One pot efficient diversity oriented synthesis of polyfunctional styryl thiazolopyrimidines and their bio-evaluation as antimalarial and anti-HIV agents

Article abstract of DOI:10.1016/j.ejmech.2012.07.018

An efficient one pot synthesis of a series of pluripotent (E)-1-(3-methyl-5-aryl-7-styryl-5H-thiazolo[3,2-a]pyrimidin-6-yl) -3-arylprop-2-en-1-ones is reported. It involves reaction of 5-acetyl-6-methyl-4-aryl-dihydropyrimidine-2-thiones, propargyl bromide and aromatic aldehydes in presence of ethanolic KOH. The newly synthesized compounds were evaluated for antimalarial activity against Plasmodium falciparum and as HIV-RT inhibitors. Most of the compound displayed potent antimalarial activity with IC₅₀ < 2 μg/mL. Compounds 6, 11 and 20 showed better activity against P. falciparum K1 strains in comparison to standard drug chloroquine. Compounds 6, 11, and 16 exhibited 73.44, 66.92, and 70.81% HIV-RT inhibition at 100 μg/mL.

Full text of DOI:10.1016/j.ejmech.2012.07.018

European Journal of Medicinal Chemistry 55 (2012) 195e204
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
One pot efficient diversity oriented synthesis of polyfunctional styryl
thiazolopyrimidines and their bio-evaluation as antimalarial and anti-HIV agents
Seerat Fatima a, Anindra Sharma a, Reshu Saxena b, Rajkamal Tripathi b, Sanjeev K. Shukla c,
,
Swaroop Kumar Pandey d, Renu Tripathi d, Rama P. Tripathi a
*
a Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, Lucknow, India
b Toxicology Division, CSIR-Central Drug Research Institute, Lucknow, India
c NMR Centre, SAIF Division, CSIR-Central Drug Research Institute, Lucknow, India
d Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient one pot synthesis of a series of pluripotent (E)-1-(3-methyl-5-aryl-7-styryl-5H-thiazolo[3,2-
a]pyrimidin-6-yl)-3-arylprop-2-en-1-ones is reported. It involves reaction of 5-acetyl-6-methyl-4-aryl-
dihydropyrimidine-2-thiones, propargyl bromide and aromatic aldehydes in presence of ethanolic KOH.
The newly synthesized compounds were evaluated for antimalarial activity against Plasmodium falci-
parum and as HIV-RT inhibitors. Most of the compound displayed potent antimalarial activity with
Received 30 March 2012
Received in revised form
11 July 2012
Accepted 14 July 2012
Available online 23 July 2012
IC50 < 2
comparison to standard drug chloroquine. Compounds 6, 11, and 16 exhibited 73.44, 66.92, and 70.81%
HIV-RT inhibition at 100 g/mL.
mg/mL. Compounds 6, 11 and 20 showed better activity against P. falciparum K1 strains in
Keywords:
Thiazolopyrimidine
Anti-HIV agents
m
Ó 2012 Elsevier Masson SAS. All rights reserved.
Antimalarial agents
P. falciparum, Styryl thiazolopyrimidine
1. Introduction
skeleton, the thienopyrimidines and thiazolopyrimidines have
received considerable attention recently due to their wide appli-
cation in medicinal chemistry. A diverse range of pharmacological
activities such as anti-HIV [17], antibacterial [18], anti-
inflammatory [19,20], antihypertensive [20], antimicrobial [21],
antioxidant, antitumor [22], anti-HSV-1 [23] and herbicidal [24] are
associated with these structural prototypes. They are also known to
inhibit the CDC25BP phosphates [25], and IspF (2-methylerythritol
2,4-cyclodiphosphate synthase) proteins of Mycobacterium tuber-
culosis, Plasmodium falciparum, and Arabidopsis thaliana [26]. Styryl
compounds both of synthetic and natural origin have tremendous
potential both in organic synthesis as synthon and in medicinal
chemistry as chemotherapeutic agents. Styryl heterocycles are also
known as anti-HIV agents [27], while the styryl ketones (chal-
cones), such as Licochalcone A (A), 5-prenylbutein (B), and
compound C are well known for their antimalarial activities
[28e30] (Fig. 1).
In the last two decades CeC bond formation has been increas-
ingly achieved by the addition of carbon centered radicals to
carbonecarbon multiple bonds. It is known that the addition of
heterosubstituted radicals to styryl sulfimides [1] and styryl triflone
[2] results in styryl heterocycles. Traditionally, styryl heterocycles
are prepared by HornereWadswortheEmmons reaction of the
alkyl(diphenyl)phosphine oxide with a carbonyl compounds [3].
The aldol reactions of 2-methyl azaarenes with aromatic aldehydes
in the presence of strong acid or base [4e8], have also been
exploited to get alkenyl azaarenes with only low E/Z selectivity.
Very recently a catalyst free benzylic CeH bond olefination of
azaarenes with N-sulphonyl aldimines have been reported to afford
E-alkenyl azaarenes stereoselectively involving addition elimina-
tion reactions [9]. The alkenyl azaarenes, in general, have been used
as antagonist, antiproliferative, antiviral, and antimicrobial agents
and also for other important biological activities [10e16]. The
bicyclic heterocycles, with condensed thiazole and pyrimidine
Currently we have been involved in design and development of
new chemotherapeutic agents using many heterocyclic and non-
heterocyclic scaffolds [31e36]. In view of the above we were
prompted to synthesise hybrid molecules with thiazolopyrimidine,
enone and styryl moieties and evaluate their biological activities. In
this context we have developed an efficient one pot protocol for the
* Corresponding author. Tel.: þ91 0522 2612411; fax: þ91 522 2623405/
2623938/2629504.
E-mail addresses: rpt.cdri@gmail.com, rp_tripathi@cdri.res.in (R.P. Tripathi).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.07.018

196
S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
OH
OH
OH
O
OH
HO
HO
O
OH
O
O
O
µ
C; IC50 = 3.36
M
µ
B; IC50 = 10.3
M
µ
A; IC50 = 1.8
M
Fig. 1. Naturally occurring chalcones having antimalarial activity.
synthesis thiazolopyrimidines with enone and styryl functionalities
(Fig. 2) and evaluate their antimalarial and HIV-RT inhibitory
activities in the first instance.
then reacted with benzaldehyde (2.1 equiv.) in presence of KOH
(2.5 equiv.) in ethanol to give the required compound 3 in 75% yield.
The method II consists in reaction of dihydropyrimidine-2-thione
1a (1.0 equiv.) with propargyl bromide (1.0 equiv.) and benzalde-
hyde (2.1 equiv.) in presence of KOH (5.0 equiv.) in ethanol to give
the required compound 3 in 60% yield. The method III involves
a reaction of dihydropyrimidine-2-thione 1a (1.0 equiv.) with
propargyl bromide (1.0 equiv.) in presence of KOH (5.0 equiv.) in
ethanol at 30 ꢀC to give the intermediate 2a within 5 min, followed
by addition of benzaldehyde (2.1 equiv.) and reaction was shifted
now to oil bath at 80 ꢀC to give the required product 3 in 70% yield.
Thus method III proved to be most efficient as the isolation of
intermediate formed during reaction is not required. This method
was adopted as a general method for the synthesis of other
compounds of the series.
Similarly condensation of different dihydropyrimidine-2-
thiones (1ae1d) prepared earlier [34] with one equivalent of
propargyl bromide and two equivalents of selected aromatic alde-
hydes by method III, led to the formation of respective styryl
thiazolopyrimidines 4e25 in very good yields (Scheme 1).
All the synthesized compounds were fully characterized by their
IR, ESI-MS, NMR and elemental analyses (experimental section). In
IR spectra the compounds in general, displayed absorption bands at
around 1630 and 2932 cmꢁ1for the carbonyl and CH-stretching
frequencies. All the compounds in MS spectra showed [M þ H]þ
corresponding to their molecular formulae. In NMR (1H and 13C)
spectral data of the compounds all the proton and carbon signals
2. Results and discussion
2.1. Chemistry
The retro synthesis of targeted styryl thiazolopyrimidines is
shown in Fig. 3. 5-Acetyl-6-methyl-4-phenyl-dihydropyrimidine-
2-thiones [37], obtained through Biginelli reaction of acetyl
acetone, thiourea and aromatic aldehyde, on reaction with prop-
argyl bromide under basic condition may lead to respective thia-
zolopyrimidines via allene mediated cycloaddition as recently
reported [38]. The latter on reaction with two equivalents of
aromatic aldehydes will give rise to the required thiazolopyr-
imidines with styryl and cinnamoyl moieties.
