Design, synthesis, and molecular docking study of benzothiazolotriazine derivatives for anticonvulsant potential

Article abstract of DOI:10.1002/ardp.201800154

A series of newer benzothiazolotriazine derivatives (4a–k) was designed, synthesized, and characterized as anticonvulsant agents against the two classically used MES and scPTZ animal models. The synthesized derivatives were tested in vivo in both the animal models, followed by a neurotoxicity study by the rotarod method. Compound 4e, 8-chloro-4-(2-chlorocyclohexa-1,5-dien-1-yl)-2-((4-methoxybenzyl)thio)-10aH-benzo[4,5]thiazolo[3,2a][1,3,5]triazine was found most promising among the series in both the animal models, with no neurotoxicity. From this it may be confirmed that the presence of a methoxy (OCH₃) group at the lipophilic aryl ring was showing high anticonvulsant potency. In the molecular modeling study, compound 4e (docking score = ?8.70) showed important hydrogen bond interaction with the amino acids LYS 329, SER 137, GLY 136 and π–π interactions with PHE 189 at the active site of GABA-AT. These derivatives can be further explored for the development of newer/novel anticonvulsant agents.

Full text of DOI:10.1002/ardp.201800154

Received: 20 May 2018
Revised: 18 October 2018
Accepted: 21 October 2018
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DOI: 10.1002/ardp.201800154
FULL PAPER
Design, synthesis, and molecular docking study of
benzothiazolotriazine derivatives for anticonvulsant potential
Jannat Ul Firdaus1
Mohd. Javed Naim1
Anwar Habib2
Sangh Partap1
Nadeem Siddiqui1
Meeta Sahu1
Ozair Alam1
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1 Department of Pharmaceutical Chemistry,
School of Pharmaceutical Education and
Research, Jamia Hamdard, New Delhi, India
Abstract
A series of newer benzothiazolotriazine derivatives (4a–k) was designed, synthesized,
and characterized as anticonvulsant agents against the two classically used MES and
scPTZ animal models. The synthesized derivatives were tested in vivo in both the
animal models, followed by a neurotoxicity study by the rotarod method. Compound
4e, 8-chloro-4-(2-chlorocyclohexa-1,5-dien-1-yl)-2-((4-methoxybenzyl)thio)-10aH-
benzo[4,5]thiazolo[3,2a][1,3,5]triazine was found most promising among the series
in both the animal models, with no neurotoxicity. From this it may be confirmed that the
presence of a methoxy (OCH3) group at the lipophilic aryl ring was showing high
anticonvulsant potency. In the molecular modeling study, compound 4e (docking
score = −8.70) showed important hydrogen bond interaction with the amino acids LYS
329, SER 137, GLY 136 and π–π interactions with PHE 189 at the active site of GABA-
AT. These derivatives can be further explored for the development of newer/novel
anticonvulsant agents.
2 Department of Medicine, HIMSR, Jamia
Hamdard, New Delhi, India
Correspondence
Prof. Nadeem Siddiqui, Department of
Pharmaceutical Chemistry, School of
Pharmaceutical Education and Research,
Jamia Hamdard, New Delhi-110062, India.
Email: nadeems_03@yahoo.co.in
K E Y W O R D S
benzothiazole, epilepsy, GABA-AT, molecular docking, triazine
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1
INTRODUCTION
leptic drugs (AEDs) are the most effective treatment for epilepsy;
despite the fact that almost all antiepileptic drugs currently used
Epilepsy is a common neurological disorder due to the predisposition
to produce epileptic stress and is characterized by the occurrence of
cognitive, neurological, social, and psychosocial changes.[1] Antiepi-
have only significant safety and efficacy profile.[2] AEDs block
seizures, but have little effect in preventing or curing this disease
completely.[3] Several new anticonvulsant agents like vigabatrin,
lamotrigine, gabapentine, felbamate, rufinamide, and levetiracetam
have been introduced in the clinical practices.[4] The search for
newer/novel AEDs is important for the population suffering from
epilepsy.
Abbreviations: AEDs, antiepileptic drugs; Alip., aliphatic; Anal. calcd., analytically calculated;
aq., aqueous; Ar, aromatic; CDCl3, deuterated chloroform; CPCSEA, Committee for the
Purpose of Control and Supervision of Experiments on Animals; ESI, electrospray
ionization; FT-IR, Fourier transform infrared; GABA-AT, gamma-aminobutyric acid; HBD,
hydrogen bonding domain; IAEC, Institutional Animal Ethics Committee; i.p., intraperito-
neal; KBr, potassium bromide; LCMS/MS, liquid chromatography mass spectrometry; m.p.,
melting point; MES, maximal electroshock seizures; NMR, nuclear magnetic resonance;
OPLS, optimized potentials for liquid simulations; PDB, protein data bank; PEG, polyethyl-
ene glycol; PPAR, peroxisome proliferators activated receptor; RCSB, Research Collabora-
tor for Structural Bioinformatics; Rf, retention factor; scPTZ, subcutaneous
Based on molecular mechanism of action, the currently marketed
AEDs can be classified as voltage-dependent Na+ and/or Ca2+
channels modulators; GABA-mediated inhibition enhancers or any
other action on the GABA system; synaptic excitation inhibition
facilitated through ionotropic glutamate receptors and modulators of
synaptic release.[5] Among all ionotropic glutamate receptors,
pentylenetetrazole; TLC, thin layer chromatography.
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Arch Pharm Chem Life Sci. 2018;1–9.
wileyonlinelibrary.com/journal/ardp
© 2018 Deutsche Pharmazeutische Gesellschaft
1

