Syntheses of Functionalized Tropones and - McGill Universitydigitool.library.mcgill.ca/thesisfile95133.pdf · Syntheses of Functionalized Tropones and Retinoic Acid Analogs Bin Zhao

Syntheses of Functionalized Tropones and

Retinoic Acid Analogs

Bin Zhao

Department of Chemistry

McGill University

Montreal, Quebec, Canada

September 2010

A thesis submitted to McGill University in partial fulfillment of the

requirements for the degree of a Masters of Science

© Bin Zhao, 2010

2

Abstract

The synthesis of highly substituted tropones is a very difficult task due to the lack

of available synthetic methods. A one pot strategy for formation of cycloheptadiene

acetal using a conjugate addition followed by cross coupling and divinylcyclopropane

rearrangement was explored. Oxidation of the expected product under acidic condition

would in theory afford the desired tropones. Addition of vinyl cuprates to a

cyclopropenone acetal was successfully developed. Also, in a model system, the

subsequent Pd(PPh3)4 catalyzed cross-coupling reaction between a cyclopropyl cuprate

and a vinyl iodide was successful. However, in the desired system, cross- coupling

between vinylcyclopropyl cuprates and the substituted vinyl iodide necessary for

CP-225,917 synthesis could not be achieved.

In a second project, synthesis of hybrid molecules combining a functional unit of

retinoic acid analogs with a functional unit for histone deacetylase activity are

presented. Retinoic acid analogs were synthesized via condensation of tetrahydro-

tetramethylnaphthalene carboxylic acid with aromatic amines possessing Zn binding

functional groups. Additional hybrids were prepared by a metal catalyzed cross

coupling strategy. These hybrid molecules were assessed by collaborators and found

to be fully bifunctional molecules. One structure, a hydroxamic acid analog of known

retinoid TTNN, proved to be particularly effective against several retinoid resistant

cancer cell lines.

3

Résumé

La synthèse de tropones hautement substituées est une tâche particulièrement

difficile dû au manque de méthodes de synthèse appropriées. Nous avons exploré une

stratégie pour la formation d’un acétal cycloheptadiène en une étape, à partir d’une

addition conjuguée, suivie par un couplage croisé et d’un réarrangement de

cyclopropane divinylique. Une oxydation sous conditions acides du produit attendu

pourrait générer des tropones multisubstituées.

L’addition conjuguée de vinyl cuprate sur un acétal de cyclopropénone a été

développée avec succès. De plus, dans un système modèle et grâce à la catalyse par le

Pd(PPh3)4, le couplage croisé entre un cyclopropyl cuprate et un iodure de vinyle a été

réussi. Par contre, le couplage nécessaire pour la synthèse de la molécule CP-225,917,

soit une réaction entre des iodures de vinyle substitués et des vinylcyclopropyl

cuprates, n’a pu être réalisé.

Un second projet comportant la synthèse de molécules hybrides est présenté. Ces

hybrides combinent des groupements fonctionnels d’analogues connus de l’acide

rétinoïque avec des groupements fonctionnels possédant une activité sur les histones

déacétylases. Les analogues de l’acide rétinoïque ont été créés grâce à la condensation

d’acides carboxyliques tétrahydrotétraméthylnaphthalène avec des amines aromatiques

possédant des groupements fonctionnels capables de se lier au zinc. D’autres hybrides

ont été préparés via une stratégie de couplage croisé à l’aide de catalyseur métallique.

Ces hybrides furent testés par des collaborateurs et leur activité bifonctionnelle a été

prouvée.

Une molécule en particulier, un acide hydroxamique analogue du rétinoïde TTNN,

a démontré une efficacité notable contre plusieurs lignées cellulaires cancéreuses

résistantes aux rétinoïdes.

4

Acknowledgements

I would like to acknowledge my supervisor, Prof. James L. Gleason, for providing

me the opportunity to work on this challenging project, as well as his supervision on

my research project.

I would like to thank all the past and present members of the Gleason lab for their

kind of support, including Dr. David Soriano Del Amo, Dr. Marc Lamblin, Erica

Tiong, Rodrigo Mendoza Sanchez, Daniel Rivalti, Melanie Burger, Jean-François

Lacroix, Laurie Lim, Jeffrey St Denis, Joshua Chin and Shuo Xing. Thanks to Dr.

James Ashenhurst and Dr. Tim Cernak who mentored me in the early days of graduate

school. I deeply thank Christian Drouin and Jonathan Hudon for helpful suggestion

and discussion throughout my Master studies.

I would also like to thank Dr. Paul Xia and Dr. Frederick Morin for explaining the

operation of NMR instruments, to Dr. Nadim Saadeh and Dr.Alain LeSimple for

HRMS measurements. Much thanks to Professor Karine Auclair for the use of her

HPLC instrument and Kenward Vong for his assistance in the operation of the HPLC

instrument.

I am very grateful to my parents and my aunt, Yuehua Lu, for their unconditional

love and support. Finally, I want to record my thanks to my wife, Yu Ling Zhang,

whose moral and practical support encourage me to cope with all the pressure over the

past years.

5

Abbreviation

Ac Acetyl

SAHA Suberoylanilide hydroxamic acid

APL Acute Promyelocytic Leukemia

ATRA All-trans-retinoic acid

aq. Aqueous

Br. Broad

Bu Butyl

0C Degree Celsius

d Doublet

δ Chemical shift

DIPEA N,N-Diisopropylethylamine

DMAP 4-(Dimethylamino)pyridine

DMF N,N-Dimethylforamide

DMSO Dimethyl sulfoxide

DPPA Diphenylphosphoryl azide

Equiv Equivalent

Et Ethy

Et3N Triethylamine

EtOAc Ethyl acetate

FMO Frontier molecular orbital

FPP Farnesyl pyrophosphate

GAPs GTPase-activating- proteins

GEFs Guanine Nucleotide Exchange Factors

g Gram

HATs Histone acetyltransferases

6

HDACs Histone deacetylases

HDACis Histone deacetylases inhibitors

HMG-CoA Hydroxymethylglutaryl-coenzyme A

HOMO Highest occupied molecular orbital

HPLC High performance liquid chromatography

4-HPR (4-hydroxyphenyl) retinamide

Hr Hour

HRMS High resolution mass spectroscopy

Hz Hertz

IR Infrared

LBD Ligand binding domain

LUMO Lowest unoccupied molecular orbital

M Molar

m Multiplet

Me Methyl

MeOH Methanol

ACN Acetonitrile

mg milligram

Mg Magnesium

ml milliliter

mmol millimole

mol mole

MS Mass spectroscopy

NaB sodium butyrate

NMR Nuclear magnetic resonance

PH Hydrogen ion concentration

7

Ph Phenyl

ppm Part per million

Pr Propyl

RA Retinoic acid

RAR Retinoic acid receptor

Rf Retention factor

RN1 retinoyloxymethyl butyrate

r.t. Room temperature

SAR Structure-activity relationship

s Singlet

sat. Saturated

SQS Squalene synthase

t Triplet

TBS tert-Butyldimethylsilyl

TBSCI Tert-butyldimethylsilyl chloride

Tf Triflic

TFA Trifluoroacetic acid

THF Tetrahydrofuran

TLC Thin layer chromatography

TSA Trichostatin A

TTNN 5',6',7',8'-Tetrahydro-5',5',8',8'-Tetramethyl(2,2'-binaphthalene)-6-carboxylic

acid

TMS Trimethylsilyl

VDR Vitamin D3 receptor

ZBG Zn binding group

8

Table of Contents

Abstract 2

Résumé 3

Acknowledgements 4

Abbreviations 5

Table of Contents 8

List of Figures 11

List of Schemes 12

Chapter One Synthesis of Functionalized Tropone 14

1. Introduction 14

1.1 CP-225,917 and CP-263,114 14

1.2. Tropone 18

1.3. [6+4] Cycloaddition 20

1.4. Approaches to substituted tropone 24

2. Approaches to desired tropone 27

2.1. Addition reaction in desired system using vinyl cuprate reagent 28

2.2. Cross coupling reaction 30

2.3. Addition reaction in desired system using vinylmagnesium

reagent or vinyllithium reagent

37

9

3. Conclusions 41

Chapter Two Synthesis of Retinoic Acid Analogs 42

1. Introduction 42

1.1 Retinoids 43

1.1.1 Biological roles 44

1.1.2 Mechanism of action 45

1.2. Histone deacetylases (HDACs) and histone deacetylases

inhibitors (HDACis)

47

1.2.1 HDACs 47

1.2.2. HDACis 48

1.3. Problems of retinoid treatment in cancer 49

1.4. Retinoid-HDACi hybrid drugs 49

1.5 Design of RAR agonist/HDACi hybrids 53

2. Synthesis of retinoic acid analogs (75-83) 56

2.1. Synthesis of compound 75 56





10

2.6. Synthesis of compound 80, 81 and 82 65


3. Assay of biological activities 70

4. Conclusions 72

Chapter Three Experimental Section 73

References 107

11

List of Figures

Figure 1. Structure of CP-225,917 (1) and CP-263,114 (2)

Figure 2. Simplified depiction of cholesterol biosynthetic pathway3

Figure 3. Ras switch function in normal untransformed cells6

Figure 4.Structure of colchiicine, purpurogallin, eupenifeldin and hinokitiol

Figure 5. The coefficients of frontier orbital of tropone and cyclopetadiene

Figure 6. Frontier orbital and secondary interaction in [6+4] addition

Figure 7. The structure of all-trans retinoic acid 53

Figure 8. Mechanisms of transcriptional repression and activation by RAR–RXR

heterodimers 52

Figure 9. Chemical Structures of TSA, SAHA, NaB, RN1, TTNN and AM580

Figure 10. The structure of retinoic acid analogs (75-83)

12

List of Schemes

Scheme 1. Retrosynthetic analysis of CP-225,917 (1)

Scheme 2. Resonance between tropone and tropylium ion

Scheme 3. [6+4] cycloaddition of substituted tropone with substituted cyclopetadiene

Scheme 4. [6+4] cycloaddition in model system

Scheme 5. Two selected methods for tropone synthesis and its derivative20

Schem 6. Cycloaddition of acetylene with betaine

Scheme 7. Anicaux’s method to prepare 4-substituted tropone

Scheme 8. Attempt to prepare a highly substituted tropone 32

Scheme 9. Nakamura’s method to prepare cycloheptadienone ketal 41

Scheme 10. Plan for synthesis of desired tropone 6

Scheme 11. Synthesis of 37 and 52

Scheme 12. Addition reaction in desired system

Scheme 13. Synthesis of 44 and 58 and the cross coupling attempt

Scheme 14. Synthesis of vinyliodide 59

Scheme 15. Cross coupling reaction in model system

Scheme 16. Cross coupling reaction in the desired system

Scheme 17. Retrosynthesis of divinylcyclopropane acetal

Scheme 18. Several attempts toward synthesis of divinylcyclopropane acetal

Scheme 19. Plan for synthesis of divinylcyclopropane acetal using Grignard reagent

Scheme 20. Addition reaction in desired system using vinylmagnesium reagent

13

Scheme 21. Addition in desired system using vinyllithium reagent

Scheme 22. Synthesis of 87




Scheme 26. Condensation reaction of aromatic acid 87 and amine 96

Scheme 27. Protection of 96 with TBSCl

Scheme 28. Synthesis of 77 in route a and b




Scheme 32. Negishi cross-coupling reaction between 103 and 108 proves to be problematic







14

Chapter One

Synthesis of Functionalized Tropones

1. Introduction

1.1. CP-225,917 and CP-263,114

In 1997, CP-225,917 (1) and CP-263,114 (2) were discovered by researchers at

Pfizer1 where they were extracted from an unidentified fungus obtained from the twigs

of a juniper tree in Texas. Those molecules, also referred to as the phomoidrides, are

members of the nonadride class of polyketide natural products. After the discovery of

phomoidride A and B, their biological roles were investigated. It was found that they

have inhibitory activities against the mammalian enzymes squalene synthase (SQS)

and Ras farnesyl transferase.1,2

O

O

OH

O

O

HO2C CH3

O

CH3

O

OH

CP-225,917 (1)

O

O

O

O

O

HO2C CH3

OCH3

CP-263,114 (2)

O

14 17

9

14 17

9

(Phomoidride A) (Phomoidride B)

Figure 1. Structure of CP-225,917 (1) and CP-263,114 (2)

High cholesterol is one of the main risk factors for atherosclerotic vascular

diseases, which is the leading cause of death in North America. In cholesterol

15

biosynthesis, hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase is the key

rate-limiting enzyme. Inhibition of this enzyme through the class of drugs known as

statins is one of the most popular means of lowering cholesterol levels in patients with

or at risk of cardiovascular diseases. However, relatively rare side effects with the use

of statins include an increase in liver enzymes and myopathy.3 Therefore, alternative

treatments are desired. Another downstream enzyme in the cholesterol biosynthesis

pathway is squalene synthase, which functions to regulate the first committed step of

hepatic cholesterol biosynthesis at the final branch point of the cholesterol biosynthetic

pathway (Figure 2).3 Squalene synthase catalyzes the reaction of two molecules of

farnesyl pyrophosphate (FPP) to pre-squalene diphosphate, which is then converted to

squalene.4,5

Since squalene is a biochemical precursor to cholesterol, inhibiting

squalene synthase presents an attractive means of cholesterol reduction. Phomoidride

A and B inhibit squalene synthase from rat liver microsomes with IC50 values of 43

μM and 160 μM respectively.2

Ras proteins are critical to the control of normal and transformed cell growth,

which can be highlighted by the fact that they are commonly mutated in about 30% of

human cancers.6 Ras, located at the inner surface of the plasma membrane, is a GTP-

hydrolyzing protein that serves as a molecular switch. In normal untransformed cells,

upon receiving signals from membrane-bound receptors (PDGF, EGF, integrins), Ras

binds to GTP and becomes active by the help of Guanine Nucleotide Exchange Factors

(GEFs). Subsequent GTP hydrolysis to GDP is then induced by GTPase-activating-

16

proteins (GAPs), which returns Ras to its inactive form (Figure 3).6 In the case of

oncogenic mutations, GTP hydrolysis by Ras is prevented. It produces a constitutively

active protein, which stimulates uncontrolled cellular proliferation leading to tumor

formation.7 To perform its cellular function, Ras must be conjugated to lipid and

localized at the plasma membrane. This process is achieved by the help of farnesyl

transferase. Phomoidride A and B inhibit Ras farnesyl transferase with IC50 values of 6

μM and 20 μM respectively.1 Therefore, as inhibitors of farnesyl transferase, which

consequently prevents conditions for Ras activation, phomoidrides have been

considered as potential anti-cancer drugs.

HO2CSCoA

OHO

HMG-CoA

HMG-CoA

reductase

HO2COH

HO

Mevalonic acid

OPP

Farnesyl pyrophosphate

Squalene synthase

Squalene

HH

HOCholestrol

H

Figure 2. Simplified depiction of cholesterol biosynthetic pathway3

17

Ras-GTP Ras-GDP

GADs

GEFs(Active) (Inactive)

Figure 3. Ras switch function in normal untransformed cells6

The structures of CP-225,917 (1) and CP-263,114 (2) were characterized using a

variety of analytical data and extensive NMR analysis, and the absolute

stereochemistry was assigned in the course of a total synthesis by K.C. Nicolaou.8

Both molecules possesses highly oxygenated structural features, including a

bicyclo[4.3.1] ring system, a bridgehead olefin, a lactol or lactol acetal moiety, a

maleic anhydride moiety, a quaternary center at C14, and two olefinic side chains.

CP-225,917 (1) can be converted to CP-263,114 (2) when treated with an acid

(MsOH)9. Likewise for the reverse transformation, compound 2 can be converted to

compound 1 when treated with base (LiOH ).9 This suggests that synthesis of one of

these molecules can provide both compounds.

