resolution 50S subunit structure of the ribosome by the Steitz group and the Yonath group. 55,56 The Nobel Prize

in Chemistry 2009 was awarded jointly to Venkatraman Ramakrishnan, Thomas A. Steitz

and Ada E. Yonath "for studies of the structure and function of the ribosome".

Crystal structures of the macrolide bound to the 50S subunits of halophilic

archeon H.marismortui and eubacterial D.radiodurans have been solved. 44 There are

several differences in the two bacterial species used in the studies; for example the

Haloarcula ribosome has a guanine at the position equivalent to 2058, which is an

adenine that makes a key interaction in the macrolidesusceptible strains. H.marismortui

(Hma) is not susceptible to macrolide inhibition at concentrations used clinically. In contrast, D.radiodurans (Dra) is a eubacterium with the 50S rRNA residues identical to those found in pathogens, and is susceptible to erythromycin. 44,55,56 From both (structures described in section 2.9) it was concluded that the 14membered ring macrolides such as

EM, CLA and Telithromycin (a third generation ketolide antibiotic section 2.9) bind largely to the nucleotides in domain V of the 23S rRNA. 44 In 2000, the Steitz group at

Yale solved the macrolide bound crystal structure of the 50S ribosomal subunit of Hma at

2.4 Å resolution, allowing atomic level details of ribosomal architecture. 57 In 2001, the

Yonath group and the MaxPlankInstitute obtained crystal structures of macrolides bound the same 50S subunit of Dra at 3.4 Å resolution. 58 The Yonath structure

highlighted the important hydrogen bonding interactions among the desosamine C

2ˈhydroxyl group with adenine 2058 and adenine 2059 equivalents. 58 The Steitz group later in 2002 published crystal structures confirming certain key binding sites in common with the Yonath group. 55 Three of the hydroxyl groups on the sites in common with the

Yonath group. 55 Three of the hydroxyl groups on the macrolactone ring C6, C11 and C

12 have hydrogen bonding with the nucleotides of the 23S rRNA. In the case of

telithromycin, the arylalkyl groups that extended from the cyclic C11, 12 carbamate are believed to make additional contacts with the ribosome, strengthening the compound

interaction with the binding site. 55 The Steitz structure showed that erythromycin and telithromycin bind with the same conformation and in the same location within the ribosome. In addition, they showed hydrophobic interactions between the lactone ring and the tunnel wall to promote binding (Figure 2.7).

Figure 2.7 ERY and TEL bound to 50s subunit of Hma (pdb:1YI2 and 1YIJ)

N O N N ( )4 O Me Me N 9 Me O 11 OMe 12 6 Me NMe2 HO Et O O O Me 3 Me O O

Telithromycin ( 1.6 ) TEL

One face of the macrolactone ring is relatively hydrophobic and that face is believed to

make van der Waals contacts with hydrophobic residues lining the tunnel wall. These

structures confirmed the data of Yonath with respect to the location of the binding site,

though some differences were observed in the conformations of the macrolactones. 56,59

Along with the higher resolution crystal structure, Steitz’s data correlates better with previous NMR, xray, genetic and chemical footprinting studies. 60 The C2ˈOH of the

desosamine is hydrogen bonded to the N1 of the 23S rRNA reside A2099Hm (Figure 2.7 from pdb: 1YI2 and 1YIJ, respectively and A2099Hm corresponds to A2058Ec).

Telithromycin has an additional point of contact with the C2644Hm through its side chain, which has been suggested to be responsible for its tenfold higher binding affinity compared to 1.3 and also explains its enhanced activity against resistant strains.

2.8 Mechanism of antibiotic resistance

There are four different classes of antibiotics with overlapping binding sites in the pepitdyl tranferase region of the 23S rRNA. They are Macrolide (M), Lincosamide (L), streptogramin B (S B), and ketolides (K) and are abbreviated as MLS BK antibiotics. Over time, several bacterial microorganisms were isolated, which were able to survive even when exposed to these MLS BK antibiotics. The mechanisms by which bacteria developed

Figure 2.8

A cartoon showing these mechanisms is presented in Figure 2.8 34

61 resistance against these MLS BK antibiotics falls under three different categories.

1) Target mutation and modification (via methylation) that prevents the binding site of the antibiotic to its natural cellular targets

2) Efflux of the antibiotic or alteration in the permeability barrier as a means of protection by means of protein pump

3) Inactivation of the antimicrobial substance by various enzymes.

2.8.1 Ribosome Mutation and Modification

Macrolide resistance due to ribosomal alteration or mutations in domain V of 23S

rRNA or the ribosomal proteins L4 or L22 were isolated providing genetic evidence that

these antibiotics failed to bind to these ribosomes. 62 Initially, A2058G was identified as

conferring erythromycin resistance in yeast mitochondria. Since then, there have been a plethora of strains identified with mutations in either A2058 or A2059 that confer MLS B or ML resistance respectively. Many clinical isolates of S. pneumonia, Mycobacterium,

Brachspira, Helicobacter, Treponema, with an A2058 or an A2059 changed to G, U and

C were found. Mutations in the ribosomal protein L4 or L22 may alter the tertiary

structure of 23S rRNA at domain V and indirectly affect macrolide binding.58

2.8.2 Ribosomal Methylation

NMonomethylation or N,N dimethylation of the 6amino group on adenine at positions 2058 by ribosomal methylases encoded by erm (erythromycin ribosome

methylase) genes blocks the binding of MLS B antibiotics and confers resistance and are

63 called MLS B phenotypes. They are found to be encoded by a variety of erm genes. In

addition to being the first recognized mechanism of resistance to erythromycin in

pathogenic strains, erm methylases are the most widespread mechanisms to MLS B antibiotics. 61 The level of resistance conferred by ribosomal methylases to specific macrolides depends on the mode of methylation of the adenine residue and on the macrolide structure. Phenotypes MLS BI and MLS BII are the two different types

depending on the monomethylation or dimethylation of the adenine residue. 64 A wide range of microorganisms including grampositive species, gramnegative bacteria, spirochetes, anaerobes, Streptomyces and Saccharopolyspora express erm methylases. 61

2.8.3 Efflux of Macrolides

It was presumed that drug efflux occurred due to the low permeability of high molecular weight hydrophobic molecules through the outer membrane of Gramnegative bacteria. 65 Later it was realized that certain chromosomally encoded pumps play an important role in the drug efflux. In all cases, a protein inside the cytoplasmic membrane acts alone or in concert with other proteins to pump the macrolide out of the cell or the cell membrane. 66

2.8.4 Inactivating Enzymes

Certain enzymes like esterases, phosphotransferases, glycosyl transferase, decylases, and formyl reductases have been identified to inactivate the MLS B antibiotics at different active sites. Esterases act on the C1 position, while Phosphorylase or Glycosylase acts onto the C2ˈ of desosamine. 61,67 Clinically, the most important mechanisms of resistance

are due to e rm methylase and ribosomal modification. Research to address different

resistant phenotypes will continue to play an important role in defining the structure activity relationships of novel macrolides.

Figure 2.9 Enzyme inactivation of macrolide

O Me Me Phosphorylase 9 or Glycosylase Me Me HO 11 OH 12 OH 6 NMe2 Me HO O O O Me 3 Me O O OMe Me Me 1.3 O OH Me Esterase

2.9 Ketolides and Discovery of Telithromycin

Ketolides evolved as an effort to overcome ERY resistant bacteria. They are semisynthetic derivatives of ERY having a 3keto function. The name ketolide is derived from keto (3keto group) and olide (lactone). 52 Macrolides like narbomycin ( 2.11), pikromycin ( 1.2 ) and 3hydroxy erythromycin A ( 2.12) analogs were isolated in the early

1970ˈs and were presumed biologically inactive. 52,68

Figure 2.10 Ketolides and C3 hydroxy erythromycin A

O O Me Me Me Me Me Me Me HO OH R OH NMe2 NMe2 Me HO Me HO O Me O O O Me O O Me Me O O O OH Me Me R= OH, Pikromycin ( 1.2 ) 3hydroxy erythromycin A ( 2.12) R= H, Narbomycin ( 2.11)

It was reported that chemical modification by removal of cladinose at C3 was able to

69 increase or suppress the MLS B resistance within the macrolide class.

Table 2.1 MIC data for ketolide Narbomycin

Compound S.aureus S.aureus S.aureus S.pneumoniae S.pneumoniae 011UC4 Ery Ri EryRc EryRc Ery Ri 011GO25i 011CB20 030SJ1 030SJ5i

Narbomycin 1.25 2.5 >40.0 10.0 20.0

ERY 0.3 >40.0 >40.0 >40.0 >40.0

EryS=erythromycin A susceptible, EryRc= constitutively erythromycin A resistant, EryRi= inducibly erythromycin A resistant

This data was ignored until narbomycin was tested against some ERY resistant, gram positive cocci. It showed that narbomycin displayed a weak but significant in vitro

antibacterial activity. These results provide a starting point for the synthesis of newer

agents addressing the ERY resistant strains. 52

The first successful ketolide, 6Omethyl3ketoerythromycin A ( 2.13 ), was

synthesized from CLA ( 1.4 ) in four steps. Acidic removal of cladinose followed by an

acetate protection of the C2ˈ hydroxyl of desosamine gave 2.12 . A modified Pfitzner

Moffat procedure was employed to oxidize the C3OH and subsequent removal of

acetate on C2ˈ gave 2.13 .70 The compound 2.13 was as active as ERY and exhibited

moderate to good activity against ERY–resistant strains of Staphylococcus aureus ,

Staphylococus epidermidis and Streptococcus pneumoniae (Table 2.2). 70

Scheme 2.4 Synthesis of ketolide from CLA

O O Me Me Me Me 9 9

Me Me 1) HCl/H2O Me Me HO OMe 2) Ac O/K CO 11 OH 2 2 3 HO 11 OMe 12 6 12 OH 6 NMe2 NMe2 Me HO O Me AcO O O Me 55% O O O Me 3 3 Me Me O O OMe O OH Me Me Me O OH 1.4 Me 2.12 O Me Me 1) EDC, HCl 9 DMSO,PyCOCF 3 Me Me 2)MeOH HO 11 OMe 12 OH 6 NMe2 70% Me HO O O O Me 3 Me O O Me

2.13

Table 2.2 MIC data for ketolide 2.13

Compound S.aureus S.aureus S.epider S.pneumoniae S.pneumoniae 011UC4 Ery Ri midis Ery Rc Ery Ri 011GO25i 012GO11i 011CB20 030SJ5i

2.13 0.3 10.0 5.0 10.0 20.0

ERY 0.3 >40.0 >40.0 >40.0 >40.0

EryS=erythromycin A susceptible, EryRc= constitutively erythromycin A resistant, EryRi= inducibly erythromycin A resistant

With the rediscovery of the ketolides, a new generation of macrolides evolved, which

were termed the third generation of macrolide antibiotics. Furthermore, it was shown that

cladinose was responsible for inducing macrolide efflux. These results subsequently

attracted immense interest in ketolide research and many structural modifications were

performed on the erythromycin scaffold with the C3 keto functionality. Among these modifications, some of the results of SAR studies, suggested that the 11, 12carbamate ketolides possess better antibiotic activities than the ketolide itself. Synthesis of the 11,

12 carbamate ketolides was carried out in three steps from 6Omethyl3ketoERY. 70,71

The synthetic scheme employed for preparing the ketolides is shown in Scheme 2.5. The

C2ˈhydroxyl group of 2.13 was protected with acetate to give 2.14 . Mesylation of the C

11 hydroxyl group and subsequent elimination by DBU afforded enone 2.16 . The C12 hydroxyl group was then activated under NaH and carbonyl dimidazole (CDI) conditions to convert it into acyl imidazole 2.17. This acyl imdazole,

Scheme 2.5 Synthesis of C11, 12 Oxazolidinones

O O Me Me Me Me 9 9 Me Me Me Me HO OMe HO 11 OMe (MeSO2)2O, Py 11 OMs DBU 12 OH 6 12 6 NMe NMe2 2 Me AcO Me AcO O Me O O O Me O O 3 3 Me Me O O O O Me Me 2.14 2.15

O O Me Me Me Me 9 O 9 Me Me Me N O HO OMe N OMe 12 6 CDI, NaH 12 6 NMe2 Me NMe2 Me AcO Me AcO O O O Me O O O Me 3 3 Me Me O O O O Me Me 2.16 2.17 O O Me Me 9 1) NH 3 NH Me O OMe 2) MeOH 12 6 Me NMe2 Me HO O O O Me 3 Me O O

Me 2.18

O O R Me Me 9 1) RNH2 N Me 2) MeOH O OMe 12 6 2.17 Me NMe2 Me HO O O O Me 3 Me O O

Me 2.19 when treated with liquid ammonia, underwent transamination followed by an intramolecular azaMichael reaction to afford oxazolidinone the C11, 12 bond 2.18. This procedure was employed to introduce various Nsubstituted alkyl amines 2.19 .70,71

Structureactivity relationship (SAR) studies were conducted in this manner by varying

Scheme 2.6 Synthesis of Telithromycin

N 1) O O N N N ( )4 Me Me O Me Me O 9 N N 9 Me N NH2 Me N O 4 O N OMe 11 OMe 12 6 12 6 Me NMe2 Me NMe2 Me AcO HO O O O Me Et O O O Me 2) MeOH Me 3 3 Me 40% O O O O Me Me

2.17 Telithromycin (1.6)

the 'R' group to optimize biological activity. Various alkyl substitutions on the nitrogen of the carbamate were screened (Table 2.4). 72 These compounds were tested against the

E.coli, ERY resistant S.aureus 011CB20 (MLS B constitutive type), grampositive cocci

H. influenzae strains. The introduction of the alkyl aryl side chain showed a dramatic

increase in the antibacterial activity with the resistant strains. Varying the alkyl chain

length and introduction of nitrogen atoms in the aryl ring were the most important

discoveries through various trials among the SAR (A2 to A5 analogs from the Table 2.4).

The introduction of an imidazolopyridyl group and a four carbon alkyl chain led to a 39

Table 2.3 MIC data of Oxazolidinones with various side chains including TEL

S.a: Staphylococcus aureus; S.e: Staphylococcus epidermidis; S.p: Streptococcus pneumonia; S.pyo:Streptococcus pyogenes; H.i: Hameophilus influenza ; EryS=erythromycin A susceptible, EryRc= constitutively erythromycin A resistant, EryRi= inducibly erythromycin A resistant

dramatic increase of activity and turned out to be the most active compound in the series

(Scheme 2.6). This molecule, (HMR 3647) telithromycin (TEL) was four times more active than CLA and was more active than AZY in most mutant strains. 70,71,72 Analogs of

TEL were made via chemical modifications at C2 and C3 positions. The presence of a

βketo functionality helped in the introduction of nucleophiles at C2 position 2.20 , 2.21 ,

2.22. Chemical modifications enabled the introduction of a C2, C3 olefin in TEL 2.23

(Figure 2.11).

Figure 2.11 Key analogs of TEL

N N O O N N N ( ) N Me 4 Me ( )4 O O Me Me N 9 N 9 Me Me O O 11 OMe 11 OMe 12 6 NMe 12 6 Me 2 Me NMe2 HO O HO Et O O Me Et O O O Me Me 3 3 Me O O O O Me Cl Me F

2.20 N 2.21 O N N ( )4 O Me Me N 9 Me O 11 OMe 12 6 Me NMe2 HO Et O O O Me 3 Me O O Me 1.6 N O N N N ( ) Me 4 Me O O N N 9 N ( ) Me Me 4 Me O O 11 OMe N 9 12 6 NMe Me Me 2 O HO 11 OMe 12 6 Et O O O Me Me NMe2 3 Me HO Et O O O Me O O 3 Me Me Me O O Me 2.22 2.23 O

All these analogs were tested both in vitro and in vivo . The biological data suggested that introduction of fluorine at C2 2.21 helped in improving the biological activity. 73

2.10 Third Generation Macrolide Antibiotics

Telithromycin TEL, a C11, 12 carbamate ketolide that is characterized by the butyl imidazolyl pyridyl side chain substituting the carbamate residue is one of the third

generation ketolide. In 2001, FDA released TEL under the brand name Ketek. It was used for the treatment of mild to moderate respiratory infections, acute

Figure 2.12 Ketolide antibiotics

O Acid stability Me Me O 9 and address NR' Me MLSB O 11 OR resistance 12 6 Me NMe2 5 HO 4 O Me Address MLSB O O Me 1 3 resistance Me additional binding O O biaryls Me Address resistance Ketolides due to efflux

R = Me or -CH2CHCHAr R' = -(CH2)4Ar or H 2.24 bacterial sinusitis, and chronic bronchitis. 74 In short, third generation ketolides with key substitutions onto the macrolactone were successful in addressing shortcomings of the first two generations (Figure 2.12).

2.11 Present Study: Desmethylation as a Strategy for Overcoming Antibiotic

Resistance

There are nearly 200 marketed antibacterial drugs with a cost factor of about $

800 million. The average time to bring a new drug to market is near roughly eight to ten years. 75 Natural products are good chemical leads and often their synthetic modifications lead to better candidates. Cragg and Newman have shown that over one half of all drugs are derived, inspired or modeled on natural products. 75 There has been a general trend in

Pharmaceutical R&D from acute infectious diseases (shortcourse therapy) to more

profitable chronic illnesses (longterm treatment). Thus greater investments are done in areas like hyperlipidaemia, hypertension, dementia, mood

Figure 2.13 Graph showing number of new antibiotics

New Antibiotics

disorders, pain, asthma, rheumatoid arthritis, or obesity.76 At the same time investment in antibacterial discovery and development is decreasing at large pharmaceutical companies such as Abbott, Aventis, BristolMyers Squibb, Eli Lilly, GlaxoSmithKline, Proctor &

Gamble, HoffmannLa Roche, and Pfizer. Several adverse factors have played a role in weakening this essential therapeutic area. Development of resistance and dynamics of the pharmaceutical market, increasing fragmentation of the market, recent patent expiration of blockbuster drugs, and the growing regulatory hurdles for the clinical evaluation of new antibiotics play a significant role. 37,77,79 As a result of these risks, large companies

are forced to focus on safe broad spectrum antibacterial drugs for extensive use. The

number of antibacterial approved drugs by the US Food and Drug Administration (FDA)

decreased by more than half over the last two decades (Figure 2.13) and only 6 of 506

“new molecular entities” in development were antibacterial agents. 79 There was a big

decrease in the approval of new antibacterial drugs from the period of 19931997 to

20032005.

Thus, there is always a demand for novel antibacterial drugs as more untreatable pathogens develop over time. With this long term goal in mind, we initiated a structure based drug discovery program focused on the development of new antibiotics. In addition, we sought to employ the concept of natural product structural simplification to third generation ketolide antibiotics to address antibiotic resistance. Our approach will determine the functions of the methyl groups present at the C4, C8 and C10 position of the ketolides. These structural modifications were proposed based on a hypothesis put forth by Steitz and coworkers after obtaining crystal structures of macrolides ERY and

AZY bound to the 50S ribosomal subunits of H.marismortui. The structures of 50S subunits with the macrolide bound to H.marismortui were solved during the period 2001

2004 at different resolutions. 80 Steitz worked with H.marismortui (Hma) , which is a

halophilic red archaeon found in the Dead Sea that thrives in an extreme environment. 81

It was important to understand how, Steitz and coworkers interpreted the structural aspects of the macrolide based on these crystal structures.

2.12 Steitz’s Explanation of Antibiotic Resistance from Structural Data

Macrolides ERY and TEL do not bind to wildtype Hma which possesses a G residue at

2058. Subsequently when the G2058 was modified genetically to an adenine A, the macrolide was susceptible. 82 It was then cocrystallized and the crystal structure was

resolved. It showed the 14membered macrolactones bind to nucleotides in domain V of

the 23s rRNA in the ribosomal peptide exit tunnel about 1015 Å from the peptidyl

transferase site. 55 The C2ˈ hydroxyl of desosamine shows hydrogen bonding interactions with the adenine at A2058Ec (A2099Hm). 56 Hydrophobic interactions promote the

Figure 2.14 Selected distances of the C4 methyl and proposed steric clash

binding between the lactone ring and the tunnel wall of the ribosome. One face of the

macrolactone ring is relatively hydrophobic and the other face is hydrophilic. The

desosamine ring is perpendicular to the plane of the macrolactone ring. The orientation at

the binding site was similar for both ERY and TEL. 58,82 Inspection of the structure reveals that the C2 atom of A2058 (2099Hm) is at a distance of 3.7 Å from the C4 methyl group (Figure 2.14). The structure of guanine has an amino group at the C2 position which engages in a steric clash. This big amino group causes a steric clash with the C4 methyl group of the lactone ring (within van der Waal radii of 2.7Å), thus providing a structural rationale for the resistance of the A2058G mutation. It was also proposed that the N,Nˈ dimethylation of A2058 also results in a steric clash with the C4 methyl group. 56,59,82

Figure 2.15 Additional binding of the biaryl side chain

It was observed in the case of TEL that modest activity is maintained against some resistant strains. This was rationalized by additional contacts made due to the presence of the biaryl side chains present in the ketolide scaffold. Figure 2.15 shows the biaryl interacting with nucleotides C2644 and U2645. These interactions include dipole dipole (heterocyclic ring and C2644) and hydrogen bonding (C2644, C2ˈOH and the pyridine ring). 56,59,82

2.13 Desmethylation Strategy and Proposed Desmethyl Analogs of Telithromycin

We hypothesized that removing the C4 methyl group from the macrolactone ring would avoid the steric clash with the C2 amino group of guanine. The resulting

"desmethylation strategy" if successful would represent a novel approach toward addressing antibiotic resistance arising from target (i.e., ribosomal) modification. This concept is illustrated below (Figure 2.16). Macrolides with C4 methyl group bind to ribosomes with adenine at 2058 (A2058) but do not bind to 2058 mutants with guanine

(Figures A and B). Proposed work of our project and my thesis involves the synthesis and

biological evaluation of C4 desmethyl ketolides of TEL which were predicted to bind with wild types and mutant bacterial strains which involved the A2058G mutation.

Figure 2.16 C4 desmethylation to address antibiotic resistance

Though there is likely a loss in hydrogen bonding of the C2ˈhydroxyl of

desosamine when A is mutated to G, we predict that the ionic interactions with the phosphate residues and the protonated dimethyl amine of desosamine coupled with the

C4 desmethylation should address antibiotic resistance caused by point mutation and bind to the mutant ribosome. This desmethylation hypothesis, coupled with the concept

of structural simplification and molecular editing, led us to propose simplified desmethyl

ketolides analogs at C8, C10 along with the C4. These analogs would not only address

the steric clash, but also enable us to understand the biological significance of these

methyl groups. This approach of synthesizing structurally simplified analogs was well precedent in the literature where simplified structures of important natural products and

their synthetic variants rendered better candidates. 83 The discovery of ketolides resulting from erythromycin modification can also be considered as example of structural simplification . The scope of structural simplification via desmethylation was well 47

demonstrated by Wender and coworkers with bryostatin and Smith and coworkers with

(+)discodermolide. 84,85

Figure 2.17 Wenders bryostatin analog

Me Me HO H OAc MeO2C O O OO O Structural Simplification O O OH OH HO HO Me O O Me O O Me Me O Me OH O R OH

Me O CO2Me Me O CO2Me

Bryostatin 1 ( 2.25 ) 2.26 : R=Me (K i= 3.0 nM) (K i= 1.35 nM) 2.27 : R=H (K i= 0.25 nM)

With this rationale, a variety of simplified analogs of bryostatin 1 ( 9) were prepared (Figure 2.17). Bryostatin 1 ( 2.25 ) is an important cancer chemotherapeutic

agent. The simplified scaffold 2.26 and 2.27 were prepared, where 2.27 a desmethylated

analog proved to more potent than bryostatin ( 2.25 ).84

Similarly, (+)discodermolide ( 2.28 ) analogs were prepared by Smith and co workers. These simplified analogs 2.29 and 2.30 (Figure 2.18) where removal of the C14

methyl group results in slightly less potent analog of 2.28 , whereas dehydration of the C

2,3 bond gave 2.30 with increased potency. 85

We came to synthesize four analogs of TEL lacking the C4 methyl group (Figure

2.18). Our structure simplification helps not only in accessing the analogs in a timely fashion, but also, and importantly addresses bacterial resistance. The analogs proposed are 4,8,10tridesmethyl telithromycin (2.31 ), 4,10didesmethyl telithromycin ( 2.32 ),

Figure 2.18 Discoderomolide analogs by Smith

Me Me Me Me Me Me Me Me Me Me Me

22 22 22 16 14 16 14 16 14 O O OH OH O O OH OH O O OH OH Me Me Me 14-normethyl 2,3-anhydro NH2 NH2 NH2 Me Me Me

HO 8 HO 8 HO 8 Me Me Me HO HO 3 3 2 O 2 O O Me Me Me O O O (+)14normethyldiscodermolide (+)discodermolide (2.28) (+)2,3anhydrodiscodermolide (2.30) (2.29) IC50 IC50 IC50 A549: 22 nM A549: 8.6 nM A549: 50 nM MCF7: 28 nM MCF7: 5.6 nM MCF7: 46 nM SKOV3: 21 nM SKOV3: 3.4 nM SKOV3: 35 nM

4,8tridesmethyl telithromycin ( 2.33 ) and 4desmethyl telithromycin ( 2.34 ). These

proposed analogs were rank ordered based on the increasing order of their synthetic

Figure 2.19 Desmethyl Telithromycin analogs

N N O O N N N N ( )4 ( )4 O O Me N 9 N 9 Me Me O O 11 OMe 11 OMe 12 6 12 6 Me NMe2 Me NMe2 HO HO Et O O O Me Et O O O Me 3 3 O O O O

Me Me 4,8,10tridesmethyl telithromycin ( 2.31 ) 4,10didesmethyl telithromycin ( 2.32 )

N N O O N N N N ( ) ( )4 Me 4 Me O Me O N 9 N 9 Me Me O O 11 OMe 11 OMe 12 6 12 6 NMe Me NMe2 Me 2 HO HO O Et O O O Me Et O O Me 3 3 O O O O Me Me

4,8didesmethyl telithromycin ( 2.33 ) 4desmethyl telithromycin ( 2.34 ) 49

complexity. With this assumption we started the synthesis of the simplest analog 4,8,10 tridesmethyl telithromycin ( 2.31 ).

2.14 Molecular Modeling of Macrolide Conformations

Before starting the synthesis we collaborated with the MacKerell lab in order to

determine the consequence of desmethylation on conformations caused by replacement of

the methyl groups with hydrogens using molecular dynamics. The MacKerell lab has the

expertise in developing pharmacophores for rational drug design based on computer

aided drug design. They use molecular dynamics simulations to sample the

conformational space of the ligands, which enable them to access all possible

confirmations important at room temperature. 86 Unlike other methods (Monte Carlo based) where a single or a small number of low energy conformations are selected, the method used in this approach takes into account the dynamic nature of the ligands which enable all possible conformations of the pharmacophore. The method developed by the

MacKerell Group was termed the Conformationally Sampled Pharmacophore (CSP) that helps to draw a comparison between the distances and the angles present in the actual crystal structure of a compound to that of the conformer of its analogs and a probability distribution can be plotted. 86 Thus, CSP calculations were performed on analog ()

4,8,10tridesmethyl telithromycin ( 2.31 ) (dotted lines) and compared with the solution phase and solid phase crystal structures of TEL ( dark lines) (Figure 2.20). The distances affecting the macrolide ring conformation and binding to the ribosome were selected and comparisons were made between TEL and ()4,8,10tridesmethyl telithromycin (2.31 ).

Figure 2.20 CSP data for 4,8,10tridesmethyl telithromycin

While these data showed the distributions for 2.31 differ from that of TEL 1.6 , analog

4,8,10tridesmethyl telithromycin ( 2.31 ) does have certain conformations that overlap

with 1.6 , suggesting 2.31 can bind to the ribosome. There are consequences to the

conformational changes caused by removing syn pentane interactions that serve to bias

the classical PerunCelmer modified diamond lattice structure for macrolides. 87 Since analog 4,8,10tridesmethyl telithromycin ( 2.31 ) sampled few conformations similar to 1.6 we believed that it can bind to the ribosome and have biological activity. With the computational data in hand, effort was diverted to plan a synthetic strategy for the total synthesis of 2.31 . Knowledge of the prior art played a crucial role in developing our synthetic strategy. Most of the third generation ketolides are semisynthetic derivatives whose syntheses begin with CLA ( 1.4 ) which is synthesized from ERY ( 1.3 ). 39 A semi

synthesis approach is no longer viable for us to synthesize 2.31 as the macrolide scaffold

lacks the methyl groups at the C4,C8 and C10 positions.

Figure 2.21 Structures of key intermediates

O O Me Me 9 9 Me Me Me Me HO OMe HO OMe 12 6 12 6 NMe2 NMe2 AcO Me AcO O O O O Me O O Me 3 3 Me Me O O O O

Me Me 2.16 2.35

TEL was synthesized from the intermediate 2.16 .70,71,72 To synthesize analog 2.31 ,

intermediate 2.35 had to be synthesized (Figure 2.21). This intermediate 2.35 has a C10,

C11 olefin and a C5 desosamine sugar. The C10, C11 olefin in 2.16 was synthesized

starting from ERY. Looking at the previously reported syntheses of similar macrolides, it

was found that there is only one total synthesis of ERY that was reported by Woodward

and coworkers in 1981. 88 A semisynthesis approach to 1.3 was developed by Tatsuta

Scheme 2.71 Regioselective glycosylation by Tatsuta Me Me Me Me O O OH Me N Me Me O Me Me Me Me 9 9 9 Me2N Me Me S N Me Me Me Me MeO2CO HO OH HO OH HO OH O 12 O 6 12 OH 6 12 6 Me Me Me O ODes O OH O OH 63% 3 3 3 Me Me Me O OH O OH O OH Me Me Me 2.36 2.37 2.38

and coworkers starting from 9 Sdihydroerythronolide A ( 2.36 ). 90 They showed the installation of desosamine both regio and chemoselectively onto the C5 alcohol in presence of other secondary and tertiary alcohols with appreciable yield of 60% (Scheme

Scheme 2.72 Final steps of Tatsuta

Me Me O O Me Me Me Me 9 9 Me Me Me Me C-9 oxidation HO OH HO OH OH 12 O 6 12 6 Me Me O ODes O ODes 3 3 Me Me O OClad O OH Me Me 2.38 1.6

2.71). Further, 2.39 was converted to ERY ( 1.6 ) which involved a selective oxidation of the C9 alcohol in presence of C11 alcohol (Scheme 2.72). There is a conformational bias of the molecule which gives this selectivity. Yields were reported in the range (~50

60%). 90

The difficulty in regioselective glycosylation is one of the possible reasons for many syntheses of erythronolide A or B and not erythromycin A or B in literature.

Further, it was important to know the different strategies employed for the synthesis of these the macrolide scaffolds. Many syntheses report the use the macrocyclization across the C1 and C13 hydroxyls with cyclic protecting groups (C9, C11 and C3, C5) and selective oxidation of C9 alcohol in presence of C11 alcohol in their synthetic plan. 90

A C9 keto helps in the elimination of the C11 alcohol to synthesize an olefin across the

C10, 11 which in turn is required for the synthesis of oxazolidinone across the C12, 11 bonds. As in all the previous syntheses a late stage oxidation of the C9 secondary

alcohol is selective over the C11 alcohol. We were skeptical of obtaining similar

selectivity for our molecule as the ring confirmation plays an important role in the

selectivity. 90 Further, it takes ten steps to finish the synthesis of 2.31 from the C9 keto

compound. So the strategies that involved a C1, 13 macrocyclization were less favored. 53

A conservative approach would utilize the concept of regioselective glycosylation but with the C10, 11 olefin in place thus avoiding functional group interchanges. This made us more interested in the synthesis of macrolides like narbonolide ( 2.39 ) and pikronolide

(2.40 ) as they have the C10, C11 olefin in place (Figure 2.22). Two syntheses of

narbonolide by Fecik (2005) and Kang (2008) were reported which were inspiration to

our approach. 91,92

Figure 2.22 Structures of narbonolide and picronolide

O O

Me Me 9 9 Me Me Me Me HO 12 6 12 6 Me Me O OH O OH 3 3 Me Me O O O O

Me Me 2.39 2.40

2.15 Fecik’s Synthesis of Narbonolide

Fecik and coworkers reported a formal total synthesis of narbonolide that employed an intramolecular NozakiHiyamaKishi (NHK) coupling for macrocyclization to form the 14membered macrolide with the disconnection across the C9, 10 bonds. A

C3, 5 cyclic protecting group gave a yield of 58% for macrocyclization. The use of an acetonide failed in distinguishing the C3 and the C5 alcohol after the deprotection.91

When NHK cyclization was tried with an orthogonal set of protecting groups across the

C3 and C5 position they obtained a 90% yield for the macrocyclization. This demonstrated that macrocyclization across the C9, 10 doesn’t depend on cyclic protecting groups.

Scheme 2.8 Fecik’s synthesis of narbonolide

1) Evans Auxilary OTIPS OTIPS OTIPS O Bu2BOTf, Et3N OH 1)PMB(OMe)2 OPMB 2) LiBH 2) DIBAL-H H 4 HO HO Me Me 60% Me Me Me 80% Me Me Me 2.41 2.42 2.43

1)Cl3PhCOCl, Et3N, DMAP 1) Swern[ O] OH Me 2) Bu2BOTf, Et3N I O OH OPMB OTIPS OTIPS 3) LiOOH O OH OPMB Me 2.48 I Me O HO Me Me Me Me Me 58% Me Me Me Me 61% 2.44 2.45 OH Me 9 1) HF.Pyr 1) NHK 2) DMP [O] Me O O O OPMB Cyclization Me Me I CrCl2, NiCl2 O 12 6 Me Me Me Me Me 50% 89% Me O OPMB 3 Me 2.46 O O 1)DMP [O] Me 2) DDQ 2.39 2.47 85%

The Evans aldol reaction of aldehyde 2.41 and subsequent reductive removal of

the auxiliary furnished the alcohol 2.42 . Protection of the 1,3diol as its 4 methoxybenzylidene acetal followed by DIBALH reduction gave the secondary alcohol, as a PMB ether 2.43 . Oxidation to aldehyde, Evans aldol reaction, and the treatment with lithium hydroperoxide furnished acid 2.44 . Complete assembly of the heptaketide chain of narbonolide was accomplished by esterification with alcohol 2.48 to give ester 2.45 .

Deprotection of the TIPS group followed by DessMartin Periodinane oxidation oxidized both the primary and secondary alcohols. However, the C2 methyl group had epimerized giving aldehyde 2.46 (Scheme 2.8). Equilibration of the C2 methyl group was anticipated after the macrocyclization took place, so NHK macrocyclization was performed with 10 equivalents of CrCl 2 and catalytic NiCl 2 at 0.0025 M concentration to

furnish the allylic alcohol 2.47 in 90% yield. Thus, DMP oxidation followed by PMB

deprotection preceded with the concomitant equilibration at the C2 position to afford narbonolide ( 2.39 ). 91

2.16 Kang’s Synthesis of Narbonolide

Another elegant synthesis of 2.39 was reported by Kang and coworkers who employed ring closing metathesis (RCM) across the C10, 11 bond extending the scope of metathesis for the synthesis of 14membered macrolactones. 92 Kang demonstrated the

Scheme 2.9 Kang’s synthesis of narbonolide Yamaguchi esterification OH 1) Evans -Aldol reaction TBS 2) TBS protection OTBS O O OPMB OTBS OPMB 3) LiOOH Me Me 2.51 O HO Me Me Me Me Me Me Me 50% 61%

2.49 2.50 1) CSA, TBS deprotection O 2) DMP [O] TBS 3) Vinyl Mg Br Me Me 9 O O OPMB OTBS 4) DMP [O] Me Me O 6 Me Me Me Me Me 40% Me O OPMB 3 2.52 Me O OTBS

2.53 O O

Me Me 9 9 1) HF/Py C -3 TBS RCM, G -II Me Me deprotection Me Me 6 2) DMP [O] 6 Me Me 88% O OPMB 60% O OPMB 3 3 Me Me O OTBS O O Me Me 2.54 2.55

DDQ 2.39

macrocyclization across the C10, 11 bond with high yield of 88% without the use of cyclic protecting groups. The synthesis utilizes a similar strategy as Fecik for the synthesis of an intermediate acid 2.50 (Scheme 2.9).92 The aldehyde 2.49 was prepared

from the same intermediate similar to 2.41 starting with a different protecting group.

Evans aldol reaction installed the stereochemistry at the C3 and C5 positions.

Intermolecular Yamaguchi esterification of acid 2.50 with 2.51 yielded ester 2.52 .

Treatment of 2.52 with CSA gave a primary alcohol which was oxidized with DMP to afford an aldehyde. This aldehyde was then treated with vinylmagnesium bromide to give an allylic alcohol which was again oxidized to yield the enone 2.53 . Upon treatment with

20 mol% Grubbs second generation catalyst under 0.01 M concentration, the RCM

occurred smoothly to furnish 88% of the macrolactoketone 2.53 . Further steps involved the deprotection of the C3 TBS ether followed by DMP oxidation to give the C3 keto

2.39 .

Upon treatment with DDQ, the C5 PMB protecting group was deprotected furnishing narbonolide ( 2.39 ). Kang and coworkers reported the use of a C5 TBS protection group as their first approach to synthesize 2.39 but couldn’t achieve successful deprotection in both acidic and basic conditions. Thus a C5 PMB group was preferred as oxidative neutral conditions can be employed for the deprotection.

Based on this prior art, we developed our own synthetic route for the synthesis of

desmethyl analogs of TEL.

2.17 Total Synthesis of (-)-4,8,10-Tridesmethyl Telithromycin

Key Strategies Planned for the Synthesis

We planned to install the oxazolidinone side chain of 2.31 by employing a onepot

carbamoylation/intramolecular azaMichael method developed by Baker and coworkers

used in the synthesis of TEL (Figure 2.23). 93 Thus, 2.56 can be synthesized by a onepot

carbamoylation/intramolecular azaMichael reaction with telithromycin side chain 2.58 allowing the installation the side chain and finish the total synthesis. This

Figure 2.23 Retrosynthesis for the synthesis of the oxazolidinone

N O N N ( ) O 4 N 9 Me O 11 OMe 6 Me 12 NMe2 5 HO Et O 4 O O Me 3 O O Me

(-)-4,8,10-tridesmethyl telithromycin (2.31)

N N O N N H N N ( )4 O 2 O ( )4 N 9 N Baker Me 9 O 11 OMe Me 6 Cyclization 12 2.58 Me NMe2 HO 11 OMe 5 6 2.31 McO 12 NMe 4 O Me Me 2 Et O O 5 McO 3 Et O 4 O O Me O O 3 O OTBS Me Mc= Methyl Carbonate Me

2.56 2.57 method was validated in the discovery of TEL as discussed earlier. 70,71,72 Intermediate

2.57 can be accessed from either a regio and chemoselective glycosylation of 2.59 with

1.48 or a regioselective glycosylation of 2.60 with 1.48 (Figure 2.24).94,89

Figure 2.24 Retrosynthesis for installing desosamine onto C5

O O

9 9 Me Me HO 11 OMe 6 HO 11 OMe Me 12 NMe2 6 5 Me 12 McO 5 Et O 4 O O Me Et O 4 OH 3 3 O O O OH Me Me Me O N 2.57 2.59 Me2N O S N MeO2CO

9 1.48 Me HO 11 OMe 6 Me 12 5 PG= protecting group Et O 4 OH 3 O OPG

Me 2.60

Intermediates 2.59 and 2.60 are the macrolides most similar to narbonolide ( 2.39 ) with different functionalities at C6 and C12 positions. We wanted to employ both the

Figure 2.25 Macrocyclization strategies

O NHK RCM 9 O OPG OPG Me 5 7 9 HO 11 OMe HO 1 3 OTBS 6 Me 12 2.59 5 Me MeO Me Et O 4 OPG 2.62 2.60 3 O OPG Et Me R 12 OH 2.61 10 HO Me

2.63: R=I 2.64: R= H macrocyclizations across the C9, 10 (NHK) bond and the C10, 11 bond (RCM).

