Synthesis of novel bioactive derivatives of 3-(4-chlorophenyl)-2-hydrazino-5,6,7,8-tetrahydrobenzo(b)thieno[2,3-d]py rimidine-4(3H)-ones

Article abstract of DOI:10.1016/j.ejmech.2009.05.027

A series of triazolo[4,3-a]tetrahydrobenzo(b)thieno[3,2-e]pyrimidine-5(4H)-ones (12a-n) were synthesized and evaluated for CNS depressant, skeletal muscle relaxant and anticonvulsant activities by photoactometer, Rotarod and pentylenetetrazole induced the

Full text of DOI:10.1016/j.ejmech.2009.05.027

European Journal of Medicinal Chemistry 44 (2009) 4721–4725
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis of novel bioactive derivatives of 3-(4-chlorophenyl)-2-hydrazino-
5,6,7,8-tetrahydrobenzo(b)thieno[2,3-d]pyrimidine-4(3H)-ones
a
b
c
a
c
´
Sunil V. Gupta , Kamalkishor Baheti , Rajesh Bora , Deepak Dekhane , Mahesh Chhabrıa ,
Murlidhar Shingare a, Shivaji Pawar a, C.J. Shishoo c, S.N. Thore a
,
*
a Vinayakrao Patil Mahavidyalaya, Vaijapur Dist., Aurangabad 423 701, India
b Y.B. Chavan College of Pharmacy, Rafiq Zakeria Complex, Aurangabad 431 001, India
c L.M. College of Pharmacy, Navrangpura, Ahmedabad 380 009, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of triazolo[4,3-a]tetrahydrobenzo(b)thieno[3,2-e]pyrimidine-5(4H)-ones (12a–n) were synthe-
sized and evaluated for CNS depressant, skeletal muscle relaxant and anticonvulsant activities by
photoactometer, Rotarod and pentylenetetrazole induced the convulsions method respectively in Swiss
albino mice. Diazepam was used as standard drug. The five derivatives 12b, 12c, 12d, 12i and 12m showed
the CNS depressant and skeletal muscle relaxant activities comparable to those of diazepam at a dose of
5 mg/kg. These derivatives also exhibited good activity when tested for anticonvulsant activity in mice at
different dose levels. The ED50 values for these derivatives are in the range of 4.40–9.33 mg/kg.
Ó 2009 Elsevier Masson SAS. All rights reserved.
Received 3 December 2008
Received in revised form
6 May 2009
Accepted 20 May 2009
Available online 28 May 2009
Keywords:
Thieno[3,2-e]pyrimidine
Pentylenetetrazole
Clonic convulsions
Skeletal muscle relaxant activity
1. Introduction
compounds have been identified by their ability to modulate
GABA neurotransmission by interacting with receptor complex.
Central nervous system (CNS) depressant agents are an impor-
tant class of drugs, which are useful in the treatment of anxiety and
related emotional disorders. Among the different classes of CNS
depressant agents, benzodiazepines were found to have good
activity and well accepted by patients. They are acting through
Positive modulation, which leads to an increase in GABA-induced
chloride ion flux, is produced by agonist class-1 i.e. benzodiaze-
pine type e.g. diazepam (1), and triazolum (2) [6,7] and class-2
i.e. non-benzodiazepine type cyclopyrones, e.g. zopiclone (3),
triazolopyridazine like compound (4) [8] suriclone (5) [9] and CL
218,872 (6), imidazopyridines e.g. zolpidem (7) [10] as shown in
Fig. 1. Some non-benzodiazepine ligands are apparently selective
for GABAA receptors, which have reduced sedation. All these non-
benzodiazepine ligands were found to contain common polyaza
system. The condensed triazole and 1,2,4-triazole are also found
to contain polyaza ring system and which is present in a potent
CNS depressant agent alprazolam.
The literature survey reveals that triazoles were reported for
analgesic, anti-inflammatory, anti-allergic and CNS depressant
activities. A large number of references [11–17] showed that
condensed 1,2,4-triazoles are having excellent CNS depressant
and anticonvulsant activities. Significant CNS depressant activity
was reported for triazoles especially triazoloquinazoline [18],
triazolopyrimidines [19], triazolothienopyrimidine [20], 1,3,4-
thiadiazolotetrahydrobenzothienopyrimidine [21] and 1,3,4-
thiadiazole-quinazoline [22] has given an impetus to synthesize
some non-benzodiazepine ligands (bioisosteric triazolotetrahy-
drobenzo(b)thienopyrimidines), which are devoid of typical
benzodiazepine receptors, which are adjacent to g-amino butyric
acid (GABA) receptors. GABA is the major inhibitory neurotrans-
mitter in the brain. It controls excitability of many central nervous
system pathways. The intimate relationship between the benzo-
diazepine sites and GABA binding sites has been studied [1]. GABA
exerts its physiological effects by binding to the different receptor
types in the neuronal membrane: GABAA, GABAB and GABAC
receptors. The GABAB receptor belongs to the G-protein-coupled
receptors super family, while the GABAA [2] and GABAC [3] are
ligand gated chloride ion channel complexes. GABAA receptors,
which are responsible for the majority of neuronal inhibition in the
mammalian CNS, mediate the action of many pharmacological
useful agents, including benzodiazepines, barbiturates, neuroactive
steroids, anesthetics and convulsants [4,5]. At least two classes of
* Corresponding author.
E-mail address: snthore@rediffmail.com (S.N. Thore).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.05.027