Owing to their interesting biological properties and more importantly their

structural complexity, the phomoidride molecules have been a target of considerable

synthetic interest. To date, four completed total synthesis have been reported along

with numerous studies directed toward the synthesis of the phomoidride core.10

18

O

O

HO2C

HO2CCH3

O

CH3

O

OH

O

O

O

O

X

O

O

O

X

+

O

O

OH

O

O

HO2C CH3

O

CH3

O

OH

CP-225,917 (1)

26

9

16

13

CH2OTBS

CH2OTBS

[6+4]

56

3

4

Scheme 1. Retrosynthetic analysis of CP-225,917 (1)

Our retrosynthetic analysis of CP-225,917 (1) is shown in Scheme 1.10c

The

synthesis hinges on a [6+4] cycloaddition of a tropone with a substituted

cyclopentadiene to forge the bicyclic core of the molecule. While simple model

tropones have been used in our synthetic studies to date, it is necessary to develop a

synthetic route to 3,4,6-trisubstituted tropone 6, the key building block required for the

projected final total synthesis of the natural product.

1.2. Tropone

Tropone 7, or 2,4,6-cycloheptatrien-l-one, consists of a seven membered ring with

three conjugated double bonds group and a ketone group. The molecule has been

19

known since 1951. Early theoretical research suggested that tropone might have

aromatic characteristics due to the formation of a tropylium ion 8 (Scheme 2).

However, subsequent experimental data suggests that tropone 7 is basically a

conjugated triene ketone with little or no aromatic delocalization.11

OO

7 8

Scheme 2. Resonance between tropone and tropylium ion

The tropone moiety is found in numerous natural products, many of which possess

interesting biological activity, including colchicines (antimitotic agent),12

purpurogallin (antioxidant agent),13,14

hinokitiol (antibacterial/antifungal agent)15

and

eupenifeldin (cytotoxic/antitumor agent)16

(Figure 4). These compounds have attracted

significant synthetic efforts and several completed total synthesis have been

achieved.17

Also, tropone and its derivatives are useful synthetic intermediates for the

introduction of a seven-membered ring into polycyclic molecules. In particularly,

tropone enters into a variety of cycloaddition reaction resulting in the formation of

[6+4], [2+4], [4+2], [3+6], [8+2], [8+3] adducts.

20

O

OMe

MeO

MeO NHAc

Colchicine

OOH

OH

Purpurogallin

O

O

HO

OH

OH

OHO

OOH

Eupenifeldin Hinokitiol

HO

MeO

HO

Figure 4. Structure of Colchiicine, Purpurogallin, Eupenifeldin and Hinokitiol

1.3 [6+4] cycloaddition

The most notable and best explored cycloaddition of tropone is the [6+4] reaction

with dienes. The frontier orbital coefficients of tropone and cyclopetadiene are shown

in Figure 5. From frontier molecular orbital (FMO) theory, it was suggested that C-2

and C-7 of tropone should be the preferential site for cycloaddition reactions.18

The

[6+4] cycloadduct results from the interaction of the tropone LUMO with the HOMO

of cyclopentadiene. The [4+2] cycloadducts may also be formed under conditions of

high temperature and long reaction times. The stereoselectivity of [6+4] addition

favors the exo-adduct 9 rather than endo-adduct 10. This can be explained by the

presence of destabilizing antibonding interactions in the endo transition state (Figure

6).

21

O O.653

-.187-.393

-.093

.326

.521

-.232

-.418

HOMO LUMO

HOMO LUMO

.32

.18

.29

.17

-.393

-.093

.326

-.521

.232

.418

.29

.17

.32

.18

Figure 5. The coefficients of frontier orbital of tropone and cyclopentadiene

O primary bondinginteraction

9Exo transition state

O

antibonding 10

Endo transition syate

O

O

Figure 6. Frontier orbital and secondary interaction in [6+4] addition

The regioselectivity of [6+4] cycloadditions between substituted tropones and

substituted diene can also be predicted by FMO theory.18

Garst has reported that

reaction of electron-poor tropones with electron-rich dienes was governed by primary

22

FMO interactions and provided “even” regioisomers which arises from maximum

overlap of the FMOs of the two addends.19

In this study, “even” regioselectivity is used

to refer to the amount of atoms between the functional groups along the shortest path.

In our preliminary studies, cycloaddition of 3-substituted tropone 11 with

2-triethylsilyloxycyclopentadiene 12 provided cycloadduct 13 in good yield.10c

Similarly, cycloadduct 15 was obtained when 4-substituted tropone 14 was used

(Scheme 3). As with the Garst studies, the [6+4] adduct was the “even” regioisomer in

all the above cases. When diester tropone 16 was used, a 1:1 mixture of regioisomers

was obtained due to the similar orbital coefficient magnitudes at C-2 and C-7 of

tropone. These examples were also the first Lewis acid catalyzed [6+4] cycloadditions

of a tropone with a diene. Based on model studies above, it was obvious that a

successful synthetic strategy towards CP molecule could not include the full maleic

anhydride unit in the tropone, as this would not afford good regioselectivity in the [6+4]

cycloaddition. We thus investigated a simple model where one of the carbonyls would

enter in reduced form. Cycloaddition of trisubstituted tropone 19 with cyclopentadiene

12 successfully afforded sole regioisomer 20 in 75% (Scheme 4).

Encouraged from these studies, we designed a [6+4] cycloaddition strategy which

would employ 3,4,6-trisubstituted tropone 6 with silyloxy diene 5 to provide tricyclic

structure 4, which might be a potential precursor to the bicyclo[4,3,1]decadienone core

of CP 225,917 (Scheme 1). Following formation of a quaternary center carboxylic acid

from C-6 and a maleic anhydride moiety from C-3 and C-4 would finish the

23

installation of left hand half of the CP molecule. Synthesis of highly functionalized

non-symmetrical tropone 6 was thus an important goal for our CP synthesis.

O

EtO2C

11

EtO2C

OOTES

12

ZnCl2, Et2O

13

O

O

EtO2C14

EtO2C

OOTES

12

ZnCl2, Et2O

O

15

O

EtO2C

EtO2C

16

EtO2C

EtO2C

O

OTES

12

ZnCl2, Et2O

O

17

EtO2C

O

18

O

EtO2C

1:1 mixture65% yield

Scheme 3. [6+4] cycloaddition of substituted tropone with substituted cyclopetadiene

24

O

EtO2C

Me

19

Me

EtO2C

O

Me

OTES

12

ZnCl2, Et2O

O

20

Me

Scheme 4. [6+4] cycloaddition in model system

1.4. Approaches to substituted tropones

A number of methods exist for the synthesis of tropone and its derivatives. Two

selected methods are shown in Scheme 5.20

In route A, tropone was prepared by

exhaustive bromination-debromination of cycloheptanone 21 followed by catalytic

reduction. 2-Phenyltropone has been obtained by an adaptation of this method. In route

B, cyclodehydration of compound 23 provides tropone 24. This has been widely used

in the synthesis of aromatic troponoids.

O O O

BrBr

Br21

22 7

Br2

AcOH H2/BaSO4(a)

PPAO

(b)

23 24

COOH

Scheme 5. Two selected methods for tropone synthesis and its derivative

Among the synthetic strategies towards substituted tropones, cycloaddition

25

reaction can be a very powerful method.21-27

For example, Roberts reported that the

cycloaddition of acetylene 25 with1-phenyl-3-hydroxypyridium 26 leads to

cycloadduct 27. Subsequent oxidation with MCPBA produces tropone 16 via

chelotropic loss of nitrosobenzene (Scheme 7).28

However, prior attempts to prepare

our desired tropones using a similar strategy were not very successful, as the

cycloaddition and subsequent oxidation suffered from low reproducibility.

MeO2C CO2Me

NOMeO2C

MeO2C

PhO

MeO2C

MeO2C25 27 16

MCPBA

N

OH

Ph

26

Cl

Schem 6. Cycloaddition of acetylene with betaine

Ring expansion of arenes is also a common route towards the preparation of the

cyclohetatriene system reported in various syntheses.29-33

Among them, Anicaux’s

method attracted our attention34

(scheme 7). It involves the ring expansion reaction of

anisole 28 with ethyl diazoacetate 29 using rhodium acetate as catalyst. The resulting

mixture of ring expanded products is separated and then isomerized via a thermal

1,5-hydrogen shift to produce cycloheptatriene 31. Oxidation of 31 with bromine

provided 4-substituted tropone 14 in good yield, which was used in our model [6+4]

cycloaddition reactions as described above. However, because the required ratio of

anisole to ethyl diazoacetae is a minimum of 20:1, it becomes impractical to prepare

26

desired tropone 6 on multigram scale by adaptation of Anicaux’s procedure.

OMe OMe

EtO2C

[1,5] shift

OMe O

2830 31 14

Rh2TFA4

N2CHCO2Et

29 Br2

EtO2C EtO2C

Scheme 7. Anicaux’s method to prepare 4-substituted tropone

A very recent method for the synthesis of a highly substituted tropone 32 was

investigated by Neenah Navasero within our lab.35

This method started from simple

and commercial materials to prepare linear diene 33, which was subjected to ring

closing metathesis reaction conditions to provide cycloheptene 34. Compound 34 was

oxidized with DMP resulting in cycloheptenone 35 with 48% yield. However,

attempted oxidation with IBX-MPO for form tropones was unsuccessful (Scheme 8).

34 35 32

DMP

IBX-MPO48%

OHOBn

OH

Grubbs 2

3334

BnO

OH

HO

OBnBnO

OH

HO

OBnBnO

OH

O

OBnBnO

O

O

OBnBnO

Scheme 8. Attempt to prepare a highly substituted tropone 32

27

2. Approach to desired tropone 6

As is shown in the examples above, the synthesis of complex tropones are not so

easy to achieve. Thus, my research involved developing an efficient method for the

synthesis of highly functionalized non-symmetrical tropone 6 based on precedent by

the work of Nakamura who reported that hexenyl cuprate 36 undergoes conjugate

addition across the double bond of cyclopropenone acetal 37 to provide cyclopropyl

cuprate 38. Subsequent cross coupling of 38 with hexenyl iodide 39 in the presence of

Pd(Ph3P)4 affords 4,5-dibutylcycloheptadienone acetal 41 in 67% yield via

[3,3]-sigmatropic rearrangement of the intermediate divinylcyclopropane acetal 40

(scheme 9).36

OO

Bu)2CuLi

OO

Bu

Cu

BuI

Pd(PPh3)4

OO

Bu Bu

OO

Bu Bu

36

3738

39

40 41

Scheme 9. Nakamura’s method to prepare cycloheptadienone ketal 41

Inspired by this work, we investigated the possible adaptation of this strategy for

the synthesis of highly functionalized tropones. In theory, formation of

cycloheptadiene acetal 46 (Scheme 10) might be achieved using a conjugate addition

28

of vinyl cuprate 42 to cyclopropenone acetal 37 followed by cross coupling with

triflate funanone 44 and subsequent divinylcyclopropane acetal rearrangement. The

product of this one-pot protocol might then be oxidized under acidic conditions to

afford the desired tropone 6.

TBSO )2CuLi

Pd(PPh3)4

OO

42

37

44

45

O

O

TBSO

O

O

OO

O

O

O

O

46

6

TfO

TBSO

TBSO

O O

OO

Cu

43

TBSO

O

Scheme 10. Plan for synthesis of desired tropone 6

2.1 Addition reaction in desired system using vinyl cuprate reagent

29

The synthesis of cyclopropenone acetal 37 began with commercially available

1,3-dichloroacetone 47. Protection with neopentyl glycol 49 in refluxing toluene and

catalytic p-toluenesulfonic acid with azeotropic removal of H2O afforded

2,2-bis-(chloromethyl)-5,5- dimethyl-1,3-dioxane 50 in 86% yield. Compound 50 was

then treated with sodium amide in liquid ammonia and quenched with ammonium

chloride to provide cyclopropenone acetal 37 in 40% yield37

(Scheme 11).

O

Cl Cl

+

OHOH

TsOH H2O

Toluene

86%

OO

1. NaNH2/Liq.NH3

2.NH4Cl

40%OO

47 50 3749

HI

TMSCl,H2O

NaI, CH3CN

rt., 1hr

TBSCl

imidazoleDMAP

CH2Cl2

48 51

63% over tow steps

ClCl

OHHO I

52

TBSO

Scheme 11. Synthesis of 37 and 52

Vinyl iodide 52 was prepared by Markovnikov addition of hydrogen iodide,

generated in situ from chlorotrimethylsilane/sodium iodide/water, to 3-butyn-1-ol 48 in

acetonitrile at room temperature to form 3-hydroxy-2-iodo-1-butene 51 without further

purified.38

Silylation of 51 with tert-butyldimethylsilyl chloride (TBSCl) in the

presence of catalytic DMAP produced silyl ether 52 in 63% yield over two steps

(Scheme 11).

30

52 53 42

OO

tBuLiEther

CuBr/DMSEther

Ether

OO

TBSOCu

43

NH4Cl

77%

OO

TBSO

56

TBSO I TBSO Li TBSO )2CuLi

37

Scheme 12. Addition reaction in desired system

With compounds 37 and 52 in hand, the cyclopropene addition reaction was

investigated. Vinyllithium 53 could be prepared by lithium-iodide exchange reaction

between 52 and 2.1 equiv of t-butyllithium in diethyl ether at -78 0C. Addition of

vinyllithium 53 to 0.5 equiv of CuBr/DMS generated Gilman type vinylcuprate 42,

which was treated with cyclopropenone acetal 37 to provide presumed vinyl

cyclopropyl cuprate 43. After workup with aqueous ammonium chloride,

vinylcyclopropane acetal 56 was obtained in 77% yield (Scheme 12).

2.2 Cross coupling reaction

With the confirmation that we could add vinyl cuprate to 37, we were in a position

to attempt cross coupling of the presumed intermediate cuprate 43 with vinyl triflate

31

44. The necessary coupling partner 44 was readily prepared in 53% yield by treatment

of tetronic acid 57 with triflic anhydride in methylene chloride.39

Unfortunately,

Pd(PPh3)4 catalyzed cross coupling between the presumed vinyl cyclopropyl cuprate

43, which was prepared as shown in Scheme 12, and triflate funanone 44 did not work

(Scheme 13). When bromo-funanone 58, which was prepared by bromination of

tetronic acid with oxalyl bromide/DMF40

, was used, cross coupling also failed

(Scheme 13).

OO

TBSOCu

43

Tf2O

DIPEA44 X=OTf 53%58 X=Br 69%

O

X

O

Pd(PPh3)4

OO

O

O

(a)

(b)

or (CoBr)2

DMF

42 + 3744 or 58

O O

HO

O O

X

TBSO

57

Scheme 13. Synthesis of 44 and 58 and the cross coupling attempt

As an alternative to 4-substituted funanones, we chose to investigate vinyl iodide

59 as reactant in the cross coupling. The synthesis of vinyl iodide 59 started by

diprotection of 1,4-butyndiol 60 with tert-butyl dimethylsilyl chloride (TBSCl) to give

the bis(silyl) ether 61 in 96% yield. Hydrostannation of the protected acetylene

derivative 61 in the presence of PdCl2(PPh3)2 catalyst provided the vinylstannane 62

with the (E) configuration in 79% yield. Subsequent iododestanylation was carried out

32

using iodine in ether at room temperature producing vinyl iodide 59 in 82% yield

(scheme 15).41

HO OH TBSO OTBS

OTBSTBSO

SnBu3

OTBSTBSO

I

TBSClImidazole

CH2Cl2

96%

Bu3SnH

PdCl2(PPh3)4

THF

79%

I2ether

60 61

6259

Scheme 14. Synthesis of vinyliodide 59

To test cross-coupling of vinyl iodide 59, we prepared a simple cyclopropyl

cuprate by addition of lithium dibutyl cuprate to cyclopropene 37. To our delight, the

Pd(PPh3)4 catalyzed cross coupling of intermediate cuprate 63 with vinyl iodide 59

afforded disubstituted-cyclopropane acetal 64 in 67% yield (Scheme 15).

Unfortunately, this cross coupling process did not extend to cuprate 43, derivated from

addition of vinyl cuprate 42 to 37 (Scheme 16). Several catalysts, such as

Pd2(dba)3/PPh3, Pd(OAc)2/PPh3, Pd(OAc)2/dppe and Pd(OAc)2/PBu3, were examined,

but none gave any desired product.

