Synthesis of thioether derivatives of quinazoline-4-one-2-thione and evaluation of their antiplatelet aggregation activity

Article abstract of DOI:10.1007/s12272-013-0192-5

A series of 2-(arylmethylthio)-3-phenylquinazolin-4-one derivatives have been synthesized and their antiplatelet aggregation activities were assessed against ADP and arachidonic acid-induced platelet aggregation in human plasma. Among the tested thioethers, derivative 2, 3, 5 and 16 were the most potent compounds with satisfactory IC₅₀ for inhibition of platelet aggregation induced by ADP. Analysis of global physicochemical parameters shows some correlations between activities and molecular volume and also surface area of the studied derivatives.

Full text of DOI:10.1007/s12272-013-0192-5

Arch. Pharm. Res.
DOI 10.1007/s12272-013-0192-5
RESEARCH ARTICLE
Synthesis of thioether derivatives of quinazoline-4-one-2-thione
and evaluation of their antiplatelet aggregation activity
•
Zahra Eskandariyan Marjan Esfahani Zadeh
•
•
Kamaleddin Haj Mohammad Ebrahim Tehrani
•
Vida Mashayekhi Farzad Kobarfard
Received: 4 February 2013 / Accepted: 16 June 2013
Ó The Pharmaceutical Society of Korea 2013
Abstract A series of 2-(arylmethylthio)-3-phenylquina-
zolin-4-one derivatives have been synthesized and their
antiplatelet aggregation activities were assessed against
ADP and arachidonic acid-induced platelet aggregation in
human plasma. Among the tested thioethers, derivative 2,
3, 5 and 16 were the most potent compounds with satis-
factory IC50 for inhibition of platelet aggregation induced
by ADP. Analysis of global physicochemical parameters
shows some correlations between activities and molecular
volume and also surface area of the studied derivatives.
In the pathogenesis of atherothrombosis, platelets play a
major role. Currently aspirin, which irreversibly inhibits
cyclooxygenase I-mediated transformation of arachidonic
acid (AA) to thromboxane A2 (TXA2), and the P2Y12
antagonists clopidogrel and prasugrel, which selectively
and irreversibly bind to the P2Y12 ADP receptor are rou-
tinely used as antiplatelet agents (Maree and Fitzgerald
2007; Meadows and Bhatt 2007). However, there are still
some serious limitations to these agents which include
weak inhibition of platelet function (e.g., aspirin) (Patrono
et al. 2004) slow onset of action (e.g., clopidogrel) (Bas-
sand 2008), variable response to treatment among patients
(e.g., clopidogrel and aspirin) (Bassand 2008; Patrono et al.
2004) and high incidence of bleeding events which is dose
dependent in both aspirin and clopidogrel drug therapy
(Guthrie 2011). Considering the current situation, devel-
opment of novel antiplatelet agents which are safe and
effective is an urgent need.
Keywords 2-(Arylmethylthio)-3-phenylquinazolin-4-one ꢀ
Antiplatelet aggregation ꢀ Thioether ꢀ Structure–activity
relationship ꢀ Adenosine diphosphate ꢀ Arachidonic acid
Introduction
Thromboembolic disorders are a major cause of death and
disability in industrial countries and also worldwide
(Mendis et al. 2011). Thrombosis that is caused secondary
to disrupted atherosclerotic plaques is the initiator of most
cardiovascular diseases including heart attacks and strokes.
Some recent works have suggested that pyrimidine
derivatives are potent antiplatelet agents (Liu et al. 2011;
Bruno et al. 2001; Crepaldi et al. 2009; Dupin et al. 2002;
Giridhar et al. 2012; Gryglewski et al. 2000). Pyrimidines
play an essential role in several biological processes and
have considerable chemical and pharmacological impor-
tance in terms that the pyrimidine ring can be found in
nucleoside antibiotics, antibacterial and cardiovascular
agents (Tozkoparan et al. 1999; Clark et al. 1993). Pyrimi-
dine, especially its thioether derivatives have attracted much
attention because of their quite high antiplatelet aggregation
activity as inhibitors for P2 receptor family (Liu et al. 2011;
Bruno et al. 2001; Crepaldi et al. 2009) (Fig. 1).
