Microwave-assisted synthesis and antitumor evaluation of a new series of thiazolylcoumarin derivatives

Article abstract of DOI:10.17179/excli2017-208

A new series of thiazolylcoumarin derivatives was synthesized. The designed strategy embraced a molecular hybridization approach which involves the combination of the thiazole and coumarin pharmacophores together. The new hybrid compounds were tested for

Full text of DOI:10.17179/excli2017-208

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Original article:
MICROWAVE-ASSISTED SYNTHESIS AND ANTITUMOR
EVALUATION OF A NEW SERIES OF THIAZOLYLCOUMARIN
DERIVATIVES
Moustafa T. Gabra,b, Nadia S. El-Goharya, Eman R. El-Bendarya, Mohamed M. El-Kerdawya,
Nanting Nib
a
Department of Medicinal Chemistry, Faculty of Pharmacy, Mansoura University,
Mansoura 35516, Egypt
Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA
b

Corresponding author: Nadia S. El-Gohary, Department of Medicinal Chemistry, Faculty
of Pharmacy, Mansoura University, Mansoura 35516, Egypt; Tel.: +2 010 00326839;
Fax: +2 050 2247496; E-mail: dr.nadiaelgohary@yahoo.com
http://dx.doi.org/10.17179/excli2017-208
This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0/).
ABSTRACT
A new series of thiazolylcoumarin derivatives was synthesized. The designed strategy embraced a molecular hy-
bridization approach which involves the combination of the thiazole and coumarin pharmacophores together. The
new hybrid compounds were tested for in vitro antitumor efficacy over cervical (Hela) and kidney fibroblast (COS-
7) cancer cells. Compounds 5f, 5h, 5m and 5r displayed promising efficacy toward Hela cell line. In addition, 5h
and 5r were found to be the most active candidates toward COS-7 cell line. The four active analogs, 5f, 5h, 5m
and 5r were screened for in vivo antitumor activity over EAC cells in mice, as well as in vitro cytotoxicity toward
W138 normal cells. Results illustrated that 5r has the highest in vivo activity, and that the four analogs are less
cytotoxic than 5-FU toward W138 normal cells. In this study, 3D pharmacophore analysis was performed to in-
vestigate the matching pharmacophoric features of the synthesized compounds with trichostatin A. In silico studies
showed that the investigated compounds meet the optimal needs for good oral absorption with no expected toxicity
hazards.
Keywords: thiazolylcoumarins, synthesis, antitumor activity, cytotoxic activity, 3D pharmacophore elucidation,
in silico studies
INTRODUCTION
Histone deacetylases (HDACs) are Zn2+
dependent enzymes that catalyze the deacety-
lation of lysine residues located at the N-ε ter-
minal extensions of core histones resulting in
chromatin condensation and transcriptional
repression (Kouzarides, 2007). Eleven
isoforms of HDACs are present in human
(Gregoretti et al., 2004). Abnormalities in the
deacetylation function of histones were rec-
ognized in various human tumors (Falkenberg
and Johnstone, 2014).
Cancer is a collection of related diseases.
Cancer cells can metastasize and invade
nearby tissues through blood stream or lym-
phatic system (Bagi, 2002). In general, cancer
develops as a result of genetic changes, such
as mutations in DNA. Cancer treatment in-
cludes radiation therapy, gene therapy and
chemotherapy. Ideal anticancer agents would
kill cancer cells without affecting normal tis-
sues. Therefore, the evolution of new safe an-
ticancer agents is a serious task for medicinal
chemists.
1114

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Most HDACs inhibitors share common the active site of HDACs. The cap region in
pharmacophoric features which can be exem- the common pharmacophore has a strong con-
plified by trichostatin A, a natural HDACs in- tribution to the overall binding affinity of
hibitor. The common pharmacophore is com- HDACs inhibitors (Salisbury and Cravatt,
posed of three regions: zinc binding group 2007). The common pharmacophoric features
(ZBG) that chelates Zn2+ at the active site of of trichostatin A and the proposed thiazolyl-
the enzyme, cap group which binds to the sur- coumarin hybrids are illustrated in Figure 1.
face of the active pocket and a linker between
Literature revealed that numerous
the ZBG and the cap group (Feng et al., HDACs inhibitors have antitumor activity
2013). Literature survey revealed the signifi- (Zain et al., 2010). Most of the reported
cance of variations in the cap group (Bowers HDACs inhibitors are hydroxamic acid deriv-
et al., 2009a, b) and the linker (Weerasinghe atives that exhibit non-specific inhibition of
et al., 2008) on the HDACs inhibitory activ- all HDAC isoforms (Day and Cohen, 2013).
ity. However, the type of ZBG is believed to As a result, extensive research is directed to-
greatly affect the potency and isoform selec- ward the development of non-hydroxamate
tivity of HDACs inhibitors (Methot et al., HDACs inhibitors (Madsen et al., 2014).
2008). Hydroxamic acid moiety is a typical
Coumarins of natural and synthetic ori-
ZBG which is common in numerous HDACs gins constitute an important class of com-
inhibitors. Due to the drawbacks of hydrox- pounds. They were proved to possess signifi-
amate functional group which include non- cant therapeutic potential, including anti-
specific inhibition of all HDAC isoforms tumor activity (Morsy et al., 2017; Emami
(Day and Cohen, 2013), diverse moieties such and Dadashpour, 2015; Klenkar and Molnar,
as thiols, benzamides, sulphamides and trithi- 2015; Amin et al., 2015; Pingaew et al.,
ocarbonates were incorporated into diverse 2014b; Sandhu et al., 2014; Liu et al., 2014;
scaffolds and investigated for their capability Li et al., 2014; Seidel et al., 2014; Sashidhara
as ZBG (Chen et al., 2013; Di Micco et al., et al., 2010; Riveiro et al., 2010). On the same
2013; Kawai and Nagata, 2012). Methyl ke- line, thiazole ring is a prominent skeleton in
tone was utilized as ZBG in the design of various bioactive molecules, including anti-
HDACs inhibitors (Ilies et al., 2011). Analo- tumor compounds (Tay et al., 2017; Gomha et
gously, we introduced coumarin moiety as a al., 2015; Abouzeid and El-Subbagh, 2015;
novel ZBG in the design of new HDACs in- Nofal et al., 2014; Rouf and Tanyeli, 2015;
hibitors aiming to explore its effect as a non- Prashanth et al., 2014; Yuan et al., 2014;
hydroxamate functional group. The hydrazi- Shitre et al., 2014; Tung et al., 2013).
nylthiazole in the synthesized hybrids is im-
plied as a linker which projects the ZBG into
Figure 1: Common pharmacophoric features of trichostatin A and the proposed thiazolylcoumarin hy-
brids 5a-t
1115

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Moreover, literature survey indicated that thi- mode (Georgia State University, USA). Ele-
azolylcoumarin hybrids (Abdul Rahman et mental analyses (C, H, N) were determined,
al., 2016; Vaarla et al., 2015; Sreekanth et al., and were within ± 0.4% of the calculated val-
2014; Srimanth et al., 2002) and other ues (Georgia State University, USA). The
aryl(heteroaryl)coumarin hybrids (Zhang et completion of reactions was controlled utiliz-
al., 2017; Pangal et al., 2017; Luo et al., 2017; ing TLC plates (silica gel 60 F254, Merck)
Garazd et al., 2017; Holiyachi et al., 2016; and UV (366 nm) was used for visualization
Goel et al., 2015; Zhang et al., 2014; Kamal of the spots. Chloroform/methanol (9:1) and
et al., 2009; Ganina et al., 2008) have promis- n-hexane/ethyl acetate (3:1) were utilized as
ing antitumor activity.
elution solvents.
Hybrid approaches in drug design proved
to offer advantages in drug-resistance (Hub- Synthesis of 3-acetylcoumarin (2): Salicyl-
schwerlen et al., 2003), introducing com- aldehyde (1) (2.20 g, 18 mmol), ethyl aceto-
pounds with improved biological activity acetate (3.12 g, 24 mmol) and piperidine (0.1
(Pingaew et al., 2014a) as well as their contri- mL) were heated in ethanol (5 mL) under mi-
bution in the development of promising crowave irradiation (50 W) at 45 °C for 5 min.
agents with potent antitumor activity (Piens et The precipitated solid upon cooling was fil-
al., 2014; Romagnoli et al., 2013). Therefore, tered and crystallized from ethanol. Yield
we followed the hybridization strategy, com- 85%, m.p. 117-118 °C (Valizadeh et al.,
1
bining the thiazole and coumarin pharmaco- 2007). H NMR (DMSO-d6) δ 2.40 (s, 2H,
phores together hoping to obtain new safe an- CH2), 7.40-8.00 (m, 4H, Ar-H), 8.80 (s, 1H,
titumor compounds. In addition, the design C4-H of chromone).
strategy embraced the profiling of diverse ar-
omatic moieties (representing the cap group) Synthesis of 3-(bromoacetyl)coumarin (3):
on the thiazolylcoumarin scaffold in order to A solution of bromine (1.60 g, 20 mmol) was
study the relationship between the interaction added dropwise with constant stirring to a so-
forces of the cap group to the target receptor lution of compound 2 (2 g, 11 mmol) in chlo-
and the antitumor activity of the proposed thi- roform (15 mL). The mixture was stirred at 0-
azolylcoumarin hybrids. The new hybrid 5 °C for 6 hrs and the orange solid obtained
compounds were assessed for in vitro anti- was filtered and crystallized from glacial ace-
tumor activity, and the four active analogs, 5f, tic acid. Yield 63%, m.p. 161-162 °C (Sid-
1
5h, 5m and 5r were screened for in vivo anti- diqui et al., 2009). H NMR (DMSO-d6) δ
tumor activity over EAC in mice, as well as in 4.90 (s, 2H, CH2), 7.40-8.00 (m, 4H, Ar-H),
vitro cytotoxicity toward W138 normal cells. 8.80 (s, 1H, C4-H of chromone).
HDACs inhibitory activity of the new active
compounds is a plausible mechanism that Synthesis of 2-arylidenehydrazinocarbo-
might shed light toward the discovery of a thioamides 4a-t: Thiosemicarbazide (0.092
new class of HDACs inhibitors.
g, 1 mmol), aromatic aldehyde (1 mmol) and
glacial acetic acid (0.1 mL) were heated in
ethanol (10 mL) under microwave irradiation
(50 W) at 80 °C for 10 min. The precipitate
formed upon cooling was filtered and crystal-
lized to afford 4a-t.
MATERIALS AND METHODS
Chemistry
Stuart SMP10 melting point apparatus
was utilized to determine melting points °C.
Bruker Avance 400 MHz spectrometer was
applied for recording 1H and 13C NMR spec-
tra; chemical shifts are expressed in δ ppm
with reference to TMS (Georgia State Univer-
sity, USA). HRMS were obtained on nano
LC-Q-TOF spectrometer in +ve or -ve ion
2-(2-Bromobenzylidene)hydrazinocarbo-
thioamide (4a): Yield 84%, m.p. 202-203 °C
(Coxon et al., 2013), (ethyl acetate/ethanol
1
(3:1)), C8H8BrN3S. H NMR (DMSO-d6) δ
7.25-8.45 (m, 7H, Ar-H, NH2, CH=N), 11.65
1116