33

OOCuBr/DMSEther

Ether

OO

Bu Cu

63

OTBSTBSO

I

64

59

THF

67%

Pd(PPh3)4

Li )2CuLi37

OO

Bu

OTBS

OTBS

Scheme 15. Cross coupling reaction in model system

OO

TBSOCu

43

OO

TBSO

OTBS

OTBS

OTBSTBSOI

59

Pd(PPh3)4

THF

42 +37

Scheme 16. Cross coupling reaction in the desired system

Based on the above results, it appeared impossible to introduce the second vinyl

group at the 2-position of 1-substituted cyclopropane acetal molecule by cross

coupling of a vinylcyclopropyl cuprate 43 and vinyl iodide 59. Thus, three alternative

strategies for preparation of a functionallized divinylcyclopropane acetal were

34

considered. The first strategy involved conversion of vinyl cyclopropyl cuprate 43 to

66 followed by Pd-catalyzed cross coupling with an organometallic desired from vinyl

iodide 59 (Scheme 17a). The second strategy involved regioselective addition of 43 to

3-phenylselanylfuran- 2(5H)-one followed by selenoxide syn-elimination with NaIO4

in MeOH/H2O42

(Scheme 17b). The third strategy involved cis-conjugate addition to

methyl-2-butynoate 70 (Scheme 17c).

35

O O

OTBSO

O

OO

TBSO

OTBS

OTBS

OO

TBSOI

OTBS

OTBS

MOO

TBSOCu

(a)

OO

TBSO(b)O

O

OO

TBSO

O

OPhSe

OO

TBSOCu

O

PhSe

O

46 65

6643

46

45

6743 68

(c) 46

OO

TBSO

69

Me

OMe

O

MeO

O

Me

OO

TBSOCu

43

70

+

+

+

Scheme 17. Retrosynthesis of divinylcyclopropane acetal

36

The first step of each strategy was investigated but, as shown in scheme 18, each

was unsuccessful. In reaction a, treatment of intermediate cuprate 43 with iodine in

ether at room temperature afforded no iodinate products. In reaction b, regioselective

addition of intermediate cuprate 43 to 3-phenylselanylfuran- 2(5H)-one did not provide

the desired product 67. In reaction c, conjugate addition of intermediate cuprate 43 to

methyl-2- butynoate 70 also failed to produce expected product. Addition, no

identifiable product was isolated from above reaction a, b and c. We decided not to

make further attempt to investigate these reaction on our part.

OO

TBSOCu

43

(a)

I2,

ether OO

TBSOI

66

OO

TBSOCu

43

(b)

OPhSe

OOO

TBSO

O

OPhSe

67

OO

TBSOCu

43

(c)

MeO

O

Me70OO

TBSO

69

Me

OMe

O

68

Scheme 18. Several attempts toward synthesis of divinylcyclopropane acetal

37

2.3 Addition reaction in desired system using vinylmagnesium reagent or

vinyllithium reagent

It was obvious that a new efficient method was required for preparation of a

divinylcyclopropane acetal. A new plan, which was also inspired by Nakamura et.

al43

, involved a iron-catalyzed olefin carbometalation of a vinyl Grignard reagent with

37 which would yield a cyclopropyl grignard which might undergo addition to ketones.

Subsequent elimination of the tertiary alcohol would then produce a divinyl

cyclopropane for rearrangement(Scheme 19).

TBSO MgX

O O

FeCl3THF

-40 0C

O O

TBSOMgX

37

O O

TBSO

HO

OTBS

OTBS

O O

TBSO

HO

OTBS

OTBS

OTBS

O

TBSO71

Scheme 19. Plan for synthesis of divinylcyclopropane acetal using Grignard reagent

In order to test the feasibility of this new plan, we first undertook a study of

38

iron-catalyzed additions of vinyl Grignard to 37. We investigated three methods to

prepare the necessary vinyl magnesium reagent. These included the direct formation

using magnesium turnings, metal-halogen exchange with complex i-PrMgCl/LiCl44

and lithiation of vinyliodide 52 followed by transmetalation45

with freshly prepared

MgBr2. Subsequent addition of the vinylmagnesium reagent to cyclopropenone acetal

37 in presence of catalyst FeCl3 at -40 0C followed by workup with aqueous NH4Cl led

to vinylcyclopropane acetal 56 in 1%, 22% and 11% yield, respectively (Scheme 20).

39

TBSO I TBSO MgI52 72

MgTHF

O O

37 O O

TBSOMgI

O O

TBSO

NH4Cl

56 1% Yield

TBSO I TBSO MgCl

52 73

iPrMgCl/LiCl

THF

-40 0C O O

TBSOMgCl

O O

TBSO

NH4Cl

56

TBSO I TBSO MgI

52 74

tBuLi

ether

-70 0C

O O

O O

TBSOMgBr

O O

TBSO

56

22% Yield

TBSO Li53

MgBr2

ether

-70 0C

37

11% Yield

NH4Cl

a)

b)

O O

37

c)

Scheme 20. Addition reaction in desired system using vinylmagnesium reagent

40

We also attempted to use a vinyllithium reagent instead of the Grignard reagent.

Lithiation of vinyliodide 52 with t-BuLi led to the vinyllithium reagent 53. Addition of

53 to cyclopropenone acetal 37 in presence of catalyst FeCl3 at -700C followed by

workup with aqueous NH4Cl led to vinylcyclopropane acetal 56 in 6% yield. When the

catalyst Fe(acac)3 was used, the yield was 2% (Scheme 21). If no catalyst was used, no

addition was observed.

TBSO I52

tBuLi

ether

-70 0C

TBSO Li53

O O

FeCl3 or Fe(acac)3

THF,-70 0C

37

O O

TBSOLi

O O

TBSO

NH4Cl

56

2-6 % Yield

Scheme 21. Addition reaction in desired system using vinyllithium reagent

3. Conclusion

Attempts to prepare cycloheptadienes relevant to the synthesis of CP 225,917 have

been described. The synthetic route involved an addition reaction followed by cross

coupling and divinylcyclopropanone acetal rearrangement. Addition of vinyl cuprate

41

42 to cyclopropenone acetal 37 provided a simple vinyl cyclopropane in good yield.

When vinylmagnesium and vinyllithium reagents were used to replace vinyl cuprate

42, only low yield of addition products were obtained. In a model system, the

Pd(PPh3)4 catalyzed cross coupling reaction between butylcyclopropyl cuprate 63 and

vinyl iodide 59 produced disubstituted-cyclopropane acetal 64 in good yield. However,

in the desired system, the Pd(PPh3)4 catalyzed cross coupling reaction between 43 and

59 was unsuccessful.

42

Chapter Two

Synthesis of Retinoic Acid Analogs

1. Introduction

Cancer cells typically show altered cell morphology and physiology when

compared to normal cells as they display lower levels of differentiation and higher

levels of proliferation.46

Several forms of cancer, such as acute promyelocytic

leukemia, have been linked to decreased gene transcription,47

resulting in decreased

cell differentiation and uncontrolled growth.48

In the human acute leukemias,

chromosomal translocations in the genes encoding for transcription factors, including

T-cell acute lymphocytic leukemia 1 (TAL1), LIM domain only 2 (LMO2), acute

myeloid leukemia 1 (AML 1) and core-binding factor subunit beta (CBFβ), results in

altered regulatory activity thus interfering in the growth, differentiation and survival of

normal blood cell precursors.49,50

Abnormal activities of oncogenic and tumor

suppressive transcription factors have also been connected with solid tumor

pathogenesis.50

The relationship between growth, differentiation, neoplastic

transformation, and the expression of genes and tumor suppressor genes is complex.47

However, from recent knowledge of their underlying mechanisms, modulation of the

growth and differentiation of tumor cells is possible by various therapeutic strategies.

Differentiation therapy is an approach that can be described as a method to resume

normal growth patterns of cancerous cells. This is based on the concept that cancer

cells are arrested in an immature state that leads to the inability to control cell growth.

43

With the application of differentiation therapy, the process of maturation within these

cells is revived, leading to the halt of uncontrollable cell proliferation.46,47

Retinoids

induce regulatory functions in cell differentiation, proliferation, apoptosis and

morphogenesis in vertebrates, and have been known as popular

differentiation-inducing agents. 47

Retinoic acid is in clinical use for treatment of acute

promyelocytic leukemia (APL) and it and its analogs have been investigated for a

range of cancers.46

Histone deacetylase inhibitors (HDACis) are also considered as

differentiation-inducing agents because they are transcriptional modulators.47

1.1 Retinoids

Retinoids are a group of signaling molecules that function by interacting with

nuclear retinoid (RARα, RARβ and RARγ ) and rexinoid (RXRα, RXRβ and RXRγ )

receptors to regulate transcription.51

RARs are members of the superfamily of nuclear

homone receptors that work as RA inducible transcriptional activators. They function in

a heterodimeric form with retinoid-X-Receptors (RXRs) to upregulate transcription of

genes in the vicinity of retinoic acid response elements.50

Natural retinoids are normally obtained from dietary vitamin A, which is rich in

eggs, milk, butter and fish-liver oils and the provitamin beta-carotene of plants. All-trans

retinoic acid (ATRA) (figure 7 ) is the major signaling retinoid in the body, and mediates

its action through RAR–RXR heterodimers.52

44

OH

O

Figure 7. The structure of All-trans retinoic acid53

Natural retinoids, which are derived from the parent retinol, arise from four

isoprenoid units joined in a head-to-tail manner.54

They can be divided into three parts:

a trimethylated cyclohexene ring, a conjugated tetraene side chain, and a polar

functional head group (e.g. alcohol, aldehyde, acid).54

Due to the presence of the

conjugated system, retinoids are very easily oxidized and / or isomerized 54

. Thus

many synthetic retinoids have been developed.

1.1.1 Biological roles

Retinoids mediate many biological processes during embryonic development and

in adult life.52,53

They are essential for several biological processes, including growth

and development, reproduction, and cellular differentiation. Retinoids have these

biological processes in both normal and tumor cells, in vivo and in vitro. 53

Because of

their capability of controlling differentiation and apoptosis, they have pharmacological

potentials in the treatment and prevention of cancer.52

In fact, ATRA and some other

commercially available retinoids are generally applied in many cell differentiation

therapies.53

However, retinoids are toxic when taken in excess, irritating to the skin,

45

and are highly teratogenic.54

The biological roles of retinoids are achieved through their two groups of nuclear

receptor, RARs and RXRs, each of which has three isotypes α, β and γ. These

receptors possess different ligand specificity. 55

For example, ATRA can only bind and

trigger RAR receptors, whereas 9-cis RA can bind and activate both RARs and RXRs.

55 The class and isoform selectivity of retinoids is important in differentiation therapy.

Due to the ability of RXR to heterodimerize with a wide variety of nuclear receptors,

they have wide range of therapeutic uses, but also a corresponding concern for broad

toxicity. RAR agonists are thus expected to have more selective therapeutive activity

and the bulk of research has been in this area.

The degree of cell differentiation depends on the expression level of target genes

and the activity of target genes is determined, among many factors, by the

post-translational modification of the N-terminal tails of core histones by acetylation

and subsequent changes in chromatin structure.47

Upon binding to agonist or

antagonist, retinoid receptors act on the transcriptional complex by inducing chromatin

structural changes, resulting in activation or repression of target genes.

1.1.2 Mechanism of action

RARs and RXRs act mainly as RAR-RXR heterodimers.55

In the absence of RAR

ligands or in the presence of RAR antagonists, RAR-RXR heterodimers form

multi-protein complexes with nuclear receptor co-repressor (CoR), silencing mediator

46

for retinoid and thyroid receptors (SMRT) and histone deacetylases (HDACs), all of

which result in repression of gene transcription.52,55

In contrast, retinoid binding to the

heterodimers induces a conformational change in the ligand-binding domain (apo-LBD)

to generate the holo-LBD. This structural transition disrupts the intereaction with the

CoR and allows the recruitment of co-activators (CoAs) as well as RAR-RXR binding

to RARE’s (retinoic acid response elements). CoAs recruit (or pre-exist in a complex

with) histone acetyltransferases (HATs), which leads to the acetylation of histone

amino-terminal tails, resulting in chromatin decondensation. Then the basal

transcription machinery, containing thyroid-hormone-receptor-associated protein

(TRAP), vitamin D receptor-interacting protein (DRIP) or Srb and mediator

protein-containing complex (SMCC), is formed, initiating the target gene expression

(figure 8 ).52,55

47

Figure 8. Mechanisms of transcriptional repression and activation by RAR–RXR

heterodimers 52

1.2 Histone deacetylases (HDACs) and Histone deacetylases inhibitors (HDACis)

1.2.1 HDACs

As described above, HDACs are nuclear enzymes that play a critical role in

48

regulating gene expression. They catalyze the deacetylation of the N-acetyl lysine

residues of histones in chromatin thus affecting the accessibility of transcription

factors to DNA.56

The overall levels of acetylation are controlled by the balance

between the activities of histone acetyltransferases (HATs) and histone deacetylases

(HDACs).57

Imbalance of their activities has been implicated in cancer, and histone

deacetylase inhibitors (HDACis) display antiproliferation properties that have been

rendered them as potential clinical candidates.56

HDACs are separated into four main

classes based on their sequence homology and expression models. Class I and II and

IV HDACs are Zn-dependent deacetylases, whereas the Class III HDACs are

NAD-dependent deacetylases.57

1.2.2 HDACis

HDACis increase histone acetylation, which results in increased gene

expression.57-59

Overall, HDACis induce cellular arrest during the cell cycle, or induce

cells to undergo apoptosis or differentiation depending upon cell type.57

Because of

the diverse biological activities of HDACis, they have been used in the inhibition of

tumor growth. Numerous HDACis have been developed and are in various stages of

clinical development. HDACi structure generally consists of a zinc binding unit

attached via a linking chain to a “cap” group which binds at the HDAC surface. Many

zinc binding groups have been employed with the most common being hydroxamic

acid (e.g. SAHA, TSA, Figure 9) and carboxylic acids (e.g. valproic acid, butyric acid).

49

Notably, SAHA has been approved by FDA. In addition, HDACis can synergize with

other therapeutic approaches. They are able to increase the efficacy of other nuclear

receptor ligands, such as retinoids, in second cancer models.60,61

1.3 Problems of retinoid treatment in cancer

As described above, retinoids has been used in the treatment of several cancer,

including APL and neuroblastoma.62

However, a problem in this treatment is the rise of

retinoid resistance. In the treatment of epithelial tumors, retinoid therapy encounters

the loss of retinoid sensitivity associated with lack of RARβ2 expression due to

RARβ2 promotor hypermethylation and histone deacetylation.46,63

The resistance to

ATRA in APL has been overcome by co-treatment with the HDACi phenylbutyric

acid.64,65

In combination with retinoids, HDACi induce acetylation in RARβ2

hyper-methylated promoters leading to the re-expression of RARβ2, resulting in an

additive inhibitory effect on tumor cell growth in vitro and in vivo.66,62

Additive/synergistic growth inhibition of human prostate cancer cells has also been

reported from combination therapy.46

However, some similar patients did not respond

to this combination therapy.48

Improvement in the therapy is needed.

