Synthesis and glycosidase inhibitory activity of novel (2-phenyl-4H- benzopyrimedo[2,1-b]-thiazol-4-yliden)acetonitrile derivatives

Article abstract of DOI:10.1016/j.bmcl.2012.10.025

A series of (2-phenyl-4H-benzopyrimodo[2,1-b][1,3]thiazol-4-yliden-4- yliden)acetonitrile derivatives have been prepared by ring transformation reaction of 4-(methylthio)-2-oxo-6-aryl-2H-pyrane-3-carbonitriles. The yield of ring transformation product is

Full text of DOI:10.1016/j.bmcl.2012.10.025

Bioorganic & Medicinal Chemistry Letters 22 (2012) 7011–7014
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and glycosidase inhibitory activity of novel
(2-phenyl-4H-benzopyrimedo[2,1-b]-thiazol-4-yliden)acetonitrile derivatives
Vijay S. Patil a,c, Kamalakar P. Nandre b, Sougata Ghosh d, Vaidya Jayathirtha Rao c, Balu A. Chopade d,
,
⇑
a,b,
Sheshanath V. Bhosale e, , Sidhanath V. Bhosale
⇑
⇑
a Department of Organic Chemistry, North Maharashtra University, Jalgaon 425 001, India
b Polymers and Functional Materials Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 607, India
c Division of Crop Protection Chemicals, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 607, India
d Institute of Bioinformatics and Biotechnology, University of Pune, Pune 411 007, India
e School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne, Vic. 3001, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 July 2012
Revised 6 September 2012
Accepted 4 October 2012
Available online 13 October 2012
A series of (2-phenyl-4H-benzopyrimodo[2,1-b][1,3]thiazol-4-yliden-4-yliden)acetonitrile derivatives
have been prepared by ring transformation reaction of 4-(methylthio)-2-oxo-6-aryl-2H-pyrane-3-carbo-
nitriles. The yield of ring transformation product is moderate to good. Furthermore the glycosidase inhib-
itory activities were tested by using
a-amylase and a-glucosidase pancreatic, intestinal and liver
enzymes, responsible for hyperglycemia in type II diabetes. The results revealed that all compounds exhi-
bit significant glycosidase inhibitory activity.
Keywords:
2-Aminobenzothiazoles
Glycosidase inhibitors
Ó 2012 Elsevier Ltd. All rights reserved.
Porcine pancreatic
a-amylase
Murine intestinal glycosidase
Diabetes mellitus is one of the most common chronic diseases
and belongs to the group of metabolic disorder.1 It is a major and
growing public health problem throughout the world, with an esti-
mated worldwide prevalence in 2010 of 285 million people and ex-
pected to rise to 439 million people by 2030.2 Globally diabetes is
likely to be fifth leading cause of death.3 The modern medicines
available for the treatment of type II diabetes (T2DM) cause serious
side effects such as hepatotoxicity, abdominal pain, flatulence,
diarrhea, and hypoglycaemia.4,5 Thus, a substantial research for
the discovery and synthesis of new antidiabetic agents with im-
The pyrimidine derivatives are found in nucleic bases as well as
building blocks for various natural products.8 These derivatives
exhibits interesting pharmacological activities including antiviral,9
antimicrobial,10 cardiotonic,11 diuretic,12 antihypertensive,13
antimalarial,14 leishmanicide,15 anti-inflammatory,16 antifilarial,17
anticancer18 and anti-HIV.19 Furthermore the importance of pyrim-
idine scaffold in pharmaceutical development is evident in a large
number of pyrimidine derivatives that have been approved by food
and drug administration (FDA) as drugs.20 This class of compounds
also has coordination ability similar to pyridyl ligands in supramo-
lecular metallo-grid like architecture.21,22
Vishnu Ji Ram and coworkers reported the synthesis of
bridgehead azolopyrimidines via thermal ring transformation
reactions of 6-aryl-3-cyano-4-methylsulfanyl-2H-pyran-2-ones.24
This method encouraged us to synthesize novel (2-phenyl-4H-
benzopyrimido[2,l-b]acetonitrile derivatives in presence of DBU
(Scheme 1). Furthermore the glycosidase inhibitory activity of
these compounds has also been studied.
proved compliance and reduced side effect are today’s need.
amylase and -glucosidase has been recognized as targets for the
drug discovery towards the maintenance of adequate glycaemic
control. -amylase is a glycoside hydrolase enzyme that breaks
down the long chain carbohydrates by cleaving the -1,4-glyco-
sidic bonds, resulting maltotriose and maltose from amylose while
maltose and glucose from amylopectin.6 Similarly,
-glucosidase
a-
a
a
a
a
hydrolyses disaccharides to monosaccharide that can be absorbed
into the blood stream.7 Thus both the enzymes consequently ele-
vate the blood glucose levels, which can be effectively controlled
with an effective glycosidase inhibitor.