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FIRDAUS ET AL.
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GABA-AT is a recently approved validated target for AEDs; its
selective prohibition raises the concentration of GABA in the cerebrum
that improves the neurological symptoms.[6] Inhibition of GABA-AT
modifies the balance between GABA and L-glutamate which makes it
an important target for neuroactive drugs. Specific inactivation by
vinyl-GABA is useful for the treatment of epilepsy.[7]
vicinity of ethanolic sodium hydroxide and benzylchloride/4-methox-
ybenzylchloride. The sequence of reaction involving synthesis of the
mentioned derivatives is given in Scheme 1. The structures were
characterized by FT-IR, 1H NMR, 13C NMR, and mass spectral analysis
followed by elemental analysis. IR spectra showed C-H Ar stretching

and C C Ar stretching bands in the region 3066–3020 and 2860–
2821 cm−1, respectively. The C N stretching bands for triazine

Benzothiazoles are bicyclic ring system with wide range of
biological activities including anticonvulsant activity.[8,9] The endocy-
clic sulfur and nitrogen function in this heterocyclic nucleus has been
found to be critical for anticonvulsant activity. In recent years,
extensive research has been carried out for modifying benzothiazole
nucleus in order to improve its anticonvulsant potential.[10,11]
Moreover, triazine ring is also an important building block in medicinal
chemistry with a number of biological activities.[12,13] This ring is also
expected to increase the basicity of benzothiazole system and hence
the stability of its salts in the solution for rapid metabolism.
appeared at 1643–1608 cm−1, where as the C─N stretching bonds
were observed in between 1288 and 1227 cm−1. Characteristic
absorption bands at 879–802 and 712–693 cm−1 were corresponding
to the C─Cl and C─S stretching functions of the structures. In 1H NMR
spectra, a singlet of CH protons of benzothiazolotriazine resonated
at δ 3.59–3.77 ppm. The benzylic protons (─S─CH2) appeared at
δ 4.39–4.69 ppm. Multiplet for aromatic protons (Ar─H) was observed
at δ 6.29–7.99 ppm.
As a part of our program on the chemistry of heterocyclic system
as potent anticonvulsant agents, we synthesized a series of newer
benzothiazolotriazine derivatives. The design of benzothiazolotriazine
derivatives was done based on the hypothesis[14,15] (Figure 1).
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2.2 Pharmacology
All the synthesized derivatives were evaluated for anticonvulsant
potential against MES and scPTZ model. These models are the
standard methods for predicting protection against tonic–clonic and
generalized absence seizures. The most potent compound 4e showed
potent activity in both seizures model without neurotoxicity in
comparison to the standard drugs (phenytoin, vigabatrin, and
carbamazepine). In MES model, compounds 4a and 4e showed
electroshock protection at 0.5 h specifying that they have a quick
onset of action. Compounds 4b, 4c, 4f, 4h, and 4j were found active at
100 mg/kg at 0.5 h. At 4.0 h, compounds 4a and 4b showed activity at
100 mg/kg and from this, it can be said they have a longer duration of
action at a moderate dose. In the scPTZ model, compounds 4c and 4e
were found active at 100 mg/kg at 0.5 h. Compound 4e continued
protection at 100 mg/kg at 4.0 h. One of the compounds 4b showed
neurotoxicity at 300 mg/kg at 4.0 h. Rest of the compounds showed no
neurotoxic effect in the animals. Moreover, compound 4e was found to
be most potent among the series and therefore, it is supposed to be
most potent selective GABA facilitator.
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2
RESULTS AND DISCUSSION
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2.1 Chemistry
An equimolar mixture of 4-substituted aniline and potassium
thiocyanate in 10% glacial acetic acid was stirred followed by addition
of bromine in 20 mL glacial acetic acid to afford the synthesis of 1a–e,
which were then treated with substituted benzoyl isothiocyanate to
obtain 2a–d. The cyclization reaction of 2a–d was performed in the
presence of n-butanol to yield 3a–k which exists in thiol-thione
tautomerism.[16] Respective compounds 3a–k were refluxed in the
From the structure–activity relationship study, it can be said that
compound 4e appeared as the most potent compound among the
series and it contains ─OCH3 (methoxy) group at lipophilic aryl ring.
Compound 4a is also found active in MES test as it is showing activity
at 30 mg/kg at 0.5 h but at 4.0 h it is found active at 100 mg/kg dose.
Compound 4a does not possess ─OCH3 (methoxy) group at lipophilic
aryl ring. From these observations, it can be said that ─OCH3
(methoxy) group at lipophilic aryl ring is responsible for prolonged
anticonvulsant activity as compound 4e continued to show activity at
4.0 h and this compound was also found active in the scPTZ test while
4a is not showing any activity even at 300 mg/kg. Moreover, 4e was
observed as the most potent compound in the series.
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2.3 Molecular docking
The molecular docking studies were performed to establish the binding
pattern of the newer synthesized compounds to the GABA-AT binding
FIGURE 1 Designed compounds bearing all the essential
pharmacophoric elements for anti-convulsant activity

