8

ABSTRACT OF THE THESIS

“DESIGN AND SYNTHESIS OF NOVEL HETEROCYCLIC COMPOUNDS

FROM ANACARIDIUM OCCIDENTALE AND THEIR BIOLOGICAL

EVALUATION”

The thesis is consists of five chapters

The first chapter deals with the survey of literature with particular

reference to the

i. The introductory aspects of anacardic acid derivatives

ii. Isolation of anacardic acid

iii. Biological activity of various anacardic acid analogs.

In Chapter II, Synthesis and anti-bacterial activity of some substituted

amino anacardic acids derivatives have been described.

In Chapter III, Synthesis and anti-bacterial activity of some sulphonamido

analogues of anacardic acid have been described.

In Chapter IV, Synthesis and anti-bacterial activity of some urea analogues

of anacardic acid have been described.

In Chapter V, Synthesis and anti-bacterial activity of some thiourea

analogues of anacardic acid have been described.

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Chapter-1: Introduction

The cashew tree (Anacardium occidentale) a species originally native to

Brazil where it is still cultivated, also grown in a large number of other

tropical and sub-tropical countries. It is now commonly found along the

coastal regions of India. Cashew nut shell liquid (CNSL) is a by-product of

cashew nut industry and anacardic acid ene mixture (Figure 1.1) is isolated

from CNSL which are salicylic acid derivatives with a nonisoprenoid alk(en)yl

side chain.

Figure 1.1: Ene mixture of anacardic acid

Each consists of a salicylic acid substituted with an alkyl chain that

has 15 carbon atoms. Anacardic acid is a mixture of saturated and

unsaturated molecules. The exact mixture depends on the species of the

plant of which the 15 carbon unsaturated side chain found in the cashew

plant is very lethal to Gram positive bacteria.

It is primarily used for tooth abscesses, it is also active against acne,

some insects, tuberculosis, and MRSA. It is primarily found in foods such as

cashew nuts, cashew apples, and cashew nutshell oil, but also in mangos

and Pelargonium geraniums.

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Chapter-2: Synthesis and anti-bacterial activity of some

substituted amino anacardic acid derivatives

Owing to the extensive biological properties of anacardic acid

derivatives, we were also prompted to develop several such analogues of

anacardic acid and screen them for their potential anti-microbial properties.

The present chapter deals with our efforts to make diversely functionalized

anacardic acid derivatives. The synthesis of all the new compounds 6a–6u

and 10a-10s is depicted in Scheme 2.1. The above new compounds were

screened for their anti-bacterial activity screenings against Escherichia coli,

Pseudomonas aeruginosa, Streptococcus pyogenes and Staphylococcus

aureus bacterial strains using agar well diffusion method. The anti-bacterial

activity of the analogues was compared with standard drug Ampicillin.

Scheme 2.1

Reagents and Conditions: a) 10 % Pd/C, EtOH, H2 (50 psi), RT, 2 h;

b) (CH3)2SO4, K2CO3, CH3CN, 90 °C, 24 h; c) LiAlH4, THF, 0 °C-RT, 18 h; d)

Methane sulphonyl chloride, Et3N, DCM, 0°C-RT, 3 h; e) different amines,

Et3N, CH3CN, 85 °C, 3-18 h;

11

Having synthesized the 2-substituted amine analogues of anacardic

acids, we then turned our attention to synthesize 6-substituted amino

derivatives (10a-10s) as depicted in Scheme 2.2. The bromo compound 9

thus obtained was treated with different substituted aliphatic or aromatic

amines resulted compounds 10a-s respectively (Scheme 2.2). All the

synthesized compounds (6a-6u, 10a-10s) were characterized by 1H NMR,

FT-IR, and Mass analysis. Some of the derivatives and intermediates were

characterized by 13C NMR also.

Scheme 2.2

Reagents and Conditions: a) (CH3)2SO4, K2CO3, CH3CN, 90 °C, 24 h;

b) O3, MeOH, DCM, -78 °C; c) MeOH, NaBH4, 18 h, 0 °C-RT; d) CBr4,

Pyridine, Ph3P, DCM, 0 °C-RT, 6 h; e) different amines, K2CO3, CH3CN, 90

°C, 4-12 h.

Compounds 6a-6u & 10a-10s were tested against two Gram negative

strains viz., i) Escherichia coli and ii) Pseudomonas aeruginosa and two

Gram positive strains viz., i). Streptococcus pyogenes and ii) Staphylococcus

12

aureus using agar well diffusion method. The anti-bacterial activity of the

analogues was compared with standard drug Ampicillin.