1.4 Retinoid-HDACi hybrid drugs

In drug discovery, the “one disease, one target” approach has dominated the

50

pharmaceutical industry.67

However, many diseases are still not well treated under this

paradigm. In order to enhance efficacy, polypharmacology, which develops drugs to

modulate multiple targets at the same time, is under consideration and development.67

The possible approaches include drug cocktails, muticomponent drugs and multiple

ligands.67

Firstly, the approach of drug cocktails can be defined by the concept of “2

tablets with 2 agents”, where different drugs for different targets are administered at

the same time. Secondly, the approach of muticomponent drugs follow a concept of “1

tablet with 2 agents”, where two or more agents are coformulated into a single tablet to

improve patient compliance.67

The combination therapies of retinoids and HDACis

that were described in the last section were administered as either drug cocktail or

muticomponent drugs. One disadvantage of having 2 drugs that rely heavily upon

each other for efficacy, which exists for both drug cocktail and multicomponent

strategies, is the unpredictable differences in the metabolism rates for each component

among patients.67

Finally, the last approach of multiple-ligand drugs follows a concept

of “1 tablet with 1 active agent that acts upon multiple biological targets”. The

difficulty of this method, however, is the design of the active agent such that it

possesses good affinity for multiple targets. This greatly increases the difficulty in the

design and optimization, but will eventually be advantageous in the later stages of the

drug discovery process due to the presence of only a single pharmacokinetic profile,

giving better drug delivery properties compared to two agents. In addition, a lower risk

of drug-drug interactions is also a benefit.67

51

In considering the disadvantages that retinoid/HDACi cocktail or multicomponent

drugs may possess, the aim of this project was to develop a hybrid drug which

combined an RAR agonist with an HDAC inhibitor. Hybrid molecules are defined as

chemical entities with different biological functions and dual activities, indicating that

a hybrid molecule often possesses two distinct pharmacophores.68

The synergistic

benefits between retinoids and HDACis have already been applied in drug discovery

research for cancer treatments. A novel prodrug of retinoic and butyric acids, RN1

(retinoyloxymethyl butyrate, Figure 9), was synthesized.48

First, in Acute

Promyelocytic Leukemia (APL) RA-sensitive NB4 cells, RN1 induced greater cell

differentiation than RA (retinoic acid) or NaB (sodium butyrate, Figure 9), and

inhibited cell growth to the same degree as RA or RA plus NaB. NaB alone had no

inhibition effect on cell growth.48

Secondly, in the RA-resistant APL NB4-MR4 cell

line, RN1 significantly inhibited cell growth while the treatment with RA or RA in

combination with NaB had no effect. RN1 partially induced differentiation and the

expression of RA target genes, and also caused apoptosis in RA-resistant R4 cells.48

Furthermore, RN1 arrested the growth and induced apoptosis in non-APL tumor cells.

In contrast, RN1 had no inhibition effect on growth in normal human peripheral blood

mononuclear cells.48

Through this research, RN1 may possess the potential to be used

in the treatment of tumors other than APL. Unfortunately, due to the instability of RN1,

its administration must quickly follow its synthesis. Also, the incorporated NaB moiety

in RN1 is one of the weakest HDACi known. Therefore, other HDACi’s, including the

52

FDA approved SAHA (Zolinza), could act as better candidates to combine with RA.

RN1 provided good underpinning for our development of a stable hybrid drug with the

hope of enhancing therapeutic efficacy in cancer treatment. There are several examples

of hybrid molecules. One example would be within our group where the design and the

synthesis of several hybrid drugs targeting nuclear receptors and HDAC have been

successfully. For instance, Triciferol, a hybrid molecule combining VDR (vitamin D3

receptor) agonist and HDAC inhibitory activities, was shown to be a more efficacious

antiproliferative and cytotoxic agent than natural vitamin D3 in four cancer cell models

in vitro.69

The experience on how to design hybrid molecules which combine activity

towards a nuclear receptor and HDAC, and the rational design principles should be

applicable to retinoic acid receptor agonist/HDACi hybrids. Notably, compared to

prodrugs such as RN1, hybrid molecules are expected to be more stable.

53

O

O

NH

OH

N

O O

Trichostain A(TSA)

HN

NH

OH

O

O

Suberoylanilide hydroxamic acid(SAHA)

O

O

RN1

ONa

O

Sodium butyrate(NaB)

OH

O

NH

O OH

O

TTNN AM580

Figure 9. Chemical Structures of TSA, SAHA, NaB, RN1, TTNN and AM580

1.5 Design of RAR agonist/HDACi hybrids70

In our group’s drug designs, 9 retinoid acid analogs (75-83) were planned, all

being hybrid molecules containing the core of retinoids merged with the Zn binding

functional group (figure 10). The design of these hybrids is based on structure-activity

relationship (SAR) and x-ray studies for ATRA/RAR and TSA/HDAC. The crystal

structures of ATRA and other agonist bound to RAR have revealed that there is a

large hydrophobic binding pocket consists mainly with hydrophobic residues (e.g. Phe,

Leu, Ile, Met) and a hydrophilic carboxylic acid binding region composed of 3 binding

54

residues (Ser129, Arg278, Lys236).71

The ligand binding interaction induces the

C-terminal H12 to seal its entry site. This can not only further stabilize the ligand, but

create a binding surface for transcriptional mediators. It also reveals that the -ionone

unit is closer to H11 and H12 leading to good van der waals interaction. Many

synthetic retinoids have been developed and most of them use a

1,1,4,4-tetramethyltetralin to replace the -ionone unit and tether this to a carboxylic

acid containing unit. Aromatic groups are used for the replacement of polyene chain in

the natural vitamin to mitigate its air-, light- and metabolic-instability. Therefore, the

acid region of ATRA was replaced by aromatic carboxylic acid in most cases.72

Addition, phenol-based retinoids have been reported (e.g. 4-HPR).72

The crystal

structure of TSA bound to archaebaterial HDAC1 homolog HDLP have revealed a

tube-like binding pocket possessing a zinc ion coordinated to residues of Asp168,

His170 and Asp 258 at the bottom of the tube.73

The hydroxamic acid forms a

bidentate chelate with the zinc ion. The diene chain is inserted into the narrow pocket,

making multiple contacts to the hydrophobic portion of the pocket. The dimethyl

-aniline group at the other end of TSA makes several hydrophobic contacts at the

surface groove at the outlet of the tube. The dienyl chain in TSA thus acts as linker,

tethering the zinc binding unit to a “cap” group which binds at the HDAC surface.74

Traditionally, long straight chains, either saturated or unsaturated, are mostly used as

linker. However, there are several recent examples of aromatic linkers. Besides the

hydroxamic acid are used commonly as zinc binding group (ZBG), other groups

55

including ortho-aminoanilides, thioglycolate amides, sulfonamides have been used.

Using simple rational design principles, it should be possible to design bifunctional

hybrid molecules that can act as both RAR agonists and HDACi's. First, we

incorporated the hydroxamic acid directly into the carboxylic acid site of known

retinoids (e.g. AM580, TTNN, figure 9) to add HDACi activity to these molecules. It

was expected that the hydroxamic acid would take part in hydrogen bonds, similar to

that of ATRA in LBD of RAR, while conveying the capacity to chelate the zinc ion in

the HDAC binding site. Based on this, hybide76, 78, 79 were designed. Secondly,

many retinoids utilize amides of p-aminobenzoic acid for the carboxylic acid region of

the molecule (e.g. AM580). Incorporation of second amino group in the aromatic ring

would transform this amide into an o-aminoanilides, a very common motif in HDACi's

which are entering clinical trials.74

Hybride 75 was designed based on this concept. In

addition, retinoids such as 4-HPR are known to have p-aminophenols and thus an

o-amino-p-phenoxyamide (e.g. 77) might also function as a retinoid/HDACi

bifunctional hybrid. Third, incorporation of the hydroxamic acid to known retinoid

backbones (e.g. 1,1,4,4-tetramethyltetralin) tethers with variable lengths to find a

best-fit with RAR carboxylic acid binding sites. With a modest tether length, these

structures are also expected to be excellent HDACi's, the 1,1,4,4-tetramethyltetralin

unit serving as the 'cap' group of the HDACi. Hybrid 80, 81, 82 were designed based

on this idea. Finally, another ZBG , thioglycolate amide, was used in hybid 83.

56

The goal of my research project was to synthesize the 9 retinoid acid analogs

described above, which would then be screened for biological activity by our

collaborators at the University of Montreal.

HN

O

NH

OH

O

NH

OH

O

NH

OH

O

NH

OH

O

OH

HN

O

SH

NH

NH2

O

NH

NH2

O

NH

O

7576

77 78

79 80

81 82

83

CO2HNHOH

O

OH

Figure 10. The structure of retinoic acid analogs (75-83)

2. Synthesis of retinoic acid analogs(75-83)

2.1 Synthesis of compound 75

57

The base of all our planned hybrids was a 1,1,4,4-tetramethyltetrahydro-

naphthalene which mirrors the ionone portion of retinoic acid. To prepare this unit,

2,5-dichloro-2,5-dimethylhexane 84 was prepared from the reaction of the

commercially available 2,5-dimethyl-2,5-hexanediol 85 with concentrated aqueous

HCl at room temperature. Friedel-Crafts alkylation of toluene with 84 in presence of

AlCl3 provided 1,1,4,4,6-pentamethyl-1,2,3,4-tetrahydronaphthalene 86 in 87% yield

over two steps. Oxidation of 86 by potassium permanganate gave 1,1,4,4,-

tetramethyl-6-carboxy-1,2,3,4-tetrahydronaphthalene 87 in 76% yield75

(Scheme 22).

OH

OH

Cl

ClMe

COOH

r.t

HCl

AlCl3

Toluene

KMnO4

Pyridine

8485 86

87

87% two steps

76%


To prepare our orthoamino anilides, methyl ester 88 was first prepared from

4-amino-3-nitrobenzoic 89 (Scheme 23). Aromatic acid 87 was activated with thionyl

chloride in CH2Cl2 to provide acid chloride 90, which was then directly coupled with

amine 88 to give nitro amide compound 91 in 52% yield over two steps.76

58

Hydrogenation of 91 under stand conditions (10% Pd-C and hydrazine hydrate in

EtOH) led to amine 92 in 81% yield, which was hydrolyzed to retinoic acid analog 75

in 73% yield (Scheme 24).

COOH

H2N

NO2

COOMe

H2N

NO2

MeOH, AcClreflux

96%

89 88


COOH

reflux

SO2Cl

CH2Cl2 Cl

O

NH

O OMe

O

NO2

COOMe

H2NNO2 88

DIPEADMAPovernight52% two steps

87 90

91

NH

O OMe

O

NH2

H2NNH2

HClPd/C

92 LiOH

THF/MeOH/H2O

73%

NH

O OH

O

NH2

75

81%


59

2.2. Synthesis of compound 76

To prepare our hybrid derived from AM 580, aromatic acid chloride 90 prepared above

was coupled with methyl para-amino benzoate 93 to provide amide 94 in 54% yield

over two steps. Hydroxyamination of ester 94 with 50% aqueous NH2OH in

THF/MeOH gave hydroxamic acid 76 in 51% yield77

(Scheme 25).

Cl

O

NH

O OMe

OCOOMe

H2N

DIPEADMAPovernight54% two steps90

94

90

NH

O NHOH

O

NH2OHTHF/MeOH

KOH

51%

76



Condensation of acid chloride 90 and 4-amino-3-nitrophenol 96 provided ester 97

rather than the desired amide 95 as shown in scheme 26. We considered the possibility

that the ester 97 was kinetic product formed due to the increased acidity of the phenol

due to the o-nitro group. However, the ester 97 did not convert to 95 in refluxing

60

toluene over 24 hours. To attempt solve this problem, 96 was protected with TBSCl

provided compound 98 (Scheme 27).

Cl

O

NH

OOH

90

95

NO2

O

ONH2

NO2

OH

H2NNO2

96

DIPEA, DMAP

97

Scheme 26. Condensation reaction of aromatic acid 87 and amine 96

OH

H2N

NO2

OTBS

H2N

NO2

TBSClTHFimidazoleDMAP

93%

9698

Scheme 27. Protection of 96 with TBSCl

It was expected that condensation of 98 with acid chloride 90 would then furnish

the desired amide. However, to our surprise, diacylated compound 100 was obtained

exclusively in this coupling event, presumably via in situ TBS deprotection.

Hydrolysis of compound 100 eventually led to 95, which was followed by

hydrogenation in the presence of catalytic amounts of 10% Pd-C to provide

compound 77(Scheme 28, route a). Alternatively, compound 77 can be directly

obtained in 54% yield by condensation of 87 with 3,4-diaminophenol 10178

prepared

61

by hydrogenation of 4-amino-3-nitrophenol 96 (Scheme28, b and c). This useful

regioseletivity results from the presence of the hydroxyl group which serves to

increase electron density at the para-amino group.

Cl

O

NH

OOTBS

90

99

NO2

NH

OO

NO2

OTBS

H2NNO2

96

DIPEA, DMAP

100

a)

O

NaOH

H2O/MeOH/THF

NH

OOH

95

NO2

H2

Pd/CMeOH

NH

OOH

77

NH2

b)

Cl

O

90

OH

H2NNH2

101

HOBt, HBTUDMF54%

NH

OOH

77

NH2

OH

H2N

NO2

OH

H2N

NH2

H2

Pd/CMeOH

92%

96 101

c)

Scheme 29. Synthesis of 77 in route a and c

62


To prepare the next series of hybrids, we required a bromotetrahydronaphthalene

which can be used for cross-coupling reactions. A double Friedel-Crafts alkylation of

bromobenzene 102 with 2,5- Dichloro- 2,5-dimethylhexane 84 produced

1,2,3,4-tetrahydro-1,1,4,4-tetramethyl-6-bromo-naphthalene 103 in 96% yield.

(Scheme 29) 79

To prepare a hybrid of TTNN, a biaryl coupling was successfully

achieved using Negishi cross-coupling80

of the arylzinc reagent, prepared by treatment

of bromotetrahydronaphthalene 103 with nBuLi followed by metal exchange with

ZnCl2, and bromonaphthalene 104 in the presence of Ni(PPh3)4 catalyst to provide

biaryl 105 in 39% yield. Hydroxyamination of ester 105 by 50% aqueous NH2OH in

THF/MeOH afforded hydroxamic acid 78 in 47% yield (Scheme 30).

Cl

Cl

Br

102

AlCl3CH2CCl296%

Br

10384


63

Br

103

+

Br

OMe

O

104

nBuLi, THF,-750C;

ZnCl2, THF;

Ni(PPh3)4

39%

103

OMe

O

NH2

THF/MeOHKOH

47%

78

NHOH

O



In order to prepare another biaryl, 3-(4’-bromophenyl)-(E)-propenoic acid

methylester 108 was prepared in 73% yield from a Wittig reaction between

4-bromobenzaldehyde 106 and Ylide 107 in water at 90 0C. (Scheme 31)

81 However,

Negishi cross-coupling between the arylzinc reagent, prepared by treatment of

bromotetrahydronaphthalene 103 with nBuLi followed by metal exchange with ZnCl2,

and 108 in the presence of Ni(PPh3)4 or Pd(PPh3)4 catalyst was unsuccessful (Scheme

32). Therefore, an alternative route was adopted for preparation of biaryl 109.

Bromotetrahydro- naphthalene 103 was treated with nBuLi, followed by addition of

triisopropylborate and then hydrolysis to arylboronic acid 110.82

Subsequent Suzuki

cross-coupling83

of arylboronic acid 110 with 108 in the presence of Pd(OAc)2/PPh3 as

64

catalyst afforded 109 in 42% yield. Hydroxyamination of ester 109 with 50% aqueous

NH2OH gave hydroxamic acid 79 in 61% yield (Scheme 33).

Br

H

O

+ Ph3POMe

OOMe

Br

OH2O

90 0C

73%

106 107 108


Br

103

1) nBuLi, THF, -75 0C

2) ZnCl2, THF

OMeBr

O3)

108

Ni(PPh3)4

or Pd(PPh3)4

OMe

O

109

Scheme 32. Negishi cross-coupling reaction between 103 and 108 proves to be

problematic

65

Br

103

OMe

O

109

nBuLi, THF;

B(iOPr)3B(OH)2

110

OMeBr

O

108

CsF, THF

Pd(OAc)2 +PPh3

42%

NHOH

O

79

NH2OH

THF/MeOHKOH

61%


2.6. Synthesis of compound 80, 81 and 82

We attempted to prepare a series of hybrids which lacked a second aromatic ring.

These molecules more closely resemble SAHA and other HDACis and we were

interested as to whether they would function as bifunctional hybrids. To prepare the

first of these, methyl 5-bromopentanoate 112 was obtained from 5-bromovaleric acid

111 in 90% yield. (Scheme 34) Alkylzinc reagent 113 was obtained by treatment of 112

with commercially available Zn powder (activated by the addition of

1,2-dibromoethane (5 mol%), TMSCl (1 mol%) and LiCl) in THF. Subsequent

coupling with aryl bromide 103 in the presence of Pd(PPh3)4 as catalyst provided ester

114 in a modest 15% yield. Hydroxyamination of ester 114 by 50% aqueous NH2OH

gave hydroxamic acid 80 in 45% yield (Scheme 35). 84

66

Br OH

O

Br OMe

OAcClMeOH

90%

111112


Br OMe

O

BrZn OMe

O

1mol% TMSCl

5mol% 1,2-dibromoethane

10mol% I2Zn,Li,THF, 50 0C

112113

Br

103

THF

Pd(PPh3)415% two steps

114

OMe

O

NHOH

ONH2OH

THF/MeOHKOH

45%

80


Synthesis of compound 81 was carried out in similar fashion. Ester 116 was

prepared from 6-bromohexanoic acid 115 in 89% yield. Alkylzinc reagent 117 was

obtained by treatment of 116 with commercially available Zn powder (activated by the

addition of 1,2-dibromoethane(5 mol%), TMSCl(1 mol%) and LiCl) in THF.