FIRDAUS ET AL.
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SCHEME 1 Synthesis of compounds 4a–k. Reagents and conditions: (a) bromine, 3 h, 10°C; (b) ArCONCS, reflux, 5 h; (c) n-butanol, reflux,
5 h; (d) benzylchloride/4-methoxybenzylchloride, ethanolic sodium hydroxide, reflux, 5 h
site. All the compounds were found to show strong inhibition by
completely occupying the active sites in the target protein (GABA-AT).
All inhibitors showed higher docking scores than vigabatrin. Com-
pound 4e was found to be most potent, have higher docking score and
assumes favorable orientation within the GABA-AT binding site. The
binding mode of compound 4e is exactly same as the co-crystal ligands
which were represented in 2D ligands interaction diagram (Figure 2).
The docked pose (Figure 3a) of the compound 4e showed the
hydrogen bond interaction with amino acids LYS 329, SER 137, GLY
136, and π interaction with PHE 189. The additional interaction of
ligand 4e is the rationale for high affinity. The receptor surface model
of compound 4e is represented in Figure 3b. The docked pose of
second most dock ranked compounds 4c and 4h are displayed in
Figure 4. The 3D docked pose of compounds 4c and 4h showing
hydrogen bonding interactions with GLN 301, CYS 135, SER 137, GLY
136, and π interaction with PHE 189 at the binding site of GABA-AT.
The 2D-docked pose of vigabatrin is represented in Figure 5.
docking score (−8.70). Therefore, these derivatives can be further
explored for future anticonvulsant drug development.
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4
EXPERIMENTAL
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4.1 Chemistry
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4.1.1 General
The chemicals and solvents used in synthesis of compounds were
obtained from E. Merck (Darmstadt, Germany), S.D. Fine Chemicals
Ltd. (Mumbai, India) and Sigma–Aldrich. The reaction progress was
monitored by thin layer chromatography (TLC) technique performed
on Merk 60 F254 coated aluminum sheet by using toluene, ethyl
acetate, and formic acid in the ratio of 5:4:1 as solvent. Melting points
were determined by the open capillary method and are uncorrected.
FT-IR spectra were recorded on an IR Affinity-I Shimadzu FTIR
spectrometer using KBr pellets and Vmax values are given in cm−1
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3
CONCLUSION
1H NMR spectra were recorded on a Bruker model DRX-400 NMR
spectrometer (1H at 400 MHz, 13C at 100 MHz) in CDCl3. Chemical
shifts (δ) are expressed in Hz (Hertz). Mass spectra were recorded on
an LCMS/MS (Perkin-Elmer and LABINDA, Applied Biosystem) model
no. API 3000 presented as m/z. Elemental analysis (C, H, and N) were
recorded on Perkin-Elmer model 240C analyses for C, H, and N were
within 0.4% of the theoretical values. The physicochemical param-
eters are depicted in (Table 1).
In conclusion, a series of newer benzothiazolotriazine derivatives (4a–k)
was synthesized as anticonvulsant agents. Compound 4e, 8-chloro-4-
(2-chlorocyclohexa-1,5-dien-1-yl)-2-((4-methoxybenzyl)thio)-10aH-
benzo[4,5]thiazolo[3,2a][1,3,5]triazine was found most potent anticon-
vulsant agent with no neurotoxicity in both the animal models: MES,
scPTZ. In molecular modeling studies, compound 4e showed hydrogen
bond interaction with amino acids LYS 329, SER 137, GLY 136, and π
interaction with PHE 189 at GABA-AT receptor site with the highest
The InChI codes of the investigated compounds are provided as
Supporting Information.