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
13
(s, 1H, NH). C NMR (DMSO-d6) δ 124.0, (DMSO-d6) δ 7.20-8.45 (m, 6H, Ar-H, NH2,
128.1, 128.2, 131.8, 133.3, 133.4, 141.2, CH=N), 11.75 (s, 1H, NH).
178.6.
2-(2-Chloro-5-nitrobenzylidene)hydrazi-
2-(2-Cyanobenzylidene)hydrazinocarbo-
nocarbothioamide (4h): Yield 79%, m.p.
thioamide (4b): Yield 91%, m.p. 212-213 °C 207-208 °C (Hao, 2010), (ethanol /water
(Hernandez et al., 2010), (chloroform), (2:1)), C8H7ClN4O2S. 1H NMR (DMSO-d6) δ
1
C9H8N4S. H NMR (DMSO-d6) δ 7.60-8.55 7.75-9.00 (m, 6H, Ar-H, CH=N, NH2), 11.80
13
(m, 7H, Ar-H, CH=N, NH2), 11.85 (s, 1H, (s, 1H, NH). C NMR (DMSO-d6) δ 125.1,
NH).
125.8, 129.6, 133.9, 141.2, 145.1, 146.9,
179.1.
2-(3-Cyanobenzylidene)hydrazinocarbo-
thioamide (4c): Yield 82%, m.p. 204-205 °C 2-(3-Bromo-4-hydroxybenzylidene)hydra-
(Hernandez et al., 2008), (ethanol/water zinocarbothioamide (4i): Yield 67%, m.p.
(2:1)), C9H8N4S. 1H NMR (DMSO-d6) δ 7.55- 169-172 °C (Tsurkan et al., 1982), (metha-
1
8.45 (m, 7H, Ar-H, CH=N, NH2), 11.60 (s, nol), C8H8BrN3OS. H NMR (DMSO-d6) δ
1H, NH). 13C NMR (DMSO-d6) δ 112.1, 6.95-8.20 (m, 6H, Ar-H, NH2, CH=N), 10.75
116.6, 130.2, 132.1, 133.7, 134.1, 134.6, (s, 1H, OH), 11.30 (s, 1H, NH).
144.3, 177.9.
2-(2-Hydroxy-5-methylbenzylidene)hydra-
2-(4-(Trifluoromethyl)benzylidene)hydra-
zinocarbothioamide (4j): Yield 72%, m.p.
zinocarbothioamide (4d): Yield 79%, m.p. 196-198 °C (Pahontu et al., 2013), (ethyl ace-
1
169-170 °C (Bernstein et al., 1951), (ethyl ac- tate/ethanol (3:1)), C9H11N3OS. H NMR
1
etate/ethanol (3:1)), C9H8F3N3S. H NMR (DMSO-d6) δ 2.20 (s, 3H, CH3), 6.70-8.30
(DMSO-d6) δ 7.75-8.45 (m, 7H, Ar-H, NH2, (m, 6H, Ar-H, NH2, CH=N), 9.50 (s, 1H,
CH=N), 11.65 (s, 1H, NH). 13C NMR OH), 11.30 (s, 1H, NH).
(DMSO-d6) δ 123.2, 125.8, 128.2, 130.0,
138.6, 144.2, 178.8.
2-(4-Hydroxy-3-methylbenzylidene)hydra-
zinocarbothioamide (4k): Yield 71%, m.p.
173-175 °C, (ethyl acetate/ethanol (3:1))
2-(3-Methylbenzylidene)hydrazinocar-
bothioamide (4e): Yield 79%, m.p. 190- (Kaishi, 1953), C9H11N3OS. 1H NMR
191 °C (Lv et al., 2010), (methanol), (DMSO-d6) δ 2.15 (s, 3H, CH3), 6.85-8.05
1
C9H11N3S. H NMR (DMSO-d6) δ 2.45 (s, (m, 6H, Ar-H, NH2, CH=N), 9.85 (s, 1H,
3H, CH3), 7.15-8.45 (m, 7H, Ar-H, NH2, OH), 11.20 (s, 1H, NH).
CH=N), 11.40 (s, 1H, NH). 13C NMR
(DMSO-d6) δ 23.6, 125.7, 127.9, 129.2, 2-(2,4-Dimethoxybenzylidene)hydrazino-
130.9, 133.6, 136.5, 144.1, 179.2.
carbothioamide (4l): Yield 69%, m.p. 221-
223 °C (Pasha et al., 2008), (ethanol/water
(2:1)), C10H13N3O2S. 1H NMR (DMSO-d6) δ
2-(2,6-Dichlorobenzylidene)hydrazinocar-
bothioamide (4f): Yield 81%, m.p. 236- 3.82 (s, 6H, 2OCH3), 6.60 (s, 2H, NH2), 7.85-
238 °C (Bernstein et al., 1951), (ethanol/wa- 8.10 (m, 3H, Ar-H), 8.35 (s, 1H, CH=N),
ter (2:1)), C8H7Cl2N3S. 1H NMR (DMSO-d6) 11.30 (s, 1H, NH).
δ 7.30-8.50 (m, 6H, Ar-H, CH=N, NH2),
11.75 (s, 1H, NH).
2-((1H-Pyrrol-2-yl)methylidene)hydra-
zinocarbothioamide (4m): Yield 84%, m.p.
2-(2-Chloro-6-fluorobenzylidene)hydrazi-
200-201 °C (Yi et al., 2011), (methanol),
1
nocarbothioamide (4g): Yield 85%, m.p. C6H8N4S. H NMR (DMSO-d6) δ 6.15-7.95
241-242 °C (Sumangala et al., 2012), (ethyl (m, 5H, pyrrole-H, NH2), 7.90 (s, 1H, CH=N),
acetate/ethanol (3:1)), C8H7ClFN3S. 1H NMR 11.20 (s, 1H, NH), 11.35 (s, 1H, NH).
1117