To optimize the reaction condition for the synthesis of targeted
compounds, we have chosen a model reaction of 5-acetyl-6-
methyl-4-phenyl-dihydropyrimidine-2-thione (1a) with propargyl
bromide and benzaldehyde under basic condition. The reaction was
carried out under three different conditions and the results are
summarized in Fig. 4. In method I, dihydropyrimidinethione 1a
(1.0 equiv.) was reacted with propargyl bromide (1.0 equiv.) in
ethanol in presence of NaOEt at 80 ꢀC to give the thiazolopyr-
imidine (2a), which was isolated, characterised and reported earlier
by our group [38]. The intermediate compound 2a (1.0 equiv.) was
CH3
N
N
S
heterocycle stilbene
O
CH3
N
S
N
O
CH3
CH3
N
N
S
N
heterocycle chalcone
Targeted molecule
S
N
Thiazolopyrimidine
Fig. 2. Targeted hybrid thiazolopyrimidines with heterocycle chalcone, thiazolopyrimidine and heterocycle stilbene moieties.

S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
197
O
CH3
CHO
O
CH3
O
N
Br
H3C
N
+
NH
+
S
N
S
H3C
N
N
H
S
Biginelli reaction
O
H3C
H3C
CHO
S
O
H2N
NH2
Fig. 3. Retro synthesis of targeted styryl thiazolopyrimidines.
were observed at their usual chemical shift. Other compounds of
the series follow the same pattern. The chemical shift assignments
in one of the prototype compound 21 was carried out using
correlation spectroscopy (COSY), hetero nuclear single quantum
coherence spectroscopy (HSQC), hetero nuclear multiple bond
correlation spectroscopy (HMBC) and nuclear over hauser spec-
troscopy (NOESY). All the important correlations are given in Fig. 5.
It was observed that the two olefenic protons (H-30 and H-200)
appeared as doublet at 7.89 and 8.05 ppm with coupling constant
3
3
0
0
00
00
JH3 eH2 ¼ 15.62 and JH2 eH1 ¼15.50 respectively, which suggest
an E geometry of the olefinic bonds. The protons of CH3 show nOe
correlation with H2, H5 and Ar1-H2,6; whereas H-5 is showing nOe
correlation with Ar1-H2,6 and it led us to assign the chemical shift
values of H5 and H2 protons. The signals for H100 and H20 show nOe
Method I: Two Pots
O
CH3
O
O
CH3
Br
C6H5CHO
N
H3C
H3C
NH
N
S
C2H5ONa/ethanol
80°C
KOH/ethanol
rt
N
S
N
H
S
N
1a
3
2a
(75%)
Method II: One pot
O
CH3
O
CHO
N
KOH/ethanol
80 °C
Br
+
+
S
H3C
H3C
NH
N
N
H
S
3(60%)
1a
Method III: One pot two steps in situ
O
CH3
O
(i) propargyl bromide /
N
KOH/ethanol, 5min, 30°C
H3C
H3C
NH
S
N
C6H5CHO, 80 °C
(ii)
N
H
S
3
(70%)
1a
Fig. 4. Synthesis of the compound 3 with the three different methods.

198
S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
R
R
O
O
Br
KOH
NH
+
Ar
N
+ ArCHO
ethanol, rt - 80 °C
S
S
N
H
N
Ar
1a
- R = H
3-25
1b
- R = 4-OMe
1c- R = 3,4,5-tri OMe
1d
- R = 4=Cl
Scheme 1. Synthesis of (E)-1-(3-methyl-5-aryl-7-styryl-5H-thiazolo[3,2-a]pyrimidin-6-yl)-3-arylprop-2-en-1-one) derivatives (3e25).
Table 1
correlation with Ar3-H6 and Ar2-H6 respectively and nOe peak
between H5 and Ar1-H2,6, facilitated to differentiate the protons of
the three aromatic ring Ar1, Ar2 and Ar3 for the protons and
carbons. Further, H5, H20 and H30 showed HMBC correlation with
C10 (C]O) assisting the assignment of olefinic protons of H20, H30
and H100, H200. The HMBC long range correlations between Ar2-
H6 4 Ar2-C2 4 H30, Ar2-H5 4 Ar2-C1 4 H20, Ar1-H3, 5 4 Ar1-
C1 4 H5, Ar1-H2,6 4 Ar1-C4, led us to assign the chemical shifts
(Table A, Supplementary information) and establish the structure of
the molecule.
Antimalarial activity and cytotoxicity of the synthesised compounds (3e25).
Compound no. IC50 against IC50 against CC50 against SI for 3D7 SI for K1
P. falciparum P. falciparum Vero cells,
(3D7)
mg/mL (K1)
m
g/mL
m
g/mL
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
0.57
5.15
0.79
0.56
5.38
2.68
2.19
24.52
0.5
5.07
2.11
5.3
5.15
3.94
5.17
6.82
1.57
0.5
0.79
2.71
1.2
195.47
342.93
49.03
361.96
367.88
52.48
114.22
163.56
>20.39
520.94
97.97
99.95
51.42
50.65
106.00
45.48
247.43
93.17
252.48
285.95
206.01
282.32
306.12
358.19
238.29
572.25
112.93
192.53
>471.31
>116.28
>868.23
455.71
248.11
182.89
239.29
205.73
115.83
>219.3
489.94
1183.89
154.03
>417.5
515.05
344.06
>25.56
0.36
2.50
1.59
<0.76
4.30
<0.3
1.09
0.85
1.49
1.09
1.14
2.03
<0.76
0.71
0.27
2.79
<0.76
0.6
>500mg
2.2. Biology
260.47
496.72
210.89
272.51
260.83
417.64
235.14
166.67
347.86
319.65
429.75
317.30
309.03
419.75
2.2.1. Antimalarial activity
All the newly synthesized compounds were evaluated for their
antimalarial activity against two different strains of P. falciparum i.e.
3D7 (chloroquine sensitive) and K1 (chloroquine resistant)
employing the method reported earlier [39]. The antimalarial
activities of the compounds are depicted in Table 1. As evident from
the results almost all the compounds except compounds 4, 7, 10,
24.44
221.57
639.3
5.9
72.84
and 25 are potent antimalarial with IC50 < 2
the two Plasmodium strains. Chloroquine was taken as standard
whose IC50 value was found to be 0.006 and 0.6 g/mL against 3D7
mg/mL against either of
2.25
0.85
1.27
6.97
141.02
363.57
330.51
>71.74
1.22
19.55
m
>500
and K1 strains respectively. Among the active compounds, the
Chloroquine 0.006
mg/mL 0.6 mg/mL
compounds 6 (IC50 ¼ 0.36
(IC50 ¼ 0.27
m
g/mL), 11 (IC50 < 0.3
m
g/mL), and 20
m
g/mL) were found to be more potent than the stan-
dard antimalarial agent chloroquine against K1 strains of
P. falciparum. The cytotoxicity of these compounds were evaluated
against the vero cell lines of monkey. Their CC50 values ranged from
166.67 to 500 mg/mL. Based on IC50 and CC50 values selective
indices (SI) (IC50/CC50) of these compounds were calculated and
found to be in the range of 20.39e1183.89. Compound 20 was found
to be the best compound with IC50 ¼ 0.27
mg/mL and SI ¼ 1183.89
against P. falciparum K1 strains.
A closure look into the structure activity relationship indicates
that out of all the compounds, compounds having benzyloxy
phenyl or 3,4-methylenedioxy phenyl as 5-phenyl substitutents in
thizolopyrimidines (compounds 10, 12, 16 and 25) do not show any
significant activity against 3D7 strains but 3,4-methylenedioxy
phenyl substituted compounds(12 and 16) showed significant
activity against K1 strain. In general compounds having OMe
substituent in either of the phenyl rings (9, 11, 13e16, 18 and 19)
were found to show potent activity against K1 strain and activity
increases by increasing the number of OMe group. Furthermore
compounds with 3,4,5 trimethoxysubstituted phenyl ring
displayed very good activity against 3D7 strain as well (11, 19). If
the aromatic rings in the enone and styryl moieties are phenyl
and the 5-phenyl has substitutents the activity follows the order
Fig. 5. Important HMBC, COSY and nOe correlations of compound no 21.