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FIRDAUS ET AL.
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FIGURE 2 2D Ligplot diagram of compound 4e at the binding site of GABA-AT
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4.1.2 Synthesis of 6-substitutedbenzo[d]thiazol-2-
amines (1a–e)
on ice bath. Bromine (0.01 mol) dissolved in 20 mL of glacial acetic acid
was added dropwise maintaining the temperature below 10°C and
stirring was continued for 3 h. The contents of the flask were kept
overnight for the completion of the reaction. The separated orange
precipitates were filtered and washed with acetic acid, dissolved in hot
Equimolar mixture (0.01 mol) of 4-substituted aniline and potassium
thiocyanate in 10% glacial acetic acid was taken and stirred constantly
FIGURE 3 (a) 3D docked pose of compound 4e showing hydrogen bonding interaction with LYS 329, SER 137, GLY 136, and π interaction
with PHE 189 at the binding site of GABA-AT; (b) receptor surface view of compound 4e at the binding site of GABA-AT

FIRDAUS ET AL.
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FIGURE 4 3D docked pose of compound 4c (left panel) and 4h (right panel) showing H-bonding interaction with GLN 301, CYS 135, SER
137, GLY 136, and π interaction with PHE 189 at the binding site of GABA-AT
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water, and filtered. The filtrate was cooled and neutralized with 25%
aqueous ammonia solution to pH 6. The dark yellow product was
filtered, washed with water, and recrystallized from appropriate
solvent to obtain compounds 1a–e.[11]
4.1.4 Synthesis of 4-(substitutedphenyl)-8-
substituted-10aH-benzo[4,5]thiazolo[3,2-a][1,3,5]-
triazine-2-thiols (3a–k)
A solution of compounds 2a–d (0.01 mol) in n-butanol (30 mL) was
refluxed for 5 h. The precipitate formed after cooling was recrystallized
from n-butanol to obtain the compounds 3a–k.[11]
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4.1.3 Synthesis of substituted-N-((6-
substitutedbenzo[d]thiazol-2-yl)carbamothioyl)-
benzamides (2a–d)
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4.1.5 Synthesis of 4-(substitutedphenyl)-2-(4-
An appropriate substituted benzoyl isothiocyanate (0.02 mol) and
equimolar quantity of 1a–e were refluxed in benzene for 5 h. The solid
product was filtered out and then recrystallized from benzene to
obtain compounds 2a–d.
substitutedbenzylthio)-8-substituted-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4a–k)
Compounds 3a–k (0.01 mol) were dissolved in ethanolic sodium
hydroxide (0.02 mol, 2 N) and equimolar quantity of benzyl chloride/4-
methoxybenzylchloride was added to this solution followed by
refluxing for 5 h. The contents of the flask were cooled and poured
into ice-cold water. The precipitate obtained was filtered, washed with
water, and recrystallized from ethanol–water to obtain compounds
4a–k as shown in Scheme 1.
2-(Benzylthio)-8-chloro-4-phenyl-10aH-benzo[4,5]thiazolo[3,2-
a][1,3,5]triazine (4a)
FT-IR (KBr, vmax cm−1): 3062 (CHstr., Ar), 2856 (CHstr., Alipstr.), 1629
(CNstr.), 1286 (C-Nstr.), 812 (C-Clstr.), 707 (C-Sstr.); 1H NMR (CDCl3,
400 MHz) δ ppm: 3.75 (s, 1H, CH), 4.59 (s, 2H, CH2), 7.21–7.98 (m, 13H,
Ar-H and benzothiazolyl H); 13C NMR (CDCl3, 100 MHz): 35.2, 79.3,
115.9, 121.4, 125.0, 126.7, 127.8, 129.1, 133.8, 135.0, 154.2, 170.1;
ESI-m/z: 421.05 [M+], 422.05 [M+1]+. Anal. calcd. for C22H16ClN2S2: C,
62.63; H, 3.81: N, 9.95%. Found: C, 62.64; H, 3.85; N, 9.97%.
8-Fluoro-2-((4-methoxybenzyl)thio)-4-phenyl-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4b)
FT-IR (KBr, vmax cm−1): 3050 (CHstr., Arstr.), 2849 (CHstr., Alipstr.), 1620
(C N
str.), 1400 (C-Fstr.), 1281 (C-Nstr.), 710 (C-Sstr.); 1H NMR (CDCl3,