4722
S.V. Gupta et al. / European Journal of Medicinal Chemistry 44 (2009) 4721–4725
F
N
N
Cl
N
N
O
O
N
N
N
N
N
N
N
Cl
N
Cl
O
N
O
N
N
Cl
O
N
N
(1)
(4)
(3)
(2)
N
N
N
H
N
N
N
N
N
H
Cl
N
N
O
N
O
S
CF3
S
N
O
(6)
(7)
(5)
Fig. 1.
benzodiazepine mediated side effect such as physical depen-
dence, amnesia, over sedation.
anticonvulsant activity at different dose levels. The results of the
various activities are presented in Tables 1–4.
A
series of 14 novel derivatives of triazolo[4,3-a]tetrahy-
drobenzo(b)thieno[3,2-e]pyrimidine-5(4H)-ones were synthesized
and evaluated for CNS depressant, skeletal muscle relaxant and
anticonvulsant activities.
4. Result and discussion
Fourteen derivatives were synthesized and their structure was
confirmed by IR, NMR, mass spectroscopy and elemental analysis.
All the fourteen derivatives tested for CNS depressant activity by
photoactometer (Table 1) shown a decrease in locomotor activity
between 46.15% and 90.40%.
The five derivatives (12b, 12c, 12d, 12i and 12m) showed
comparable CNS depressant activity at a dose of 5 mg/kg i.p. after
60 min of administration to that of standard drug diazepam
(89.32%) at a dose of 5 mg/kg. All the compounds except 12h
exhibited more than 50% decrease in locomotor activity after
60 min.
The title derivatives were also tested for skeletal muscle
relaxant activity (motor coordination) by Rotarod method (Table 2).
In this model, the five derivatives (12b, 12c, 12d, 12i and 12m)
showed the superior activity in the range from 102.75% to 116.62%
when compared with diazepam (100%) at a dose of 5 mg/kg. The
other derivative showed the activity in the range of 49.02–92.60%
2. Chemistry
Compound
3-(4-chlorophenyl)-2-hydroxy-5,6,7,8-tetrahydro
(9) was
benzo(b)thiophene[2,3-d]pyrimidine-4(3H)-one
synthesized from 2-amino-3-carbethoxy-4,5,6,7-tetrahydro-
benzo(b)thiophene (8) [23] on treatment with solution of p-
chlorophenyl isocyanate at 120 ꢀC and followed by cyclization
with potassium hydroxide solution. The compound (9) on
treatment with mixture of phosphorus oxychloride and
phosphoruspentachloride yielded the 2-chloro-3-(4-chlor-
ophenyl)-5,6,7,8-tetrahydrobenzo(b)thiophene[2,3-d]pyrimi-
dine-4(3H)-one (10) at refluxing condition. The chloro
derivative (10) on treatment with hydrazine hydrate in
methanol yielded 3-(4-chlorophenyl)-2-hydrazino-5,6,7,8-tet-
rahydrobenzo(b)thiophene[2,3-d]pyrimidine-4(3H)-one (11)
as shown in Scheme 1. The title compounds (12a–n) were
prepared by treating hydrazino derivative (11) with various
one carbon donors such as triethyl orthoformate, triethyl
orthoacetate, propionic acid, butyric acid, isobutyric acid,
chloroacetyl chloride, benzoyl chloride, cyanogen bromide,
ammonium thiocyanate and benzoyl chloride, methyl iso-
thiocyanate, ethyl isocyanate, phenyl isothiocyanate, carbon
disulphide. The title compounds (12a–n) were synthesized by
the route depicted in Scheme 2.
Cl
i) p-Cl-C6H4-NCO
O
O
reflux, 3h.
O
N
ii) KOH,H2O
reflux, 3h.
OH
N
S
NH2
S
8
9
POCl3/PCl5
120°C, 18 h
3. Biological activity
Cl
Cl
O
The title derivatives (12a–n) were evaluated for CNS depressant
activity by photoactometer and skeletal muscle relaxant activity
(motor coordination) by Rotarod method at a dose of 5 mg/kg in
Swiss albino mice. The activity was compared with diazepam as
a standard drug. Of the various compounds tested for CNS
depressant and skeletal muscle relaxant activities, the most active
five derivatives 12b, 12c, 12d, 12i and 12m were evaluated for
O
NH2NH2,H2O
N
N
Methanol,
reflux,15 min.
NH
NH2
N
S
Cl
N
S
11
10
Scheme 1. Synthesis of hydrazino intermediate (11).