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
1
2-((1,1'-Biphenyl)-4-ylmethylidene)hydra-
°C, (ethyl acetate/ethanol (3:1)). H NMR
zinocarbothioamide (4n): Yield 80%, m.p. (DMSO-d6) δ 8.05-8.90 (m, 11H, Ar-H,
202-203 °C (Mendoza-Merono et al., 2010), NH2), 9.25 (s, 1H, CH=N), 11.65 (s, 1H, NH).
1
(ethanol/water (2:1)), C14H13N3S. H NMR Anal. C18H13N3S (C, H, N).
(DMSO-d6) δ 7.45-8.25 (m, 12H, Ar-H, NH2,
CH=N), 11.50 (s, 1H, NH). 13C NMR Synthesis of hydrazinothiazolylcoumarin
(DMSO-d6) δ 127.1, 127.3, 128.2, 128.3, derivatives 5a-t: 3-(Bromoacetyl)coumarin
129.4, 133.7, 139.8, 141.7, 142.3, 178.4.
(3) (0.107 g, 4 mmol), 2-arylidenehydrazino-
carbothioamides 4a-t (4 mmol) and glacial
acetic acid (0.1 mL) were heated in ethanol
2-(Naphthalen-2-ylmethylidene)hydra-
zinocarbothioamide (4o): Yield 88%, m.p. (10 mL) under microwave irradiation (60 W)
245-246 °C (Yi et al., 2011), (ethanol/water at 100 °C for 10 min. The attained solid was
1
(2:1)), C12H11N3S. H NMR (DMSO-d6) δ filtered and crystallized to give 5a-t.
7.10-8.70 (m, 10H, Ar-H, NH2, CH=N), 11.55
(s, 1H, NH).
3-(2-(2-(2-Bromobenzylidene)hydrazino)-
thiazol-4-yl)-2H-chromen-2-one (5a): Yield
75%, m.p. 212-213 °C, (ethanol/water (2:1)).
2-((1-Nitronaphthalen-2-yl)methylidene)-
hydrazinocarbothioamide (4p): Yield 77%, 1H NMR (DMSO-d6) δ 7.30-8.65 (m, 11H,
m.p. 183-185 °C, (ethyl acetate/ethanol Ar-H, C5-H of thiazole, C4-H of chromone,
1
(3:1)). H NMR (DMSO-d6) δ 7.60-8.45 (m, CH=N), 12.50 (s, 1H, NH). 13C NMR
9H, Ar-H, NH2, CH=N), 11.70 (s, 1H, NH). (DMSO-d6) δ 116.3, 119.6, 120.9, 123.1,
Anal. C12H10N4O2S (C, H, N).
125.2, 127.1, 128.6, 129.3, 129.9, 131.4,
132.2, 133.4, 133.6, 138.7, 140.2, 144.5,
152.8, 159.2, 167.9. HRMS: m/z (ESI) calcd
2-((2-Oxo-2H-chromen-6-yl)methylidene)-
hydrazinocarbothioamide (4q): Yield 71%, for C19H11BrN3O2S-, [M-H]- : 423.9749;
m.p. 276-278 °C (Datta and Daniels, 1963), found: 423.9758. Anal. C19H12BrN3O2S (C,
1
(methanol), C11H9N3O2S. H NMR (DMSO- H, N).
d6) δ 6.55-8.20 (m, 8H, Ar-H, C4-H of chro-
mone, NH2, CH=N), 11.55 (s, 1H, NH).
3-(2-(2-(2-Cyanobenzylidene)hydrazino)-
thiazol-4-yl)-2H-chromen-2-one
(5b):
2-((10-Chloroanthracen-9-yl)methyli-
Yield 69%, m.p. 219-220 °C, (ethanol/water
dene)hydrazinocarbothioamide (4r): Yield (2:1)). H NMR (DMSO-d6) δ 7.30-8.80 (m,
1
81%, m.p. 195-197 °C, (ethyl acetate/ethanol 11H, Ar-H, C5-H of thiazole, C4-H of chro-
1
13
(3:1)). H NMR (DMSO-d6) δ 7.70-8.65 (m, mone, CH=N), 12.55 (s, 1H, NH). C NMR
10H, Ar-H), 9.20 (s, 1H, CH=N), 11.85 (s, (DMSO-d6) δ 112.3, 113.6, 116.1, 120.7,
1H, NH). Anal. C16H12ClN3S (C, H, N).
123.1, 125.2, 127.3, 128.9, 129.7, 129.9,
131.7, 132.1, 132.9, 133.5, 138.2, 143.7,
145.8, 152.6, 161.3, 168.4. HRMS: m/z (ESI)
2-(Phenanthren-9-ylmethylidene)hydra-
zinocarbothioamide (4s): Yield 69%, m.p. calcd for C20H11N4O2S-, [M-H]- : 371.0581;
219-220 °C (Ebrahimi et al., 2015), (etha- found: 371.0593. Anal. C20H12N4O2S (C, H,
nol/water (2:1)), C16H13N3S. 1H NMR N).
(DMSO-d6) δ 7.65-8.95 (m, 12H, Ar-H, NH2,
CH=N), 11.55 (s, 1H, NH). 13C NMR 3-(2-(2-(3-Cyanobenzylidene)hydrazino)-
(DMSO-d6) δ 123.3, 123.9, 124.4, 127.4, thiazol-4-yl)-2H-chromen-2-one (5c): Yield
127.7, 127.9, 128.0, 128.2, 128.4, 128.7, 63%, m.p. 224-225 °C, (methanol). 1H NMR
129.4, 130.5, 130.7, 131.2, 142.0, 178.4.
(DMSO-d6) δ 7.30-8.10 (m, 10H, Ar-H), 8.55
(s, 1H, CH=N), 12.40 (s, 1H, NH). HRMS:
m/z (ESI) calcd for C20H13N4O2S+, [M+H]+:
2-(Pyren-2-ylmethylidene)hydrazinocar-
bothioamide (4t): Yield 83%, m.p. 200-202
1118

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
373.0785;
C20H12N4O2S (C, H, N).
found:
373.0766.
Anal. 7.90 (m, 8H, Ar-H, C5-H of thiazole), 8.25 (s,
1H, C4-H of chromone), 8.65 (s, 1H, CH=N),
12.50 (s, 1H, NH). 13C NMR (DMSO-d6) δ
3-(2-(2-(4-(Trifluoromethyl)benzylidene)-
hydrazino)thiazol-4-yl)-2H-chromen-2-
111.7, 115.9, 116.1, 119.6, 120.8, 120.9,
125.2, 126.7, 126.8, 129.3, 133.4, 134.7,
one (5d): Yield 72%, m.p. 189-190 °C, (eth- 138.7, 144.4, 152.8, 159.2, 159.3, 161.9,
1
anol/water (2:1)). H NMR (DMSO-d6) δ 167.9. HRMS: m/z (ESI) calcd for
7.30-8.15 (m, 9H, Ar-H, C5-H of thiazole), C19H12ClFN3O2S+,
[M+H]+:
400.0328;
8.30 (s, 1H, C4-H of chromone), 8.60 (s, 1H, found: 400.0314. Anal. C19H11ClFN3O2S (C,
CH=N), 12.45 (s, 1H, NH). 13C NMR H, N).
(DMSO-d6) δ 111.5, 116.3, 119.6, 120.9,
125.2, 126.1, 126.2, 127.4, 129.2, 129.3, 3-(2-(2-(2-Chloro-5-nitrobenzylidene)hy-
132.2, 138.7, 140.3, 144.5, 152.7, 159.2, drazino)thiazol-4-yl)-2H-chromen-2-one
159.3, 167.9. HRMS: m/z (ESI) calcd for (5h): Yield 74%, m.p. 176-177 °C, (etha-
C20H11F3N3O2S-, [M-H]- : 414.0535; found: nol/water (2:1)). 1H NMR (DMSO-d6) δ 7.30-
414.0541. Anal. C20H12F3N3O2S (C, H, N).
8.65 (m, 10H, Ar-H, C5-H of thiazole, C4-H
of chromone, CH=N), 12.70 (s, 1H, NH). 13C
NMR (DMSO-d6) δ 112.3, 120.9, 123.1,
3-(2-(2-(3-Methylbenzylidene)hydrazino)-
thiazol-4-yl)-2H-chromen-2-one (5e): Yield 125.4, 125.7, 126.9, 127.2, 128.4, 129.3,
82%, m.p. 190-191 °C, (ethyl acetate/ethanol 129.9, 133.7, 138.1, 141.0, 142.8, 145.9,
1
(3:1)). H NMR (DMSO-d6) δ 2.30 (s, 3H, 146.2, 151.3, 161.6, 169.2. HRMS: m/z (ESI)
CH3), 7.15-8.05 (m, 9H, Ar-H, C5-H of thia- calcd for C19H12ClN4O4S+, [M+H]+:
zole), 8.30 (s, 1H, C4-H of chromone), 8.52 427.0246;
found:
427.0267.
Anal.
(s, 1H, CH=N), 12.20 (s, 1H, NH). 13C NMR C19H11ClN4O4S (C, H, N).
(DMSO-d6) δ 21.4, 111.1, 116.3, 119.6,
120.9, 121.6, 124.1, 125.2, 127.1, 129.2, 3-(2-(2-(3-Bromo-4-hydroxybenzylidene)-
129.3, 130.5, 132.1, 138.5, 138.6, 142.3, hydrazino)thiazol-4-yl)-2H-chromen-2-
144.4, 152.7, 159.2, 168.1. HRMS: m/z (ESI) one (5i): Yield 80 %, m.p. 182-184 °C, (ethyl
calcd for C20H14N3O2S-, [M-H]- : 360.0800; acetate/ethanol (3:1)). 1H NMR (DMSO-d6) δ
found: 360.0813. Anal. C20H15N3O2S (C, H, N). 7.00-8.85 (m, 10H, Ar-H, C5-H of thiazole,
C4-H of chromone, CH=N), 10.85 (s, 1H,
3-(2-(2-(2,6-Dichlorobenzylidene)hydra-
OH), 12.05 (s, 1H, NH). HRMS: m/z (ESI)
zino)thiazol-4-yl)-2H-chromen-2-one (5f): calcd for C19H11BrN3O3S-, [M-H]-
:
Yield 81%, m.p. 230-232 °C, (chloroform). 439.9685;
found:
439.9698.
Anal.
1H NMR (DMSO-d6) δ 7.30-7.90 (m, 8H, Ar- C19H12BrN3O3S (C, H, N).
H, C5-H of thiazole), 8.30 (s, 1H, C4-H of
chromone), 8.60 (s, 1H, CH=N), 12.50 (s, 1H, 3-(2-(2-(2-Hydroxy-5-methylbenzylidene)-
NH). 13C NMR (DMSO-d6) δ 111.7, 116.3, hydrazino)thiazol-4-yl)-2H-chromen-2-
119.6, 120.9, 125.1, 125.3, 129.3, 130.9, one (5j): Yield 84%, m.p. 206-207 °C, (ethyl
132.1, 134.0, 136.8, 139.7, 144.4, 152.8, acetate/ethanol (3:1)). 1H NMR (DMSO-d6) δ
159.2, 159.3, 167.9. HRMS: m/z (ESI) calcd 2.20 (s, 3H, CH3), 6.80-7.90 (m, 8H, Ar-H,
for C19H12Cl2N3O2S+, [M+H]+: 416.0034; C5-H of thiazole), 8.30 (s, 1H, C4-H of chro-
found: 416.0030. Anal. C19H11Cl2N3O2S (C, mone), 8.55 (s, 1H, CH=N), 9.80 (s, 1H, OH),
H, N).
12.15 (s, 1H, NH). 13C NMR (DMSO-d6) δ
20.6, 110.8, 116.3, 116.5, 119.6, 120.1, 120.9,
125.2, 126.7, 128.4, 129.3, 131.8, 132.1,
138.6, 140.6, 144.6, 152.8, 154.4, 159.2,
3-(2-(2-(2-Chloro-6-fluorobenzylidene)hy-
drazino)thiazol-4-yl)-2H-chromen-2-one
(5g): Yield 69%, m.p. 195-196 °C, (etha- 167.8. HRMS: m/z (ESI) calcd for
nol/water (2:1)). 1H NMR (DMSO-d6) δ 7.25-
1119

