1

Chapter 1 - Thieno[2,3-d]Pyrimidines - Introduction and literature review

S. No Name of the subtitle Page No

1.1 Introduction 2

1.1.1 Computational approaches in drug discovery 3

1.1.2 Introduction to thienopyrimidines 5

1.1.2.1 Chemistry of thienopyrimidine 6

1.1.2.2 Synthetic approaches to thienopyrimidines 6

1.1.2.2.1 Synthesis of thienopyrimidine by pyrimidine ring closure 6

1.1.2.2.2 Synthesis of thienopyrimidines by thiophene ring closure 9

1.1.2.3 Chemical properties of thienopyrimidines 10

1.1.2.3.1 Nucleophilic substitution 10

1.1.2.3.2 Electrophillic substitution 13

1.1.2.4 Biological activities of thienopyrimidines 15

1.2 Literature review 16

1.3 Scope and objectives of the present work 33

2

1.1 Introduction

Drug discovery is the process by which new candidate medications are

discovered. Modern drug discovery involves the identification of screening hits and

optimization of those hits to increase the affinity, selectivity (to reduce the potential of

side effects), efficacy/potency, metabolic stability (to increase the half-life), and oral

bioavailability. Once a compound that fulfills all of these requirements has been

identified, the process of drug development begins prior to clinical trials. One or more

of these steps may, but not necessarily, involve computer-aided drug design. The

process of finding a new drug against a chosen target for a particular disease usually

involves high-throughput screening (HTS), wherein large libraries of chemicals are

tested for their ability to modify the target. Another important function of HTS is to

show how selective the compounds are for the chosen target. The idea is to find a

molecule which will interfere with only the chosen target, but not other, related

targets. The advantage is a perfect drug candidate will be identified from these early

screening runs. It is more often observed that several compounds are found to have

some degree of activity, and if these compounds share common chemical features,

one or more pharmacophores can then be developed. Hence, medicinal chemists

attempt to use structure-activity relationships (SAR) to improve certain features of the

lead compound;

Enhance the activity against the chosen target

Reduce unrelated and toxic effects

Improve ADME properties of the molecule.

This process will require several iterative screening steps, during which, it is hoped

that the properties of the new molecular entities will improve and allow the potential

compounds to go forward to in vitro and in vivo screening test for the desired activity.

3

A range of parameters can be used to assess the quality of a compound, or a series

of compounds, as described in the Lipinski's rule of five. Such parameters include

calculated properties such as molecular weight, cLogP to estimate lipophilicity, polar

surface area (PSA), number of hydrogen donors, hydrogrn acceptors and also

measured properties, such as potency, in vitro measurement of metabolic clearance

etc. Some descriptors such as ligand efficiency (LE) and lipophilic efficiency (LiPE)

combine such parameters to assess drug likeness.

It is often possible to start drug discovery by identifying lead from a molecule

which already has some of the desired properties. Such a molecule might be extracted

from a natural product or even be a drug on the market which could be improved upon

(socalled "me too" drugs). Other methods, such as virtual HTS, where screening is

done using computer software generated models and attempt can also be made either

to "dock" virtual libraries to a target or to carryout screening of focused screening

libraries for the desired target.

1.1.1 Computational Approaches in Drug Discovery

The major objectives of the medicinal chemists are transformation of

pathobiochemical and physiological data into a “chemical language” with the aim of

designing molecules interacting specifically with the degenerating processes in the

diseased organism. One of the most important and essential fields in the modern

medicinal chemistry is the computational chemistry. At today, one part of it,

frequently named in silico drug discovery.

Taking into account the fact that potential therapeutic targets are being disclosed

with increasing frequency, and this exponential growth will continue during the next

4

decades, there is a need for rapid and effective target validation and for accelerated

lead discovery procedures. The number of cellular targets (enzymes, receptors,

biopolymers, etc.) with established three-dimensional structure is now increasing

exponentially. Structural information derived from X-ray analysis of enzyme inhibitor

conglomerates has been and continued to be very valuable for the design of new types

of ligands.

The most important characteristic feature of the rational drug design is to utilize in

a positive way all known information of the system under the study for developing a

strategy for potential leads in drug discovery. This knowledge hopefully will lead to

reduced human power cost, time saving and laboratory expenses. These approaches,

which are in the nature of drug design on a rational basis, will become fundamental

parts of medicinal chemistry research. There are many reasons that have contributed

to the fast growth of in silico drug design such as:

(i) The advancement of the computer science which leads to the construction

of powerful and friendly used computers;

(ii) The development of statistical packages that can utilize databases

containing theoretical or experimental data and that can be subjected to

QSAR;

(iii) The development of new techniques in the experimental procedures for

characterizing proteins and biological targets (i.e. X-ray crystallography

and NMR spectroscopy);

(iv) The increase in the knowledge of the molecular basis of drug action.

Today, computer-assisted approaches are indispensable prerequisites to

support medicinal chemistry research.