FIGURE 5 2D Ligplot diagram of vigabatrin at the binding site of
GABA-AT

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FIRDAUS ET AL.
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TABLE 1 Physicochemical parameters of the synthesized compounds 4a–k
Comp.
4a
R
R1
R2
Mol. formula
Mol. wt.
421.97
435.54
530.89
401.55
488.45
439.96
456.41
469.98
451.99
431.57
447.11
M.p. (°C)
140–142
280–282
200–202
125–128
210–212
130–132
204–206
290–292
158–160
110–112
105–107
% Yield
69
Rf (TEF-5:4:1)
0.76
clog P
6.80
6.15
7.58
6.53
7.29
6.94
7.51
6.86
6.72
6.45
5.90
Cl
H
H
C22H16ClN3S2
C23H18FN3OS2
C23H17BrClN3OS2
C23H19N3S2
4b
4c
F
H
OCH3
OCH3
H
80
0.85
Br
2-Cl
H
50
0.54
4d
4e
4f
CH3
Cl
73
0.74
2-Cl
2-Cl
4-Cl
4-Cl
4-OCH3
4-OCH3
4-OCH3
OCH3
H
C23H19Cl2N3OS2
83
0.88
F
C
22H15ClFN3S2
22H15ClFN3S2
57
0.93
4g
4h
4i
Cl
H
C
73
0.81
F
OCH3
H
C23H17ClFN3OS2
C23H18ClN3OS2
C24H21N3OS2
78
0.80
Cl
63
0.85
4j
CH3
OCH3
H
78
0.87
4k
H
C24H21N3O2S2
60
0.86
400 MHz) δ ppm: 3.71 (s, 1H, CH), 3.89 (s, 3H, OCH3), 4.52 (s, 2H, CH2),
7.30–7.68 (m, 12H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3,
100 MHz): 33.8, 56.8, 77.8, 110.7, 112.3, 114.3, 124.9, 126.8, 129.3,
132.3, 135.3, 151.0, 156.8, 159.0, 173.1; ESI-m/z: 435.09 [M+],
436.09 [M+H]+. Anal. calcd. for C23H18FN3OS2: C, 63.44; H, 4.18; N,
9.66%. Found: C, 63.48; H, 4.20; N, 9.68%.
8-Chloro-4-(2-chlorocyclohexa-1,5-dien-1-yl)-2-((3-
methoxybenzyl)thio)-10aH-benzo[4,5]thiazolo[3,2-a][1,3,5]-
triazine (4e)
FT-IR (KBr, vmax cm−1): 3032 (CHstr., Arstr.), 2840 (CHstr., Alipstr.), 1637
(C
str.), 1254 (C-Nstr.), 802 (C-Clstr.), 712 (C-Sstr.); 1H NMR (CDCl3,

N
400 MHz) δ ppm: 3.64 (s, 1H, CH), 3.69 (s, 3H, OCH3), 4.50 (s, 2H, CH2),
7.06–7.50 (m, 11H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3,
100 MHz): 21.9, 35.1, 36.8, 56.6, 79.1, 114.8, 115.7, 120.0, 121.1,
123.7, 129.7, 131.8, 135.7, 156.3, 170.8; ESI-m/z: 487.03 [M+],
488.04 [M+H]+. Anal. calcd. for C23H19Cl2N3OS2: C, 56.56; H, 3.92; N,
8.60%. Found: C, 56.60; H, 3.95; N, 8.62%.
8-Bromo-4-(2-chlorophenyl)-2-((4-methoxybenzyl)thio)-10aH-
benzo[4,5]thiazolo[3,2a][1,3,5]triazine (4c)
FT-IR (KBr, vmax cm−1): 3058 (CHstr., Arstr.), 2860 (CHstr., Alipstr.), 1637
(C
str.), 810 (C-Clstr.), 705 (C-Sstr.) 612 (C-Brstr.); 1H NMR (CDCl3,