Z. Eskandariyan ꢀ M. Esfahani Zadeh ꢀ
K. Haj Mohammad Ebrahim Tehrani ꢀ
V. Mashayekhi ꢀ F. Kobarfard (&)
Department of Medicinal Chemistry, School of Pharmacy,
Shahid Beheshti University of Medical Sciences, Vali Asr
Avenue, Niayesh Junction, P.O. Box 14155-6153, Tehran, Iran
e-mail: kobarfard@sbmu.ac.ir
On the other hand, some new quinazolinone derivatives
have also shown antiplatelet activity (Gravier et al. 1992;
Ding et al. 1995; Chang et al. 2003). Quinazolinone
derivatives are of special importance because of their
F. Kobarfard
Phytochemistry Research Center, Shahid Beheshti University
of Medical Sciences, Vali Asr Avenue, Niayesh Junction,
P.O. Box 14155-6153, Tehran, Iran
123

Z. Eskandariyan et al.
SCH3
N
R1
R2
O
N
O
N
S
N
O
NH
N
N
R1
H2N
S
R
H2N
S
R
N
N
S
R
R
H
A
B
C
Fig. 1 Active antiplatelet pyrimidine derivatives. A 6-alkylamino-
2,4-dialkyl(aryl)thiopyrimidines (Liu et al. 2011), R = Me, n-Pr,
R1 = n-Pr, i-Pr, Ph, Bn, R2 = Bn, CH2CH2Ph; B tricyclic pyrimi-
dines (Bruno et al. 2001), R = some amino substituents; C substituted
6-amino-2-mercaptopyrimidines (Crepaldi et al. 2009), R = CH3,
CH2CH2NHBOC, CH2CH2OH, CH2CF3, 2-chlorobenzyl, etc.
R1 = substituted arylsulfonyl moieties
biological and pharmacological activities, such as anti
inflammatory (Laddha and Bhatnagar 2009) and antifungal
(Giri and Nizamuddin 1978) agents etc. Wu and his
coworkers in their published work investigated the anti-
platelet activity of substituted 4-quinazolinone derivatives
(Fig. 2) some of which inhibited platelet aggregation
induced by AA and collagen (Chang et al. 2003).
O
NH
H2N
N
I
S
R
O
N
N
O
Considering the structural elements of antiplatelet
pyrimidine and 4-quinazolinone derivatives, in the present
study a series of 2-(arylmethylthio)-3-phenylquinazolin-4-
one derivatives have been synthesized and their antiplatelet
activities were assessed against ADP and AA-induced
aggregation in human plasma. The synthesized derivatives
could be viewed as hybrid structures which contain both
S-substituted mercaptopyrimidines and 4-quinazolinone
structural backbones (Fig. 3). In order to study the struc-
ture–antiplatelet activity relationship of the derivatives,
different aromatic rings with diverse physicochemical and
electronic characters have been incorporated to the struc-
ture of the desired compounds.
S
NH
Ar
N
R2
R1
II
Fig. 3 General structure of 2-(arylmethylthio)-3-phenylquinazolin-4-
one derivatives
obtained using Agilent 6410 Triple Quad. Proton nuclear
magnetic resonance (1H NMR) spectra were recorded in
DMSO-d6 solution with a Bruker Avance DRX 400 MHz
spectrometer. Peak positions have been reported in parts
per million (d) downfield from tetramethylsilane as internal
standard, and J values have been given in hertz. The syn-
thesized derivatives were analyzed for C, H, N and S on a
Costech model 4010 and agreed with the proposed struc-
tures within 0.4 % of the theoretical values. The physi-
cochemical parameters including Clog P value, surface
area, molecular volume, refractivity and polarizability were
calculated by Hyperchem 8.0 software.
Materials and methods
General
Reactions were monitored by thin-layer chromatography
(TLC) on silica gel (precoated F254 Merck plates) using
chloroform/methanol as mobile phase. Melting points were
obtained by an Electrothermal 9100 apparatus and are
uncorrected. The infrared spectra (IR) were measured on a
Perkin-Elmer 843 spectrometer with KBr as diluent.
Electron spray ionization mass spectra (ESI–MS) were
Chemistry
General procedure for preparation of thioethers 2–15
To a solution of compound 1 (0.88 g, 3.49 mmol) in
35 mL of 0.1 M NaOH in CH3OH, appropriate arylmethyl
halides (3.49 mmol) were added and the solution was
stirred at room temperature. After the completion of the
reaction indicated by TLC, the developed precipitates were
filtered off, washed with water (15 mL) and recrystallized
from appropriate solvents. Compounds 2–15 were thus
prepared.
Fig. 2 Antiplatelet
4-quinazolinone derivatives.