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
C20H14N3O3S-, [M-H]- : 376.0781; found: NH). 13C NMR (DMSO-d6) δ 111.2, 116.4,
376.0771. Anal. C20H15N3O3S (C, H, N).
119.6, 121.0, 125.2, 127.1, 127.4, 127.5,
128.3, 129.3, 129.5, 132.2, 133.8, 138.7,
139.8, 141.3, 141.8, 144.5, 152.8, 159.3,
168.2. HRMS: m/z (ESI) calcd for
3-(2-(2-(4-Hydroxy-3-methylbenzylidene)-
hydrazino)thiazol-4-yl)-2H-chromen-2-
one (5k): Yield 71%, m.p. 193-194 °C, (eth- C25H16N3O2S-, [M-H]- : 422.0955; found:
anol/water (2:1)). 1H NMR (DMSO-d6) δ 2.15 422.0959. Anal. C25H17N3O2S (C, H, N).
(s, 3H, CH3), 6.80 (s, 1H, C5-H of thiazole),
7.25-7.95 (m, 8H, Ar-H, C4-H of chromone), 3-(2-(2-(Naphthalen-2-ylmethylidene)hy-
8.50 (s, 1H, CH=N), 9.75 (s, 1H, OH), 11.90 drazino)thiazol-4-yl)-2H-chromen-2-one
(s, 1H, NH). HRMS: m/z (ESI) calcd for (5o): Yield 79%, m.p. 225-227 °C, (ethyl ac-
1
C20H14N3O3S-, [M-H]- : 376.0781; found: etate/ethanol (3:1)). H NMR (DMSO-d6) δ
376.0765. Anal. C20H15N3O3S (C, H, N).
7.30-8.60 (m, 14H, Ar-H, C5-H of thiazole,
C4-H of chromone, CH=N), 12.30 (s, 1H,
NH). HRMS: m/z (ESI) calcd for
C23H14N3O2S-, [M-H]- : 396.0812; found:
3-(2-(2-(2,4-Dimethoxybenzylidene)-hy-
drazino)thiazol-4-yl)-2H-chromen-2-one
(5l): Yield 79%, m.p. 219-220 °C, (chloro- 396.0795. Anal. C23H15N3O2S (C, H, N).
1
form). H NMR (DMSO-d6) δ 3.80 (s, 3H,
OCH3), 3.86 (s, 3H, OCH3), 6.65-8.55 (m, 3-(2-(2-((1-Nitronaphthalen-2-yl)methyli-
10H, Ar-H, C5-H of thiazole, C4-H of chro- dene)hydrazino)thiazol-4-yl)-2H-
13
mone, CH=N), 11.90 (s, 1H, NH). C NMR chromen-2-one (5p): Yield 63%. m.p. 211-
(DMSO-d6) δ 56.1, 56.2, 102.3, 106.3, 111.3, 213 °C, (chloroform). 1H NMR (DMSO-d6) δ
115.6, 120.6, 121.8, 125.9, 126.6, 128.2, 7.35-8.25 (m, 12H, Ar-H, C5-H of thiazole,
129.6, 132.3, 136.7, 144.1, 146.4, 151.3, C4-H of chromone), 8.55 (s, 1H, CH=N),
159.6, 161.3, 163.5, 169.1. HRMS: m/z (ESI) 12.75 (s, 1H, NH). 13C NMR (DMSO-d6) δ
calcd for C21H18N3O4S+, [M+H]+: 408.1037; 113.2, 115.9, 121.1, 123.6, 124.2, 125.1,
found: 408.1025. Anal. C21H17N3O4S (C, H, 125.7, 126.3, 127.3, 127.6, 128.4, 128.9,
N).
129.5, 129.8, 135.2, 137.4, 142.9, 144.6,
145.9, 147.2, 154.3, 162.2, 171.7. HRMS: m/z
(ESI) calcd for C23H13N4O4S-, [M-H]- :
3-(2-(2-((1H-Pyrrol-2-yl)methylidene)hy-
drazino)thiazol-4-yl)-2H-chromen-2-one
441.0663;
found:
441.0660.
Anal.
(5m): Yield 62%, m.p. 167-168 °C, (chloro- C23H14N4O4S (C, H, N).
1
form). H NMR (DMSO-d6) δ 6.10-6.90 (m,
4H, pyrrole-H, C5-H of thiazole), 7.30-7.95 6-((2-(4-(2-Oxo-2H-chromen-3-yl)thiazol-
(m, 5H, Ar-H, C4-H of chromone), 8.55 (s, 2-yl)hydrazono)methyl)-2H-chromen-2-
1H, CH=N), 11.30 (s, 1H, NH), 11.85 (s, 1H, one (5q): Yield 76%, m.p. 181-183 °C, (eth-
NH). 13C NMR (DMSO-d6) δ 111.3, 113.7, anol/water (2:1)). 1H NMR (DMSO-d6) δ 6.50
116.6, 120.3, 120.9, 125.1, 125.6, 128.1, (d, 1H, C3-H of chromone), 7.30-8.15 (m,
128.6, 129.7, 133.1, 139.4, 145.2, 146.3, 10H, Ar-H, C5-H of thiazole, C4-H of two
155.4, 162.1, 170.9. HRMS: m/z (ESI) calcd chromone moieties), 8.55 (s, 1H, CH=N),
for C17H11N4O2S-, [M-H]- : 335.0610; found: 12.25 (s, 1H, NH). 13C NMR (DMSO-d6) δ
335.0619. Anal. C17H12N4O2S (C, H, N).
111.2, 116.3, 117.2, 117.5, 119.5, 119.6,
120.9, 125.2, 126.7, 129.2, 129.7, 131.2,
132.2, 138.6, 140.6, 144.5, 151.9, 152.7,
154.3, 159.2, 160.1, 168.0. HRMS: m/z (ESI)
3-(2-(2-((1,1'-Biphenyl)-4-ylmethylidene)-
hydrazino)thiazol-4-yl)-2H-chromen-2-
one (5n): Yield 77%, m.p. 198-200 °C, (ethyl calcd for C22H12N3O4S-, [M-H]- : 414.0560;
acetate/ethanol (3:1)). 1H NMR (DMSO-d6) δ found: 414.0565. Anal. C22H13N3O4S (C, H,
7.30-8.65 (m, 16H, Ar-H, C5-H of thiazole, N).
C4-H of chromone, CH=N), 12.25 (s, 1H,
1120