S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
199
Cl > H > OMe (20 > 3 >13). The effect of nature and position of the
halogen substituents in the two phenyl rings of the stilbene and
propenone moieties was found to be F > Cl > Br and
oꢁ > mꢁ > pꢁ. Further, an interesting observation is observed that
when the value of R changes from H to Cl the effect of the position
of the halogens on the activity was found to be the just reversed
and become pꢁ > mꢁ > oꢁ. Changing the Ar with heteroaromatic
(compound 17) did not offer any significant improvement in the
activity.
moiety with heteroaromatic (17) did not offer any significant
improvement in the activity.
3. Conclusion
In conclusion, a series of novel pluripotent (E)-1-(3-methyl-5-
aryl-7-styryl-5H-thiazolo[3,2-a]pyrimidin-6-yl)-3-phenylprop-2-en-
1-ones have been synthesized from 5-acetyl-6-methyl-4-aryl
dihydropyrimidine-2-thiones in very good yields. The compounds
were evaluated for their antimalarial and HIV-RT inhibitory activi-
ties. A number of compounds showed significant to moderate
antimalarial and HIV-RT inhibitory activities. Three compounds 6,
11, and 20 were found to more potent than the standard drug
Chloroquine against K1 strains of P. falciparum. These compounds
with three different pharmcophores have potential to be exploited
for explorations in medicinal chemistry.
2.2.2. Anti-HIV-1 evaluation
All the newly synthesized compounds (3e25) were also evalu-
ated for their reverse transcriptase inhibitory activity at two
different concentrations 10 and 100
shown in Table 2.
mg/mL and the results are
At 10
mg/mL only one compound i.e. compound 16 showed
significant (58%) RT inhibition. However, at 100
m
g/mL RT inhibition
ranges from 11 to 73%. Among all the compounds screened, three
compounds 6 (73.44%), 11 (66.92%) and 16 (70.81%) showed very
good RT inhibitory activities. Other compounds of the series
showed moderate to good inhibitory activity. Nevirapine a non-
nucleoside reverse transcriptase (NNRT) inhibitor clinically used
4. Experimental
4.1. Chemistry
Commercially available reagent grade chemicals and solvents
were used as received. All reactions were followed by TLC on E.
Merck Kieselgel 60 F254, with detection by UV light, spraying a 20%
KMnO4 aq. solution or exposure to I2 vapours. Column chroma-
tography was performed on silica gel (60e120 mesh E. Merck). IR
spectra were recorded as thin films or in KBr solution with a Per-
kineElmer Spectrum RX-1 (4000e450 cmꢁ1) spectrophotometer.
The 1H (400 and 300 MHz) and 13C NMR (100 and 50 MHz) spectra
were recorded on a Bruker Avance-400, Bruker DRX-300 and
Bruker DRX-200 in DMSO, CD3OD and CDCl3. Chemical shift values
are reported in ppm relative to TMS (tetramethylsilane) as internal
reference, unless otherwise stated: s (singlet), d (doublet), t
(triplet), m (multiplet), dd (double doublet), bs (broad singlet); J in
hertz. ESI mass spectra were performed using Quattro II (Micro-
mass). Elemental analyses were performed on a PerkineElmer
2400 II elemental analyzer.
drug, showed 97.9% inhibition at 10 mg/mL concentration.
A closure look into structure activity relationship indicates that
in general compounds having 4-chloro substituent in the phenyl
ring are least active in comparison to the other compounds. The
effect of substituent in the 5-phenyl ring on RT inhibition follows
activity order as H > OMe > Cl (3 > 13 > 20). Further, increasing the
number of OMe substitutents in either of the aromatic rings results
in enhancement of enzyme inhibitory activities. Compound 9 with
one OMe substituent on phenyl ring showed 33% RT inhibition
while compound 11 with increased number of methoxy substituent
led to strong inhibition (66%) of RT. Similar observation was made
for compounds 18 and 19. The halogen substituents in the two
phenyl rings of the stilbene and propenone moieties effect the
inhibition in the order F > Br > Cl. The position of the halogen
substituents on the phenyl rings has significant effect on the RT
inhibitory activity and follows the pattern of oꢁ > mꢁ > pꢁ.
Further replacement of the aromatic ring in the enone and stilbene
4.1.1. Typical procedure for the synthesis of compounds (3e25)
To a magnetically stirred solution of 5-acetyl-6-methyl-4-
aryldihydropyrimidine-2-thione (1ae1d) (1.0 equiv.) at 25 ꢀC in
ethanol as solvent, propargyl bromide (1.0 equiv.) and KOH
(5.0 equiv.) is added, the solution colour changes to yellow which is
marked by the formation of product i.e. thiazolopyrimidine. After
5 min aromatic aldehyde (2.1 equiv.) is added to the same pot and
now the reaction is shifted to an oil bath at 80 ꢀC. The reaction
mixture turned to red colour after sometime. The reaction mixture
was stirred at the same temperature for further half an hour. The
ethanol is evaporated under reduced pressure to give a crude mass
which was chromatographed over silica gel (60e120 mesh) using
ethylacetate: hexane as eluent to give the desired products.
Table 2
% HIV-1 RT inhibition activity of different styryl thiazolopyrimidine (3e25).
Compound no.
% Inhibition at 10
mg/mL
% Inhibition at 100 mg/mL
3
4
5
6
7
8
9
10
42.26
42.58
15.39
38.91
39.76
30.04
40.57
47.71
5.69
49.63
53.39
54.50
73.44
55.44
59.25
32.73
56.30
66.92
Nd
11
12
Nd
4.1.1.1. (E)-1-(3-Methyl-5-phenyl-7-styryl-5H-thiazolo[3,2-a]pyrimidin-
6-yl)-3-phenylprop-2-en-1-one (3). It was obtained by the reaction
of 1a (1.0 g, 4.0 mmol), propargyl bromide (0.5 mL, 4.0 mmol), KOH
(1.12 g, 20.0 mmol) and benzaldehyde (0.9 mL, 8.4 mmol) and
ethanol (20 mL) as solvent as described above as red solid,
mp ¼ 160e165 ꢀC; yield (1.30 g, 70%) ; IR (KBr) nmax cmꢁ1: 2926 (CH
stretching ), 1720 (C]O stretching), 1625 (C]N stretching), 696
(CH2eS stretch); ESMS: m/z ¼ 461 (M þ H)þ; 1H NMR (300 MHz,
13
14
15
16
17
18
19
20
21
22
23
24
39.35
31.23
9.22
48.59
50.89
41.40
70.81
54.39
55.92
51.33
30.55
26.12
16.57
11.41
26.47
18.56
58.78
47.71
48.40
30.07
23.57
17.96
13.23
10.62
17.80
17.64
97.91
CDCl3):
d
¼ 7.71 (d, 1H, J ¼ 15.42 Hz, H200), 7.54e7.47 (m, 5H, ArH,
H30), 7.42e7.38 (m, 4H, ArH), 7.33e7.20 (m, 9H, ArH, H100, H20), 6.38
(s, 1H, H5), 6.05 (s, 1H, H2), 2.14 (s, 3H, CH3); 13C NMR (50 MHz,
25
CDCl3):
d
¼ 187.5, 166.5, 151.4, 142.4, 139.6, 136.8, 136.4, 136.0, 135.4,
Nevirapine
129.6, 128.8, 128.7, 128.1, 128.0, 127.8, 127.4, 126.2, 125.7, 111.9, 101.1,

200
S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
57.5, 14.2. Anal. calcd. for C30H24N2OS: C, 78.23; H, 5.25; N, 6.08;
found: C, 78.20; H, 5.29; N, 6.04.
128.9, 128.8, 128.7, 128.4, 128.2, 126.7, 126.2, 123.9, 123.0, 111.9, 101.2,
57.5, 13.9. Anal. calcd. for C30H22Br2N2OS: C, 58.27; H, 3.59; N, 4.53;
found: C, 58.22; H, 3.69; N, 4.50.