Significantly, our substrates differ in that they possess a C12 hydroxyl group (Figure

2.25).91,92

2.18 First Generation Approach

The first generation approach employed a regio and chemoselective glycosylation for the synthesis of 2.57 . The retrosynthesis of these fragments are shown

in Figure 2.26. To access 2.59 , we intended to use identical protecting groups at C3 and

C5. The precursor to the cyclization reactions can be accessed through Yamaguchi esterification of acid 2.65 with either 2.63 or 2.64 .

Figure 2.26 Retrosynthesis for acid 2.65 , diols 2.63 and 2.64

O OTBS OTBS OTBS 7 9 5 7 9 5 HO 1 3 OTBS BnO OTBS MeO Me Me MeO Me 2.65 2.66

5 CO2Me BnO 6 BnO OH Me 2.67 2.68

Et I 12 OH Me 10 Me HO Me Me O Me O Me Et O Et 2.63 CHO OH OH Et Et 2.69 2.70 2.71 12 10 OH

HO Me

2.64

An Evans syn aldol was planned to fix the stereochemistry at the C2 and C3 positions.

Sharpless asymmetric dihydroxylation of olefin 2.67 was anticipated to give the C5 and the C6 alcohols. The olefin in 2.67 was accessed starting from 2.68 (Figure 2.26).

Synthesis of fragments 2.63 and 2.64 are known from the literature.94 We wanted to

access both the fragments through a common intermediate i.e., aldehyde 2.69 . This

compound can be prepared from epoxide 2.70 , which was accessed through kinetic

resolution of rac 2.71 via the Sharpless asymmetric epoxidation.

Scheme 2.10 Synthesis of diols 2.64 and 2.63

Me Me (-)-DIPT/Ti(i-PrO)4 1.)PivOH, Ti(O-iPr)4 Me Me O 2) DMP, PPTS O Me t-BuOOH 3.) MeLi O OH Me Me 65% over three steps OH 35% OH Et 2.71 2.70 2.72

Me Me (COCl)2, DMSO, Et3N O Me O CHO Et 2.69

1.) Ph3PCH2 1.) CrCl2, CHI3 Et Et 2.) 1N HCl (aq) 2.) 1N HCl (aq) I OH OH 65% 30% HO Me HO Me

2.64 2.63

Kinetic resolution of rac2.71 via the Sharpless asymmetric epoxidation protocol

furnished enantioenriched alcohol 2.70 in 35% yield and 92% ee as per Mosher ester

95 analysis (Scheme 2.10). Regioselective ringopening with pivalic acid and Ti(OiPr) 4, acetonide formation and treatment with MeLi afforded alcohol 2.72 (59% over three

steps). 94 Swern oxidation of 2.72 to aldehyde 2.69 yielded a common intermediate to synthesize 2.64 and 2.63 .95 Takai olefenation gave the vinyl iodide which upon treatment with 1M HCl in MeOH deprotected the acetonide giving 2.63 in 30% yield over two steps. Wittig methylenation of 2.69 followed by removal of the acetonide gave 2.64 .

(65% yield over 2 steps). 95

Synthesis of fragment 2.65

Synthesis of fragment 2.65 began with commercially available 3benzyloxy propanol ( 2.68 ) which was oxidized using the Swern protocol (Scheme 2.11). Addition of

2propenyl MgBr and subsequent JohnsonClaisen orthoester rearrangement afforded

enoate 2.67 in 48% overall yield. 96 Reduction of the ester and protection of the newly formed alcohol as its tert butyldimethylsilyl (TBS) ether provided 2.73 in 78% yield over two steps. Sharpless dihydroxylation (AD mixβ) established the requisite stereochemistry of the hydroxyls at C5 and C6 in 91% yield (er>20:1). 97

Scheme 2.11 Synthesis of regioisomer of 2.77

1) (COCl)2, DMSO, Et3N 2) 2-propenyl MgBr, THF 1) LiAlH4, Et2O 3) (MeO)3CCH3, EtCO2H 2) TBSCl, imidazole CO2Me BnO OH BnO 48% 78% 2.68 2.67 Me

OTBS HO TBSO AD mix β 6 5 BnO BnO 91% HO Me Me er > 20:1 2.73 2.74

TBSO TBSO 6 BnO 5 Mec hanism: X MeO Me 2.77 t-Bu Me 1) TBSOTf, 2,6-lutidine Si 2) NaH, MeI, 70% Me 4 O TBSO 1,4 silyl O Na TBSO MeO TBSO 3 O→O 2 6 BnO BnO 5 migration BnO O 1 Me TBSO Me TBSO Me Na 2.75 2.76 2.78

Selective protection of the secondary C5 alcohol with TBSOTf and 2,6lutidine followed by treatment with NaH and MeI resulted in the formation of 2.78 as opposed to the desired regioisomer 2.77 in 70% over two steps via a 1,4 silyl OO migration (Scheme

2.10). 94,98 This migration came to light when we succeeded in obtaining a single crystal x 62

ray structure of cylclized product 2.87 (Figure 2.27). The synthesis was carried forward

with the undesired regioisomer 2.88.

Scheme 2.12 Synthesis of iodoester 2.84

(COCl) , DMSO, MeO TBSO H , Pd/C, MeO TBSO 2 OMe TBSO 2 Et3N 6 6 OHC 6 5 5 5 BnO 80% HO TBSO Me TBSO Me TBSO Me 2.78 2.79 2.80

O O OH OMe TBSO 1) TBSOTf, 2,6-lutidine O OTBS OMe TBSO 2.81, Bu BOTf, Et N, 2 3 2) LiOOH, THF, H2O, O 3 5 N HO 3 5 60% Me TBSO Me 85% Me TBSO Me (dr> 20:1) Bn 2.82 2.83

O O Cl3PhCOCl, Et3N, DMAP, Et O OTBS OMe TBSO 2.63 Me I O N O 3 5 74% HO Me Me TBSO Me Bn 2.81 2.84

Debenzylation of benzyl ether 2.78 afforded alcohol 2.79 in 80% yield (Scheme

2.12). It was important to monitor the reaction via TLC every fifteen minutes to avoid

unnecessary silyl ether deprotection. Reproducible results were only obtained when the

Pd/C was purchased from Acros chemical company. Swern oxidation of 2.79 to aldehyde

2.80 was followed by the Evans aldol reaction with propionimide 2.81 . This set the stereochemistry at C2 and C3 positions affording aldol product 2.82 in 78% yield

(dr>20:1) over two steps. 99 Protection of the C3 hydroxyl with TBSOTf and removal of the auxiliary with LiOOH provided the acid 2.83 in 85% yield over two steps. 92 This acid was used to couple with both 2.63 and 2.64 forming the precursors for both NHK and

RCM macrocylizations. Chemoselective Yamaguchi esterification of 2.83 and iodo diol

2.63 afforded ester 2.84 in 74% yield.92 The C9 primary TBS ether was selectively

removed under acidic conditions by using CSA in MeOH at 0 ºC obtaining 2.85 in 85%

yield (Scheme 2.13).91 Oxidation of alcohol 2.85 with the DessMartin Periodinane

(DMP) and NaHCO 3 proceeded smoothly

Scheme 2.13 Synthesis of macrocycle 2.88 via NHK

Et O OTBS OMe OTBS Et O OTBS OMe OH CSA, MeOH I I O 3 5 O 3 5 85% HO Me Me TBSO Me HO Me Me TBSO Me 2.84 2.85 Et O OTBS OMe DMP, NaHCO3, CrCl2, cat. NiCl2, DMSO, I CHO O 3 5 80% 50% HO Me TBSO Me Me 2.86 OH O

Me HO Me OTBS DMP, Pyridine. HO 6 OTBS Me 6 5 Me 5 Et 82% O OMe Et O OMe 3 3 O OTBS O OTBS Me Me 2.87 2.88 to furnish aldehyde 2.86 in 80% yield. At this point, the stage was set to try the NHK cyclization. This reaction proceeded to furnish the macrolactoketone 2.87 with yields ranging from 3060%. Many conditions were tried to optimize the yield for this cyclization. 91,100 The best conditions involved the use of DMSO which was distilled

º º under reduced pressure (120 C to 80 C at vacuum 20 or 4 mmHg) and CrCl 2 and NiCl 2 weighed in a glove box. The DMSO solution was subjected to three cycles of freeze pumpthaw, before 10 equivalents of CrCl 2 and catalytic NiCl 2 were added to the

aldehyde 2.86 in DMSO (0.0025 M) at rt and stirred for 20 h. The yield for the optimized

NHK cyclization was 50% yield of 2.87 as a 1:1 mixture of diastereomeric allylic

alcohols. Subsequent oxidation of 2.87 with DMP and pyridine furnished macroketolactone 2.88 .

In parallel, we developed a RCM route similar to Kang’s synthesis of narbonolide

(Scheme 2.14). 92 Yamaguchi esterification of acid 2.83 and 2.64 gave the ester 2.89 with the olefin precursor at one end of the carbon chain. Acidic deprotection of the C9 TBS with CSA delivered the C9 alcohol 2.90 . The oxidation state at C9 was set by oxidizing

Scheme 2.14 Synthesis of macrocycle 2.88 via RCM

OH TBSO HO Me Me O OTBS OMe OTBS HO Cl3PhCOCl, Et3N, DMAP, OTBS 6 Me HO 3 5 5 Et O OMe Me TBSO Me 78% 2.83 3 O OTBS Me 2.89 HO Me CSA, MeOH HO OTBS 1) Dess-Martin Periodinane, NaHCO3 6 2) Vinyl MgBr, THF Me 5 3) Dess-Martin Periodinane, CH2Cl2, 82% Et O OMe 55% 3 O OTBS O Me 2.90 O

Me Me HO HO OTBS OTBS 20 mol% Grubbs II cat., 6 Me 6 Me 5 5 Et Et O OMe O OMe 3 3 O OTBS O OTBS

Me Me

2.91 2.88 the alcohol with DMP. This aldehyde was then reacted with 5 equivalents of vinylmagnesium bromide at 0 ºC to give an allylic alcohol which was oxidized to an

enone 2.91 using DMP. Treatment of the diene substrate with 20 mol% Grubbs Second

Generation catalyst and stirring at rt for 20 h gave macroketolactone 2.88 in 60% yield

(90% yield BORSM, based on recovered starting material). 92

Both macrocyclization methods were effective with yield of 50% and 60% respectively.

Our experience clearly suggested that the RCM macrocyclization approach was easier,

more consistent, less labor intensive and most importantly scalable compared to that of the NHK macrocyclization. As compound 2.88 was a solid, recrystallization of 2.88 from

Et 2O by slow evaporation resulted in crystals suitable for xray analysis. Surprisingly, the

groups at the C5 and C6 positions in 2.88 had been transposed (Figure 2.27). This led us to the use of alternate procedures for the C6Omethylation and avoidance of any basic conditions to install the methyl ether.

Figure 2.27 Xray crystal structure of macrocycle 2.88

Me HO OTBS Me 6 5 Et O OMe 3 O OTBS Me

2.88 From the xray crystal structure it was evident that we needed an alternate strategy and address two important things:

1) Rectify the C6Omethylation

2) Have orthogonal protecting groups at C3 and C5 so that both glycosylation

approaches could be attempted.

We revisited the methylation reaction responsible for the attendant transposition. By employing a more reactive methylating agent (e.g., Meerwein’s salt) would avoid the unwanted 1,4 OO silyl migration enabled by reactive metal alkoxide 2.76.101 In

addition, we recruited the TES protecting group to establish an orthogonal set at C3 and

C5 and offer recourse in the event a regioselective glycosylation was unsuccessful.

Prior recruiting the TES protecting group we explored other viable combinations such as

C5 PMB/C3 TBS and C5 TBS/C3 PMB. The main factors that guided the choice were yields and scalability.

2.19 Second Generation Approach

The secondary C5 alcohol was protected as a TES ether by using TESCl and imidazole in DMF at 0 ºC giving 2.92 in 90% yield. We then methylated the C6

hydroxyl employing Meerweinˈs salt and Proton Sponge in addition to the NaH, MeI procedures (Scheme 2.15). Thus, 2.92 when treated with Me 3OBF 4 (i.e., Meerweinˈs salt) and Proton Sponge in CH 2Cl 2 afforded desired regioisomer 2.94. Treatment of 2.92 under rearrangement conditions (i.e., NaH and MeI) furnished the expected but undesired regioisomer 2.93. We further confirmed the structure of 2.94 with 2DNMR experiments. 101

Scheme 2.15 Synthesis of regioisomers 2.93 and 2.94 MeO TBSO NaH, MeI 6 DMF BnO 5 HO TBSO TESO TBSO 78% TESCl TESO Me 2.93 6 imidazole 6 BnO 5 BnO 5 90% Me OBF HO Me HO Me 3 4 Proton TESO TBSO Sponge 2.74 2.92 6 BnO 5 CH Cl 2 2 MeO Me 80% 2.94

With the correct regioisomer 2.94 the sequence of reactions was repeated. Thus,

removal of the benzyl ether in 2.94 afforded alcohol 2.95 in 85% yield (Scheme 2.16). 99

Oxidation of 2.95 with the Swern protocol followed by the Evans aldol reaction furnished

2.97 in 78% yield (dr>20:1). Protection of the C3 hydroxyl with TBSOTf and removal of the auxiliary with LiOOH resulted in acid 2.98 in 85% over two steps. 92 Yamaguchi

esterification of 2.98 and 2.63 delivered ester 2.99 in 75% yield. Removal of the primary

Scheme 2.16 Synthesis of NHK precursor 2.99

OTES TBSO OTES TBSO 1) H2, Pd/C 1) (COCl) , DMSO, Et N 6 6 2 3 BnO 5 HO 5 MeO Me 85% MeO Me 2.94 2.95

OTES TBSO O O OH OTES TBSO 1) TBSOTf, 2,6-lutidine 1) 2.81, Bu2BOTf, Et3N 2) LiOOH, THF, H2O, OHC 5 O N 3 5 MeO Me dr> 20:1, Me MeO Me 85% 78% over 2 steps Bn over two steps OTBS 2.96 2.97 I

O OTBS OTES Me Et HO OMe 1) Cl PhCOCl, Et N, DMAP, 3 3 Me 6 HO 3 5 OTBS + I OH 5 MeO Me Et O OTES Me HO Me 75% 3 O OTBS 2.98 2.63 Me

2.99

TBS group was attempted with sixty equivalents of NH 4F in methanol at reflux condition.

This reaction delivered 65% yield of 2.100 on smaller scales (~500 mg) but was not

scalable and caused etching of glass reaction vessels. An alternate procedure involving

TBAF/AcOH was used that afforded 2.100 with a yield of 65% on a 3 gram scale

(Scheme 2.17). 102 This C9 alcohol 2.100 was converted to the aldehyde 2.101 using

DMP oxidation (78% yield), which set the stage for the intramolecular NHK reaction.103

Based on previous mentioned conditions this cyclization proceeded with a yield of 50% to give 2.102 as a 1:1 diastereomeric mixture of alcohol at C9 position. Oxidation of allylic alcohol 2.102 furnished the desired macroketolactone 2.103 in 80% yield. 91

Protection of the C12 hydroxyl with a TMS group did not have any effect on the yield of the NHK cyclization. We also prepared 2.102 following RCM conditions. Thus, the

Yamaguchi protocol was employed to couple acid 2.98 and the diol olefin 2.64 yielded ester 2.104 in 78% yield (Scheme 2.18). Employing the optimized C9 deprotection condition utilizing TBAF/AcOH, furnished alcohol 2.105 (86% yield 68

Scheme 2.17 Synthesis of macrocycle 2.103 via NHK

OTBS OH I I I CHO Me Me Me HO HO OMe HO OMe 1) TBAF, AcOH, 1) DMP, NaHCO , OMe 6 6 3 6 Me Me Me 5 5 5 65% Et Et O OTES O OTES 78% Et O OTES 3 3 3 O OTBS O OTBS O OTBS

Me Me Me

2.99 2.100 2.101 OH O

Me HO OMe Me (j) DMP, HO (i) CrCl2, cat. NiCl2, DMSO, 6 OMe Me 6 5 Me 5 Et O OTES 80% 50% Et O OTES 3 3 O OTBS O OTBS Me Me 2.102 2.103

borsm). Oxidation of the C9 alcohol using DMP in 2.104 provided the aldehyde which

was treated with vinylmagnesium bromide to give a mixture of allylic alcohol at C9 position. Subsequent oxidation of this mixture with DMP under high dilution afforded the

RCM substrate 2.106 in 60% over 3 steps.92 The RCM reaction proceeded smoothly in

CH 2Cl 2 (0.01 M) at rt for 20 h with 20 mol% Grubbs second Generation catalyst (2.107) to provide 2.103 in 60% yield (90% borsm). Although the RCM route has more steps, it was the more scalable, reproducible and low maintenance route wherein we were able to synthesize ~5 grams of the macrocycle in sequential batches. The largest scale RCM reaction performed was on a gram scale. This RCM reaction furnished a yield ranging

Figure 2.28 Structures of GII and HGII

MesN NMes MesN NMes Cl Cl Ru Ru Cl Cl Ph PCy i-PrO 3

2.107 2.108 69

Scheme 2.18 Synthesis of macrocycle 2.103 via RCM

TBSO Me O OTBS OTES OTBS HO Cl3PhCOCl, Et3N, DMAP, OMe 2.64 Me 6 HO 3 5 5 Et O OTES Me MeO Me 78% 3 2.98 O OTBS Me HO 2.104 Me TBAF/AcOH HO OMe 1) Dess-Martin Periodinane, NaHCO3 6 2) Vinyl MgBr, THF Me 5 3) Dess-Martin Periodinane, CH2Cl2, 86% Et O OTES borsm 60% 3 O OTBS O Me O 2.105

Me Me HO HO OMe OMe 6 20 mol% Grubbs II cat., 6 Me Me 5 5 Et O OTES Et O OTES 3 3 O OTBS O OTBS Me Me 2.106 2.103

From 60 to 72% with the mass balance being unreacted enone 2.106. Grubbs Hoveyda –

II (2.108) furnished lower yields (3540%) for macrocyclization compared to GrubbsII

(Figure 2.28). This was due to the greater activity of the Grubbs HoveydaII compared to

GrubbsII for RCM.104 It was important to note that the RCM reaction did not work when the C12 hydroxyl was protected with TMS. Initially there was a concern with using five equivalents of vinylmagnesium bromide for addition to the C9 aldehyde in the presence of the C12 hydroxyl. Fortunately, the reaction proceeded without any issues keeping the

C12 hydroxyl unprotected even at large scales (~2 g). 92

With significant amounts of macrocycle in hand, attention was directed toward two remaining challenges in the synthesis of 2.31 . They were:

1) Installation of the C5 desosamine

2) Installation of the telithromycin side chain 70

2.20 Installation of C-5 desosamine

A conservative approach to glycosylation involved a selective deprotection of the

C5 TES followed by glycosylation. To this end, the C5 TES ether was removed under various conditions (e.g., pTsOH, PPTS, HF). 105 Unfortunately, this was accompanied by

ketalization at the C9 position 2.110 (Scheme 2.19) as a consequence of the acidic conditions employed to remove the TES group. We were unaware of this fact as both

Kangˈs and Fecikˈs synthesis of narbonolide, a C5 PMB group was used which was deprotected under neutral conditions. 91,92

Scheme 2.19 Unexpected ketal formation between C9 carbonyl and C5 alcohol

O O OH

p-TsOH Me PPTS Me Me HO OMe HF HO OMe HO OMe 6 6 O Me Me Me 6 5 5 Et O OTES Et O OH Et O 5 3 3 3 O OTBS O OTBS O OTBS Me Me Me

2.103 2.109 2.110

With no success in isolating the C5alcohol and C3 TBS compound, we decided to do a global deprotection followed by a regio and chemoselective glycosylation. Treatment of

2.103 with 3.5 equivalents of TBAF (i.e., basic conditions) at 010 ºC resulted in the

removal of both silyl groups, affording triol 2.111 in 70% yield (Scheme 2.20). 102

Previous work by Martin, Toshima and Tatsuta showed, regioselective glycosylation occurs exclusively onto C5 in closely related erythronolide systems. When we repeated the regioselective glycosylation of 2.111 at C5 in the presence of the C3 hydroxyl with

donor 1.48 under the agency of AgOTf and 2,6di tBu4Mepyridine (DTBMP) the reaction led exclusively to the decomposition of starting material.105

Scheme 2.20 Unsuccessful regioselective glycosylation with 2.111

O O

9 9 Me Me HO HO OMe OMe TBAF 12 12 1.48 Me Me , AgOTf, DTBMP 5 5 Decomposition 70% Et O OTES Et O OH

O OTBS O OH Me N Me Me O Me2N S N 2.103 2.111 MeO2CO 1.48

Neither strategy yielding any successful glycosylated product and recourse was made to a new strategy. To achieve a successful glycosylation it was important to reduce the C9 ketone and protect the C3 hydroxyl functional group. Thus the C9 ketone was reduced under Luche conditions at 60 ºC to give an inseparable 7:1 mixture of

diasteromers (Scheme 2.21). 106 Subsequent treatment with pTsOH in

Scheme 2.21 Attempt to isolate C5 alcohol and C9 keto compound 2.113

O OH 9 9 Me 1) NaBH4, CeCl3 7H2O, HO Me OMe dr= 7:1 HO OMe 12 Me 12 MnO2 5 2) p-TsOH, MeOH Me 5 Et O OTES Et O OH 75% O OTBS O OTBS Me Me 2.103 2.112 OH O

9 Me Me HO HO OMe OMe O 12 6 Me Me 5 Et O OH Et O 5 3 O OTBS O OTBS Me Me

2.113 2.110

methanol at 0 ºC selectively removed the C5 TES ether in the presence of the C3 TBS ether to afford triol 2.112 in 75% yield over two steps. Allylic oxidation using MnO 2 furnished the C5 alcohol with the C9 keto which after column chromatography isolated as a mixture of 7:1 ( 2.113:2.110 ). This showed that compound 2.113 is an unstable

compound and the stability is highly pH dependant. Since secondary allylic alcohols (C

9) are more reactive than secondary alcohols it was important to protect the C9 alcohol

regioselectively. Choice of the protecting group was critical at this point, as we wanted to

have an orthogonal set at C9, C3 and C12. Initially TBS and TBDPS were used, but

later TES was the group which was employed due to the ease in protection and

deprotection (Scheme 2.22). Regioselective protection of secondary allylic alcohols over

Scheme 2.22 Unexpected C12 glycosylation

Me2N OH Me OTES

9 MeO2CO O 9 Me HO 1) TESCl, imidazole Me OMe 2) 1.48, AgOTf, DTBMP O 12 OMe Me 12 5 Me 5 Et O OH 42% over two steps. Et O OH 3 O OTBS O OTBS Me Me 2.112 2.114 Me2N Me2N OH O Me Me MeO CO MeO2CO O 9 2 O 9 Me Me 1) TBAF O OMe 1) DMP O OMe 12 12 Me Me 5 5 Et O OH Et O O 3 3 O OH O O Me Me 2.115 2.116 (unstable)

secondary alcohols was well precedented. Thus, treatment of 2.112 with TESCl and

imidazole at 78 ºC in DMF/DCM mixture with catalytic DMAP, led to selective protection of the C9 alcohol. 107 The only alcohols left unprotected were the C5 73

(secondary) and the C12 (tertiary) alcohols. Since glycosylation has been shown to be selective with the secondary alcohols in presence of the tertiary alcohols, protection of the alcohol was not necessary.

When the C9 TES protected compound was treated with donor 1.48 , AgOTf and

DTBMP glycosylation occurred onto the C12 position as opposed to the desired C5. 105

This was first evident when the further steps were carried out in the synthesis. When

2.114 was treated with TBAF at 0 ºC, all the silyl groups were deprotected. Subsequent

oxidation with DMP revealed an unstable species 2.116 whose carbon NMR suggested

the presence of three ketone peaks. This led us to assign the structure of 2.115 completely

using 2DNMR experiments with the help of Dr. DeBrosse. These experiments suggested

that the sugar was indeed on the C12 carbon and not on C5. Further, an HMBC

correlation between the anomeric proton in desosamine with the C12 methyl carbon and

the C12 carbon were shown. Though the C12 hydroxyl is a tertiary alcohol, it is also an

allylic alcohol thus making it more reactive than the C5 alcohol at the temperature and

chemical conditions for glycosylation. It was clear that to successfully achieve

glycosylation onto the C5 alcohol all other hydroxyls must be protected. Towards this

end, macroketolactone 2.103 was first reduced under Luche conditions. Silylation of both

C9 and C12 hydroxyls with TESOTf and 2,6lutidine and subsequent treatment with p

TsOH in MeOH at 010 ºC selectively deprotects the C9 and C5TES groups leaving the

C12TES protected , affording 2.114 in 52% yield over three steps (Scheme 2.23). If the

C12 TES ether was deprotected than the Luche product or the triol 2.117 would have been formed, however neither were observed. Regioselective silylation of the allylic C9

Scheme 2.23 Successful C5 glycosylation

O OH

9 1) NaBH4, CeCl3H2O, dr= 7:1 9 2) TESOTf, 2,6-lutidine; 1) TESCl, imidazole Me Me 3) PTSA, MeOH 2) 1.48, AgOTf, DTBMP HO OMe TESO OMe 12 12 Me Me 5 52% over three steps 5 50% over two steps Et O OTES Et O OH

O OTBS O OTBS Me Me 2.103 2.117 OH OTES

8 8 Me Me HO OMe TESO OMe 1M TBAF NMe NMe Me 2 Me 2 McO McO Et O 4 O O Me Et O 4 O O Me 95%

O OTBS O OTBS Me Me 2.118 O 2.119

8 Me DMP, CH2Cl2, . HO OMe Me NMe2 McO Et O 4 O O Me

O OTBS

Me 2.120

alcohol with TESCl furnished the C9 TES product which then underwent glycosylation at the C5 position with donor 1.48 furnishing 2.118 in 50% yield over two steps. 105 The structure of this compound was confirmed with 2DNMR experiments. It was only after protecting all the other alcohols, that glycosylation occurred on the C5 hydroxyl group in

50% yield over two steps. Fluoridemediated cleavage of silyl ethers at C9 and C12 with 1M TBAF solution in THF at 0 ºC yielded 2.119 in 95% yield. This was followed by

DMP oxidation at C9 to furnish the glycosylated macroketolactone 2.120 in 88% yield.

This structure was rigorously confirmed by 2D NMR experiments and the full

assignments are provided in the appendix section.

2.21 Installation of Telithromycin Side Chain

The synthesis of 2.120 set the stage up for introducing the side chain and finishing

the synthesis. Most of the previous endgames had the oxidation state at C3 as a protected

alcohol (cladinose) or converted it into a ketone. Having a 1, 3 diketo systems at C1 and

C3 makes the C2 hydrogen very labile and prone to epimerization in presence of a base

especially without the presence of the C4 methyl group. Since activation of the C12

hydroxyl involved the use of strong bases like NaHMDS, LiHMDS and NaH, we decided

to keep the C3 as the protected TBS ether. Initially conditions of NaHMDS, CDI and

LiHMDS, CDI were tried to make the C12 CDI product. 72,93 Later the NaH protocol reported by Chiron Pharmaceuticals proved to be the most consistent and reliable method. 108 To obtain reproducible results, the NaH used must be fresh and stored in small glass vials placed separately in smaller desiccators. Upon significant optimization, the

Scheme 2.24 Installation of TEL side chain

O O

O 8 8 Me Me HO N OMe O OMe NMe NaH, CDI, THF/DMF Me 2 N Me NMe2 McO McO 4 O Et O O Me Et O 4 O O Me

O OTBS O OTBS Me Me 2.120 2.121 N

O N N ( )4 O N 10 8 Me 2.58, O OMe CH CN/H O 3 2 Me NMe2 McO 4 O Me 35% Et O O O OTBS Me

2.122

endgame began with the activation of the C12 alcohol using NaH. Compound 2.120 with

CDI was taken in a mixture of DMF/THF and cooled to 20 ºC ( very important ) and

then NaH was added (Scheme 2.24). After the reaction, the CDI product was taken in a

mixture of CH 3CN/H 2O (9:1) and butylamine 2.58 was added. This effected a tandem

carbamoylation/intramolecular azaMichael sequence to stereoselectively afford

oxazolidinone 2.122 in 35% to 50% overall yield. 72,93 Various conditions had to be employed for the deprotection of the C3 TBS ether. Many conditions for molecules containing basic nitrogens are listed in the literature and were attempted to obtain 2.123 .

Treatment of 2.122 with TBAF, HF, HF•pyridine, HF•Et 3N did not yield any of the C3 deprotected compound. 103 Roush and coworkers demonstrated the use of tris

(dimethylamino) sulfonium difluorotrimethylsilicate (TASF) in the synthesis of

109 bafilomycin A 1 where an aldol TBS ether was successfully deprotected. When we repeated Roush’s conditions on our system, the reaction furnished the C3 alcohol 2.123 in 70% yield (Scheme 2.25).

Scheme 2.25 Deprotection of the C3 TBS

N N O O N N N N ( )4 ( )4 O O N 10 8 N 10 8 Me Me O O OMe TASF, DMF/H2O OMe Me NMe2 Me NMe2 McO McO Et O 4 O O Me Et O 4 O O Me 70% O OTBS O OH

Me Me

2.122 2.123

The CoreyKim oxidation is a well established method for oxidizing the C3 alcohol in similar macrolides. Oxidation of 2.123 furnished the C3 ketone in 75%

yield. 108,110 Finally, methanolysis removed the methyl carbonate from the C2ˈ position of desosamine to secure ()4,8,10tridesmethyl telithromycin ( 2.31 ) in 60% yield (Scheme

2.26).

Scheme 2.26 C3 oxidation and methanolysis

N N O O N N N N ( ) ( ) 4 4 O O 10 8 N 10 8 N Me Me (c) NCS, DMS, Et N O O OMe 3 OMe NMe2 Me NMe2 (d) MeOH Me HO McO 4 O Me Et O 4 O O Me Et O O 60% O OH O O Me Me

2.123 (-)-4,8,10-tridesmethyl telithromycin (2.31)

2.22 Biological Evaluation of (-)-4,8,10-Tridesmethyl Telithromycin

With 4,8,10tridesmethyl telithromycin analog 2.31 in hand, we approached the

Mankin lab at the University of Illinois at Chicago for testing against several bacterial

strains of Escherichia coli and Staphylococcus aureus using TEL (1.6 ) as the baseline

(Table 2.5). Minimum inhibitory concentration (MIC) values are reported in µg/mL for

the 4,8,10tridesmethyl telithromycin analog ( 2.31 ) and telithromycin ( 1.6 ). While both

resistant strains (entries 1 and 5) were not susceptible to either macrolide, both E. coli

wildtype and A2058G mutant (entries 2 and 3) were inhibited by both analog 2.31 and

TEL (1.6 ). Moreover, desmethyl analog 2.31 was less potent than TEL (1.6 ) by a factor

of 64 (entries 2 and 3). As described, this may be due to the conformational flexibility of

2.31 versus 1.6 , in addition to loss of van der Waals contacts at C4, C8 and the C10.

Curiously, desmethyl analog 2.31 was found to be more potent than TEL (1.6 ) against S.

aureus clinical strain UCN14 with an A2058T mutation (entry 4). The UCN14 strain is a

clinically relevant important strain of S. aureus that affects patients with cystic fibrosis.

The UCN14 strain was resistant to macrolide antibiotics like ERY, AZY and TEL but was found to be more susceptible to other classes of antibiotics like Clidamycin,

Dalfopristin, Quinupristindalfopristin and Spiramycin. The MIC values in these antibiotics ranged from 1 to 0.15 µg/mL.111

Table 2.4 MIC data of 2.31 using 1.6 as the baseline

These results demonstrate that structural simplification (i.e., functionoriented synthesis)

and/or molecular editing of established antibiotics can result in analogs with improved

activity against A2058T ribosomal mutants. 112,113

In conclusion, we have prepared 4,8,10tridesmethyl telithromycin ( 2.31 ), a desmethyl analog of ketolide antibiotic TEL (1.6 ), by chemical synthesis. This analog was able to penetrate bacterial cells, bind the ribosome and inhibit bacterial growth. We were able to prepare a total of 12.1 mg of analog 2.31 in 23 operations (42 steps overall,

31 steps in the longest linear sequence), which was found to inhibit bacterial growth. In addition, our analog was more potent than TEL against an A2058T mutant. 114

CHAPTER 3: Synthesis and Biological Evaluation of (-)-4,10-Didesmethyl

Telithromycin

3.1 Introduction

With the encouraging results from the biological evaluation of 4,8,10

tridesmethyl telithromycin (2.31 ) we embarked upon the total synthesis of ()4,10

didesmethyl telithromycin (2.32 ), the next analog in the series.114 Initial efforts involved

installation of the C8 methyl group onto the macrolactone using the Still macrocyclic

stereocontrol strategy.115 The synthesis was later accomplished by installing the C8 methyl at an early stage in the synthesis.

Figure 3.1 Structure of 4,10didesmethyltelithromycin

N O N N ( )4 O Me N 9 Me O 11 OMe 12 6 Me NMe2 HO Et O O O Me 3 O O

Me 4,10didesmethyltelithromycin ( 2.32 )

3.2 Molecular Modeling of 4,10-Didesmethyl Telithromycin

Prior to starting the synthesis, CSP was performed to suggest the consequence of

desmethylation on conformations caused by replacement of the methyl groups with

hydrogens using molecular dynamics. 86 This data was plotted along with the CSP of

4,8,10tridesmethyl telithromycin (2.31 ) and telithromycin ( 1.6 ) considering both the

80 solution phase and solid phase crystal structure (Figure 3.2). Those distances that affect the macrolide ring conformation and binding to the ribosome were selected and comparisons were made with 2.31 and 1.6 .86 The overlap coefficients of the probability distribution were compared for each of the desmethyl analog with respect to the parent telithromycin (Table 3.1).

Table 3.1 Comparison of Overlap Coefficient of 2.31 , 2.32 with TEL

Overlap Coefficient vs. TEL A B C D

C4,8,10tridesmethyl ( 2.31 ) 0.35 0.27 0.45 0.69

C4,10tridesmethyl ( 2.32 ) 0.33 0.26 0.57 0.75

Figure 3.2 CSP data of 2.32

N N

O D R O R N 9 Me O 11 B OMe 12 6 Me NMe2 HO Et O O O Me R A 3 C O O Me

From the overlap coefficient, we observed significant changes in the distances of C and D

with the introduction of a methyl group in 2.32 compared to 2.31 . As previously observed

for analog 2.31 , 2.32 also had distributions different from that of telithromycin 1.6 .

However, analog 2.32 had conformations that overlapped with 1.6 . Hence, the data

suggested that 2.31 can bind to the ribosome and exhibit biological activity (Figure

3.3).86,114

Figure 3.3 CSP of 2.31 in Blue and CSP of 2.32 in Red

N N O N O N N N ( )4 ( )4 O O Me N 9 N 9 Me Me O O 11 OMe 11 OMe 12 6 NMe 12 6 Me 2 Me NMe2 HO O Me HO Et O O Et O O O Me 3 3 O O O O Me Me

4,8,10tridesmethyl telithromycin ( 2.31 ) 4,10diidesmethyltelithromycin ( 2.32 )

Blue Red (Figure 3.1)

3.3 Retrosynthetic Plan

The experience gained from the total synthesis of ()4,8,10tridesmethyl telithromycin ( 2.31 ) played a key role in developing a synthetic strategy for the total synthesis of ()4,10didesmethyl telithromycin ( 2.32 ).114

Figure 3.4 Retrosynthesis of 2.32 to install the side chain

N H2N N ( )4 N N O 2.58 N N ( ) O O 4 Me N 8 Me Me 8 O 11 OMe Me 6 12 Me NMe2 HO 11 OMe 5 6 RO 12 NMe 2.32 4 O Me Me 2 Et O O 5 McO 3 Et O 4 O O Me O O 3 O OPG Me R= Methyl Carbonate (Mc) Me 3.1 3.2

Installation of the oxazolidinone side chain by employing Baker’s onepot carbamoylation/intramolecular azaMichael method was successful in our previous endgame. Thus, compound 3.1 would be accessed via this protocol with the C3 protected compound 3.2 and telithromycin side chain 2.58 (Figure 3.4). 70,71,72

Figure 3.5 Retrosynthesis of enone 3.3

O OPG Me Me 10 8 8 Me Me HO OMe PGO OMe NMe Me 2 Me NMe2 McO N McO Et O 4 O O Me Et O 4 OH O Me

N S O OPG O OPG 1.48 Me Me 3.3 3.4

Glycosylation onto the macrolactone was optimized in the total synthesis of 2.31 .

A similar strategy to install the sugar onto the C5 hydroxyl was envisioned where the

glycosylation conditions would be repeated with 3.4 and donor 1.48 , keeping the C3, C

9 and the C12 alcohols protected (Figure 3.5). 114

Since the RCM across the C10,11 bond enabled gram scale synthesis of the macrocycle in the previous synthesis of 2.31 , we planned to employ the same strategy for

Figure 3.6 Retrosynthesis of macrocycle 3.4

OPG O Et Me Me 12 8 8 10 Me Me OH PGO OMe HO OMe HO Me 2.64 Me Me

Et O 4 OH Et O 4 OTES O OTBS OTES TBSO O OTBS O OTBS HO 3 5 Me Me Me MeO Me Me 3.4 3.5 3.6

83 the synthesis of enone 3.5 . Yamaguchi esterification of diol olefin 2.64 with acid 3.6 would permit access to the RCM precursor (Figure 3.6).92 As previously employed, an

Evans syn aldol was planned to fix the stereochemistry at the C2 and C3 positions.