In the present work synthesis of 2-(2-phenyl-4H-benzo[d]-
pyrimido[2,1-b][1,3]thiazol-4-yliden)acetonitrile (4, a–n)28 was
achieved via ring transformation reaction of 4-(methylthio)-2-
oxo-6-aryl-2H-pyran-3-carbonitriles (2, a–f) by using substituted
2-aminobenzothiazole (3, a–c). The catalytic condition employed
for ring transformation reaction was DBU in DMF (Scheme 1).
The precursors, 4-(methylthio)-2-oxo-6-aryl-2H-pyran-3-carbo-
⇑
Corresponding authors. Tel.: +91 40 27191545; tel.: +91 020 25690442 (B.A.C.).
E-mail addresses: directoribb@unipune.ac.in (B.A. Chopade), bsheshanath@
gmail.com (S.V. Bhosale), sidhanath2003@yahoo.co.in (S.V. Bhosale).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.10.025

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V. S. Patil et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7011–7014
NC
O
SCH3
NC
CN
a
OC2H5
SMe
N
b
Ar
N
S
R
Ar
O
O
MeS
1
4a-m
2a-f
Scheme 1. Reagent and conditions: (a) Acetophenone (a–f), KOH, DMF, rt. (b) 2-Aminobenzothiazoles, DBU, DMF, rt.
nitriles ( 2, a–f) were prepared by following known literature
exhibited inhibitory activity in micromolar range (IC50 = 0.99
In case of brominated derivatives 4m exhibited strongest inhibi-
tion as compared to 4d (IC50 = 28.16 M) while 4n showed no inhi-
bition. Even among the napthyl derivatives although 4g
lM).
method.23,23b
Acetonitrile derivatives tested for
significant levels of inhibition as compared to acarbose
(IC50 = 35.5 M). The study revealed that the chlorinated deriva-
tives 4b (IC50 = 21.85 M) and 4h (IC50 = 20.22 M) were moder-
ately potent and comparatively identical with that of fluorinated
derivatives 4c and 4e (IC50 = 24.39 and 20.60 M respectively).
However, brominated derivatives 4d (IC50 = 15.26 M), 4m
(IC50 = 17.43 M) and 4n (IC50 = 17.14 M) showed excellent inhi-
bition and were found to be superior as compared to other aceto-
nitrile derivatives. Naphthyl derivatives 4f (IC50 = 19.91 M) and
4g (IC50 = 18.71 M) were found to be superior as compared to
a
-amylase inhibition showed
l
l
(IC50 = 15.94
(IC50 = 21.19
l
M) was found to be an excellent inhibitor, 4f
l
l
lM) showed moderate activity. Both the methyl
derivatives and unsubstituted compounds showed an activity in
an intermediate range.
l
l
a
-Amylase inhibition assay: Synthesized acetonitrile derivatives
were checked for -amylase inhibitory activity according to slight
modification of Bernfeld method (1955) using starch as substrate.
In this assay, 50
g mlꢀ1 (OD 0.4 at 280 nm) of porcine pancreatic
-amylase was incubated with 1 mg mlꢀ1 samples at 37 °C for
10 min.25 One percent starch was used as substrate.
-Amylase
l
l
a
l
l
l
a
fluorine derivatives whereas less potent to brominated derivatives.
a
In case of the methyl derivatives a variation was observed among
without any compound was used as control. The estimation of
reducing sugar was carried out by using DNSA assay at A540 nm
and the enzyme units were expressed as micro-molar per minute.
One unit of enzyme was defined as the amount of enzyme required
4i and 4j. Compound 4i (IC50 = 23.24
ity similar to that of the fluorinated derivatives while 4j
(IC50 = 19.54 M) exhibited superior activity comparable to that
of napthyl derivatives 4f and 4g. Whereas derivatives 4k
(IC50 = 22.30 M), 4 l (IC50 = 21.80 M) and 4a (IC50 = 22.96 M)
lM) showed moderate activ-
l
to liberate 1 lM of maltose under employed assay conditions. The
l
l
l
final inhibition shown by different tested compounds were com-
pared with the standard inhibitor, acarbose.26 The inhibitory activ-
ity was calculated by using the formula:
showed an intermediate activity between chlorinated derivatives
and fluorinated derivatives.