5

1.1.2 Introduction to thienopyrimidines

Pyrimidine has always been a unique interesting heterocyclic moiety for the

medicinal chemists; an exhaustive research has been done on the pyrimidines that led

to the discovery and introduction of several drugs into the market.

From the standpoint of biological activity, fused heteroaromatic systems are often

of much greater interest than the constituent monocyclic compounds. The appearance

of qualitatively new properties of an annealated molecule, enlargement of the

possibility of varying pharmacophore groups in different positions of the molecule

and the ability of the latter to interact with a wider spectrum of receptors adopting

various conformations are apparently of crucial importance. In addition, the structure

of the molecule can be varied by annealing at different positions of individual

heterocyclic fragments.

Fused pyrimidines have also been attracted a considerable interest in medicinal

chemistry research due to their versatility and a broad bioactive potential. Thieno

pyrimidine is among those fused pyrimidines found to have a wide variety of

pharmacological and biological applications. Since last four decades research has

been focused on the design and synthesis of novel thienopyrimidines as medicinal

agents, a large number of reports have been documented on thienopyrimidines as they

found to exhibit a variety of biological activities such as antimicrobial, anti-

inflammatory, bronchodilatory activity, inhibition of Phospodiesterases, tyrosine

kinase and VEGFR kinase1-5

. It is evident that purine as an endogeneous scaffold

plays an important biochemical role in variety of regular physiological functions such

as respiration, inflammation, cell proliferation and so forth. As a bioisoster to purines,

thieno[2,3-d] pyrimidines were also found to exhibit numerous biological activities

probably due to the interaction with various physiological elements.

6

1.1.2.1 Chemistry of thienopyrimidine

Thienopyrimidine is a bicyclic heterocyclic compound wherein a five

membered thiophene ring is fused to a six membered heterocylic ring with two

nitrogen atoms. The fusion may occur in three different orientations that results in

three important types of thienopyrimidines namely; thieno[2,3-d]pyrimidine,

thieno[3,2-d]pyrimidine and thieno[3,4-d]pyrimidine. Most of the isomeric

thienopyrimidines occur as colored amorphous form, some exists as crystalline form.

1.1.2.2 Synthetic approaches to thienopyrimidines

Synthetic approaches for the construction of a number of thienopyrimidines are

well established. There exists three possible types of fusion of thiophene to

pyrimidines ring results in corresponding isomeric thienopyrimidines namely;

thieno[2,3-d]pyrimidines, thieno[3,4-d]pyrimidines and thieno[3,2-d]pyrimidines.

SN

N

N

N

N

N

S

S

1

2

3

45

6

4a

7

7a

1

2

3

45

6

7

4a

7a

1

2

3

45

6

7

4a

7a

(1) (2) (3)

The approaches to the synthesis of thienopyrimidines can be categorized into two

groups. One of this is synthesis of pyrimidines ring by intramolecular cyclization of

thiophene derivatives and another one is the construction of thiophene ring by the ring

closures of thiophene derivatives. Both the synthetic approaches are discussed below

by taking suitable examples.

1.1.2.2.1 Synthesis of thienopyrimidine by pyrimidine ring closure

In this approach, appropriately substituted amino thiophenes are used as the main

starting compounds for the preparation of thienopyrimidines. All the three types of

7

thienopyrimidines can be achieved from either 2-amino or 3-amino thiophenes under

similar reaction conditions and proceeds via same reaction sequence.

The pyrimidine ring closure in thienylurea is the most popular approaches to the

synthesis of thienopyrimidinones. This method was first described by Capuano et al1.,

in 1969, later number of reports have been documented on the synthesis of

thienopyrimidines by employing pyrimidine ring closure approach by slightly

modifying the reaction conditions.

Pyrimidine ring closure from substituted thienylurea occurs easily upon reaction

with an alkali, usually ethanolic solution of alkali (potassium tertiary butoxide) can be

used.

COX

NHCONHR

A

NH

NR

A

O

O

Scheme - 1

Similarly thioxothienopyrimidines can also be prepared from the corresponding

thienyltiourea as described by Ibrahim et al2.,

S

COOC2H5

NH2S

COOC2H5

NH SNH

NR

CNHR

O

S

S

RNCS EtOH-KOH

Scheme - 2

Synthesis of 2-alkylthio-4-oxo-thieno[3,2-d]pyrimidin-3-yl acetonitrile from

methyl 2-amino carboxylate thiophene by employing one-pot procedure3 following

pyrimidine ring closure.

8

S

NH2

COOCH3

CSCl2

S

NCS

COOCH3

NH2CH2CN

S

HN

COOCH3

HN

CH2CN

S

RX

N

N

S

O

SR

CH2CN

R = Methyl, Propyl, Butyl

Scheme - 3

Another similar procedure can be used for the synthesis of

thienopyrimidinedithiones from the 2-amino-3-cyano thiophene. Thiazine is formed

during the reaction as an important intermediate compound which upon recyclization

yields corresponding thieno pyrimidinedithione4.