Sharpless asymmetric dihydroxylation onto the olefin in 2.67 was anticipated to give a lactone, via domino dihydroxylation/lactonization of the C6 hydroxyl group. This lactonization enabled the installation of the C8 methyl group earlier in the synthesis

(Figure 3.7).91,92

Figure 3.7 Retrosynthesis of acid 3.6

O OTBS OTES OTES 7 9 5 7 9 5 HO 1 3 OTBS BnO OTBS MeO Me Me MeO Me Me Me 3.6 3.7 OTES 5 6 CO2Me BnO Me BnO Me O Me 3.8 O 2.67

3.4 Forward Synthesis

Initial attempts to introduce the C8 methyl via macrocontrol alkylation were attempted. Still utilized the conformational bias present in medium and large rings to introduce substitutions asymmetrically with good selectivity. This was demonstrated in

Figure 3.8 Structure of enone 3.9

Me 8 Me O OH Me Me O O 4 O Me (+)3Deoxyrosaronolide ( 3.9)

84 the synthesis of (+)3Deoxyrosaronolide ( 3.9) (Figure 3.8). The C8 methyl group was introduced via macrocylic stereocontrolled methylation. 114 Specifically, the C8 methyl

was introduced by treating enone 3.10 with KHMDS followed by MeI, giving 3.11 in

70% yield with >20:1 diastereoselectivity (Scheme 3.1). 114

Scheme 3.1 Macrocyclic stereocontrolled methylation

O O Me 8 1) KHMDS 8 2) MeI Me Me THF -78 to -20 °C S S Me Me O 70% O 4 S 4 S O O Me 3.10 Me 3.11

Using these results as good precedent, we employed LDA as the base. When 3.12 was treated with LDA/MeI conditions, we could isolate low yields (~30%) of C8 methylated compound with poor diastereoselectivity (Scheme 3.2).

Scheme 3.2 Macrocyclic methylation of 3.12

1) LDA Me 2) MeI TMSO OMe THF -78to - -20 C ° 6 Me 5 Mixture of isomers + Starting Material Et O OPG 3 O OPG Me

3.12

This result, led us to the installation of the C8 methyl group at an early stage in the synthesis. Towards this end, Sharpless dihydroxylation with AD mixβ onto the enoate

2.72 gave the five membered lactone 3.13 with the establishment of the requisite

stereochemistry of hydroxyls at C5 and C6 in 85% yield (er>20:1) (Scheme3.3). The C

5 alcohol was protected as its triethylsilyl (TES) ether 3.14 in 90% yield. 114

Scheme 3.3 Synthesis of lactone 3.8 with the C8 methyl

OH OTES AD - mix β 5 6 TESCl, imidazole 5 6 CO2Me BnO BnO BnO 85% Me 90% Me Me O O dr : > 20;1 2.72 3.13 O 3.14 O

1) LDA, MeI OTES 2) LDA, (H3C)3CCOOH 5 6 BnO Me 60% Me O 3.8 O

Introduction of the C8 methyl was accomplished using LDA mediated methylation of the lactone 3.14 followed by epimerization to obtain the desired

stereochemistry. Treatment of lactone 3.14 with LDA followed by MeI furnished the C8

methyl, cis to the C6 methyl group due to the presence of a bulky C5TES group. Thus,

epimerization was needed to match the stereochemistry of the C8 methyl group to that in

the final analog 2.32 . Thus, epimerization of the newly generated stereocenter was

Scheme 3.4 Xray structure of 3.15

CF3 Ph OMe

OTES 1) TBAF, THF O O 5 2) DCC, R-MTPA, DMAP 6 5 BnO Me 6 BnO Me Me O 60% Me O O O 3.8 3.15

achieved via enolization with LDA followed by protonation with pivalic acid conditions

giving the correct diasteromer 3.8 as the methylated lactone in 60% yield over two steps. 116 The absolute configuration of the C8 methyl group was confirmed by the xray crystal structure of lactone 3.15 , which was obtained by treating 3.8 with TBAF and

86 converting the C5 alcohol into a Mosher ester giving 3.15 as a solid in 60% yield over

97,102 two steps (Scheme 3.4). Recrystallization of 3.8 from Et 2O by slow evaporation

resulted in crystals suitable for xray analysis. The synthesis was carried forward with the

confirmation of 8Rabsolute configuration of the C8 methyl group.

Further steps in the synthesis were guided by the previous synthesis of

o tridesmethyl analog 2.31 . Reduction of the lactone 3.8 with LiAlH 4 in THF at 45 C

followed by protection of the newly formed alcohol as its tert butyldimethylsilyl (TBS) ether provided the C9 TBS ether 3.16 in 78% yield over two steps.

Scheme 3.5 Synthesis of C6 OMe 3.7 with the C8 methyl

OTES 1) LiAlH4, THF OTES TBSO 2) TBSCl, imidazole 5 6 6 Me 5 BnO BnO Me O HO Me 78% Me O 3.8 3.16

OTES TBSO OTES TBSO TABLE 6 5 6 BnO 5 BnO HO Me Me MeO Me Me

3.16 3.7

Methylation of the tertiary C6 alcohol needed optimization as Me 3OBF 4 and

Proton Sponge conditions gave only 35% yield of the methylated product 3.7. Different neutral conditions were attempted keeping the migration issue in mind (Table 3.1). 117

Treatment of 3.16 with MeOTf and 2,6DTBMP, which was previously used by Evans in the total synthesis of callipetoside A gave 80% yield of the methylated product 3.7 .118

This protocol involved the use of 15 equivalents of 2,6DTBMP and 10 equivalents of

MeOTf. The use of such substantial amounts of reagents was not economically feasible for the synthesis of intermediate 3.7 in large scales.118

Table 3.2 Optimization of C6 Omethylation

Condition Reagents Yeild

1 Proton Sponge, Me 3OBF 4 35% (3 Eqv) (3 Eqv) 2 Proton Sponge, Me 3OBF 4 38% (5 Eqv) (5 Eqv) 3 Proton Sponge, Me3OBF 4, 4 Å MS 42% (3 Eqv) (3 Eqv) 4 2,6DTBMP, MeOTf 82% (15 Eqv) (10 Eqv) 5 2,6DTBMP, MeOTf 66% (7.25 Eqv) (7.25 Eqv) 6 2,6DTBMP, MeOTf 60% (5 Eqv) (5 Eqv) 7 2,6-DTBMP, MeOTf 76% (10 Eqv) (6 Eqv)

As an alternative, 2,6DTBMP was substituted with other bases such as 2,6lutidine,

Proton Sponge, DMAP, collidine and 2,4,6tritertbutyl pyrimidine as the acid scavengers, but all these bases were inferior compared to 2,6DTBMP. 119 Secondly, the equivalents

of base 2,6DTBMP and MeOTf were altered until the reaction was optimized (Table

3.2). During these experiments we realized that a small change in the workup procedure

helped in recovering pure 2,6DTBMP base quantitatively. Now, a batch of 25g (costing

$478) of 2,6DTBMP base is used in sequential batches, enabling us to both scale up and

complete the total synthesis of ()4,10didesmethyl telithromycin ( 2.32 ). The same

recovered base is currently being used in the synthesis of 4desmethyl telithromycin

(2.34 ). With the best optimized condition (7) giving 76% yield of 3.7, subsequent steps

were carried through. Hydrogenolysis of the benzyl ether 3.7 afforded the alcohol 3.17 in

80% yield (Scheme 3.6).99,114 (We took the same precautions had to be followed as specified in chapter 2). Swern oxidation furnished aldehyde 3.18, which was subjected to

88 an Evans aldol reaction with 2.81 to set the stereochemistry at the C2 and C3 positions.

It is important to purify the aldol product immediately after the reaction. The desired

aldol product 3.19 was obtained in 78% yield furnishing the C2,3 stereocenters

Scheme 3.6 Synthesis of acid 3.6

OTES TBSO OTES TBSO H , Pd/C (COCl)2, DMSO, Et3N 6 2 6 BnO 5 HO 5 MeO Me Me 80% MeO Me Me 3.7 3.17

O O O O OH OTES TBSO OTES TBSO Me Bu2BOTf, Et3N OHC + O N O 3 5 5 N 76% (2 steps) Me MeO Me Me MeO Me Me Bn Bn dr> 20:1 3.18 2.81 3.19

O O OH OTES TBSO 1) TBSOTf, 2,6-lutidine O OTBS OTES TBSO 2) LiOOH, THF, H2O, O N 3 5 HO 3 5 88% (2 steps) Me MeO Me Me Me MeO Me Me Bn 3.19 3.6

in >20:1 dr over two steps.99,114 Protection of the C3 hydroxyl with TBSOTf and removal of the auxiliary furnished acid 3.6 in 88% yield over two steps (Scheme 3.6).92

Chemoselective Yamaguchi esterification of 3.6 with the diol 2.64 afforded ester

3.20 in 78% yield. 92 Poor selectivity was observed when the C9 primary TBS ether of

ester 3.20 was deprotected with TBAF and AcOH yielding the C9 alcohol 3.21 in 20%

114 yield, unlike 65% in the synthesis of 2.31 . Other procedures such as NH 4F, PPTS and pTsOH didn’t afford good selectivity between the C9 and C5 silyl ethers. 102 Two alternative procedures for scaleup were developed based on the results published by

Shiina and coworkers in 2008. 120 Shiina demonstrated that a primary TES ether can be

89 selectively deprotected in the presence of a secondary TES ether in 95% yield in the total synthesis of Botcinic acid. 120

Scheme 3.7 Synthesis of ester 3.21

Et OH HO Me 2.64 Et O OTBS OTES TBSO O OTBS OTES TBSO Cl PhCOCl, Et N, DMAP 3 3 2.64 3 5 HO 3 5 O HO Me MeO Me Me MeO Me Me 78% Me Me 3.6 3.20

Et O OTBS OTES TBSO Et O OTBS OTES HO TBAF, AcOH 3 5 O 3 5 O 20% HO Me MeO Me HO Me Me MeO Me Me Me Me 3.20 3.21

This reference inspired us to swap the C9 TBS to C9 TES ether and repeat

Shiina’s condition for accessing the C9 alcohol 3.21 . Along these lines, both the C5

TES and the C9 TBS were deprotected using CSA in MeOH, and the corresponding alcohols were protected as the TES ether using TESCl, imidazole, DMAP in DMF giving

3.22 in 65% yield over two steps (Scheme 3.81). Treatment of 3.22 with PPTS in

Scheme 3.81 Alternative method to synthesize 3.21

Et O OTBS OTES TBSO Et O OTBS OTES HO O 3 5 O 3 5 HO Me Me MeO Me Me HO Me Me MeO Me Me 3.20 3.21

1) CSA, MeOH PPTS, MeOH/DCM 2) TESCl, imidazole Et O OTBS OTES TESO 85% 65% O 3 5 HO Me Me MeO Me Me 3.22

DCM/MeOH at 20 oC gave the C9 alcohol 3.21 in 85% yield. 120 As a second alternative the C9 TES introduced earlier in the synthesis of ester 3.22 , which enabled to access

90 larger amounts of compound 3.21 . The C3 TBS protected aldol compound 3.23 was

treated with CSA in MeOH to provide the C9, C5 alcohols, which were treated with

Scheme 3.82 Optimized synthesis of fragment 3.22

Et O OTBS OTES TESO O O OTBS OTES TBSO O 3 5 O 3 5 N HO Me Me MeO Me Me Me MeO Me Me Bn 3.23 3.22 1) CSA, MeOH Cl3PhCOCl, Et3N, DMAP 2) TESCl, imidazole 2.64 76% 76%

O OTBS OTES TESO O O OTBS OTES TESO LiOOH, THF,H2O HO 3 5 O N 3 5 85% Me MeO Me Me Me MeO Me Me Bn 3.24 3.25

TESCl, Imidazole and DMAP in DMF giving 3.24 in 76% yield over two steps (Scheme

3.82). Treatment of 3.24 with LiOOH in THF/H 2O led to the removal of the auxiliary

yielding acid 3.25 in 85% yield. Chemoselective Yamaguchi esterification of 3.25 with the diol olefin 2.64 afforded ester 3.22 in 76% yield. 92 This alternative procedure allowed

Scheme 3.9 Synthesis of macrocycle 3.5

OH O Me Me Me Me 1) DMP, NaHCO3 HO OMe 2) vinyl MgBr, THF HO OMe 6 6 Me 3) DMP, Me 20 mol% Grubbs II cat. 5 5 Et O OTES Et O OTES 56% (3 steps) 60% O OTBS O OTBS 90% (borsm) Me Me 3.21 3.26 O Me Me HO OMe 6 Me 5 Et O OTES 3 O OTBS Me 3.5

91 us to access the C9 alcohol 3.21 in large amounts (3 g). With large quantities of 3.21 in

hand, efforts were directed to employ the ringclosing metathesis (RCM) strategy.92 The

C9 alcohol was oxidized to the aldehyde with DMP (Scheme 3.9). Addition of

vinylmagnesium bromide and subsequent DMP oxidation afforded vinyl ketone 3.26 in

56% overall yield. Treatment of dienone 3.26 with 20 mol% Grubbs’ Second Generation catalyst affected the desired RCM, affording macroketolactone 3.5 in 90% yield (borsm),

similar to the synthesis of macrolactone 2.120 .92,114 With enough quantity of macrocycle

in hand, the next step was to install desosamine onto the C5 alcohol. It was unavoidable

to keep the C3, C9 and the C12 hydroxyls unprotected for the glycosylation to occur

exclusively onto the C5 hydroxyl. Chemoselective deprotection of the C5 TES led to

Scheme 3.10 Synthesis of C5 sugar 3.28

O OH

Me Me

Me 1) NaBH4, CeCl37H2O, Me HO OMe 2) TESOTf, 2,6-lutidine TESO 11 OMe 1) TESCl, imidazole 6 3) PTSA, MeOH Me Me 12 2) 1.48, AgOTf, DTBMP 5 5 Et O OTES Et O OH 36% (3 steps) 50% (2 steps) 3 dr= 5:2 3 O OTBS O OTBS Me Me 3.5 3.27 OTES Me 8 Me TESO OMe Me NMe2 McO Et O 4 O O Me

O OTBS Me 3.28

ketalization with the C9 ketone. Thus, the C9 carbonyl of the enone 3.5 was reduced using Luche reduction conditions to give a 5:2 diasteromeric mixture of the C9 alcohols.

Silylation of C9 and C12 hydroxyls with TESOTf and subsequent treatment with p

92 toluenesulfonic acid (pTsOH) selectively deprotected the C5 and the C9 TES ethers leaving the C12 TES ether protected compound 3.27 in 30% yield over three steps.

Decreased selectivity was observed when PTSA was used for the deprotection of the C9

TES over the C12 TES with the introduction of the C8 methyl group. 121 Chemoselective silylation of the C9 allylic alcohol with TESCl, followed by the treatment with AgOTf,

2,6DTBMP and the desosamine donor 1.48 gave the C5 glycosylated product 3.28 in

50% yield over two steps. (1M in THF) TBAF was not selective for the deprotection of

114 the C9 and C12 TES ethers over the C3 TBS. Treatment of 3.28 with HF•3Et 3N

gave the C9, 12 alcohol in 78% yield. 102 DMP oxidation of the allylic alcohol furnished

the enone with sugar 3.29 in 56% yield over two steps (Scheme 3.11). This compound

was fully characterized using 2DNMR experiments (See Appendix).

Scheme 3.11 Synthesis of enone with sugar 3.29

OTES O Me 8 Me Me 8 TESO OMe 1) HF Et3N Me 2) DMP HO OMe Me NMe2 McO Me NMe2 Et O 4 O O Me McO 56% Et O 4 O O Me

O OTBS O OTBS Me Me 3.28 3.29

Introduction of the oxazolidinone across the C11,12 double bond was optimized in the synthesis of 2.31. Thus, similar conditions were employed where activation of the

C12 hydroxyl of 3.29 under the conditions of NaH/CDI and subsequent treatment with primary amine 2.58 effected Baker’s tandem carbamoylation/intramolecular azaMichael sequence to stereoselectively afford oxazolidinone 3.30 in 45% overall yield. 70,71,72,114

Scheme 3.12 Installation of side chain: 3.30 N O O N N ( )4 Me O Me 8 N 10 8 Me Me O HO OMe 1) NaH, CDI, THF/DMF OMe NMe Me NMe2 2) 2.58, CH3CN/H2O Me 2 McO McO 4 Et O 4 O O Me Et O O O Me 45% over 2 steps

O OTBS O OTBS Me Me 3.29 3.30

N N NH2 2.58 4

Removal of the C3 TBS ether with tris(dimethylamino)sulfonium difluoro trimethylsilicate (TASF) yielded the C3 alcohol 3.31 in 70% yield. 109,114 CoreyKim oxidation of the C3 alcohol 3.31 furnished the C3 keto 3.32 in 75% yield. 108,114 Finally deprotection of the methyl carbonate on the C2ˈ position of desosamine delivered ()

4,10diidesmethyl telithromycin ( 2.32 ) in 80% yield. 114

Scheme 3.13 The end game for the synthesis of 2.32

N N O O N N N N ( ) ( )4 4 Me O Me O N 10 8 N 10 8 Me Me O O OMe OMe TASF, DMF/H O NMe Me NMe2 2 Me 2 McO McO 4 O Me Et O 4 O O Me 70% Et O O

O OTBS O OH

Me Me 3.30 3.31

N N O O N N N ( ) N ( ) 4 4 Me O Me O N 10 8 N 10 8 Me Me O OMe O OMe NCS, DMS, Et N 3 Me NMe2 MeOH Me NMe2 McO HO Et O 4 O O Me Et O 4 O O Me 75% 80%

O O O O

Me Me

3.32 2.32

3.5 Biological Evaluation of (-)-4,10-didesmethyl telithromycin

Biological evaluation of analog ()4,10didesmethyl telithromycin ( 2.32 ) was

again accomplished in collaboration with the Mankin lab. Analog 2.32 was tested against several bacterial strains of Escherichia coli and Staphylococcus aureus using telithromycin ( 1.6 ) as the baseline in DMSO solution. The MIC data was compared with the data of ()4,8,10tridesmethyl telithromycin (2.31 ), which was already tested. 111,114

(Table 3.3 shows the minimum inhibitory concentration (MIC) values in g/mL for ()

4,8,10tridesmethyl analogue ( 2.31 ) in EtOH, ()4,10didesmethyl analogue (2.32 ) in

DMSO and telithromycin ( 1.6 ). The data showed both resistant strains (entries 1 and 5)

were not susceptible to the three macrolides 1.6, 2.31 and 2.32 . The strains of E. coli

wildtype and A2058G mutant (entries 2 and 3) were inhibited by 2.32 , 2.31 and

telithromycin ( 1.6 ). In these strains, the 4,10didesmethyl analogue 2.32 was four-fold more potent than 4,8,10tridesmethyl analogue 2.31 . Compared to telithromycin ( 1.6 ), the

new analogue was sixteenfold less potent. The differences in entries 2 and 3 demonstrate

the difference in conformational flexibility of 2.32 over 2.31 with the introduction of a

methyl group at the C8 position. Interestingly, 2.32 did not

Table 3.3 MIC data of 2.32 with 2.31 and 1.6 as the baseline

Entry Strain Bacteria wt/mutant MIC (2.31) MIC (2.32) MIC (1.6) 1 SQ171/2058G E. coli A2058G >512 >512 >512 2 DK/pKK3535 E. coli wt 32 8 0.5 3 DK/2058G E. coli A2058G 64 16 1 S. aureus 4 UCN14 A2058T 32 >256 >128 5 ATCC33591 S. aureus ermA >128 >128 >128

bind onto the UCN14 strain with an A2058T mutant as compared to 2.31 . The decrease

in the biological data of 2.32 compared with telithromycin ( 1.6 ) is likely due to the loss

95 of van der Waals contacts at C4 and C10 positions. Significantly the biological evaluation data clearly demonstrated that the introduction of a C8 methyl group caused conformational changes in the molecule that influenced the biological activity of the analog. 122

To summarize, two desmethyl analogs of telithromycin ( 1.6 ), 4,8,10 tridesmethyl telithromycin ( 2.31) and 4,10didesmethyl telithromycin ( 2.32 ) were synthesized using RCM macrocyclization approach. The former was also prepared by

NHK macrocyclization. Analog 4,10didesmethyl telithromycin ( 2.32 ) was synthesized in 24 operations (44 steps overall, 32 steps in the longest linear sequence) with a total of

20 mg being synthesized in sequential batches. This analog was found to inhibit bacterial growth and was more potent than 4,8,10tridesmethyl telithromycin against an A2058G mutant. 114,122

CHAPTER 4: Progress Towards the Synthesis 4-Desmethyl Telithromycin

4.1 Introduction

The biological evaluation of (-)-4,8,10-tridesmethyl telithromycin ( 2.31) and (-)-

4,10-didesmethyl telithromycin ( 2.32 ) supported the notion that van der Waals

interactions of the methyl groups on the macrolactone play an important role in binding. 114,121 The conclusion to the desmethylation strategy can be summarized with the synthesis and the biological evaluation of 4-desmethyl telithromycin ( 2.34 ) which is the least modified scaffold (Figure 4.1). Efforts towards the synthesis of 4-desmethyl telithromycin (2.34 ) via RCM approach to synthesize the least modified macroketolactone are discussed in this chapter.

Figure 4.1 Structure of 4-desmethyl telithromycin

N O N N ( )4 O Me Me N 10 8 Me O OMe Me NMe2 HO Et O 4 O O Me

O O

Me 4-desmethyl telithromycin ( 2.34 )

4.2 Retrosynthetic Plan

Since the endgame towards the synthesis of these analogs was thoroughly optimized, our initial effort was to employ the RCM macrocyclization in presence of the

C-10 methyl. To access macrolactoketone 4.1 we envisioned the use of RCM macrocyclization at the C-10, 11 and C-11, 12 on two model substrates 4.2 and 4.3 . We

97 predicted that the optimized RCM method would work in the presence of the C-8 methyl group. Grignard addition of 2-bromopropene on to the C-9 aldehyde followed by DMP oxidation would help in accessing the RCM model precursor 4.2 (Figure 4.2).123

Figure 4.2 Strategy for RCM across C-10,11 with the C-10 methyl

O O OH

Me Me Me Me 10 10 RCM Me Me RCM Me HO OMe HO OMe Me OMe Me 6 Me 6 6 5 5 5 Et O OPG Et O OPG Et O OPG 3 3 3 O OPG O OPG O PG

Me Me Me

4.1 Model Substrate 4.2 Model Substrate 4.3

No successful macrocyclization occurred across the C-10, 11 bond under RCM conditions with the introduction of the C-10 methyl group. Alternate procedures such as changing the solvent (CH 2Cl 2, toluene), concentration, temperature (40 to 120 ºC) and metathesis catalyst did not yield any cylclized product (Figure 4.3). We predicted that the steric hindrance caused by the C-10 methyl group was preventing the catalyst to react with the olefin partner to initiate the cyclization. Further, RCM across the C-12, 13 bond led to isomerization of the olefins but no successful cyclization occurred. 123

Figure 4.3 RCM catalyst used

Me Me MesN NMes MesN NMes N N Cl Cl N N Cl Ru Ru Cl Me Ru Cl Cl Ph Me Ru Cl PCy i-PrO Cl Ph 3 i-PrO PCy3

G-II 2.107 GH-II 2.108 MG-II 2.1071 MGH-II 2.1081

G-II: Grubbs-II, GH-II: Grubbs Hoveyda-II, MG-II: Modified Grubbs-II, Modified Grubbs Hoveyda--II

4.3 Present Study

NHK macrocyclization, for the total synthesis of 4,8-didesmethyl telithromycin

(2.33 ) afforded a yield of 20% over two steps for the macrocyclization in the presence of

Figure 4.4 NHK cyclization with the C-10methyl and C-5 sugar

Me I CHO Me 8 8 Me Me 1) NHK Cyclization HO HO OMe 2) DMP OMe Me Me 20% 4 Et O 4 OR Et O OR

O OTBS O OTBS Me 4.4 Me 4.5 NMe2 McO O Me PG= TES, Des = O

the C-10 methyl group. More importantly this cyclization worked in the presence the C-5 amino sugar saving significant amount of steps in the total synthesis (Figure 4.4). 124 The

present study includes the validation of the NHK macrocyclization strategy towards the

synthesis of 4-desmethyl telithromycin ( 2.34) having both the C-10 and the C-8 methyl

groups.

Chemoselective Yamaguchi esterification of 3.6 with the diol 4.6 afforded ester

4.7 in 72% yield. 121 The C-9 alcohol was accessed following the strategy adopted from the synthesis of 2.32 . The C-5 and C-9 silyl ethers were swapped to their corresponding

TES ethers and treated with PPTS in CH 2Cl 2/MeOH at -20 ºC to afford the C-9 alcohol

4.8 in 30% yield over three steps. 120 DMP oxidation furnished the aldehyde which on

treating with CrCl 2, NiCl 2 in DMSO followed by allylic oxidation gave a 3:1 mixture of

diasteromers in modest yields ranging from 5-10% (Scheme 4.1). (epimerization at C-2

or the C-8 methyl position). 121

Scheme 4.1 Synthesis of C-4 desmethyl macrocycle 4.9

OTBS OTBS Me Me 1) CSA, MeOH Me Me Cl3PhCOCl, Et3N, DMAP 2) TESCl, Imidaole, DMAP OMe HO I OMe 6 4.6 3) PPTS, MeOH Me 6 5 Me 5 72% 30% OH OTES Et O OTES 3 3 O OTBS O OTBS Me I Me Me 3.6 4.7 HO OH O Me 4.6 Me Me Me Et OH Me 1) DMP Me HO HO I OMe 2) CrCl2, NiCl2 OMe 3) DMP 6 Me 6 Me Me 5 5 5 to 10% Et O OTES Et O OTES 3 3 O OTBS O OTBS Me Me

4.8 4.9

To test the NHK cyclization in presence of the C-5 desosamine sugar, the auxiliary in the aldol product was swapped to a benzyl ester by treating with lithium benzyloxide (Scheme 4.2). 125 The C-5 and C-9 silyl ether was deprotected by CSA to afford the diol 4.11 in 70% yield. The C-9 alcohol was protected as TBS ether and the

Scheme 4.2 Synthesis of NHK fragment 4.13 OH OTBS OTBS Me Me Me Me Me Me OMe OMe 1) TBSOTf, 2,6lutidine OMe 6 6 PTSA, MeOH 2) BnOLi 6 5 5 5 OTES 70% OBn OH O O 50% OBn OTES 3 3 3 N OH O OTBS O O OTBS Me Me Me Bn 3.5 4.10 4.11 OTBS OTBS Me Me 1) TBSCl, Imidazole Me 2) 1.48, AgOTf, 2,6-DTBMP Me 1) H2/Pd-C HO I OMe 2)Cl PhCOCl, Et N, DMAP 6 OMe 3 3 Me 6 Me 5 55% Over 2 Steps 5 Et O ODes 70% Over 2 Steps NMe2 OBn ODes 3 McO 3 O O Me O OTBS Des = O OTBS Me Me 4.12 4.13

100

C-5 alcohol was treated with AgOTf, 2,6-DTBMP and the donor 1.48 to furnish the

glycosylated compound 4.12 in 55% yield over two steps. 121 Hydrogenolysis of the benzyl ester followed by chemoselective esterification with diol 4.6 yielded ester 4.13 in

70% over two steps.

The C-9 TBS ether was deprotected using HF•pyridine to yield the C-9 alcohol in

80% yield. Unfortunately, no cyclization occurred upon treatment of 4.14 with DMP followed by CrCl 2, NiCl 2 in DMSO. Reduction of both the vinyl Iodide and the C-9 aldehyde was observed with no macrocyclization (Scheme 4.3). 100

Scheme 4.3 Unsuccessful NHK cyclization of 4.15

OTBS OH Me Me Me Me 1) DMP HO HF.Pyr HO I OMe I OMe 2) CrCl2, NiCl2, DMSO 6 6 Me Me Me 5 Me 5 x Et O ODes 80% Et O ODes 3 3 O OTBS O OTBS Me Me

4.14 4.15

To summarize, both the macrocyclization methods across the C-9, 10 (NHK) and C-11,

10 (RCM) bonds were unsuccessful for the total synthesis of 4-desmethyl telithromycin

(2.34 ).

101

CHAPTER 5

EXPERIMENTAL SECTION

5.1 General Methods

All reactions containing moisture or air sensitive reagents were performed in ovendried glassware under nitrogen or argon. Dimethylformamide, tetrahydrofuran, toluene and dichloromethane were passed through two columns of neutral alumina. Pyridine, 2,6 lutidine, acetone, iPr 2NEt, Et 3N were all distilled from CaH 2 prior to use. Molecular sieves (4Å) were activated by flame drying under vacuum prior to use. AgOTf was azeotroped with dry toluene. All other reagents were purchased from commercial sources and used without further purification. All solvents for workup procedures were used as received. Flash column chromatography was performed according to the procedure of

Still using ICN Silitech 3263 D 60Å silica gel with the indicated solvents.126 TBAF solution (1 M in THF) was prepared by adding 4Å molecular sieves (1gm/mL) to a solution of TBAF•3H 2O in THF and stirred for 4h. For NHK reactions DMSO was distilled under vacuum using CaH 2 and the solution was freeze pump thawed. CrCl 2

(Strem) and NiCl 2 (Sigma) were weighed in glove box. For all RCM reactions, CH 2Cl 2 was deaereated by bubbling argon (1 min/mL). Thin layer chromatography was performed on Analtech 60F 254 silica gel plates. Detection was performed using UV light,

1 13 KMnO 4 stain, PMA stain and subsequent heating. H and C NMR spectra were recorded at the indicated field strength in CDCl 3 at rt. Chemical shifts are indicated in parts per million (ppm) downfield from tetramethylsilane (TMS, δ = 0.00) and referenced

102

to the CDCl 3. Splitting patterns are abbreviated as follows: s (singlet), d (doublet), t

(triplet), q (quartet) and m (multiplet).

Melting points were recorded on a MelTemp apparatus. Optical rotations were measured on a PerkinElmer 341 polarimeter. Infrared spectra were recorded on a Perkin

Elmer 1600 FTIR spectrometer using NaCl plates for liquids and ATRFTIR spectra were taken on a single bounce smart orbit diamond ATR accessory mounted in a Nicolet

Magna 750 FTIR spectrometer Thermo Scientific that was equipped with a deuterium tryglycine sulfate (DTGS) detector. High resolution mass spectrometry was collected at

Department of Chemistry, University of Pennsylvania and Ohio State University Mass

Spectrometry Facilities. Xray crystal structure analysis was performed at Department of

Chemistry, University of Pennsylvania.

103

5.2 CHAPTER 1: Concise Syntheses of D-Desosamine, 2-Thiopyrimidinyl

Desosamine Donors and Methyl Desosaminide Analogues from D-Glucose

Cl Cl Methyl 4,6dideoxy4,6dichloroαDgalactopyranoside ( 1.59 ): Methyl O HO αDglucopyranoside 1.55 (1.0 g, 5.14 mmol) was dissolved in pyridine HO 1.59 OMe (6 mL) and chloroform (6 mL). Sulfuryl chloride (3.35 g, 41.2 mmol)

was added dropwise over 30 min at −78 ◦C. The reaction mixture was stirred for 2 h at this temperature, and the mixture was warmed to rt. The reaction mixture was heated to

50 ◦C and stirred for 5 h. After cooling to rt, the solution was diluted with MeOH (3 mL) and water (3 mL) and subsequently neutralized by slow addition of solid Na 2CO 3. To this mixture was added a solution of NaI (0.38 g, 2.54 mmol) in H 2O/MeOH (2 mL, 1:1),

and the reaction mixture was stirred an additional 5 min. The resulting solution was

coevaporated with toluene (2 x 12 mL) and concentrated under reduced pressure. The

solid was recrystallized from chloroform to afford 0.65 g (55%) of 1.59. Spectral data of

1.59 matched those reported in reference 24(b).

Methyl 4,6dideoxyαDxylo hexopyranoside ( 1.60 ): To a solution Me O HO of KOH (0.90 g, 16.1 mmol) in EtOH (10 ml) was added 1.59 (1.0 g, HO 1.60 OMe 4.33 mmol). The reaction mixture was stirred at rt under a H 2 atmosphere in presence of NiRaney (4.6 g) for 12 h. The reaction mixture was filtered through a bed of Celite (making sure to keep the filter cake moist) and quenched with an aqueous solution of 10% HCl (25 mL). The solution was then taken up in hot CHCl 3 (50

mL) . The solvent was removed under reduced pressure, and the residue was purified by 104

flash column chromatography eluting with CH 2Cl 2/acetone (70:30) to afford 0.57 g of

1.60 (82%) as a white solid. Spectral data of 1.60 matched those reported in reference

15.

Me Methyl 2,3anhydro4,6dideoxyαDribo hexopyranoside ( 1.45 ): PPh 3 O

O (1.06 g, 4.06 mmol) and DEAD (0.70 g, 4.06 mmol) were added to a 1.45 OMe solution of 1.60 (0.6 g, 3.69 mmol) in benzene (36 mL) containing 4 Å molecular sieves (1.0 g). The reaction mixture was refluxed for 24 h and cooled to rt.

The reaction mixture was concentrated under reduced pressure and purified by bulbto bulb distillation (bp = 140 oC, 18 mmHg) to afford 0.28 g of 1.45 (60%) as a clear liquid.

Spectral data of 1.45 matched those reported in reference 15.

Methyl desosaminide ( 1.61 ): Dimethylamine (2 mL, 40% in H 2O) Me O Me2N was added to a solution of 1.45 (70 mg, 0.56 mmol) in EtOH (2.3 HO 1.61 OMe mL) and stirred for 60 h at rt. The reaction mixture was concentrated under reduced pressure, and the residue was purified by flash column chromatography eluting with MeOH/CH 2Cl 2/Et 3N (10:85:5) to afford 80 mg (76%) of

1.61 as a colorless oil. Spectral data of 1.61 matched those reported in reference 13.

Me DDesosamine (1.1 ): To a solution of 1.61 (110 mg, 0.58 mmol) O Me2N HO OH in EtOH (5 mL) was added 6 N HCl (3 mL). The reaction mixture 1.1 was refluxed for 4 h, cooled to rt and concentrated under reduced pressure. The residue was dissolved in MeOH (2 mL) and passed through a small column

105

of Amberlyst A26 resin (200 mg, OH form) to afford 75 mg (74%) of 1.1 as yellow oil.

Spectral data of 1.1 matched those reported in reference 7c.

1(2Pyrimidinethio)3,4,6trideoxy3(dimethylamino)D Me O N Me2N xylo hexopyranoside ( 1.62 ): Diethylazidodicarboxylate (59 HO S N 1.62 mg, 0.34 mmol) was added to a solution of trin butylphosphine (69 mg, 0.34 mmol) in toluene (1.5 mL) at 40 ◦ C and stirred for 20 min at this temperature. A solution of 1.1 (50 mg, 0.28 mmol) in toluene (1.5 mL) was added rapidly. After 45 min, solid 2mercaptopyrimidine (38.1 mg, 0.34 mmol) was added. The cooling bath was removed, and the reaction mixture was stirred for 15 h. The reaction mixture was filtered and concentrated under reduced pressure. The residue was purified by flash column chromatography eluting with EtOAc/hexanes/Et 3N (75:20:5) to afford 48 mg (64%) of 1.62 as a yellow oil. Spectral data of 1.62 matched those reported in reference 26.

Me 1(2Pyrimidinethio)3,4,6trideoxy2Omethoxycarbonyl3 O N Me2N (dimethylamino)Dxylo hexopyranoside ( 1.48 ): Methyl S N MeO2CO 1.48 chloroformate (21 mg, 0.22 mmol) was added to a solution of

1.62 (50 mg, 0.18 mmol) in THF (1 mL) and saturated aq NaHCO 3 (1 mL) at rt. After 15

min the reaction was diluted with EtOAc (10 mL) and washed with water (5 mL). The

layers were separated and the aqueous phase was extracted with EtOAc (2 x 5 mL). The

combined organic phases were dried over Na 2SO 4, filtered and concentrated under

reduced pressure. The residue was purified by flash column chromatography eluting with

106

EtOAc/hexanes/Et 3N (60:35:5) to afford 48 mg (82%) of 1.48 as a yellow oil. Spectral data of 1.48 matched those reported in reference 16.

1(2Pyrimidinethio)3,4,6trideoxy2Oacetyl3 Me O N Me2N (dimethylamino)Dxylo hexopyranoside ( 1.49 ): Acetic AcO S N 1.49 anhydride (22 mg, 0.22 mmol) was added to a solution of

10 (50 mg, 0.18 mmol) and Et 3N (22 mg, 0.22 mmol) in CH 2Cl 2 (2 mL) at rt and stirred for 12 h. The reaction mixture was diluted with CH 2Cl 2 (10 mL) and washed with 5% aq

NaHCO 3 (5 mL) and brine (5 mL). The combined aqueous layers were backextracted with CH 2Cl 2 (5 mL). The combined organic phases were dried over Na 2SO 4, filtered and

concentrated under reduced pressure. The residue was purified by flash column

chromatography eluting with EtOAc/hexanes/Et 3N (70:25:5) to afford 42 mg (76%) of

1.49 as a colorless oil. Spectral data of 1.49 matched those reported in reference 26.

General procedure for the aminolysis of 1.45 with secondary amines:

A solution of 1.45 (1 equiv) in anhydrous EtOH (5 mL) was treated with the secondary

amine, 1.63, 1.65, 1.67 (5.0 equiv) at rt. The reaction mixture was heated to 80 oC and

stirred for 72 h at this temperature. After cooling to rt, the reaction mixture was

concentrated under reduced pressure. The residue was purified by flash column

chromatography eluting with MeOH/CH 2Cl 2/Et 3N (20:75:5) to afford the corresponding

3amino analogues 1.64, 1.66, 1.68 as oils.

107

Methyl3,4,6trideoxy3pyrrolidinoαDxylo hexopyranoside Me O 25 N (1.64 ): Yield = 86%: [α] D +126 ( c 0.1, CHCl 3); IR (neat) HO 1.64 OMe 1 1 3457, 2969, 1272, 1049, 690 cm ; H NMR (CDCl 3) δ 4.81 (d,

J = 3.6 Hz, 1H), 3.88 (m, 1H), 3.53 (dd, J = 10.8, 3.6 Hz, 1H), 3.36 (s, 3H), 3.05 (td, J

=10.8, 4.0 Hz, 1H), 2.61 (m, 4H), 1.75 (m, 5H), 1.31 (m, 1H), 1.18 (d, J = 6.0 Hz, 1H);

13 C NMR (CDCl 3) 99.9, 70.6, 64.9, 57.2, 55.3, 48.0, 31.2, 23.8, 21.5; HRMS (FAB) calculated for C 11 H22 NO 3 (M + H) 216.1599; observed 216.1595.