R1 = H, OCH3, R2 = H, CH3,
O
NH
CH2CH3, phenyl,
4-methoxyphenyl
N
R2
R1
123

Antiplatelet thioether derivatives of quinazoline-4-one
2-(Benzylthio)-3-phenylquinazolin-4-one (2)
2-(4-Fluorobenzylthio)-3-phenylquinazolin-4-one (6)
Yield (50 %); mp 171–173 °C. IR (KBr, cm-1): 3055, 1683,
1543, 779, 690. H NMR (DMSO-d6): d 8.10 (1H, d, J =
Yield (66 %); mp 145–148 °C. IR (KBr, cm-1): 3065,
1683, 1551, 770. H NMR (DMSO-d6): d 8.10 (1H, d,
1
1
7.2 Hz, quinazolinone H-5), 7.87 (1H, t, J = 7.2 Hz,
quinazolinone H-7), 7.72 (1H, d, J = 8.0 Hz, quinazolinone
H-8), 7.43–7.56 (8H, m, H-20B, 30B, 40B, 50B, 60B, 20A, 60A,
quinazolinone H-6), 7.22–7.32 (3H, m, H-30A, 40A, 50A),
4.42 (2H, s, methylene H). ESI–MS m/z: 345 (M ? H?).
Anal. Calcd for C21H16N2OS: C 73.23, H 4.68, N 8.13, S
9.31. Found: C 73.31, H 4.67, N 8.10, S 9.33.
J = 7.6 Hz, quinazolinone H-5), 7.87 (1H, t, J = 7.8 Hz,
quinazolinone H-7), 7.72 (1H, d, J = 8.0 Hz, quinazoli-
none H-8), 7.55–7.59 (3H, m, H-30A, 40A, 50A), 7.48–7.52
(3H, m, H-20B, 60B, quinazolinone H-6), 7.44–7.46 (2H, m,
H-20A, 60A), 7.12 (2H, t, J = 9 Hz, H-30B, 50B), 4.41 (2H,
s, methylene H). ESI–MS m/z: 363 (M ? H?). Anal. Calcd
for C21H15FN2OS: C 69.59, H 4.17, N 7.73, S 8.85. Found:
C 69.68, H 4.16, N 7.73, S 8.87.
2-(2-Nitrobenzylthio)-3-phenylquinazolin-4-one (3)
(Lakhan 1969)
2-(3-Fluorobenzylthio)-3-phenylquinazolin-4-one (7)
Yield (82 %); mp 201–204 °C. IR (KBr, cm-1): 3124,
1723, 1581, 1556, 750. H NMR (DMSO-d6): d 8.07 (1H,
Yield (74 %); mp 134–136 °C. IR (KBr, cm-1): 3069, 1689,
1549, 783, 697. 1H NMR (DMSO-d6): d 8.10 (1H, d,
J = 7.6 Hz, quinazolinone H-5), 7.88 (1H, t, J = 7.4 Hz,
quinazolinone H-7), 7.72 (1H, d, J = 8.0 Hz, quinazolinone
H-8), 7.45–7.59 (6H, m, H-20A, 60A, quinazolinone H-6,
H-30A, 40A, 50A), 7.29–7.37 (3H, m, H-20B, 40B, 60B), 7.07
(1H, t, J = 7.8 Hz, H-50B), 4.44 (2H, s, methylene H).
ESI–MS m/z: 363 (M ? H?). Anal. Calcd for C21H15FN2OS:
C 69.59, H 4.17, N 7.73, S 8.85. Found: 69.70, H 4.16, N
7.71, S 8.88.
1
d, J = 7.6 Hz, quinazolinone H-5), 8.00 (1H, d,
J = 8.4 Hz, H-30B), 7.86–7.90 (2H, m, H-50B, quinazoli-
none H-7), 7.69–7.73 (2H, m, H-40B, 60B), 7.43–7.58 (7H,
m, H-20A, 30A, 40A, 50A, 60A, quinazolinone H-6,8), 4.72
(2H, s, methylene H). ESI–MS m/z: 390 (M ? H?). Anal.
Calcd for C21H15N3O3S: C 64.77, H 3.88, N 10.79, S 8.23.
Found: C 64.83, H 3.88, N 10.78, S 8.25.