S

CN

NH2S

NH

S

NH

S

CS2

R1

R2

R1

R2

SNH

NH

S

S

R1

R2

Scheme - 4

The annealated triazolylthienopyrimidnes can be prepared by pyrimidine ring

closure of 2-amino-3-triazolyl thiophene as described by Shishoo et al5., In the similar

manner angularly annealated triazolylthienopyrimidnethione can be prepared by

treating 2-amino 3-triazolyl thiophene with carbondisulfide under mild basic

conditions.

9

SNH

CNHRS

R1

R2

NH

NN

SN

R1

R2

N

NN

NHR

K2CO

3

MeI

Scheme - 5

SNH

R1

R2

N

NN

CS2

SNH2

R1

R2

NH

NN

KOH

S

Scheme - 6

1.1.2.2.2 Synthesis of thienopyrimidines by thiophene ring closure

As earlier, procedure for the construction of thienopyrimidines by employing the

thiophene ring closure approach used much more rarely than the previously described

pyrimidine ring closure method. Moreover, the synthesis of thienopyrimidines can be

achieved by taking a variety of substituted pyrimidines as starting compounds.

For example, 5-amino substituted thienopyrimidines (R1 = COOC2H5, SCH3, Ar;

R2 = SCH3, NR2; Z = COOC2H5, CONR2) are prepared from 5-cyano pyrimidine-6-

thione upon S-alkylation followed by cyclization with sodiumhydride6.

N

NH

CN

S

R1

R2

ClCH2ZN

NH

CN

S

R1

R2 Z

N

N

R1

R2S

NH2

ZNaH

Scheme - 7

10

Claisen-Schmidt reaction can also afford corresponding thienopyrimidines via

reaction of mercaptoacetic acid with 5-acyl-6-chloro pyrimidine or via the alkylation

of 5-acyl pyrimidine thiones with alpha halo carbonyl compound7.

N

NH

COR3

Cl

R1

R2

N

NH

COR3

S

R1

R2

N

NH

COR3

S

R1

R2 Z

HSCH2 Z

ClCH 2

Z

N

N

R1

R2S

R3

ZR1 = H, CH3; R2 = Ar; R3 = CH3

Z= COOH, COOC2H5, CONHR, COR, CN

Scheme - 8

1.1.2.3 Chemical properties of thienopyrimidines

To achieve directed synthesis of biologically active heterocyclic compounds,

knowledge of the chemical behavior of heterocyclic system is required. Like other

heterocyclic compounds thienopyrimidine also exhibit a variety of chemical

properties, however nucleophilic and electrophilic substitution reactions are important

and are discussed hereunder.

1.1.2.3.1 Nucleophilic substitution

i) Chlorination of thienopyrimidinones and thienopyrimidinediones

Thienopyrimidinones and thienopyrimidinediones can undergo nucleophilic

substitution in which the oxygen atom(s) replaced with chlorine atom. This reactions

11

proceeds on heating with a chlorinating reagent either POCl3 or SOCl2 and

accompanied by the formation of corresponding chlorinated thienopyrimidine8.

NH

N

A

R

O

POCl3

NH

N

A

R

Cl

Scheme - 9

Similarly, thienopyrimidine containing thioxo group undergo similar

transformations9

upon heating with POCl3 or SOCl2.

NH

N

S

R1

R2

S

N

N

S

R1

R2

Cl

POCl3

PhNMe2

Scheme - 10

ii) Formation of Amino, alkylthio, alkyloxy and thioxo thienopyrimidines

from chlorinated thienopyrimidines

Moreover, the nucleophilic substitution occurs more easily in

chlorothienopyrimidines than the other. The chlorine atom can be replaced with any

other nucleophillic residue like amine, thiolates, thiourea and alkoxy group result in

formation of corresponding substituted thienopyrimidines10-13

.

12

NH

N

A

Cl

R1

NH

N

A

NR22

R1

NH

N

SR2

R1NH

NH

A

S

R1

A

NH

N

A

OR2

R1

R2SNa

R2

2NHR2ONa

(NH2)2CS

Scheme - 11

In general halogenated thienopyrimidines can exchange halogen atom with other

halogen atom of nucleophillic reagent14

.

SN

N

Cl

SN

N

I

NaI

Scheme - 12

Methylthio substituted thienopyrimidines can undergo nucleophilic substitution

with a variety of amines15

.

N

N

R1

SMe

A

N

N

R1

NR22

AR

22 NH

Scheme - 13

Intramolecular condensation occurs in thienopyrimidinone and thioxo

thienopyrimidines involves primary amino group and thioxo or oxo group of the same

thienopyrimidine. This condensation results in the formation of another five or six

membered fused heterocyclic ring system16

.

