Synthesis and anticonvulsant activity of novel quinazolin-4(3H)-one derived pyrazole analogs

Article abstract of DOI:10.1007/s00044-012-0169-9

Eighteen novel 6,8-(dibromo/unsubstituted)-2-(methyl/phenyl)-3-(4-(5- (substitutedphenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-carbonyl)phenyl) -quinazolin-4(3H)-ones 4a-4r were designed and synthesized in good yield. Antiepileptic screening of the title compounds was performed using MES and scPTZ seizures tests while the neurotoxicity was determined by rotorod test. In the preliminary screening, compounds 4d, 4e, 4p, 4q, and 4r were found active in MES model, while 4a, 4d, 4f, 4m, and 4p showed significant antiepileptic activity in scPTZ model. Further, all these eight compounds were administered to rats and compounds 4e, 4p, and 4q showed better activity than Phenytoin in oral route. Among these compounds 4p revealed protection in MES after i.p. administration at a dose of 30 mg/kg (0.5 h) and 100 mg/kg (4 h). The compound 4p also provided protection in the scPTZ at a dose of 100 mg/kg (0.5 h) and 300 mg/kg (4 h).

Full text of DOI:10.1007/s00044-012-0169-9

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:1711–1722
DOI 10.1007/s00044-012-0169-9
ORIGINAL RESEARCH
Synthesis and anticonvulsant activity of novel
quinazolin-4(3H)-one derived pyrazole analogs
•
Veerachamy Alagarsamy Govindaraj Saravanan
Received: 8 December 2011 / Accepted: 28 June 2012 / Published online: 11 July 2012
Ó Springer Science+Business Media, LLC 2012
Abstract Eighteen novel 6,8-(dibromo/unsubstituted)-2-
(methyl/phenyl)-3-(4-(5-(substitutedphenyl)-3-phenyl-4,5-dihy-
dro-1H-pyrazole-1-carbonyl)phenyl)-quinazolin-4(3H)-ones
4a–4r were designed and synthesized in good yield. Antiep-
ileptic screening of the title compounds was performed using
MES and scPTZ seizures tests while the neurotoxicity was
determined by rotorod test. In the preliminary screening,
compounds 4d, 4e, 4p, 4q, and 4r were found active in MES
model, while 4a, 4d, 4f, 4m, and 4p showed significant
antiepileptic activity in scPTZ model. Further, all these eight
compounds were administered to rats and compounds 4e, 4p,
and 4q showed better activity than Phenytoin in oral route.
Among these compounds 4p revealed protection in MES after
i.p. administration at a dose of 30 mg/kg (0.5 h) and 100 mg/
kg (4 h). The compound 4p also provided protection in the
scPTZ at a dose of 100 mg/kg (0.5 h) and 300 mg/kg (4 h).
worldwide (Bell and Sander, 2002). Based on the main
molecular mechanism of action currently used antiepileptic
drugs (AEDs), can be broadly classified into four major
categories as mentioned follow: (a) enhancement of
GABA-mediated inhibition or other effect on the GABA
system, (b) modulation of voltage-dependent Na? and/or
Ca2? channels, (c) modulation of synaptic release and
(d) inhibition of synaptic excitation mediated by ionotropic
glutamate receptors (Pollard and French, 2006). Currently,
a significant group of patients are resistant to the available
AEDs, hence there is a need for improved agents for the
treatment of seizure disorders. Polytherapy with AEDs is
necessary in clinical practice because of the limited effi-
cacy of monotherapy. The long established AEDs control
seizures in 50 % of patients developing partial seizures and
in 60–70 % of those developing generalized seizures
(Lopes Lima, 2000; Berk et al., 2001; Duncan, 2002).
Moreover, many AEDs have serious side effects such as
ataxia, drowsiness, gingival hyperplasia, gastrointestinal
disturbances, and megaloblastic anemia (Spear, 2001).
Toxicity, intolerance, and lack of efficacy are the limita-
tions of the current AEDs. All of these have stimulated
intensive research on novel AEDs. The complex mecha-
nism of action of most of the AEDs and the insufficient
information on the cellular mechanism of epilepsy in
human makes it difficult to use rational methodologies in
the field of drug discovery. Thus based on the existence of
different pharmacophores that were established through the
analysis of structural characteristics of clinically effective
drugs, as well as other antiepileptic compounds design of
new AEDs are needed (Karakurt et al., 2010; Deng et al.,
2010; Alam et al., 2010). It is well documented from the
literatures (Estrada and Pena, 2000; Bruno-Blanch et al.,
2003), that one of the important core fragments is defined
by the presence of (i) hydrogen donor/acceptor unit (HAD),
Keywords Quniazoline Á Pyrazole Á Epilepsy Á
In vivo studies Á Neurotoxicity
Introduction
Epilepsy is a common neurological disorder, affecting
a large section of population (45–100 million people)
V. Alagarsamy (&)
Medicinal Chemistry Research Laboratory, M.N.R. College
of Pharmacy, Sangareddy, Andhra Pradesh, India
e-mail: drvalagarsamy@gmail.com
G. Saravanan
Medicinal Chemistry Research Laboratory, Bapatla College
of Pharmacy, Jawaharlal Nehru Technological University,
Hyderabad, Andhra Pradesh, India
123