2-(2-Chlorobenzylthio)-3-phenylquinazolin-4-one (4)
2-(2-Methylbenzylthio)-3-phenylquinazolin-4-one (8)
Yield (76 %); mp 161–163 °C. IR (KBr, cm-1): 3068,
1690, 1550, 744. H NMR (DMSO-d6): d 8.10 (1H, d,
Yield (77 %); mp 148–150 °C. IR (KBr, cm-1): 1689,
1550, 781, 697. 1H NMR (DMSO-d6): d 8.10 (1H, d,
J = 7.6 Hz, quinazolinone H-5), 7.88 (1H, t, J = 7.6 Hz,
quinazolinone H-7), 7.72 (1H, d, J = 8 Hz, H-8),
7.44–7.57 (6H, m, H-20A, 60A, quinazolinone H-6, H-30A,
40A, 50A), 7.41 (1H, d, J = 6.8 Hz, H-60B), 7.10–7.17 (3H,
m, H-30B, 40B, 50B), 4.45 (2H, s, methylene H), 2.32 (3H, s,
methyl H). ESI–MS m/z: 359 (M ? H?). Anal. Calcd for
C22H18N2OS: C 73.71, H 5.06, N 7.82, S 8.95. Found: C
73.63, H 5.08, N 7.83, S 8.94.
1
J = 7.6 Hz, quinazolinone H-5), 7.88 (1H, t, J = 7.4,
quinazolinone H-7), 7.75 (1H, d, J = 8.0 Hz, H-30B), 7.71
(1H, dd, J1 = 5.6 Hz, J2 = 3.6 Hz, H-40B), 7.55–7.58 (4H,
m, H-30A, 40A, 50A, quinazolinone H-8), 7.51 (1H, t,
quinazolinone H-6), 7.44–7.47 (2H, m, H-20A, 60A), 7.28–7.33
(2H, m, H-50B, 60B), 4.53 (2H, s, methylene H). ESI–MS
m/z: 379, 381 (M ? H?). Anal. Calcd for C21H15ClN2OS:
C 66.57, H 3.99, N 7.39, S 8.46. Found: C 66.73, H 4.01, N
7.37, S 8.48.
2-(4-Methylbenzylthio)-3-phenylquinazolin-4-one (9)
(Bhargava and Srivastava 1968)
2-(4-Nitrobenzylthio)-3-phenylquinazolin-4-one (5)
Yield (83 %); mp 162–164 °C. IR (KBr, cm-1): 1692,
1559, 774, 698. 1H NMR (DMSO-d6): d 8.10 (1H, d,
J = 6.8 Hz, quinazolinone H-5), 7.87 (1H, t, J = 7.8 Hz,
quinazolinone H-7), 7.70 (1H, d, J = 8.0 Hz, quinazoli-
none H-8), 7.48–7.57 (4H, m, quinazolinone H-6, H-30A,
40A, 50A), 7.43–7.45 (2H, m, H-20A, 60A), 7.31 (2H, d,
J = 7.6 Hz, H-20B, 60B), 7.10 (2H, d, J = 7.6 Hz, H-30B,
50B), 4.37 (2H, s, methylene H), 2.25 (3H, s, methyl H).
ESI–MS m/z: 359 (M ? H?). Anal. Calcd for C22H18
N2OS: C 73.71, H 5.06, N 7.82, S 8.95. Found: C 73.89,
H 5.07, N 7.80, S 8.97.
Yield (55 %); mp 188–200 °C. IR (KBr, cm-1): 1691,
1556, 1353, 785. H NMR (DMSO-d6): d 8.16 (2H, d,
1
J = 8.8 Hz, H-30B, 50B), 8.08 (1H, d, J = 7.2 Hz, qui-
nazolinone H-5), 7.87 (1H, t, J = 7.4 Hz, quinazolinone
H-7), 7.76 (2H, d, J = 8.4 Hz, H-20B, 60B), 7.73 (1H, d,
J = 8.4 Hz, quinazolinone H-8), 7.56–7.60 (3H, m, H-30A,
40A, 50A), 7.45–7.51 (3H, m, H-20A, 60A, quinazolinone
H-6), 4.53 (2H, s, metylene H). ESI–MS m/z: 390
(M ? H?). Anal. Calcd for C21H15N3O3S: C 64.77, H
3.88, N 10.79, S 8.23. Found: C 64.59, H 3.89, N 11.82, S
8.25.