S.V. Gupta et al. / European Journal of Medicinal Chemistry 44 (2009) 4721–4725
4723
Cl
O
N
Cl
Cl
N
N
S
O
O
N
R
N
N
12 c-e ; R =C2H5,n-C3H7,i-C3H7,
N
N
N
N
S
S
N
N
ClCH2COCl
AcOH
Orthoesters
reflux, 5h
RCO OH
R
R
12a ; R = H,
12f ; R = CH2Cl
Reflux, 10h
Reflux, 10h
12b R = CH3
Cl
Cl
O
Cl
O
N
CS2/ Pyridine
Reflux, 20 h
O
N
PhCOCl
140°C
N
N
N
S
N
N
S
NH
NH2
N
Reflux, 3h
N
S
N
R
11
R
12g ; R = Ph
12m R = SH
12n R = SCH3
Cl
DMS, KOH
rt, 12 h.
PhCOCl
NH4SCN/Acetone
Reflux, 10h
CNBr/C2H5OH
Reflux, 5h
RNCS/C2H5OH
Reflux, 6h
Cl
O
Cl
O
N
O
N
N
N
N
S
N
N
S
N
N
N
N
S
N
R
R
12j-l ; R= NHCH3,NHC2H5,NHC6H5
R
12h ; R = NHCOPh
12i ; R = NH2
Scheme 2. Synthesis of target compounds 12(a–n).
to that of standard drug. The most active five derivatives (12b, 12c,
12d, 12i and 12m) among the series were evaluated for anticon-
vulsant activity (Table 3). The dose required for protecting the
animal from pentylenetetrazole (PTZ) induced clonic convulsions
was determined for each compound. All the five compounds
offered good protection to the animals from the PTZ induced clonic
convulsions at the dose levels of 6.0–11.0 mg/kg body weight, while
diazepam showed 100% protection at the dose of 2.5 mg/kg. Again
the compound 12d exhibited the anticonvulsant activity by
protecting 100% animal at dose of 6.0 mg/kg body weight. The ED50
values for anticonvulsant activity of five compounds have also been
calculated and given in Table 4. The ED50 values for these deriva-
tives are in the range of 4.40–9.33 mg/kg while that of diazepam
showed an ED50 of 1.18.
The pharmacological results indicate that the series of
compounds exhibited comparable CNS depressant and skeletal
muscle relaxant activities than anticonvulsant activities.
5. Pharmacology
5.1. CNS depressant activity
5.1.1. CNS depressant activity by photoactometer method
The title compounds (12a–n) were screened for their CNS
depressant activity using photoactometer [24,25,26] at 30 min and
1 h after drug administration. The CNS depressant activity of animal
inside the photometer chamber was recorded as a photoactometer
counts. Decrease score suggests the CNS depressant activity. The
Table 1
CNS depressant activity by photoactometer (n ¼ 6; dose 5 mg/kg i.p.).
Compound
Photoactometer counts
% CNS depressant activity
Prior (control) administration
of test compound
30 min after administration
of test compound
60 min after administration
of test compound
After 30 min
After 60 min
12b
12c
12d
12i
12m
Diazepam
98 ꢁ 1.73
112 ꢁ 1.75
198 ꢁ 1.93
107 ꢁ 1.76
170 ꢁ 1.87
103 ꢁ 1.67
24 ꢁ 1.23
32 ꢁ 1.40
42 ꢁ 1.42
19 ꢁ 1.22
31 ꢁ 1.47
15 ꢁ 1.21
17 ꢁ 1.25
18 ꢁ 1.26
19 ꢁ 1.28
12 ꢁ 1.13
17 ꢁ 1.25
11 ꢁ 1.17
75.51
71.42
78.78
82.24
81.71
85.43
82.65
83.92
90.40
88.78
90.00
89.32
Each value represents the mean ꢁ SEM (n ¼ 6) significance levels P < 0.5.