4.1.1.2. (E)-3-(4-Chlorophenyl)-1-(7-(4-chlorostyryl)-3-methyl-5-phenyl-
5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (4). It was obtained
by the reaction of 1a (1.0 g, 4.0 mmol), propargyl bromide (0.5 mL,
4.0 mmol), KOH (1.12 g, 20.0 mmol) and 4-chlorobenzaldehyde
(1.19 g, 8.4 mmol) and ethanol (20 mL) as solvent as described above
4.1.1.6. (E)-3-(4-Fluorophenyl)-1-(7-(4-fluorostyryl)-3-methyl-5-phenyl-
5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (8). It was
obtained by the reaction of 1a (1.0 g, 4.0 mmol), propargyl bromide
(0.5 mL, 4.0 mmol), KOH (1.12 g, 20.0 mmol) and 4-fluo-
robenzaldehyde (1.05 mL, 8.4 mmol) and ethanol (20 mL) as solvent
as described above as red solid, mp ¼ 153e156 ꢀC; yield (1.4 g, 71%);
IR (KBr) nmax cmꢁ1: 2932 (CH stretching), 1627 (-C]O stretching),
1560 (-C]N- stretch), 703 (CHeS stretch); ESMS: m/z ¼ 497
as red solid, mp ¼ 184e188 ꢀC; yield (1.45 g, 68%); IR (KBr) nmax cmꢁ1
:
2924 (CH stretching), 1630 (-C]O stretching), 1564 (-C]N stretch-
ing), 700 (CHeS stretch); ESMS: m/z ¼ 530 (M þ H)þ; 1H NMR
(300 MHz, CDCl3):
d
¼ 7.66 (d, 1H, J ¼ 15.42 Hz, H200), 7.49e7.35 (m,
7H, ArH, H30), 7.35e7.24 (m, 9H, ArH, H100, H20), 6.37 (s, 1H, H5), 6.12(s,
(M þ H)þ; 1H NMR (300 MHz, CDCl3):
¼ 7.66 (d, 1H, J ¼ 15.48 Hz,
d
1H, H2), 2.15 (s, 3H, CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.4, 167.1,
H200), 7.50e7.40 (m, 6H, ArH, H30), 7.30e7.22 (m, 6H, ArH, H100),
152.0, 142.3, 138.3, 136.2, 135.6, 135.4, 134.9, 134.7, 133.9, 129.1, 129.0,
128.9, 128.5, 128.4, 128.2, 126.6, 126.2, 111.8, 101.2, 57.5, 13.9. Anal.
calcd. for C30H22N2Cl2OS: C, 68.05; H, 4.19; N, 5.29; found: C, 68.01; H,
4.24; N, 5.31.
7.03e6.94 (m, 4H, ArH, H20), 6.38 (s, 1H, H5), 6.10 (s, 1H, H2), 2.15 (s,
3H, CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.5, 167.0, 152.0, 142.4,
138.2,136.1,135.4,132.6,131.7,129.6, 129.4, 129.1,128.9,128.8,128.1,
127.8, 126.2, 125.9, 116.1, 115.7, 111.7, 101.0, 57.5, 13.9. Anal. calcd. for
C30H22F2N2OS: C; 72.56; H, 4.47; N, 5.64; found: C, 72.53; H, 452; N,
5.60.
4.1.1.3. (E)-3-(3-Chlorophenyl)-1-(7-(3-chlorostyryl)-3-methyl-5-
phenyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (5). It was
obtained by the reaction of 1a (1.0 g, 4.0 mmol), propargyl bromide
(0.5 mL, 4.06 mmol), KOH (1.12 g, 20.0 mmol) and 3-chlor-
obenzaldehyde (1.19 g, 8.4 mmol) and ethanol (20 mL) as solvent as
described above as red solid, mp ¼ 142e145 ꢀC; yield (1.54 g, 72%);
IR (KBr) nmax cmꢁ1: 2925 (CH stretching), 1635 (-C]O stretching),
1566 (-C]N- stretch), 681 (CHeS stretch); ESMS: m/z ¼ 530
4.1.1.7. (E)-3-(4-Methoxyphenyl)-1-(7-(4-methoxystyryl)-3-methyl-
5-phenyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (9). It
was obtained by the reaction of 1a (1.0 g, 4.0 mmol), propargyl
bromide (0.5 mL, 4.0 mmol), KOH (1.12 g, 20.0 mmol) and 4-
methoxybenzaldehyde (1.16 mL, 8.4 mmol) and ethanol (20 mL)
as solvent as described above as red solid, mp ¼ 100e113 ꢀC; yield
(1.45 g, 69%); IR (KBr) nmax cmꢁ1 : 2934 (CH stretching ), 1640 (-C]
O stretching), 1605 (-C]N- stretch), 688 (CH-S stretch); ESMS: m/
z ¼ 521 (M þ H)þ; 1H NMR (300 MHz, CDCl3): 7.68 (d, 1H,
J ¼ 15.48 Hz, H200), 7.54e7.41 (m, 6H, ArH, H30), 7.30e7.23 (m, 6H,
ArH, H20), 6.85e6.80 (m, 4H, ArH, H100), 6.38 (s, 1H, H5), 6.06 (s, 1H,
H2), 3.82 (s, 6H, OCH3 ), 2.14 (s, 3H, CH3); 13C NMR (50 MHz, CDCl3):
(M þ H)þ; 1H NMR (300 MHz, CDCl3):
¼ 7.64 (d, 1H, J ¼ 15.45 Hz,
d
H200), 7.45e7.37 (m, 6H, ArH, H30), 7.34e7.31 (m, 4H, ArH), 7.28e7.18
(m, 6H, ArH, H100, H20), 6.39 (s, 1H, H5), 6.12 (s, 1H, H2), 2.15 (s, 3H,
CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.3, 167.2, 152.1, 142.3, 138.2,
138.1, 137.3, 136.2, 135.4, 134.9, 130.1, 130.0, 129.6, 129.2, 128.9,
128.8, 128.2, 127.7, 127.5, 127.2, 126.2, 125.7, 125.3, 111.9, 101.4, 57.5,
14.0. Anal. calcd. for C30H22Cl2N2OS: C, 68.05; H, 4.19; N, 5.29;
found: C, 68.00; H, 4.23; N, 5.26.
d
¼ 187.9, 166.8, 160.9, 160.3, 142.6, 139.2, 136.1, 129.4, 128.9, 128.7,
128.3, 127.9, 126.3, 125.9, 124.1, 119.9, 114.2, 111.4, 101.0, 57.5, 55.3,
13.9. Anal. calcd. for C32H28N2O3S: C, 73.82; H, 5.42; N, 5.38; found:
C, 73.80; H, 5.49; N, 5.35.
4.1.1.4. (E)-3-(2-Chlorophenyl)-1-(7-(2-chlorostyryl)-3-methyl-5-phenyl-
5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (6). It was obtained
by the reaction of 1a (1.0 g, 4.0 mmol), propargyl bromide (0.5 mL,
4.1.1.8. (E)-3-(4-(Benzyloxy)phenyl)-1-(7-(4-(benzyloxy)styryl)-3-
methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one
(10). It was obtained by the reaction of 1a (1.0 g, 4.0 mmol),
propargyl bromide (0.5 mL, 4.0 mmol), KOH (1.12 g, 20.0 mmol)
and 4-benzyloxybenzaldehyde (1.80 g, 8.4 mmol) and ethanol
(20 mL) as solvent as described above as red solid,
mp ¼ 190e193 ꢀC; yield (1.85 g, 68%) ; IR (KBr) nmax cmꢁ1 : 2934
(CH stretching ), 1640 (-C]O stretching), 1605 (-C]N- stretch), 688
(CHeS stretch); ESMS: m/z ¼ 673 (M þ H)þ; 1H NMR (300 MHz,
4.0 mmol),
KOH
(1.12 g,
20.0 mmol)
and
2-chloroben-
zaldehyde (1.19 g, 8.4 mmol) and ethanol (20 mL) as solvent as
described above as red solid, mp ¼ 158e160 ꢀC; yield (1.52 g, 71%); IR
(KBr) nmax cmꢁ1 : 2925 (CH stretching ), 1600 (-C]O stretching), 1564
(-C]N- stretch), 692 (CHeS stretch); ESMS: m/z ¼ 530 (M þ H)þ; 1H
NMR (300 MHz, CDCl3):
d
¼ 8.09 (d, 1H, J ¼ 15.45 Hz, H200), 7.93 (d, 1H,
J ¼ 15.45 Hz, H30), 7.54e7.49 (m, 5H, ArH, H100, H20), 7.35e7.26 (m, 6H,
ArH), 7.23e7.17 (m, 2H, ArH), 7.12e7.07 (m, 2H, ArH ), 6.39 (s, 1H, H5),
6.12 (s, 1H, H2), 2.15 (s, 3H, CH3); 13C NMR (50 MHz CDCl3):
d
¼ 187.3,
CDCl3):
d
¼ 7.68 (d, 1H, J ¼ 15.45 Hz, H200), 7.54e7.33 (m, 16H, ArH,
167.1, 152.1, 142.3, 136.1, 135.5, 135.0, 134.4, 133.6, 132.7, 130.5, 130.1,
129.7, 128.9, 128.2, 127.3, 127.1, 126.9, 126.3, 112.0, 101.6, 57.6, 13.9. Anal.
calcd. for C30H22Cl2N2OS: C, 68.05; H, 4.19; N, 5.29; found: C, 68.01; H,
4.21; N, 5.30.