123

Z. Eskandariyan et al.
2-(3-Methoxybenzylthio)-3-phenylquinazolin-4-one (10)
2-(2-Cyanobenzylthio)-3-phenylquinazolin-4-one. (14)
Yield (46 %); mp 123–125 °C. IR (KBr, cm-1): 1694, 1553,
783, 698. 1H NMR (DMSO-d6): d 8.10 (1H, d, J = 8.0 Hz,
quinazolinone H-5), 7.88 (1H, t, J = 7.8 Hz, quinazolinone
H-7), 7.72 (1H, d, J = 8.4 Hz, quinazolinone H-8),
7.55–7.58 (3H, m, H-30A, 40A, 50A), 7.50 (1H, t, J = 7.6 Hz,
quinazolinone H-6), 7.44–7.46 (2H, m, H-20A, 60A), 7.21
(1H, t, J = 7.8 Hz, H-50B), 7.04 (1H, s, H-20B), 7.00 (1H, d,
J = 7.6 Hz, H-60B), 6.80 (1H, d, J = 7.6 Hz, H-40B), 4.40
(2H, s, methylene H), 3.72 (3H, s, methoxy H). ESI–MS m/z:
375 (M ? H?). Anal. Calcd for C22H18N2O2S: C 70.57,
H 4.85, N 7.48, S 8.56. Found: C 70.41, H 4.86, N 7.47,
S 8.57.
Yield (83 %); mp 172–174 °C. IR (KBr, cm-1): 2240, 1694,
1555, 789. 1H NMR (DMSO-d6): d 8.08 (1H, d, J = 7.6 Hz,
quinazolinone H-5), 7.74–7.89 (4H, m, H-40B, 50B, quinaz-
olinone H-7,8), 7.66 (1H, t, J = 7.4 Hz, H-30B), 7.55–7.61
(3H, m, H-30A, 40A, 50A), 7.43–7.51 (4H, m, H-20B, 20A, 60A,
quinazolinone H-6), 4.58 (2H, s, methylene H). ESI–MS m/z:
370 (M ? H?). Anal. Calcd for C22H15N3OS: C 71.52,
H 4.09, N 11.37, S 8.68. Found: C 71.64, H 4.10, N 11.39,
S 8.65.
2-(6-Chloro-3,4-methylenedioxybenzylthio)-3-
phenylquinazolin-4-one (15)
2-(3-Methylbenzylthio)-3-phenylquinazolin-4-one (11)
Yield (88 %); mp 193–195 °C. IR (KBr, cm-1): 1681,
1556, 1045, 787. H NMR (DMSO-d6): d 8.10 (1H, d,
1
Yield (80 %); mp 138–140 °C. IR (KBr, cm-1): 1687, 889,
779, 699. 1H NMR (DMSO-d6): d 8.10 (1H, d, J = 7.2 Hz,
quinazolinone H-5), 7.87 (1H, t, J = 7.6 Hz, quinazolinone
H-7), 7.72 (1H, d, J = 8 Hz, quinazolinone H-8), 7.44–7.58
(6H, m, H-20A, 60A, quinazolinone H-6,H-30A, 40A, 50A),
7.16–7.24 (3H, m, H-20B, 50B, 60B), 7.05 (1H, d, J = 7.2 Hz,
H-40B), 4.38 (2H, s, methylene H), 2.26 (3H, s, methyl H).
ESI–MS m/z: 359 (M ? H?). Anal. Calcd for C22H18N2OS:
C 73.71, H 5.06, N 7.82, S 8.95. Found: C 73.80, H 5.06, N
7.84, S 8.98.
J = 7.6 Hz, quinazolinone H-5), 7.88 (1H, t, J = 7.6 Hz,
quinazolinone H-7), 7.76 (1H, d, J = 8.4 Hz, quinazoli-
none H-8), 7.44–7.58 (6H, m, H-20A, 60A, quinazolinone
H-6, H-30A, 40A, 50A), 7.26 (1H, s, H-40B), 7.08 (1H, s,
H-20B), 6.05 (2H, s, H-30B), 4.43 (2H, s, methylene H).
ESI–MS m/z: 423, 425 (M ? H?), 445 (M ? Na?). Anal.
Calcd for C22H15ClN2O3S: C 62.48, H 3.58, N 6.62, S 7.58.
Found: C 62.31, H 3.58, N 6.61, S 7.60.
2-(2-Carbamoylbenzylthio)-3-phenylquinazolin-4-one (16)
2-((Pyridin-3-yl)methylthio)-3-phenylquinazolin-4-one (12)
Yield (49 %); mp 161–162.2 °C. IR (KBr, cm-1): 1691,
A solution of 0.5 g of compound 14 in 2 mL of concen-
trated sulphuric acid was warmed to 80–90 °C and allowed
to stand for 5 min. Then the solution was cooled, poured
into 20 mL of cold water and filtered. The solid was stirred
with 10 mL of 5 % sodium hydroxide solution, then fil-
tered and recrystallized from ethanol.