Subsequent coupling with aryl bromide 103 in the presence of Pd(PPh3)4 as catalyst

provided ester 119 in 7.9% yield. Hydroxyamination of ester 119 by 50% aqueous

67

NH2OH gave hydroxamic acid 81 in 52% yield (Scheme 36).84

1mol% TMSCl



Br

103

THF

Pd(PPh3)47.9% two steps

NH2OH

THF/MeOHKOH

HOBr

O

MeOBr

OAcClMeOH

89%115 116

MeOZnBr

O

117

118

OMe

O

81

NHOH

O

52%


Also, synthesis of compound 82 was carried out in similar fashion.

7-Bromoheptanol 119 was treated with DMSO/(COCl)2/Et3N in dichloromethane to

afford aldehyde 120 in 95% yield.85

Oxidation of aldehyde 120 to carboxylic acid 121

with NaClO2/NaH2PO4/H2O followed by treatment with acetyl chloride in methanol

provided ester 122 in 60% yield over two steps. Alkylzinc reagent 123 was obtained by

treatment of 122 with commercially available Zn powder (activated by the addition of

1,2-dibromoethane(5 mol%), TMSCl(1 mol%) and LiCl) in THF. Subsequent coupling

68

with aryl bromide 103 in the presence of Pd(PPh3)4 as catalyst provided ester 124 in

11% yield. Hydroxyamination of ester 124 by 50% aqueous NH2OH gave hydrxamic

acid 82 in 64% yield (Scheme 37).84

Br OH Br H

O

Oxalyl chloride

DMSO,Et3NCH2Cl2

95%119 120

Br OH

O

121

AcClMeOH

1mol% TMSCl



60% two steps

NaClO2

NaH2PO4

H2O

Br OMe

O

122

BrZn OMe

O

123

OMe

OBr

103

THF

Pd(PPh3)411% two steps

124

NHOH

O

82

NH2OH

THF/MeOHKOH

64%



Finally, recent results from our lab indicate that thioglycolate amides are good

69

HDACis and we thus sought to introduce this zinc binding group in our retinoid

hybrids. Hydrolysis of ester 114 led to carboxylic acid 125, which could be subjected

to a Curtius rearrangement with DPPA(diphenylphosphoryl azide). The intermediate

isocyanate 126 was hydrolyzed with aqueous NaOH to afford amine 127 in 42% yield

over two steps. Coupling of protected thioglycolic acid 128 with amine 127 produced

the amide 129 in 99% yield. Deprotection of 129 led to the desired thiol 130 in 74%

yield (Scheme 38). 77

114

OMe

O

125

OH

ONaOH

THF/MeOHH2O

99%

DPPA

Et3toluene

126

N=C=ONaOHTHF

42% two steps

NH2

127

HOSAc

O

128

EDC HCl99%

HN

129

SAc

O

HN

SH

O

MeONaMeOH

74%83


3. Assay of biological activities70

70

The biological activities of hybrids (75, 76, 77 and 78) were determined through

assays performed by David Cotnoir-White (University of Montreal). All four hybrids

have strong RAR agonist activity while maintaining modest to strong HDACi activity.

Hybrid 76 had the highest overall potency while both hybrids 76 and 78 showed

anti-proliferative properties against several cell lines. Impressively, TTNN-based

hybrid 78 displayed highly promising anti-proliferative activity. The details are

described below.

1) Hybrid molecules showed similar apparent affinity for RARα as parental

compounds. A bioluminescence energy transfer (BRET) assay designed for co-activator

recruitment of RARα and characterized hybrids was employed, which monitors the

formation of the receptor-coactivator complex. Results show that all four hybrids were

as active as ATRA or 9-cis-RA at 1 µM. Notably, the RAR agonist activity of hybrid

78 was not interrupted by the incorporation of hydroxamic acids into retinoids.

2) Hybrids (76, 77, 78) were found to transcriptionally activate RA target genes to

varying degrees. The induction of several RAR target genes by these hybrids was

observed in RA responsive NB4 and MCF-7 cell lines as well as the retinoid resistant

MDA-MB-231 cell line. In NB4, hybrids 76, 77 strongly induced RARα, while hybrid

78 only had a very weak effect. However, C/EBP-epsilon was induced by all three

hybrids and this induction was significantly suppressed by the addition of an RAR

antagonist. On the other hand, hybrid 78 induced RAR in MCF-7 and MDA-MB-231

cells, but no induction was observed in the presence of ATRA or parent retinoid

71

TTNN.

3) HDACi activity was monitored by a fluorometric assay using an acetylated

lysine substrate which, upon treatment with purified HDACs followed by trypsin,

releases aminomethylcoumarin. Hybrids 76, 75, 77 and 78 had IC50's of 2.5 µM, 227

µM, 576 µM, and 5.0 µM respectively against HDAC3. HDAC6 activity of 78 was

assessed and found to have an IC50 of 148 nM. This range of potencies is similar to

those observed in related VDR agonist-HDACi hybrids (unpublished data). More

importantly, in breast cancer cell lines MCF7 and MDA-MB-231, prolonged treatment

with hybrid 78 caused p53 acetylation to levels similar to SAHA, an effect that is not

observed with its parental compound TTNN. This observation opens the door to

understanding a possible mechanism of action for the anti-proliferative property of

hybrid 78 in some breast cancer cell lines.

4) Tests were also performed to observe the effects of hybrids (76, 77, 78) on

proliferation, apoptosis and/or differentiation in leukemic and breast cancer cells. Cells

were treated with parental retinoids and the HDACi SAHA, alone and in combination,

as well as the hybrids at same concentrations. Cell growth was evaluated over a 3-7

day period using cell viability assays. Apoptosis was monitored by propidium iodide

staining and flow cytometry analysis. Hybrids 76 and 77 showed strong growth

inhibitory effects in RA-sensitive and RA-resistant acute myelogenous leukemia

(AML) cells, and they also induced granulocytic differentiation. These results are

consistent with the RARα BRET assay. Most importantly, hybrid 78, a RARβ/γ

72

selective retinoid TTNN hybrid, showed strong anti-proliferative activity in a

RA-resistant ALL cell line, REH, as evidenced by its potent induction of cell death. It

is also active in several breast cancer cell lines. Remarkably, Hybrid 78 had a strong

inhibition effect on the growth of MDA-MB-231 cells (a RA-resistant breast cancer

cell line), in which SAHA, a potent HDACi, only partially inhibited cell growth.

Furthermore, hybrid 78 exhibited only negligible effects on immortalized 184b5 cells,

indicating a potentially useful therapeutic window.

4. Conclusions

The synthesis of several retinoic acid analogs (75-83) has been described. Retinoic

acid analogs (75-77) were synthesized using condensation reaction sequence involving

tetrahydrotetramethylnaphthalene carboxylic acid and possible Zn binding functional

groups. Retinoic acid analogs (78-79) were prepared via Suzuki or Negishi

cross-coupling reaction between aromatic bromides and corresponding aromatic

boronic acid or zinc reagent. Retinoic acid analogs (80-82) were prepared by Pd(0)

catalyzed cross coupling reaction of aromatic bromide with non-activated alkyl halides.

Retinoic acid analogs (83) were synthesized using general method for formation of

amide bond. Alternative routes were required for preparation of compounds (80-82)

due to the low yield. From the biological assays completed to date, compound 78 has

enhanced anti-proliferative activity and potentially low toxicity which make it an

exciting lead as a novel anticancer drug.

73

Chapter Three

Experimental Section

General: All reactions were conducted in oven or flame-dried glassware under an

argon atmosphere with magnetic stirring unless noted otherwise. 1H and

13C spectra

were recorded on a 300MHz or 400MHz Varian Mercury, or 500MHz Varian Unity

spectrometer and chemical shift values are expressed in ppm (δ) relative to chloroform

(7.26 ppm, 77.0 ppm respectively). High-resolution mass spetra were obtained from

the Department of Chemistry or the Mass Spectrometry Unit at McGill University.

Infrared spectra were obtained using a Nicolet Avatar 360 FTIR spectrometer on

evaporated samples. Thin layer chromatography (TLC) was carried out on EMD glass

plates pre-coated with Silica gel 60 F-254. All plate were visualized by UV254 light

source or by staining with an aqueous solution of potassium permanganate. Flash

column chromatography was performed using Silica Gel F60 (Silicycle). Ether and

THF were distilled from sodium and benzophenone. Methylene chloride, toluene and

triethylamine were distilled from calcium hydride. Commercial reagents were used

without further purification unless otherwise noted.

74

Synthesis of 2,2-bis(chloromethyl)-5,5-dimethyl-1,3-dioxane (50):

O O

ClCl

A mixture of 1,3-neopentyl glycol (13.8 g, 0.132 mol, 1.1 equiv),

1,3-dichloroacetone (15.2 g, 0.12 mol, 1 equiv), p-toluenesulfonic acid (0.455 g, 2.4

mmol, 2 mol%) and toluene (10 mL) was heated to reflux for 19 hr in a

round-bottomed flask equipped with a Dean-Stark trap and a condenser. The reaction

was partitioned between hexane (50mL) and saturated sodium bicarbonate (20mL).

The organic phase was washed with brine and water, dried over MgSO4, filtered and

concentrated on a rotary evaporator. Purification by vacuum distillation (111-113 0C,

2.5 mmHg) afforded 2,2-bis(chloromethyl)- 5,5-dimethyl-1,3-dioxane(50)37

(22.0 g,

86%). Rf = 0.7 (40% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3 ) δ 3.76 (s, 4H),

3.54 (s, 4H), 0.97 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 97.4, 71.2, 42.1, 30.0, 22.6.

Synthesis of 6,6-dimethyl-4,8-dioxaspiro[2.5]oct-1-ene (37):

O O

A three-necked, round-bottomed flask was equipped with dry ice/acetone

condenser and placed in a dry ice/acetone bath. Gaseous ammonia was introduced to

the flask until 60mL of NH3 had been condensed and gentle stirring was started. The

NH3 inlet was replaced with a glass stopper the dry ice/acetone bath was replaced with

75

a -35 0C bath (dry ice/trichloroethylene). A crystal of hydrated ferric nitrate (0.045 g,

0.74 mmol, 0.25 mol%) was added. A small piece (about 1 mm) of sodium was added

to the resulting orange solution. The solution was stirred until the blue color

disappeared and pieces of sodium (3.2 g, 0.139 mol, 0.31 equiv) were added over 30

minutes. After 20 minutes, the cooling bath was replaced with a dry ice/acetone bath.

A solution of 2,2-bis(chloromethyl)- 5,5-dimethyl-1,3-dioxane (50) (9.545 g,

0.0448mol, 1 equiv) in dry ether (23 mL) was added dropwise to the slurry of sodium

amide in liquid ammonia over 1 hr. The cooling bath was removed, and the mixture

was stirred for 3 hr, then was cooled again with a dry ice/acetone bath. After 10 min,

solid ammonium chloride (9.59 g, 0.179 mol, 4 equiv) was added in several portions

over 30 min. The dry ice condenser removed and the ammonia was allowed to

evaporate. The cooling bath was replaced with a water bath (room temperature), and a

mixture of dry ether and dry pentane (40 mL) was added over 20 min with vigorous

stirring. After evaporation of most of the ammonia (2 hr), the solution was filtered by

suction through a pad of celite 521. The filter cake was washed with ether (3 X 10 mL).

The combined filtrate was washed with brine and water, dried over MgSO4, filtered

and concentrated on a rotary evaporator. Purification by vacuum distillation (60-61 0C,

6-8 mmHg) afforded 6,6-dimethyl-4,8-dioxaspiro[2.5]oct-1- ene (37) (2.46 g, 40%).37

Rf = 0.3 (10% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3) δ 7.85 (s, 2H), 3.61 (s,

2H), 1.04 (s,6H); 13

C NMR (75 MHz, CDCl3) δ 125.7, 81.2, 76.7, 30.5, 22.4.

Synthesis of tert-butyl(3-iodobut-3-enyloxy)dimethylsilane (52):

76

TBSO I

To a slurry mixture of NaI (6.0 g, 40mmol, 1 equiv) in MeCN (30 mL) at room

temperature was added TMSCl (5.08 ml, 40 mmol, 1 equiv) followed by H2O (0.36 ml,

20 mmol, 0.5 equiv). After 10 min, a solution of 3-butyn-1-ol (48) (1.4 g, 20 mmol, 0.5

equiv) in MeCN (5.0mL) was added to the mixture and the resulting mixture was

allowed to react for 1 hr at room temperature. The reaction was quenched with water

(60 mL) and the mixture was extracted with ether (3x50 mL). Drying over MgSO4,

filtration and concentration on a rotary evaporator gave the crude iodo alcohol (3.82

g).

The crude iodo alcohol was dissolved in dichloromethane (100 mL) and cooled to

0 0C. To the stirred solution was added TBSCl (2.59 g, 21.2 mmol, 1.1 equiv),

imidazole (1.44 g, 21.2 mmol, 1.1 equiv), and DMAP (5 mg). The resulting mixture

was stirred at room temperature overnight. The reaction was quenched with water (60

mL) and the mixture was extracted with ether (3 X 50 mL). The combined extracts

were washed with brine and water, dried over MgSO4, filtered and concentrated on a

rotary evaporator. Purification by column chromatography using EtOAc/Hexane (1%)

as eluent afforded tert-butyl (3-iodobut-3-enyloxy)-dimethylsilane (52) (3.64g, 63%

over two steps). Rf = 0.4 (2% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3 ) δ 6.08 (s,

1H), 5.76 (s, 1H), 3.72 (d, J=6Hz, 2H), 2.59 (d, J=6Hz), 0.89 (s, 9H), 0.07 (s, 6H); 13

C

NMR (75 MHz, CDCl3) δ 127.6, 107.8, 61.9, 48.6, 26.1, 18.5, -5.0.

77

Addition Reaction in desired system to prepare tert-butyl(3-(6,6-dimethyl-

4,8-dioxaspiro[2.5]octan-1-yl)but-3-enyloxy)dimethylsilane (56):

O O

TBSO

To a solution of vinyl iodide (52) (385.2 mg, 1.234 mmol, 1 equiv) in 12 mL of

ether at -78 0C was added dropwise a 2.25 M solution of t-BuLi in hexane (1.13 mL,

2.63 mmol, 2.05 equiv). After stirring at -78 0C for an addition 10 min, the cooling

bath was removed and the mixture was allowed to warm and was stirred at room

temperature for 1 hr. The mixture was recooled to -78 0C and added via a cannula to a

suspension of CuBr/DMS (126.8 mg, 0.617 mmol, 0.5 equiv) in ether (5 mL) at -78 0C.

After stirring at -78 0C for another 15 min, then the cooling bath was removed. The

mixture was stirred at room temperature for 15 min and recooled to-78 0C. A solution

of 6,6-dimethyl-4,8-dioxaspiro[2.5]oct-1- ene (37) (86.4 mg, 0.617 mmol, 0.5 equiv)

in ether (1.6 mL) was added. The reaction mixture was stirred at -780C for 15 min. The

cooling bath was removed and the reaction mixture was quenched with aqueous NH4Cl

(25 mL) and the mixture was extracted with ether (3 X 30 mL). The combined extracts

were washed with brine and water, dried over MgSO4, filtered and concentrated on a

rotary evaporator. Purification by column chromatography using EtOAc/Hexane (2%)

as eluent afforded compound 56 (155.4 mg, 77%). Rf = 0.3 (5% EtOAc/Hexane); 1H

NMR (400 MHz, CDCl3 ) δ 4.85 (s, 1H), 4.76 (s,1H), 3.83-3.72 (m, 2H), 3.57-3.40 (m,

78

4H), 2.39 (t, J=6.8Hz, 2H), 1.79-1.75 (m, 1H), 1.21-1.06 (m, 2H), 1.03 (s, 3H), 0.95 (s,

3H), 0.89 (s, 9H), 0.06 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 141.2, 111.1, 91.0, 76.5,

76.3, 62.7, 40.8, 30.8, 30.6, 26.1, 22.6, 22.5, 18.5, 17.7, -5.0.