N
400 MHz) δ ppm: 3.77 (s, 1H, CH), 3.81 (s, 3H, OCH3), 4.36 (s, 2H, CH2),
7.19–7.51 (m, 11H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3,
100 MHz): 35.1, 55.0, 77.8, 115.8, 112.1, 120.8, 123.1, 125.0, 126.3,
127.8, 128.0, 130.6, 131.0, 132.8, 134.3, 155.8, 157.6, 171.8; ESI-m/z:
528.97 [M+], 529.97 [M+H]+, 530.97 [M+2] +. Anal. calcd. for
2-(Benzylthio)-4-(2-chlorophenyl)-8-fluoro-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4f)
FT-IR (KBr, vmax cm−1): 3020 (CHstr., Arstr.), 2840 (CHstr., Alipstr.), 1640
(CNstr.), 1230 (C-Nstr.), 1420 (C-Fstr.), 802 (C-Clstr.), 709 (C-Sstr.);
1H NMR (CDCl3, 400 MHz) δ ppm: 3.59 (s, 1H, CH), 4.69 (s, 2H, CH2),
7.21–7.60 (m, 12H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3,
100 MHz): 35.1, 79.3, 112.1, 115.6, 123.7, 125.1, 126.0, 127.1, 129.7,
132.5, 133.3, 135.0, 149.5, 157.2, 168.9; ESI-m/z: 439.04 [M+],
440.04 [M+H]+. Anal. calcd. for C22H15ClFN3S2: C, 60.06; H, 3.44; N,
9.55%. Found: C, 60.10; H, 3.47; N, 9.57%.
C23H17BrClN3OS2: C, 52.03; H, 3.23; N, 7.92%. Found: C, 52.08; H,
3.25; N, 7.94%.
2-(Benzylthio)-8-methyl-4-phenyl-10aH-benzo[4,5]thiazolo[3,2-
a][1,3,5]triazine (4d)
FT-IR (KBr, vmax cm−1): 3055 (CHstr., Arstr.), 2854 (CHstr., Alipstr.), 1635
(C
str.), 1288 (C-Nstr.), 698 (C-Sstr.); 1H NMR (CDCl3, 400 MHz) δ

N
ppm: 2.54 (s, 3H, CH3), 3.68 (s, 1H, CH), 4.51 (s, 2H, CH2), 7.03–7.61
(m, 13H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3, 100 MHz):
20.1. 35.2, 78.0, 113.2, 124.1, 126.2, 127.0, 128.3, 129.6, 132.1,
135.7, 139.0, 139.0, 171.1; ESI-m/z: 401.10 [M+]. Anal. calcd. for
2-(Benzylthio)-8-chloro-4-(4-chlorophenyl)-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4g)
FT-IR (KBr, vmax cm−1): 3066 (CHstr., Arstr.), 1608 (C Nstr.), 1273

(C-Nstr.), 879 (C-Clstr.), 694 (C-Sstr.); 1H NMR (CDCl3, 400 MHz) δ ppm:
3.74 (s, 1H, CH), 4.57 (s, 2H, CH2), 7.31–7.60 (m, 12H, Ar-H and
benzothiazolyl H); 13C NMR (CDCl3, 100 MHz): 33.2, 77.1, 115.8,
C23H19N3S2: C, 68.80; H, 4.77; N, 10.46%. Found: C, 68.84; H, 4.80; N,
10.48%.

FIRDAUS ET AL.
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120.0, 123.1, 126.2, 127.6, 128.0, 131.1, 135.8, 136.7, 139.0, 153.2,
171.6; ESI-m/z: 455.01 [M+], 456.01 [M+H]+. Anal. calcd. for
2-(Benzylthio)-4-(4-methoxyphenyl)-8-methyl-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4j)
C22H15Cl2N3S2: C, 57.89; H, 3.31; N, 9.21%. Found: C, 57.93; H,
FT-IR (KBr, vmax cm−1): 3065 (CHstr., Arstr.), 2832 (CHstr., Alipstr.), 1640
3.34; N, 9.23%.
str.), 1275 (C-Nstr.), 712 (C-Sstr.); 1H NMR (CDCl3, 400 MHz) δ