Me Methyl3,4,6trideoxy3piperidinoαDxylohexopyranoside O N 25 HO (1.66 ): Yield = 82%: [α] D +132 ( c 0.1, CHCl 3); IR (neat) 3422, 1.66 OMe 1 1 2967, 1457, 1272, 1090, 1048 cm ; H NMR (CDCl 3) δ 4.84 (d,

J = 3.6Hz, 1H) , 3.86 (m, 1H), 3.55 (dd, J = 10.8, 3.6 Hz, 1H), 3.41 (s, 3H), 2.89 (td, J

=10.8, 3.6 Hz, 1H), 2.63 (m, 2H), 2.36 (m, 2H), 1.74 (m, 1H), 1.55 (m, 4H), 1.41 (m,

13 2H), 1.21 (m, 1H), 1.15 (d, J = 4.0 Hz, 1H); C NMR (CDCl 3) 99.9, 68.1, 65.3, 61.8,

55.3, 49.8, 31.1, 26.7, 25.0, 21.5; HRMS (FAB) calculated for C 12 H24 NO 3 (M + H)

230.1756; observed 230.1747.

Methyl3,4,6trideoxy3morpholinoαDxylo hexopyranoside Me O O 25 N (1.68 ): Yield = 78%: [α] D + 144 ( c 0.1, CHCl 3); IR (neat) HO OMe 1 1 1.68 3440, 2975, 1641, 1454, 1110, 1043, 674 cm ; H NMR

(CDCl 3) δ 4.86 (d, J = 3.4 Hz, 1H), 3.88 (m, 1H), 3.68 (m, 4H), 3.57 (dd, J = 10.6, 3.4

Hz, 1H), 3.42 (s, 3H), 2.90 (td, J = 10.6, 3.6 Hz, 1H), 2.67 (m, 2H), 2.45 (m, 2H), 1.76

13 (m, 1H), 1.29 (m, 1H), 1.19 (d, J = 6.4 Hz, 1H); C NMR (CDCl 3) 99.7, 68.0, 67.7,

108

65.1, 61.5, 55.3, 48.8, 31.1, 21.5; HRMS (FAB) calculated for C 11 H22 NO 4 (M + H)

232.1549; observed 232.1539.

5.3 CHAPTER 2: Desmethyl Analogs of Telithromycin to Address Antibiotic

Resistance: Synthesis and Biological Evaluation of (-)-4,8,10-Tridesmethyl

Telithromycin

Ester 2.67 : To a solution of oxalyl chloride (10.66 g,

CO2Me ◦ BnO 84.25 mmol) in CH 2Cl 2 (650 mL) at 78 C was added Me 2.67 DMSO (13.71 g, 175.54 mmol) dropwise. After stirring

for 10 min, 3benzyloxy1propanol (11.67 g, 70.21mmol) in CH 2Cl 2 (50 mL) was added via cannula, and the reaction mixture was stirred at78 ◦C for 45 min. Triethylamine

(17.70 g, 175.54 mmol) was then added dropwise, and the reaction mixture was slowly warmed to rt. After 3 h, the reaction was quenched with H 2O (200 mL). The organic layer

was separated and washed with brine (200 mL), dried (Na 2SO 4) and concentrated under reduced pressure. Crude 3benzyloxy1propanal was filtered through a silica plug using ether (200 mL), concentrated and dried under high vacuum, and used directly in the next step. To a twonecked roundbottomed flask fitted with a reflux condenser was added Mg

(3.35 g, 139.85 mmol), iodine (10 mg), and THF (56 mL). 2bromopropene (10.2 g,

84.25 mmol) was added dropwise in portions. After complete addition, the reaction mixture was heated to reflux for 45 min then cooled to rt. To a solution of 3benzyloxy1 propanal in THF (351 mL) at 20 ◦C was added 2propenylmagnesium bromide by cannula. The reaction mixture was stirred for 1 h and quenched by adding sat’d aq.

109

NH 4Cl (150 mL). The reaction mixture was extracted with EtOAc (2 x 300 mL). The combined organic layers were washed with brine (100 mL), dried (Na 2SO 4) and filtered.

The solvent was concentrated under reduced pressure, dried under high vacuum, and dissolved in toluene (145 mL). Trimethyl orthoacetate (33.74 g, 280.84 mmol) and propionic acid (0.26 g, 3.51 mmol) were added, and the reaction mixture was heated at reflux for 36 h. The reaction mixture was concentrated under reduced pressure and purified via flash chromatography eluting with EtOAc/hexanes (1/17) to afford 8.83 g

(48%) of 2.67 as a colorless oil; IR (neat) 1227, 1361, 1438, 1741, 2857 cm 1; 1H NMR

(400 MHz) δ 7.277.19 (m, 5H), 5.13 (m, J = 6.6 Hz, 1H), 4.44 (s, 2H), 3.57 (s, 3H), 3.38

(t, J = 6.8 Hz, 2H), 2.372.23 (m, 6H), 1.56 (s, 3H); 13 C NMR (100 MHz) δ 173.6, 138.4,

135.3, 128.2 (2C), 127.5 (2C), 127.4, 121.1, 72.7, 69.8, 51.3, 34.5, 32.8, 28.5, 15.9;

HRMS (FAB) calc’d for C 16 H22 O3OMe =231.1378, found 231.1385.

OTBS Olefin 2.73 : To a suspension of LiAlH 4 (1.77 g, 46.58

◦ BnO mmol) in Et 2O (250 mL) at 0 C was added ester 2.67 (8.14 Me 2.73 g, 31.05 mmol) dissolved in Et 2O (50 mL) dropwise by cannula. After 10 min, the reaction mixture was diluted with Et 2O (100 mL) and

◦ quenched by adding sat’d aq. Na 2SO 4 (50 mL) dropwise at 0 C. The organic layer was decanted, and the solid was washed with ether (3 x 50 mL). The combined organic layers were washed with brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was

concentrated under reduced pressure, dried under high vacuum, and dissolved in DMF

(150 mL). Imidazole (2.95 g, 43.47 mmol) and TBSCl (5.61 g, 37.26 mmol) were added,

and the reaction mixture was stirred for 16 h. The reaction was quenched with H 2O (150

110

mL) and extracted with Et 2O (4 x 150 mL). The combined organic layers were washed

with H 2O (100 mL), brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was

concentrated under reduced pressure, and the residue was purified by flash

chromatography eluting with EtOAc/hexanes (1/25) to afford 8.43 g (78%) of 2.73 as a colorless oil; IR (neat) 1120, 1251, 1360, 1471, 2871, 2963 cm 1; 1H NMR (400 MHz) δ

7.357.26 (m, 5H), 5.16 (m, 1H), 4.52 (s, 2H), 3.58 (t, J = 6.6 Hz, 2H), 3.45 (t, J = 7.0

Hz, 2H), 2.33 (app q, J = 6.9 Hz, 2H), 2.02 (t, J = 7.6 Hz, 2H), 1.651.58 (m, 5H), 0.89

(s, 9H), 0.04 (s, 6H); 13 C NMR (100 MHz) δ 138.6, 136.9, 128.3 (2C), 127.6 (2C), 127.4,

120.2, 72.8, 70.1, 62.8, 35.8, 31.1, 28.6, 25.9, 18.3 (3C), 16.1, 5.3 (2C); HRMS (FAB)

+ calc’d for C 21 H36 O2Si+H = 349.2563, found 349.2556.

HO TBSO Diol 2.74 : To a suspension of K 3Fe(CN) 6 (28.33 g, 86.06 6 5 BnO mmol), K 2CO 3 (11.90 g, 86.06 mmol), (DHQD) 2PHAL HO Me 2.74

(223mg, 0.28 mmol), K 2OsO 2(OH) 4 (21 mg, 0.057 mmol) in

◦ tBuOH (145 mL) and H 2O (145 mL) at 0 C was added MeSO 2NH 2 (2.75 g, 28.92 mmol). The reaction mixture was stirred at 0 ◦C until the dissolved salts precipitated out.

Olefin 2.73 (10.0 g, 28.97mmol) was then added to the reaction mixture at 0 ◦C and stirred for 36 h at 0 ºC. Sodium sulfite (Na 2SO 3, 43.0 g) was then added to the reaction mixture and stirred an additional hour. The mixture was extracted with EtOAc (3 x 200 mL). The combined organic layers were washed with a 2N aq. KOH (150 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/4) to afford

23 10.08 g (91%) of 2.74 as a colorless oil. [α] D +2.8° (c 7.5, CH 2Cl 2); IR (film) 2950,

111

2879, 1462, 1382, 1255, 1113, 733, 696 cm 1; 1H NMR (400 MHz) δ 7.277.26 (m, 5H),

4.46 (s, 2H), 3.653.55 (m, 5H), 1.681.51 (m, 6H), 1.03 (s, 3H), 0.82 (s, 9H), 0.01 (s,

6H); 13 C NMR (100 MHz) δ 137.9, 128.4 (2C), 127.7, 127.6 (2C), 76.0, 73.6, 73.3, 69.2,

63.9, 35.5, 30.9, 26.7, 25.9 (3C), 21.4, 18.3, 5.4 (2C); HRMS (FAB) calc’d for

+ C21 H38 O4Si+H = 383.2617, found 383.2602.

TBS ether 2.78: To a solution of diol 2.74 (2.5 g, 18.29 MeO TBSO 6 ◦ BnO 5 mmol) in CH 2Cl 2 (30 mL) at 20 C was added 2,6lutidine TBSO Me 2.78 (2.10 g, 19.59 mmol) and TBSOTf (2.07 g, 7.83 mmol).

After 2 h, the reaction was quenched by adding sat’d aq. NaHCO 3 (20 mL). The aqueous

layer was extracted with CH 2Cl 2 (2 x 10 mL). The combined organic layers were washed

with brine (20 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure, azeotroped with toluene (20 mL) and dried under high vacuum. The residue was dissolved in THF (130 mL), MeI (2.01 g, 32.65 mmol) was added, and the solution was cooled to 0 ºC. Sodium hydride (0.78 g, 32.65 mmol) was added slowly in portions. The reaction mixture was warmed to rt and stirred for 16 h. The reaction

◦ mixture was quenched by adding MeOH (30 mL) followed by H 2O (50 mL) at 0 C. The

reaction mixture was diluted with Et 2O (150 mL), and the aqueous layer was extracted

with Et 2O (2 x 50 mL). The combined organics were washed with brine (50 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with EtOAc/hexanes (0.4:1) to

23 afford 2.9 g (70 %) of 2.78 as colorless oil. [α] D +9.4° ( c 1.8, CH 2Cl 2); IR (film) 2880,

1475, 1422, 1361, 1055, 733, 696 cm 1; 1H NMR (400 MHz) δ 7.277.17 (m, 5H), 4.45

112

(d, J = 11.6 Hz, 1H), 4.41 (d, J = 12.0 Hz, 1H), 3.533.47 (m, 4H), 3.33 (s, 3H), 3.08 (dd,

J = 10.0, 2.2 Hz, 1H), 1.901.87 (m, 1H), 1.551.34 (m, 5H), 1.14 (s, 3H), 0.82 (s, 9H),

0.80 (s, 9H), 0.02 (s, 6H), 0.04 (s, 6H); 13 C NMR (100 MHz) δ 138.6, 128.3 (2), 127.5

(2), 127.4, 84.9, 78.4, 72.8, 67.8, 63.7, 60.7, 35.1, 30.8, 27.0, 26.1 (3C), 26.0 (3C), 24.0,

18.4, 18.3, 1.8, 1.9, 5.3 (2); HRMS (FAB) calc’d for C 28 H54 O4Si 2 M+Na = 533.3458,

found 533.3442.

MeO TBSO Alcohol 2.79: To a solution of ether 2.78 (2.9 g, 5.67 mmol)

6 HO 5 in EtOH (56 mL) was added 10% Pd/C (0.6 g, 0.56 mmol) TBSO Me 2.79

under an atmosphere of H 2. The reaction mixture was

followed 48 h (TLC control). The reaction mixture was filtered through a Celite plug,

which had been previously washed with EtOAc. The solvent was concentrated under

reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (0.8:1) to afford 1.9 g (80%) of 2.79 as a colorless oil. [α] D +6.0° ( c 6.8,

CH 2Cl 2); IR (film) 3306, 2953, 2928, 2885, 1471, 1462, 1253, 1098, 1055, 831, 811, 770 cm 1; 1H NMR (400 MHz) δ 3.783.72 (m, 2H), 3.573.52 (m, 2H), 3.48 (s, 3H), 3.20

(dd, J = 10.0, 2.8 Hz, 1H), 2.40 (bs, 1H), 1.821.76 (m, 1H), 1.651.39 (m, 5H), 1.21 (s,

3H), 0.87 (m, 9H), 0.84 (s, 9H), 0.95 (m, 6H), 0.02 (s, 6H); 13 C NMR (100 MHz) δ 86.6,

78.6, 63.6, 61.0, 60.8, 35.4, 33.0, 26.9, 26.0 (3C), 25.9 (3C), 23.9, 18.3, 18.2, 1.8, 1.9,

5.4 (2C); HRMS (FAB) calc’d for C 21 H48 O4Si 2+Na = 443.2989, found 443.2973.

O O OH OMe TBSO Aldol 2.82 : To a solution of oxalyl chloride (0.61 g, O N 3 5 ◦ Me TBSO Me 4.86 mmol) in CH 2Cl 2 (30 mL) at 78 C was added Bn 2.82

113

DMSO (0.79 g, 10.12 mmol) dropwise. After stirring for 10 min, alcohol 2.79 (1.70 g,

4.05 mmol) in CH 2Cl 2 (10 mL) was added via cannula, and the reaction mixture was

stirred at 78 ◦C for 45 min. Triethylamine (1.02 g, 10.12 mmol) was added dropwise by cannula, and the reaction mixture was slowly warmed to rt. After 2 h, the reaction was quenched with dropwise addition of H 2O (10 mL). The organic layer was separated and washed with brine (10 mL), dried (Na 2SO 4) and concentrated under reduced pressure.

The crude product was dissolved in Et 2O (50 mL), filtered through a plug of silica gel

using ether, concentrated and dried under high vacuum. This material was used directly

without further purification. To a solution of ( R)4benzyl3propionyl2oxazolidinone

(2.81 ) (0.94 g, 4.05 mmol) in CH 2Cl 2 (20 mL) was added dibutylborontriflate (5.30 mL of a 1.0 M solution in CH 2Cl 2, 5.26 mmol) and triethylamine (0.61 g, 6.07 mmol)

dropwise at 0 °C. The solution was cooled to 78 ◦C and to this was added the aldehyde

◦ (1.70 g, 4.05 mmol) in CH 2Cl 2 (10 mL) at 78 C. The resulting solution was stirred for

20 min at 78 °C. After warming the solution to 0 ◦C, the reaction mixture was stirred an additional hour. The reaction was terminated by adding a pH 7 aq. phosphate buffer solution (0.2 M aq. sodium hydrogen phosphate/0.1 M aq. citric acid, 82:18, 8.0 mL) and

MeOH (24.2 mL). To this cloudy solution was added a solution of MeOH and 30% H 2O2

(2:1, 24.2 mL), and the resulting solution was stirred for 1 h at 0 ◦C. The solution was concentrated and extracted with EtOAc (3 x 60 mL). The organic layer was washed with sat’d aq. NaHCO 3 (50 mL), brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and the residue purified by flash chromatography

23 eluting with EtOAc/hexanes (2:1) to afford 1.50 g (78%) of 2.82 as colorless oil. [α] D

39.2° ( c 3.75, CH 2Cl 2); IR (film) 3500, 2953, 2885, 2856, 1781, 1696, 1382, 1359, 1252,

114

1208, 1195, 1097, 1051, 1004, 832, 771, 700 cm 1; 1H NMR (400 MHz) δ 7.307.14 (m,

5H), 4.654.60 (m, 1H), 4.174.10 (m, 2H), 4.074.04 (m, 1H), 3.823.79 (m, 2H), 3.63

(d, J = 1.2 Hz, 1H), 3.52 (t, J = 5.8 Hz, 2H), 3.46 (s, 3H), 3.253.20 (m, 2H), 2.71 (dd, J

= 13.4, 9.4 Hz, 1H), 1.741.34 (m, 6H), 1.22 (d, J = 7.2 Hz, 3H), 1.19 (s, 3H), 0.83 (s,

9H), 0.80 (s, 9H), 0.05 (s, 6H), 0.01 (s, 6H); 13 C NMR (100 MHz) δ 175.8, 153.1, 135.2,

129.4 (2C), 128.9 (2C), 127.3, 88.7, 78.7, 71.8, 66.0, 63.6, 60.7, 55.3, 43.0, 37.7, 36.3,

35.1, 34.2, 26.9, 26.0 (3C), 25.9 (3C), 24.1, 18.3, 11.4, 1.8, 1.8, 5.3; HRMS (FAB) calc’d for C 34 H61 NO 7Si 2 +Na = 674.3884, found 674.3868.

Acid 2.83: To a stirred solution of aldol 2.82 (1.41 g, O OTBS OMe TBSO

HO 3 5 2.16 mmol) in CH 2Cl 2 (15 mL) at 0 °C was added 2,6 Me TBSO Me 2.83 lutidine (0.41 g, 3.89 mmol) and TBSOTf (0.85 g, 3.24

mmol). The reaction mixture was stirred for 15 min at 0 °C and quenched with sat’d aq.

NaHCO 3 (10 mL). The organic layer was separated, washed with brine (10 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

crude product dissolved in THF/H 2O (4:1, 31 mL). To this was added 30% aq. H 2O2

(1.14 mL, 10.07 mmol) and 0.8 M aq. LiOH (4.6 mL, 3.65 mmol) at 0 °C. The reaction was warmed to rt and stirred for 16 h. The reaction was quenched by adding aq. Na 2SO 3

(1.33 M, 10 mL) and aq. NH 4Cl solution (10 mL). The reaction mixture was then diluted with EtOAc (40 mL). The organic layer was separated and the aqueous layer was back extracted with EtOAc (2 × 20 mL). The combined organic layers were washed with brine

(20 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and the residue purified by flash chromatography eluting with EtOAc/hexanes

23 (0.4/1) to yield 1.11 g (85%) of 2.83 as a colorless oil. [α] D +5.4° ( c 2.5, CH 2Cl 2); IR

115

(film) 3538, 2953, 2928, 2886, 2856, 1709, 1471, 1462, 1252, 1097, 1053, 1003, 832,

803 cm 1; 1H NMR (400 MHz) δ 4.354.32 (m, 1H), 3.603.52 (m, 2H), 3.50 (s, 3H), 2.98

(d, J = 9.6 Hz, 1H), 2.692.64 (m, 1H), 1.821.76 (m, 1H), 1.671.40 (m, 5H), 1.21 (s,

3H), 1.14 (d, J = 7.2 Hz, 3H), 0.88 (s, 9H), 0.87 (s, 18H), 0.10 (s, 3H), 0.09 (s, 3H), 0.07

(s, 3H), 0.03 (s, 9H); 13 C NMR (100 MHz) δ 180.1, 84.7, 78.8, 70.7, 63.5, 60.5, 43.4,

35.8, 35.8, 27.1, 26.1 (3C), 25.9 (3C), 25.8 (3C), 24.1, 18.3, 17.9, 9.5, 1.7, 1.8, 2.0,

4.2, 5.1, 5.3 (2C); HRMS (FAB) calc’d for C 30 H66 O6Si 3+Na = 629.4065, found

629.4047.

Ester 2.84 : To a solution of acid 2.83 (0.22 Et O OTBS OMe TBSO I O 3 5 g, 0.36 mmol) in THF (4 mL) at rt was added HO Me Me TBSO Me 2.84 Et 3N (0.04 g, 0.38 mmol) and 2,4,6

trichlorobenzoyl chloride (0.01 g, 0.40 mmol). The reaction mixture was stirred for 3 h at

rt, and the solids were filtered and washed with hexanes (10 mL). The combined filtrates

were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene

(5 mL). To this solution was added iododiol 2.63 (0.11 g, 0.43 mmol) in toluene (2 mL)

and DMAP (0.06 g, 0.49 mmol). After being stirred for 16 h at rt, the reaction mixture

was diluted with EtOAc (20 mL), washed with sat’d aq. NaHCO 3 (10 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and the residue purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to afford

23 0.24 g (78 %) of 2.84 as a colorless oil. [α] D +11.2° ( c 1.2, CH 2Cl 2); IR (film) 3445,

2951, 2936, 2909, 2877, 2857, 1729, 1461, 1251, 1192, 1095, 1004, 950, 836, 775 cm 1;

1H NMR (400 MHz) δ 6.68 (d, J = 14.6 Hz, 1H), 6.43 (d, J = 14.6, 1H), 4.81 (dd, J =

10.4, 2.8 Hz, 1H), 4.144.10 (m, 1H), 3.583.50 (m, 2H), 3.50 (s, 3H), 3.25 (dd, J = 9.6,

116

3.2 Hz, 1H), 3.18 (bs, 1H), 2.742.61 (m,1H), 1.681.35 (m, 8H), 1.25 (s, 3H), 1.21 (d, J

= 4.8 Hz, 3H), 1.17 (s, 3H), 0.90 (s, 9H), 0.890.86 (m, 21H), 0.11 (s, 6H), 0.07 (s, 3H),

0.06 (s, 3H), 0.02 (s, 6H); 13 C NMR (100 MHz) δ 175.8, 148.0, 83.9, 80.2, 79.3, 77.7,

71.2, 63.4, 60.7, 44.3, 36.5, 35.2, 26.7, 26.2 (3C), 26.1, 25.9 (6C), 24.8, 23.5, 23.2, 18.4,

18.3, 18.0, 14.4, 10.7, 1.6, 1.7, 3.8, 4.5, 5.4 (2C); HRMS (FAB) calc’d for

C37 H77 IO 7Si 3+Na = 867.3920, found 867.3934.

Alcohol 2.85 : To a solution of ester 2.84 Et O OTBS OMe HO I (0.27 g, 0.32 mmol) in MeOH (7 mL) was O 3 5 HO Me Me TBSO Me 2.85 added CSA (0.015 g, 0.065 mmol) at 0 ◦C.

After stirring for 1 h, the reaction was quenched with NaHCO 3 (0.040 g). The mixture

was concentrated under reduced pressure, and the residue was purified by flash

chromatography eluting with EtOAc/hexanes (1/5) to afford 0.20 g (85%) of 2.85 as a

23 colorless oil. [α] D +14.5° ( c 0.9, CH 2Cl 2); IR (film) 3458, 2952, 2936, 2908, 2877,

1724, 1461, 1251, 1194, 1094, 1045, 1005, 836, 775, 735 cm 1; 1H NMR (400 MHz) δ

6.67 (d, J = 11.6 Hz, 1H), 6.42 (d, J = 11.6, 1H), 4.80 (dd, J = 8.4, 2.0 Hz, 1H), 4.80 (dt,

J = 5.6, 2.0 Hz, 1H), 3.59 (t, J = 4.4 Hz, 2H), 3.47 (s, 3H), 3.323.27 (m, 2H), 2.742.70

(m, 1H), 1.751.40 (m, 8H), 1.24 (s, 3H), 1.21 (d, J = 4.8 Hz, 3H), 1.21 (s, 3H), 0.90 (s,

9H), 0.880.85 (m, 12H), 0.11 (s, 3H), 0.10 (s, 3H), 0.08 (s,3H), 0.06 (s, 3H); 13 C NMR

(100 MHz) δ 175.8, 147.8, 84.3, 80.2, 78.9, 77.7, 77.04, 77.3, 63.3, 60.4, 44.6, 35.8, 34.9,

29.6, 26.2 (3C), 25.9 (3C), 24.5, 24.1, 23.2, 18.4, 18.0, 15.0, 10.6, 1.6, 1.7, 3.9, 4.5;

HRMS (FAB) calc’d for C 31 H63 IO 7Si 2+Na = 753.3055, found 753.3053.

117

Aldehyde 2.86 : DessMartin periodinane

Et O OTBS OMe O (0.53 g, 0.31 mmol) and NaHCO 3 (0.13 g, I O 3 5 HO Me TBSO Me 1.57 mmol) were suspended in CH Cl (3 Me 2.86 2 2

mL). Alcohol 32 (0.23 g, 0.31 mmol) in CH 2Cl 2 (3 mL) was added dropwise via cannula into the reaction mixture. After 1 h at rt, the reaction mixture was added to a mixture of sat’d aq. NaHCO 3 (5 mL), sat’d aq. Na 2SO 3 (5 mL) and H 2O (10 mL). The mixture was

extracted with Et 2O (2 x 20 mL). The combined organic layers were washed with brine

(10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (0.4/1) to afford 0.18 g (80%) of 2.86 as a foam. [α] D +14.9° ( c 0.75,

CH 2Cl 2); IR (film) 2962, 2886, 2853, 1736, 1695, 1461, 1401, 1250, 1190, 1094, 1050 cm 1; 1H NMR (400 MHz) δ 9.8 (s, 1H), 6.67 (d, J = 14.4 Hz, 1H), 6.43 (d, J = 14.4 Hz,

1H), 4.81 (dd, J = 10.4, 2.8 Hz, 1H), 4.11 (dt, J = 6.8, 3.2 Hz, 1H), 3.47 (s, 3H), 3.21 (d,

J = 9.6 Hz, 2.4, 1H), 3.11 (bs, 1H), 1.851.50 (m, 8H), 1.25 (s, 3H), 1.21 (d, J = 7.2 Hz,

3H), 1.21 (s, 3H), 0.90 (s, 9H), 0.890.85 (m, 12H), 0.12 (s, 3H), 0.11 (s, 3H), 0.08 (s,

3H), 0.04 (s, 3H); 13 C NMR (100 MHz) δ 202.1, 175.7, 148.0, 84.1, 80.2, 78.4, 77.7,

71.1, 60.7, 44.5, 38.7, 35.2, 31.4, 26.1 (3C), 25.9 (3C), 24.6, 23.5, 23.1, 18.4, 18.0, 14.6,

10.7, 1.6, 1.8, 3.9, 4.6; HRMS (FAB) calc’d for C 31 H61 IO 7Si 2+Na = 751.2898, found

751.2892.

118

Alcohol 2.87 : To a solution of aldehyde 2.86 (0.20 g, 0.27 OH

mmol) in DMSO (125 mL) at rt was added CrCl 2 (0.33g,

Me HO OTBS 2.75 mmol) and NiCl 2 (0.004 mg, 0.027 mmol). The 6 Me 5 Et O OMe reaction was stirred for 16 h and quenched by the addition 3 O OTBS of H 2O (60 mL). The mixture was diluted with EtOAc (500 Me 2.87 mL), and the layers were separated. The organic layer was washed with H 2O (3 x 50 mL). The combined aqueous layers were backextracted with

EtOAc (3 x 200 mL). The combined organic layers were washed with brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/2) to afford 0.06 g (dr = 1:1 at C9) (50%) of 2.87 as a foam. IR (film) 3465, 2953, 2909,

1731, 1461, 1251, 1095, 1252, 1118, 1093, 1067 cm 1; 1H NMR (400 MHz) δ 6.85 (d, J =

16.4 Hz, 1H), 6.19 (d, J = 16.4 Hz, 1H), 4.83 (dd, J = 10.8, 1.2 Hz, 1H), 4.33 (t, J = 8.4

Hz, 1H), 3.76 (dd, J = 9.6, 3.2 Hz, 1H), 3.23 (dt, J = 12.8, 3.5 Hz, 1H), 3.12 (s, 3H), 2.83

(bs, 1H), 2.462.38 (m, 1H), 1.991.90 (m, 2H), 1.811.52 (m, 5H), 1.33 (s, 3H), 1.19 (d,

J = 8.0 Hz, 3H), 1.18 (s, 3H), 0.94 (t, J = 8.2 Hz, 9H), 0.89 (s, 9H), 0.86 (t, J = 7.2 Hz,

3H), 0.60 (q, J = 7.8 Hz, 6H), 0.13 (s, 3H), 0.04 (s, 3H); 13 C NMR (100 MHz) δ 204.1,

175.7, 151.8, 127.7, 80.1, 78.9, 74.1, 73.2, 71.2, 49.0, 48.3, 44.7, 34.6, 31.1, 26.2, 21.9,

21.0, 19.7, 18.4, 16.1, 10.3, 6.7, 5.1, 3.0, 4.8; HRMS (FAB) calc’d for C 31 H62 O7Si 2+Na

= 625.3932, found 625.3925.

119

Ester 2.89 : To a solution of acid 2.83 (0.55 g, 0.89 mmol) in TBSO Me HO OTBS THF (9 mL) at rt were added Et 3N (0.01 g, 0.94 mmol) and 6 Me 5 2,4,6trichlorobenzoyl chloride (0.24 g, 0.98 mmol). The Et O OMe 3 O OTBS reaction mixture was stirred for 3 h at rt, and the solids were Me 2.89 filtered and washed with hexanes (10 mL). The combined filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene (20 mL). To this solution were added diol 2.64 (0.14 g, 1.07 mmol) in toluene (5

mL) and DMAP (0.14 g, 1.21 mmol). After being stirred for 16 h at rt, the reaction

mixture was diluted with EtOAc (50 mL), washed with saturated aq. NaHCO 3 (20 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to afford 2.7 g (78

23 %) of 2.89 as a colorless oil. [α] D +24.8° ( c 1.7, CH 2Cl 2); IR (film) 3494, 2953, 2882,

1731, 1471, 1382, 1254 cm 1; 1H NMR (400 MHz) δ 5.88 (dd, J = 17.6, 10.8 Hz, 1H),

5.30 (dd, J = 17.0, 1.4 Hz, 1H), 5.12 (dd, J = 10.6, 1.4 Hz, 1H), 4.83 (dd, J = 10.2, 3.0

Hz, 1H), 4.534.49 (m, 1H), 3.593.57 (m, 3H), 3.11 (s, 3H), 2.63 (dd, J = 7.0, 2.2 Hz,

1H), 2.06 (bs, 1H), 1.721.35 (m, 8H), 1.25 (s, 3H), 1.18 (d, J = 7.2 Hz, 3H), 1.03 (s,

3H), 0.960.92 (m, 9H), 0.88 (s, 9H), 0.87.83 (m, 3H), 084 (s, 9H), 0.640.58 (m, 6H),

13 0.05 (s, 6H), 0.04 (s, 6H); C NMR (100 MHz, CDCl 3) δ 174.8, 140.9, 113.9, 80.5, 79.0,

74.9, 73.7, 69.5, 63.3, 48.4, 42.5, 37.4, 30.0, 26.1, 25.9, 25.6, 25.1, 22.4, 18.3, 18.0, 17.4,

+ 10.7, 9.4, 7.1, 5.4, 3.9, 4.6, 5.4. HRMS (FAB) calc’d for C 37 H78 O7Si 3+H = 719.5133,

found 719.5119.

120

Alcohol 2.90: To a solution of ester 2.89 (0.37 g, 0.52 HO Me mmol) in MeOH (11 mL) was added CSA (0.024 g, 0.10 HO OTBS 6 Me 5 mmol) at 0 ◦C. After stirring for 1hr, the solution was added Et O OMe 3 O OTBS solid NaHCO 3 (0.040 g).The solution was concentrated under

Me 2.90 reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (2/1) to afford 0.26 g of 2.90 in 85% yield

23 as a colorless oil. [α] D +15.4° ( c 1.2, CH 2Cl 2) IR (film) 3458, 2950, 2877, 1733, 1462,

1378, 1251, 1114, 1047 cm 1; 1H NMR (400 MHz) δ 5.88 (dd, J = 17.4, 11.0 Hz, 1H),

5.30 (dd, J = 17.2, 0.8 Hz, 1H), 5.13 (dd, J = 10.8, 1.2 Hz, 1H), 4.82 (dd, J = 10.4, 2.8

Hz, 1H), 4.48 (td, J = 10.0, 2.8 Hz, 1H), 3.66 (m, 1H), 3.61 (t, J = 6.2 Hz, 2H), 3.14 (s,

3H), 2.65 (qd, J = 7.2, 2.0 Hz, 1H), 2.18 (bs, 1H), 1.771.42 (m, 8H), 1.25 (s, 3H), 1.19

(d, J = 7.2 Hz, 3H), 1.06 (s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.85 (s, 9H), 0.870.83 (m,

3H), 0.660.56 (m, 6H), 0.08 (s, 3H), 0.08 (s, 3H); 13 C NMR (100 MHz) δ 174.9, 140.8,

114.0, 80.6, 79.3, 74.9, 73.5, 69.6, 63.2, 48.6, 43.1, 37.6, 30.3, 26.2, 25.9, 25.0, 22.5,

+ 18.1, 17.5, 10.7, 10.0, 7.1, 5.4, 3.9, 4.7. HRMS (FAB) calc’d for C 31 H64 O7Si 2+H =

605.4269, found 605.4260.

O Vinyl ketone 2.91: DessMartin periodinane (0.26 g, 0.61

mmol) and NaHCO 3 (0.21 g, 2.56 mmol) were suspended in Me HO OTBS 6 Me CH 2Cl 2 (3 mL). Alcohol 2.90 (0.31 g, 0.51 mmol) in CH 2Cl 2 5 Et O OMe 3 (5 mL) was added dropwise via cannula into the reaction O OTBS Me mixture. After 1h at rt, the reaction mixture was added to a 2.91

121

mixture of sat’d aq. NaHCO 3 (5 mL), sat’d aq. Na 2SO 3 (5 mL) and H 2O (10 mL). The

mixture was extracted with Et 2O (2 x 20 mL). The combined organic layers were washed

with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the crude aldehyde was dissolved in THF (20 mL) and cooled to 0

◦C under Argon. Vinylmagnesium bromide (3.65 mL, 0.7 M in THF, 2.56 mmol) was added dropwise, and the reaction mixture was stirred for 30 min at 0 ◦C. The reaction was

quenched with sat’d aq. NH 4Cl (10 mL). The reaction mixture was diluted with EtOAc

(25 mL), and the aqueous layer was extracted with EtOAc (2 x 10 mL). The combined

organic layers were washed with brine (10mL), dried (Na 2SO 4) and filtered. The solvent was passed through a short plug of silica gel, concentrated under reduced pressure, and dissolved in CH 2Cl 2 (50 mL). DessMartin periodinane (0.43 g, 1.02 mmol) was added at

rt, and the reaction mixture was stirred for 2 h. The reaction was quenched with sat’d aq.

NaHCO 3 (30 mL). The organic layer was separated, washed with brine (25 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and purified by flash chromatography eluting with EtOAc/hexanes (0.8/1) to afford 0.13 g (57%) of

23 2.91 as a colorless oil. [α] D +16.4° ( c 1, CH 2Cl 2) IR (film) 2952, 2879, 2877, 1733,

1684, 1463, 1411, 1379, 1250, 1190, 1094, 1050 cm 1; 1H NMR (400 MHz) δ 6.36 (dd, J

= 17.6, 10.4 Hz, 1H), 6.22 (dd, J = 17.6, 1.2 Hz, 1H), 5.88 (dd, J = 17.4, 10.4 Hz, 1H),

5.82 (dd, J = 10.4, 1.2 Hz, 1H), 5.30 (dd, J = 17.4, 1.4 Hz, 1H), 5.12 (dd, J = 10.8, 1.2

Hz, 1H), 4.82 (dd, J = 10.0, 2.8 Hz, 1H), 4.494.45 (m, 1H), 3.59 (dd, J = 10.0, 2.0 Hz,

1H), 3.11 (s, 3H), 2.672.64 (m, 2H), 2.542.46 (m, 1H), 2.11 (bs, 1H), 1.981.90 (m,

1H), 1.771.49 (m, 6H), 1.25 (s, 3H), 1.17 (d, J = 7.2 Hz, 3H), 1.07 (s, 3H), 0.95 (t, J =

8.0 Hz, 9H), 0.85 (s, 9H), 0.880.83 (m, 3H), 0.670.58 (m, 5H), 0.07 (s, 3H), 0.05 (s,

122

3H); 13 C NMR (100 MHz) δ 200.5, 174.8, 140.9, 136.5, 128.0, 114.0, 80.6, 78.8, 74.9,

73.6, 69.7, 48.8, 43.1, 37.7, 33.2, 27.2, 25.9, 25.0, 22.5, 18.1, 17.8, 10.7, 10.1, 7.1, 5.4,

+ 3.9, 4.6. HRMS (FAB) calc’d for C 33 H64 O7Si 2 Na = 651.4080, found 651.4081.

O Macrolactoketone 2.88: DessMartin periodinane (0.07 g,

0.15 mmol) was added to alcohol 2.87 (0.03 g, 0.05 mmol) in Me HO OTBS 6 Me CH 2Cl 2 (5 mL) and pyridine (0.15 mL). After 1 h at rt, the 5 Et O OMe 3 reaction mixture was added to a mixture of sat’d aq. NaHCO 3 O OTBS Me 2.88 (5 mL), sat’d aq. Na 2SO 3 (5 mL) and H 2O (10 mL). The

mixture was extracted with Et 2O (2 x 20 mL). The combined organic layers were washed

with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and the residue was purified by flash chromatography eluting with

EtOAc/hexanes (1.2/1) to afford 0.024 g (82%) of 2.88 as a white solid (mp = 192195

23 °C); [α] D +6.7° ( c 2.7, CH 2Cl 2); IR (film) 3443, 2956, 2930, 2893, 2883, 2857, 1733,

1658, 1461, 1262, 1126, 1095, 1066, 1053, 1001, 835cm 1; 1H NMR (400 MHz) δ 7.08

(d, J = 16.4 Hz, 1H), 6.14 (d, J = 16.4 Hz, 1H), 4.77 (dd, J = 10.0, 2.8 Hz, 1H), 4.05 (dd,

J = 10.0, 6.8 Hz, 1H), 3.46 (s, 3H), 3.403.31 (m, 2H), 3.022.95 (m, 1H), 2.52 (bs, 1H),

2.091.52 (m, 10H), 1.34 (s, 3H), 1.30 (s, 3H), 1.25 (d, J = 6.8 Hz, 3H), 0.950.89 (m,

12H), 0.80 (s, 3H), 0.07 (s, 3H), 0.07 (m, 6H), 0.05 (s, 3H); 13 C NMR (100 MHz) δ

203.7, 176.2, 152.5, 127.5, 86.6, 77.3, 76.6, 73.7, 71.7, 59.8, 45.4, 44.7, 34.8, 33.7, 32.7,

26.0 (6C), 25.5, 22.4, 21.5, 18.1, 17.4, 10.6, 1.7, 1.8, 3.9, 4.6; HRMS (FAB) calc’d for

C31 H60 O7Si 2+Na = 623.3775 found 623.3736.

123

TES Ether 2.91 : To a solution of diol 2.73 (1.0 g, 2.61 mmol) TESO TBSO ◦ 6 in DMF (26 mL) at 0 C was added imidazole (0.25 g, 3.65 BnO 5 HO Me 2.91 mmol) and TESCl (0.47 g, 3.13 mmol). The reaction mixture was warmed to rt. After 1.5 h, the reaction was quenched by with H 2O (40 mL). The aqueous layer was extracted with ether (4 x 50 mL). The combined organic layers were washed with H 2O (50 mL) brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/5) to afford 1.16 g (90%) of 2.91 as a

23 colorless oil. [α] D +7.7° ( c 8.3, CH 2Cl 2); IR (film) 3443, 2956, 2930, 2893, 2883, 2857,

1733, 1658, 1461, 1262, 1126, 1095, 1066, 1053, 1001, 835 cm 1; 1H NMR (400 MHz) δ

7.297.18 (m, 5H), 4.43 (s, 2H), 3.61 (dd, J = 7.2, 3.6 Hz, 1H), 3.54 (t, J = 6.4 Hz, 2H),

3.503.47 (m, 1H), 2.47(s, 1H), 1.881.80 (m, 1H), 1.651.36 (m, 5H), 1.02(s, 3H), 0.88

(t, J = 6.4 Hz, 9H), 0.82 (s, 9H), 0.55 (q, J = 7.6 Hz, 6H), 0.02 (s, 6H); 13 C NMR (100

MHz) δ 138.3, 128.3 (2), 127.6 (2), 127.5, 76.0, 74.1, 72.9, 67.3, 63.8, 34.9, 33.1, 26.8,

25.9 (3C), 21.8, 18.2, 6.9 (3C), 5.2 (3C), 5.3 (2C); HRMS (FAB) calc’d for

C27 H52 O4Si 2+Na = 519.3302 found 519.3286.