Synthesis of 2,2,3,3,10,10,11,11-octamethyl-4,9-dioxa-3,10-disiladodec-6-yne (61):

TBSO OTBS

A solution of butyne-1,4-diol (2.55 g, 29.6 mmol, 1 equiv), imidazole (4.75 g,

69.75 mmol, 2.4 equiv), DMAP (355 mg, 2.96 mmol, 0.1 equiv) in CH2Cl2 (200 mL)

was stirred for 5 min. TBSCl (10.5 g. 69.75 mmol, 2.4 equiv) was added to the mixture

and stirred for 1.5hr at room temperature. The reaction was quenched with 10%

aqueous potassium carbonate (100 mL) and the mixture was extracted with ether (3 X

100 mL). The combined extracts were washed with brine and water, dried over MgSO4,

filtered and concentrated on a rotary evaporator. Purification by column

chromatography using EtOAc/Hexane (2%) as eluent afforded alkyne (61) (8.84 g,

96%).41

Rf = 0.4 (5% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3) δ 4.34 (s, 4H),

0.90 (s, 18H), 0.11 (s, 12H); 13

C NMR (75 MHz, CDCl3) δ 83.5, 52.0, 26.0, 18.5, -4.9.

Synthesis of (E)-2,2,3,3,10,10,11,11-octamethyl-6-(tributylstannyl)-4,9-dioxa-3,10-

disiladodec-6-ene (62):

OTBSTBSO

SnBu3

79

To a solution of alkyne (61) (1.93 g, 6.13 mmol, 1 equiv) in THF (15 mL)

containing PdCl2(PPh3)2 (86.1 mg, 0.123 mmol, 2 mol%), Bu3SnH (1.95 ml, 7.36

mmol, 1.2 equiv.) was added dropwise at room temperature. After 20 min, the THF

was evaporated in vacuo. The oily residue was purified by column chromatography

using EtOAc/Hexane (1%) as eluent afforded vinylstannane (62) (2.96 g, 79%).41

Rf =

0.4 (2% EtOAc/Hexane); 1

H NMR (400 MHz, CDCl3 ) δ 5.68-5.50 (m, 1H), 4.37-4.16

(m, 4H), 1.51-1.25 (m, 18), 0.92-0.85 (m, 27H), 0.07 (s, 6H), 0.06 (s, 6H); 13

C NMR

(75 MHz, CDCl3) δ 148.0, 137.3, 64.8, 61.1, 29.4, 27.6, 26.3, 26.1, 18.7, 18.5, 13.9,

10.4, -4.8, -5.1.

Synthesis of (E)-6-iodo-2,2,3,3,10,10,11,11-octamethyl-4,9-dioxa-3,10-disiladodec-

6-ene (59):

OTBSTBSO

I

To a solution of vinylatannane (62) (2.95 g, 4.89 mmol, 1 equiv) in ether (23 mL),

a solution of iodine (1.24 g, 4.89 mmol, 1 equiv) in ether (16 mL) was added dropwisw

at room temperature. After 5.5 hr, the reaction mixture was evaporated in vacuo.

Purification by column chromatography using EtOAc/Hexane (2%) as eluent afforded

vinyliodide (59) (1.77 g, 82%).41

Rf= 0.4 (5% EtOAc/Hexane); 1H NMR (400 MHz,

CDCl3 ) δ 6.37 (s, 1H), 4.25 (s, 2H), 4.24 (s, 2H), 0.92 (s, 9H), 0.89 (s, 9H), 0.11 (s,

6H), 0.08 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 141.8, 103.9, 66.5, 61.6, 26.11, 26.0,

80

18.5, 18.5, -4.8, -5.0.

Cross coupling in model system to prepare (Z)-6-(2-butyl-6,6-dimethyl-4,8-

dioxaspiro[2.5]octan-1-yl)- 2,2,3,3,10,10,11,11-octamethyl-4,9-dioxa-3,10-

disiladodec-6-ene (64):

O O

Bu

OTBS

OTBS

To a suspension of CuBr/DMS (60.1 mg, 0.292 mmol, 1 equiv) in ether (1 mL), a

2.63 M solution of nBuLi (0.23 mL, 0.585 mmol, 2 equiv.) was added dropwise at -78

0C. After 15 min, the cooling bath was removed and stirred at r.t. for 10 min. Then the

reaction mixture was recooled to -78 0C. To this mixture, a solution of cyclopropenoen

acetal (37) (42.1 mg, 0.292 mmol, 1 equiv) in ether (0.3mL) was added at -78 0C. After

30 min, a solution of vinyliodide (59) (389 mg, 0.877 mmol, 3 equiv) and Pd(PPh3)4

(24 mg, 7 mol%) in THF (4 mL) was added at -780C. The cooling bath was removed

and let it warmed to r.t.. After this mixture was stirred for 7 hr, quenched with 33%

(NH4)2SO4 (7 mL) and the mixture was extracted with ether (3 X 10 mL). The

combined extracts were washed with water and brine, dried over MgSO4, filtered and

concentrated on a rotary evaporator. Purification by column chromatography using

Ether/Petroleum Ether (1%) as eluent afforded compound 64 (104 mg, 67%). Rf = 0.7

81

(5% Ether/Petroleum Ether); 1H NMR (400 MHz, CDCl3 ) δ 5.57 (t, J=6Hz, 1H),

4.27-4.05 (m, 4H), 3.55-3.44 (m, 4H), 1.79 (d, J=10.8Hz, 1H), 1.43-1.27 (m, 7H), 1.08

(s, 3H), 0.92-0.85 (m, 24H), 0.06 (s, 6H), 0.06 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ

133.9, 127.4, 76.2, 75.5, 31.8, 30.9, 30.5, 30.2, 28.9, 26.1, 22.8, 22.7, 22.3, 21.3, 18.5,

14.2, -4.8, -5.0, -5.1.

Synthesis of 1,1,4,4,6-pentamethyl-1,2,3,4-tetrahydronaphthalene (86):

Me

2,5-Dimeththyl-2,5-hexanediol (1.02 g, 6.93 mmol, 1 equiv) was combined with

reagent grade concentrated HCl (16 mL, 180 mmol, 26 equiv) and stirred at r.t. for 3 hr.

The reaction was quenched with water (2 0mL) and the mixture was extracted with

CH2Cl2 (3 X 20 mL). The combined extracts were washed with water and brine, dried

over MgSO4, filtered. Concentration on a rotary evaporator afforded crude

2,5-dichlorol-2,5-hexanediol (84). To a solution of 2,5-dichlorol-2,5-hexanediol (1.28

g, 6.93 mmol, 1 equiv) in toluene (1.2 mL, 10.4 mmol, 1.5equiv) and CH2Cl2 (14 mL),

aluminum chloride (46.4 mg, 0.35 mmol, 5 mol%) was added at 5 0C. The mixture was

warmed to r.t. and stirred for 30 min. The reaction was quenched with water (10 mL)

and the mixture was extracted with hexane (3 X 10 mL). The combined extracts were

washed with water and brine, dried over MgSO4, filtered and concentrated on a rotary

82

evaporator. Purification by column chromatography using EtOAc/Hexane (1%) as

eluent afforded 1,1,4,4,6-pentamethyl-1,2,3,4-tetrahydronaphthalene (86) (1.24 g, 87%

over two steps).75

Rf = 0.6 (2% EtOAc/Hexane); 1H NMR (300 MHz, CDCl3 ) δ 7.21

(d, J=7.6Hz, 1H), 7.12 (s, 1H), 6.96 (dd, J=8, 1.2Hz, 1H), 2.31 (s, 3H), 1.68 (s, 4H),

1.28 (s, 6H), 1.27 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 144.8, 142.0, 134.9,

127.2,126.7, 126.2, 35.4, 35.3, 34.3, 34.1, 32.1, 32.0.

Synthesis of 5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid

(87):

COOH

A round-bottomed flask equipped with a stirrer and reflux condenser was charged

with 1,1,4,4,6- pentamethyl-1,2,3,4-tetrahydronaphthalene (86) (1.24 g, 6.1 mmol, 1

equiv), sodium hydroxide (0.36 g, 9.16 mmol, 1.5 equiv), pyridine (4.2 mL) and water

(2.1 mL). The flask was heated in oil bath and maintained at 95 0C. Potassium

permanganate (2.41 g, 15.26 mmol, 2.5 equiv) was added in portions. The reaction

mixture was heated and stirred for addition 2 hr. Then ethanol (0.4 mL) was added.

After being cooled, the reaction mixture was suction filtered and the collected

manganese dioxide was washed with 2 N solution of NaOH (10 mL). The combined

filtrate was concentrated and acidified with 10% sulfuric acid. The flocculent

precipitate was collected by suction filtration, and redissolved in ether. Dried over

83

MgSO4 and filtered. Concentrated on a rotary evaporator afforded compound (87)

(1.07 g, 76%).75

1H NMR (200 MHz, CDCl3 ) δ 8.06 (d, J=1.8, 1H), 7.84 (dd, J=8.4,

1.8Hz, 1H), 7.39 (d, J=8.4Hz, 1H), 1.70 (s, 4H), 1.31 (s, 6H), 1.30 (s, 6H); 13

C NMR

(75 MHz, CDCl3) δ 172.1, 151.6, 145.5, 129.1, 127.3, 127.1, 126.6, 35.0, 34.9, 34.6,

31.9, 31.8.

Synthesis of methyl 3-nitro-4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-

2-carboxamido)benzoate (91):

NH

O OMe

O

NO2

A mixture of 5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid

(87) (39 mg, 0.168 mmol, 1 equiv), thionyl chloride (0.34 mL) and dichloromethane (1

mL) was heated at reflux for 4 hr. After removal of the solvent, a mixture of methyl

4-amino-3- nitrobenzoate (33 mg, 0.168 mmol, 1 equiv), dichloromethane (1 mL),

DIPEA (0.07 mL, 0.42 mmol, 2.5 equiv) and DMAP (2.1 mg, 0.017 mmol, 10 mol%)

was added to the residue and stirred overnight at r.t. The reaction was quenched with

water (5 mL) and the mixture was extracted with dichloromethane (3 X 5 mL). The



EtOAc/Hexane (3%) as eluent afforded compound (91) (35.9mg, 52% over two

84

steps).76

Rf = 0.6 (20% EtOAc/Hexane); 1H NMR (300 MHz, CDCl3 ) δ 11.56 (s, 1H),

9.15 (d, J=8.7Hz, 1H), 8.96 (d, J=2.1Hz, 1H), 8.32 (dd, J=9, 2.1Hz, 1H), 7.97 (d,

J=2.1Hz, 1H), 7.72 (dd, J=8.4,2.1Hz, 1H), 7.47 (d, J=8.4Hz, 1H), 3.96 (s, 3H), 1.73 (s,

4H), 1.36 (s, 6H), 1.32 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 166.3, 164.9, 151.0,

146.3, 139.3, 136.9, 135.8, 131.0, 127.9, 127.7, 126.4, 124.9, 124.5, 121.7, 52.8, 35.01,

34.9, 34.7, 32.0, 31.8, 29.9.

Synthesis of methyl 3-amino-4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene

-2-carboxamido)benzoate (92):

NH

O OMe

O

NH2

To a suspension of 10% Pd-C (23 mg), 5% HCl (0.02 mL) and methyl 3-nitro-4-

(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene- 2-carboxamido)benzoate (91)

(30.3 mg, 0.074 mmol, 1 equiv) in ethanol (0.14 mL), hydrazine hydrate (0.02 mL,

0.303 mmol, 4.1 equiv) was added, and the resulting mixture was stirred overnight at

r.t. Then the reaction mixture was diluted with ethanol (2 mL) and ethyl acetate (2 mL).

The Pd-C was removed by filtration through Celite 521. The filtrate was washed with

water and brine, dried over MgSO4, filtered and concentrated on a rotary evaporator.


compound (92) (22.8 mg, 81%). Rf = 0.2 (20%EtOAc/Hexane); 1H NMR (300 MHz,

85

CDCl3 ) δ 8.21 (s, 1H), 7.89 (d, J=2.1Hz, 1H) 7.59 (dd, J=8.4,2.1Hz, 1H) 7.49 (s, 3H),

7.37 (d, J=8.4Hz, 1H), 3.87 (s, 3H), 1.70 (s, 4H), 1.30 (s, 6H), 1.29(s, 6H); 13

C NMR

(75 MHz, CDCl3) δ 167.0, 166.3, 149.9, 146.0, 139.5, 131.2, 130.1, 128.0, 127.3,

126.4, 124.2, 124.1, 121.7, 120.0, 52.3, 35.0, 34.9, 34.8, 34.7, 32.0, 31.9.

Synthesis of 3-amino-4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-

2-carboxamido)benzoic acid (75):

NH

O OH

O

NH2

To a solution of methyl 3-amino-4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-

naphthalene-2-carboxamido)benzoate (92) (57.9 mg, 0.152 mmol, 1 equiv) in

THF/H2O/MeOH (0.9 ml:0.3 ml:0.3 ml), a solution of 1N lithium hydroxide

monohydrate (0.31 ml, 0.304 mmol, 2 equiv) was added, and the resulting mixture was

stirred at r.t. for 12 hr. After most of the THF and MeOH was evaporated, the aqueous

phase was acidified with 1N HCl to PH 5.5 and extracted with ethyl acetate to afford

the compound (75) (40.7 mg, 73%).1H NMR (300 MHz, CDCl3 ) δ 8.44 (s, 1H), 7.91

(d, J=1.2Hz), 7.62 (d, J=8.4, 1H) 7.50-7.48 (m, 3H), 7.34 (d, J=8.1Hz, 1H), 1.68 (s,

4H), 1.28 (s, 6H), 1.27 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 171.4, 166.7, 149.9,

145.9, 139.3, 131.1, 130.7, 127.4, 127.2, 126.5, 124.4, 122.6, 120.6, 35.0, 34.9, 34.8,

86

34.6, 31.9, 31.9; HRMS (ESI): m/z calcd. for [( M+H)+]=367.2022, found=367.2019.

Synthesis of methyl 4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-

carboxamido)benzoate (94):

NH

O OMe

O

A mixture of 5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid

(87) (72.3 mg, 0.311 mmol, 1 equi), thionyl chloride (0.63 mL) and dichloromethane

(2 mL) was heated at reflux for 4 hr. After removal of the solvent, a mixture of methyl

4-amino- benzoate (47 mg, 0.311 mmol, 1 equiv), dichloromethane (1.5 ml), DIPEA

(0.11mL, 0.622 mmol, 2 equiv) and DMAP (3.9 mg, 0.0311 mmol, 10 mol%) was

added to the residue and stirred overnight at r.t. The reaction was quenched with water

(5 mL) and the mixture was extracted with dichloromethane (3 X 5 mL). The



EtOAc/Hexane (5%) as eluent afforded compound (94) (61.4 mg, 54% over two

steps).76

Rf = 0.4 (20% EtOAc/Hexane); 1H NMR (200 MHz, CDCl3 ) δ 8.45 (s, 1H),

7.98 (s, 1H), 7.94 (s, 1H), 7.85 (d, J=1.6Hz, 1H), 7.75 (s, 1H), 7.71 (s, 1H), 7.55 (dd,

J=8.4,1.6Hz, 1H), 7.31 (d, J=8.6Hz, 1H), 3.85 (s, 3H), 1.65 (s, 4H), 1.24 (s, 12H); 13

C

NMR (75 MHz, CDCl3) δ 166.9, 166.7, 149.9, 146.0, 142.8, 131.8, 131.0, 127.2, 126.3,

87

125.6, 124.0, 119.5, 52.2, 35.1, 34.9, 34.8, 34.6, 31.9, 31.8.