13

N

N(CH2)nCl

O

R

A

N

N

Cl

R

A

N

N(CH2)nNH2

X

R

A

i

ii

i = NH2(CH2)nNH2

ii = NH4OAc

X = O, S

N

N

N

R

A

(CH2)n

Scheme - 14

Triazolylthienopyrimidine can undergo nucleophilic substitution with a variety of

nucleophile such as primary amines and thiols can afford corresponding substituted

thienopyrimidines17

.

SN

N

N

R

N

N

HNu

SN

N

Nu

R

Scheme - 15

1.1.2.3.2 Electrophillic substitution

Thieno[2,3-d]pyrimidines and thieno[3,4-d]pyrimidines can undergo electrophilic

substitution reactions in presence of an excess of electrophilic reagents. Electrophilic

substitution such as chlorination, bromination, Vilsmeier formylation and nitrations

are demonstrated18-20

. Usually the substitutions can occur at position C5 in thieno[2,3-

d]pyrimidines and at position C5 and C7 in thieno[3,4-d]pyrimidines. In case of

thieno [3,2-d]pyrimidines substitution occurs only at C7.

14

Thienopyrimidinones and thienopyrimidinediones undergo N-alkylation in

presence of K2CO3 or NaH as the base under conditions of phase transfer catalyst21

.

NH

NH

O

A

O

Alk1Hal

NH

NAlk1

O

A

O

Alk2Hal

N

Alk2

NAlk1

O

A

O

Scheme - 16

Similarly the thienopyrimidinediones can also undergo Michael reaction with

ethylacrylate and acrylonitrile22

.

NH

NR

O

A

O N

NR

O

A

O

Z

CH2=CH-Z

Z = CN, COOC2H5

Scheme - 17

Intramolecular cyclization of allythiothienopyrimidine is an example for

electrophilic substitution. This occurs in presence of any cyclizing agent either

sulfuric acid or alkyhalide which gives linearly annealated and angular isomers of

thiazolo thienopyrimidines respectively23

.

15

SN

NH

O

SCH2CH2=CH2

R1

R2

SN

N

OR1

R2

SN

N

OR1

R2

S

Me

S

HalH2C

Hal

2

H 2SO

4

Scheme – 18

1.1.2.4. Biological activities of thienopyrimidines

Thienopyrimidine derivatives are characterized by a very broad spectrum of

biological activities, which include, antibacterial, antimicrobial, antiviral, antiallergic,

antihypertensive, antiatherosclerotic, antidiabetic, analgetic, and antiinflammatory

activities, antidepressant and depressant, antihistaminic, spasmolytic activities.

Many thienopyrimidine derivatives have been covered by a number of patents

worldwide for their interesting biological and pharmacological activities such as

phosphodiesterase inhibitors, receptor antagonists, antitumor, radioprotective

activities, immunomodulators, prophylaxis and therapy of cerebral ischemia, malaria,

alzheimer's disease, parkinson's disease

Apart from their therapeutic applications, some thienopyrimidine are also used as

fungicides, herbicides and insecticides in agriculture.

16

1.2 Literature review

Thienopyrimidines and its derivatives have been generally associated with various

biological and pharmacological properties. The synthesis of a large number of thieno

pyrimidines derivatives have been reported to obtain potentially active compounds.

Many such compounds have been found to be promising. A few even have clinical

applications. An exhaustive literature search has been done on the synthesis,

biological and pharmacological activities of thieno pyrimidines. Since there have

been numerous reports, some of the interesting reports are presented hereunder.

Salahuddin et al24

., described the synthesis of 2-bromo-1-[4-(6, 7-dihydro-5H-

cyclopenta[4, 5]thieno[2, 3-d]pyrimidin-4-yl-amino) phenyl] ethanone and 2-bromo-

1-[4-(6, 7-dihydro-5H-cyclopenta[4, 5]thieno[2, 3-d] pyrimidin-4-yl-amino) phenyl]

ethanone derivatives. Synthesized compounds were screened for antibacterial activity

by using disc diffusion technique against a variety of microorganisms, including gram

positive bacteria B.subtilis, B.pumilis and the gramnegative Bacteria S. aureus, E coli.

Compounds (4) were found to be potent antibacterial agents.

N

N

S

HN N

N

S

R

(4)

17

N

N

S

HN

CH2CH2NH

NH

N

(5)

N

N

S

HN

CH2CNH

F3COC

Cl

(6)

Nermin et al25

., reported the synthesis of indenothienopyrimidines and their

antimicrobial properties. 2-substituted [1,2,4] triazolo[1,5,-]-9H-indeno[1’,2’:4,5]

thieno[3,2-e]pyrimidines derivatives (7, 8 and 9) and 9H-indeno[1’,2’,:4,5]thieno

[3,2-e]tetrazolo[1,5-c]pyrimidines were prepared from 9H-indeno[1’,2’:4,5]thieno

[2,3-d]pyrimidin-4-ylhydrazine. He also described about the synthesis of

Nsubstituted-9-H-indeno [1’,2’: 4,5]thieno[2,3-d]pyrimidin-4-yl) amine derivatives

and thieno[2,3-d] pyrimidin-4-yl-isothiourea derivatives. The antibacterial activity of

synthesized compounds tested against E. coli (Gram -ve bacteria), B. subtilis (Gram

+ve bacteria), Staphylococcus and the antifungal activity of the compounds was tested

against C. albicans.