MeO TBSO Ether 2.92: To a solution of 2.91 (0.50 g, 1.00 mmol) in THF 6 BnO 5 (10 mL) was added MeI (2.01 g, 32.65 mmol), and the TESO Me 2.92 reaction mixture was cooled to 0 °C. Sodium hydride (0.78 g, 32.65 mmol) was then added in small portions. The reaction mixture was allowed to warm to rt and stirred for

16 h. The reaction mixture was quenched by adding MeOH (3 mL) followed by H 2O (5 mL) at 0 °C. The reaction mixture was diluted with Et 2O (15 mL), and the aqueous layer

124

was backextracted with Et 2O (2 x 5 mL). The combined organic layers were washed with brine (5 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under

reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (0.4:1) to afford 0.4 g (78 %) of 2.92 as a colorless oil. [α] D +8.4° ( c

1 1 3.8, CH 2Cl 2); IR (film) 2880, 1475, 1422, 1361, 1055, 733, 696 cm ; H NMR (400

MHz) δ 7.357.26 (m, 5H), 4.54 (d, J = 12.0 Hz, 1H), 4.49 (d, J = 12.0 Hz, 1H), 3.61

3.55 (m, 4H), 3.42 (s, 3H), 3.17 (dd, J = 10.4, 2.4 Hz, 1H), 1.931.89 (m, 1H), 1.651.39

(m, 5H), 1.20 (s, 3H), 0.95 (t, J = 8 Hz, 9H), 0.89 (s, 9H), 0.59 (q, J = 8 Hz, 6H), 0.04 (s,

6H); 13 C NMR (100 MHz) δ 138.6, 128.3 (2C), 127.6 (2C), 127.4, 84.6, 78.2, 72.8, 67.8,

63.7, 60.8, 35.4, 30.8, 27.0, 26.0 (3C), 24.2, 18.3, 7.2 (3C), 6.9 (3C), 5.3 (2C); HRMS

(FAB) calc’d for C 28 H54 O4Si 2 M+Na = 533.3458, found 533.3455.

◦ TESO TBSO Ether 2.93 : To a solution of 2.91 in CH 2Cl 2 (90 mL) at 0 C 6 BnO 5 was added Proton Sponge (11.74 g, 54.87 mmol) and MeO Me 2.93

Me 3OBF 4 (8.11 g, 54.87 mmol). The reaction mixture was warmed to rt and stirred for 16 h. The reaction mixture was concentrated and quenched with sat’d aq. NH 4Cl (50 mL). The reaction mixture was diluted with Et 2O (100 mL), and the aqueous layer was backextracted with Et 2O (2 x 50 mL). The combined organic layers were washed with 1N aq. HCl solution (60 mL), sat’d aq. NaHCO 3 (80 mL), H 2O

(80 mL), brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under

reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (1/25) to afford 7.4 g (80 %) of 2.93 as an oil. [α] D +11.5° (c

1 1 2.6,CH 2Cl 2); IR (film) 1255, 1361, 1471, 2857, 2953, 3398, 1096, 899, 733, 696 cm ; H

125

NMR (400 MHz) δ 7.277.20 (m, 5H), 4.45 (d, J = 12.0 Hz, 1H), 4.41 (d, J = 12.0 Hz,

1H), 3.74 (dd, J = 9.8, 2.2 Hz, 2H), 3.543.48 (m, 4H), 3.07 (s, 3H), 1.841.76 (m, 1H),

1.601.28 (m, 4H), 0.98 (s, 3H), 0.880.84 (m, 9H), 0.83 (s, 9H), 0.550.49 (m, 6H), 0.02

(s, 6H); 13 C NMR (100 MHz) δ 138.6, 128.3 (2C), 127.6 (2C), 127.4, 78.8, 73.7, 72.9,

67.9, 63.5, 48.7, 32.7, 29.9, 26.0, 25.9 (3C), 18.2, 18.0, 7.1 (3C), 5.3 (3C), 5.3 (2C);

HRMS (FAB) calc’d for C 28 H54 O4Si 2 M+Na = 533.3458, found 533.3445.

OTES TBSO Alcohol 2.95 : To a solution of ether 2.93 (5.6 g, 10.96 mmol) in

6 HO 5 EtOH (100 mL) was added 10% Pd/C (1.16 g, 1.09 mmol) MeO Me 2.95 under an atmosphere of H 2. The reaction mixture was followed

48 h (TLC control). The reaction mixture was filtered through a Celite plug, which had been previously washed with EtOAc. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (1/13) to afford 3.9 g (85%) of 2.95 as a colorless oil. [α] D +6.6° (c 2.5,

1 1 CH 2Cl 2); IR (film) 3404, 2950, 2886, 2858, 1471, 1387, 1406, 733, 696 cm ; H NMR

(400 MHz) δ 3.833.61 (m, 3H), 3.57 (t, J = 6.2 Hz, 2H), 3.16 (s, 3H), 1.811.30 (m, 6H),

1.07 (s, 3H), 0.960.92 (m, 9H), 0.88 (s, 9H), 0.650.59 (m, 6H), 0.03 (s, 6H); 13 C NMR

(100 MHz) δ 78.9, 76.3, 63.4, 60.5, 49.0, 35.2, 29.8, 26.2, 25.9 (3C), 18.4, 18.3, 7.0 (3C),

+ 5.2 (3C), 5.4 (2C); HRMS (FAB) calc’d for C 21 H48 O4Si 2+H = 421.3169, found

421.3161.

126

Aldol 2.97 : To a solution of oxalyl chloride (1.80 g, O O OH OTES TBSO

O N 3 5 14.25 mmol) in CH 2Cl 2 (80 mL) at 78 ºC was added Me MeO Me Bn 2.97 DMSO (1.85 g, 23.76 mmol) dropwise. After stirring

for 10 min, alcohol 2.93 (4.00 g, 9.50 mmol) in CH 2Cl 2 (15 mL) was added via cannula,

and the reaction mixture was stirred at 78 ◦C for 45 min. Triethylamine (2.39 g, 23.76

mmol) was then added dropwise by cannula, and the reaction mixture was slowly

warmed to rt. After 2 h, the reaction was quenched with H 2O (50 mL). The organic layer

was separated and washed with brine (50 mL), dried (Na 2SO 4) and concentrated under

reduced pressure. The crude product was dissolved in Et 2O (100 mL), filtered through a plug of silica gel using ether, concentrated and dried under high vacuum. This material was used directly without further purification. To a solution of ( R)4benzyl3propionyl

2oxazolidinone ( 2.81 ) (2.21 g, 9.50 mmol) in CH 2Cl 2 (30 mL) was added dibutylborontriflate (12.35 mL of a 1.0 M solution in CH 2Cl 2, 12.35 mmol) and triethylamine (1.44 g, 14.25 mmol) dropwise at 0 °C. The solution was cooled to 78 ºC and to this was added the aldehyde (4.00 g, 9.50 mmol) dissolved in CH 2Cl 2 (9 mL) at

78 ºC. The resulting solution was stirred for 20 min at 78 ºC. The solution was then

warmed to 0 ºC and stirred an additional hour. The reaction was terminated by adding a pH 7 aq. phosphate buffer solution (0.2 M aq. sodium hydrogen phosphate/0.1 M aq. citric acid, 82:18, 18.9 mL) and MeOH (56.8 mL). To this cloudy solution was added a solution of methanol and 30% H 2O2 (2:1, 56.8 mL) and the resulting solution was stirred for 1 h at 0 ºC. The solution was concentrated and extracted with EtOAc (3 x 100 mL).

The combined organic layers were washed with sat’d aq. NaHCO 3 (100 mL), brine (100

mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure,

127

and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1:5)

23 to afford 4.83 g (78%) of 2.97 as a colorless oil. [α] D 32.0° (c 3.2, CH 2Cl 2); IR (film)

3538, 2953, 2877, 2857, 1748, 1702, 1461, 1384, 1406, 1238, 1101 cm 1; 1H NMR (400

MHz) δ 7.337.20 (m, 5H), 4.664.60 (m, 1H), 4.184.06 (m, 3H), 3.893.79 (m, 2H),

3.78 (d, J = 1.2 Hz, 1H), 3.603.55 (m, 2H), 3.29 (dd, J = 9.4, 3.0 Hz, 1H), 3.15 (s, 3H),

2.76 (dd, J = 13.2, 10.0 Hz, 1H), 1.701.30 (m, 6H), 1.26 (d, J = 7.2 Hz, 3H), 1.06 (s,

3H), 0.950.92 (m, 9H) 0.89 (s,9H), 0.660.60 (m, 6H), 0.04 (s, 6H); 13 C NMR (100

MHz) δ 175.9, 153.1, 135.3, 129.4 (2C), 128.9 (2C), 127.3, 79.0, 76.8, 70.9, 66.1, 63.3,

55.5, 48.6, 42.8, 37.8, 36.3, 29.8, 25.9 (4C), 18.3, 17.6, 11.2, 7.0 (3C), 5.1 (3C), 5.4

+ (2C); HRMS (FAB) calc’d for C 34 H61 NO 7Si 2 +H = 652.4065, found 652.4056.

Acid 2.98 : To a stirred solution of aldol 2.97 (4.5 g, O OTBS OTES

6.90 mmol) in CH 2Cl 2 (35 mL) at 0 ºC was added HO 3 5 OTBS MeO Me 2.98 Me 2,6lutidine (1.33 g, 12.42 mmol) and TBSOTf (2.73 g, 10.35 mmol). The reaction mixture was stirred for 15 min at 0 ºC and quenched with sat’d aq. NaHCO 3 (20 mL). The organic layer was separated, washed with brine (20 mL),

dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the crude product dissolved in THF/H 2O (4:1, 95 mL). To this was added 30% aq. H 2O2

(3.65 mL, 32.08 mmol) and 0.8 M aq. LiOH (13.8 mL, 11.08 mmol) at 0 ºC. The reaction was warmed to rt and stirred for 16 h. The reaction was quenched by adding aq. 1.33 M

Na 2SO 3 (22 mL) and aq. NH 4Cl solution (20 mL). The reaction mixture was then diluted with EtOAc (150 mL). The organic layer was separated and the aqueous layer was back extracted with EtOAc (2 × 50 mL). The combined organic layers were washed with brine

128

solution (20 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (1/25) to yield 3.56 g (85%) of acid 2.98 . [α] D +6.0° (c 0.55, CH 2Cl 2);

IR (film) 2953, 2857, 1708, 1463, 1386, 1256, 1098 cm 1; 1H NMR (400 MHz) δ 4.41

(m, 1H), 3.64 (bd, J = 9.2 Hz, 1H), 3.57 (t, J = 6.0 Hz, 2H), 3.13 (s, 3H), 2.65 (m, 1H),

1.751.33 (m, 6H), 1.13 (d, J = 7.2 Hz, 3H), 1.04 (s, 3H), 0.980.95 (m, 9H), 0.89 (s, 9H),

0.87 (s, 9H), 0.670.59 (m, 6H), 0.05 (2s, 6H), 0.04 (s, 6H); 13 C NMR (100 MHz) δ

178.7, 79.1, 77.9, 73.7, 70.5, 63.3, 48.4, 42.9, 37.2, 29.9, 26.1, 25.9 (3C), 25.8 (3C), 18.3,

17.9, 17.5, 7.1 (3C), 5.4 (3C), 4.2, 5.1, 5.4 (2C); HRMS (FAB) calc’d for

+ C30 H66 O6Si 3+H = 607.4245, found 607.4242.

Ester 2.99 : To a solution of acid 2.98 (0.60 g, 0.98 mmol) in OTBS

I THF (10 mL) at rt were added Et 3N (0.1 g, 1.03 mmol) and Me HO OMe 6 2,4,6trichlorobenzoyl chloride (0.26 g, 1.08 mmol). The Me 5 Et O OTES reaction mixture was stirred for 3 h at rt, and the solids were 3 O OTBS filtered and washed with hexanes (20 mL). The combined Me 2.99 filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene (15 mL). To this solution was added iododiol

2.63 (0.26 g, 0.98 mmol) in toluene (5 mL) and DMAP (0.16 g, 1.33 mmol). After

stirring for 16 h at rt, the reaction mixture was diluted with EtOAc (50 mL), washed with

sat’d aq. NaHCO 3 (20 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated

under reduced pressure, and the residue was purified by flash chromatography eluting

23 with EtOAc/hexanes (0.4/1) to afford 0.68 g (75%) of 2.99 as a colorless oil. [α] D

129

+27.4° ( c 0.7, CH 2Cl 2); IR (film) 3460, 2951, 2933, 2878, 1732, 1471, 1462, 1381, 1254,

1199, 1095, 1073, 1044, 1005, 949, 834, 774, 736 cm1; 1H NMR (400 MHz) δ 6.54 (d, J

= 14.4 Hz, 1H), 6.41 (d, J = 14.4, 1H), 4.78 (dd, J = 9.6, 3.2 Hz, 1H), 4.48 (dt, J = 9.6,

3.2 Hz, 1H), 3.603.55 (m, 3H), 3.10 (s, 3H), 2.672.62 (m, 1H), 2.33 (bs, 1H), 1.791.34

(m, 8H), 1.23 (s, 3H), 1.17 (d, J = 6.8 Hz, 3H), 1.02 (s, 3H), 0.94 (t, J = 8 Hz, 9H), 0.88

0.86 (m, 12H), 0.84 (s, 9H), 0.660.55 (m, 6H), 0.06 (s, 3H), 0.03 (s, 6H); 13 C NMR (100

MHz) δ 175.0, 147.6, 80.0, 79.0, 77.6, 77.2, 73.6, 69.6, 63.2, 48.3, 42.7, 37.3, 29.4, 26.0,

25.9 (6C), 25.2, 22.6, 18.2, 18.0, 17.4, 10.6, 9.6, 7.2 (3C), 5.4 (3C), 3.8, 4.6, 5.4 (2C);

HRMS (FAB) calc’d for C 37 H77 IO 7Si 3+Na = 867.3920 found 867.3900.

Alcohol 2.100 : To a solution of TBAF•3H 2O (0.90 g, 2.86 OH I mmol) in DMF (28 mL) was added AcOH (0.70 g, 2.01 Me HO OMe 6 mmol). After stirring for 30 min, the solution was added to Me 5 Et O OTES 2.99 (0.68 g, 0.95 mmol), and the reaction mixture was stirred 3 O OTBS for 20 h at rt. The reaction was quenched with H 2O (20 mL), Me 2.100

and the aqueous layer was backextracted with Et 2O (4 x 60 mL). The combined organic layers were washed with sat’d aq. NaHCO 3 (50 mL), H 2O

(50 mL), brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under

reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (1/5) to afford 0.35 g (78% borsm) of 2.100 as a colorless oil. [α] D

+30.8° ( c 0.6, CH 2Cl 2); IR (film) 3458, 2951, 2936, 2909, 2877, 1729, 1461, 1251, 1192,

1095, 1069, 1044, 1004, 950, 940, 836, 775 cm 1; 1H NMR (400 MHz) δ 6.55 (d, J =

14.4 Hz, 1H), 6.41 (d, J = 14.4, 1H), 4.77 (dd, J = 10.0, 3.2 Hz, 1H), 4.45 (dt, J = 9.6,

130

3.2 Hz, 1H), 3.66 (dd, J = 10.4, 2.0 Hz, 1H), 3.623.58 (m, 2H), 3.14 (s, 3H), 2.67 (dq, J

= 4.8, 2.4 Hz, 1H), 2.55 (bs, 1H), 2.03 (m, 1H), 1.821.42 (m, 8H), 1.23 (s, 3H), 1.18 (d,

J = 7.2 Hz, 3H), 1.05 (s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.860.84 (m, 12H), 0.660.55 (m,

6H), 0.77 (s, 3H), 0.05 (s, 3H); 13 C NMR (100 MHz) δ 175.0, 147.6, 80.1, 79.3, 77.5,

77.3, 73.5, 69.8, 63.2, 48.6, 43.4, 37.7, 30.2, 26.2, 25.9 (3C), 24.9, 22.7, 18.1, 17.4, 10.6,

10.3, 7.1 (3C), 5.4 (3C), 3.9, 4.7; HRMS (FAB) calc’d for C 31 H63 IO 7Si 2+Na = 753.3055 found 753.3032.

Aldehyde 2.101 : DessMartin periodinane (0.23 g, 0.54

I CHO mmol) and NaHCO 3 (0.19 g, 2.25 mmol) were suspended in Me HO OMe 6 Me CH 2Cl 2 (3 mL). Alcohol 2.100 (0.33 g, 0.45 mmol) in 5 Et O OTES 3 CH 2Cl 2 (4 mL) was added dropwise via cannula into the O OTBS Me reaction mixture. After 1 h at rt, the reaction mixture was 2.101 added to a mixture of sat’d aq. NaHCO 3 (5 mL), sat’d aq. Na 2SO 3 (5 mL) and H 2O (10

mL). The mixture was extracted with Et 2O (2 x 20 mL). The combined organic layers were washed with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/5) to afford 0.28 g (85% yield) of 2.101

23 as a colorless oil. [α] D +32.8° ( c 0.7, CH 2Cl 2); IR (film) 2952, 2879, 2877, 1733, 1684,

1463, 1411, 1379, 1250, 1190, 1094, 1050 cm 1; 1H NMR (400 MHz) δ 9.76 (m, 1H),

6.55 (d, J = 14.4 Hz, 1H), 6.41 (d, J = 14.4 Hz, 1H), 4.78 (dd, J = 10.0, 3.2 Hz, 1H),

4.44 (dt, J = 8.8, 3.6 Hz, 1H), 3.59 (dd, J = 9.6, 2.4 Hz, 1H), 3.10 (s, 3H), 2.67 (dq, J =

4.8, 2.4 Hz, 1H), 2.532.35 (m, 3H), 1.991.91 (m, 1H), 1.771.47 (m, 6H), 1.24 (s, 3H),

1.17 (d, J = 7.2 Hz, 3H), 1.08 (s, 3H), 0.95 (t, J = 8.4 Hz, 9H), 0.870.85 (m, 12H), 0.66

131

0.55 (m, 6H), 0.07 (s, 3H), 0.05 (s, 3H); 13 C NMR (100 MHz) δ 202.1, 174.8, 147.6,

80.1, 78.6, 77.5, 77.2, 73.4, 69.8, 48.8, 43.3, 38.0, 37.6, 25.8 (3C), 25.6, 24.9, 22.7, 18.1,

17.7, 10.6, 10.2, 7.1 (3C), 5.4 (3C), 3.9, 4.6; HRMS (FAB) calc’d for C 31 H61 IO 7Si 2+Na

= 751.2898 found 751.2892.

Alcohol 2.102 : To a solution of aldehyde 2.101 (0.28 g, 0.27 OH

mmol) in DMSO (158 mL) at rt was added CrCl 2 (0.47g, Me HO OMe 6 3.84 mmol) and NiCl 2 (0.005 mg, 0.038 mmol). The Me 5 Et O OTES reaction mixture was stirred for 16 h then quenched by the 3 O OTBS addition of H 2O (90 mL). The mixture was diluted with Me 2.102 EtOAc (600 mL), and the layers were separated. The organic layer was washed with H 2O (3 x 100 mL). The combined aqueous layers were back extracted with EtOAc (3 x 200 mL). The combined organic layers were washed with brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with

EtOAc/hexanes (2/5) to afford 0.12 g (dr = 1:1 at C9) (52%) of 2.102 as a foam. IR (film)

3443, 2953, 2936, 2909, 2878, 1731, 1461, 1251, 1095, 1057, 1005, 972, 854, 831, 815,

774 cm 1; 1H NMR (400 MHz) δ 5.755.60 (m, 2H), 4.81 (td, J = 10.6, 2 Hz, 1H), 4.30

4.12 (m, 1H), 4.073.98 (m, 1H), 3.14 (s, 3H), 2.692.46 (m, 2H), 1.921.73 (m, 2H),

1.53133 (m, 4H), 1.291.26 (m, 3H), 1.211.16 (m, 3H), 1.12 1.03 (m, 3H), 0.970.89

(m, 12H), 0.870.84 (s, 9H), 0.640.53 (m, 6H), 0.10 0.01 (m, 6H); 13 C NMR (100 MHz)

δ 175.7, 175.3, 136.2, 133.7, 133.2, 132.4, 80.3, 79.6, 79.4, 79.3, 74.4, 73.9, 73.7, 73.4,

72.9, 72.6, 70.5, 70.3, 48.7, 48.3, 42.5, 40.4, 30.6, 30.5, 29.6, 27.5, 26.1, 25.8, 23.3, 22.1,

132

20.6, 19.1, 18.3, 18.0, 17.4, 15.5, 15.0, 10.6, 10.6, 7.1, 7.0, 5.3, 5.1, 3.4, 4.1, 4.8, 5.0;

HRMS (FAB) calc’d for C 31 H62 O7Si 2+Na = 625.3932, found 625.3911.

Ester 2.104 : To a solution of acid 2.92 (2.9 g, 4.77 mmol) in

TBSO THF (49 mL) at rt were added Et 3N (0.50 g, 5.00 mmol) and Me HO OMe 6 Me 5 2,4,6trichlorobenzoyl chloride (1.27 g, 5.24 mmol). The Et O OTES 3 reaction mixture was stirred for 3 h at rt, and the solids were O OTBS Me 2.104 filtered and washed with hexanes (25 mL). The combined

filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in

toluene (90 mL). To this solution were added diol 2.64 (0.74 g, 5.73 mmol) in toluene (8

mL) and DMAP (0.79 g, 6.44 mmol). After being stirred for 16 h at rt, the reaction

mixture was diluted with EtOAc (100 mL), washed with sat’d aq. NaHCO 3 (50 mL),

dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and purified by flash chromatography eluting with EtOAc/hexanes (1/25) to afford 2.7 g (78

23 %) of 2.104 as a colorless oil. [α] D +24.8° (c 1.7, CH 2Cl 2); IR (film) 3494, 2953, 2882,

1731, 1471, 1382, 1254 cm 1; 1H NMR (400 MHz) δ 5.88 (dd, J = 17.6, 10.8 Hz, 1H),

5.30 (dd, J = 17.0, 1.4 Hz, 1H), 5.12 (dd, J = 10.6, 1.4 Hz, 1H), 4.83 (dd, J = 10.2, 3.0

Hz, 1H), 4.534.49 (m, 1H), 3.593.57 (m, 3H), 3.11 (s, 3H), 2.64 (qd, J = 8.8, 2.0 Hz,

1H), 2.06 (bs, 1H), 1.721.35 (m, 8H), 1.25 (s, 3H), 1.18 (d, J = 7.2 Hz, 3H), 1.03 (s, 3H),

0.960.92 (m, 9H), 0.88 (s, 9H), 0.87.83 (m, 3H), 084 (s, 9H), 0.640.58 (m, 6H), 0.05

(2s, 6H), 0.04 (s, 6H); 13 C NMR (100 MHz) δ 174.8, 140.9, 113.9, 80.5, 79.0, 74.9, 73.7,

69.5, 63.3, 48.4, 42.5, 37.4, 30.0, 26.1, 25.9 (6C), 25.1, 22.4, 18.3, 18.0, 17.4, 10.7, 9.4,

133

+ 7.1 (3C), 5.4 (3C), 3.9, 4.6, 5.4 (2C); HRMS (FAB) calc’d for C 37 H78 O7Si 3+H =

719.5133, found 719.5119.

Alcohol 2.105 : To a solution of TBAF•3H 2O (3.55 g, 11.26 HO Me HO OMe mmol) in DMF (110 mL) was added AcOH (0.70 g, 6 Me 5 Et O OTES 11.81mmol). After stirring for 30 min, the solution was added 3 O OTBS to 2.104 (2.70 g, 3.75 mmol), and the reaction mixture was Me 2.105

stirred for 20 h at rt. The reaction was quenched with H 2O

(120 mL), and the aqueous layer was backextracted with Et 2O (4 x 100 mL). The combined organic layers were washed with sat’d aq. NaHCO 3 (100 mL), H 2O (100 mL), brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with

EtOAc/hexanes (1/5) to afford 1.38 g (60% yield, 86% borsm) of 2.105 as a colorless oil.

23 [α] D +15.4° (c 1.2, CH 2Cl 2); IR (film) 3458, 2950, 2877, 1733, 1462, 1378, 1251, 1114,

1047 cm1; 1H NMR (400 MHz) δ 5.88 (dd, J = 17.4, 11.0 Hz, 1H), 5.30 (dd, J = 17.2,

0.8 Hz, 1H), 5.13 (dd, J = 10.8, 1.2 Hz, 1H), 4.82 (dd, J = 10.4, 2.8 Hz, 1H), 4.48 (td, J =

10.0, 2.8 Hz, 1H), 3.66 (m, 1H), 3.61 (t, J = 6.2 Hz, 2H), 3.14 (s, 3H), 2.65 (qd, J = 7.2,

2.0 Hz, 1H), 2.18 (bs, 1H), 1.771.42 (m, 8H), 1.25 (s, 3H), 1.19 (d, J = 7.2 Hz, 3H), 1.06

(s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.85 (s, 9H), 0.870.83 (m, 3H), 0.660.56 (m, 6H), 0.08

(s, 3H), 0.08 (s, 3H); 13 C NMR (100 MHz) δ 174.9, 140.8, 114.0, 80.6, 79.3, 74.9, 73.5,

69.6, 63.2, 48.6, 43.1, 37.6, 30.3 (3C), 26.2, 25.9, 25.0, 22.5, 18.1, 17.5, 10.7, 10.0, 7.1

+ (3C), 5.4 (3C), 3.9, 4.7; HRMS (FAB) calc’d for C31 H64 O7Si 2+H = 605.4269, found

605.4260.

134

Vinyl Ketone 2.106 : DessMartin periodinane (1.16 g, 2.73 O

mmol) and NaHCO 3 (0.95 g, 11.4 mmol) were suspended in Me HO OMe CH Cl (6 mL). Alcohol 2.105 (1.38 g, 2.28 mmol) in 6 2 2 Me 5 Et O OTES CH 2Cl 2 (20 mL) was added dropwise via cannula into the 3 O OTBS reaction mixture. After 1 h at rt, the reaction mixture was Me 2.106

added to a mixture of sat’d aq. NaHCO 3 (50 mL), sat’d aq.

Na 2SO 3 (50 mL) and H 2O (100 mL). The mixture was extracted with Et 2O (2 x 100 mL).

The combined organic layers were washed with brine (100 mL), dried (Na 2SO 4) and

filtered. The solvent was concentrated under reduced pressure, dried under vacuum, and

the crude aldehyde was dissolved in THF (90 mL) and cooled to 0 ºC under Argon.

Vinylmagnesium bromide (16.3 mL, 0.7 M in THF, 11.4 mmol) was added dropwise, and

the reaction mixture was stirred for 30 min at 0 ºC. The reaction was quenched with sat’d

aq. NH 4Cl (50 mL). The reaction mixture was diluted with EtOAc (150 mL), and the

aqueous layer was extracted with EtOAc (2 x 50 mL). The combined organic layers were

washed with brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was passed through a short plug of silica gel, concentrated under reduced pressure, and dissolved in

CH 2Cl 2 (220 mL). DessMartin periodinane (1.93 g, 4.56 mmol) was added at rt, and the

reaction mixture was stirred for 2 h. The reaction was quenched with sat’d aq. NaHCO 3

(100 mL). The organic layer was separated, washed with brine (50 mL), dried (Na 2SO 4)

and filtered. The solvent was concentrated under reduced pressure and purified by flash

chromatography eluting with EtOAc/hexanes (1/13) to afford 0.80 g (57%) of 2.106 as a

23 colorless oil. [α] D +16.4° (c 1, CH 2Cl 2); IR (film) 2952, 2879, 2877, 1733, 1684, 1463,

1411, 1379, 1250, 1190, 1094, 1050 cm 1; 1H NMR (400 MHz) δ 6.36 (dd, J = 17.6, 10.4

135

Hz, 1H), 6.22 (dd, J = 17.6, 1.2 Hz, 1H), 5.88 (dd, J = 17.4, 10.4 Hz, 1H), 5.82 (dd, J =

10.4, 1.2 Hz, 1H), 5.30 (dd, J = 17.4, 1.4 Hz, 1H), 5.12 (dd, J = 10.8, 1.2 Hz, 1H), 4.82

(dd, J = 10.0, 2.8 Hz, 1H), 4.494.45 (m, 1H), 3.59 (dd, J = 10.0, 2.0 Hz, 1H), 3.11 (s,

3H), 2.672.64 (m, 2H), 2.542.46 (m, 1H), 2.11 (bs, 1H), 1.981.90 (m, 1H), 1.771.49

(m, 6H), 1.25 (s, 3H), 1.17 (d, J = 7.2 Hz, 3H), 1.07 (s, 3H), 0.95 (t, J = 8.0 Hz, 9H), 0.85

(s, 9H), 0.880.83 (m, 3H), 0.670.58 (m, 5H), 0.07 (s, 3H), 0.05 (s, 3H); 13 C NMR (100

MHz) δ 200.5, 174.8, 140.9, 136.5, 128.0, 114.0, 80.6, 78.8, 74.9, 73.6, 69.7, 48.8, 43.1,

37.7, 33.2, 27.2, 25.9 (3C), 25.0, 22.5, 18.1, 17.8, 10.7, 10.1, 7.1 (3C), 5.4 (3C), 3.9,

4.6; HRMS (FAB) calc’d for C 33 H64 O7Si 2 +Na = 651.4080, found 651.4081.

O Ketolactone 2.103 : To a solution of 2.106 (0.79 g, 1.25

mmol) in CH 2Cl 2 (125 mL) at rt was added the Grubbs II Me HO OMe 6 Me catalyst (0.21 g, 0.25 mmol). The reaction mixture was 5 Et O OTES 3 stirred for 20 h at rt. The solvent was concentrated under O OTBS Me reduced pressure and the residue was purified by flash 2.103 chromatography eluting with EtOAc/hexanes (1/5) to afford

23 0.45 g (60%, 90% borsm) of 2.103 as a foam. [α] D 17.3° (c 0.9, CH 2Cl 2); IR (film)

3443, 2956, 2878, 1731, 1659, 1462, 1411, 1370, 1252, 1118, 1093, 1067 cm 1; 1H NMR

(400 MHz) δ 6.85 (d, J = 16.4 Hz, 1H), 6.19 (d, J = 16.4 Hz, 1H), 4.83 (dd, J = 10.8, 1.2

Hz, 1H), 4.33 (t, J = 8.4 Hz, 1H), 3.76 (dd, J = 9.6, 3.2 Hz, 1H), 3.23 (dt, J = 12.8, 3.5

Hz, 1H), 3.12 (s, 3H), 2.83 (bs, 1H), 2.462.38 (m, 1H), 1.991.90 (m, 2H), 1.811.52 (m,

5H), 1.33 (s, 3H), 1.19 (d, J = 8.0 Hz, 3H), 1.18 (s, 3H), 0.94 (t, J = 8.2 Hz, 9H), 0.89 (s,

9H), 0.86 (t, J = 7.2 Hz, 3H), 0.60 (q, J = 7.8 Hz, 6H), 0.13 (s, 3H), 0.04 (s, 3H); 13 C

136

NMR (100 MHz) δ 204.1, 175.7, 151.8, 127.7, 80.1, 78.9, 74.1, 73.2, 71.2, 49.0, 48.3,

44.7, 34.6, 31.1, 26.2 (3C), 21.9, 21.0, 19.7, 18.4, 16.1, 10.3, 6.7 (3C), 5.1 (3C), 3.0,

+ 4.8; HRMS (FAB) calc’d for C 31 H60 O7Si 2+H = 601.3956, found 601.3949.

OH Ketal 2.110 : To a solution of 2.103 (0.030 g, 0.05 mmol)

in MeOH (7 mL) was added pTsOH (2 mg, 0.01 mmol) at Me HO OMe O Me 6 0 ºC. After 3 h at this temperature, the reaction was

Et O 5 3 quenched by adding sat’d aq. NaHCO 3 (5 mL). The O OTBS reaction mixture was diluted with EtOAc (20 mL) and the Me 2.110 aqueous layer was backextracted with EtOAc (2 x 5 mL). The combined organic layers were washed with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and purified directly by flash chromatography

23 eluting with hexanes/EtOAc (4:1) to afford 12 mg (52%) of 2.110 as a foam. [α] D

+10.7° ( c 0.8, CH 2Cl 2); IR (film) 3441, 2954, 2934, 2882, 1729, 1461, 1374, 1264, 1178,

1145, 1072, 1006, 961, 834, 775, 702 cm 1; 1H NMR (400 MHz) δ 6.07 (d, J = 16.4 Hz,

1H), 5.95 (d, J = 16.4 Hz, 1H), 4.85 (t, J = 3.6 Hz, 1H), 4.54 (dd, J = 11.2, 2.4 Hz, 1H),

4.29 (d, J = 9.6 Hz, 1H), 3.943.90 (m, 1H), 3.21 (s, 3H), 2.902.82 (m, 1H), 2.061.95

(m, 3H), 1.851.71 (m, 2H), 1.571.46 (m, 2H), 2.59 (bs, 2H), 1.30 (s, 3H), 1.27 (d, J =

6.8 Hz, 3H), 1.27 (s, 3H), 0.88 (t, J = 7.2 Hz, 3H), 0.90 (s, 9H), 0.08 (s, 3H), 0.05 (s, 3H);

13 C NMR (100 MHz) δ 175.4, 146.1, 136.3, 122.8, 102.9, 83.2, 74.7, 73.6, 71.7, 70.9,

49.1, 44.4, 31.3, 29.3, 25.9 (3C), 21.6, 21.2, 18.0, 16.4, 10.5, 4.1, 4.7; HRMS (FAB) calc’d for C 25 H46 O7Si+K = 525.2650, found 525.2667.

137

Triol 2.111 : To a solution of 2.103 (34 mg, 0.05 mmol) in O

9 THF (2.2 mL) was added TBAF•3H 2O (54 mg, 0.17mmol) Me HO OMe at 0 ºC and allowed to slowly warm to 10 ºC and stirred for 6 Me 12 5 Et O OH h. The reaction mixture was quenched by slowly adding

O OH sat’d aq. NaHCO 3 (3 mL). The mixture was diluted with Me 2.111 EtOAc (5 mL), and the aqueous layer was extracted with

EtOAc (2 x 5 mL). The combined organic layers were washed with brine (10 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with EtOAc/hexanes (3:2) to afford

23 13 mg of 2.111 (70%) as a foam. [α] D +3.5° ( c 0.9, CH 2Cl 2); IR (film) 3441, 2956,

2878, 1727, 1462, 1372, 1265, 1178, 1093 cm 1; 1H NMR (400 MHz) δ 6.74 (d, J = 16.0

Hz, 1H), 6.19 (d, J = 16.0 Hz, 1H), 4.87 (dd, J = 10.8, 2.4 Hz, 1H), 4.00 (t, J = 8.8 Hz,

1H), 3.86 (dd, J = 10.8, 2.4 Hz, 1H), 3.72 (bs, 1H), 3.20 (s, 3H), 2.88 (bs, 1H), 2.652.53

(m, 3H), 2.312.23 (m, 1H), 12.951.84 (m, 2H), 1.741.46 (m, 5H), 1.33 (s, 3H), 1.30 (d,

J = 6.8 Hz, 3H), 1.01 (s, 3H), 0.91 (t, J = 7.2 Hz, 3H); 13 C NMR (100 MHz) δ 202.2,

175.9, 150.4, 128.3, 79.9, 78.7, 73.8, 73.2, 48.9, 46.8, 37.1, 33.5, 30.6, 22.0, 21.8, 20.8,

16.2, 14.1, 10.4; HRMS (FAB) calc’d for C 19 H32 O7+Na = 395.2046 found 395.2024.

138

Alcohol 2.112 : To a solution of 2.103 (0.075 g, 0.12 mmol) OH in MeOH (3 mL) at rt was added CeCl 3•7H 2O (53 mg, 0.14 9 Me HO OMe mmol). The reaction mixture was cooled to 60 ºC after which 12 Me 5 Et O OH NaBH 4 (5.3 mg, 0.14 mmol) was added. After 30 min at this

O OTBS temperature, the reaction was quenched by adding sat’d aq. Me 2.112 NH 4Cl (2 mL). Ethyl acetate (10 mL) was added, and the

aqueous layer was backextracted with EtOAc (2 x 5 mL). The combined organic layers

were washed with 1N HCl solution (5 mL), sat’d aq. NaHCO 3 (5 mL), H 2O (5 mL), brine

(5 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was dried under vacuum. The residue was dissolved in MeOH

(17 mL) and cooled to 0 ºC after which pTsOH (4.5 mg, 0.024 mmol) was added. The reaction mixture was stirred at 0 ºC for 3 h after which the reaction was quenched by adding NaHCO 3 (10 mg). The mixture was concentrated and purified directly by flash

chromatography eluting with EtOAc/hexanes (2/5) to afford 44 mg of 2.112 (75%) as a foam. (dr = 7:1 dr at C9 by 1H NMR). Major 9(R) isomer: IR (film) 3441, 2956, 2878,

1727, 1462, 1372, 1265, 1178, 1093 cm 1; 1H NMR (400 MHz) δ 5.905.84 (m, 1H), 5.71

(m, 1H), 4.874.84 (m, 1H), 4.134.04 (m, 2H), 3.753.73 (m, 1H), 3.20 (s, 3H), 2.80

2.70 (m, 2H), 2.52 (bs, 1H), 2.13 (bs, 1H), 2.021.96 (m, 1H), 1.831.42 (m, 5H), 1.30 (s,

3H), 1.22 (m, 1H), 1.26 (s, 3H), 1.22 (d, J = 6.4 Hz, 3H), 1.07 (s, 3H), 0.93 (t, J = 7.2 Hz,

3H), 0.87 (s, 9H), 0.10 (s, 6H); 13 C NMR (100 MHz) δ 175.4, 133.7, 133.2, 81.5, 78.6,

73.9, 72.6, 72.1, 71.7, 49.4, 48.0, 37.2, 31.0, 29.6, 27.6, 25.8 (3C), 24.5, 23.5, 17.5, 15.1,

10.8, 4.6, 4.7; HRMS (FAB) calc’d for C 25 H48 O7Si+Na = 511.3067, found 511.3042.