Both chlorine and fluorine derivatives 4b (IC50 = 17.39
4c (IC50 = 17.48 M) were found to be significant inhibitors of mur-
ine pancreatic glucosidase while chlorine derivative 4h (IC50
20.71 M) exhibited comparatively lower inhibition. However,
the activities were higher as compared to acarbose (IC50
2.34 M). Both the fluorinated derivatives 4c (IC50 = 17.48 M)
and 4e (IC50 = 18.96 M) showed excellent inhibition among all
the acetonitrile derivatives tested. A variation was observed among
the brominated derivatives tested. Compound 4d (IC50 = 22.99 M)
and 4n (IC50 = 26.64 M) showed moderate inhibition while 4m
(IC50 = 33.75 M) exhibited a further reduced level of activity. Sim-
ilarly a significant difference was observed for the activity of nap-
thyl derivatives where 4f (IC50 = 19.91 M) showed moderate
inhibition while 4g (IC50 = 30.32 M) showed reduced inhibition.
lM) and
%Inhibition ¼ ðA540Control ꢀ A540TestÞ=A540Control ꢁ 100
l
Glucosidase inhibition assay with murine pancreatic, small intesti-
nal and liver extracts: Ten week old male Swiss mice weighing 20 g
were obtained from National Toxicology Centre, Pune and entire
procedure of activity testing was carried out with guidelines of
Institutional Animal Ethical Committee. The obtained mouse was
starved for 12 h. The pancreas, liver and small intestine tissues
were excised and homogenized with 10 mM ice cold phosphate
buffer containing 6 mM NaCl (1:10 dilution; w/v) and appropriate
amount of protease inhibitors. Tissue homogenates were centri-
fuged for 10 min at 10,000 rpm and the supernatant was taken as
a source of enzyme that was diluted so as to get an absorbance
of 0.4 (at 280 nm). Percentage inhibition of the samples against
pancreatic, small intestinal and liver glucosidases was calculated
using literature method.27
=
l
=
l
l
l
l
l
l
l
l
However methyl substituted as well as unsubstituted derivatives
showed inferior levels of inhibition except for the unsubstituted
Spectral data of newly synthesized compounds: [2-(2-Phenyl)-4H-
benzo[d]pyrimido[2,1-b][1,3]thiazol-4-yliden]acetonitrile: Table 1,
derivative 4a (IC50 = 21.42 lM).
A similar trend was observed for the activity of chlorinated
derivatives against murine intestinal glucosidase as was observed
in case of the pancreatic glucosidase while acarbose failed to show
any inhibition. Superior activity was exhibited selectively by chlo-
entry (4a). Yield-58%; mp 192–194 °C; IR (KBr t
max/cmꢀ1): 2848
(C–H), 2189 (–CN), 1609 (C@N); Mass [ESI, 70 eV] m/z (%): 303
(22), 302 (100); 1H NMR (CDCl3 d ppm): 5.08 (s, 1H, CH@C), 7.24
(s, 1H, phH), 7.39–7.48 (m, 5H, PhH), 7.64–7.66 (d, J = 7.5 1H,
PhH), 7.98–8.00 (m, 3H, PhH); 13C NMR(75 MHz, CDCl3, d ppm)
64.1, 102.1, 104.2, 115.7, 119.5, 121.4, 122.9, 125.9, 126.5, 126.6,
127.3, 128.7, 130.3, 131.6, 135.1, 150.4, 151.9, 160.4; HRMS (ESI)
m/z: Calcd for C18H12N3S1: [M+H]+ 302.0758. Found: 302.0751.
[2-(4-Chlorophenyl)-4H-benzo[d]pyrimido[2,1b][1,3]thiazol-4-
yliden]acetonitrile: Table 1, entry (4b). Yield-74%; mp 230–232 °C;
rinated derivatives. Compound 4b (IC50 = 17.62
imum activity. However both the fluorinated derivatives 4c
(IC50 = 37.29 M) and 4e (IC50 = 30.40 M) were found to be infe-
lM) showed max-
l
l
rior inhibitor for the intestinal glucosidase unlike pancreatic gluco-
sidase. Brominated derivatives 4d and 4n showed no inhibition.