H30), 7.30e7.23 (m, 6H, ArH, H20), 6.92e6.88 (m, 4H, ArH, H100), 6.38
(s, 1H, H5), 6.06 (s, 1H, H2), 5.08 (s, 2H, OCH2 ), 5.07 (s, 2H, OCH2 ),
2.14 (s, 3H, CH3) ; Anal. calcd. for C44H36N2O3S: C, 78.54; H, 5.39; N,
4.16; found: C, 78.50; H, 5.42; N, 4.13.
4.1.1.5. (E)-3-(4-Bromophenyl)-1-(7-(4-bromostyryl)-3-methyl-5-phenyl-
5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (7). It was obtained
by the reaction of 1a (1.0 g, 4.0 mmol), propargyl bromide (0.5 mL,
4.1.1.9. (E)-1-(3-Methyl-5-phenyl-7-(3,4,5-trimethoxystyryl)-5H-
thiazolo[3,2-a]pyrimidin-6-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-
1-one (11). It was obtained by the reaction of 1a (1.0 g, 4.0 mmol),
propargyl bromide (0.5 mL, 4.0 mmol), KOH (1.12 g, 20.0 mmol)
and 3,4,5-trimethoxybenzaldehyde (1.67 g, 8.4 mmol) and ethanol
(20 mL) as solvent as described above as red solid, mp ¼
180e182 ꢀC; yield (1.82 g in 70%); IR (KBr) nmax cmꢁ1: 2929 (CH
stretching ), 1631 (-C]O stretching), 1581 (-C]N- stretch), 697
(CHeS stretch); ESMS: m/z ¼ 641 (M þ H)þ; 1H NMR (300 MHz,
4.0 mmol),
KOH
(1.12 g,
20.0 mmol)
and
4-bromoben-
zaldehyde (1.57 g, 8.4 mmol) and ethanol (20 mL) as solvent as
described above as red solid, mp ¼ 165e168 ꢀC; yield (1.75 g, 70%); IR
(KBr) nmax cmꢁ1: 2932 (CH stretching ), 1627 (-C]O stretching), 1560
(C]N stretch), 703 (CHeS stretch); ESMS: m/z ¼ 619 (M þ H)þ; 1H NMR
(300 MHz, CDCl3):
d
¼ 7.64 (d, 1H, J ¼ 15.48 Hz, H200), 7.47e7.39 (m, 7H,
ArH, H30), 7.36e7.31 (m, 6H, ArH), 7.28e7.25 (m, 3H, ArH, H100, H20), 6.37
CDCl3):
d
¼ 7.59 (d, J ¼ 15.42 Hz, 1H, H200), 7.43 (d, J ¼ 7.44 Hz, 2H,
(s, 1H, H5), 6.11 (s, 1H, H2), 2.15 (s, 3H, CH3); 13C NMR (50 MHz, CDCl3):
ArH), 7.38 (s, 1H, ArH,), 7.33e7.28 (m, 5H, ArH, H20, H100, H30), 6.72
(d, J ¼ 1.95 Hz, 4H, ArH,), 6.40 (s, 1H, H5), 6.11 (s,1H, H2), 3.85 (s, 6H,
d
¼ 187.4, 167.1, 152.0, 142.3, 138.4, 136.2, 135.5, 134.4, 132.1, 131.9, 129.1,

S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
201
OCH3 ), 3.65 (s, 6H, OCH3), 3.62 (s, 6H, OCH3 ), 2.15 (s, 3H, CH3); 13
NMR (50 MHz, CDCl3):
139.0, 138.9, 136.3, 136.2, 132.0, 131.0, 128.8, 128.1, 128.0, 126.2,
111.6, 104.7, 60.8, 57.4, 55.8, 55.7, 13.9. Anal. calcd. for C36H36N2O7S:
C, 67.48; H, 5.66; N, 4.37; found: C, 67.45; H, 5.71; N, 4.35.
C
H5), 6.08 (s, 1H, H2), 3.76 (s, 3H, OCH3), 2.15 (s, 3H, CH3); 13C NMR
(50 MHz, CDCl3):
129.6, 129.4, 129.1, 128.9, 127.6, 125.6, 116.0, 115.7, 114.7, 114.1, 112.0,
101.4, 57.2, 55.2, 14.7. Anal. calcd. for C31H24F2N2O2S; C, 70.71; H,
4.59; N, 5.32; found: C, 70.70; H, 4.64; N, 5.30.
d
¼ 187.5, 167.1, 153.4, 153.3, 152.3, 142.4,
d
¼ 187.7, 159.4, 138.4, 136.2, 135.5, 134.8, 131.6,
4.1.1.10. (E)-3-(Benzo[d][1,3]dioxol-5-yl)-1-(7-((E)-2-(benzo[d][1,3]
dioxol-5-yl)vinyl)-3-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidin-
6-yl)prop-2-en-1-one (12). It was obtained by the reaction of 1a
(1.0 g, 4.0 mmol), propargyl bromide (0.5 mL, 4.0 mmol), KOH
(1.12 g, 20.0 mmol) and 3,4-methylenedioxybenzaldehyde (1.28 g,
8.4 mmol) and ethanol (20 mL) as solvent as described above as red
4.1.1.14. (E)-3-(Benzo[d][1,3]dioxol-5-yl)-1-(7-((E)-2-(benzo[d][1,3]
dioxol-5-yl)vinyl)-5-(4-methoxyphenyl)-3-methyl-5H-thiazolo[3,2-a]
pyrimidin-6-yl)prop-2-en-1-one (16). It was obtained by the reac-
tion of 1b (1.0 g, 3.6 mmol), propargyl bromide (0.43 mL, 3.6 mmol),
KOH (1.0 g, 18.0 mmol) and 3,4-methylenedioxybenzaldehyde
(1.14 g, 7.6 mmol) and ethanol (20 mL) as solvent as described
above as red solid, mp ¼ 185e189 ꢀC; yield (1.36 g, 65%) ; IR (KBr)
nmax cmꢁ1: 2922 (CH stretching ), 1714 (-C]O stretching), 1560
(-C]N stretch), 680 (CHeS stretch); ESMS: m/z ¼ 579 (M þ H)þ; 1H
solid, mp ¼ 156e160 ꢀC; yield (1.45 g, 65%) ; IR (KBr) nmax cmꢁ1
:
2900 (CH stretching ), 1730 (C]O stretching), 1598 (C]N stretch),
696 (CHeS stretch); ESMS: m/z ¼ 549 (M þ H)þ; 1H NMR (300 MHz,
CDCl3): 7.47 (d, 1H, J ¼ 15.66 Hz, H200), 7.40 (d, J ¼ 6.99 Hz, 2H, ArH),
7.32e7.24 (m, 4H, ArH, H30) 7.18e7.11 (m, 2H, ArH, H100), 7.05e6.98
(m, 4H, ArH, H20), 6.78e6.73 (m, 2H, ArH,), 6.38 (s, 1H, H5), 6.16 (s,
NMR (300 MHz, CDCl3):
d
¼ 7.62 (d, J ¼ 15.05 Hz, 1H, H200), 7.45 (d,
J ¼ 15.42 Hz,1H, H30), 7.33e7.28 (m, 2H, ArH, H100), 7.21e7.11 (m, 2H,
ArH, H20), 7.02e6.97 (m, 4H, ArH), 6.81e6.72 (m, 4H, ArH), 6.28 (s,
1H, H5); 6.06 (s,1H); 2.15 (s, 3H, CH3). Anal. calcd. for C33H26N2O6S;
C, 68.50; H, 4.53; N, 4.84; found: C, 68.55; H, 4.58; N, 4.80.