18

S N

N

N

N

R

(7)

S N

N

NN

CH3

(8)

S N

N

N

NN

(9)

Solimn et al26

., reported the synthesis and antimicrobial activities of

tetrahydrobenzothieno[2,3-d]pyrimidine and tetrahydrobenzothieno[3,2-e] [1,2,4]

triazolo [4,3-c] pyrimidine Derivatives. New series of tetrahydrobenzothieno[2,3-

d]pyrimidine and tetrahydrobenzo thienotriazolopyrimidine derivatives have been

synthesized namely 4-(substituted amino)-5,6,7,8-tetrahydro[1]benzothieno[2,3-

d]pyrimidines, 4-(3,5-disubstituted pyrazol-1-yl)-5,6,7,8-tetrahydro-

[1]benzothieno[2,3-d]pyrimidines, N-(phenyl or 4-substituted phenyl)-2-(8,9,10,11-

tetrahydro[1]benzothieno[3,2-e][1,2,4]-triazolo[4,3-c]pyrimidin-3-ylsulfanyl)

acetamides and 3-substituted-8,9,10,11-tetrahydro[1]benzothieno[3,2-

e][1,2,4]triazolo[4,3-c]pyrimidines. The antibacterial and antifungal investigations

showed that compounds 10, 11 and 12 were active.

19

N

N

S

NN

R

R1

N

N

S

N

N

R

(10) (11)

N

N

S

N

N

S

O

HN

(12)

Asma et al27

., synthesized new tetrahydrobenzo[4,5]thieno[2,3-d]Pyrimidine

derivatives and Schiff bases derived from 2-aminotetrahydro benzothiophenes and

heteroarylcarboxaldehydes. The antitumor and antimicrobial activities of these

synthesized derivatives have also been reported the antitumor activity has been

carried out by using two methods namely; cell culture and assays for growth,

apoptosis and transcriptional activation of the GADD45 Reporter: and growth

suppression of ovarian cancer xenografts in nude mice by nude mouse studies of

OVCAR3 tumor xenografts.

N

NH

S

O

O

O

CH3

R1

R2

R3

(13)

20

Abdel haleem et al28

., reported the synthesis and antimicrobial activity of 2-

substituted and unsubstituted-4-[(4-substituted anilino)]tetrahydrobenzo thieno

pyrimidinederivatives (14).

(14)

Konnos et al29

., synthesized and reported a series of 4-alkylamino- and 4-

arylaminothieno[2,3-d]pyrimidines (15, 16) by the nucleophilic substitution of 4-

chlorothieno[2,3-d]pyrimidines with various amines. These compounds were

evaluated for antifungal activity against Piricularia oryzae.

SN

N

HN

SN

N

HNR

R

R = p-OCH3C6H4,-CH2CH2CH2

(15) (16)

S

N

N

R

HN

NN

R3

R1

R = H,CH3: R1 = H,C6H5,2,4--NO2C6H3

R3 = o-(OH)C6H4, p-Br.C6H4, p-(NO2)C6H4

21

Schmidt et al30

., reported 2,4-diamino-6-benzyl-5-methyl thieno[2,3-d]

pyrimidine (17, 18) and thienopyrano[2,3-d]pyrimidine as possible antibacterial and

antimalarial agents.

SN

N

H2N

NH2

S

S

H3C

H2CN

N

H2N

NH2

(17) (18)

Raghuprasad et al31

., synthesized some novel 5-substituted- 1,2,4-triazolo[4,3-

c]8,9,10-trihydrocyclopenta/8,9,10,11,12-penta hydrocyclohepta[6] thieno

[3,2-e] pyrimidin-3-thiones (19) and were tested for antimicrobial activity by Kirby

Bauer’s method. He reported that all the compounds showed antibacterial activity

comparable with standard.

SN

N

R3

R1

R2

NN

S

H

R1 = (CH2)3,

R2 = CH3,C6H5, Pyridyl, p-ClC6H5

(19)

Bhuiyan et al32

., synthesized some new thienopyrimidine derivatives and were

screened for antibacterial activity against pathogenic organism by disc diffusion

method. He reported that 4(3,5dimethylpyrazolyl)5,6,7,8-tetrhydrobenzothieno[2,3-

d]pyrimidine (20) possess high antibacterial activity.

22

S

N

N

N

N

H3C

CH3

(20)

Isaac and his co-workers33

., reported the synthesis of series of 6-aralkyl

substituted 2,4-diaminothieno[2,3-d]pyrimidines in which the 6-aryl group is

separated from the thieno[2,3-d]pyrimidine ring by two to five methylene bridge were

synthesized and studied as potential inhibitors of dihydrofolate reductase from

Toxoplasma gondii, Pneumocystis carinii, Mycobacterium avium and rat liver.