A variation was observed among the derivatives in the inhibi-
tion of murine liver glucosidase with substitution of different
groups and even between the derivatives with identical substitu-
IR (KBr t
max/cmꢀ1): 2189 (–CN), 1608 (C@N); Mass [ESI, 70 eV] m/z
(%): 380 (67), 336 (100); 1H NMR (DMSO-d6 d ppm): 5.29 (s, 1H,
CH@C), 7.13–7.27 (m, 3H, PhH), 7.41–7.51 (m, 2H, PhH), 7.82–
7.85 (d J = 7.2 Hz, 1H, PhH), 8.00–8.05 (m, 2H, PhH), 8.14–8.16 (d,
J = 8.1 Hz, 1H, PhH); 13C NMR(75 MHz, DMSO-d6 d ppm) 65.0,
tions. Chlorinated derivative 4h (IC50 = 19.70
as compared to 4b (IC50 = 22.01 M). Similarly 4e (IC50 = 21.12
showed comparatively stronger inhibition than 4c (IC50
25.03 M) although both were fluorine derivatives. Acarbose
l
M) was more potent
l
l
M)
=
l

V. S. Patil et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7011–7014
7013
Table 1
Enzyme inhibition activitya of compound 4a–m
Entry
Ar
R
Enzyme inhibition IC50 values (lM)
Porcine pancreatic
a
-amylase
Murine pancreatic glucosidase
Murine intestinal glucosidase
Murine liver glucosidase
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
Acarbose
C6H5
H
H
H
H
OCH3
H
OCH3
OCH3
H
OCH3
OCH3
OC2H5
OCH3
22.96
21.85
24.39
15.26
20.60
19.91
18.71
20.22
23.24
19.54
22.30
21.80
17.43
35.50
21.42
17.39
17.48
22.99
18.96
22.91
30.32
20.71
34.87
29.47
29.19
46.15
33.75
>100
32.60
17.62
37.29
NI
23.54
22.01
25.03
28.16
21.12
21.19
15.94
19.70
20.30
18.29
24.95
18.70
14.13
>100
4Cl–C6H4
4F–C6H4
4Br–C6H4
4F–C6H4
2-Naphthyl
2-Naphthyl
4Cl–C6H4
4CH3–C6H4
4CH3–C6H4
C6H5
30.40
22.59
62.46
25.91
36.12
27.42
41.61
38.58
30.47
NI
C6H5
4Br–C6H4
a
The results summarized are the mean values of n = 3 for IC50 values, NI = No inhibition.
103.3, 107.4, 116.4, 119.5, 123.4, 124.2, 126.4, 126.8, 128.0, 128.8,
133.5, 134.9, 135.1, 147.7, 150.6, 155.6, 161.3; HRMS (ESI) m/z:
Calcd for C18H11Cl1N3S1: [M+H]+ 336.0347. Found: 336.0362.
[2-(4-Fluorophenyl)-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-
4-yliden]acetonitrile: Table 1, entry (4c). Yield-80%; mp 216–
[8-Methoxy-2-(2-naphthyl)-4H-benzo[d]pyrimido[2,1-
b][1,3]thiazol-4-yliden]acetonitrile: Table 1, entry (4g). Yield-62%;
mp 228–230 °C; IR (KBr t
max/cmꢀ1): 2924(C–H), 2180(–CN), 1601
(C@N); Mass [ESI, 70 eV] m/z (%): 383 (30), 382 (100).; 1H NMR
(DMSO-d6 d ppm): 3.88 (s, 3H, OCH3), 5.28 (s, 1H, CH@C), 7.29 (s,
1H, PhH), 7.53–7.56 (m, 4H, PhH), 7.95–7.98 (t, J = 5 Hz, J = 9 Hz,
218 °C; IR (KBr t
max/cmꢀ1): 2185 (–CN), 1602 (C@N); Mass [ESI,
70 eV] m/z (%): 320 (8), 321 (100); 1H NMR (DMSO-d6 d ppm):
5.09 (s, 1H, CH@C), 7.10–7.18 (m, 2H, PhH), 7.21 (s, 1H, PhH),
7.41–7.48 (m, 2H, PhH), 7.65–7.68 (dd, J = 1.5 Hz, J = 7.5 Hz 1H,
2H, PhH), 8.01–8.03 (m, 4H, PhH).; 13C NMR(75 MHz, DMSO-d6
d
ppm) 55.7, 63.1, 99.5, 103.3, 107.9, 113.3, 117.5, 119.8, 123.1,
126.1, 126.2, 126.6, 127.4, 128.4, 128.8, 128.9, 132.0, 132.7,
143.5, 146.6, 150.7, 158.6, 165.7.; HRMS (ESI) m/z: Calcd for
PhH), 7.98–8.03 (m, 3H, PhH); 13C NMR(75 MHz, DMSO-d6
d
ppm) 64.6, 103.0, 115.7, 115.9, 119.8, 120.4, 121.3, 123.4, 125.5,
126.5, 126.6, 126.9, 133.4, 143.6, 148.1, 150.9, 164.4, 165.0; HRMS
C
23H16N3O1S1: [M+H]+ 382.1021. Found: 382.1014.