1H, H2), 5.97 (s, 2H, OCH2 ), 5.95 (s, 2H, OCH2 ), 2.18 (s, 3H, CH3); 13
C
NMR (50 MHz, CDCl3):
d
¼ 187.8, 148.5, 148.2, 136.1, 130.9, 128.8,
128.1, 126.2, 123.9, 123.1, 111.5, 108.5, 106.5, 101.3, 101.2, 57.6, 13.9.
Anal. calcd. for C32H24N2O5S: C, 70.06; H, 4.41; N, 5.11; found: C,
70.03; H, 4.46; N, 5.10.
4.1.1.15. (E)-1-(5-(4-Methoxyphenyl)-3-methyl-7-((E)-2-(thiophen-
2-yl)vinyl)-5H-thiazolo[3,2-a]pyrimidin-6-yl)-3-(thiophen-2-yl)prop-
2-en-1-one (17). It was obtained by the reaction of 1b (1.0 g,
3.6 mmol), propargyl bromide (0.43 mL, 3.6 mmol), KOH (1.0 g,
18.0 mmol) and thiophene-2-carboxaldehyde(0.71 mL, 7.6 mmol)
and ethanol (20 mL) as solvent as described above as red solid,
mp ¼ 143e145 ꢀC; yield (1.27 g, 70%) ; IR (KBr) nmax cmꢁ1: 2937 (CH
stretching ), 1623 (-C]O stretching), 1513 (-C]N stretch), 700
(CHeS stretch); ESMS: m/z ¼ 503 (M þ H)þ; 1H NMR (300 MHz,
4.1.1.11. (E)-1-(5-(4-Methoxyphenyl)-3-methyl-7-styryl-5H-thiazolo
[3,2-a]pyrimidin-6-yl)-3-phenylprop-2-en-1-one (13). It was obtained
by the reaction of 1b (1.0 g, 3.6 mmol), propargyl bromide (0.43 mL,
3.6 mmol), KOH (1.0 g, 18.0 mmol) and benzaldehyde (0.80 mL,
7.6 mmol) and ethanol (20 mL) as solvent as described above as red
solid, mp ¼ 138e140 ꢀC; yield (1.26 g in 71%); IR (KBr) nmax cmꢁ1
:
2930 (CH stretching), 1722 (-C]O stretching), 1574 (-C]N stretch),
686 (CHeS stretch); ESMS: m/z ¼ 491 (M þ H)þ; 1H NMR (300 MHz,
CDCl3): 7.72 (d, J ¼ 15.45 Hz, 1H, H200), 7.56e7.45 (m, 6H, ArH, H30),
7.39e7.26 (m, 9H, ArH, H100, H20 ), 6.83 (d, J ¼ 8.61, 2H, ArH), 6.31 (s,
1H, H5), 6.07 (s, 1H, H2), 3.76 (s, 3H, CH3), 2.16 (s, 3H, CH3); 13C NMR
CDCl3):
d
¼ 7.90 (d, J ¼ 14.53 Hz, 1H, H200), 7.70 (d, J ¼ 15.09 Hz, 1H,
H30), 7.34e7.28 (m, 3H, ArH, H100), 7.24e7.20 (m, 3H, ArH, H20),
7.17e7.13 (m, 2H, ArH), 7.04e7.00 (m, 2H, ArH), 6.82 (d, J ¼ 8.58 Hz,
2H, ArH), 6.28 (s, 1H, H5); 6.08 (s,1H, H2); 3.76 (s, 3H, OCH3 ); 2.15
(s, 3H, CH3); anal. calcd. for C27H22N2O2S3 : C, 64.51; H, 4.41; N,
5.57; found: C, 64.45; H, 4.47; N, 5.53
(50 MHz, CDCl3):
d
¼ 187.9, 166.7, 159.3, 151.6, 139.7, 136.7, 136.4,
136.1,135.4,129.7,128.9,128.8,128.7,128.0,127.8,127.7,127.5,125.9,
114.1, 112.2, 101.1, 57.2, 55.2, 14.0. Anal. calcd. for C31H26N2O2S; C,
75.89; H, 5.34; N, 5.71; found: C, 75.85; H, 5.38; N, 5.70.
4.1.1.16. (E)-1-(3-Methyl-5-(3,4,5-trimethoxyphenyl)-7-(3,4,5-trimetho-
xystyryl)-5H-thiazolo[3,2-a]pyrimidin-6-yl)-3-(3,4,5-trimethoxyphenyl)
prop-2-en-1-one (18). It was obtained by the reaction of 1c (1 g,
2.9 mmol), propargyl bromide (0.35 mL, 2.9 mmol), KOH (0.83 g,
14.5 mmol) and 3,4,5-trimethoxybenzaldehyde (1.22 mL, 6.2 mmol)
and ethanol (20 mL) as solvent as described above as red solid,
mp ¼ 182e184 ꢀC; yield (1.27 g, 69%); IR (KBr) nmax cmꢁ1: 2939 (CH
stretching), 1630 (-C]O stretching), 1581 (-C]N stretch), 700 (CHeS
stretch); ESMS: m/z ¼ 731 (M þ H)þ; 1H NMR (300 MHz, CDCl3):
4.1.1.12. (E)-3-(4-Chlorophenyl)-1-(7-(4-chlorostyryl)-5-(4-methox-
yphenyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-
one (14). It was obtained by the reaction of 1b (1.0 g, 3.6 mmol),
propargyl bromide (0.43 mL, 3.6 mmol), KOH (1.0 g,18.0 mmol) and
4-chlorobenzaldehyde (1.06 g, 7.6 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 165e168 ꢀC; yield
(1.39 g, 69%); IR (KBr) nmax cmꢁ1: 2923 (CH stretching), 1723 (-C]O
stretching), 1595 (-C]N stretch), 682 (CHeS stretch); ESMS: m/
z ¼ 560 (M þ H)þ; 1H NMR (300 MHz, CDCl3): 7.69 (d, J ¼ 14.61 Hz,
1H, H200), 7.48e7.35 (m, 5H, ArH, H30), 7.32e7.24 (m, 8H, ArH, H100,
H20), 6.83 (d, J ¼ 8.31, 2H, ArH), 6.30 (s, 1H, H5), 6.12 (s, 1H, H2), 3.76
(s, 3H, OCH3), 2.16 (s, 3H, CH3); Anal. calcd. for C31H24Cl2N2O2S: C,
66.55; H, 4.32; N, 5.01; found: C, 66.50; H, 4.34; N, 5.05.
d
¼ 7.56 (d, J ¼ 15.39 Hz, 1H, H200), 7.41 (d, J ¼ 15.63 Hz, 1H, H30),
7.30e7.24 (m, 2H, H20 , H200), 6.70 (d, J ¼ 1.65 Hz, 4H, ArH), 6.59 (s, 2H,
ArH), 6.30 (s,1H, H5), 6.12 (s,1H, H2), 3.82e3.77 (m,15H, OCH3), 3.63 (s,
6H, OCH3 ), 3.59 (s, 6H, OCH3 ), 2.16 (s, 3H, CH3); 13C NMR (50 MHz,
CDCl3):
d
¼ 187.3, 166.8, 153.4, 152.1, 139.8, 139.1, 138.7, 137.8,
136.4, 131.8, 130.9, 128.8, 128.0, 128.0, 125.9, 111.6, 104.7, 104.2, 103.0,
96.1, 65.9, 60.7, 57.1, 55.9, 55.7, 13.9. Anal. calcd. for C39H42N2O10S: C,
64.09; H, 5.79; N, 3.83; found: C, 64.06; H, 5.81; N, 3.81; O, 21.94; S, 4.31.
4.1.1.13. (E)-3-(4-Fluorophenyl)-1-(7-(4-fluorostyryl)-5-(4-methoxyph-
enyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (15).