139

Me2N Macrolide 2.114 : To a solution of 55 (70 mg, 0.14 Me OTES

MeO2CO O 9 mmol) in DMF (1.5 mL) and CH 2Cl 2 (1.5 mL) at rt Me O OMe were added imidazole (12 mg, 0.16 mmol) and Me 12 5 Et O OH DMAP (2 mg). The reaction mixture was cooled to 3 O OTBS 78 ºC, and TESCl (25 mg, 0.15 mmol) was added. Me 2.114 After stirring for 3 h at 78 ºC the reaction was

quenched by adding sat’d aq. NH 4Cl (3 mL). The mixture was diluted with EtOAc (10

mL), and the aqueous layer was backextracted with EtOAc (2 x 5 mL). The combined

organic layers were washed with H 2O (5 mL), dried (Na 2SO 4) and filtered. The solvent

was concentrated under reduced pressure, azeotroped with toluene (5 mL), and the crude

alcohol was taken to the next step. To a suspension of freshly activated 4 Å molecular

sieves (1.55 g) and AgOTf (0.72 g, 2.82 mmol) in CH2Cl 2/toluene (5 mL, 1:1) was added

dropwise by cannula a mixture of C5 alcohol (0.14 mmol), desosamine donor 7 (0.28 g,

0.85 mmol) and 2,6ditert butyl4methylpyridine (0.18 g, 0.85 mmol) in CH 2Cl 2 (2.5

mL) at 0 ºC. The reaction flask was wrapped with aluminum foil, warmed to rt and stirred

for an additional 20 h. The reaction was quenched with Et 3N (4.0 mL), filtered through

Celite, and eluted with EtOAc (50 mL). The filtrate was washed with sat’d aq. NaHCO 3

(20 mL), dried (Na 2SO 4), filtered, and concentrated under reduced pressure. The residue

was purified by flash chromatography eluting with hexanes/EtOAc (3:2) to afford 50% of

57 as a foam (dr = 7:1 dr at C9 by 1H NMR). Major 9(R) isomer: IR (film) 3441, 2956,

2878, 1727, 1462, 1372, 1265, 1178, 1093 cm 1; 1H NMR (400 MHz) δ 5.80 (m, 1H),

5.48 (d, J = 16.4 Hz, 1H), 5.15 (dd, J = 10.0, 1.6 Hz, 1H), 4.55 (dd, J = 10.4, 7.6 Hz, 1H),

4.48 (d, J = 7.6 Hz, 1H), 3.963.93 (m, 2H), 3.77 (s, 3H), 3.723.68 (m, 1H), 3.473.43

140

(m, 1H), 3.18 (s, 3H), 2.752.56 (m, 2H), 2.27 (m, 9H), 2.332.30 (m, 1H), 1.26 (s, 3H),

1.21 (d, J = 6.8 Hz, 3H), 1.22 (d, J = 6.0 Hz, 3H), 1.04 (s, 3H), 0.95 (t, J = 8.0 Hz, 9H),

0.88 (s, 9H), 0.85 (t, J = 11.4 Hz, 3H), 0.620.52 (m, 6H), 0.12 (s, 3H), 0.10 (s, 3H); 13 C

NMR (100 MHz) δ 174.3, 153.3, 135.8, 131.2, 96.6, 79.7, 78.7, 77.8, 75.1, 73.9, 73.6,

73.0, 68.8, 63.0, 54.6, 49.1, 48.6, 40.6 (2C), 37.7, 31.7, 30.8, 29.6, 28.1, 25.8 (3C), 22.9,

21.2, 20.6, 18.0, 15.6, 10.6, 6.9 (3C), 5.0 (3C), 4.2, 4.4; HRMS (FAB) calc’d for

C41 H79 NO 11 Si 2+Na = 840.5089, found 840.5081.

Macrolide 2.115 : To a solution of 2.114 (28 mg, Me2N Me OH 0.034 mmol) in THF (0.5 mL) at 0 ºC was added MeO2CO O 9 Me TBAF (0.15 mL, 0.145 mmol, 1 M in THF). After O OMe Me 12 5 3 h at rt, the reaction was quenched with sat’d aq. Et O OH 3 O OH NaHCO 3 (1 mL). EtOAc (5 mL) was added. The Me 2.115 aqueous layer was extracted with EtOAc (2 × 3

mL). The combined organic layers were washed with brine (5 mL), dried (Na 2SO 4),

filtered and concentrated under reduced pressure. The residue was purified by flash

chromatography eluting with MeOH/CH 2Cl 2 (1/16) to obtain diol 2.115 as a foam (dr =

7:1 at C9 by 1H NMR). Major 9(R) isomer: IR (film) 3413, 2949, 2835, 1745, 1721,

1461,776 cm 1; 1H NMR (400 MHz) δ 5.825.81 (m, 2H), 5.21 (dd, J = 10.64 2.4 Hz,

1H), 4.56 (dd, J = 10.6, 7.8 Hz, 1H), 4.42 (d, J = 7.6 Hz, 1H), 3.913.78 (m, 3H), 3.78 (s,

3H), 3.473.45 (m, 1H), 3.17 (s, 3H), 2.73 (dt, J = 12.0, 4.2 Hz, 1H), 2.402.36 (m, 1H),

2.26 (s, 6H), 2.152.05 (m, 1H), 1.91.3 (m, 12H), 1.24 (s, 3H), 1.23 (d, J = 6.0 Hz, 3H),

1.21 (s, 3H), 1.20 (d, J = 9.6 Hz, 3H), 0.890.85 (m, 3H); 13 C NMR (100 MHz) δ 174.1,

141

154.3, 113.5, 110.7, 94.5, 85.5, 79.8, 77.8, 77.8, 77.1, 72.1, 70.3, 68.7, 63.2, 53.0, 48.3,

40.4 (2C), 36.4, 30.5, 29.7, 24.5, 12.1, 17.4, 15.2, 10.4; HRMS (FAB) calc’d for

C29 H51 NO 11 +Na = 612.3360, found 612.3358.

OH Alcohol 2.117 : To a solution of 2.103 (620 mg, 1.03 mmol)

9 in MeOH (22 mL) at rt was added CeCl 3•7H 2O (430 mg, Me TESO OMe 12 Me 1.15 mmol). The reaction mixture was cooled to 60 ºC after 5 Et O OH which NaBH 4 (45 mg, 1.17 mmol) was added. After 30 min, O OTBS Me 2.117 at this temperature, the reaction was quenched by adding

sat’d aq. NH 4Cl (20 mL). Ethyl acetate (50 mL) was added, and the aqueous layer was extracted with EtOAc (2 x 20 mL). The combined organic layers were washed with 1N

HCl solution (20 mL), sat’d aq. NaHCO 3 (20 mL), H 2O (20 mL), brine (20 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was dried under vacuum. The residue was dissolved in CH 2Cl 2 (21 mL) and

cooled to 78 ºC after which 2,6lutidine (440 mg, 4.11 mmol) and TESOTf (815 mg,

3.08 mmol) were added. The reaction mixture was stirred for 1 h at 78 ºC. The reaction

was quenched by adding sat’d aq. NaHCO 3 (20 mL). The mixture was extracted with

CH 2Cl 2 (10 mL). The organic layer was separated, washed with brine (20 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was dried under vacuum. The residue was dissolved in MeOH (140 mL) and

cooled to 0 ºC after which pTsOH (39 mg, 0.20 mmol) was added. The reaction mixture

was stirred at 0 ºC for 3 h, and the reaction was quenched by adding NaHCO 3 (50 mg).

The mixture was concentrated and purified directly by flash chromatography eluting with

142

EtOAc/hexanes (1/5) to afford 323 mg (52%) of a 2.117 as a foam (7:1 dr at C9 by 1H

NMR). Major 9(R) isomer: IR (film) 3441, 2956, 2878, 1727, 1462, 1372, 1265, 1178,

1093 cm 1; 1H NMR (400 MHz) δ 5.745.64 (m, 2H), 4.84 (dd, J = 10.4, 2.4 Hz, 1H),

4.064.01 (m, 2H), 3.77 (dd, J = 10.4, 2.8 Hz, 1H), 3.18 (s, 3H), 2.772.67 (m, 1H), 2.46

2.38 (m, 1H), 2.59 (bs, 2H), 2.001.34 (m, 7H), 1.31 (s, 3H), 1.18 (d, J = 7.2 Hz, 3H),

1.09 (s, 3H), 0.90 (t, J = 8.0 Hz, 9H), 0.86 (s, 9H), 0.880.84 (m, 3H), 0.55 (q, J = 7.7 Hz,

6H), 0.09 (s, 3H), 0.08 (s, 3H); 13 C NMR (100 MHz) δ 174.4, 134.5, 133.4, 80.7, 78.3,

75.3, 73.3, 72.7, 71.8, 49.4, 48.2, 35.7, 30.2, 27.8, 25.7, 23.0, 22.0, 18.2, 17.9, 15.4, 10.9,

+ 7.0 (3C), 6.7 (3C), 4.7, 4.8; HRMS (FAB) calc’d for C 31 H62 O7Si 2–H = 601.3956, found

601.3997.

Macrolide 2.118 : To a solution of 2.117 (330 OTES

mg, 0.54 mmol) in DMF (5.5 mL) and CH 2Cl 2 8 Me TESO OMe (5.5 mL) at rt were added imidazole (43 mg, 0.62 Me NMe2 McO Et O 4 O O Me mmol) and DMAP (3 mg, 0.03 mmol). The

O OTBS reaction mixture was cooled to 78 ºC, and Me 2.118 TESCl (90 mg, 0.60 mmol) was added. After

stirring for 3 h at 78 ºC, the reaction was quenched by adding sat’d aq. NH 4Cl (5 mL).

The mixture was diluted with EtOAc (10 mL) and the aqueous layer was extracted with

EtOAc (2 x 5 mL). The combined organic layers were washed with H 2O (10 mL), brine

(10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and azeotroped with toluene (5 mL), and the crude C5 alcohol was taken to the next step. To a suspension of freshly activated 4 Å molecular sieves (6.24 g) and AgOTf

(2.73 g, 10.63 mmol) in CH 2Cl 2 (10.4 mL) and toluene (10.4 mL) was added dropwise by

143

cannula to a solution of C5 alcohol (0.54 mmol), desosamine thiopyrimidine donor 1.48

(1.06 g, 3.23 mmol) and 2,6ditertbutyl4methylpyridine (664 mg, 3.23 mmol) in

CH 2Cl 2 (10.4 mL) at 0 ºC. The reaction flask was wrapped with aluminum foil, warmed

to rt and stirred for an additional 20 h. The reaction was quenched with Et 3N (8.0 mL), filtered through Celite, and eluted with EtOAc (50 mL). The filtrate was washed with saturated aqueous NaHCO 3 (20 mL), dried (Na 2SO 4), filtered, and concentrated under reduced pressure. The residue was purified by flash chromatography eluting with

EtOAc/hexanes (1/3) to afford 50% of 2.118 as foam (7:1 dr at C9 by 1H NMR). Major

9(R) isomer: IR (film) 3441, 2956, 2878, 1727, 1462, 1372, 1265, 1178, 1093 cm 1; 1H

NMR (400 MHz) δ 5.65 (dd, J = 16.0, 2.0 Hz, 1H), 5.42 (dd, J = 16.0, 3.6 Hz, 1H), 4.77

(dd, J = 10.0, 2.8 Hz, 1H), 4.55 (dd, J = 10.8, 7.6 Hz, 1H), 4.43 (bs, 1H), 4.25 (d, J = 7.6

Hz, 1H), 4.16 (t, J = 8.8 Hz, 1H), 3.73 (s, 3H), 3.69 (d, J = 8.4 Hz, 1H), 3.473.38 (m,

1H), 3.14 (s, 3H), 2.73 (dt, J = 12.0, 4.2 Hz, 1H), 2.332.30 (m, 1H), 2.28 (s, 6H), 1.97

1.87 (m, 1H), 1.761.30 (m, 6H), 1.26 (s, 3H), 1.22 (d, J = 6.0 Hz, 3H), 1.15 (d, J = 10.4

Hz, 3H) 1.31 (s, 3H), 1.11 (s, 3H), 0.95 (t, J = 8.0 Hz, 9H), 0.90 (t, J = 7.8 Hz, 9H), 0.89

(s, 9H), 0.85 (t, J = 11.4 Hz, 3H), 0.610.52 (m, 12H), 0.11 (s, 3H), 0.06 (s, 3H); 13 C

NMR (100 MHz) δ 175.1, 155.0, 134.4, 132.6, 98.7, 80.1, 79.5, 77.6, 75.5, 74.8, 71.0,

70.1, 68.8, 63.0, 54.6, 48.7, 48.1, 40.5 (2C), 39.9, 30.6, 29.3, 26.3 (3C), 24.8, 22.7, 20.8,

19.3, 18.3, 15.6, 10.9, 7.0 (3C), 6.9 (3C), 6.8, 6.6 (3C), 4.8 (3C), 3.4, 4.2; HRMS (FAB)

+ calc’d for C 47 H93 NO 11 Si 3+H = 932.6134, found 932.6107.

144

OH Diol 2.119: To a solution of 2.118 (135 mg, 0.14

8 mmol) in THF (1.5 mL) at 0 ºC was added TBAF Me HO OMe Me NMe2 (0.92 mL, 0.92 mmol, 1 M in THF). After 30 min, McO Et O 4 O O Me the reaction was quenched with sat’d aq. NaHCO 3 O OTBS Me (4 mL). EtOAc (10 mL) was added. The aqueous 2.119 layer was extracted with EtOAc (2 × 5mL). The combined organic layers were washed with brine (5 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. The residue was purified by flash chromatography

1 eluting with MeOH/CH 2Cl 2 (1/16) to obtain diol 2.119 as a foam (dr = 7:1 at C9 by H

NMR). Major 9(R) isomer: IR (film) 3416, 2959, 2855, 1754, 1731, 1460, 1372, 1268,

1165, 1076 cm 1; 1H NMR (400 MHz) δ 5.745.64 (m, 2H), 4.80 (dd, J = 10.6, 2.2 Hz,

1H), 4.54 (dd, J = 10.6, 7.8 Hz, 1H), 4.32 (d, J = 7.6 Hz, 1H), 4.264.23 (m, 1H), 4.16 (t,

J = 8.4 Hz, 1H), 3.75 (s, 3H), 3.773.73 (m, 1H), 3.453.42 (m, 1H), 3.15 (s, 3H), 2.73

(dt, J = 12.0, 4.2 Hz, 1H), 2.402.36 (m, 1H), 2.27 (s, 6H), 1.91.3 (m, 12H), 1.25 (s, 3H),

1.22 (d, J = 6.0 Hz, 3H), 1.20 (s, 3H), 1.17 (d, J = 9.6 Hz, 3H), 0.89 (s, 9H), 0.890.85

(m, 3H), 0.10 (s, 3H), 0.06 (s, 3H); 13 C NMR (100 MHz) δ 175.5, 155.4, 135.4, 131.7,

98.5, 79.8, 79.4, 77.5, 74.9, 72.8, 71.4, 70.1, 68.7, 63.0, 54.9, 52.0, 48.4, 48.3, 40.4 (2C),

29.1, 26.1 (3C), 26.0, 25.1, 22.3, 20.7, 20.0, 18.1, 15.9, 13.4, 10.5, 3.5, 4.2; HRMS

+ (FAB) calc’d for C 35 H65 NO 11 Si +H = 704.4398, found 704.4405.

145

Ketolactone 2.120 : To a solution of diol 2.119 O

(110 mg, 0.15 mmol) in CH 2Cl 2 (15.6 mL) was 8 Me HO OMe added DMP (132.5 mg, 0.313 mmol). The Me NMe2 McO 4 O Me Et O O reaction mixture was stirred for 4 h at rt, after

O OTBS 2.120 which a mixture of EtOAc (40 mL), sat’d aq. Me

NaHCO 3 (10 mL), sat’d aq. Na 2S2O3 (10 mL) and H 2O (20 mL) was added. The aqueous layer was backextracted with EtOAc (20 mL). The combined organic layers were washed with brine (10 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. The residue was purified by flash chromatography eluting with MeOH/CH 2Cl 2

23 (1:25) to afford 78% of 2.120 as a foam. [α] D 73.0° ( c 1.01, CH 2Cl 2); IR (film) 3441,

2956, 2878, 1727, 1462, 1372, 1265, 1178, 1093 cm 1; 1H NMR (400 MHz) δ 6.76 (d, J

= 16.4 Hz, 1H), 6.17 (d, J = 16.4 Hz, 1H), 4.82 (dd, J = 10.8, 2.0 Hz, 1H), 4.53 (dd, J =

10.8, 7.6 Hz, 1H), 4.29 (d, J = 7.6 Hz, 1H), 4.21 (t, J = 9.0 Hz, 1H), 3.76 (dd, J =10.4, 2.0

Hz, 1H), 3.62 (s, 3H), 3.493.41 (m, 1H), 3.11 (s, 3H), 2.88 (dt, J = 12.6, 3.8 Hz, 1H),

2.76 (dt, J = 11.4, 3.6 Hz, 1H), 2.482.41 (m, 2H), 2.27 (s, 6H), 1.981.88 (m, 2H), 1.79

1.51 (m, 6H), 1.411.34 (m, 1H), 1.34 (s, 3H), 1.231.19 (m, 9H), 0.90 (s, 9H), 0.84 (t, J

= 7.8 Hz, 3H), 0.10 (s, 3H), 0.06 (s, 3H); 13 C NMR (100 MHz) δ 203.3, 175.6, 155.0,

150.7, 127.8, 98.2, 79.6, 78.5, 74.9, 73.2, 71.5, 69.0, 63.0, 54.9, 48.8, 48.4, 40.6 (2C),

40.1, 34.3, 31.8, 30.7, 29.7, 26.2 (3C), 21.9, 20.9, 19.9, 18.3, 17.7, 16.3, 10.3, 3.4, 4.2;

+ HRMS (FAB) calc’d for C 35 H63 NO 11 Si+H = 702.4248, found 702.4241.

146

N Ketolactone 2.122 : To a solution of O N N ( )4 2.120 (85 mg, 0.121mmol) and CDI (104 O N 10 8 Me mg, 0.642 mmol) in DMF (0.1 mL) and O OMe Me NMe2 McO THF (1.1 mL) at 10 ºC was added NaH Et O 4 O O Me

O OTBS (12.1 mg, 0.50mmol). After 30 min, the

Me 2.122 reaction was quenched by dropwise

addition of sat’d aq. NaHCO 3 (3 mL). EtOAc (10 mL) was added, and the aqueous layer

was backextracted with EtOAc (2 x 5 mL). The combined organic layers were washed

with NH 4OH (2 mL), H 2O (5 mL), brine (5 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. To the crude carbamate was added butylamine 2.58

(130.8 mg, 0.60 mmol) in 9:1 MeCN/H 2O (2.5 mL), and the reaction mixture was stirred

for 40 h at rt. The reaction mixture was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with MeOH/CH 2Cl 2 (1:25) to

23 afford 35% of 2.122 as a foam. [α] D +5.8° ( c 0.6, CH 2Cl 2); IR (film) 2935, 2851, 1749,

1704, 1456, 1260, 1105, 1055 cm 1; 1H NMR (400 MHz) δ 8.96 (d, J = 1.6 Hz, 1H), 8.46

(dd, J = 4.4 Hz, 1.6 Hz, 1H), 8.08 (td, J = 7.6 Hz, 2 Hz, 1H), 7.57 (d, J = 1.2 Hz, 1H),

7.34 (d, J = 1.2 Hz, 1H), 7.307.27 (m, 1H), 5.01 (dd, J = 10.6 Hz, 2.2 Hz, 1H), 4.64 (d, J

= 7.6 Hz, 1H), 4.42 (dd, J = 10.4, 7.6 Hz, 1H), 4.094.01 (m, 4H), 3.92 (dd, J = 7.6, 4.0

Hz, 1H), 3.78 (s, 3H), 3.433.46 (m, 2H), 3.09 (s, 3H), 3.04 3.00 (m, 2H), 2.782.62 (m,

3H), 2.40 (dd, J = 16.4, 8.4 Hz, 1H), 2.302.20 (m, 1H), 2.26 (s, 6H), 1.991.51 (m, 11H),

1.391.31(m,1H), 1.30 (s, 3H), 1.26 (s, 3H), 1.231.21 (m, 6H), 0.93 (s, 9H), 0.88 (t, J =

7.4 Hz, 3H), 0.11 (s, 3H), 0.10 (s, 3H); 13 C NMR (100 MHz) δ 208.0, 176.6, 156.4,

155.1, 147.6, 146.4, 139.1, 137.8, 131.9, 130.2, 123.5, 115.4, 98.4, 81.7, 78.0, 75.8, 75.7,

147

70.4, 68.7, 63.9, 57.8, 54.6, 49.5, 46.7, 46.5, 43.6, 41.4, 40.6 (2C), 37.7, 36.6, 30.9, 29.5,

28.3, 28.1, 26.0 (3C), 24.4, 22.5, 21.2, 20.8, 18.1, 16.4, 14.7, 10.3, 4.1, 4.4; HRMS

+ (FAB) calc’d for C 48 H77 N5O12 Si+H = 944.5416, found 944.5416.

Alcohol 2.123 : To a solution of 2.122 N O N N (20 mg, 0.019 mmol) in DMF (0.2 mL) ( )4 O N 10 8 Me and H 2O (0.0034 mL, 0.19 mmol) at rt O OMe Me NMe2 McO was added TASF (0.1 mL, 1M in DMF, Et O 4 O O Me 0.095 mmol). The reaction mixture was O OH 2.123 Me stirred at rt for 16 h. The reaction was

diluted with EtOAc (5 mL) and washed with pH=7 phosphate buffer solution (2 mL). The

aqueous layer was backextracted with EtOAc (2 x 3 mL). The combined organic layers

were washed with H 2O (4 mL), brine (2 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. The residue was purified via flash chromatography eluting with

23 MeOH/CH 2Cl 2 (1:17) to afford 70% of 2.123 as a foam. [α] D 2.9° (c 0.38, CH 2Cl 2); IR

(film) 3427, 2918, 2843, 1753, 1715, 1456, 1264, 1176, 1105, 1034 cm 1; 1H NMR (400

MHz) δ 8.99 (d, J = 1.6 Hz, 1H), 8.44 (dd, J = 4.8, 1.6 Hz, 1H), 8.11 (td, J = 8.0, 2.0 Hz,

1H), 7.58 (d, J = 0.8 Hz, 1H), 7.40 (d, J = 1.2 Hz, 1H), 7.327.28 (m, 1H), 4.94 (dd, J =

10.6, 2.2 Hz, 1H), 4.64 (d, J = 8.0 Hz, 1H), 4.54 (dd, J = 10.2, 8.0 Hz, 1H), 4.134.00 (m,

2H), 3.973.94 (m, 1H), 3.81 (s, 3H), 3.783.70 (m, 2H), 3.583.50 (m, 2H), 3.063.02

(m, 1H), 2.99 (s, 3H), 2.792.68 (m, 2H), 2.532.46 (m, 1H), 2.372.29 (m, 3H), 2.27(s,

6H), 1.951.35 (m, 14H), 1.32 (s, 3H), 1.30 (d, J = 7.2 Hz, 3H), 1.251.22 (m, 6H), 0.88

(t, J = 7.4 Hz, 3H); 13 C NMR (100 MHz) δ 208.0, 176.6, 156.2, 155.3, 147.6, 146.4,

148

139.1, 137.9, 132.0, 130.3, 123.7, 115.5, 101.7, 82.1, 78.6, 77.4, 75.6, 71.3, 69.3, 63.4,

58.1, 54.9, 49.1, 47.6, 46.8, 43.6, 43.0, 41.7, 40.6 (2C), 38.4, 36.5, 30.1, 29.7, 28.3, 24.7,

+ 22.1, 21.1, 18.7, 14.9, 14.8, 10.4; HRMS (FAB) calc’d for C 42 H63 N5O12 +H = 830.4567,

found 830.4551.

N 4,8,10-tridesmethyl telithromycin O N N ( )4 O (2.31) : To a roundbottomed flask N 10 8 Me O OMe wrapped in aluminum foil was added Me NMe2 HO Et O 4 O O Me NCS (14 mg, 0.104 mmol) and CH 2Cl 2

O O (0.8 mL). The mixture was cooled to 0 Me 2.31

ºC, and Me 2S (0.012 mL, 0.169 mmol)

was added. The reaction mixture was stirred for 5 min. After cooling to 20 ºC, 2.123 (15

mg, 0.18 mmol) dissolved in CH 2Cl 2 (1 mL) was added dropwise via cannula. The reaction mixture was stirred for 1.5 h after which Et 3N (25 mg, 0.248 mmol) was added.

The reaction was warmed to rt. After 30 min, the reaction was quenched by adding sat’d aq. NaHCO 3 (2 mL). The mixture was diluted with CH 2Cl 2 (5 mL). The organic layer was washed with sat’d aq. NaHCO 3 (2 mL), brine (2 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. After drying on the high vacuum for 30 min, the residue was dissolved in MeOH (2 mL). The reaction mixture was stirred at rt for 12 h.

The reaction mixture was concentrated, and the residue was purified via flash

23 chromatography eluting with CH 2Cl 2/MeOH (1/8) to afford 45% of 2.31 as a foam. [α] D

8.8° (c 0.125, CH 2Cl 2); IR (film) 3330, 2957, 2847, 1742, 1708, 1632, 1450, 1412, 1174,

1073 cm 1; 1H NMR (400 MHz) δ 8.98 (d, J = 2.0 Hz, 1H), 8.45 (dd, J = 4.8, 1.6 Hz, 1H),

149

8.08 (td, J = 7.6 Hz, 1.8 Hz 1H), 7.58 (d, J = 0.8 Hz, 1H), 7.36 (d, J = 1.2 Hz, 1H), 7.30

(dd, J = 7.6, 4.8 Hz, 1H), 4.94 (dd, J = 9.6, 3.2 Hz, 1H), 4.32 (dd, J = 8.0, 3.0 Hz, 1H),

4.24 (d, J = 7.2 Hz, 1H), 4.093.99 (m, 2H), 3.87 (dd, J = 7.6, 4.2 Hz, 1H), 3.77 (q, J =

7.2 Hz, 1H), 3.583.49 (m, 2H), 3.293.25 (m, 1H), 3.062.88 (m, 3H), 2.81 (s, 3H), 2.68

2.63 (m, 1H), 2.582.38 (m, 2H), 2.34 (s, 6H), 2.031.48 (m, 13H), 1.37 (d, J = 7.2 Hz,

3H), 1.33 (s, 3H), 1.251.22 (m, 6H), 0.89 (t, J = 7.6 Hz, 3H); 13 C NMR (100 MHz) δ

207.4, 202.4, 169.3, 156.5, 147.6, 146.3, 139.2, 138.2, 132.0, 130.2, 123.6, 115.4, 103.2,

81.8, 78.4, 78.1, 69.6, 68.9, 65.6, 58.4, 52.6, 49.8, 46.9, 44.7, 42.0, 41.8, 40.6 (2C), 37.0,

30.6, 29.7, 29.3, 28.1, 24.6, 23.1, 21.1, 18.3, 15.1, 14.1, 10.6; HRMS (FAB) calc’d for

+ C40 H59 N5O10 +H = 770.4324, found 770.4340.

5.4 CHAPTER 3: Synthesis and Biological Evaluation of (-)-4,10-Didesmethyl

Telithromycin

Latone 3.13: To a suspension of K 3Fe(CN) 6 (56.50 g, 171.67 OH 5 6 BnO mmol), K 2CO 3 (23.72 g, 171.67 mmol), (DHQD) 2PHAL (446 Me O 3.13 mg, 0.57 mmol), K 2OsO 2(OH) 4 (42 mg, 0.11 mmol) in tBuOH O

(366 mL) and H 2O (366 mL) at 0 ºC was added MeSO 2NH 2 (5.44 g, 57.22 mmol). The reaction mixture was stirred at 0 ºC until the dissolved salts precipitated out. Olefin 2.72

(15.0 g, 57.22 mmol) was then added to the reaction mixture at 0 ºC and stirred for 36 h at 0 ºC. Sodium sulfite (Na 2SO 3, 65.0 g) was then added to the reaction mixture and

stirred for an additional hour. The mixture was extracted with EtOAc (3 x 400 mL). The

150

combined organic layers were washed with a 2N solution of aq. NaOH (200 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and was purified by flash chromatography eluting with EtOAc/hexanes (1/4) to afford 12.85 g

23 (85%) of 3.13 as an oil. [α] D 6.56° (c 1.6, CH 2Cl 2); IR (film) 3447, 3030, 2932, 2865,

1758, 1496, 1453, 1361, 1207, 1155, 1074, 1028, 943, 739 cm 1; 1H NMR (400MHz) δ

7.377.29 (m, 5H), 4.53 (s, 2H), 3.803.75 (m, 2H), 3.703.65 (m, 1H), 3.23 (d, J = 2.8

Hz, 1H), 2.732.52 (m, 2H), 2.402.32 (m, 1H), 1.931.80 (m, 2H), 1.37 (s, 3H); 13 C

NMR (100 MHz) δ 177.2, 137.6, 128.4 (2C), 127.8, 127.7 (2C), 87.8, 76.2, 73.3, 68.6,

30.5, 30.3, 29.4, 22.6. HRMS (FAB) calc’d for C 15 H20 O4+Na= 287.1259, found

287.1254.

OTES Silyl Ether 3.14 : To the compound 3.13 (9.2 g, 34.8 mmol) 5 6 BnO dissolved in DMF (250 mL), Imidazole (3.32 g, 48.75 mmol) Me O 3.14 O and TESCl (6.3 g, 41.78 mmol) were added at 0 ºC and allowed to warm to room temperature and was stirred for 1.5 h. The reaction was quenched with water (200 mL) and extracted with Et 2O (4 x 200 mL). The combined organic layers were

washed with water (100 mL), brine (200 mL), dried (Na 2SO 4) and filtered. The solvent

was concentrated under reduced pressure, and the residue was purified by flash

chromatography eluting with EtOAc/hexanes (1/4) to afford 11.8 g (90%) of 3.14 as a

23 colorless oil. [α] D +12.9° (c 1.05, CH 2Cl 2); IR (neat) 3521, 3030, 3064, 2953, 2874,

1771, 1496, 1454, 1416, 1385, 1240, 1205, 1113, 1041, 1006, 738 cm 1; 1H NMR (400

MHz) δ 7.327.20 (m, 5H), 4.44 (d, J = 12.0 Hz, 1H), 4.40 (d, J = 12.0 Hz, 1H), 3.77

(dd, J = 9.2, 2.4 Hz, 1H), 3.53 (m, 2H), 2.542.43 (m, 2H), 1.981.25 (m, 3H), 1.511.46 151

(m, 1H), 1.25 (s, 3H), 0.89 (t, J = 8.4 Hz, 9H), 0.650.50 (m, 6H); 13 C NMR (100 MHz)

δ 176.1, 138.1, 128.1 (2C), 127.5 (2C), 127.4, 88.6, 74.6, 72.8, 66.4, 32.7, 30.5, 28.8,

20.1 (3C), 4.8 (3C). HRMS (FAB) calc’d for C 21 H34 O4Si+Na= 401.2124, found

401.2126.

Methyl Silyl Ether 3.8: To a flame dried round bottom OTES 5 6 flask was added THF (60 mL) followed by BnO Me Me O Diisopropylamine (5.45 g, 53.7 mmol). It was cooled to 78 3.8 O ºC and added nBuLi (21.52 mL, 2.17 M solution in hexanes) slowly and stirred for 10 mins at 78 ºC and 20 mins at 0 ºC. It was cooled to

78 ºC before adding 3.14 (13.6 g, 35.92 mmol) in THF (120 mL) via cannula. After 2 h,

MeI (51 g, 359.2 mmol) was added in THF (20 mL) to the reaction mixture and stirred for 30 mins. The reaction mixture was quenched by adding saturated NH 4Cl (100 mL) and diluted with Et 2O (250 mL). The aqueous layer was extracted with Et2O (2 x 75 mL)

and the combined organic layers were washed with brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, dried under high vacuum and preceded to the next step. To the freshly prepared LDA [THF (60 mL), Diisopropyl amine (6.27 g, 61.96 mmol), nBuLi (24.8 mL, 2.17 M solution in hexanes)], was added the residue in THF (120 mL) at 78 ºC. The solution was stirred for 30 mins at 78 ºC and

1.5 h at 45 ºC. Pivalic acid (5.5 g, 53.88 mmol) in THF (20 mL) was then cannulated into the reaction mixture at 78 ºC. After 2 h the reaction mixture was quenched with

NH 4Cl (100 mL) and diluted with Et 2O (250 mL). The aqueous layer was extracted with

Et 2O (2 x 75 mL) and the combined organic layers were washed with brine (100 mL),

dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and 152

the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/25) to

23 afford 8.43 g (60%) of 3.8 as a colorless oil. [α] D +17.6° (c 1.06, CH 2Cl 2); IR (neat)

3088, 3041, 1772, 1494, 1360, 1103, 952, 698 cm 1; 1H NMR (400 MHz) δ 7.327.18 (m,

5H), 4.45 (d, J = 11.6 Hz, 1H), 4.39 (d, J = 11.6 Hz, 1H), 3.72 (dd, J = 9.6, 2.0 Hz, 1H),

3.523.48 (m, 2H), 2.712.66 (m, 1H), 2.00 (dd, J = 12.4, 3.6 Hz, 1H), 1.71.4 (m, 3H),

1.22 (s, 3H), 1.17 (d, J = 7.2 Hz, 3H), 0.88 (t, J = 8.6 Hz, 9H), 0.650.51 (m, 6H); 13 C

NMR (100 MHz) δ 178.5, 138.2, 128.3 (2C), 127.7 (2C), 127.6, 86.1, 75.1, 73.1, 66.6,

39.3, 34.8, 32.6, 18.9, 15.1, 6.9 (3C), 5.0 (3C). HRMS (FAB) calc’d for C 22 H36 O4Si+Na

= 415.2281, found 415.2282.

Mosher ester 3.15. To the ester 3.8 (52 mg, 0.13 mmol) in CF3 Ph OMe THF (1.5 mL) was added TBAF•3H 2O (125 mg, 0.28 O O 5 6 mmol) at 0 ºC. After 30 mins, the reaction was quenched BnO Me Me O by adding H 2O (2 mL), diluted with EtOAc (5 mL) and the 3.15 O aqueous layer was extracted with (2 x 5 mL). The combined organic layers were dried (Na 2SO 4) and filtered. The solvent was evaporated

under reduced pressure dried under high vacuum. The residue was dissolved in CH 2Cl 2

(1.3 mL) and DCC (78.4 mg, 0.38 mmol), (R)3,3,3trifluoro2methoxy2 phenylpropanoicacid (89 mg, 0.38 mmol), DMAP (47 mg, 0.38 mmol) were added at rt and stirred for 20 h. The reaction mixture was then purified by flash chromatography eluting with EtOAc/hexanes (1/4) to afford 39 mg (60%) of 3.15 as a solid. (M.P = 103

23 105 ºC) ; [α] D + 30.3° (c 1.7 CH 2Cl 2); IR (neat) 3064, 3031, 2930, 1775, 1752, 1496,

1452, 1361, 11239, 1169,1109, 1060, 721 cm 1; 1H NMR (400 MHz) δ 7.527.50 (m,

2H), 7.307.18 (m, 8H), 5.35 (dd, J = 10, 2 Hz, 1H), 4.40 (d, J = 12.0 Hz, 1H), 4.34 (d, J 153

= 12.0 Hz, 1H), 3.45 (s, 3H), 3.373.35 (m, 1H), 3.283.23 (m, 1H), 2.732.68 (m, 1H),

2.07 (dd, J = 12.4, 8.8 Hz, 1H), 1.871.77 (m, 1H), 1.691.63 (m, 2H), 1.25 (s, 3H), 1.17

(d, J = 7.2 Hz, 3H); 13 C NMR (100 MHz) δ 177.6, 166.0, 137.9, 131.8, 129.6 (2C),

128.4 (4C), 127.7 (2C), 127.6, 124.7, 121.9, 83.5, 76.7, 73.3, 65.6, 55.5, 39.1, 34.4, 30.2,

29.6, 20.2, 15.1. HRMS (FAB) calc’d for C 26 H29 F3O6+Na = 517.1814, found 517.1832.

TBS Ether 3.16 : To a suspension of LiAlH 4 (0.78 g, OTES TBSO

6 BnO 5 20.52 mmol) in THF (60 mL) at 45 ºC was added ester 9 HO Me Me 3.16 (6.2 g, 15.80 mmol) dissolved in THF (100 mL) dropwise via cannula. After 3h, the reaction mixture was diluted with Et 2O (100 mL) and quenched by adding sat’d aq. Na 2SO 4 (50 mL) dropwise at 0 ºC. The organic layer was decanted,

and the solid was washed with ether (3 x 50 mL). The combined organic layers were

washed with brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, dried under high vacuum, and dissolved in DMF (100 mL).

Imidazole (1.50 g, 22.10 mmol) and TBSCl (2.85 g, 18.95 mmol) were added, and the reaction mixture was stirred for 16 h. The reaction was quenched with water (100 mL) and extracted with Et 2O (4 x 150 mL). The combined organic layers were washed with water (100 mL), brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/25) to afford 6.3 g (78%) of 3.16 as a

23 colorless oil. [α] D +15.8° (c 3.3, CH 2Cl 2); IR (film) 3431, 3030, 2952, 2874, 2856,

1455, 1361, 1250, 1076, 1004, 938, 833,775, 696 cm 1; 1H NMR (400 MHz) δ 7.277.16

(m, 5H), 4.44 (d, J = 9.6 Hz, 1H), 4.40 (d, J = 10.0 Hz, 1H), 3.553.42 (m, 4H), 3.28 (dd,

J = 6, 4.4 Hz, 1H), 1.951.84 (m, 2H), 1.581.42 (m, 2H), 1.331.26 (m, 1H), 1.05 (s, 154

3H), 0.87 (t, J = 8.6 Hz, 9H), 0.84 (s, 9H), 0.590.49 (m, 6H), 0.01 (s, 6H); 13 C NMR

(100 MHz) δ 138.5, 128.2 (2C), 127.6 (2C), 127.3, 77.1, 73.9, 72.8, 69.7, 67.9, 42.0,

33.0, 30.8, 25.8 (3C), 22.8, 19.4, 18.2, 7.0 (3C), 5.3 (3C), 5.5 (2C). HRMS (FAB) calc’d for C 28 H54 O4Si 2+Na= 533.3458, found 533.3439.