[2-(4-Chlorophenyl)-8-methoxy-4H-benzo[d]pyrimido[2,1-
(ESI) m/z: Calcd for
C
18H11F1N3S1: [M+H]+ 320.0657. Found:
b][1,3]thiazol-4-yliden]acetonitrile: Table 1, entry (4h). Yield-73%;
320.0657.
mp 260–262 °C; IR (KBr
t
max/cmꢀ1): 2927(C–H), 2186(–CN), 1606
[2-(4-Bromophenyl)-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-
4-yliden]acetonitrile: Table 1, entry (4d). Yield-72%; mp 234–
(C@N); Mass [ESI, 70 eV] m/z (%): 368 (22), 366 (100).; 1H NMR
(DMSO-d6 d ppm): 3.88 (s, 3H, OCH3), 5.17 (s, 1H, CH@C), 7.16 (s,
1H, PhH), 7.38–7.44 (m, 3H, PhH), 7.82–7.84 (m, 2H, PhH), 7.95–
7.97 (d, J = 8.5 Hz, 2H, PhH).; 13C NMR(75 MHz, DMSO-d6 d ppm)
55.6, 63.4, 95.4, 103.2, 107.7, 113.3, 117.3, 120.4, 123.9, 126.0,
126.1, 127.8, 128.6, 134.7, 134.9, 143.0, 145.3, 164.5, 166.0.;HRMS
(ESI) m/z: Calcd for C19H13Cl1N3O1S1: [M+H]+ 366.0454. Found:
366.0467.
236 °C; IR (KBr t
max/cmꢀ1): 2922 (C–H), 2191 (–CN), 1606 (C@N);
Mass [ESI, 70 eV] m/z (%): 382 (80), 380 (100); 1H NMR (DMSO-
d6 d ppm): 5.51 (s, 1H, CH@C), 7.16 (s, 1H, PhH), 7.52–7.55 (t,
J = 3.6 Hz, J = 7.5 Hz, 2H, PhH), 7.62–7.69 (d, J = 8.6 Hz, 2H, PhH),
7.94–7.97 (m, 3H, PhH), 8.03–8.06 (m, 1H, PhH); 13C NMR(75 MHz,
DMSO-d6 d ppm) 65.0, 103.4, 116.4, 121.2, 122.2, 122.9, 123.4,
123.8, 124.3, 126.3, 128.1, 128.3, 131.7, 131.8, 133.9, 146.3,
153.1, 161.1.; HRMS (ESI) m/z: Calcd for C18H11Br1N3S1: [M+H]+
379.9842. Found: 379.9857
[2-(4-Methylphenyl)-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-
4-yliden]acetonitrile: Table 1, entry (4i). Yield-51%; mp 208–
210 °C; IR (KBr t
max/cmꢀ1): 2914(C–H), 2186(-CN), 1607 (C@N);
[2-(4-Flurophenyl)-8-methoxy-4Hbenzo[d]pyrimido[2,1-
b][1,3]thiazol-4-yliden]acetonitrile: Table 1, entry (4e). Yield-84%;
Mass [ESI, 70 eV] m/z (%): 338 (12), 316 (100).; 1H NMR (DMSO-
d6 d ppm): 2.35 (s, 3H, CH3), 5.42 (s, 1H, CH@C), 7.09 (s, 1H,
PhH), 7.30–7.32 (d, J = 8.2 Hz, 2H, PhH), 7.49–7.54 (m, 2H, PhH),
7.86–7.88 (d, J = 8.2 Hz, 2H, PhH), 8.00–8.02 (dd, J = 1.8 Hz,
J = 7.3 Hz,1H, PhH), 8.19–8.21 (d, J = 9.1 Hz, 1H, PhH).; 13C
NMR(75 MHz, DMSO-d6 d ppm) 20.9, 64.0, 102.4, 116.5, 119.9,
121.1, 123.4, 124.3, 126.1, 126.2, 126.5, 129.3, 129.5, 131.5,
131.9, 135.3, 140.3, 149.1, 165.3.; HRMS (ESI) m/z: Calcd for
mp 232–234 °C; IR (KBr t
max/cmꢀ1): 2921(C–H), 2190(–CN), 1610
(C@N); Mass [ESI, 70 eV] m/z (%): 351 (15), 350 (20); 1H NMR
(DMSO-d6 d ppm): 3.88 (s, 3H, OCH3), 5.16 (s, 1H, CH@C), 7.12–
7.20 (m, 4H, PhH), 7.41(s, 1H, PhH), 7.99–8.05 (m, 3H, PhH); 13C
NMR(75 MHz, DMSO-d6 d ppm) 55.7, 63.0, 102.7, 107.9, 113.3,
115.6, 115.8, 117.5, 119.8, 125.4, 126.5, 128.5, 128.6, 131.3,
142.4, 150.6, 161.7, 163.7, 164.7.; HRMS (ESI) m/z: Calcd for
C
19H14N3S1: [M+H]+ 316.0922. Found: 316.0908.
C
19H13F1N3O1S1: [M+H]+ 350.0768. Found: 350.0763.