1
1552, 695. H NMR (DMSO-d6): d 8.70 (1H, s, H-20B),
8.43 (1H, d, J = 3.6 Hz, H-40B), 8.09 (1H, d, J = 7.6 Hz,
quinazolinone H-5), 7.86–7.9 (2H, m, quinazolinone H-7,
H-60B), 7.74 (1H, d, J = 8 Hz, quinazolinone H-8),
7.45–7.57 (6H, m, H-20A, 60A, quinazolinone H-6, H-30A,
40A, 50A), 7.33 (1H, dd, J = 4.8 Hz, H-50B), 4.42 (2H, s,
methylene H). ESI–MS m/z: 346 (M ? H?). Anal. Calcd
for C20H15N3OS: C 69.54, H 4.38, N 12.17, S 9.28. Found:
C 69.44, H 4.39, N 12.21, S 9.26.
Yield (50 %); mp 231–233 °C. IR (KBr, cm-1): 3390,
1
1665, 1548, 768. H NMR (DMSO-d6): d 8.08 (1H, d,
J = 8 Hz, quinazolinone H-5), 7.87 (1H, t, J = 8.2 Hz,
quinazolinone H-7), 7.76 (1H, d, J = 8 Hz, quinazolinone
H-8), 7.65 (1H, d, J = 7.2 Hz, H-50B), 7.53–7.55 (3H, m,
H-30A, 40A, 50A), 7.38–7.52 (5H, m, H-20B, 30B, 20A, 60A,
quinazolinone H-6), 7.29–7.33 (1H, m, H-40B), 4.67 (2H, s,
methylene H). ESI–MS m/z: 388 (M ? H?). Anal. Calcd
for C22H17N3O2S: C 68.20, H 4.42, N 10.85, S 8.28.
Found: C 68.13, H 4.41, N 10.88, S 8.29.
2-((Pyridin-4-yl)methylthio)-3-phenylquinazolin-4-one (13)
Yield (58 %); mp 182–184 °C. IR (KBr, cm-1): 1691,
1
1557, 1466, 787. H NMR (DMSO-d6): d 8.49 (2H, d,
J = 6 Hz, H-30B, 50B), 8.09 (1H, d, J = 8 Hz, quinazoli-
none H-5), 7.86 (1H, t, J = 7.4 Hz, quinazolinone H-7),
7.70 (1H, d, J = 8 Hz, quinazolinone H-8), 7.56–7.58 (3H,
m, H-30A, 40A, 50A), 7.47–7.54 (5H, m, H-20A, 60A, qui-
nazolinone H-6, H-60B, 20B), 4.41 (2H, s, methylene H).
ESI–MS m/z: 346 (M ? H?), 368 (M ? Na?). Anal. Calcd
for C20H15N3OS: C 69.54, H 4.38, N 12.17, S 9.28. Found:
C 69.61, H 4.38, N 12.16, S 9.29.
In vitro evaluation of anti platelet aggregation activity
The anti platelet aggregation activity of the derivatives
were measured using human plasma. Fresh blood samples
were obtained from non-smoker healthy volunteers with
negative history of drug consumption up to 15 days prior to
the test. Platelet-rich plasma (PRP) was obtained from
whole blood collected in sodium citrate (9:1 by volume)
123

Antiplatelet thioether derivatives of quinazoline-4-one
upon centrifugation at 1,000 rpm for 8 min. The remaining
was centrifuged at 3,000 rpm for 15 min and PPP was
collected from the above layer which was used as the test
blank. The platelet count was adjusted to 250,000 plts/mL
by diluting PRP with appropriate amount of PPP. To PRP
samples, test compounds previously dissolved in ethylen-
glycol monomethyl ether were added and samples were
incubated for 5 min at 37 °C. Then ADP (5 lM) or AA
(1.25 mg/mL) was added and platelet shape change and
aggregation were monitored for 5 min. Ethylenglycol
monomethyl ether (0.5 % v/v) was used as negative control
and indomethacin and aspirin as standard drugs. Platelet
aggregation inhibition (%) was calculated by the following
formula:
were confirmed by different spectroscopic methods such as
IR, MASS and 1H NMR. In the IR spectra, a strong
absorption band at 1,680–1,690 was assigned to the cyclic
amide functionality of the quinazolinone ring which was
present in IR spectra of all the derivatives. In the spectra of
nitro-derivatives, strong absorptions at 1,375 and 1,581 (for
derivative 3) and 1,353 and 1,556 (for derivative 5) were
observed and assigned to N–O symmetric and asymmetric
stretches. Characteristic of –CN functional group, a weak
absorption band at 2,240 was observed in IR spectrum of
compound 14, which disappeared after its hydrolysis to the
1
amide derivative 16. In the H NMR spectra, as a result of
the existence of three aromatic rings, a complex spectrum
of overlapping hydrogens was observed in the aromatic
zone. However, at the upfield and downfield extremities,
quinazoline H-5 (doublet at 8.1 ppm), H-7 (triplet at
7.9 ppm) and H-8 (doublet at 7.7 ppm) and also methylene
hydrogens (singlet at 4.5 ppm) were weakly coupled and
hence more readily distinguishable. Molecular mass of all
the derivatives was detected by Electron-spray ionization
mass spectrometry (ESI–MS) as M ? 1 and/or M ? 23
relating to hydrogen and sodium adducts of the intact
molecules, respectively.