Methyl Ether 3.7: To a solution of 3.16 (6 g, 11.72 mmol) OTES TBSO

6 BnO 5 in CH 2Cl 2 (145 mL) was added 2,6DTBMP (24.0 g, 117.21 MeO Me Me

3.7 mmol) and MeOTf (11.5 g, 70.32 mmol). After 48h, the reaction was quenched by adding sat NaHCO 3 (100 mL) stirred for 15 mins followed by

MeOH (100 mL) and stirred for 30 mins. The reaction mixture was then added Et 2O (250

mL) and the aqueous layer was extracted with Et 2O (2 x 150 mL). The combined organic layers were washed with brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure (~100 mmHg), and the residue was purified by flash chromatography. Eluting the column with hexanes enabled to recover the base 2,6-

DTBMP quantitatively!. Further eluting with EtOAc/hexanes (1/25) afforded 5.2 g (76

23 %) of 3.7 as a colorless oil. [α] D +11.0° (c 2.5, CH 2Cl 2); IR (film) 2950, 2929, 2874,

2855, 1461, 1360, 1249, 1093, 1072, 1006, 835, 775 cm 1; 1H NMR (400 MHz) δ 7.27

7.27 (m, 5H), 4.45 (d, J = 12.0 Hz, 1H), 4.41 (d, J = 12.0 Hz, 1H), (m, 1H), 3.83 (dd, J

= 10, 1.6 Hz, 1H), 3.533.47 (m, 2H), 3.363.23 (m, 2H), 3.06 (s, 3H), 1.19 (m, 1H), 1.74

(bs, 1H), 1.05 (s, 3H), 0.88 (t, J = 8.6 Hz, 9H), 0.83 (s, 9H), 0.580.49 (m, 6H), 0.03 (s,

6H); 13 C NMR (100 MHz) δ 138.7, 128.1 (2C), 127.5 (2C), 127.2, 79.5, 73.6, 72.7, 69.1,

67.8, 48.4, 35.7, 32.5, 31.0, 25.9 (3C), 18.3, 17.6, 7.06 (3C), 5.3 (3C), 5.4 (2C). HRMS

(FAB) calc’d for C 28 H54 O4Si 2+Na= 547.3615, found 547.3596.

155

Alcohol 3.17. To a solution of ether 3.7 (5.0 g, 9.52 mmol) OTES TBSO

6 HO 5 in EtOH (100 mL) was added 10% Pd/C (1.0 g, 0.95 mmol) MeO Me Me

3.17 under an atmosphere of H 2. The reaction mixture was followed 48 h (TLC control). The reaction mixture was filtered through a Celite plug,

which had been previously washed with EtOAc. The solvent was concentrated under

reduced pressure, and the residue was purified by flash chromatography eluting with

23 EtOAc/hexanes (0.8:1) to afford 3.3 g (80%) of 3.17 as a colorless oil. [α] D +6.0° ( c 1.1,

CH 2Cl 2); IR (film) 3349, 2929, 2875, 1642, 1376, 1251, 1166, 1062, 835, 775, 740, 666

cm 1; 1H NMR (400 MHz) δ 3.89 (dd, J = 8.8, 3.6 Hz, 1H), 3.783.63 (m, 2H), 3.31 (d, J

= 6.4 Hz, 2H), 3.15 (s, 3H), 1.861.79 (m, 1H), 1.771.69 (m, 1H), 1.631.55 (m, 1H),

1.52 (dd, J = 15.2, 3.2 Hz, 1H), 1.34 (dd, J = 15.2, 8.4 Hz, 1H), 1.07 (s, 3H), 0.95 (t, J =

8.0 Hz, 9H), 0.95 (d, J = 6.4 Hz, 3H), 0.87 (s, 9H), 0.650.56 (m, 6H), 0.02 (s, 6H); 13 C

NMR (100 MHz) δ 79.6, 76.4, 69.1, 60.9, 48.7, 35.7, 34.9, 31.1, 25.9 (3C), 18.5, 17.7,

6.9 (3C), 5.2 (3C), 5.4 (2C). HRMS (FAB) calc’d for C 22 H50 O4Si 2+Na = 457.3145,

found 457.3150.

Aldol 3.19. To a solution of oxalyl chloride (0.97 g, O O OH OTES TBSO

O N 3 5 7.72 mmol) in CH 2Cl 2 (40 mL) at 78 ºC was added Me MeO Me Me Bn 3.19 DMSO (1.25 g, 16.09 mmol) dropwise. After stirring for 10 min, alcohol 3.17 (2.8 g, 6.43 mmol) in CH 2Cl 2 (20 mL) was added via cannula, and the reaction mixture was stirred at 78 ºC for 45 min. Triethylamine (1.62 g, 16.09 mmol) was then added dropwise by cannula, and the reaction mixture was slowly warmed to rt. After 2 h, the reaction was then quenched by adding water (20 mL). The organic layer was separated and washed with brine (20 mL), dried (Na 2SO 4) and 156

concentrated under reduced pressure. The crude product was dissolved in Et 2O (75 mL),

filtered through a plug of silica gel using ether, concentrated and dried under high

vacuum. This material was used directly without further purification. To a solution of

(R)4benzyl3propionyl2oxazolidinone ( 2.81 ) (1.5 g, 6.43 mmol) in CH 2Cl 2 (20 mL) was added dibutylborontriflate (8.4 mL of a 1.0 M solution in CH 2Cl 2, 8.4 mmol) and

triethylamine (1.0 g, 9.7 mmol) dropwise at 0 ºC. The solution was cooled down to 78

ºC and to this was added the aldehyde dissolved in CH 2Cl 2 (10 mL) at 78 ºC. The

resulting solution was stirred for 20 min at 78 ºC. The solution was then warmed to 0 ºC

and stirred an additional hour. The reaction was terminated by adding a pH 7 aq. phosphate buffer solution (0.2 M aq. sodium hydrogen phosphate/0.1 M aq. citric acid,

82:18, 12.8 mL) and methanol (38.5 mL). To this cloudy solution was added a solution of

methanol and 30% hydrogen peroxide (2:1, 38.5 mL) and the resulting solution was

stirred for 1 h at 0 ºC. The solution was concentrated and extracted with EtOAc (3 x 100

mL). The organic layer was washed with sat NaHCO 3 (100 mL), brine (100 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and was purified by flash chromatography eluting with EtOAc/hexanes (2:1) to afford 3.26 g

23 (76%) of 3.19 as a colorless oil. [α] D 35.8° ( c 1.8, CH 2Cl 2); IR (film) 3526, 2950,

2875, 2855, 1780, 1696, 1456, 1381, 1288, 1207, 1237, 1094, 1005, 939, 935, 774, 736,

701 cm 1; 1H NMR (400 MHz) δ 7.387.24 (m, 5H), 4.764.76 (m, 1H), 4.244.15 (m,

3H), 3.99 (dd, J = 9.6, 6.0 Hz, 1H), 3.903.83 (m, 1H), 3.75 (bs, 1H), 3.37 (d, J = 6.0 Hz,

2H), 3.32 (dd, J = 13.2, 2.8 Hz, 1H), 3.18 (s, 3H), 2.81 (dd, J = 13.6, 9.6 Hz, 1H), 1.80

1.42 (m, 6H), 1.31 (d, J = 6.8 Hz, 3H), 1.11 (s, 3H), 1.02 (d, J = 6.4 Hz, 3H), 0.99 (t, J =

8.4 Hz, 9H), 0.93 (s, 9H) 0.720.66 (m, 6H), 0.08 (s, 6H); 13 C NMR (100 MHz) δ 175.8,

157

152.9, 135.2, 129.3 (2C), 128.9 (2C), 127.1, 79.6, 76.8, 71.0, 69.0, 65.9, 55.3, 48.4, 42.6,

37.6, 36.0, 35.4, 31.0, 25.8 (3C), 18.1 (2C), 17.2, 11.0, 6.8 (3C), 5.0 (3C), 5.5 (2C).

HRMS (FAB) calc’d for C 35 H63 NO 7Si 2 +Na = 688.4041, found 688.4028.

Acid 3.6: To a stirred solution of aldol 3.19 (2.8 g, O OTBS OTES TBSO 4.19 mmol) in CH 2Cl 2 (22 mL) at 0 ºC was added HO 3 5 MeO Me Me Me 2,6lutidine (0.80 g, 7.54 mmol) and TBSOTf (1.66 3.6 g, 6.29 mmol). The reaction mixture was stirred for

15 min at 0 ºC and quenched with sat’d aq. NaHCO 3 (10 mL). The organic layer was

separated, washed with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the crude product dissolved in THF/H 2O (4:1,

55 mL). To this was added 30% aq. H 2O2 (0.63 g, 18.54 mmol) and 0.8 M aq. LiOH

(0.28 g, 8.4 mL, 6.77 mmol) at 0 ºC. The reaction was warmed to rt and stirred for 16 h.

The reaction was quenched by adding aq. Na 2SO 3 (1.33 M, 25 mL) and aq. NH 4Cl solution (25 mL). The reaction mixture was then diluted with EtOAc (60mL). The organic layer was separated and the aqueous layer was extracted with EtOAc (2 × 30 mL). The combined organic layers were washed with brine solution (30 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to

23 yield 2.28 g (88%) of 3.6 as a colorless oil. [α] D +7.1° ( c 0.6, CH 2Cl 2); IR (film) 2950,

2928, 2877, 2856, 1706, 1462, 1413, 1387, 1361, 1251, 1171, 1094, 1073, 1047, 1004,

882, 835, 773, 735 cm 1; 1H NMR (400 MHz) δ 4.534.51 (m, 1H), 3.64 (d, J = 10.0 Hz,

1H), 3.35 (dd, J = 9.4, 5.6 Hz, 1H), 3.22 (dd, J = 9.4, 8.0 Hz, 1H), 3.12 (s, 3H), 2.62

2.57 (m, 1H), 1.801.25 (m, 6H), 1.15 (d, J = 6.8 Hz, 3H), 1.05 (s, 3H), 0.97 (t, J = 8.0 158

Hz, 9H), 0.95 (d, J = 6.4 Hz, 3H), 0.88 (s, 9H), 0.85 (s, 9H), 0.700.62 (m, 6H), 0.05 (s,

3H), 0.03 (s, 6H), 0.01 (s, 3H); 13 C NMR (100 MHz) δ 180.3, 79.9, 73.8, 70.3, 69.2, 48.4,

43.5, 37.0, 35.4, 31.3, 25.9 (3C), 25.7 (3C), 18.3, 18.1, 17.9, 16.9, 8.5, 7.1 (3C), 5.3 (3C),

4.1, 5.1, 5.4, 5.5. HRMS (FAB) calc’d for C 31 H68 O6Si 3+Na = 643.4221, found

643.4198.

Et O OTBS OTES TBSO Ester 3.20: To a solution of acid 3.6 (2.4 g,

O 3 5 3.87 mmol) in THF (40 mL) at rt were added HO Me Me MeO Me Me

3.20 Et 3N (0.4 g, 4.05 mmol) and 2,4,6trichloro benzoylchloride (1.03 g, 4.25 mmol). The reaction mixture was stirred for 3 h at rt, and

the solids were filtered and washed with hexanes (40 mL). The combined filtrates were

concentrated under reduced pressure, dried under vacuum, and dissolved in toluene (60

mL). To this solution were added diol olefin 2.64 (0.60 g, 4.64 mmol) in toluene (10 mL)

and DMAP (0.64 g, 5.22 mmol). After being stirred for 16 h at rt, the reaction mixture

was diluted with EtOAc (100 mL), washed with saturated aq. NaHCO 3 (50 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to afford 2.2 g (78 %) of

23 3.20 as a colorless oil. [α] D +24.4° ( c 1.5, CH 2Cl 2); IR (film) 3473, 2950, 2929, 2878,

2855, 1731, 1461, 1411, 1373, 1361, 1250, 1187, 1092, 1073, 1046, 1004, 939, 899, 774,

735 cm 1; 1H NMR (400 MHz) δ 5.87 (dd, J = 17.2 Hz, 10.4 Hz, 1H), 5.30 (dd, J = 17.2,

1.2 Hz, 1H), 5.12 (dd, J = 10.8, 1.2 Hz, 1H), 4.83 (dd, J = 10.4, 3.0 Hz, 1H), 4.554.53

(m, 1H), 3.62 (d, J = 10.0 Hz, 1H), 3.34 (dd, J = 9.6, 6.0 Hz, 1H), 3.22 (dd, J = 9.4, 7.6

Hz, 1H), 3.10 (s, 3H), 2.642.56 (m, 1H), 2.02 (bs, 1H), 1.771.30 (m, 8H), 1.24 (s, 3H),

1.20 (d, J = 7.2 Hz, 3H), 1.02 (s, 3H), 0.94 (t, J = 7.6 Hz, 9H), 0.88 (s, 9H), 0.85.83 (m, 159

12H), 0.680.56 (m, 6H), 0.06 (s, 3H), 0.03 (s, 3H), 0.01 (s, 6H); 13 C NMR (100 MHz): δ

174.9, 141.0, 113.8, 80.4, 79.9, 75.0, 73.8, 69.3, 63.2, 48.3, 42.3, 37.1, 35.4, 31.3, 25.9

(6C), 25.1, 22.4, 18.2, 18.1, 18.0, 17.0, 10.7, 9.3, 7.1 (3C), 5.4 (3C), 3.8, 4.7, 5.4 (2C).

HRMS (FAB) calc’d for C 38 H80 O7Si 3+Na = 755.5110, found 755.5098.

Et O OTBS OTES TESO Ester 3.22 : To a solution of ester 3.20 (1.5 g,

O 3 5 2.04 mmol) in MeOH (41 mL) was added CSA HO Me Me MeO Me Me

3.22 (0.095 g, 0.40 mmol) at 0 ºC. After stirring for 2

h, the reaction was quenched with solid NaHCO 3 (0.20 g). The mixture was concentrated to remove MeOH. The residue was diluted with EtOAc (100 mL) and washed with saturated aq. NaHCO 3 (25 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure dried under high vacuum. The crude alcohol was dissolved in

DMF (2l mL) and was added Imidazole (0.55 g, 8.16 mmol), DMAP (4 mg) and, TESCl

(0.76 g, 5.1 mmol) at 0 ºC and stirred for 5 h at rt. The reaction was quenched with water

(20 mL) and extracted with Et 2O (4 x 50 mL). The combined organic layers were washed with water (50 mL), brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was

concentrated under reduced pressure, and the residue was purified by flash

chromatography eluting with EtOAc/hexanes (1/50) to afford 0.97 g (65%) of 3.22 as a

23 colorless oil. [α] D +14.4° ( c 2, CH 2Cl 2); IR (film) 2952, 2930, 2876, 2856, 1731, 1461,

1413, 1375, 1251, 1093, 1005, 941, 836, 775, 737 cm1; 1H NMR (400 MHz) δ 5.89 (dd,

J = 17.2, 10.8 Hz, 1H), 5.32 (dd, J = 17.2, 1.2 Hz, 1H), 5.14 (dd, J = 10.8, 1.2 Hz, 1H),

4.84 (dd, J = 10.0, 3.6 Hz, 1H), 4.564.53 (m, 1H), 3.63 (d, J = 10.0 Hz, 1H), 3.34 (dd, J

= 9.2, 5.6 Hz, 1H), 3.25 (dd, J = 9.2, 7.6 Hz, 1H), 3.11 (s, 3H), 2.622.60 (m, 1H), 2.03

(bs, 1H), 1.801.30 (m, 8H), 1.25 (s, 3H), 1.21 (d, J = 7.2 Hz, 3H), 1.04 (s, 3H), 0.97 160

0.91 (m, 24H), 088 (t, J = 7.2 Hz, 3H), 0.85 (s, 9H), 0.650.52 (m, 12H), 0.08 (s, 3H),

0.04 (s, 3H); 13 C NMR (100 MHz): δ 174.9, 141.0, 113.8, 80.4, 79.9, 75.0, 73.8, 69.3,

68.9, 48.4, 42.3, 37.1, 35.6, 31.3, 25.8 (3C), 25.2, 22.4, 18.1, 17.1, 10.7, 9.2, 7.1 (3C), 6.8

(3C), 5.4 (3C), 4.3 (3C), 3.8, 4.6. HRMS (FAB) calc’d for C 38 H80 O7Si 3+Na = 755.5110, found 755.5098.

To a solution of ester 3.22 (1.56 g, 2.12 mmol) in a mixture of CH 2Cl 2 /MeOH

(1:1) (350 mL) was added PPTS (0.1 g, 0.42 mmol) at 20 ºC and stirred for 3 h at 20 ºC.

The reaction was quenched with solid NaHCO 3 (0.20 g). The solvent was concentrated

under reduced pressure, and the residue was purified by flash chromatography eluting

with EtOAc/hexanes (1/5) to afford 1.11 g (85%) of 3.21 as a colorless oil.

Et O OTBS OTES HO Alcohol 3.21: To a solution of TBAF•3H 2O

O 3 5 (1.81 g, 5.76 mmol) in DMF (60 mL) was HO Me Me MeO Me Me

3.21 added AcOH (0.36 g, 6.04 mmol). After stirring for 30 min, the solution of 3.20 (1.41 g, 1.92 mmol) was added, and the reaction mixture

was stirred for 20 h at rt. The reaction was quenched with water (60 mL), and the

aqueous layer was extracted with Et 2O (4 x 100 mL). The organic layers were combined and washed with sat’d aq. NaHCO 3 (100 mL), water (100 mL), brine (100 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with EtOAc/hexanes (1/5) to afford

23 0.24 g (20%) of 3.21 as a colorless oil. [α] D +19.6° (c 1.0, CH 2Cl 2) IR (film) 3418,

2952, 2877, 2855, 1729, 1461, 1412, 1374, 1250, 1207, 1094, 1047, 1005, 864, 775, 736

cm 1; 1H NMR (400 MHz) δ 5.87 (dd, J = 17.4, 10.8 Hz, 1H), 5.29 (dd , J = 17.2, 1.8 Hz,

161

1H), 5.11 (dd, J = 10.8, 1.2 Hz, 1H), 4.82 (dd, J = 10.4, 2.8 Hz, 1H), 4.484.40 (m, 1H),

3.66 (m, 1H), 3.67 (d, J = 10.0 Hz, 1H), 3.50 (dd, J = 10.8, 4.4 Hz, 1H), 3.26 (dd, J =

10.8, 4.4 Hz, 1H), 3.16 (s, 3H), 2.632.54 (m, 1H), 2.18 (bs, 1H), 1.931.30 (m, 8H), 1.23

(s, 3H), 1.18 (d, J = 6.8 Hz, 3H), 1.16 (s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.92 (d, J = 6.8

Hz, 1H), 0.84 (s, 9H), 0.860.82 (m, 3H), 0.660.59 (m, 6H), 0.07 (s, 3H), 0.04 (s, 3H);

13 C NMR (100 MHz) δ 174.8, 140.9, 113.8, 80.6, 79.6, 74.8, 73.2, 69.6, 68.8, 49.2, 43.1,

37.7, 37.1, 31.1 25.8 (3C), 24.8, 22.4, 19.0, 18.8, 18.0, 10.6, 9.5, 7.1 (3C), 5.5 (3C), 3.8,

4.6. HRMS (FAB) calc’d for C 32 H66 O7Si 2+Na = 641.4245, found 641.4234.

Aldol 3.23: To a stirred solution of aldol 3.19 (2.35 O O OTBS OTES TESO

O N 3 5 g, 3.53 mmol) in CH 2Cl 2 (20 mL) at 0 ºC was added Me MeO Me Me Bn 3.23 2,6lutidine (0.67 g, 6.35 mmol) and TBSOTf (1.40 g, 5.30 mmol). The reaction mixture was stirred for 15 min at 0 ºC and quenched with sat’d aq. NaHCO 3 (10 mL). The organic layer was separated, washed with brine (10 mL),

dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and

the crude product was azeotroped with Toluene (10 mL). The crude product was

dissolved in MeOH (70 mL) was added CSA (0.16 g, 0.70 mmol) at 0 ºC. After stirring

for 2 h, the reaction was quenched with solid NaHCO3 (0.30 g). The mixture was

concentrated to remove MeOH. The residue was diluted with EtOAc (100 mL) and

washed with saturated aq. NaHCO 3 (25 mL), dried (Na 2SO 4) and filtered. The solvent

was evaporated under reduced pressure dried under high vacuum. The crude alcohol was

dissolved in DMF (35 mL) and was added Imidazole (1.0 g, 14.12 mmol), DMAP (4 mg)

and, TESCl (1.33 g, 8.83 mmol) at 0 ºC and stirred for 5 h at rt. The reaction was

quenched with water (20 mL) and extracted with Et 2O (4 x 100 mL). The combined 162

organic layers were washed with water (100 mL), brine (100 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting with EtOAc/hexanes (1/20) to afford 1.38 g

23 (76%) of 3.23 as colorless oil. [α] D 24.3° ( c 1.15, CH 2Cl 2); IR (film) 2952, 2875, 1784,

1707, 1459, 1380, 1349, 1236, 1207, 1096, 1073, 1006, 971, 812, 775 cm 1; 1H NMR

(400 MHz) δ 7.377.23 (m, 5H), 4.654.61 (m, 1H), 4.334.28 (m, 1H), 4.184.11 (m,

2H), 3.88 (dd, J = 6.8, 2.0 Hz, 1H), 3.783.75 (m, 1H), 3.403.30 (m, 3H), 3.15 (s, 3H),

2.78 (dd, J = 13.2, 9.2 Hz, 1H), 1.981.34 (m, 6H), 1.27 (d, J = 7.2 Hz, 3H), 1.07 (s, 3H),

1.000.95 (m, 24H), 0.93 (s, 9H) 0.690.59 (m, 14H), 0.13 (s, 3H), 0.09 (s, 3H); 13 C NMR

(100 MHz) δ 175.3, 152.9, 135.4, 129.4 (2C), 128.8 (2C), 127.2, 79.8, 73.6, 69.4, 68.9,

65.8, 55.5, 48.3, 42.0, 39.1, 37.6, 35.5, 31.3, 25.8 (3C), 18.2, 18.0, 17.0, 10.4, 7.1 (3C),

6.7 (3C), 5.3 (3C), 4.3 (3C), 4.2, 5.0; HRMS (FAB) calc’d for C 41 H77 NO 7Si 3 +Na =

802.4906, found 802.4914.

Acid 3.25: To the solution of aldol 3.23 (2.4 g, 3.08 O OTBS OTES TESO

HO 3 5 mmol) dissolved in THF/H 2O (4:1, 45 mL) was added Me MeO Me Me 3.25 30% aq.H 2O2 (0.49 g, 14.49 mmol) and 0.8 M aq.

LiOH (0.22 g, 6.5 mL, 5.24 mmol) at 0 ºC. The reaction was warmed to rt and stirred for

16 h. The reaction was quenched by adding aq. Na 2SO 3 (1.33 M, 20 mL) and aq. NH 4Cl solution (20 mL). The reaction mixture was then diluted with EtOAc (50 mL). The organic layer was separated and the aqueous layer was extracted with EtOAc (2 × 30 mL). The combined organic layers were washed with brine solution (30 mL), dried

(Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the

residue was purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to 163

23 yield 2.28 g (88%) of 3.25 as a colorless oil. [α] D +10.4° ( c 1.3, CH 2Cl 2); IR (film)

2952, 2876, 2856, 1706, 1461, 1414, 1376, 1361, 1251, 1171, 1095, 1005, 948, 883, 774 cm 1; 1H NMR (400 MHz) δ 4.514.45 (m, 1H), 3.66 (d, J = 9.6 Hz, 1H), 3.34 (dd, J =

9.6, 6.0 Hz, 1H), 3.24 (dd, J = 9.2, 7.2 Hz, 1H), 3.11 (s, 3H), 2.672.56 (m, 1H), 1.82

1.25 (m, 6H), 1.15 (d, J = 7.2 Hz, 3H), 1.04 (s, 3H), 0.980.90 (m, 22H), 0.85 (s, 9H),

0.680.54 (m, 12H), 0.06 (s, 3H), 0.02 (s, 3H); 13 C NMR (100 MHz) δ 180.2, 79.9, 73.8,

70.3, 68.9, 48.4, 42.5, 37.0, 35.5, 31.4, 25.7 (3C), 18.1, 17.9, 17.1, 8.4, 7.1 (3C), 6.8 (3C),

5.3 (3C), 4.3 (3C), 4.2, 5.1. HRMS (FAB) calc’d for C 31 H68 O6Si 3+Na = 643.4221, found

643.4195.

To a solution of acid 3.25 (1.2 g, 1.93 mmol) in THF (20 mL) at rt were added Et 3N (0.21 g, 2.12 mmol) and 2,4,6trichlorobenzoyl chloride (0.51 g, 2.12 mmol). The reaction mixture was stirred for 3 h at rt, and the solids were filtered and washed with hexanes (20 mL). The combined filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene (30 mL). To this solution were added diol olefin 2.64

(0.31 g, 2.31 mmol) in toluene (10 mL) and DMAP (0.32 g, 2.60 mmol). After being stirred for 16 h at rt, the reaction mixture was diluted with EtOAc (60 mL), washed with saturated aq. NaHCO 3 (30 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and purified by flash chromatography eluting with

EtOAc/hexanes (0.4/1) to afford 1.07 g (76 %) of 3.22 as a colorless oil.

164

Vinyl Ketone 3.26: DessMartin periodinane (0.82 g, 1.93 O

Me mmol) and NaHCO 3 (0.67 g, 8.07 mmol) were suspended in Me HO OMe 6 CH 2Cl 2 (10 mL). Alcohol 3.21 (1.0 g, 1.61 mmol) in Me 5 Et O OTES CH 2Cl 2 (10 mL) was added dropwise via cannula into the

O OTBS reaction mixture. After 1h at rt, the reaction mixture was Me

3.26 added to a mixture of sat’d aq. NaHCO 3 (10 mL), sat’d aq.

Na 2SO 3 (10 mL) and H 2O (20 mL). The mixture was extracted with Et 2O (2 x 40 mL).

The combined organic layers were washed with brine (20 mL), dried (Na 2SO 4) and

filtered. The solvent was concentrated under reduced pressure, dried under vacuum, and

the crude aldehyde was dissolved in THF (63 mL) and cooled to 0 ºC under Argon.

Vinylmagnesium bromide (11.5 mL, 0.7 M in THF, 8.07 mmol) was added dropwise, and

the reaction mixture was stirred for 30 min at 0 ºC. The reaction was quenched with sat’d

aq. NH 4Cl (30 mL). The reaction mixture was diluted with EtOAc (100 mL), and the

aqueous layer was extracted with EtOAc (2 x 50 mL). The combined organic layers were

washed with brine (50 mL), dried (Na 2SO 4) and filtered. The solvent was passed through a short plug of silica gel, concentrated under reduced pressure, and dissolved in CH 2Cl2

(160 mL). DessMartin periodinane (1.36 g, 3.23 mmol) was added at rt, and the reaction mixture was stirred for 2 h. The reaction was quenched with sat’d aq. NaHCO 3 (100 mL).

The organic layer was separated, washed with brine (50 mL), dried (Na 2SO 4) and filtered.

The solvent was concentrated under reduced pressure and purified by flash

chromatography eluting with EtOAc/hexanes (1/13) to afford 0.52 g (50%) of 3.26 as a

23 colorless oil . [α] D +15.4° (c 1.0, CH 2Cl 2) IR (film) 3475, 2952, 2930, 2879, 2856, 1729, 165

1461 1410, 1376, 1251, 1186, 1093, 1005, 836, 775 cm 1; 1H NMR (400 MHz) δ 6.42

(dd, J = 17.6, 10.4 Hz, 1H), 6.25 (dd, J = 17.6, 1.6 Hz, 1H), 5.87 (dd, J = 17.2, 10.8 Hz,

1H), 5.74 (dd, J = 10.8, 1.6 Hz, 1H), 5.30 (dd, J = 17.2, 1.2 Hz, 1H), 5.12 (dd, J = 10.8,

1.2 Hz, 1H), 4.82 (dd, J = 10.4, 3.2 Hz, 1H), 4.484.44 (m, 1H), 3.46 (dd, J = 9.2, 2.4

Hz, 1H), 3.07 (s, 3H), 3.042.97 (m, 1H), 2.512.49 (m, 1H), 2.14 (bs, 1H), 2.112.06 (m,

1H), 1.811.78 (m, 1H), 1.711.44 (m, 5H), 1.23 (s, 3H), 1.17 (d, J = 7.6 Hz, 3H), 1.12

(d, J = 7.6 Hz, 3H), 1.08 (s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.85 (t, J = 7.6 Hz, 9H), 0.85

(s, 9H), 0.650.55 (m, 6H), 0.670.58 (m, 5H), 0.07 (s, 3H), 0.03 (s, 3H); 13 C NMR (100

MHz) δ 203.7, 174.8, 140.9, 135.2, 127.6, 113.8, 80.5, 79.1, 74.9, 74.0, 69.5, 49.0, 43.1,

38.6, 37.7, 36.3, 25.9 (3C), 25.0, 22.4, 19.0, 18.4, 18.0, 10.6, 9.6, 7.1 (3C), 5.4 (3C), 3.8,

4.5. HRMS (FAB) calc’d for C 34 H66 O7Si 2+Na = 665.4245, found 655.4221.

Macrolactone 3.25: To a solution of 3.26 (0.49 g, 0.75 O

Me mmol) in CH 2Cl 2 (76 mL) at rt was added the Grubbs II Me HO OMe 6 catalyst (0.12 g, 0.15 mmol). The reaction mixture was Me 5 Et O OTES stirred for 20 h at rt. The solvent was concentrated under 3 O OTBS reduced pressure, and the residue was purified by flash Me 3.25 chromatography eluting with EtOAc/hexanes (1/5) to afford

23 0.45 g (60%, 90% borsm) of 3.26 as a foam. [α] D +2.0° (c 0.5, CH 2Cl 2); IR (film) 3447,

2954, 2933, 2877 1735, 1672, 1461, 1378, 1252, 1163, 1096, 1057, 981, 729 cm 1; 1H

NMR (400 MHz) δ 6.71 (d, J = 16.0 Hz, 1H), 6.22 (d, J = 16.0 Hz, 1H), 4.82 (dd, J =

10.8, 2.0 Hz, 1H), 4.174.13 (m, 1H), 3.81 (dd, J = 8.8, 6.0 Hz, 1H), 3.12 (s, 3H), 3.01

2.96 (m, 1H), 2.83 (bs, 1H), 2.492.42 (m, 2H), 1.881.77 (m, 2H), 1.611.34 (m, 5H),

1.34 (s, 3H), 1.20 (d, J = 7.2 Hz, 3H), 1.11 (d, J = 7.2 Hz, 3H), 1.06 (s, 3H), 0.96 (t, J = 166

8.2 Hz, 9H), 0.91 (t, J = 7.6 Hz, 3H), 0.86 (s, 9H), 0.700.60 (m, 6H), 0.08 (s, 3H), 0.05

(s, 3H); 13 C NMR (100 MHz) δ 205.2, 175.4, 148.3, 128.9, 80.2, 79.6, 74.4, 73.7, 69.6,

49.1, 48.4, 42.6, 37.4, 37.0, 30.2, 25.9 (3C), 22.0, 20.9, 19.3, 18.0, 15.6, 10.6, 7.1 (3C),

5.2 (3C), 3.9, 4.5. HRMS (FAB) calc’d for C 32 H62 O7Si 2+Na = 637.3932, found

637.3925.

Alcohol 3.27: To a solution of 3.25 (315 mg, 0.51 mmol) OH

Me in MeOH (10 mL) at rt was added CeCl 3•7H 2O (188 mg, Me TESO 11 OMe 0.57 mmol). The reaction mixture was cooled to 60 ºC Me 12 5 Et O OH after which NaBH 4 (22 mg, 0.58 mmol) was added. After 3 O OTBS 30 min, at this temperature, the reaction was quenched by Me 3.27 adding sat’d aq. NH 4Cl (5 mL). Ethyl acetate (20 mL) was added, and the aqueous layer was extracted with EtOAc (2 x 10 mL). The combined organic layers were washed with 1N HCl solution (10 mL), sat’d aq. NaHCO 3 (10 mL),

water (10 mL), brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was dried under vacuum. The residue was

dissolved in CH 2Cl 2 (10 mL) and cooled to 78 ºC after which 2,6lutidine (220 mg, 2.04

mmol) and TESOTf (404 mg, 1.53 mmol) were added. The reaction mixture was stirred

for 1 h at 78 ºC. The reaction was quenched by adding sat’d aq. NaHCO 3 (10 mL). The mixture was extracted with CH 2Cl 2 (10 mL). The organic layer was separated, washed with brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, and the residue was dried under vacuum. The residue was dissolved in

MeOH (75 mL) and cooled to 0 ºC after which PTSA (20 mg, 0.102 mmol) was added.

The reaction mixture was stirred at 010 ºC for 3 h, and the reaction was quenched by 167

adding NaHCO 3 (50 mg). The mixture was concentrated and purified directly by flash

chromatography eluting with EtOAc/hexanes (1/5) to afford 95 mg (30%) of a 3.27 as a

foam (5:2 dr at C9 by 1H NMR). Major isomer: IR (film) 3448, 3357, 2965, 2878, 1727,

1488, 1364, 1372, 1265,1178,1093 cm 1; 1H NMR (400 MHz) δ 5.855.72 (m, 2H), 4.82

4.79 (m, 1H), 4.174.02 (m, 2H), 3.943.76 (m, 1H), 3.12 (s, 3H), 2.742.69 (m, 1H),

2.132.05 (m, 1H), 1.931.37 (m, 7H), 1.32 (s, 3H), 1.18 (d, J = 7.2 Hz, 3H), 1.16 (d, J =

7.2 Hz, 3H), 1.04 (s, 3H), 0.94 (t, J = 8.0 Hz, 9H), 0.87 (t, J = 7.6 Hz, 3H), 0.86 (s, 9H),

0.670.54 (m, 6H), 0.09 (s, 3H), 0.08 (s, 3H); 13 C NMR (100MHz) δ 174.6, 137.8, 131.6,

133.4, 80.4, 78.8, 78.6, 74.7, 74.4, 49.4, 47.4, 35.2, 33.6, 32.7, 25.7 (3C), 21.8, 20.9, 19.6

19.2, 17.9, 15.2, 10.8, 6.9 (3C), 6.6 (3C), 4.2, 4.6. HRMS (FAB) calc’d for

C32 H64 O7Si 2+Na= 639.4088, found 639.4108.

Macrolide 3.28: To a solution of alcohol 3.27

OTES (200 mg, 0.32 mmol) in DMF (3.5 mL) and Me 8 Me CH 2Cl 2 (3.5 mL) at rt were added Imidazole (25 TESO OMe Me NMe2 McO mg, 0.37 mmol) and DMAP (2 mg, 0.01 mmol). Et O 4 O O Me The reaction mixture was cooled to 78 ºC, and O OTBS Me TESCl (53.5 mg, 0.35 mmol) was added. After 3.28 stirring for 4 h at 78 to 30 ºC, the reaction was

quenched by adding sat’d aq. NH 4Cl (5 mL). The mixture was diluted with EtOAc (10 mL), and the aqueous layer was extracted with EtOAc (2 x 5 mL). The combined organic layers were washed with water (10 mL), brine (10 mL), dried (Na 2SO 4) and filtered. The

solvent was concentrated under reduced pressure and azeotroped with toluene (5 mL),

and the crude C5 alcohol was taken to the next step. To a suspension of freshly activated 168

4 Å molecular sieves (3.5 g) and AgOTf (1.6 g, 6.3 mmol) in CH 2Cl 2 (5.5 mL) and

toluene (5.5 mL) was added dropwise by cannula to a solution of C5 alcohol (0.32

mmol), desosamine thiopyrimidine donor 1.48 (0.62 g, 1.92 mmol) and 2,6ditertbutyl

4methylpyridine (394 mg, 1.92 mmol) in CH 2Cl 2 (5.5 mL) at 0 ºC. The reaction flask was wrapped with aluminum foil, warmed to rt and stirred for an additional 20 h. The reaction was quenched with Et 3N (5.0 mL), filtered through Celite, and eluted with

EtOAc (50 mL). The filtrate was washed with saturated aqueous NaHCO 3 (20 mL), dried

(Na 2SO 4), filtered, and concentrated under reduced pressure. The residue was purified by

flash chromatography eluting with EtOAc/hexanes (1/3) to afford 0.15 g (50%) of 3.28 as

a foam (5:2 dr at C9 by 1H NMR). Major C9(R) isomer: IR (film) 3449, 3421, 2845,

2775, 1734, 1726, 1455, 1378, 1222, 1016, 1055, 889, 772 cm 1; 1H NMR (400 MHz) δ

5.70 (d, J = 16.4 Hz, 1H), 5.53 (d, J = 16.4 Hz, 1H), 4.67 (dd, J = 8.4, 3.6 Hz, 1H), 4.51

(dd, J = 10.4, 7.6 Hz, 1H), 4.43 (d, J = 7.6 Hz, 1H), 4.36 (dd, J = 8.0, 3.6 Hz, 1H), 3.99

(dt, J = 8.8, 3.6 Hz, 1H), 3.85 (dd, J = 7.6, 3.2 Hz, 1H), 3.75 (d, J = 4.8 Hz, 1H), 3.71 (s,

3H), 3.513.47 (m, 1H), 3.14 (s, 3H), 2.73 (dt, J = 12.8, 4.2 Hz, 1H), 2.512.48 (m, 1H),

2.28 (s, 6H), 1.971.87 (m, 1H), 1.761.30 (m, 6H), 1.27 (s, 3H), 1.261.22 (m, 9H), 1.22

(s, 3H), 0.95 (t, J = 8.0 Hz, 9H), 0.90 (t, J = 7.8 Hz, 9H), 0.91 (s, 9H), 0.85 (m, 3H),

0.630.52 (m, 12H), 0.11 (s, 3H), 0.12 (s, 3H); 13 C NMR (100 MHz) δ 175.4, 155.1,

136.6, 131.0, 98.7, 82.6, 79.5, 76.4, 75.8, 75.2, 71.5, 68.7, 62.9, 54.5, 49.8, 48.2, 40.6

(2C), 38.4, 35.4, 30.7, 29.6, 26.2 (3C), 23.0, 21.5, 20.9, 18.4, 16.0, 15.8, 11.3, 7.0 (3C),

+ 6.9 (3C), 6.6 (3C), 5.0 (3C), 3.1, 3.8. HRMS (FAB) calc’d for C 48 H95 NO 11 Si 3+H =

946.6291, found 946.6299.