[8-Methoxy-2-(4-methylphenyl)-4Hbenzo[d]pyrimido[2,1-
[2-(2-Naphthyl)-4H-benzo[d]pyrimido[2,1b][1,3]thiazol-
b][1,3]thiazol-4-yliden]acetonitrile: Table 1, entry (4j). Yield-52%;
4yliden]acetonitrile: Table 1, entry (4f). Yield-64%; mp 226–
mp 240–242 °C; IR (KBr
t
max/cmꢀ1): 2931(C–H), 2191(–CN), 1607
228 °C; IR (KBr
t
max/cmꢀ1): 2923(C–H), 2178(–CN), 1599 (C@N);
(C@N); Mass [ESI, 70 eV] m/z (%): 347 (25), 346 (100).; 1H NMR
(DMSO-d6 d ppm): 2.41 (s, 3H, CH3), 3.89 (s, 3H, OCH3), 5.08 (s,
1H, CH@C) 7.14 (s, 1H, PhH), 7.23–7.25 (d, 2H, J = 8.3 Hz, PhH),
7.78–7.81 (d, J = 7.5 Hz, 2H, PhH), 7.85–7.87 (d, J = 8.3 Hz, 2H,
PhH), 7.98–8.02 (d, J = 9.2 Hz, 1H, PhH).; 13C NMR(75 MHz,
DMSO-d6 d ppm) 20.9, 55.6, 62.4, 95.4, 102.3, 113.2, 117.3, 121.0,
122.3, 125.0, 126.0, 128.7, 129.2, 131.9, 136.6, 137.7, 150.8,
163.1, 163.4, 168.9.; HRMS (ESI) m/z: Calcd for C20H16N3O1S1:
[M+H]+ 346.1018. Found: 346.1014.
Mass [ESI, 70 eV] m/z (%): 353 (30), 352 (100).; 1H NMR (DMSO-
d6 d ppm): 5.15 (s, 1H, CH@C), 7.43 (s, 1H, PhH), 7.45–7.55 (m,
4H, PhH), 7.69–7.71 (dd, J = 1.3 Hz, J = 7.5 Hz, 1H, PhH), 7.86–8.06
(m, 5H, PhH), 8.58 (s, 1H, PhH).; 13C NMR(75 MHz, DMSO-d6
d
ppm) 64.2, 104.4, 115.7, 119.5, 122.9, 123.3, 125.1, 126.4, 126.5,
127.0, 127.2, 127.6, 128.2, 128.4, 128.9, 132.2, 133.1, 134.2,
135.5, 150.1, 151.9, 160.4.; HRMS (ESI) m/z: Calcd for
C
22H14N3S1: [M+H]+ 352.0920. Found: 352.0908.

7014
V. S. Patil et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7011–7014
4. Fujisawa, T.; Ikegami, H.; Inoue, K.; Kawabata, Y.; Ogihara, T. Metabolism 2005,
[8-Methoxy-2-phenyl-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-
54, 387.
4-yliden]acetonitrile: Table 1, entry (4k). Yield-72%; mp 226–
5. Singh, S. K.; Rai, P. K.; Jaiswal, D.; Watal, G. Evid. Based Complement. Altern. Med.
2008, 5, 415.
6. Akkarachiyasit, S.; Charoenlertkul, P.; Yibchok-anun, S.; Adisakwattana, S. Int. J.
Mol. Sci. 2010, 11, 3387.
7. Eduardo, B. D. M.; Adriane, D. S.; Gomes, I. C. Tetrahedron 2006, 62, 10277.
8. Blackburn, G. M. Nucleic Acids in Chemistry and Biology In Gait, M. J., Ed.;
Oxford University Press, 1996.
228 °C; IR (KBr t
max/cmꢀ1): 2922(C–H), 2288(–CN), 1602 (C@N);
Mass [ESI, 70 eV] m/z (%): 333 (20), 332 (100).; 1H NMR (DMSO-
d6 d ppm): 3.85 (s, 3H, OCH3), 5.36 (s, 1H, CH@C), 7.05–7.09 (dd,
J = 9.2 Hz, J = 2.8 Hz, 1H, PhH), 7.13 (s, 1H, PhH), 7.50–7.53 (m,3H,
PhH), 7.69–7.70 (d, J = 2.6 Hz, 1H, PhH), 7.97–8.00 (m, 2H, PhH),
8.14–8.17 (d, J = 9.4 Hz, 1H, PhH).;13C NMR(75 MHz, DMSO-d6
d
9. Ram, V. J.; Berghe, D. A. V.; Vlientick, A. J. Liebigs Ann. Chem. 1987, 9, 797.
10. Khobragade, C. N.; Bodade, R. G.; Konda, S. G.; Dawane, B. S.; Manwar, A. V. Eur.
J. Med. Chem. 2010, 45, 1635.
ppm) 55.8, 62.9, 103.0, 107.9, 111.2, 113.3, 117.5, 119.9, 126.1,
126.2, 128.9, 130.3, 135.0, 138.2, 144.4, 149.0, 157.3, 163.2,
167.9.; HRMS (ESI) m/z: Calcd for
11. Brueschaber, L.; Heyedenhauss, D.; Hodzel, H.; Jaeneeke, G.; Konetzke, G.;
Roethling, T.; Eckhard, T.; Tenor, E. Chem. Abstr. 1988, 108, 112493t. Ger (East)
DD 247003, 1987.