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
3-(2-(2-((10-Chloroanthracen-9-yl)-me-
thylidene)hydrazino)thiazol-4-yl)-2H-
In vitro antitumor assay
The new analogs were tested for in vitro
chromen-2-one (5r): Yield 86%, m.p. 238- antitumor efficacy adopting the reported pro-
240 °C, (ethanol/water (2:1)). 1H NMR cedure (Mosmann, 1983; Denizot and Lang,
(DMSO-d6) δ 7.20-8.75 (m, 15H, Ar-H, C5-H 1986; Gerlier and Thomasset, 1986).
of thiazole, C4-H of chromone, CH=N), 12.50
In vivo antitumor assay
13
(s, 1H, NH). C NMR (DMSO-d6) δ 111.3,
In vivo antitumor assessment of 5f, 5h, 5m
116.4, 120.4, 122.5, 125.1, 125.2, 125.9,
and 5r was performed according to the litera-
126.7, 127.8, 128.4, 128.8, 129.3, 130.1,
ture method (Oberling and Guerin, 1954;
132.5, 134.0, 138.8, 140.1, 142.3, 152.0,
Sheeja et al., 1997; Clarkson and Burchenal,
164.2, 168.0. HRMS: m/z (ESI) calcd for
1965).
C27H15ClN3O2S-, [M-H]- : 480.0574; found:
In vitro cytotoxicity testing
480.0574. Anal. C27H16ClN3O2S (C, H, N).
In vitro cytotoxic activity of 5f, 5h, 5m
and 5r was evaluated in accord to the reported
method (Mosmann, 1983; Denizot and Lang,
1986; Gerlier and Thomasset, 1986).
3-(2-(2-(Phenanthren-9-ylmethylidene)-
hydrazino)thiazol-4-yl)-2H-chromen-2-
one (5s): Yield 87%, m.p. 245-247 °C, (chlo-
1
roform). H NMR (DMSO-d6) δ 7.30-8.20
RESULTS AND DISCUSSION
(m, 11H, Ar-H, C5-H of thiazole, C4-H of
chromone, CH=N), 8.55-9.10 (m, 5H, Ar-H),
12.45 (s, 1H, NH). HRMS: m/z (ESI) calcd for
C27H16N3O2S-, [M-H]- : 446.0941; found:
446.0960. Anal. C27H17N3O2S (C, H, N).
Chemistry
3-(Bromoacetyl)coumarin (3) was synthe-
sized via a two step procedure (Figure 2).
First, cyclocondensation of salicylaldehyde
(1) and ethyl acetoacetate under microwave
irradiation utilizing piperidine as a catalyst to
give the 3-acetylcoumarin (2) (Valizadeh et
al., 2007). Second, bromination of compound
2 in chloroform to yield the bromoketone 3 in
63% yield (Siddiqui et al., 2009) (Figure 2).
The 2-arylidenehydrazinocarbothioamides
4a-t were synthesized through condensation
of the aromatic aldehydes and thiosemicarba-
zide in ethanol under microwave irradiation
(Figure 3). Microwave irradiation of 4a-t and
bromoketone 3 in ethanol, followed by addi-
tion of ammonium hydroxide 5%, furnished
the desired thiazolylcoumarin hybrids 5a-t in
moderate to good yields (62-89%) (Figure 3).
3-(2-(2-(Pyren-2-ylmethylidene)hydra-
zino) thiazol-4-yl)-2H-chromen-2-one (5t):
Yield 89%, m.p. 237-239 °C, (ethanol/water
1
(2:1)). H NMR (DMSO-d6) δ 7.35-9.00 (m,
16H, Ar-H, C5-H of thiazole, C4-H of chro-
mone, CH=N), 12.50 (s, 1H, NH). HRMS:
m/z (ESI) calcd for C29H16N3O2S-, [M-H]- :
470.0975;
found:
470.0979.
Anal.
C29H17N3O2S (C, H, N).
Biology
Detailed biological screening methods are
provided in the supplementary information.
Figure 2: Synthesis of 3-(bromoacetyl)coumarin (3)
1121

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Figure 3: Synthesis of thiazolylcoumarin hybrids 5a-t
Biological screening
pounds 5f, 5h, 5m and 5r exhibited remarka-
ble activity against Hela cell line. In addition,
5h and 5r displayed outstanding efficacy to-
ward COS-7 cell line (Table 1). The rest of the
tested compounds displayed weaker efficacy.
In vitro antitumor screening
In vitro antitumor screening of com-
pounds 5a-t was carried out on cervical
(Hela) and kidney fibroblast (COS-7) cancer
cell lines in accord to MTT assay (Mosmann, Structure-activity relationship
1983; Denizot and Lang, 1986; Gerlier and
Compound 5f incorporating 2,6-dichloro-
Thomasset, 1986) and utilizing doxorubicin phenyl moiety displayed prominent antitumor
as a standard drug. The concentrations of the efficacy toward Hela cell line and it repre-
compounds that cause 50% inhibition of cell sents the basic framework for further struc-
viability (IC50, µM) were calculated. Com- tural modifications. Replacing this moiety
with 2-chloro-6-fluorophenyl counterpart
1122

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Table 1: In vitro antitumor activity of 5a-t toward Hela and COS-7 cancer cell lines
Comp. No.
IC50 (µM)
Comp. No.
IC50 (µM)
Hela
COS-7
Hela
COS-7
5a
5b
5c
5d
5e
5f
5g
5h
5i
>50
>50
>50
>50
>50
1.90
>50
1.42
>50
>50
>50
>50
>50
>50
>50
>50
>50
1.96
>50
>50
5l
5m
5n
5o
5p
5q
5r
5s
5t
>50
6.25
>50
>50
>50
>50
1.29
>50
>50
2.05
>50
12.50
>50
>50
>50
>50
1.66
>50
>50
3.04
5j
Doxorubicin
5k
>50
>50
--------
--------
--------
Bold values refer to the good results
abolished the activity against the same cell where MST = days of the mouse in a
line (compound 5g), whereas its replacement group/total no. of mice. Compound 5r dis-
with 2-chloro-5-nitrophenyl counterpart led played prominent increase in lifespan of mice
to increased efficacy toward the same cell line (Table 2). Also, this compound produced con-
and a tremendous improvement in the activity siderable decrease in viable tumor cell count
toward COS-7 cell line (compound 5h). In- (Table 3). Regarding the effect on blood pro-
corporation of pyrrol-2-yl moiety into the thi- file, compound 5r showed higher Hb and
azolylcoumarin resulted in considerable effi- RBC levels and lower WBC count than 5-FU
ciency toward Hela and COS-7 cell lines (Table 4).
which might be attributed to additional inter-
action with the target receptor (compound
5m). 10-Chloroanthracen-9-yl moiety was
proved to exhibit the optimum hydrophobic
binding affinity and displayed the most potent
antitumor efficacy against both cell lines
(compound 5r).
Table 2: Effect of 5f, 5h, 5m and 5r on mean sur-
vival time and % increase in lifespan of mice inoc-
ulated with EAC cells
Group
Mean survival
time (day)
nda
% Increase
in lifespan
nda
Normal
EAC only
14.5
nda
5f
5h
41.0
39.3
182.7
171.0
In vivo antitumor screening
Results of in vivo antitumor screening of
compounds 5f, 5h, 5m and 5r (showing the
highest in vitro antitumor activity) against
EAC cells in mice are listed in Tables 2-4.
The % increase in lifespan of EAC inoculated
mice (%ILS), the decrease in viable tumor
cell count and the retrieval of normal blood
profile are three substantial measures used for
estimation of antitumor efficacy of the se-
lected compounds and 5-fluorouracil (5-FU)
(standard agent) (Oberling and Guerin, 1954;
Sheeja et al., 1997; Clarkson and Burchenal,
1965). The mean survival time (MST) of each
group was rated and %ILS of mice inoculated
with EAC cells was determined adopting the
equation: %ILS = [(MST of treated group/
MST of positive control group)-1] x 100,
5m
5r
37.0
45.5
49.0
155.2
213.8
237.9
5-Fluorouracil
a nd: not determined.
Bold values refer to the good results.
Table 3: Effect of 5f, 5h, 5m and 5r on tumor vol-
ume and viable tumor cell count of mice inocu-
lated with EAC cells
Group
Tumor vol- Viable tumor cell
ume (mL)
count/100 μL
Normal
EAC only
nda
nda
9.85
2.62
3.12
3.85
2.11
1.60
83.20x106
25.83x106
32.57x106
40.52x106
21.94x106
20.17x106
5f
5h
5m
5r
5-Fluorouracil
a nd: not determined.
Bold values refer to the good results.
1123

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Table 4: Effect of 5f, 5h, 5m and 5r on blood pro-
file of mice inoculated with EAC cells
Based on this assumption, analysis of the mo-
lecular recognitions in the biological target in-
teracting with the lead compound will enable
the design of more potent analogs.
Group
Hb
RBCs
Count
WBCs
Count
(g/dl)
106/mm3 103/mm3
LigandScout software allows accurate vir-
tual screening based on 3D pharmacophore
models, and it is utilized to produce a pharma-
cophore for trichostatin A (Wolber and
Langer, 2005). The model (Figure 4) was gen-
erated by overlaying the pharmacophoric fea-
tures of HDAC8 domain complexed with tri-
Normal
EAC only
13.73
8.15
5.84
3.69
5.14
4.92
4.39
5.55
5.21
5.99
23.96
8.41
9.25
9.61
7.45
8.86
5f
5h
5m
5r
12.92
11.97
11.43
13.10
12.96
5-Fluorouracil
Bold values refer to the good results.
chostatin
A
(PDB ID: 1T64) (PDB;
http://www.rcsb.org/pdb/home/home.do).
The pharmacophore created by Lig-
andScout revealed the presence of one hydro-
gen bond acceptor site (red arrow) embedded
between five hydrophobic regions repre-
sented by yellow spheres which conveys the
tremendous contribution of hydrophobic in-
teractions with the receptor. Moreover, ZBG
represented by a blue conical shape, was ori-
ented at the terminal of the hydrophobic re-
gions and is proposed to be an essential fea-
ture in the presented pharmacophore. The
four active antitumor compounds in this
study, 5f, 5h, 5m and 5r were subjected to a
pharmacophore-based virtual screening
against the target pharmacophore of tri-
chostatin A. The matching pharmacophoric
features between the active compounds and
trichostatin A are identified in Table 6. All the
active compounds attained a ZBG, a hydro-
gen bond acceptor site and at least two sites
for hydrophobic interactions matching the
orientation exhibited by the target pharmaco-
phore. In addition, a relative pharmacophore
score illustrated in Table 6 was calculated for
each compound. Compounds 5f and 5r exhib-
ited the highest relative pharmacophore score
of 0.76 and 0.81, respectively. Figures 5A and
6A illustrate the 3D alignments of 5f and 5r,
respectively with the pharmacophore model.
2D Mappings of the pharmacophore model
with 5f and 5r are shown in Figures 5B and
6B, respectively. The proposed pharmaco-
phore of HDAC8 revealed that hydrophobic
forces represent the major contributing inter-
action with the compounds, accordingly,
LeadIT program was utilized to examine the
In vitro cytotoxicity testing
The effective antitumor compounds, 5f,
5h, 5m and 5r were further assessed for in
vitro cytotoxicity toward human normal lung
fibroblast (W138) cell line (Mosmann, 1983;
Denizot and Lang, 1986; Gerlier and Thomas-
set, 1986). IC50 values (µM) of the tested
compounds and 5-FU (reference cytotoxic
agent) were calculated. Results (Table 5) re-
vealed that the four tested compounds are less
cytotoxic than 5-FU. Comparing the IC50 val-
ues of 5h, 5m and 5r on the tested normal cell
line (19.75-29.47 µM) with those on the
tested cancer cell lines (1.29-12.50 µM), we
can conclude that the three compounds are
more selective cytotoxic agents toward cancer
cells than normal cells. In addition, 5f was
found to be more selective toward Hela can-
cer cell line (IC50 = 1.90 µM) than W138 nor-
mal cell line (IC50 = 36.21 µM).
Table 5: In vitro cytotoxic activity of 5f, 5h, 5m and
5r toward W138 normal cell line
Comp. No.
IC50 (µM)
5f
5h
5m
5r
36.21
19.75
29.47
24.32
5.73
5-Fluorouracil
3D Pharmacophore elucidation
A pharmacophore is a set of common
structural features shared by a group of com-
pounds that interacts with the complementary
sites on a specific target leading to biological
activity (Rodolpho and Andrade, 2013).
1124