169

O Enone sugar 3.29: To a solution of 3.28 (210 mg,

Me 0.22 mmol) in CH 3CN (44 mL) at 0 ºC was added Me HO OMe Me NMe2 Et 3N (1.3 g, 12.8 mmol) and Et 3N•HF (1.77 g, 11 McO Et O O O Me mmol) in a nalgene container. The reaction was O OTBS

Me allowed to warm to room temperature. After 48h,

3.29 the reaction was quenched with sat’d aq. NaHCO 3

(50 mL) dropwise at 0 ºC. Ethyl acetate (100 mL) was added. The aqueous layer was extracted with EtOAc (2 × 25mL). The combined organic layers were washed with brine

(50 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure and the residue was dried under high vacuum. The residue was dissolved in CH 2Cl 2 (22 mL) was added DMP (186.6 mg, 0.44 mmol). The reaction mixture was stirred for 4 h at rt, after which a mixture of EtOAc (50 mL), sat’d aq. NaHCO 3 (20 mL), sat’d aq. Na 2S2O3 (20 mL) and water (40 mL) was added. The aqueous layer was extracted with EtOAc (2 x 30 mL). The combined organic layers were washed with brine (30 mL), dried (Na 2SO 4),

filtered and concentrated under reduced pressure. The residue was purified by flash

chromatography eluting with MeOH/CH 2Cl 2 (1:25) to afford 94 mg (60%) of 3.29 as a

23 foam. [α] D 3.4° (c 1, CH 2Cl 2); IR (film) 3448, 3394, 3200, 2878, 2994, 2878, 1740,

1722, 1462, 1372, 1265, 1178, 1093, 884 cm 1; 1H NMR (400 MHz) δ 6.67 (d, J = 16.0

Hz, 1H), 6.17 (d, J = 16.0 Hz, 1H), 4.86 (dd, J = 10.8, 2.0 Hz, 1H), 4.50 (dd, J = 10.8,

7.6 Hz, 1H), 4.34 (d, J = 7.6 Hz, 1H), 3.96 (t, J = 8.4 Hz, 1H), 3.81 (s, 3H), 3.653.61

(m, 1H), 3.523.47 (m, 1H), 3.12 (s, 3H), 3.00 (bs, 1H), 2.71 (dt, J = 12.0, 4.0 Hz, 1H),

2.35 (dd, J = 8.4, 5.6 Hz, 1H), 2.29 (s, 6H), 2.162.03 (m, 1H), 1.951.86 (m, 1H), 1.78

1.69 (m, 2H), 1.511.38 (m, 4H), 1.33 (s, 3H), 1.24 (s, 3H), 1.22 (d, J = 6.0 Hz, 3H), 1.17

170

(d, J = 7.2 Hz, 3H), 1.08 (d, J = 7.2 Hz, 3H), 0.920.88 (m, 12H), 0.09 (s, 6H); 13 C NMR

(100 MHz) δ 203.6, 175.9, 155.1, 147.0, 128.0, 98.4, 79.0, 78.1, 77.1, 74.9, 73.6, 71.1,

68.7, 63.2, 54.6, 49.9, 48.1, 40.6 (2C), 40.3, 38.8, 37.7, 30.4, 26.2 (3C), 22.2, 21.8, 21.0,

+ 19.7, 19.6, 18.2, 16.1, 10.6, 3.3, 4.0. HRMS (FAB) calc’d for C 36 H66 NO 11 Si+H =

716.4405 found 716.4393.

Oxazolidininone 3.30 : To a solution of N O 3.29 (85 mg, 0.111 mmol) and CDI (96 N N ( )4 O Me N 10 8 mg, 0.59 mmol) in DMF (1.1 mL) and Me O OMe Me NMe2 THF (0.11 mL) at 15 ºC was added NaH McO Et O 4 O O Me (11.8 mg, 0.50 mmol). After 30 mins, the O OTBS Me reaction was quenched by dropwise 3.30 addition of sat’d aq.NaHCO 3 (3 mL).

EtOAc (10 mL) was added, and the aqueous layer was extracted with EtOAc (2 x 5mL).

The combined organic layers were washed with NH 4OH (2 mL), water (5 mL), brine (5

mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. To the crude

carbamate was added butylamine 2.58 (121 mg, 0.55 mmol) in 9:1 MeCN/H 2O (3 mL), and the reaction mixture was stirred for 48 h at rt. The reaction mixture was concentrated under reduced pressure, and the residue was purified by flash chromatography eluting

23 with MeOH/CH 2Cl 2 (1:25) to afford 47.5 mg (45%) of 3.20 as a foam. [α] D +4.9° (c

0.5, CH 2Cl 2); IR (film) 2964, 2922, 2787, 1732, 1687, 1456, 1260, 1105, 1055, 823, 727

cm 1; 1H NMR (400 MHz) δ 8.94 (d, J = 1.6 Hz, 1H), 8.43 (dd, J = 4.8, 1.6 Hz, 1H), 8.05

(td, J = 8.0, 1.6 Hz, 1H), 7.55 (d, J = 1.2 Hz, 1H), 7.32 (d, J = 1.2 Hz, 1H), 7.297.27 (m,

1H), 4.91 (dd, J = 10.4, 2.0 Hz, 1H), 4.47 (dd, J = 10.4, 7.6 Hz, 1H), 4.32 (d, J = 7.6 Hz, 171

1H), 4.01 (t, J = 7.2 Hz, 2H) 3.94 (d, J = 10.0 Hz, 1H), 3.75 (s, 3H), 3.783.71 (m, 2H),

3.543.46 (m, 2H), 3.093.02 (m, 1H), 2.92 (s, 3H), 2.81 (m, 1H), 2.71 (dt, J = 11.6, 4

Hz, 1H), 2.562.49 (m, 2H), 2.332.18 (m, 2H), 2.27 (s, 6H), 1.981.43 (m, 12H), 1.31 (s,

3H), 1.28 (s, 3H), 1.241.20 (m, 9H), 1.17 (d, J = 7.6 Hz, 3H), 1.05 (d, J = 7.6 Hz, 3H),

0.91 (s, 9H), 0.84 (t, J = 7.2 Hz, 3H), 0.10 (s, 3H), 0.09 (s, 3H); 13 C NMR (100MHz) δ

210.3, 175.8, 156.8, 155.1, 147.5, 146.2, 139.0, 137.8, 132.0, 130.2, 123.5, 115.4, 98.3,

81.9, 78.3, 78.0, 77.6, 75.0, 70.0, 68.9, 62.8, 59.0, 54.6, 50.7, 48.4, 46.8, 44.2, 42.4, 40.5

(2C), 39.9, 36.5, 30.4, 29.6, 28.2, 28.1, 26.1 (3C), 24.4, 22.7, 20.9, 19.8, 18.2, 15.6, 15.0,

10.1, 3.3, 3.9. HRMS (FAB) calc’d for C 49 H79 N5O12 Si+Na = 980.5392 found 980.5408.

Alcohol 3.31: To a solution of 3.30 (20 N O mg, 0.02 mmol) in DMF (0.2 mL) and N N ( )4 O Me N 10 8 H O (0.0036 mL, 0.2 mmol) at rt was Me 2 O OMe Me NMe2 added TASF (0.1 mL, 1M in DMF, 0.1 McO Et O 4 O O Me mmol). The reaction mixture was stirred O OH Me at rt for 16 h. The reaction was diluted 3.31 with EtOAc (5 mL) and washed with pH=7 phosphate buffer solution (2 mL). The aqueous layer was extracted with EtOAc (2

x 3 mL), and the combined organic layers were washed with water (4 mL), brine (2 mL),

dried (Na 2SO 4), filtered and concentrated under reduced pressure. The residue was purified via flash chromatography eluting with MeOH/CH 2Cl 2 (1:17) to afford 12.6 mg

23 (75%) of 3.31 as a foam. [α] D 3.5° (c 0.1, CH 2Cl 2); IR (film) 3493, 2924, 2851, 1751,

172

1715, 1456, 1264, 1374, 1265, 1166, 1105, 1051 cm 1; 1H NMR (400 MHz) δ 9.02 (d, J

= 1.2 Hz, 1H), 8.41 (dd, J = 4.8, 1.2 Hz, 1H), 8.12 (td, J = 8.0, 1.6 Hz, 1H), 7.54 (d, J =

0.8 Hz, 1H), 7.45 (d, J = 1.2 Hz, 1H), 7.317.27 (m, 1H), 4.97 (dd, J = 10.8, 2.0 Hz, 1H),

4.63 (d, J = 7.6 Hz, 1H), 4.52 (dd, J = 17.2, 9.6 Hz, 1H), 4.143.94 (m, 2H), 3.78 (s, 3H),

3.763.70 (m, 2H), 3.61350 (m, 2H), 3.24 (bs, 1H), 2.822.76 (m, 2H), 2.76 (s, 3H),

2.542.51 (m, 1H), 2.45 (dd, J = 9.6, 7.2 Hz, 1H), 2.28 (s, 6H), 2.14 (dd, J = 12.0, 7.2

Hz, 1H), 1.951.88 (m, 2H), 1.801.37 (m, 10H), 1.37 (s, 3H), 1.29 (d, J = 6.8 Hz, 3H),

1.261.17 (m, 9H), 1.04 (d, J = 7.2 Hz, 3H), 0.86 (t, J = 7.4 Hz, 3H); 13 C NMR (100

MHz) δ 211.1, 176.4, 156.4, 155.1, 147.2, 146.4, 138.8, 137.9, 132.0, 130.3, 123.7,

115.7, 99.6, 82.3, 80.4, 77.9, 75.2, 71.8, 69.0, 62.9, 57.8, 54.7, 49.6, 47.6, 46.9, 44.3,

42.4, 40.5 (2C), 38.6, 38.0, 37.0, 30.4, 29.6, 28.4, 25.0, 22.0, 20.1, 19.4, 17.8, 15.0, 14.9,

+ 10.3. HRMS (FAB) calc’d for C 43 H65 N5O12 +H = 844.4717, found 844.4708.

Ketolactone 3.32: To a roundbottomed N O N N flask wrapped in aluminum foil was added ( )4 O Me N 10 8 Me NCS (27.5 mg, 0.20 mmol) and CH 2Cl 2 O OMe Me NMe2 (1.5 mL). The mixture was cooled to 0 ºC McO Et O 4 O O Me and Me 2S (20.6 mg, 0.33 mmol) was O O Me added. The reaction mixture was stirred for

3.32 5 min. After cooling to 20 ºC, 3.32 (25

mg, 0.03 mmol) dissolved in CH 2Cl 2 (2 mL) was added dropwise via cannula. The reaction mixture was stirred for 1.5 h after which Et 3N (48.5 mg, 0.48 mmol) was added.

173

The reaction was warmed to rt. After 30 min, the reaction was quenched by adding sat’d aq. NaHCO 3 (3 mL). The mixture was diluted with CH 2Cl 2 (10 mL). The organic layer was washed with sat’d aq. NaHCO 3 (2 mL), brine (2 mL), dried (Na 2SO 4), filtered and concentrated under reduced pressure. The residue was purified via flash chromatography

23 eluting with MeOH/CH 2Cl 2 (1:17) to afford 70% of 3.32 as a foam. [α] D 2.0° (c 0.1,

CH 2Cl 2); IR (film) 2955, 2916, 2848, 1751, 1722, 1708, 1632, 1462, 1378, 1265, 1172,

1073, 736 cm 1; 1H NMR (400 MHz) δ 8.95 (d, J = 1.6 Hz, 1H), 8.44 (dd, J = 4.8, 1.6

Hz, 1H), 8.07 (td, J = 8.4 Hz, 1.6 Hz 1H), 7.55 (d, J = 1.2 Hz, 1H), 7.32 (d, J = 1.2 Hz,

1H), 7.307.27 (m, 1H), 4.93 (dd, J = 9.6, 3.2 Hz, 1H), 4.48 (dd, J = 10.4, 7.4 Hz, 1H),

4.19 (dd, J = 10.0, 2.4 Hz, 1H), 4.01 (dt, J = 8.4, 2.8 Hz, 2H), 3.81 (s, 3H), 3.763.73 (m

,1H), 3.68 (q, J = 7.2 Hz, 1H), 3.563.49 (m, 2H), 3.09 3.04 (m, 1H), 2.932.85 (m, 2H),

2.762.71 (m,1H), 2.61 (s, 3H), 2.372.32 (m, 2H), 2.28 (s, 6H), 1.991.47 (m, 13H),

1.38 (s, 3H), 1.37 (d, J = 7.2 Hz, 3H), 1.271.22 (m, 6H), 1.07 (d, J = 7.2 Hz, 3H), 0.89

(t, J = 7.6 Hz, 3H); 13 C NMR (100 MHz) δ 210.2, 200.2, 169.0, 156.7, 155.1, 147.6,

146.3, 139.2, 137.8, 131.9, 130.2, 123.5, 115.3, 100.3, 81.4, 79.4, 79.0, 77.6, 74.7, 69.3,

63.1, 59.4, 54.8, 52.4, 50.0, 46.8, 43.7, 43.3, 42.4, 40.5 (2C), 39.8, 36.8, 30.2, 28.2, 24.7,

+ 23.2, 20.9, 18.9, 17.9, 16.4, 15.4, 10.4. HRMS (FAB) calc’d for C 43 H63 N5O12 +H =

842.4571, found 842.4561.

174

4,10tridesmethyl telithromycin ( 2.32 ):

N To the compound 2.32 (10 mg) was O N N O Me added MeOH (2 mL) and stirred at rt for N Me O OMe 12 h. The reaction mixture was Me NMe2 HO Et O O O Me concentrated, and the residue was

O O purified via flash chromatography Me

2.32 eluting with CH 2Cl 2/MeOH (1/8) to

23 afford 60% of 2.32 as a foam. [α] D 25.6° (c 0.125, CH 2Cl 2); IR (film) 3340, 2857,

2747, 1742, 1706, 1622, 1440, 1411, 1155, 1022, 848 cm 1; 1H NMR (400 MHz) δ 8.96

(bs, 1H), 8.45 (dd, J = 4.0 Hz, 1H), 8.07 (td, J = 8.0, 1.6 Hz, 1H), 7.56 (d, J = 0.8 Hz,

1H), 7.33 (d, J = 1.2 Hz, 1H), 7.29 (dd, J = 8.0, 4.8 Hz, 1H), 4.94 (dd, J = 9.6, 2.8 Hz,

1H), 4.22 (t, J = 7.6 Hz, 2H), 4.063.98 (m, 2H), 3.77 (dd, J = 8.8, 2.0 Hz, 1H), 3.7 (q, J

= 6.8 Hz, 1H), 3.583.49 (m, 2H), 3.223.18 (m, 1H), 3.003.00 (m, 2H), 2.91 (dd, J =

17.2, 1.6 Hz, 1H), 2.64 (s, 3H), 2.622.51 (m, 3H), 2.34 (s, 6H), 2.342.27(m, 1H), 1.97

1.53 (m, 13H), 1.37 (d, J = 7.2 Hz, 3H), 1.36 (s, 3H), 1.28(s, 3H), 1.261.23 (m, 6H),

1.37 (d, J = 7.2 Hz, 3H), 0.88 (t, J = 7.6 Hz, 3H); 13 C NMR (100 MHz) δ 210.2, 200.6,

169.1, 156.7, 147.6, 146.3, 139.1, 137.8, 132.0, 130.2, 123.5, 115.4, 103.0, 81.5, 79.5,

79.4, 77.6, 69.5, 69.2, 65.9, 59.2, 52.5, 50.0, 46.8, 44.3, 43.8, 42.3, 40.3 (2C), 36.6, 29.7,

28.2, 24.7, 23.1, 21.1, 18.8, 18.0, 16.0, 15.3, 14.1, 10.6. HRMS (FAB) calc’d for

+ C41 H61 N5O10 +H = 784.4513, found 784.4497.

175

5.5 CHAPTER 4: Progress towards the Synthesis 4-Desmethyl Telithromycin

Ester 4.7 : To a solution of acid 3.6 (0.47 g, Et O OTBS OTES TBSO I O 3 5 0.80 mmol) in THF (8 mL) at rt was added HO Me MeO Me Me 4.7 Me Me Et 3N (0.08 g, 0.84 mmol) and 2,4,6 trichlorobenzoyl chloride (0.21 g, 0.88 mmol). The reaction mixture was stirred for 3 h at rt, and the solids were filtered and washed with hexanes (20 mL). The combined filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene

(12 mL). To this solution was added iododiol 4.6 (0.26 g, 0.96 mmol) in toluene (4 mL)

and DMAP (0.13 g, 1.08 mmol). After being stirred for 16 h at rt, the reaction mixture

was diluted with EtOAc (30 mL), washed with sat’d aq. NaHCO 3 (10 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and the residue purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to afford

23 0.50 g (72 %) of 4.6 as a colorless oil . [α] D +9.2° (c 1.1, CH 2Cl 2); IR (film) 3435, 2931,

2938, 2809, 2855, 1726, 1465, 1251 cm 1; 1H NMR (400 MHz) δ 5.95 (d, J = 1.6 Hz,

1H), 4.65 (dd, J = 10.0, 3.6 Hz, 1H), 4.424.36 (m, 1H), 3.49 (d, J = 9.2 Hz, 1H), 3.25

(dd, J = 9.2, 5.6 Hz, 1H), 3.10 (dd, J = 9.6, 7.6 Hz, 1H), 2.97 (s, 3H), 2.982.95 (m, 1H),

2.57 (d, J = 1.6 Hz, 1H), 2.532.54 (m, 1H), 1.97 (bs, 1H), 1.661.18 (m, 8H), 1.14 (s,

3H), 1.07 (d, J = 7.2 Hz, 3H), 0.89 (s, 3H), 0.81 (t, J = 10.0 Hz, 9H), 0.750.72 (m, 16H),

0.70 (s, 9H), 0.530.43 (m, 6H), 0.62 (s, 3H), 0.10 (s, 3H), 0.11 (s, 6H); 13 C NMR (100

MHz) δ 174.1, 142.1, 99.3, 81.9, 79.1, 76.9, 74.3, 68.7, 67.9, 48.3, 44.5, 36.7, 35.9, 31.1,

29.2, 26.1, 25.8 (3C), 25.6 (3C), 22.6, 19.2, 18.8, 18.1, 18.0, 10.7, 9.8, 7.1 (3C), 5,5 (3C),

176

3.8, 4.5, 5.0 (2C); HRMS (FAB) calc’d for C 39 H81 IO 7Si 3+Na = 895.4232, found

895.4238.

Alcohol 4.8 : To a solution of ester 4.7 (0.58 Et O OTBS OTES HO I g, 0.66 mmol) in MeOH (13 mL) was added O 3 5 HO Me MeO Me 4.8 Me Me CSA (0.030 g, 0.13 mmol) at 0 ºC. After

stirring for 1 h, the reaction was quenched with NaHCO 3 (0.040 g). The mixture was concentrated under reduced pressure, and the residue was dissolved in EtOAc (20 mL) and washed with with sat’d aq. NaHCO 3 (5 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure dried under high vacuum and dissolved in DMF

(7 mL) and cooled 0 ºC. Imidazole (0.18 g, 2.65 mmol), TESCl (0.25 g, 1.66 mmol) and

DMAP (2 mg) was added and stirred for 5 h at rt. After 5 h, the reaction was quenched by with H 2O (7 mL). The aqueous layer was extracted with ether (4 x 10 mL). The combined organic layers were washed with H 2O (10 mL) brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure and the residue is dissolved in a mixture of CH 2Cl 2/MeOH (240 mL, 1:1) and PPTS (66 mg, 0.13 mmol) at

20 °C. After 3 h stirring at 20 ºC, the reaction was quenched with solid NaHCO 3 ( 200

mg) and the solvent was concentrated under reduced pressure and purified by flash

chromatography eluting with EtOAc/hexanes (1/5) to afford 0.15 g (30%) of 4.8 as a

23 colorless oil. [α] D +22.5° (c 4.4, CH 2Cl 2); IR (film) 3458, 2952, 2936, 2908, 2877,

1724, 1461, 1251, 1194, 1094, 1045, 1005, 836, 775, 735 cm 1; 1H NMR (400 MHz) δ

6.10 (d, J = 1.6 Hz, 1H), 4.78 (dd, J = 10.0, 3.2 Hz, 1H), 4.43 (dt, J = 9.2, 3.2 Hz, 1H),

3.69 (dd, J = 10.0, 3.6 Hz, 1H), 3.523.49 (bs, 1H), 3.293.21 (m, 1H), 3.17 (s, 3H), 2.69

(d, J = 1.6 Hz, 1H), 2.642.61 (m, 1H), 2.742.70 (m, 1H), 2.34 (bs, 1H), 1.911.40 (m,

177

8H), 1.27 (s, 3H), 1.19 (d, J = 6.8 Hz, 3H), 1.16 (s, 3H), 0.95 (t, J = 10.0 Hz, 9H), 0.88 (t,

J = 7.2 Hz, 3H), 0.85 (s, 9H), 0.660.58 (m, 6H), 0.08 (s, 3H), 0.05 (s, 3H); 13 C NMR

(100 MHz) δ 174.8, 141.9, 99.8, 80.9, 79.8, 77.9, 73.3, 69.7, 68.9, 49.3, 43.4, 37.7, 37.3,

31.2, 30.2, 26.2, 25.8 (3C), 22.6, 19.1, 18.9, 18.1, 10.7, 9.8, 7.1 (3C), 5,5 (3C), 3.8, 4.5;

HRMS (FAB) calc’d for C 32 H65 IO 7Si 2+Na = 767.3211, found 767.3204.

Macrolide 4.9 : DessMartin periodinane (0.07 g, 0.158 O

Me Me mmol) and NaHCO 3 (0.055 g, 0.658 mmol) were suspended Me HO OMe in CH Cl (2 mL). Alcohol 4.8 (0.10 g, 0.131 mmol) in 6 2 2 Me 5 Et O OTES CH 2Cl 2 (2 mL) was added dropwise via cannula into the 3 O OTBS reaction mixture. After 1 h at rt, the reaction mixture was Me 4.9

added to a mixture of sat’d aq. NaHCO 3 (5 mL), sat’d aq.

Na 2SO 3 (5 mL) and H 2O (10 mL). The mixture was extracted with Et 2O (2 x 20 mL). The combined organic layers were washed with brine (10 mL), dried (Na 2SO 4) and filtered.

The solvent was concentrated under reduced pressure, and the residue was filtered

through a short plug of silica gel using Et 2O (20 mL). This residue was dissolved in

DMSO (54 mL) at rt was added CrCl 2 (0.16 g, 1.31 mmol) and NiCl 2 (0.004 mg, 0.013

mmol). The reaction was stirred for 16 h and quenched by the addition of H 2O (60 mL).

The mixture was diluted with EtOAc (300 mL), and the layers were separated. The organic layer was washed with H 2O (3 x 50 mL). The combined aqueous layers were backextracted with EtOAc (3 x 200 mL). The combined organic layers were washed

with brine (200 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under

reduced pressure, and the residue was dissolved in CH 2Cl 2 (4 mL) and added Pyridine

178

(0.1 mL) followed by DessMartin periodinane (0.07 g, 0.158 mmol). After 1 h at rt, the reaction mixture was added to a mixture of sat’d aq. NaHCO 3 (5 mL), sat’d aq. Na 2SO 3

(5 mL) and H 2O (10 mL). The mixture was extracted with Et 2O (2 x 10 mL). The

combined organic layers were washed with brine (10 mL), dried (Na 2SO 4) and filtered concentrated under reduced pressure and purified by flash chromatography eluting with

EtOAc/hexanes (1/2) to afford 57 mg (dr = 3:1 at C2) (5%) of 4.9 as a foam. IR (film)

3456, 2935, 2901, 1728, 1464, 1252, 1095, 1252, 1118, 1093, 1067 cm 1; 1H NMR (400

MHz) δ 5.66 (d, J = 1.4 Hz, 1H), 4.86 (dd, J = 10.4, 2.8 Hz, 1H), 4.084.04 (m, 1H), 3.84

(dd, J = 8.0, 4.4 Hz, 1H), 3.67 (d, J = 7.2 Hz, 1H), 3.20 (s, 3H), 2.552.52 (m, 1H), 2.27

(bs, 1H), 1.90 (d, J = 1.4 Hz, 1H), 1.801.52 (m, 5H), 1.38 (s, 3H), 1.20 (s, 3H), 1.16 (d, J

= 7.2 Hz, 3H), ), 1.06 (d, J = 6.8 Hz, 3H), 0.95 (t, J = 8.2 Hz, 9H), 0.91 (s, 9H), 0.86 (t, J

= 7.2 Hz, 3H), 0.670.59 (m, 6H), 0.12 (s, 3H), 0.10 (s, 3H); 13 C NMR (100 MHz) δ

208.0, 175.4, 142.6, 138.2, 80.4, 79.5, 74.2, 73.9, 70.8, 48.8, 48.6, 41.3, 35.8, 34.6, 31.9,

25.8 (3C), 22.7, 21.3, 21.1, 17.9, 16.7, 14.1, 12.8, 10.6, 7.2 (3C), 5.4 (3C), 3.7, 4.5;

HRMS (FAB) calc’d for C 33 H64 O7Si 2+Na = 651.4088, found 651.4076.

Ester 4.10 : To a stirred solution of aldol 3.5 (0.85 g, 1.28 mmol) OTBS

Me in CH 2Cl 2 (10 mL) at 0 °C was added 2,6lutidine (0.24 g, 2.30

Me OMe mmol) and TBSOTf (0.50 g, 1.92 mmol). The reaction mixture 6 5 OBn OTES was stirred for 15 min at 0 ºC and quenched with sat’d aq. 3

O OTBS NaHCO 3 (10 mL). The organic layer was separated, washed with Me 4.10

brine (10 mL), dried (Na 2SO 4) and filtered. The solvent was concentrated under reduced pressure, azoetroped with Toluene (3 mL). To BnOH (0.26 g,

179

1.99 mmol) in THF (6.5 mL) was added nBuLi at 0 ºC and stirred for 30 mins. To this solution the residue dissolved in THF (6.5 mL) was cannulated at 78 ºC. The reaction mixture was allowed to warm slowly stirred for 16 h at rt. The reaction was quenched by with NH 4Cl (10 mL). The aqueous layer was extracted with ether (2 x 20 mL). The combined organic layers were washed with brine (10 mL), dried (Na 2SO 4) and filtered.

The solvent was concentrated under reduced pressure and purified by flash

chromatography eluting with Ether/hexanes (1/25) to afford 0.45 g (50%) of 4.10 as a

23 colorless oil. [α] D +19.8° ( c 2.0, CH 2Cl 2); IR (film) 2928, 2877, 2856, 1736, 1462,

1413, 1387, 1361, 1251, 1171, 773, 735 cm 1; 1H NMR (400 MHz) δ 7.397.30 (m, 5H),

5.22 (d, J = 12.4 Hz, 1H), 4.96 (dd, J = 12.0 Hz, 1H), 4.514.46 (m, 1H), 3.58 (d, J =

10.0 Hz, 1H), 3.33 (dd, J = 9.6, 5.6 Hz, 1H), 3.22 (dd, J = 9.2, 7.2 Hz, 1H), 3.01 (s, 3H),

2.622.55 (m, 1H), 1.801.25 (m, 6H), 1.15 (d, J = 7.2 Hz, 3H), 1.02 (s, 3H), 0.94 (d, J =

6.8 Hz, 3H), 0.89 (t, J = 8.0 Hz, 9H), 0.88 (s, 9H), 0.84 (s, 9H), 0.030.02 (m, 9H), 0.03

(s, 6H); 13 C NMR (100 MHz) δ 174.8, 136.0, 128.7 (2C), 128.4 (2C), 128.1, 79.8, 73.7,

73.0, 69.2, 66.6, 48.4, 42.4, 37.3, 35.4, 29.6, 25.9 (3C), 25.7 (3C), 18.2, 18.0, 17.9, 16.9,

8.1, 7.1 (3C), 5.5 (3C), 3.1 (2C), 4.0, 5.5. HRMS (FAB) calc’d for C 38 H74 O6Si 3+Na =

733.4691, found 733.4689.

OH Alcohol 4.11 : To a solution of ester 4.10 (0.38 g, 0.53 mmol) in Me MeOH (11 mL) was added CSA (0.025 g, 0.10 mmol) at 0 ºC. Me OMe 6 5 After stirring for 2 h, the reaction was quenched with solid OBn OH 3 NaHCO 3 (0.10 g). The mixture was concentrated to remove O OTBS Me 4.11

180

MeOH. The residue was diluted with EtOAc (100 mL) and washed with saturated aq.

NaHCO 3 (25 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure residue and purified by flash chromatography eluting with

23 EtOAc/hexanes (1/50) to afford 0.18 g (70%) of 4.22 as colorless oil. [α] D +7.1° (c 6.5,

CH 2Cl 2); IR (film) 2952, 2930, 2876, 2856, 1731, 1461, 1413, 1375, 1251, 1093, 1005,

941, 836, 775, 737 cm 1; 1H NMR (400 MHz) δ 7.267.17 (m, 5H), 5.06 (dd, J = 12.4 Hz,

1H), 4.99 (d, J = 12.4 Hz, 1H), 3.55 (d, J = 10.0 Hz, 1H), 3.41 (dd, J = 10.4, 4.4 Hz, 1H),

3.19 (dd, J = 10.2, 3.6 Hz, 1H), 3.12 (s, 3H), 2.682.63 (m, 2H), 1.781.65 (m, 2H), 1.53

1.45 (m, 1H), 1.36 (d, J = 6.0 Hz, 3H), 1.01 (s, 3H), 1.05 (d, J = 6.0 Hz, 3H), 0.83 (d, J =

6.8 Hz, 3H), 0.77 (s, 9H), 0.00 (s, 3H), 0.04 (s, 3H); 13 C NMR (100 MHz): δ 174.6,

135.9, 128.4 (2C), 128.2 (2C), 128.1, 79.1, 72.6, 72.2, 68.7, 66.2, 49.4, 44.7, 37.9, 35.1,

31.1, 25.7 (3C), 19.2, 18.4, 17.8, 11.7, 4.4, 4.7. HRMS (FAB) calc’d for

C26 H46 O6Si+Na = 505.2961, found 505.2966.

Ester 4.12 : To a solution of alcohol 4.11 (0.20 g, 0.41 mmol) in OTBS Me DMF (4 mL) at rt were added Imidazole (42 mg, 0.62 mmol) and Me OMe 6 TBSCl (75 mg, 0.49 mmol) was added. After stirring for 16 h, the 5 OBn ODes reaction was quenched by adding H 2O (5 mL). The mixture was 3 O OTBS diluted with EtOAc (10 mL), and the aqueous layer was extracted Me 4.12 with EtOAc (2 x 5 mL). The combined organic layers were washed with water (10 mL), brine (10 mL), dried (Na2SO 4) and filtered. The solvent was concentrated under reduced pressure and azeotroped with toluene (5 mL), and the crude

C5 alcohol was taken to the next step. To a suspension of freshly activated 4 Å

181

molecular sieves (4.5 g) and AgOTf (2.1 g, 8.1 mmol) in CH 2Cl 2 (7 mL) and toluene (7

mL) was added dropwise by cannula to a solution of C5 alcohol (0.41 mmol),

desosamine thiopyrimidine donor 1.48 (0.85 g, 2.46 mmol) and 2,6ditertbutyl4

methylpyridine (0.505 g, 2.46 mmol) in CH 2Cl 2 (7 mL) at 0 ºC. The reaction flask was wrapped with aluminum foil, warmed to rt and stirred for an additional 20 h. The reaction was quenched with Et 3N (8.0 mL), filtered through Celite, and eluted with EtOAc (50

mL). The filtrate was washed with saturated aqueous NaHCO 3 (20 mL), dried (Na 2SO 4),

filtered, and concentrated under reduced pressure. The residue was purified by flash

chromatography eluting with EtOAc/hexanes (1/3) to afford 0.20 g (55%) of 4.12 as

23 foam. [α] D 2.8° (c 0.5, CH 2Cl 2); IR (film) 3449, 3421, 2845, 2775, 1734, 1726, 1455,

1378, 1222, 1016, 1055, 889, 772 cm 1; 1H NMR (400 MHz) δ 7.267.20 (m, 5H), 5.08

(d, J = 12.8 Hz, 1H), 4.93 (d, J = 12.4 Hz, 1H), 4.39 (dd, J = 10.8, 7.6 Hz, 1H), 4.29 (d,

J = 7.6 Hz, 1H), 3.61 (s, 3H), 3.51 (dd, J = 7.6, 2.8 Hz, 1H), 3.45 (dd, J = 9.6, 5.2 Hz,

1H), 3.17 (dd, J = 9.6, 7.6 Hz, 1H), 3.153.08 (m, 1H), 3.04 (s, 3H), 2.592.50 (m, 1H),

2.40 (dt, J = 12.0, 4.4 Hz, 1H), 2.14 (s, 6H), 1.941.87 (m, 1H), 1.731.66 (m, 1H), 1.54

1.41 (m, 3H), 1.221.11 (m, 2H), 1.07 (s, 3H), 1.03 (d, J = 6.0 Hz, 3H), 1.02 (d, J = 6.8

Hz, 3H), 0.83 (d, J = 6.8 Hz, 3H), 0.78 (s, 9H), 0.75 (s, 9H), 0.05 (s, 3H), 0.07 (s, 6H),

0.09 (m, 3H); 13 C NMR (100 MHz) δ 174.4, 155.3, 136.0, 128.4 (2C), 128.2 (2C), 128.0,

99.6, 78.6, 76.7, 75.1, 70.9, 68.8, 68.7, 66.2, 62.6, 54.4, 49.8, 43.4, 40.6 (2C), 36.4, 36.3,

31.0, 30.6, 25.9 (3C), 25.7 (3C), 20.9, 19.4, 18.3, 17.9, 8.6, 4.2, 5.2, 5.4 (2C). HRMS

(FAB) calc’d for C 42 H77NO 10 Si 2+Na = 834.4984, found 834.4880.

182

Ester 4.13 : To a solution of ester 4.12 (0.175 Et O OTBS ODes TBSO I g, 0.21 mmol) in EtOH/EtOAc (22 mL, 1:1) O HO Me MeO Me Me 4.13 Me Me was added 20% Pd/C (0.05 g, 0.043 mmol) under an atmosphere of H 2. The reaction mixture was followed 48 h. The reaction mixture was filtered through a Celite plug, which had been previously washed with

EtOAc. The solvent was concentrated under reduced pressure and dissolved in THF (2 mL) at rt was added Et 3N (0.02 g, 0.22 mmol) and 2,4,6trichlorobenzoyl chloride (0.05 g, 0.40 mmol). The reaction mixture was stirred for 3 h at rt, and the solids were filtered and washed with hexanes (10 mL). The combined filtrates were concentrated under reduced pressure, dried under vacuum, and dissolved in toluene (4 mL). To this solution was added iododiol 4.6 (0.07 g, 0.25 mmol) in toluene (1 mL) and DMAP (0.12 g, 0.28 mmol). After being stirred for 16 h at rt, the reaction mixture was diluted with EtOAc (10 mL), washed with sat’d aq. NaHCO 3 (5 mL), dried (Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and the residue purified by flash chromatography eluting with EtOAc/hexanes (0.4/1) to afford 0.15 g (70 %) of 4.13 as a colorless oil.

23 [α] D 9.3° ( c 1, CH 2Cl 2); IR (film) 3445, 2951, 2936, 2909, 2877, 2857, 1729, 1461,

1251, 1192, 1095, 1004, 950, 836, 775 cm 1; 1H NMR (400 MHz) δ 6.10 (d, J = 1.6 Hz,

1H), 4.79 (dd, J = 7.8, 4.8 Hz, 1H), 4.54 (dd, J = 10.8, 7.6 Hz, 1H), 4.44 (d, J = 7.2 Hz,

1H), 4.304.24 (m, 1H), 3.74 (s, 3H), 3.673.64 (m, 1H), 3.53 (dd, J = 9.2, 4.8 Hz, 1H),

3.483.42 (bs, 1H), 3.29 (dd, J = 10.0, 3.2 Hz, 1H), 3.16 (s, 3H), 3.183.14 (m, 1H),

2.762.70 (m, 1H), 2.29 (s, 6H), 2.042.00 (m, 1H), 1.861.46 (m, 8H) 1.32 (s, 3H), 1.24

(s, 3H), 1.22 (d, J = 6 Hz, 1H), 1.20 (s, 3H), 1.14 (d, J = 6.8 Hz, 3H), 0.93 (t, J = 6.4 Hz,

3H), 0.89 (s, 9H), 0.88 (s, 9H), 0.890.88 (m, 3H), 0.09 (s, 3H), 0.07 (s, 3H), 0.03 (s, 6H);

183

13 C NMR (100 MHz) δ 174.4, 155.1, 142.6, 99.5, 99.2, 80.3, 79.0, 77.9, 77.8, 75.2, 71.6,

68.9, 68.8, 62.9, 54.7, 49.8, 44.5, 40.5, 36.5, 35.5, 31.0, 30.5, 30.2, 29.6, 26.4, 26.0 (3C),

25.9 (3C), 22.7, 21.1, 20.9, 19.3, 18.3, 18.1, 11.2, 10.9, 3.6, 4.3, 5.3 (2C); HRMS

(FAB) calc’d for C 43 H84 INO 11 Si 2+Na = 996.4525, found 996.4529.

Alcohol 4.14 : To a solution of ester 4.13 Et O OTBS ODes HO I O (0.235 g, 0.24 mmol) in a nalgene container Me HO Me 4.14 Me MeO Me Me was added THF/Pyridine (10.5 mL, 20:1)

followed by HF•Pyridine (0.41 g, 20.53 mmol) and stirred for 3 h at rt. The reaction

mixture was quenched by adding sat’d aq. NaHCO 3 (25 mL) slowly drop by drop at 0 ºC

until the vigorous reaction seizes. The aqueous layer was extracted with EtOAc (2 x 30

mL) and the combined organic layers at washed with sat’d aq. NaHCO 3 (10 mL), dried

(Na 2SO 4) and filtered. The solvent was evaporated under reduced pressure and the residue purified by flash chromatography eluting with EtOAc/hexanes (4/1) to afford

23 0.175 g (85 %) of 4.14 as a foam. [α] D 6.8° ( c 0.5, CH 2Cl 2); IR (film) 3545, 2963,

2946, 2919, 2857, 2837, 1723, 1720, 1461, 836, 775 cm 1; 1H NMR (400 MHz) δ 6.08 (d,

J = 1.6 Hz, 1H), 4.77 (dd, J = 9.2, 3.6 Hz, 1H), 4.50 (dd, J = 10.4, 7.6 Hz, 1H), 4.43 (d, J

= 7.6 Hz, 1H), 4.244.20 (m, 1H), 3.74 (s, 3H), 3.763.74 (m, 1H), 3.493.43 (m, 2H),

3.26 (dd, J = 10.8, 6.8 Hz, 1H), 3.19 (s, 3H), 2.862.81 (m, 1H), 2.68 (d, J = 1.6 Hz,

1H), 2.712.66 (m, 1H), 2.28 (s, 6H), 2.052.00 (m, 2H), 1.861.46 (m, 8H), 1.29 (s, 3H),

1.25 (s, 3H), 1.21 (d, J = 6 Hz, 1H), 1.14 (d, J = 7.2 Hz, 3H), 0.88 (t, J = 6.4 Hz, 3H),

0.87 (s, 9H), 0.07 (s, 3H), 0.06 (s, 3H); 13 C NMR (100 MHz) δ 174.4, 155.2, 142.5, 99.3

184

(2C), 80.4, 79.2, 77.7, 76.7, 75.1, 71.3, 68.9, 68.5, 62.7, 54.8, 49.8, 44.4, 40.4 (2C), 38.6,

35.4, 31.1, 30.6, 30.2, 29.6, 26.4, 25.8 (3C), 22.7, 20.9, 20.7, 19.5, 19.0, 18.1, 11.3, 10.8,

3.7, 4.3; HRMS (FAB) calc’d for C 37 H70 INO 11 Si+Na = 882.3661, found 882.3654.

185

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