Inhibition % ¼ ½1 ꢁ ðD=SÞꢂ ꢃ 100
where D = platelet aggregation in the presence of test
compounds, and S = platelet aggregation in the presence
of solvent.
Compounds were thus screened at the primary concen-
tration of 100 lM and those that exhibited higher than
50 % inhibitory activity, were further diluted to calculate
IC50.
Antiplatelet aggregation activity
Results and discussion
The in vitro antiplatelet activity of all the synthesized
compounds was assayed on human PRP by using the
Born’s reported turbidimetric method (Born 1962) on an
APACT 4004 aggregometer. ADP and AA were employed
as inducers of platelet aggregation, and indomethacin and
aspirin were used as the positive controls. IC50 was defined
as the concentration of the test compounds that inhibits
platelet aggregation by 50 %.
Chemistry
The synthetic pathway is disclosed in Scheme 1. Final
desired derivatives were prepared by a two-step procedure.
The first step was the formation of 2,3-dihydro-3-phenyl-2-
thioxoquinazolin-4-one 1 synthesized by reacting anthra-
nilic acid with phenylisothiocyanate according to the
established procedure (Al-Rashood et al. 2006; Li et al.
2012), and in the second step compound 1 was reacted with
different aryl methyl halides under basic condition (Crep-
aldi et al. 2009). Compounds 2–15 were thus prepared in
good yields. The derivative 16 was prepared by hydrolyz-
ing compound 14 in the presence of sulfuric acid (Furniss
et al. 1989).
The antiplatelet aggregation activity of the derivatives is
listed in Table 1. Data shows that the majority of the deriv-
atives inhibited ADP-induced platelet aggregation more
effectively than the aggregation induced by AA. Among the
tested compounds, 2-(benzylthio)-3-phenylquinazolin-4-
one 2 was the most potent compound with IC50 value of
9.5 lM against aggregation induced by ADP and com-
pounds 16 and 5 showed satisfactory activity with IC50
values of 14.53 and 14.80 lM, respectively. Based on the
activity data, it could be suggested that unsubstituted phenyl
To obtain the title compounds with high purity, the
crudes prepared by the above mentioned procedure were
recrystallized from appropriate solvents and their structures
Scheme 1 The total synthetic
pathway; reagents and
O
O
conditions:
(a) phenylisothiocyanate,
triethylamine, ethanol, reflux.
(b) NaOH in methanol,
COOH
N
N
a
b
NH2
N
H
S
N
S
appropriate arylmethyl halides,
r.t
2-16
1
Ar
123