Compounds (21) in which the thieno[2,3-d]pyrimidines ring is separated from the 6-

aryl substituent by three methylene groups were the most potent inhibitors of the

series.

N

NS

NH2

(CH2)n

CH3

H2N

Ar

n = 2-5: Ar = Phenyl/1-Napthyl/2-Napthyl

(21)

EI-Sherbeny et al34

., reported some thienopyrimidine derivatives (22, 23) as

anti microbial and antiviral agents.

23

SN

N

O

n(H2C)

N

N

R

CH3

R = C6H5/CH3/p-ClC6H4

SN

N

NH

O

n(H2C)

R

NH2

(22) (23)

Andre Rosowsky and his co-workers35

synthesized and reported 2,4-

diaminothieno[2,3-d]pyrimidine analogues (24, 25) as potential inhibitors of

dihydrofolate reductase(DHFR) of Pneumocystis carinii and Toxoplasma gondii.

S N

N

NH2

H3CNH2

n(H2C)

Z S N

N

NH2

NH2n(H2C)

Z

(24) (25)

n = 0,1,2,3

Z = 21,5

1-(OMe)2/,3

1,4

1,5

1-(OMe)3

Showa Denko and his co-workers36

reported the synthesis and biological

activity of some thienopyrimidines derivatives (26) as possible antifungal agents.

SN

N

R1

OH3C

H3C

O R

R = H,Alkyl: R1 = C2H5

(26)

Devani et al37

., reported the 2-mercapto thieno[2,3-d]pyrimidine 4-one (27) as

possible antimicrobial agent.

24

S N

N

SH

OR1

R2

OR3

R1 = Ph, 4-ClC6H4, 4-MeC6H4

R2 = H,CH3: R3 = Alkyl

(27)

Ismail et al38

., synthesized a series of tetramethylenethieno[2,3-d]pyrimidine

derivatives and tested for antimicrobial properties. All the synthesized compounds

were found to exhibit in vitro antibacterial and/or antifungal activity. The highest

activity was elicited by 4-benzolhydrazino-5,6-tetramethylenethieno[2,3-d]pyrimidine

(28).

SN

N

R1

OH3C

H3C

O R

R = H,Alkyl: R1 = C2H5

(28)

El-Gazzar et al39

., synthesized 4-amino thieno[2,3-d]pyrimidine derivatives by

the reaction of 5-Methyl-6-phenyl-2-thioxothieno[2,3-d]pyrimidone derivatives with

hydrazonoyl chloride derivatives to afford triazolothienopyrimidones and acetone-1-

(2-amino-5-isopropyl-thiophene-3-carbonitrile) reacted with functional and

bifunctional groups to yield the corresponding compounds (29, 30) and were

evaluated for their anti-inflammatory, analgesic and ulcerogenic activity.

25

N

N

S

OH3C

C6H5

N

N

Ar

R

S

N

NH

NH2H3COCH2C

H3C

H3C R

(29) (30)

Hefeez et al40

., reported the synthesis of 2-thioxo-N3-amino thieno[2,3-d]

pyrimidines and 5-ethyl-2-amino-3-pyrazolyl-4-methyl thiophenecarboxylate from

3,5-diethyl-2-amino-4-methyl thiophenecaboxylate and evaluated as anti-

inflammatory, analgesic and ulcerogenic activities. Among the compounds studied,

compounds (31) containing the substituted hydrazide at C-3 position showed more

potent anti-inflammatory and analgesic activities than the standard drug

(Indomethacin and Aspirin), without producing ulcerogenity. Such compounds were

also found to have moderate to excellent antimicrobial activity.

SNH

N

S

H3C

C2H5OOC

O

NH2

(31)

Rashmi et al41

., reported the synthesis of 4,5-substituted thieno[2,3-

d]pyrimidines and evaluated for antioxidant and anti-inflammatory activities. The 4-

hydroxy thieno[2,3-d]pyrimidine existed as tautomer was treated with potassium

carbonate in dry acetone to form potassium salt to make the compound to exist in

lactim form (lactam-lactim tautomerism) which was then allowed to react with

ethylchloroacetate to form 4,5-substituted thieno[2,3-d]pyrimidines. Among tested

compounds only compound 32 was found to be potent antioxidant. In in vitro anti-

inflammatory studies the compounds(32) found to potent anti-inflammatory agent

26

bearing substitutions R = -C6H4-4-OCH3, -C6H4-3,4,5- OCH3, -C6H4-3- OCH3-4-OH, -

C6H4-4-OH.