C
19H14N3O1S1: [M+H]+
332.0871. Found: 332.0857.
12. Wright, W.B.; Tomcufeik, A.S.; Marisco. J.W.J. USA US 4325955, 1982; Chem.
Abstr. 1982, 97, 23818q.
13. Walker, H. A.; Wilson, S.; Atkins, E. C.; Garrett, H. E.; Richardson, A. R. J.
Pharmacol. Exp. Ther. 1951, 101, 368.
[8-Ethoxy-2-phenyl-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-4-
yliden]acetonitrile: Table 1, entry (4l). Yield-70%; mp 180–182 °C;
IR (KBr t
max/cmꢀ1): 2927(C–H), 2187(–CN), 1605 (C@N); Mass [ESI,
14. Falco, E. A. Br. J. Pharmacol. 1961, 6, 185.
70 eV] m/z (%): 347 (28), 346 (100).; 1H NMR (DMSO-d6 d ppm):
1.40–1.45 (t, 3H), 4.07–4.17 (q, 2H OCH2), 5.21 (s, 1H, CH@C),
7.14 (s, 1H, PhH), 7.46–7.47 (m, 4H, PhH), 7.96–7.98 (m, 2H,
15. Ram, V. J.; Singha, U. K.; Guru, P. Y. Eur. J. Med. Chem. 1990, 25, 533.
16. Dannhardt, G.; Bauer, A.; Nowe, U. Arch. Pharm. 1997, 330, 74.
17. Pershin, G. N.; Sherbarkova, L. I.; Zykova, T. N.; Sokolova, V. N. Farmakol.
Toksikol. 1972, 35, 466.
18. Howells, R. E.; Tinsly, J.; DeVaney, E.; Smith, G. Acta Trop. 1981, 38, 289.
19. Hisamichi, H.; Naito, R.; Toyoshima, A.; Kawano, N.; Ichikawa, A.; Orita, A.;
Orita, M.; Hamada, N.; Takeuchi, M.; Ohta, M.; Tsukamoto, S. Bioorg. Med. Chem.
Lett. 2005, 13, 4936.
PhH), 8.04–8.07 (m, 2H, PhH).;13C NMR(75 MHz, DMSO-d6
d
ppm) 14.3, 62.8, 63.7, 95.4, 103.0, 108.1, 113.7, 117.3, 121.3,
125.9, 126.1, 128.2, 128.6, 128.8, 130.0, 134.8, 149.1, 150.7,
160.6, 163.4.; HRMS (ESI) m/z: Calcd for C20H16N3O1S1: [M+H]+
346.1019. Found: 346.1014.
20. William, B. P. Chem. Rev. 2009, 109, 2880.
21. Lehn, J.-M. Supramolecular Chemistry–Concepts and Perspectives; VCH:
Weinheim, 1995. Chapter 9.
22. Semenov, A.; Spatz, J. P.; Moller, M.; Lehn, J.; Sell, B.; Schubert, D.; Weidl, C. H.;
Schubert, U. S. Angew. Chem., Int. Ed. 1999, 38, 2547.
23. (a) Tominaga, Y. Trends Heterocycl. Chem. 1991, 2, 43; (b) Tominaga, Y.;
Ushirogochi, A.; Matsuda, Y.; Kobayashi, G. Chem. Pharm. Bull. 1984, 32, 3384.
24. Ram, V. J.; Srivastava, P.; Goel, A. Tetrahedron 2003, 59, 7141.
25. Bernfeld, P. Methods Enzymol. 1955, 1, 149.
[2-(4-Bromorophenyl)-8-methoxy-4H-benzo[d]pyrimido[2,1-
b][1,3]thiazol-4-yliden]acetonitrile: Table 1, entry (4m). Yield-
77%; mp 280–282 °C; IR (KBr t
max/cmꢀ1): 2930(C–H), 2186(–CN),
1604 (C@N); Mass [ESI, 70 eV] m/z (%): 412 (100), 418 (98).; 1H
NMR (DMSO-d6 d ppm): 3.86 (s, 3H, OCH3), 5.33 (s, 1H, CH@C),
7.14 (s, 1H, PhH), 7.60–7.64 (m, 3H, PhH), 7.67 (s, 1H, PhH),
7.89–7.94 (m, 3H, PhH).; 13C NMR(75 MHz, DMSO-d6 d ppm)
53.8, 62.3, 95.4, 113.4, 115.3, 117.4, 119.5, 119.7, 125.3, 126.7,
128.1, 128.7, 131.1, 131.6, 134.1, 139.0, 148.0, 162.4, 166.3.; HRMS
(ESI) m/z: Calcd for C19H13Br1N3O1S1: [M+H]+ 409.9972. Found:
409.9962.