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S.V. Gupta et al. / European Journal of Medicinal Chemistry 44 (2009) 4721–4725
Table 2
Table 4
Skeletal muscle relaxant activity (motor coordination) by Rotarod method (n ¼ 6;
Effective dose (ED50) protecting 50% population from pentylenetetrazole (85 mg/kg,
s.c.) induced clonic convulsions (n ¼ 6) in mice.
dose 5 mg/kg, i.p.).
Compound
Mean number of
falls/min (control)
Mean increase in
number of falls/min
% CNS depressant
activity
Compound
ED50 (mg/kg)
12b
12c
12d
12i
12m
Diazepam
9.33
8.50
4.40
6.73
5.50
1.18
12b
12c
12d
12i
12m
Diazepam
2.99 ꢁ 0.26
2.49 ꢁ 0.36
2.66 ꢁ 0.35
2.24 ꢁ 0.36
2.83 ꢁ 0.18
3.16 ꢁ 0.24
7.74 ꢁ 0.54
6.58 ꢁ 0.73
7.49 ꢁ 0.30
5.99 ꢁ 0.63
7.66 ꢁ 0.35
8.08 ꢁ 0.13
102.75
105.49
116.62
107.52
109.62
100.00
Each value represents the mean ꢁ SEM (n ¼ 6) significance levels P < 0.5.
5.1.2. Skeletal muscle relaxant activity (motor coordination) by
Rotarod method [27]
Swiss albino mice of either sex weighing 25–40 g weight were
used. They were divided into groups of six animals each and each
group was allowed to get acquainted for 10 min. Thereafter the
photoactometer counts were noted for a period of 10 min which
was the initial reading (control). The test compounds were sus-
pended in 1% CMC solution in distilled water and administered at
a dose of 5 mg/kg i.p. of the body weight. Each group is served as its
control. One of the groups was treated with diazepam as the
Motor coordination and balance were tested using Rotarod
apparatus. The mice weighing 25–40 g were divided into group of
six animals each. The test compounds were suspended in 1% CMC
solution in distilled water and administered at a dose of 5 mg/kg of
the body weight. Each group served as its control. One of the groups
was treated with diazepam as the standard at a dose of 5 mg/kg.
After 30 min of administration of test compound, the animals were
Mean increase in number of falls ꢂ Mean control reading
% Muscle relaxation activity ¼
ꢃ 100
Mean control reading
standard at a dose of 5 mg/kg. After 20 min of administration of test
compound, the animals were kept into the photoactometer
chamber and the counts were noted for 10 min after a 10 min rest
in the chamber. The same procedure was repeated after 50 min.
Decrease in the number of counts for each group was calculated
and finally, the %CNS depressant activity was determined by the
following formula.
placed on the Rotarod and again the number of falls per min was
recorded. Mean increase in number of falls per minute for each
group was calculated and finally skeletal muscle relaxation activity
was determined by the following formula.
The observations of activity are shown in Table 2.
5.1.3. Anticonvulsant activity (PTZ induced seizure test) [28]
Of the various compounds tested for CNS depressant activity,
the most active five derivatives 12b, 12c, 12d, 12i and 12m were
evaluated for anticonvulsant activity. The dose required for pro-
tecting the animal from pentylenetetrazole (PTZ) induced clonic
convulsions was determined for tested compound (Table 3).
Aqueous solution of PTZ (dose 85 mg/kg) was administered
subcutaneously to group of six mice, 30 min after the adminis-
tration of the test compound as suspension in 1% CMC i.p. The
mice were then observed for a period of 20 min for the symptoms
of clonic convulsions. The number of animals in each group, which
were protected against PTZ induced clonic convulsions was used
as a percentage response parameter for calculating the effective
anticonvulsant dose (ED50) of the test compound.
All the tested compounds offered good protection to the animals
from the PTZ induced clonic convulsions at the dose levels 6.0–
12.0 mg/kg body weight. Compound 12d exhibited the best anti-
convulsant activity by protecting 100% animals at dose of 6.0 mg/kg
body weight. ED50s of these compounds have also been calculated
and tabulated in Table 4.
Control readingꢂDecrease in count
%CNS depressant activity ¼
Control reading
ꢃ100
The observations of activity are shown in Table 1.
Table 3
Anticonvulsant activity (n ¼ 6, s.c.).
Compound
Dose (mg/kg)
% of animal protected against
PTZ induced clonic convulsions
12b
9.0
10.0
11.0
33.33
83.33
100.00
12c
8.0
9.0
33.33
66.66
10.0
100.00
12d
4.0
5.0
6.0
16.66
83.33
100.00
Acknowledgement
12i
6.0
7.0
8.0
16.66
66.66
100.00
Authors are grateful to the Principal, L.M. College of Pharmacy,
Ahmedabad for providing the support and laboratory facilities for
carrying out the research work.
12m
Diazepam
5.0
6.0
7.0
33.33
66.66
100.00
Appendix. Supplementary data
0.5
1.0
2.0
2.5
16.66
50.00
83.33
Experimental procedures and characterizations of intermedi-
ates and final compounds. This data is available online via internet
100.00

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4725
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