(C N
ppm: 2.29 (s, 1H, CH3), 3.71 (s, 1H, CH), 3.80 (s, 3H, OCH3), 4.53 (s, 2H,
CH2), 7.09–7.45 (m, 12H, Ar-H and benzothiazolyl H); 13C NMR
(CDCl3, 100 MHz): 35.8, 74.8, 113.8, 115.7, 120.9, 123.9, 125.2,
127.0, 129.6, 130.7, 131.9, 135.0, 154.8, 165.0, 173.1; ESI-m/z:
431.11 [M+]. Anal. calcd. for C24H21N3OS2: C, 66.80; H, 4.92; N,
9.75%. Found: C, 66.83; H, 4.93; N, 9.76%.
4-(4-Chlorophenyl)-8-fluoro-2-((4-methoxybenzyl)thio)-10aH-
benzo[4,5]thiazolo[3,2a][1,3,5]triazine (4h)
FT-IR (KBr, vmax cm−1): 3043 (CHstr., Arstr.), 2833 (CHstr., Alipstr.), 1643

Nstr.), 1242 (C-Nstr.), 1415 (C-Fstr.), 805.11 (C-Clstr.), 712.33 (C-
(C
str.); 1H NMR (CDCl3, 400 MHz) δ ppm: 3.64 (s, 1H, CH), 3.86 (s, 3H,
S
OCH3), 4.68 (s, 2H, CH2), 7.31–7.59 (m, 11H, Ar-H and benzothiazolyl
H); 13C NMR (CDCl3, 100 MHz): 35.0, 55.7, 79.1, 110.8, 114.1, 115.0,
124.9, 125.8, 127.1, 128.1, 129.8, 130.8, 134.7, 153.5, 155.6, 159.1,
171.3; ESI-m/z: 469.05 [M+], 470.05 [M+H]+. Anal. calcd. for
2-(Benzylthio)-8-methoxy-4-(4-methoxyphenyl)-10aH-
benzo[4,5]thiazolo[3,2-a][1,3,5]triazine (4k)
FT-IR (KBr, vmax cm−1): 3055 (CHstr., Arstr.), 2821 (CHstr., Alipstr.), 1632
C23H17ClFN3OS2: C, 58.78; H, 3.65; N, 8.94%. Found: C, 58.82; H,
str.), 1227 (C-Nstr.), 693 (C-Sstr.); 1H NMR (CDCl3, 400 MHz) δ

(C N
3.68; N, 8.96%.
ppm: 3.69 (s, 1H, CH), 3.89 (s, 6H, OCH3), 4.57 (s, 2H, CH2), 6.29–7.37
(m, 12H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3, 100 MHz):
30.8, 79.1, 110.5, 113.1, 115.4, 118.0, 124.1, 127.7, 128.7, 130.0,
132.2, 135.7, 145.0, 155.2, 159.0, 174.3. ESI-m/z: 447.11 [M+]. Anal.
calcd. for C24H21N3O2S2: C, 64.40; H, 4.75; N, 9.37%. Found: C, 64.44;
H, 4.78; N, 9.43%.
2-(Benzylthio)-8-chloro-4-(4-methoxyphenyl)-10aH-benzo[4,5]-
thiazolo[3,2-a][1,3,5]triazine (4i)
FT-IR (KBr, vmax cm−1): 3053 (CHstr., Arstr.), 2845 (CHstr., Alipstr.), 1641
(C
str.), 1255 (C-Nstr.), 802 (C-Clstr.), 695 (C-Sstr.); 1H NMR (CDCl3,