Chapter-3: Synthesis and antibacterial activity of some

sulphonamido analogues of anacardic acid

As discussed in the Chapter-1 and Chapter-2 about biological

significance of various anacardic acid derivatives, we now turned our

attention towards the synthesis of some amide analogues of anacardic acids.

Literature survey revealed that functionalized amide derivative of

anacardic acid such as N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-

pentadecyl-benzamide (CTPB, Figure 3.1) was found to be the first specific

activator of histone acetyltransferase (HAT) activity of p300.

In view of the immense potential of anacardic acid and its derivatives

as selective and specific biological agents, the aim of the present work is to

make use of abundantly and cheaply available anacardic acid and to make

synthons for generating novel class of bioactive compounds such as

functionlised sulfonamido analogues of anacardic acids and screen them for

potential anti-bacterial properties.

The synthesis of all the new compounds 13a–13l is depicted in

Scheme 3.1. The crude products were purified by column chromatography

13

to yield the title compounds 13a-13l (Scheme 3.1).

Scheme 3.1

Reagents and Conditions: a) NaN3, DMF, 100 oC, 2 h; b) 10 % Pd/C, H2

(50 psi), 2 h; c) different sulphonyl chlorides, Et3N, DCM, 0 oC-RT.

Having synthesized the sulfonamide analogues of the anacardic acid

with the methyl amine ortho to the methoxy group on the phenyl ring, we

have synthesized sulfonamide analogues (16a-16l) on side chain 15 to as

depicted in Scheme 3.2 tested for their biological activity.

The amino compound 15 was reacted with various substituted

sulfonyl chlorides in DCM using Et3N as a base and isolated sulfonamido

analogues of anacardic acid 16a-16l (Scheme 3.2). All the intermediates

and synthesized analogues (13a-13l, 16a-16l) were characterized by 1H

NMR, FT-IR, and Mass analysis. Some of the derivatives and intermediates

were characterized by 13C NMR also.

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Scheme 3.2

Reagents and Conditions: a) O3, MeOH, DCM, -78 oC, 6 h; b) MeOH,

NaBH4, 18 h, 0 oC-RT; c) CBr4, Pyridine, PPh3, DCM, 0 oC-RT, 8 h; d) NaN3,

DMF, 100 oC, 3 h; e)10% Pd/C, EtOH, H2 (50 psi), RT, 2 h; f) different

sulfonyl chlorides, Et3N, DCM, 0°C-RT, 3 h.

Compounds 13a–13l and 16a-16l were tested against two Gram

negative strains viz., i) Escherichia coli and ii) Pseudomonas aeruginosa and

two Gram positive strains viz., i).Staphylococcus aureus and ii) Streptococcus

pyogenes using agar well diffusion method. The anti-bacterial activity of the

analogues was compared with standard drug Ampicillin.

Chapter-4: Synthesis and Antibacterial Activity of some urea

analogues of anacardic acid

As discussed earlier in the previous chapters about the biological

significance of various analogues of anacardic acids, in the present chapter

we intended to synthesize some highly substituted urea and thiourea

15

analogues of anacardic acid and screen them for their potential biological

activities.

In this regard, the amino compound 12 was synthesized following the

procedure outlined in Chapter-3 via its azido analogue. Compound 12 was

then reacted with substituted isocyanates derivatives in chloroform at room

temperature to afford the corresponding urea analogues of anacardic acid

ie., 17a-17k (Scheme 4.1)

Scheme 4.1:

Reagents and Conditions: a) different isocynates, CHCl3, RT

Following the similar lines of synthesis in Scheme 4.1, we have

synthesized the urea analogues (18a-k) on side chain of anacardic acid from

the amino compound 15 (scheme 4.2). The required amino compound 15

was synthesized following the protocol presented in Chapter-3. The amino

compound 15 was then reacted with substituted isocyanates derivatives in

CHCl3 at RT to afford the corresponding urea analogues of anacardic acid

i.e., 18a-18k. All the synthesized analogues (17a-17k, 18a-18k) were

characterized by 1H NMR, FT-IR, and Mass analysis. Some of the derivatives

and intermediates were characterized by 13C NMR also.

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Scheme 4.2:

Reagents and Conditions: a) different isocynates, CHCl3, RT

Compounds 17a–17k, 18a-18k were tested against two Gram

negative strains viz., i) Escherichia coli and ii) Pseudomonas aeruginosa and

two Gram positive strains viz., i). Streptococcus pyogenes and ii)

Staphylococcus aureus using agar well diffusion method. The anti-bacterial

activity of the analogues was compared with standard drug Ampicillin.