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
hydrophobic interaction of the active analogs In silico studies
with the target receptor (Stahl and Rarey, Computational chemists follow different
2001). The lipophilic area of each compound approaches for estimation of molecular diver-
exposed toward HDAC8 domain was given a sity. Drug-likeness is a qualitative notion used
score (Table 6). Compounds 5f and 5r at- to study how a particular substance is "drug-
tained the highest lipophilic area score of - like". So, computer softwares were utilized
14.12 and -14.65, respectively. 2D Interac- for predicting the drug-likeness of the new
tions of 5f and 5r with HDAC8 domain are drugs (Ursu et al., 2011). The most active
presented in Figures 7 and 8, respectively.
compounds, 5f, 5h, 5m and 5r were studied
for the expectation of Lipinski’s rule
(Lipinski et al., 2001) along with other molec-
ular properties.
Table 6: Results of pharmacophore analysis of 5f, 5h, 5m and 5r
Comp. No.
Matching Features
Relative Pharmacophore Lipophilic Area
Score
Score
5f
0.76
-14.12
5h
0.56
0.54
-13.71
-12.31
5m
5r
0.81
-14.65
Trichostatin A
1.00
-14.71
: Hydrophobic region;
: Zinc binding group;
: Hydrogen acceptor
Bold values refer to the good results.
Figure 4: A. LigandScout 3D proposed docking pose for trichostatin A in HDAC8 domain (PDB ID:
1T64). B. 3D Pharmacophore of trichostatin A (in ball and stick presentation); The pharmacophore color
coding is red for hydrogen acceptor, yellow for hydrophobic regions, and blue for zinc binding group. C.
2D Representation of the pharmacophoric features of trichostatin A. D. The 3D pharmacophore model
for HDAC8 domain (PDB ID: 1T64). The pharmacophore color coding is red for hydrogen acceptor,
yellow for hydrophobic regions, and blue for zinc binding group
1125

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Figure 5: The 3D and 2D alignments of 5f with HDAC8 pharmacophore model. A. 3D Alignment of 5f
with HDAC8 pharmacophore model. The pharmacophore color coding is red for hydrogen acceptors,
yellow for hydrophobic regions and blue for zinc binding groups. B. 2D Representation of structural
features of 5f that can be aligned with the pharmacophore hypothesis. HBA; hydrogen bond acceptor
and H; hydrophobic center
Figure 6: The 3D and 2D alignments of 5r with HDAC8 pharmacophore model. A. 3D Alignment of 5r
with HDAC8 pharmacophore model. The pharmacophore color coding is red for hydrogen acceptors,
yellow for hydrophobic regions and blue for zinc binding groups. B. 2D Representation of structural
features of 5r that can be aligned with the pharmacophore hypothesis. HBA; hydrogen bond acceptor
and H; hydrophobic center
Figure 8: 2D Interaction of 5r with HDAC8 do-
Figure 7: 2D Interaction of 5f with HDAC8 do-
main. Hydrogen bonds are shown by dashed
main. Hydrogen bonds are shown by dashed
lines. Green solid lines represent hydrophobic in-
lines. Green solid lines represent hydrophobic in-
teractions
teractions
1126

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Molinspiration calculations
CONCLUSION
Lipinski’s rule is related to drug absorp-
tion (Lipinski et al., 2001). Also, topological
polar surface area (TPSA) and number of ro-
tatable bonds (Nrotb) influence oral absorp-
tion of drugs (Veber et al., 2002).
TPSA, Nrotb, and the parameters of
Lipinski’s rule for the effective analogs, 5f,
5h, 5m and 5r were evaluated using molinspi-
ration software.
Results illustrated that all examined ana-
logs have zero or one violation of Lipinski’s
rule, as well as TPSA values and Nrotb under
the acceptable norms; therefore, they are an-
ticipated to be well absorbed (Table 7).
The recent study led to the development
of new efficient antitumor thiazolylcoumarin
derivatives. Compounds 5f, 5h, 5m and 5r are
the most active antitumor analogs toward
Hela cell line; in addition, 5h and 5r dis-
played eminent activity toward COS-7 cell
line. Moreover, 5r displayed the highest in
vivo activity. Furthermore, the four active an-
alogs were proved to be less cytotoxic than 5-
FU on W138 normal cells; therefore, they
might be used as potent antitumor agents with
low toxicity toward normal cells. Further
mechanistic and kinetic investigations con-
cerning the HDACs inhibitory activity of
these active compounds will shed light on
Drug-likeness
Osiris software (Jarrahpour et al., 2011) possible structural modifications desired to
was applied for studying the toxicity hazards obtain new more active antitumor agents.
(mutagenicity, tumorigenicity, irritation & re-
Acknowledgments
productive effects) and drug-likeness of the
analyzed compounds. Results revealed that all
the analyzed analogs are expected to have no
toxicity hazards. It is well established that
molecules containing fragments which are ex-
tremely available in commercial drugs, have
positive drug-likeness values. Results listed in
Table 7 showed that 5f, 5m and 5r have posi-
tive drug-likeness values, and they are ex-
pected to have fragments which are available
in commercial drugs.
The authors extend their appreciation to
Professor Binghe Wang, Georgia State Uni-
versity, USA, for offering the facilities
needed for performing spectral analysis and in
vitro antitumor testing. Thanks to Mr. Ahmed
Abbas, Faculty of Pharmacy, Mansoura Uni-
versity, Egypt, for assessment of in vivo anti-
tumor and in vitro cytotoxic activities.
Table 7: TPSA, Nrotb, calculated Lipinski’s rule and drug-likeness of 5f, 5h, 5m and 5r
Comp. No.
Drug-
Molecular properties
likeness
TPSA
Nrotb miLogP nOH-NH nO-N
M. wt.
No. of
violations
1
5f
5h
5m
5r
67.49
113.32
83.28
67.49
4
5
4
4
5.22
4.53
3.12
6.86
1
1
2
1
5
8
6
5
416.29
426.84
336.38
481.96
6.17
-1.13
5.43
5.23
0
0
1
1127