It was obtained by the reaction of 1b (1.0 g, 3.6 mmol), propargyl
bromide (0.43 mL, 3.6 mmol), KOH (1.0 g, 18.0 mmol) and 4-
fluorobenzaldehyde (0.94 mL, 7.6 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 159e162 ꢀC; yield
(1.42 g, 75%) ; IR (KBr) nmax cmꢁ1: 2931 (CH stretching ), 1700 (-C]
O stretching), 1567 (-C]N stretch), 677 (CHeS stretch); ESMS: m/
z ¼ 526 (M þ H)þ; 1H NMR (300 MHz, CDCl3) ¼ 7.66 (d, J ¼ 15.45 Hz,
1H, H200), 7.50e7.45 (m, 5H, ArH, H30), 7.36e7.16 (m, 4H, ArH, H100,
H20), 7.03e6.94 (m, 3H, ArH), 6.83 (d, J ¼ 8.61, 2H, ArH), 6.30 (s, 1H,
4.1.1.17. (E)-3-(4-Methoxyphenyl)-1-(7-(4-methoxystyryl)-3-methyl-
5-(3,4,5-trimethoxyphenyl)-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-
2-en-1-one (19). It was obtained by the reaction of 1c (1.0 g,
2.9 mmol), propargyl bromide (0.35 mL, 2.9 mmol), KOH (0.83 g,
14.5 mmol) and 4-methoxybenzaldehyde (0.85 mL, 6.2 mmol) and
ethanol (20 mL) as solvent as described above as red solid,
mp ¼ 148e150 ꢀC; yield (1.27 g, 69%) ; IR (KBr) nmax cmꢁ1: 2922 (CH
stretching ), 1629 (-C]O stretching), 1508 (-C]N- stretch), 768
(CHeS stretch); ESMS: m/z ¼ 611 (M þ H)þ; 1H NMR (300 MHz,
CDCl3):
d
¼ 7.65 (d, J ¼ 15.08 Hz, 1H, H200), 7.52e7.42 (m, 5H, ArH,

202
S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
H30), 7.28e7.22 (m, 2H, ArH, H100), 6.84e6.78 (m, 4H, ArH), 6.59 (s,
2H, ArH), 6.29 (s, 1H, H5), 6.07 (s, 1H, H2), 3.82e3.78 (m, 15H,
(1.34 g, 67%); IR (KBr) nmax cmꢁ1: 2967 (CH stretching), 1720 (-C]O
stretching), 1565 (-C]N- stretch), 676 (CHeS stretch); ESMS: m/
OCH3ꢂ5), 2.17 (s, 3H, CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.8,
z ¼ 564 (M þ H)þ; 1H NMR (300 MHz, CDCl3):
¼ 7.67 (d, J ¼ 15.51 Hz,
d
166.5, 160.9, 160.3, 153.3, 152.0, 139.1, 138.0, 137.6, 136.2, 136.1,
129.4, 129.2, 128.8, 128.2, 126.0, 123.9, 114.2,111.3, 103.0, 100.4, 60.5,
57.3, 55.9, 55.1, 13.9. Anal. calcd. for C35H34N2O6S: C, 68.83; H, 5.61;
N, 4.59; found: C, 68.80; H, 5.67; N, 4.64.
1H, H200), 7.51e7.41 (m, 3H, ArH, H30), 7.38e7.35 (m, 3H, ArH),
7.33e7.22 (m, 9H, ArH, H100), 6.33 (s, 1H, H5), 6.14 (s, 1H, H2), 2.14 (s,
3H, CH3); 13C NMR (50 MHz, CDCl3):
135.8, 134.9, 134.7, 134.0, 129.1, 129.0, 128.9, 128.5, 128.1, 127.7, 126.3,
124.0, 123.2, 111.4, 101.7, 56.9, 13.9. Anal. calcd. for C30H21Cl3N2OS: C,
63.90; H, 3.75; N, 4.97; found: 63.87; H, 3.77; N, 4.91.
d
¼ 187.2, 140.7, 138.4, 136.0,
4.1.1.18. (E)-1-(5-(4-Chlorophenyl)-3-methyl-7-styryl-5H-thiazolo[3,2-
a]pyrimidin-6-yl)-3-phenylprop-2-en-1-one (20). It was obtained by
the reaction of 1d (1.0 g, 3.5 mmol), propargyl bromide (0.42 mL,
3.5 mmol), KOH (0.99 g, 17.5 mmol) and benzaldehyde (0.79 mL,
7.4 mmol) and ethanol (20 mL) as solvent as described above as red
solid, mp ¼ 204e205 ꢀC; yield (1.21 g, 69%); IR (KBr) nmax cmꢁ1: 2970
(CH stretching), 1623 (-C]O stretching), 1563 (-C]N- stretch), 687
(CHeS stretch); ESMS: m/z ¼ 496 (M þ H)þ; 1H NMR (300 MHz,
4.1.1.22. (E)-3-(4-Bromophenyl)-1-(7-(4-bromostyryl)-5-(4-chlorophe-
nyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (24).
It was obtained by the reaction of 1d (1.0 g, 3.5 mmol), propargyl
bromide (0.42 mL, 3.5 mmol), KOH (0.99 g, 17.5 mmol) and 4-
bromobenzaldehyde (1.38 g, 7.4 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 199e200 ꢀC; yield
(1.51 g, 65%); IR (KBr) nmax cmꢁ1: 2964 (CH stretching ), 1628 (-C]O
stretching), 1566 (-C]N- stretch), 678 (CHeS stretch); ESMS: m/
CDCl3):
d
¼ 7.74 (d, J ¼ 15.18 Hz,1H, H200), 7.59e7.48 (m, 5H, ArH, H30),
7.43e7.38 (m, 2H, ArH, H100), 7.35e7.24 (m, 10H, ArH, H20), 6.35 (s,1H,
H5), 6.12 (s, 1H, H2), 2.14 (s, 3H, CH3); 13C NMR (50 MHz, CDCl3):
z ¼ 653 (M þ H)þ; 1H NMR (300 MHz, CDCl3):
d
¼ 7.65
d
¼ 187.6,167.0 (C9),152.4,141.0,139.7,137.0,136.3,135.9,135.4,133.9,
(d, J ¼ 15.65 Hz, 1H, H200), 7.49 (d, J ¼ 5.61 Hz, 1H, ArH), 7.43e7.39 (m,
4H, ArH, H30), 7.36e7.30 (m, 7H, ArH, H100), 7.27e7.23 (m, 3H, ArH,
H20), 6.33 (s, 1H, H5), 6.14 (s, 1H, H2), 2.14 (s, 3H, CH3); 13C NMR
129.7, 128.9, 128.8, 127.8, 127.7, 127.5, 126.0, 111.3, 101.3, 56.9(C5),
13.9(CH3). Anal. calcd. for C30H23ClN2OS: C, 72.79; H, 4.68; N, 5.66;
found: C, 72.75; H, 4.73; N, 5.70.
(50 MHz, CDCl3):
d
¼ 187.2,167.0,152.2,140.7,138.5,136.0,135.9,135.1,
134.2, 134.0, 132.1, 132.0, 131.7, 129.1, 129.0, 128.7, 128.2, 127.7, 126.4,
124.0,123.2,111.4,101.6, 56.9,13.9. Anal. calcd. for C30H21Br2ClN2OS: C,
55.19; H, 3.24; N, 4.29; found: C, 55.15; H, 3.27; N, 4.28.