N
400 MHz) δ ppm: 3.60 (s, 1H, CH), 3.77 (s, 3H, OCH3), 4.59 (s, 2H, CH2),
7.06–7.41 (m, 12H, Ar-H and benzothiazolyl H); 13C NMR (CDCl3,
100 MHz): 33.1, 76.7, 112.4, 114.1, 119.9, 123.6, 124.7, 126.2, 127.0,
129.7, 130.6, 135.1, 136.8, 153.2, 160.3, 170.7; ESI-m/z: 451.06 [M+],
452.06 [M+H]+. Anal. calcd. for C23H18ClN3OS2: C, 61.11; H, 4.02; N,
9.29%. Found: C, 61.17; H, 4.05; N, 9.35%.
|
4.2 Molecular docking
The molecular docking study of designed molecules was carried out in
order to determine the binding patterns with target receptor/enzyme
using Glide extra precision (XP) Maestro 10.1 Schrodinger, running on
TABLE 2 Anticonvulsant activity and docking scores of the synthesized compounds 4a–k
MES screen
scPTZ
0.5 h
Neurotoxicity
Compound
0.5 h
30a
100
100
300
30
4.0 h
100
100
300
300
30
4.0 h
–
0.5 h
–
4.0 h
–
Docking score
−7.76
−7.68
−8.53
−7.15
−8.70
−7.33
−7.01
−8.31
−7.16
−6.39
−6.46
−6.50
–
b
4a
–
4b
300
100
–
300
300
–
–
300
–
4c
–
4d
–
–
4e
100
–
100
–
–
–
4f
100
300
100
300
100
300
250
30
300
300
300
300
300
300
250
30
–
–
4g
–
–
–
–
4h
300
–
300
–
–
–
4i
–
–
4j
–
–
–
–
4k
–
–
–
–
Vigabatrinc
Phenytoinc
Carbamazepinec
–
–
–
–
–
–
100
100
100
300
30
30
100
300
–
an = 4 (no. of animals tested in each group), the figures in the table indicate the minimum dose whereby bioactivity was demonstrated in half or more of the
mice; all solution were prepared in polyethylene glycol 400 (PEG 400).
b(−) Means no activity at 300 mg/kg.
[14,19,23]
cData from Refs.
.

8
FIRDAUS ET AL.
|
Linux 64 operating system.[17] The 2D structures of synthesized
derivatives were produced and then changed to their respective 3D
structures using Ligplot. The PDB file of the γ-aminobutyric acid
aminotransferase (GABA-AT) (PDB ID: 4ZSY) was downloaded from
RCSB Protein Data Bank. The protein was prepared by means of the
protein preparation wizard and receptor grid was generated for co-
crystal ligands and vigabatrin. The water molecules/residues beyond
5 Å were excluded. The protein undergoes optimization by assigning
H-bonds and minimization at OPLS 2005 force field. The docked pose
of ligands and their interactions were analyzed after the end of
molecular docking (Table 2).
incompetence of the animal (mice) to sustain steadiness on the rotarod
for at least 1 min in each of three successive trails.[22]
ACKNOWLEDGMENTS
The authors are thankful to School of Pharmaceutical Education and
Research, Jamia Hamdard, New Delhi, India, for providing all necessary
facilities for this work. PTZ was obtained from Shrenik Pharma, Mumbai
as a gift sample. The co-author (Dr. Ozair Alam) is thankful to DST-SERB
(SB/FT/LS-203-2012), New Delhi, for providing molecular modeling
software (Schrödinger, USA) under Fast track young scientist scheme.
|
4.3 Biological activity
CONFLICT OF INTEREST
The procedure for maximal electroshock seizures (MES), subcuta-
neous pentylenetetrazole (scPTZ), and rotarod test were per-
formed according to the ADD Program, Epilepsy Branch, National
Institutes of Health, Bethesda, MD, USA.[18,19] Albino mice (18–
25 g) were procured from Central Animal House Facility, Jamia
Hamdard, New-Delhi-110062. The animals were housed under
standard conditions and permitted open access to food and water.
The test compounds were evaluated at three graded doses, 30,
100, 300 mg/kg intraperitoneally (i.p.). All the experimental
procedures in the study were performed by approval of Institu-
tional Animal Ethics Committee (IAEC, 173/GO/Re/S/2000/
CPCSEA) project proposal no. 1329.
The authors declare no conflict of interest.
ORCID
Nadeem Siddiqui
http://orcid.org/0000-0002-0501-9988
http://orcid.org/0000-0003-0322-2509
Ozair Alam
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|
4.3.1 MES test
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|
4.3.2 scPTZ test
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|
4.3.3 Neurotoxicity
Toxic effects of the synthesized compounds were detected by using
standardized rotarod test. Mice were trained to halt on a knurled
rotarod of diameter 3.2 cm and rotating at 10 revolutions per minute.
These trained mice were then administered with the test compounds
and assessed for motor impairment which was specified by the

FIRDAUS ET AL.
9
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[22] N. W. Dunham, T. S. Miya, J. Am. Pharm. Assoc. 1957, 10, 208.
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How to cite this article: Firdaus JU, Habib A, Siddiqui N,
et al. Design, synthesis, and molecular docking study of
benzothiazolotriazine derivatives for anticonvulsant
potential. Arch Pharm Chem Life Sci. 2018;1–9.
https://doi.org/10.1002/ardp.201800154
SUPPORTING INFORMATION
Additional supporting information may be found online in the
Supporting Information section at the end of the article.