Synthesis of N-(4-(hydroxycarbamoyl)phenyl)-5,5,8,8-tetramethyl-5,6,7,8-

tetrahydronaphthalene-2-carboxamide (76):

NH

O NHOH

O

To a solution of compound (94) (15.2 mg, 0.0416 mmol, 1 equiv) in THF (1 mL)

and MeOH (1 mL) at 0 0C was added a 50% aqueous solution of NH2OH (2.5 mL,

41.6 mmol, 1000equiv.) followed by a 1M solution of KOH (0.3 mL, 0.29 mmol, 7

equiv.). The reaction mixture was stirred at r.t. for 27 hr. This mixture was acidified

with citric acid to PH 4 and extracted with ethyl acetate. The combined extracts were

washed with water and brine, dried over Na2SO4, filtered and concentrated on a rotary

evaporator. Purification by octadecyl-functionalized silica gel column chromatography

using MeOH/H2O (5% to 95%) as eluent afforded compound (76) (7.8 mg, 51%).77

1H

NMR (400 MHz, CD3OD ) δ 7.93 (s, 1H), 7.84-7.75 (m, 4H), 7.69 (d, J=6.8Hz, 1H),

7.46 (d, J=7.6Hz), 1.74 (s, 4H), 1.34 (s, 6H), 1.31 (s, 6H); 13

C NMR (75 MHz, CD3OD)

δ 168.0, 166.6, 149.4, 145.4, 142.2, 131.8, 130.3, 127.6, 127.6, 126.8, 126.2, 124.4,

120.3, 120.0, 34.9, 34.7, 34.3, 34.2, 30.9, 30.8; HRMS (ESI): m/z calcd. for

[( M+H)+]=367.2022, found=367.2015.

88

Synthesis of N-(2-amino-4-hydroxyphenyl)-5,5,8,8-tetramethyl-5,6,7,8-

tetrahydronaphthalene-2-carboxamide (77):

NH

NH2

OOH

HBTU (109.6 mg, 0.289 mmol, 1.1 equiv) was added to a solution of 3,4-

diaminophenol (32.6 mg, 0.263 mmol, 1 equiv), compound (87) (61 mg, 0.263 mmol,

1 equiv), HOBt (177.4 mg, 1.313 mmol, 5 equiv) and DIPEA (0.14 mL, 0.789 mmol, 3

equiv) in DMF (2 mL) at r.t. The resulting mixture was maintained at r.t. and stirred

for 14 hr. Then the reaction mixture was diluted with ethyl acetate and poured into

water (5 mL). This mixture was extracted with ethyl acetate (3 X 5 mL). The



EtOAc/Hexane (2% to 10%) as eluent afforded compound (77) (48 mg, 54%). Rf =

0.45 (70% EtOAc/Hexane); 1H NMR (400 MHz, CD3OD) δ 7.95 (d, J=2Hz, 1H), 7.69

(dd, J=8,2Hz, 1H), 7.44 (d, J=8.4Hz, 1H), 6.95 (d, J=8Hz, 1H), 6.35 (d, J=2.4Hz, 1H),

6.22 (dd, J=8.4, 2.4Hz, 1H), 1.74 (s, 4H), 1.33 (s, 6H), 1.30 (s, 6H); 13

C NMR (75

MHz, CD3OD) δ 168.2, 156.9, 149.1, 145.2, 144.0, 131.4, 127.7, 126.7, 126.2, 124.5,

116.4, 105.7, 103.6, 34.9, 34.7, 34.3, 34.2, 30.9, 30.8; HRMS (ESI): m/z calcd. for

[( M+H)+]=339.2073, found=339.2090.

89

Synthesis of 6-bromo-1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene (103):

Br

To a solution of 2,5-dichlorol-2,5-hexanediol (84) (180.3 mg, 0.946 mmol, 1 equiv)

and bromobenzene (386.4 mg, 2.365 mmol, 2.5 equiv) in dichloromethane (1 mL),

aluminium trichloride (13 mg, 0.0946 mmol, 10 mol%) was added at r.t. The resulting

mixture was stirred overnight at r.t. The reaction was quenched with water (5 mL) and

the mixture was extracted with ethyl acetate (2 X 5 mL). The combined extracts were

washed with 5% aqueous solution of NaHCO3, water and brine, dried over MgSO4,


chromatography using hexane as eluent afforded compound (103) (242.7 mg, 96%). Rf

= 0.7 (Hexane); 1H NMR (500 MHz, CDCl3 ) δ 7.43 (d, J=2Hz, 1H), 7.25 (dd,

J=8.5,2Hz, 1H), 7.19 (d, J=8.5Hz, 1H), 1.69 (s, 4H), 1.29 (s, 6H), 1.27 (s, 6H); 13

C

NMR (125 MHz, CDCl3) δ 147.6, 144.1, 129.6, 128.9, 128.7, 119.66, 35.1, 35.0, 34.7,

34.3, 32.0, 31.8.

Synthesis of methyl 5',5',8',8'-tetramethyl-5',6',7',8'-tetrahydro-2,2'-binaphthyl-

6-carboxylate (105):

90

O

OMe

To a solution of aromatic bromide (103) (96.9 mg, 0.363mmol, 1 equiv) in THF (1

mL) at -78 0C, a 2.56 M solution of nBuLi (0.29 mL, 0.74 mmol, 2 equiv) was added.

After stirring at -78 0C for 1 hr, this solution of aryllithium reagent was added to a

mixture of ZnCl2 (99 mg, 0.73 mmol, 2 equiv) in THF (1 mL) which had been

precooled to -78 0C. After 1 hr at -78

0C and 1 hr at r.t., the resultant arylzinc mixture

was added to a solution of methyl 6-bromo-2-naphthoate (82 mg, 0.309 mmol, 0.85

equiv) and Ni(PPh3)4 (6.9 mg, 0.0073 mmol, 2 mol%) in THF (0.6 mL) which had

been precooled to 5 0C. The reaction mixture was allowed to warm to r.t. over 30 min

period and stirred for additional 30 min at r.t.. The reaction was quenched with ice (2 g)

and 10% aqueous HCl (2 mL) and the mixture was extracted with ether (2 X 5 mL).

The combined extracts were washed with sat. aqueous solution of NaHCO3, water and

brine, dried over MgSO4, filtered and concentrated on a rotary evaporator. Purification

by column chromatography using EtOAc/Hexane (10%) as eluent followed by

crystallization from ether at -20 0C afforded compound (104) (52.7 mg, 39%). Rf = 0.3

(20% EtOAc/Hexane); 1H NMR (300 MHz, CDCl3 ) δ 8.63 (s, 1H), 8.10 (d, J=1.8Hz,

1H), 8.07 (d, J=1.5Hz, 1H), 8.04 (s, 1H), 8.01 (d, J=8.7Hz, 1H), 7.94 (d, J=8.7Hz, 1H),

7.81 (dd, J=8.7,1.8Hz, 1H), 7.66 (d, J=2.1Hz, 1H), 7.50 (dd, J=8.1,1.8Hz, 1H), 7.45 (d,

J=8.4Hz, 1H), 1.75 (s, 4H), 1.39 (s, 6H), 1.35 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ

91

167.5, 145.7, 145.0, 141.5, 137.9, 136.0, 131.7, 131.0, 129.9, 128.5, 127.5, 127.3,

126.8, 125.9, 125.8, 125.4, 125.0, 52.5, 35.3, 35.2, 34.7, 34.4, 32.2, 32.1.

Synthesis of N-hydroxy-5',5',8',8'-tetramethyl-5',6',7',8'-tetrahydro-2,2'-

binaphthyl-6-carboxamide (78):

O

NH

OH

To a solution of compound (104) (9.2 mg, 0.0247 mmo, 1 equivl) in THF (1 mL)

and MeOH (1 mL) at 0 0C was added a 50% aqueous solution of NH2OH (1.6 ml, 24.7

mmol, 1000 equiv) followed by a 1 M solution of KOH (0.17 mL, 0.17 mmol, 7equiv).

The reaction mixture was stirred at r.t. for 50 hr. This mixture was acidified with citric

acid to PH 5 and extracted with ethyl acetate. The combined extracts were washed

with water and brine, dried over Na2SO4, filtered and concentrated on a rotary

evaporator. Purification by reverse phase HPLC using MeOH/H2O (5% to 95%) as

eluent afforded compound (78) (4.3 mg, 47%). 1H NMR (400 MHz, CD3OD ) δ 8.30 (s,

1H), 8.10 (s, 1H), 8.03-7.80 (m, 4H), 1.76 (s, 4H), 1.37 (s, 6H), 1.33 (s, 6H); 13

C NMR

(75 MHz, CD3OD) δ 168.2, 146.5, 145.7, 142.1, 138.8, 136.6, 133.0, 130.4, 129.7,

128.3, 127.5, 126.4, 125.9, 125.7, 124.9, 36.3, 36.1, 35.4, 35.1, 32.3, 32.2; HRMS

(ESI): m/z calcd. for [( M-H)+]=372.1964, found=372.1970.

92

Synthesis of (E)-methyl 3-(4-bromophenyl)acrylate (108):

Br

OMe

O

A mixture of 4-bromobenzaldehyde (185 mg, 1 mmol, 1 equiv) and

(methoxycarbonyl methylene)- triphenylphosphorane (502 mg, 1.5 mmol, 1.5 equiv) in

deionized water (5 mL) was stirred at 90 0C for 20 min. The reaction mixture was

cooled to r.t. and extracted with dichloromethane (2 X 5 mL). The combined extracts

were washed with water and brine, dried over MgSO4, filtered and concentrated on a

rotary evaporator. Purification by column chromatography using EtOAc/Hexane (2 %)

as eluent afforded compound (108) (176 mg, 73%). Rf = 0.6 (20% EtOAc/Hexane); 1H

NMR (300 MHz, CDCl3 ) δ 7.62 (d. J=15.9Hz, 1H), 7.51 (m, 2H), 7.38 (m, 2H), 6.42

(d, J=15.9Hz, 1H), 3.80 (s, 3H); 13

C NMR (75 MHz, CDCl3) δ 167.4, 143.7, 133.5,

132.3, 129.6, 124.8, 118.7, 52.0.

Synthesis of (E)-methyl 3-(4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-

2-yl)phenyl)acrylate (109):

OMe

O

To a solution of 6-bromo-1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene (103)

(461 mg, 1.725 mmol, 1 equiv) in THF (2.5 mL) at -780C, a 2.436 M solution of

93

nBuLi (1.14 mL, 2.76 mmol, 1.6 equiv) was added in one portion. After the mixture

was stirred at -78 0C for 40 min, (i-PrO)3B (1.2 mL, 5.175 mmol, 3 equiv) was added.

After the reaction mixture was stirred at -78 0C for 20 min, the cooling bath was

removed. This mixture was then stirred at r.t. overnight. The reaction was quenched

with 10% aqueous HCl (15 ml) and the mixture was extracted with EtOAc (2 X 100

mL). The combined extracts were washed with water and brine, dried over Na2SO4,

filtered. Concentration on a rotary evaporator afforded 5,5,8,8-

tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylboronic acid (110), which was used

directly for Suzuki coupling without further purified.

A mixture of (E)-methyl 3-(4-bromophenyl)acrylate (108) (125.5 mg, 0.521 mmol,

1 equiv), CsF (146 mg, 1.042 mmol, 2 equiv), Pd(OAc)2 (7 mg, 0.0312 mmol, 6 mol%)

and PPh3 (32.7 mg, 0.1247 mmol, 0.24 equiv) in THF (15 mL) was stirred at r.t. for 30

min. A solution of 5,5,8,8- tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylboronic acid

(110) (241.7 mg, 1.042 mmol, 2 equiv) in THF (5 mL) was added to above mixture

and heated to reflux. After 22 hr, the reaction mixture was cooled to r.t. and diluted

with EtOAc. This mixture was washed with water and brine, dried over MgSO4,


chromatography using EtOAc/Hexane (2%) as eluent afforded compound (109) (76.2

mg, 42%). Rf = 0.5 (10% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3 ) δ 7.74 (d,

16Hz, 1H), 7.62-7.54 (m, 5H), 7.41-7.38 (m, 2H), 6.49 (d, J=18Hz, 1H), 3.82 (s, 3H),

1.73 (s, 4H), 1.35 (s, 6H), 1.32 (s, 6H); 13

C NMR (75MHz, CDCl3) δ 167.8, 145.6,

94

145.0, 144.8, 143.7, 137.5, 133.1, 128.7, 127.6, 127.4, 125.4, 124.5, 117.5, 51.9, 35.3,

35.2, 34.6, 34.4, 32.1, 32.0.

Synthesis of (E)-N-hydroxy-3-(4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-

naphthalen-2-yl)phenyl)acrylamide (79):

NHOH

O

To a solution of compound (109) (20.5 mg, 0.059 mmol, 1 equiv) in THF (1.5 mL)

and MeOH (1.5 mL) at 0 0C was added a 50% aqueous solution of NH2OH (3.6ml, 59

mmol, 1000 equiv) followed by a 1 M solution of KOH (0.42 mL, 0.413 mmol,

7equiv). The reaction mixture was stirred at r.t. for 46 hr. This mixture was acidified

with 1 N citric acid to PH 5 and extracted with ethyl acetate. The combined extracts

were washed with water and brine, dried over Na2SO4, filtered and concentrated on a

rotary evaporator. Purification by reverse phase HPLC using MeOH/H2O (5% to 95%)

as eluent afforded compound (79) (12.5 mg, 61%). 1H NMR (300 MHz, CD3OD ) δ

7.62-7.39 (m, 8H), 6.49 (d, J=15.9Hz, 1H), 1.74 (s,4H), 1.34 (s, 6H), 1.30 (s, 6H); 13

C

NMR (75 MHz, CD3OD) δ 165.2, 145.2, 144.5, 143.0, 139.9, 137.4, 133.6, 128.1,

127.0, 127.0, 124.7, 124.0, 116.8, 35.1, 34.9, 34.1, 33.9, 31.1, 31.0; HRMS (ESI): m/z

calcd. for [( M-H)+]=348.1964, found=348.1960.

95

Synthesis of methyl 5-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-

pentanoate (114):

OMe

O

A Schlenk flask was charged with LiCl (53.2 mg, 1.254 mmol, 1 equiv) and dried

under vacuum at 160 0C for 30 min. Zinc powder (246 mg, 3.762 mmol, 3 equiv) was

added to the flask, and the mixture of LiCl and Zn was dried again under the same

conditions for additional 30 min. After the mixture was allowed to cool to r.t., THF

(1.25 mL) was added. The resulting suspension was treated with 1,2-dibromoethane

(0.00545 mL, 0.0627 mmol, 5 mol%) and heated with a heat gun until foaming. The

process was repeated twice. TMSCl (0.0016 mL, 0.0125 mmol, 1 mol%) was added

and the mixture was stirred for 20 min. To this mixture, a solution of I2 (32 mg, 0.1254

mmol, 10 mol%) in THF (0.3 mL) was added followed by a solution of methyl

5-bromoveratrole (244.6 mg, 1.254 mmol, 1 equiv) in THF (1.3 mL). This reaction

mixture was heated to 50 0C and stirred for 24 hr. The oil bath was removed and the

mixture was cooled down to r.t. To this alkylzinc bromide-lithium chloride complex, a

solution of aromatic bromide (103) (134 mg, 0.502 mmol, 0.4 equiv) and Pd(PPh3)4

(23.2 mg, 0.02 mmol, 4 mol%) in THF (1 mL) was added at r.t.. This mixture was

stirred at r.t. overnight. The reaction was quenched with sat. aqueous NH4Cl and the

96

mixture was extracted with EtOAc. The combined extracts were washed with water

and brine, dried over MgSO4, filtered and concentrated on a rotary evaporator.


compound (114) (22.7 mg, 15%).84

Rf = 0.4 (10% EtOAc/Hexane); 1H NMR (400

MHz, CDCl3 ) δ 7.21 (d, J=7.6Hz, 1H), 7.08 (s, 1H), 6.94 (d, J=7.6Hz, 1H), 3.66 (s,

3H), 2.57 (t, J=7.6Hz, 2H), 2.34 (t, J=7.6Hz, 2H), 1.69-1.63 (m, 8H), 1.27 (s, 6H), 1.26

(s, 6H); 13

C NMR (75 MHz, CDCl3) δ 174.4, 144.8, 142.4, 139.2, 126.6, 126.5, 125.8,

51.7, 35.5, 35.4, 35.3, 34.4, 34.2, 3.18, 3.16, 3.12, 3.13, 25.0.