N

N

S

O

HN

N R

O

(32)

Algarsamy et al42

., reported the synthesis of 2-mercapto-3-(substituted

amino)-5,6,7,8-tetrahydro-3H-benzo[4,5] thieno[2,3-d]pyrimidin-4-ones by reacting

3-Amino-2-mercapto-5,6,7,8- tetrahydro-3H-benzo[4,5]thieno[2,3-d]pyrimidin-4-one

with different aldehydes and ketones; The title compounds were investigated for

analgesic, anti-inflammatory and ulcerogenic index activities. While the test

compounds exhibited significant activity, compounds 33a, 33b and 33c exhibited

highly potent analgesic activity. The compound 33c exhibited highest anti-

inflammatory activity when compared to the reference standard diclofenac sodium.

On the other hand test compounds exhibited mild ulcerogenic potential when

compared to Aspirin.

N

N

S

O

SH

N

R1

R2

a C

CH3

C2H5

b C

H

CH

CH

c C

CH3

C6H5

C6H5

(33)

27

Ashalatha et al43

., reported the synthesis of 2-(substituted

phenyl)/alkyl[1,3,4]thiadiazolo[2,3-b]-6,7,8,9-tetrahydrobenzo(b)thieno[3,2-

e]pyrimidin-5(4H)-ones, six new 3-amino-2-[(2-oxo-2-(aryl)ethyl)thio]-5,6,7,8 tetra

hydro[1] benzo thieno[2,3-d]pyrimidin-4(3H)-ones, one 2

mercapto[1,3,4]thiadiazolo[2,3-b]-6,7,8,9-tetrahydro benzo(b)thieno[3,2-e] pyrimidin

5(4H)-one and one 2-chloromethyl [1,3,4]thiadiazolo[2,3-b]-6,7,8,9-

tetrahydrobenzo(b)-thieno[3,2-e] pyrimidin- 5(4H) -one from 3-amino-2-mercapto-

5,6,7,8- tetrahydro[1]benzothieno[2,3-d] pyrimidin-4(3H)-one. Synthesized

compounds were screened for anti-inflammatory and CNS depressant activities.

Some of the compounds 34 and 35 exhibited promising Pharmacological activities.

N

N

S

O

S

N

R

N

N

S

O

S

NH2

Ar

O

(34) (35)

N

N

S

O

S

HN

S

N

N

S

O

S

N

CH2Cl

(36) (37)

Algarsamy et al44

., reported the synthesis anti-inflammatory, ulcerogenic index

analgesic and antibacterial activities of novel 2-methylthio-3-substituted- 5,6,7,8-

tetrahydrobenzo (b) thieno[2,3-d]pyrimidin-4(3H)-ones. The title compounds were

synthesized by nucleophilic substitution of (2-methylthio-4-oxo-3H-5,6,7,8-

tetrahydrobenzo (b) thieno[2,3-d]pyrimidin-3-yl) dithiocarbamic acid methylester

with different amines. Compounds exhibited more potent analgesic activity, whereas

compound 38 showed more anti-inflammatory activity than the standard compound.

28

N

N

S

O

S

CH3

HN C

S

N

R1

R2

(38)

Abu-Hashem et al45

., reported the synthesis of novel

thiophenecarbohydrazide, thienopyrazole and thienopyrimidine derivatives from 2-

amino-5-acetyl-4-methyl-thiophene-3-carboxylic acid ethyl ester and 5-acetyl-2-

amino-4-methylthiophene-3-carbohydrazide. The synthesized compounds were

evaluated for antioxidant activity by employing ABTS method and Bleomycin-

dependent DNA damage. Compounds were also evaluated for their antitumor activity

by employing Ehrlich ascites in vitro assay. Compounds 39, 40 showed potent

antioxidant activity and 41 showed potent antitumor activity followed by compounds

39, 40, 41 and 42.

SNH

NR

O

S

H3C

H3COC

SNH

N

O

S

R

R'

NH2

(39) (40)

S

N

N

O

CH3

H3C

H3COC

NH2

S

COOC2H5

NH

H3C

H3COCC

S

NH2

(41) (42)

29

Takao Horiuchi et al46

., described about the synthesis of new analogues of

thieno[2,3-d]pyrimidin-4-yl hydrazones from the classical condensation of thieno[2,3-

d]pyrimidin-4-hydrazines with 2-thiophenecarboxaldehyde. Intermediates compounds

thieno[2,3-d]pyrimidin-4-hydrazines were prepared by chlorinating the carbonyl

group at position 4 of thieno pyrimidines with phosphorusoxychloride, followed by

treating with hydrazine monohydrate. Formed compounds were evaluated for

antitumor activity and several 2-pyrdinecarboxaldehyde [6-(tert-butyl)thieno[2,3-

d]pyrimidine-4-yl]- hydrazones were shown to be potent, selective inhibitors of

CDK4 with improved physical profiles. In addition, these compounds were found to

have antiproliferative activities and act as cytotoxic agents by preventing cell

progression. Moreover, compound 43 was found to be efficacious in xenograft models

of human colon carcinoma.