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Med Chem Res (2013) 22:1711–1722
(ii) one electron donor atom (D), and (iii) a hydrophobic
domain (A) (aryl ring substituted/unsubstituted). This
common template is found in the structures of well-estab-
lished first generation AEDs such as phenytoin/carbamaz-
epine or in the second generation AEDs or among the
newest drugs (e.g., 8 felbamate) and the drugs in clinical
trial (Fig. 1). For the development of novel therapeutics
based on the pharmacophore model much efforts devoted
in the recent years resulted in the availability of several
newer AEDs, such as lamotrigine, levetiracetam, pregab-
alin, stiripentol, tiagabine, topiramate, and zonisamide
(Stefan and Feuerstein, 2007). Therefore, the search for
new AEDs continues to be an active area of investigation in
medicinal chemistry.
step, 4-(6,8-(dibromo/unsubstituted)-2-(methyl/phenyl)-4-
oxoquinazolin-3(4H)-yl)benzoic acid 2a–2c were synthe-
sized through simple reaction by treating compounds 1a–1c
with p-amino benzoic acid with the elimination of water
molecule. On treating with thionyl chloride followed by
hydrazine hydrate, compounds 2a–2c gets converted to its
respective hydrazide derivatives 3a–3c. In the last step, the
compounds 4a–4r were synthesized by a ring closure
reaction, in which a different chalcones (a,b-unsaturated
carbonyl compound) and hydrazide derivative of quinazo-
line analog 3a–3c were reacted. TLC was performed
throughout the reactions to optimize the reactions for purity
and completion.
The structures of the synthesized compounds were
confirmed by elemental analysis and spectral (IR, 1H-
NMR, and Mass) data. Formation of the benzoxazine ring
in compound 1a/1b/1c was confirmed by the presence of
absorption peak at 1,706–1,751 and 1,038–1,055 cm-1 in
IR due to the presence of C=O and C–O–C stretching,
respectively. The formations of compound 2a/2b/2c were
confirmed by the appearance of broad peak in between
2,817 and 2,864 cm-1 in IR corresponds to O–H stretching
of COOH and appearance of singlet between d 9.84 and
10.01 ppm for single protons in its 1H-NMR spectra which
might be assigned to COOH group. The conversion of
hydrazide 3a/3b/3c from carboxylic acid 2a/2b/2c can be
recognized by strong absorption peak around 3,350 cm-1
in IR due to N–H stretching and appearance of singlet in its
1H-NMR spectra between d 3.47 and 3.71 ppm for two
protons which might be assigned to NH2 of hydrazide
group. The presence of –NH in hydrazide was confirmed
by appearance of singlet for single proton in 1H-NMR
spectra between d 8.35 and 8.45 ppm. The IR spectrum of
title compound 4e showed sharp absorption peaks at
3,581 cm-1 corresponding to O–H stretching vibration.
The multiple weak absorption peaks at 3,142 cm-1 corre-
sponds to Ar–H stretching vibration. The strong absorption
at 1,748 cm-1 is due to the C=O stretching vibration and
the moderate intensity absorption at 1,634 cm-1 corre-
sponds to a C=N stretching vibration. The weak absorption
at 1,618 cm-1 arises due to C=C stretching. The absorption
at 1,063 cm-1 is due to the C–O stretching vibration in C–
O–C. Its 1H-NMR spectrum showed a singlet at d
2.43 ppm due to the presence of CH3 at C2 of quinazoli-