4.1.1.19. (E)-3-(2-Chlorophenyl)-1-(5-(4-chlorophenyl)-7-(2-chlor-
ostyryl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-
one (21). It was obtained by the reaction of 1d (1.0 g, 3.5 mmol),
propargyl bromide (0.42 mL, 3.5 mmol), KOH (0.99 g,17.5 mmol) and
2-chlorobenzaldehyde (0.84 mL, 7.4 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 185e186 ꢀC; yield
(1.21 g, 70%); IR (KBr) nmax cmꢁ1: 2921 (CH stretching ), 1707 (-C]O
stretching), 1567 (-C]N- stretch), 673 (CHeS stretch); ESMS: m/
4.1.1.23. (E)-3-(4-(Benzyloxy)phenyl)-1-(7-(4-(benzyloxy)styryl)-5-
(4-chlorophenyl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-
en-1-one (25). It was obtained by the reaction of 1d (1.0 g,
3.5 mmol), propargyl bromide (0.42 mL, 3.5 mmol), KOH (0.99 g,
17.5 mmol) and 4-benzyloxybenzaldehyde (1.58 g, 7.4 mmol) and
ethanol (20 mL) as solvent as described above as red solid,
mp ¼ 170e171 ꢀC; yield (1.71 g, 68%); IR (KBr) nmax cmꢁ1: 2925 (CH
stretching), 1633 (-C]O stretching), 1507 (-C]N- stretch), 615
(CHeS stretch); ESMS: m/z ¼ 708 (M þ H)þ; 1H NMR (300 MHz,
z ¼ 564 (M þ H)þ; 1H NMR (400 MHz, CDCl3)
¼ 8.05 (d, J ¼ 15.50 Hz,
d
1H, H-200), 7.89 (d, J ¼ 15.62 Hz, 1H, H-30), 7.51e7.47 (m, 2H, AreH),
7.38e7.35 (m, 5H, AreH, H-100), 7.30e7.25 (m, 3H, H-20, AreH),
7.23e7.16 (m, 2H, AreH), 7.10e7.04 (m, 2H, AreH), 6.34 (s, 1H, H-5),
6.13 (s, 1H, H-2), 2.13 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3)
CDCl3):
d
¼ 7.66 (d, J ¼ 15.39, 1H, H200), 7.51e7.31 (m, 16H, ArH, H30),
d
¼ 187.5, 167.3, 152.6, 141.1, 136.1, 135.9, 135.3, 134.7, 134.6, 134.3,
7.28e7.16 (m, 6H, ArH), 6.91e6.87 (m, 3H, H200, H20, H100), 6.33 (s,1H,
133.8, 133.2, 130.6, 130.5, 130.4, 130.3, 129.9, 129.2, 128.9, 128.0, 127.5,
127.3, 127.1, 127.0, 111.8, 101.9, 57.3, 14.1. Anal. calcd. for
C30H21Cl3N2OS: 63.90; H, 3.75; N, 4.97; found: 63.88; H, 3.77; N, 4.95.
H5), 6.07 (s,1H, H2), 5.08 (s, 2H, OCH2), 5.07 (s, 2H, OCH2), 2.14 (s, 3H,
CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.5, 166.6, 160.1, 159.6, 152.2,
141.1,139.3,136.6,136.5,135.8,133.8,129.4, ,128.9,128.5,128.0,127.7,
127.4, 125.8, 123.9, 115.1, 111.1, 69.9, 56.8, 13.9. Anal. calcd. for
C44H35ClN2O3S: C, 74.72; H, 4.99; N, 3.96; found: C, 74.70; H, 5.01; N,
3.93.
4.1.1.20. (E)-3-(3-Chlorophenyl)-1-(5-(4-chlorophenyl)-7-(3-chlorosty-
ryl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (22).
It was obtained by the reaction of 1d (1.0 g, 3.5 mmol), propargyl
bromide (0.42 mL, 3.5 mmol), KOH (0.99 g, 17.5 mmol ) and 3-
chlorobenzaldehyde (0.85 mL, 7.4 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 175e176 ꢀC; yield
(1.42 g, 71%) ; IR (KBr) nmax cmꢁ1 : 2921 (CH stretching ), 1707 (-C]O
stretching), 1567 (-C]N- stretch), 673 (CHeS stretch); ESMS: m/
4.1.2. 2D NMR studies
The 2D NMR Studies of compound 21 were carried out on a Bruker
Avance-400 MHz (300 K) in CDCl3 solvent with TMS as an internal
standard. 13C NMR spectra were recorded with complete proton
decoupling. The assignment was carried out with the help of COSY,
NOESY, HSQC and HMBC experiments. 2D-NOESY was used to fix the
spatial correlations which helped in assignment. All the spectra were
recorded in phase sensitive mode except for COSY which is in
magnitude mode. The spectra were acquired with 2*256 FID for
NOESYand HMBC, 256 Fids for HSQC and 128 Fids for COSY containing
4e16 transients for all the experiments with a recycle delay of 1.5 s.
z ¼ 564 (M þ H)þ; 1H NMR (300 MHz, CDCl3):
¼ 7.67 (d, J ¼ 15.43 Hz,
d
1H, H200), 7.46e7.41 (m, 3H, ArH, H30), 7.36e7.30 (m, 6H, ArH, H100),
7.29e7.21 (m, 6H, ArH, H20), 6.36 (s,1H, H5), 6.17 (s,1H, H2), 2.15 (s, 3H,
CH3); 13C NMR (50 MHz, CDCl3):
d
¼ 187.1, 167.0, 152.0, 140.7, 138.2,
138.1, 137.2, 136.0, 135.8, 134.9, 134.8, 134.1, 130.1, 129.6, 129.0, 128.9,
127.7, 127.5, 127.2, 125.7, 125.3, 111.5, 101.7, 96.1, 56.9, 13.9. Anal. calcd.
for C30H21Cl3N2OS: C, 63.90; H, 3.75; N, 4.97; found: 63.86; H, 3.80;
N, 4.99.
4.2. Biology
4.1.1.21. (E)-3-(4-Chlorophenyl)-1-(5-(4-chlorophenyl)-7-(4-chlorosty-
ryl)-3-methyl-5H-thiazolo[3,2-a]pyrimidin-6-yl)prop-2-en-1-one (23).
It was obtained by the reaction of 1d (1.0 g, 3.5 mmol), propargyl
bromide (0.42 mL, 3.5 mmol), KOH (0.99 g, 17.5 mmol) and 4-
chlorobenzaldehyde (1.05 g, 7.4 mmol) and ethanol (20 mL) as
solvent as described above as red solid, mp ¼ 197e198 ꢀC; yield
4.2.1. Antimalarial assay
Antimalarial assay for synthetic compounds was carried out
against CQ sensitive 3D7 as well as CQ resistant K1clone of
P. falciparum [39]. Parasite culture was maintained in vitro in
RPMI-1640 (HEPES modification) medium supplemented with 0.5%
AlbuMaxII, 0.2% glucose, 0.2% NaHCO3 and additionally 15 mM

S. Fatima et al. / European Journal of Medicinal Chemistry 55 (2012) 195e204
203
hypoxanthine, incubated at 37 ꢀC with 5% CO2 and daily change of
medium. Parasite growth rate and stage was determined by the
examination of a giemsa’s stained thin smear of the parasitized RBCs.
Stock solution of synthesized compounds were prepared at
10mg/mL in DMSO and stored at 0 ꢀC until use. Two fold serial
dilutions of these compounds as well as standard drug chloroquine
was developed. Optical density (OD) was measured by ELISA reader
at 405 nm (reference wavelength: 490 nm). The resulting colour
intensity is directly proportional to the actual RT activity. The
percentage inhibitory activity of RT inhibitors was calculated by
using the formula shown below.
ðOD 405 nm with inhibitorÞ
(50
mL per well) were prepared in 96 well microtiter plates. Infected
% RT inhibition ¼ 100 ꢁ
ꢂ 100
ðOD 405 nm without inhibitorÞ
erythrocytes (50
mL per well with 4% haematocrit and 1% para-
sitaemea) were added to these wells. Plates were incubated in CO2
incubator maintained at 37 ꢀC and 5% CO2. After 72 h incubation,
100 mL lytic buffer (20 mM Tris pH 7.5, 5 mM EDTA, 0.008% saponin,
Acknowledgments
and 0.08% Triton X-100) containing SYBR green (2X), was added to
each well and incubated for 4 h at room temp in dark. Plates were
read under fluorescence reader at ex.485 nm, em. 535 nm. IC50
values were determined on the basis of DNA content of the parasite
relative to controls using MS-EXEL.
Authors thank, CSIR network project “SPLENDID” and DRDO
New Delhi for financial assistance. Seerat and Anindra are thankful
to CSIR New Delhi for their SRF. We are also thankful to SAIF
Division, CDRI for providing the spectral data and microanalyses.
This is a CDRI communication No. 8286.
4.2.2. Cytotoxicity assay
Cytotoxic assay was carried out against monkey kidney cell line
C1008 (Vero cells) [40]. Cells were cultivated in 25 cm2 tissue
culture flask supplemented with MEM-medium and 15%FBS
provided with 5% CO2 at 37 ꢀC. For the cytotoxicity assay, cells were
washed with PBS, trypsinized with 0.25% trypsin and a cell
suspension was made in culture medium. Cells were counted in
Neubaur chamber and appropriate dilution was made (1 ꢂ105 cells/
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ejmech.2012.07.018.
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