Synthesis of N-hydroxy-5-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-

2-yl)pentanamide (80):

NHOH

O



56.5 mmol, 1000 equiv) followed by a 1 M solution of KOH (0.4 mL, 0.4 mmol, 7

equiv). The reaction mixture was stirred at r.t. for 16 hr. This mixture was acidified

with 1N citric acid to PH 5 and extracted with ethyl acetate. The combined extracts



97


7.18 (d, J=8.4Hz, 1H), 7.08 (s, 1H), 6.90 (d, J=8.4Hz, 1H), 2.54 (t, J=6.8Hz, 2H), 2.10

(t, J=6.8Hz, 2H), 1.67-1.60 (m, 8H), 1.24 (s, 6H), 1.23 (s, 6H); 13

C NMR (125 MHz,

CD3OD) δ 171.5, 144.1, 141.7, 138.8, 126.0, 125.9, 125.3, 34.9, 34.9, 34.8, 33.6, 33.4,

32.2, 30.8, 30.7, 25.0; HRMS (ESI): m/z calcd. for [( M+H)+]=304.2271,

found=304.2267.

Synthesis of methyl 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-

2-yl)hexanoate (118):

OMe

O

A Schlenk flask was charged with LiCl (74 mg, 1.745 mmol, 1 equiv) and dried






process was repeated twice. TMSCl (0.0023 ml, 0.0125 mmol, 1 mol%) was added and

the mixture was stirred for 20 min. To this mixture, a solution of I2 (32 mg, 0.1254

mmol, 10 mol%) in THF (0.3 mL) was added followed by a solution of methyl

6-bromohexanoate (367.1 mg, 1.756 mmol, 1 equiv) in THF (1.5 mL). This reaction

98



solution of aromatic bromide (103) (187.7 mg, 0.7024 mmol, 0.4 equiv) and Pd(PPh3)4

(32.4mg, 0.028 mmol, 4 mol%) in THF (1 ml) was added at r.t.. This mixture was

stirred at r.t. overnight. The reaction was quenched by sat. aqueous NH4Cl and the

mixture was extracted with EtOAc. The combined extracts were washed with water

and brine, dried over MgSO4, filtered and concentrated on a rotary evaporator.


compound (118) (17.6 mg, 7.9%).84

Rf = 0.4 (10% EtOAc/Hexane); 1H NMR (300

MHz, CDCl3 ) δ 7.22 (d, J=8.1Hz, 1H), 7.10 (d, J=1.8Hz, 1H), 6.95 (dd, J=8.1,1.8Hz,

1H), 3.68 (s, 3H), 2.56 (t, J=7.8Hz, 2H), 2.33 (t, J=7.8, 2H), 1.71-1.58 (m, 8H),

1.44-1.36 (m, 2H), 1.28 (s, 6H), 1.28 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 174.5,

144.8, 142.3, 139.6, 126.5, 126.5, 125.8, 51.7, 35.7, 35.4, 35.3, 34.4, 34.3, 34.1, 32.1,

32.1, 31.3, 29.2, 25.1.


2-yl)hexanamide (81):

NHOH

O



99






as eluent afforded compound (81) (6.1mg, 52%). 1H NMR (400 MHz, CD3OD ) δ

7.17 (d, J=8Hz, 1H), 7.07 (s, 1H), 6.89 (d, J=7.6Hz, 1H), 2.52 (t, J=6.8Hz, 2H), 2.07 (t,

J=6.4Hz, 2H), 1.66-1.57 (m, 8H), 1.36-1.32 (m, 2H), 1.24 (s, 6H), 1.23 (s, 6H); 13

C

NMR (75 MHz, CD3OD) δ 171.5, 144.1, 141.6, 139.1, 125.9, 125.8, 125.3, 35.0, 34.9,

34.9, 33.6, 33.4, 30.9, 30.9, 28.4, 25.2; HRMS (ESI): m/z calcd. for

[( M+H)+]=318.2428, found=318.2421.

Synthesis of 7-bromoheptanal (120):

Br H

O

To a solution of DMSO (0.31 mL, 4.357 mmol, 2.4 equiv) in dichloromethane (17

mL) at -78 0C, oxalyl chloride (0.19 mL, 2.18 mmol, 1.2 equiv) was added dropwise.

The mixture was stirred for 10 min and a solution of 7-bromoheptan-1-ol (354 mg,

1.815 mmol, 1 equiv) in dichloromethane (3.6 mL) was added. After stirring at -78 0C

for 15 min, Et3N (1.27 mL, 9.08 mmol, 5 equiv) was added. The resulting mixture was

stirred at -78 0C for 30 min and at r.t. for 2.5 hr. The reaction was quenched by sat.

100

aqueous NH4Cl and the mixture was extracted with ether. The combined extracts were

washed with water and brine, dried over MgSO4, filtered and concentrated on a rotary

evaporator. Purification by column chromatography using EtOAc/Hexane (2%) as

eluent afforded compound (120) (332.7 mg, 95%).85

Rf = 0.5 (20% EtOAc/Hexane);

1H NMR (400 MHz, CDCl3 ) δ 9.76 (t, 1.6Hz, 1H), 3.39 (t, J=7.8Hz, 2H), 2.44 (dt,

J=7.2Hz,1.6Hz, 2H), 1.88-1.81 (m, 2H), 1.67-1.60 (m, 2H), 1.49-1.32 (m, 4H); 13

C

NMR (75 MHz, CDCl3) δ 202.8, 43.9, 33.9, 32.7, 28.4, 28.1, 22.0.

Synthesis of methyl 7-bromoheptanoate (122):

Br OMe

O

To a solution of the 7-bromoheptanal (120) (439.6 mg, 2.28 mmol, 1 equiv) and

2-methyl-2-butene (10 mL) in tBuOH (40 mL), a solution of NaClO2 (617 mg, 6.83

mmol, 3 equiv) and NaH2PO4 (1.57 g, 11.39 mmol, 5 equiv) in H2O (40 mL) was

added at r.t.. This mixture was stirred at r.t. for 2 hr. The reaction was quenched with

H2O and the mixture was extracted with ether. The combined extracts were washed

with brine, dried over MgSO4, filtered. Concentration on a rotary evaporator afforded

crude 7-bromoheptanoic acid (121), which was directly used in the next reaction

without further purified.

Acetyl chloride (0.5 mL) was added to a solution of 7-bromoheptanoic acid (121)

prepared above in MeOH (7 mL) and this mixture was stirred at r.t. overnight.

101

Amberlite IRA-67 resin was added and the mixture was stirred for 15 min, filtered,

drived over MgSO4, filtered, concentrated on a rotary evaporator. Purification by

column chromatography using EtOAc/Hexane (2%) as eluent afforded compound (122)

(304mg, 60% over two steps). Rf = 0.3 (10% EtOAc/Hexane); 1H NMR (400 MHz,

CDCl3 ) δ 3.66 (s,3H), 3.40 (t, 6.6Hz, 2H), 2.31 (t, J=7.2Hz, 2H), 1.90-1.83 (m, 2H),

1.69-1.59 (m, 2H), 1.48-1.31 (m, 4H); 13

C NMR (75 MHz, CDCl3) δ 174.3, 51.7, 34.1,

34.0, 32.7, 28.4, 28.0, 24.9.

Synthesis of methyl 7-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-

2-yl)heptanoate (124):

OMe

O

A Schlenk flask was charged with LiCl (46 mg, 1.09 mmol, 1 equiv) and dried






process was repeated twice. TMSCl (0.0014 mL, 0.0109 mmo, 1 mol%l) was added

and the mixture was stirred for 20 min. To this mixture, a solution of I2 (27.5 mg,

102

0.109 mmol, 10 mol%) in THF (0.3 mL) was added followed by a solution of methyl

6-bromohexanoate (241.9 mg, 1.09 mmol, 1 equiv) in THF (1 mL). This reaction



solution of aromatic bromide (103) (145 mg, 0.55 mmol, 0.5 equiv) and Pd(PPh3)4 (25

mg, 0.0217 mmol, 4 mol%) in THF (1 mL) was added at r.t.. This mixture was stirred

at r.t. overnight. The reaction was quenched with sat. aqueous NH4Cl and the mixture

was extracted with EtOAc. The combined extracts were washed with water and brine,

dried over MgSO4, filtered and concentrated on a rotary evaporator. Purification by

column chromatography using EtOAc/Hexane (2%) as eluent afforded compound (124)

(39.4mg, 11%).84

Rf = 0.4 (10% EtOAc/Hexane); 1H NMR (400 MHz, CDCl3 ) δ 7.21

(d, J=7.6Hz, 1H), 7.08 (d, 1.6Hz, 1H), 6.93 (dd, J=8,1.6Hz, 1H), 3.66 (s, 3H), 2.53 (t,

J=6Hz, 2H), 2.30, J=7.6Hz, 2H), 1.66-1.55 (m, 8H), 1.36-1.31 (m, 4H), 1.27 (s, 6H),

1.26 (s, 6H); 13

C NMR (125 MHz, CDCl3) δ 173.2, 143.5, 141.0, 138.5, 125.3, 125.27,

124.6, 50.4, 34.6, 34.2, 34.1, 33.1, 33.1, 32.9, 30.8, 30.2, 28.1, 28.0, 23.9.


2-yl)heptanamide (82):

NHOH

O

103









7.17 (t, J=8Hz, 1H), 7.07 (s, 1H), 6.89 (t, J=7.6Hz, 1H), 2.51 (t, J=7.2Hz, 2H), 2.06 (t,

J=7.6Hz, 2H), 1.66 (s, 4H), 1.58 (m, 4H), 1.38-1.36 (m, 4H), 1.24 (s, 6H), 1.23 (s, 6H);

13C NMR (125 MHz, CD3OD) δ 171.6, 144.1, 141.5, 139.2, 125.9, 125.8, 125.3, 35.1,

34.9, 34.9, 33.6, 33.4, 32.3, 31.2, 30.9, 28.6, 28.5, 25.3; HRMS (ESI): m/z calcd. for

[( M+H)+]=330.2433, found=330.2430.

Synthesis of 5-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)pentanoic

acid (125):

OH

O

To a solution of methyl 5-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2–

104

yl )pentanoate (114) (118.4mg, 0.392 mmol, 1 equiv) in THF/H2O/MeOH (3 mL: 1

mL : 1 mL), a solution of 1N lithium hydroxide monohydrate (0.79 mL, 0.79 mmol, 2

equiv) was added, and the resulting mixture was stirred at r.t. for 20 hr. After most of

the THF and MeOH was evaporated, the aqueous phase was acidified with 1N solution

of HCl to PH 5.5 and extracted with ethyl acetate to afford the compound (125) (89.4

mg, 99%).1H NMR (300 MHz, CDCl3 ) δ 7.24 (d, J=8.1Hz, 1H), 7.13 (d, J=1.5Hz, 1H),

6.97 (dd, J=7.8,1.8Hz, 1H), 2.61 (t, J=6.9Hz, 2H), 2.42 (t, 7.2Hz, 2H), 1.71 (m, 8H),

1.31 (s, 6H), 1.30 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 180.4, 144.9, 142.4, 139.1,

126.6, 126.5, 125.9, 35.5, 35.4, 35.4, 34.4, 34.2, 34.1, 32.1, 32.1, 31.0, 24.7.

Synthesis of 4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)butan-

1-amine (127):

NH2

To a solution of carboxylic acid (125) (102 mg, 0.354 mmol, 1 equiv) in toluene

(2 mL) was added Et3N (0.0543 mL, 0.389 mmol, 1.1 equiv) followed by DPPA

(0.076 mL, 0.354 mmol, 1 equiv). The mixture was stirred at r.t. for 30 min, and then

heated to reflux overnight. After concentration on a rotary evaporator, the crude

isocyanate (126) was treated with 2 N solution of NaOH (2.7 mL) and THF (7 mL)

and stirred at r.t. for 30 min. The resulting solution was extracted with CH2Cl2 (2 X 30

mL). The combined extracts were washed with water and brine, dried over MgSO4,

105


chromatography using Et3N/MeOH/EtOAc (10:10:80) as eluent afforded compound

(127) (38.4 mg, 42%). Rf = 0.3 (Et3N/MeOH/EtOAc=10:10:80); 1H NMR (400 MHz,

CDCl3 ) δ 7.21 (d, J=8Hz, 1H), 7.10 (d, J=1.6, 1H), 6.95 (dd, J=8,1.6Hz, 1H), 2.75 (t,

J=6Hz, 2H), 2.58 (t, J=7.2Hz, 2H), 1.67-1.52 (m, 8H), 1.28 (s, 6H), 1.27 (s, 6H); 13

C

NMR (75 MHz, CDCl3) δ 144.8, 142.3, 139.4, 126.6, 126.5, 125.8, 42.0, 35.7, 35.4,

35.3, 34.4, 34.1, 32.1, 32.1, 28.9.

Synthesis of S-2-oxo-2-(4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-

yl)butylamino)ethyl ethanethioate (129):

HN

SAc

O

To a solution of the amine (127) (16.7 mg, 0.0644 mmol, 1 equiv) and

2-(acetylthio)acetic acid (26 mg, 0.193 mmol, 3 equiv) in dichloromethane (1.5 mL) at

0 0C, EDC/HCl (37 mg, 0.0773 mmol, 3 equiv) was added. The reaction mixture was

stirred at r.t. overnight and diluted with dichloromethane (30 mL).This mixture was

washed with 0.5 N solution of HCl (2 X 15 mL), sat. NaHCO3 (2 X 15 mL) and brine,

dried with Na2SO4 and concentrated on a rotary evaporator. Purification by column

chromatography using EtOAc/Hexane (5%) as eluent afforded compound (129) (24

mg, 99%).77

Rf = 0.5 ( 40% EtOAc/Hexane); 1H NMR (300 MHz, CDCl3 ) δ 7.21 (d,

J=8.1Hz, 1H), 7.08 (d, J=1.8Hz), 6.93 (dd, J=8.1,1.8Hz, 1H), 6.18 (br. s, 1H), 3.56 (s,

106

2H), 3.25 (q, J=6.6Hz, 2H), 2.56 (t, J=7.8Hz, 1H), 2.39 (s, 3H), 1.67-1.52 (m, 8H),

1.27 (s, 6H), 1.26 (s, 6H); 13

C NMR (75 MHz, CDCl3) δ 196.2, 168.2, 144.9, 142.5,

139.1, 126.6, 126.5, 125.8, 39.9, 35.4, 35.4, 35.3, 34.4, 34.1, 33.3, 32.1, 32.1, 30.5,

29.3, 28.8.

Synthesis of 2-mercapto-N-(4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-

2- yl)butyl)acetamide (83):

HN

SH

O

A desoxygenated solution of MeONa (3.6 mg, 0.0655 mmol, 1 equiv) in MeOH

(1.5 mL) was added to S-2-oxo-2-(4-(5,5,8,8-tetramethyl-5,6,7,8-

tetrahydronaphthalen-2- yl)butylamino)ethyl ethanethioate (129) (24.6 mg, 0.0655

mmol, 1 equiv). The solution was stirred at r.t. for 4 hr. The reaction was quenched

with AcOH (2 mL) and concentrated on a rotary evaporator. The residue was diluted

with EtOAc (30 mL) and washed with water and brine, dried over Na2SO4, filtered and


EtOAc/Hexane (5%) as eluent afforded compound (83) (16 mg, 74%).77

Rf = 0.4 (40%

EtOAc/Hexane); 1H NMR (400 MHz, CDCl3 ) δ 7.21 (d, J=7.6Hz, 1H), 7.08 (s, 1H),

6.94 (dd, J=8,2Hz, 1H), 6.68 (br. s, 1H), 3.31 (q, J=6.4, 2H), 3.23 (d, J=8.8Hz, 2H),

2.58 (t, J=7.2Hz, 2H), 1.83 (t, J=8.8Hz, 1H), 1.67-1.57 (m, 8H), 1.27 (s, 6H), 1.26 (s,

107

6H); 13

C NMR (75 MHz, CDCl3) δ 169.2, 144.9, 142.5, 139.1, 126.7, 126.5, 125.8,

40.0, 35.4, 35.4, 35.3, 34.4, 34.1, 32.1, 29.4, 28.8, 28.5; HRMS (ESI): m/z calcd. for

[( M-H)+]=332.2048, found=332.2048.

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