Z. Eskandariyan et al.
Table 1 Antiplatelet aggregation activity of the synthesized deriva-
tives
Table 2 General molecular parameters of the synthesized derivatives
Derivative Clog P Ra
Pb
Vc
SAd
Approx Grid
1
2.63
5.36
5.02
6.07
5.1
74.46 29.02
102.23 39.86
707.77 325.77 438.50
992.04 466.33 598.38
2
3
109.56 41.70 1022.65 458.16 590.43
107.04 41.78 1027.09 489.99 607.39
109.56 41.70 1035.41 524.99 611.39
4
5
Derivative
Ar
ADP
IC50 (lM)
AA
IC50 (lM)
6
5.5
102.45 39.77
983.56 485.18 581.20
475.15 596.98
7
5.51
5.81
5.86
5.28
5.86
3.86
3.86
4.94
6.11
3.54
102.45 39.77 1000.5
1
–
17.39
9.58
[100
[100
[100
[100
[100
[100
[100
[100
51.99
[100
[100
[100
28.7
8
107.27 41.69 1024.12 476.28 598.54
107.27 41.69 1046.01 508.11 625.93
108.69 42.33 1067.36 513.49 635.53
107.27 41.69 1027.45 513.82 604.77
2
Phenyl
9
3
2-Nitrophenyl
2-Chlorophenyl
4-Nitrophenyl
4-Fluorophenyl
3-Fluorophenyl
2-Methylphenyl
4-Methylphenyl
3-Methoxyphenyl
3-Methylphenyl
Pyridin-3-yl
15.70
34.18
14.80
28.91
[100
[100
24.80
66.60
18.36
85.05
[100
[100
21.28
10
11
12
13
14
15
16
a
4
5
100.01 39.15
100.01 39.15
945.96 401.81 552.53
962.14 463.33 571.96
6
7
107.97 41.71 1021.69 513.82 599.47
112.80 44.12 1047.65 447.41 590.58
110.81 43.13 1041.74 483.80 606.78
8
9
10
11
12
13
14
15
Refractivity
b
c
d
Polarizability
Pyridin-4-yl
Molecular volume
Surface area
2-Cyanophenyl
36.39
[100
(6-Chloro-3,4-
metylenedioxy)
phenyl
y = -1.4E-05x2 +
0.029x - 15
R² = 0.515
y = -2.8E-05x2 + 0.034x -
10
0.12
0.1
16
2-Carbamoylphenyl
14.53
[100
[100
[100
3.0
0.12
0.1
R² = 0.506
Indomethacin
Aspirin
(2)
(5)
(2)
0.08
0.06
0.04
0.02
0
30.3
0.08
0.06
0.04
0.02
0
(3)
(16)
(3)
(5)
(16)
(11)
(15)
(9)
(11)
(4)
(9)
(10)
(15)
ring (as in compound 2) is the best aromatic substituent on
position 3 of quinazoline ring among other employed ones,
since substitution on phenyl ring or replacing it by pyridine
decreases the bioactivity to variable extents. However those
with electron withdrawing substituents such as nitro and
amide groups (3, 5 and 16) showed less decreased activity. It
should be added that the activity of the latter 3 derivatives is
still acceptable and higher than their parent compound 1.
Interestingly, compounds 13 and 14 with 4-pyridyl and
2-cyano substituents were active against aggregation
induced by AA. However, the other derivatives did not show
a pronounced activity at 100 lM concentration when AA
was used as inducer.
(6)
(4)
(6)
(12)
(10)
(12)
900
1000
1100
500
550
600
650
Molecular Volume
Surface area(Grid)
Fig. 4 IC50 values plotted against surface area and molecular volume
grid) and molecular volume (V). Refractivity (R) and
polarizability (P) have been used as descriptors for both
volume and electronic state (London dispersive forces)
properties of the molecules. For each descriptor, the best
multilinear regression equation was obtained.
The calculated physicochemical parameters of the
derivatives are listed in Table 2. Analysis of the physico-
chemical parameters showed a fairly parabolic correlation
between the observed activities and surface area (grid) and
also molecular volume of the compounds (Fig. 4).
Although the correlation coefficient (R2) values do not
indicate a strong correlation (0.515 and 0.506 values,
respectively) but if the data point number 2 is considered as
an outlier, a fairly acceptable correlation will be obtained.
In order to obtain the relationship between the structural
parameters of the investigated derivatives and their anti-
platelet aggregation activity, quantitative structure–activity
relationship (QSAR) analysis was performed with various
molecular descriptors. The calculated octanol–water parti-
tion coefficient (Clog P) has been considered as descriptor
for the hydrophobic effect. The steric effect has been
described by means of the surface area (SA: approx and
123

Antiplatelet thioether derivatives of quinazoline-4-one
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respectively. According to Fig. 4, the most potent deriva-
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and molecular volume. In contrast, the derivatives that fall
into the extremities of the plots (e.g. compounds 10 and
12), exhibited weak bioactivity.
Surface area and molecular volume are two parameters
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possible receptors. The existence of a parabolic correlation
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that there may be some steric requirements on the receptor
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In conclusion, a series of 2-(arylmethylthio)-3-phe-
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