N

N

S

R1

R2

HN

N

S

(43)

Edgar R. Wood et al47

., synthesized some analogs of 6-ethynylthieno[3,2-d]

(44) and 6-ethynylthieno[2,3-d]pyrimidin-4-anilines (45) and were tested for EGFR,

ErbB-2 and ErbB-4 tyrosine kinase inhibition. Analogs of the series 6-

ethynylthieno[3,2-d] pyrimidin-4-anilines were found to have potent tyrosoine kinase

inhibition when compared to other series.

30

S

N

N

HN

CCR

Cl

O

F

(44)

SN

N

HN

CCR

Cl

O

F

(45)

H2N

H

NH

N

N

N

H

H

R =, ,

Adams and jerry Leroy48

patented 4-amino-2,3-disubstitutedthieno[2,3-

d]pyrimidines derivatives, which are useful as TIE-2 and/or VEGFR-2 inhibitors. The

invention includes methods of making such furo and thienopyrimidine derivatives as

well as methods of using the same in the treatment of hyperproliferative diseases.

Michael J. Munchhof and his co-worker49

., reported the synthesis of novel

classes of thienopyrimidines (46, R1= 5-indolyl, R2= -C6H5) and thienopyridines

which have been identified as potent inhibitors of VEGFR-2 kinase.

X=CH or N

S

N

X

NHR1

R2

(46)

31

Jordis et al50

., prepared thirteen 4-aminothienopyrimidines (47,48) [R = Me,

R1 = H, Me; R2 = H, SMe; R3 = Me(CH2)4, H, cyclopentyl, PhCH2, etc.; RR1 =

(CH2)4; R2 = H, SMe, R3 = Me(CH2)4 etc.] and were tested for anti-cytokinin activity

using tobacco callus assay .

S

R1

R2

N

N

NHR3

SCH3S

R1

R2

N

N

SCH3

SCH3

(47) (48)

Stole51

patented 4-amino-5,6-substituted thiopheno[2,3-d]pyrimidines (49) as

phosphodiesterase enzyme VII (PDE7) inhibitor for the treatment and prevention of

asthama, osteoporosis and osteopenia.

S

YN

N

HN

R1

N R2

R3

R4

(CH2)n

R

(49)

Raghuprasad et al52

., reported the synthesis of 4-(2-hydroxy ethylamino)

thienopyrimidines (50) and imidazolothienopyrimidines (51) as possible

bronchodilatory agents in the treatment of asthma.

32

S

R1

R2

N

N

NHCH2CH2OH

NH2

S

R1

R2

N

N

NH2

N

(50) (51)

Crespo et al53

., designed a common pharmacophore for compounds

structurally related to nitraquazone. Using this pharmacophore, new structures have

been designed, synthesized, and evaluated for their inhibitory potencies against cyclic

adenosine 5'-monophosphate (cAMP) specific phosphodiesterase (PDE 4). From this

group 2-butyl-4-cyclohexylaminothieno[3,2-d]pyrimidine (52) has an interesting

profile, with an important improvement in PDE 4 inhibition.

N

N

S

NH

CH2CH2CH2CH3

(52)

Hosni et al54

., reported the synthesis of novel class of thieno[2,3-d]pyrimidinones

and their condensed products as possible Molluscicidal and Larvicidal agents. The

molluscicidal activity was screened against Biomphalaria alexandrina snails. The

larvicidal activity was screened against the free larval stages of Schistosoma mansoni;

cercariae and miracidia. Compound 53 was found to be highly active with LC90 at

7ppm, whereas compounds 53, 54, 55 and 56 exhibited 90% cercarial mortality at

10ppm also exhibited miracidal activity at same concentrations.

33

N

N

S

RO

COOC2H5

CH2Cl N

NH

S

RO

CH2NH2NH2

(53) (54)

N

NH

S

RO

CH2

N

N

O

CH3

N

NH

S

RO

C

COOC2H5

COOC2H5

CN

(55) (56)

1.3. Scope and objectives of the present work

Recent observations and an exhaustive literature survey on thieno[2, 3-

d]pyrimidine molecule and derivatives describe the importance of thieno[2, 3-

d]pyrimidines as a biological and pharmacological agents. These molecules were

found to possess a wide range of acceptable biological activities such as

antimicrobial, anti inflammatory, bronchodilatory activity, inhibition of

Phospodiesterases, tyrosine kinase and VEGFR kinase as discussed in the introduction

part. The present medicinal chemistry research focusing on the thieno[2, 3-d]

pyrimidine as synthon for the design and development of potential lead molecules as

this scaffold has structural similarity with many endogenous biological molecules.

Comparatively, less research has been documented in the biological standpoint, only

few patents are available on the derivatives of thieno[2,3-d]pyrimidine. It is evident

from the literature that thieno[2,3-d]pyrimidine is yet to be explored in both synthetic

and biological aspects.

34

However, no reports have been documented on the synthesis of thieno[2,3-

d]pyrimidine with Schiff’s base as a substituent at the C4 position along with varied

substitutions at position C2, C5 and C6. This observations initiated present

investigation to synthesize new hitherto unreported thieno[2,3-d]pyrimidines and

screening for possible biological activities.