Chapter-5: Synthesis and Antibacterial Activity of some thiourea

analogues of anacardic acid

As discussed earlier in the previous chapters about the biological

significance of various analogues of anacardic acids, in the present chapter

we intended to synthesize some highly substituted urea and thiourea

analogues of anacardic acid and screen them for their potential biological

activities.

In this regard, the amino compound 12 was synthesized following the

procedure outlined in Chapter-3 via its azido analogue. Compound 12 was

then reacted with substituted isothiocyanates derivatives in chloroform at

room temperature to afford the corresponding urea analogues of anacardic

acid ie., 19a-19k (Scheme 5.1)

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Scheme 5.1

Reagents and Conditions: a) different isothiocynates, CHCl3, RT

Following the similar lines of synthesis as mentioned in Scheme 5.1,

we have synthesised the thiourea analogues (20a-20f) on side chain of

anacardic acid from the amino compound 15 (scheme 5.2). The required

amino compound 15 was synthesized following the protocol presented in

Chapter- 3. The amino compound 15 was then reacted with substituted

isothiocynate derivatives in CHCl3 at RT to afford the corresponding thiourea

analogues of anacardic acid (20a-20f) (Scheme 5.2). All the synthesized

analogues (19a-19f, 20a-20f) were characterized by 1H NMR, FT-IR, and

Mass analysis. Some of the derivatives and intermediates were characterized

by 13C NMR also.

Scheme 5.2

Reagents and Conditions: a) different isothiocynates, CHCl3, RT.

Compounds 19a-19f and 20a-20f were tested against two Gram

negative strains viz., i) Escherichia coli and ii) Pseudomonas aeruginosa and

two Gram positive strains viz., i). Streptococcus pyogenes and ii)

Staphylococcus aureus using agar well diffusion method. The anti-bacterial

activity of the analogues were compared with standard drug Ampicillin.

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TABLE OF CONTENTS

Acknowledgements i-ii

Abstract of the Thesis iii-xiii

Table of Contents xiv-xv

General Remarks xvi-xvii

Abbreviations xviii-xx

CHAPTER 1: Introduction 1

References 12

Aim and objectives 21

CHAPTER 2: Synthesis and Anti-bacterial Activity of Some substituted

amino Anacardic Acid Derivatives

Introduction 23

Present work 24

Experimental 43

References 73

Spectra 74

CHAPTER 3: Synthesis and Antibacterial Activity of some sulphonamide

analogues of anacardic acid

Introduction 101

Present work 102

Experimental 117

References 137

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Spectra 138

CHAPTER 4: Synthesis and Antibacterial Activity of some urea analogues of

anacardic acid

Introduction 157

Present work 157

Experimental 169

Spectra 185

CHAPTER 5: Synthesis and Antibacterial Activity of some thiourea

analogues of anacardic acid

Introduction 203

Present work 203

Experimental 214

Spectra 223

List of publications 231

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GENERAL REMARKS

All melting points were recorded on a superfit (India) capillary melting

point apparatus and are uncorrected.

Infrared spectra were recorded on a Perkin Elmer FT-IR spectrometer.

Samples were recorded either in neat, KBr wafers or in DCM as a thin

film.

1H NMR and 13C NMR Spectra were recorded on a Varian EM-360

spectrometer 400MHz. The samples were made in CDCl3 and DMSO-

d6 using TMS (δ = 0 ppm) as internal standard. Spectral assignments

are as follows: (1) chemical shifts on the δ scale, (2) standard

abbreviation for multiplicity, that is, s = singlet, d = doublet, t= triplet,

q = quartet, m = multiplet, brs = broad singlet. (3) Coupling constant J

in Hertz.

The mass spectra were recorded on Agilent ion trap MS.

Thin layer chromatography (TLC) was performed using silica gel 60-

F254 (0.5-mm) glass plates. Visualization of the spots on TLC plates

was achieved either by exposure to iodine vapour or UV light or

nihydrin solution and heating the plates to 100 oC.

Column chromatography was performed using silica gel (60-120

mesh/100-200 mesh) and executed under nitrogen pressure (flash

chromatography) conditions, the column was usually eluted with ethyl

acetate-petroleum ether or MeOH-CHCl3.

All solvents and reagents were purified by standard techniques.

Evaporation of solvents were carried out under reduced pressure on

Buchi rotary evaporator below 45 oC.

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The names of all the compounds given in the experimental section

were taken from Chem draw 11.