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Denizot F, Lang R. Rapid colorimetric assay for cell
REFERENCES
growth and survival. Modifications to the tetrazolium
dye procedure giving improved sensitivity and reliabil-
ity. J Immunol Methods. 1986;89:271-7.
Abdul Rahman FS, Yusufzai SK, Osman H, Mohamad
D. Synthesis, characterisation and cytotoxicity activity
of thiazole substitution of coumarin derivatives (Char-
acterisation of coumarin derivatives). J Phys Sci.
2016;27:77-87.
Di Micco S, Chini M G, Terracciano S, Bruno I, Riccio
R, Bifulco G. Structural basis for the design and syn-
thesis of selective HDAC inhibitors. Bioorg Med
Chem. 2013;21:3795-807.
Abouzeid LA, El-Subbagh HI. DNA binding of ethyl
2-substituted aminothiazole-4-carboxylate analogues:
A molecular modeling approach to predict their anti-
tumor activity. Future J Pharm Sci. 2015;1:1-7.
Ebrahimi HP, Hadi JS, Alsalim TA, Ghali TS, Boland-
nazar Z. A novel series of thiosemicarbazone drugs:
From synthesis to structure. Spectrochim. Acta Mol Bi-
omol Spectrosc. 2015;137:1067-77.
Amin KM, Abou-Seri SM, Awadallah FM, Eissa AM,
Hassan GS, Abdulla MM. Synthesis and anticancer ac-
tivity of some 8-substituted-7-methoxy-2H-chromen-
2-one derivatives toward hepatocellular carcinoma
HepG2 cells. Eur J Med Chem. 2015;90:221-31.
Emami S, Dadashpour S. Current developments of
coumarin based anti-cancer agents in medicinal chem-
istry. Eur J Med Chem. 2015;102:611-30.
Bagi CM. Cancer cell metastasis session. J Musculo-
skel Neuron Interact. 2002;2:579-80.
Falkenberg KJ, Johnstone RW. Histone deacetylases
and their inhibitors in cancer, neurological diseases and
immune disorders. Nat Rev Drug Discov. 2014;13:
673-91.
Bernstein J, Yale HL, Losee K, Holsing M, Martins J,
Lott WA. The chemotherapy of experimental tubercu-
losis. 111. The synthesis of thiosemicarbazones and re-
lated compounds. J Am Chem Soc. 1951;73:906-12.
Feng T, Wang H, Su H, Lu H, Yu L, Zhang X, et al.
Novel
N-hydroxyfurylacrylamide-based
histone
deacetylase (HDAC) inhibitors with branched CAP
group (Part 2). Bioorg Med Chem. 2013;21:5339-54.
Bowers AA, Greshock TJ, West N, Estiu G, Schreiber
SL, Wiest O, Williams RM, Bradner JE. Synthesis and
conformation-activity relationships of the peptide
isosteres of FK228 and largazole. J Am Chem Soc.
2009a;131:2900-5.
Ganina OG, Daras E, Bourgarel-Rey V, Peyrot V, An-
dresyuk AN, Finet JP, et al. Synthesis and biological
evaluation of polymethoxylated 4-heteroaryl couma-
rins as tubulin assembly inhibitor. Bioorg Med Chem.
2008;16:8806-12.
Bowers AA, West N, Newkirk TL, Troutman-Youg-
man AE, Schreiber SL, Wiest O, et al. Synthesis and
histone deacetylase inhibitory activity of largazole an-
alogs: Alteration of the zinc-binding domain and mac-
rocyclic scaffold. Org Lett. 2009b;11:1301-4.
Garazd Y, Garazd M, Lesyk R. Synthesis and evaluation
of anticancer activity of 6-pyrazolinylcoumarin deriv-
atives. Saudi Pharm J. 2017;25:214-23.
Chen K, Xu L, Wiest O. Computational exploration of
zinc binding groups for HDAC inhibition. J Org Chem.
2013;78:5051-5.
Gerlier D, Thomasset T. Use of MTT colorimetric as-
say to measure cell activation. J Immunol Methods.
1986; 94:57-63.
Clarkson BD, Burchenal JH. Preliminary screening of
antineoplastic drugs. Prog Clin Cancer. 1965;1:625-9.
Goel R, Luxami V, Paul K. Synthesis, in vitro anti-
cancer activity and SAR studies of arylated imid-
azo[1,2-a]pyrazine-coumarin hybrids. RSC Adv.
2015;5:37887-95.
Coxon GD, Craig D, Corrales RM, Vialla E, Gannoun-
Zaki L, Kremer L. Synthesis, antitubercular activity
and mechanism of resistance of highly effective thiac-
etazone analogues. PLoS One. 2013;8:e53162,
https://doi.org/10.1371/journal.pone.0053162.
Gomha SM, Salaheldin TA, Hassaneen HME, Abdel-
Aziz HM, Khedr MA. Synthesis, characterization and
molecular docking of novel bioactive thiazolyl-thia-
zole derivatives as promising cytotoxic antitumor drug.
Molecules. 2015;21(1):E3, doi: 10.3390/mole-
cules21010003.
Datta AD, Daniels TC. Antitubercular activity of some
aromatic aldehyde and ketone derivatives. J Pharm Sci.
1963;52:905-6.
Gregoretti IV, Lee YM, Goodson HV. Molecular evo-
lution of the histone deacetylase family: functional im-
plications of phylogenetic analysis. J Mol Biol. 2004;
338:17-31.
Day JA, Cohen SM. Investigating the selectivity of
metalloenzyme inhibitors. J Med Chem. 2013;56:
7997-8007.
1128

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Hao YM. 2-Chloro-5-nitrobenzaldehyde thiosemi-
carbazone. Acta Cryst. 2010;66:o2528.
Kouzarides T. Chromatin modifications and their
functions. Cell. 2007;128:693-705.
Hernandez W, Paz J, Carrasco F, Vaisberg A, Spodine
E, Richter R, et al. Synthesis, characterization, and in
vitro cytotoxic activities of benzaldehyde thiosemi-
carbazone derivatives and their palladium(II) and plat-
inum(II) complexes against various human tumor cell
lines. Bioinorg Chem Appl. 2008;2008: Article ID
690952.
Li H, Wang X, Xu G, Zeng L, Cheng K, Gao P, et al.
Synthesis and biological evaluation of a novel class of
coumarin derivatives. Bioorg Med Chem Lett. 2014;
24:5274-8.
Lipinski CA, Lombardo F, Dominy BW, Feeney PJ.
Experimental and computational approaches to esti-
mate solubility and permeability in drug discovery and
development settings. Adv Drug Deliv Rev. 2001;
46:3-26.
Hernandez W, Paz J, Carrasco F, Vaisberg A, Manzur
J, Spodine E, et al. Synthesis and characterization of
new palladium(II) complexes with ligands derived
from furan-2-carbaldehyde and benzaldehyde thio-
semicarbazone and their in vitro cytotoxic activities
against various human tumor cell lines. Z Naturforsch
B Chem Sci. 2010;65:1271-8.
Liu MM, Chen XY, Huang YQ, Feng P, Guo YL, Yang
G, et al. Hybrids of phenylsulfonylfuroxan and couma-
rin as potent antitumor agents. J Med Chem. 2014;57:
9343-56.
Luo G, Chen M, Lyu W, Zhao R, Xu Q, You Q, et al.
Design, synthesis, biological evaluation and molecular
docking studies of novel 3-aryl-4-anilino-2H-
chromen-2-one derivatives targeting ERα as anti-
breast cancer agents. Bioorg Med Chem Lett. 2017;27:
2668-73.
Holiyachi M, Shastri SL, Chougala BM, Shastri LA,
Joshi SD, Dixit SR, et al. Design, synthesis and struc-
ture-activity relationship study of coumarin benzimid-
azole hybrid as potent antibacterial and anticancer
agent. Chemistry Select. 2016;1:4638-44.
Hubschwerlen C, Specklin JL, Sigwalt C, Schroeder S,
Locher HH. Design, synthesis and biological evalua-
tion of oxazolidinone-quinoline hybrids. Bioorg Med
Chem. 2003;11:2313-9.
Lv PC, Zhou CF, Chen J, Liu PG, Wang KR, Mao WJ,
et al. Design, synthesis and biological evaluation of thi-
azolidinone derivatives as potential EGFR and HER-2
kinase inhibitors. Bioorg Med Chem. 2010;18:314-9.
Ilies M, Dowling DP, Lombardi PM, Christianson DW.
Synthesis of a new trifluoromethylketone analogue of
l-arginine and contrasting inhibitory activity against
human arginase I and histone deacetylase 8. Bioorg
Med Chem Lett. 2011;21:5854-8.
Madsen AS, Kristensen HM, Lanz G, Olsen CA. The
effects of various zinc binding groups on inhibition of
histone deacetylases 1-11. Chem Med Chem.
2014;9:614-26.
Mendoza-Merono R, Menedez-Taboada L, Fernandez-
Zapico E, Garcia-Granda S. 1-(Biphenyl-4-ylmethyli-
dene)thiosemicarbazide monohydrate. Acta Cryst.
2010;66:o1029.
Jarrahpour A, Fathi J, Mimouni M, Ben Hadda T,
Sheikh J, Chohan ZH, et al. Petra, Osiris and molinspi-
ration (POM) together as a successful support in drug
design: antibacterial activity and biopharmaceutical
characterization of some azo Schiff bases. Med Chem
Res. 2011;19:1-7.
Methot JL, Chakravarty PK, Chenard M, Close J, Cruz
JC, Dahlberg WK, et al. Exploration of the internal
cavity of histone deacetylase (HDAC) with selective
HDAC1/HDAC2 inhibitors (SHI-1:2). Bioorg Med
Chem Lett. 2008;18:973-8.
Kaishi NK. Synthetic retarders for photographic emul-
sions. IV. Photographic properties of thiosemicarba-
zone derivatives. Ind Chem Sect. 1953;56:373-5.
Morsy SA, Farahat AA, Nasr MNA, Tantawy AS. Syn-
thesis, molecular modeling and anticancer activity of
new coumarin containing compounds. Saudi Pharm J.
2017, http://dx.doi.org/10.1016/j.jsps.2017.02.003.
Kamal A, Adil SF, Tamboli JR, Siddardha B, Murthy
USN. Synthesis of coumarin linked naphthalimide con-
jugates as potential anticancer and antimicrobial
agents. Lett Drug Des Discov. 2009;6:201-9.
Mosmann T. Rapid colorimetric assay for cellular
growth and survival: Application to proliferation and
cytotoxicity assays. J Immunol Methods. 1983;65:55-
63.
Kawai K, Nagata N. Metal-ligand interactions: An
analysis of zinc binding groups using the Protein Data
Bank. Eur J Med Chem. 2012;51:271-6.
Klenkar J, Molnar M. Natural and synthetic coumarins
as potential anticancer agents. J Chem Pharm Res.
2015;7:1223-38.
1129