26. Ghosh, S.; Ahire, M.; Patil, S., Jabgunde A.; Bhat Dusane M.; Joshi B. N.; Pardeshi
K.; Jachak S.; Dhavale. D.D.; Chopade B. A. Evid. Based Complement. Altern. Med.,
2011; 2012, ID:929051, http://dx.doi.org/10.1155/2012/929051.
27. Sanap, S. P.; Ghosh, S.; Jabgunde, A. M.; Pinjari, R. V.; Gejji, S. P.; Singh, S.;
Chopade, B. A.; Dhavale, D. D. Org. Biomol. Chem. 2010, 8, 3307.
28. Experimental section: Melting points of all the synthesized compounds were
determined by a Kofler micro melting point apparatus and were uncorrected.
IR spectra were recorded on a Thermo Nicolet Nexus 670 spectrometer using
KBr pellets. 1H NMR spectra were recorded on AVANCE 300 MHz spectrometer
using tetramethyl silane (TMS) as an internal standard. Mass spectra were
recorded on VG-7070H Micromass at 200 °C, 70 eV. The pharmacological
evaluations of the products were carried out in pharmacological unit, Institute
of Bioinformatics and Biotechnology (University of Pune, INDIA).
Synthesis of 6-aryl-3-cyano-4-methylthio-2H-pyran-2-ones (2, a–f): A reaction
mixture of equimolar quantities of an acetyl compound (1 mmol) and ethyl 2-
cyano-3,3-bis(methylthio)acrylate 1 (1 mmol) in the presence of powder KOH
(2 mmol) in 30 mL of dry DMF was stirred at room temperature for 5–6 h.
In summary, novel series of (2-phenyl-4H benzopyrimido [2,1-
b]thiazol-4-yliden)acetonitrile derivatives were synthesized. The
employed catalytic system offers high reaction yields, short reac-
tion time and mild conditions. Furthermore inhibition activity of
fused pyrimido derivative shows good to excellent glycosidase
inhibitory activity. Among the investigated compounds 4d and
4m showed excellent
a-amylase inhibition where as 4c and 4e
showed very high glucosidase inhibition. The present investigation
demonstrates the majority of the newly synthesized compounds
can be considered as lead molecule for further study.
Progress of the reaction was monitored by TLC (ethyl acetate:hexane 3:7, v/v).
After completion of the reaction, the reaction mixture was poured into crushed
ice (300 mL of ice-water) with vigorous stirring and the reaction mixture was
allowed to stand at room temperature about 4–5 h. The yellow precipitates
formed was filtered, washed with cold water and dried in air. The crude
product was recrystallized from benzene-methanol or methanol, dried at room
temperature gives 40–70% yield.
Acknowledgments
Synthesis
of
2-(2-phenyl-4H-benzo[d]pyrimido[2,1-b][1,3]thiazol-4-
The authors are thankful to the Director, IICT, Hyderabad for
providing necessary instrumental facilities. Sid. V. Bhosale would
like to thank the CSIR, New Delhi, India for financial support under
XIIth five year plan. S. Ghosh thanks Council of Scientific and
Industrial Research (CSIR, Government of India) for Senior Re-
search Fellowship (09/137(0516)/2012-EMR-I).
yliden)acetonitrile (4a–m): A mixture of 2-aminobenzothazole (3a, 1 mmol)
and DBU (2 mmol) in DMF (15 mL) was stirred under nitrogen for 10–15 min at
room temperature followed by addition of 4-(methylthio)-2-oxo-6-aryl-2H-
pyran-3-carbonitrile (2a, 1 mmol) under nitrogen flux with constant stirring.
The progress of the reaction was monitored by TLC (ethyl acetate:hexane, 2:8,
v/v). After completion of the reaction, the reaction mixture was poured onto
crushed ice with vigorous stirring about 30 min. The reaction mixture was
allowed to stand at room temperature for 20 min to settle down the solid,
filtered and the residue was recrystallized from MeOH/CHCl3 (warm) gives the
target compounds [2-(2-phenyl)-4H-benzo[d] pyrimido[2,1-b][1,3]thiazol-4-
yliden]acetonitrile 4a in 58% yield. The spectral data confirm the structure of
the synthesised compounds [Table 1]. This typical experimental procedure was
used to prepare the other analogues (4b–m) of this series.
References and notes
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3. Roglic, G.; Unwin, N.; Bennett, P. H.; Mathers, C.; Tuomilehto, J.; Nag, S.;
Connolly, V.; King, H. Diabetes Care 2005, 28, 2130.