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Nofal ZM, Soliman EA, Abd El-Karim S, El-Zahar M
Rouf A, Tanyeli C. Bioactive thiazole and benzothia-
zole derivatives. Eur J Med Chem. 2015;97:911-27.
I, Srour AM, Sethumadhavan S, et al. Synthesis of
some new benzimidazole-thiazole derivatives as anti-
cancer agents. J Heterocycl Chem. 2014;51:1797-806.
Salisbury CM, Cravatt BF. Activity-based probes for
proteomic profiling of histone deacetylase complexes.
Proc Natl Acad Sci USA. 2007;104:1171-6.
Oberling C, Guerin M. The role of viruses in the pro-
duction of cancer. Adv Cancer Res. 1954;2:353-423.
Sandhu S, Bansal Y, Silakari O, Bansal G. Coumarin
hybrids as novel therapeutic agents. Bioorg Med
Chem. 2014;22:3806-14.
Pahontu E, Fala V, Gulea A, Poirier D, Tapcov V, Rosu
T. Synthesis and characterization of some new Cu(II),
Ni(II) and Zn(II) complexes with salicylidene thio-
semicarbazones: Antibacterial, antifungal and in vitro
antileukemia activity. Molecules. 2013;18:8812-36.
Sashidhara KV, Kumar A, Kumar M, Sarkar J, Sinha
S. Synthesis and in vitro evaluation of novel coumarin-
chalcone hybrids as potential anticancer agents. Bioorg
Med Chem Lett. 2010;20:7205-11.
Pangal AA, Shaikh JA, Khan EM. Current develop-
ments of C3-substituted coumarin hybrids as anti-can-
cer agents. Int J Pharm Sci Rev Res. 2017;42:161-8.
Seidel C, Schnekenburger M, Zwergel C, Gaascht F,
Mai A, Dicato M, et al. Novel inhibitors of human his-
tone deacetylases: Design, synthesis and bioactivity of
3-alkenoylcoumarines. Bioorg Med Chem Lett. 2014;
24:3797-801.
Pasha FA, Muddassar M, Beg Y, Cho SJ. DFT-based
de novo QSAR of phenoloxidase inhibitors. Chem Biol
Drug Des. 2008;71:483-93.
Piens N, De Vreese R, De Neve N, Hecke KV, Balza-
rini J, De Kimpe N, et al. Synthesis of novel thymine-
β-lactam hybrids and evaluation of their antitumor ac-
tivity. Synthesis. 2014;46:2436-44.
Sheeja KR, Kuttan G, Kuttan R. Cytotoxic and anti-
tumour activity of Berberin. Amala Res Bull. 1997;
17:73-6.
Shitre GV, Bhosale RS, Karhale DS, Sujitha P, Kumar
CG, Krishna KV, et al. Synthesis and biological evalu-
ation of novel α-aminophosphonate derivatives pos-
sessing thiazole-piperidine skeleton as cytotoxic
agents. Chem Biol Interface. 2014;4:48-57.
Pingaew R, Prachayasittikul S, Ruchirawat S, Pracha-
yasittikul V. Synthesis and cytotoxicity of novel 4-(4-
(substituted)-1H-1,2,3-triazol-1-yl-N-phenethylben-
zenesulfonamides. Med Chem Res. 2014a;23:1768-80.
Pingaew R, Saekee A, Mandi P, Nantasenamat C, Pra-
chayasittikul S, Ruchirawat S, et al. Synthesis, biolog-
ical evaluation and molecular docking of novel chal-
cone-coumarin hybrids as anticancer and antimalarial
agents. Eur J Med Chem. 2014b;85:65-76.
Siddiqui N, Arshad M, Khan S. Synthesis of some new
coumarin incorporated thiazolyl semicarbazones as an-
ticonvulsants. Acta Pol Pharm Drug Res. 2009;66:161-
7.
Sreekanth T, Kavitha N, Shyamsunder A, Rajeshwar
Y, Sabhassomalingappa K. Synthesis, characterization,
in vitro cytotoxic and antioxidant activities of novel
coumarin thiazolyl derivatives. Int J Pharm Educ Res.
2014;1:29-35.
Prashanth T, Thirusangu P, Avin BRV, Ranganatha
VL, Prabhakar BT, Khanum SA. Synthesis and evalu-
ation of novel benzophenone-thiazole derivatives as
potent VEGF-A inhibitors. Eur J Med Chem. 2014;
87:274-83.
Srimanth K, Rao VR, Krishna DR. Synthesis and eval-
uation of anticancer activity of some imidazothiazolyl,
imidazobenzothiazolyl and dihydroimidazothiazolyl
coumarins. Arzneimittelforschung. 2002;52: 88-92.
Riveiro ME, De Kimpe N, Moglioni A, Vazquez R,
Monzor F, Shayo C, et al. Coumarins: Old compounds
with novel promising therapeutic perspectives. Curr
Med Chem. 2010;17:1325-38.
Stahl M, Rarey M. Detailed analysis of scoring func-
tions for virtual screening. J Med Chem. 2001;44:
1035-42.
Rodolpho CD, Andrade CH. Assessing the perform-
ance of 3D pharmacophore models in virtual screening:
How good are they?. Curr Top Med Chem. 2013;13:
1127-38.
Sumangala V, Poojary B, Chidananda N, Arulmoli T,
Shenoy S. Synthesis and biological evaluation of 2,4-
disubstituted-[1,3]-thiazoles. Chem Pharm Res. 2012;
4:4979-87.
Romagnoli R, Baraldi PG, Salvador MK, Camacho
ME, Balzarini J, Bermejo J, et al. Anticancer activity
of novel hybrid molecules containing 5-benzylidene
thiazolidine-2,4-dione. Eur J Med Chem. 2013;63:
544-57.
Tay F, Erkan C, Sariozlu N Y, Ergene E, Demirayak S.
Synthesis, antimicrobial and anticancer activities of
some naphthylthiazolylamine derivatives. Biomed
Res. 2017;28:2696-703.
1130

EXCLI Journal 2017;16:1114-1131 – ISSN 1611-2156
Received: February 10, 2017, accepted: July 31, 2017, published: August 30, 2017
Tsurkan AA, Gromova ZF, Rudzit EA, Neshchadim
Wolber G, Langer T. LigandScout: 3D pharmaco-
phores derived protein-bound ligands and their use as
virtual screening filters. J Chem Inf Comp Sci. 2005;
45:160-9.
GN, Kulikova DA. Synthesis of biologically active cy-
clopenteno[d]selenazole derivatives and their thio ana-
logs. Khim-Farm Zh. 1982;16:692-5.
Tung TT, Oanh DT, Dung PT, Hue VT, Park SH, Han
BW, et al. New benzothiazole/thiazole-containing hy-
droxamic acids as potent histone deacetylase inhibitors
and antitumor agents. Med Chem. 2013;9:1051-7.
Yi W, Dubois C, Yahiaoui S, Haudecoeur R, Belle C,
Song H, et al. Refinement of arylthiosemicarbazone
pharmacophore in inhibition of mushroom tyrosinase.
Eur J Med Chem. 2011;46:4330-5.
Ursu O, Rayan A, Goldblum A, Oprea T. Understand-
ing drug-likeness. WIREs Comput Mol Sci. 2011;1:
760-81.
Yuan JW, Wang SF, Luo ZL, Qiu HY, Wang PF,
Zhang X, et al. Synthesis and biological evaluation of
compounds which contain pyrazole, thiazole and naph-
thalene ring as antitumor agents. Bioorg Med Chem
Lett. 2014;24:2324-8.
Vaarla K, Kesharwani RK, Santosh K, Vedula RR, Ko-
tamraju S, Toopurani MK. Synthesis, biological activ-
ity evaluation and molecular docking studies of novel
coumarin substituted thiazolyl-3-aryl-pyrazole-4-carb-
aldehydes. Bioorg Med Chem Lett. 2015;25:5797-803.
Zain J, Kaminetzky D, O’Connor OA. Emerging role
of epigenetic therapies in cutaneous T-cell lymphomas.
Expert Rev Hematol. 2010;3:187-203.
Valizadeh H, Gholipur H, Shockravi A. Microwave as-
sisted synthesis of coumarins via potassium carbonate
catalyzed Knoevenagel condensation in 1-n-butyl-3-
methylimidazolium bromide ionic liquid. J Heterocycl
Chem. 2007;44:867-70.
Zhang L, Yao YC, Gao MY, Rong RX, Wang KR, Li
XL, et al. Anticancer activity and DNA binding prop-
erty of the trimers of triphenylethylene-coumarin hy-
brids. Chin Chem Lett. 2017;27:1708-16.
Zhang W, Li Z, Zhou M, Wu F, Hou X, Luo H, et al.
Synthesis and biological evaluation of 4-(1,2,3-triazol-
1-yl)coumarin derivatives as potential antitumor
agents. Bioorg Med Chem Lett. 2014;24:799-807.
Veber DF, Johnson SR, Cheng HY, Smith BR, Ward
KW, Kopple KD. Molecular properties that influence
the oral bioavailability of drug candidates. J Med
Chem. 2002;45:2615-23.
Weerasinghe SV, Estiu G, Wiest O, Pflum MK. Resi-
dues in the 11 Å channel of histone deacetylase 1 pro-
mote catalytic activity: Implications for designing iso-
form-selective histone deacetylase inhibitor. J Med
Chem. 2008;51:5542-51.
1131