none. Appearance of double doublet between d 3.16–3.19
and 3.68–3.71 ppm corresponds to C4–H1 and C4–H2 of
pyrazole, respectively. The presence of double doublet
between d 5.54 and 5.58 ppm confirms the presence of
The chemistry of quinazoline compounds has been the
subject of considerable interest due to their wide spectrum
of biological activity as many, such as anticonvulsant
(Kumar et al., 2011), anti-cancer (Abdel Gawad et al.,
2010), anti-tubercular (Pattan et al., 2006), anti-viral (Di-
nakaran et al., 2003), anti-microbial (Mohamed et al.,
2010), anti-helmintic (Shukla and Shukla, 1989), analgesic
and anti-inflammatory activity (Alagarsamy et al., 2005).
Quinazolin-4(3H)-one represents a good template for
preparation of some new anticonvulsant agents since such a
heterocyclic system possess the required pharmacophoric
moiety. In the arsenal of anticonvulsant agents, recently
pyrazole derivatives have constituted a vital part and its
worth has been proved by the progressive findings in the
literature. The anticonvulsant action of pyrazole moiety is
ascribed to its unique properties of being a two-electron
donor system and ability to act as a constrained pharma-
cophore at the receptor site (Abdel-Aziz et al., 2009;
Ozdemir et al., 2007, 2008).
Our precedingresearch on quinazolin-4(3H)-one derivative
as anticonvulsant agents driven us to continue synthesizing
newer derivatives in which intended to associate quinazolin-
4(3H)-one nucleus to the pyrazole moiety. Association of the
two active pharmacophores is expected to wield synergistic
effects to the resulting molecule. Based on these findings,
we have designed to synthesize a series of 6,8-(dibromo/
unsubstituted)-2-(methyl/phenyl)-3-(4-(5-(substituted phenyl)
-3-phenyl-4,5-dihydro-1H-pyrazole-1-carbonyl)phenyl)-
quinazolin-4(3H)-ones as potent anticonvulsant agents.
Results and discussion
The reaction sequence leading to the synthesis of titled
compounds 4a–4r is outlined in Scheme 1. The synthesis of
6,8-(dibromo/unsubstituted)-2-(methyl/phenyl)-4H-benzo-
[1,3]-oxazin-4-one 1a–1c involved a simple acetylation/
benzoylation of anthranilic acid/3,5-dibromo anthranilic
acid followed by ring closure reaction. In the subsequent
1
single proton in C5 of pyrazole. A singlet appeared in H-
NMR at d 5.72 ppm confirms the presence of hydroxyl
group. A group of signals appeared between d 7.32 and
8.59 ppm corresponds to Ar–H protons. Further, mass
spectrum confirmed their purity and molecular weight.
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Med Chem Res (2013) 22:1711–1722
1713
D
HAD
CH
A
A
O
OCH3
A
A
H
A
N
N
H3C
N
H
NH
H
O
O
D
N
O
D
HAD
N
H
O
H
HAD
Harkoseride
Phenytoin
Carbamazepine
F
D
H
H
N
D
N
D
N
O
A
CH3
N
N
A
N
Cl
HAD
H
Cl
N
H
F
O
N
N
H
N
H
HAD
N
HAD
O
A
H
Lamotrignine
Rufinamide
Ethotoin
HAD
H
HAD
CH3
N
O
CH3
NH2
A
N
H
O
A
N
H
NH2
D
F
O
B
O
D
B
F
NW 1015
Retigabine
R1
B
B
HAD
N
N
D
HAD
C
O
O
A
X
N
A
N
R
D
Y
Model compound structure
Fig. 1 Pharmacophoric pattern of well-known antiepileptics and model compound with its vital structuralfeatures: A hydrophobicarylringsystem,
HAD hydrogen bond acceptor/donor domain, D electron donor moiety, and B distal aryl ring
123

1714
Med Chem Res (2013) 22:1711–1722
COOH
O
N
O
X
COOH
NH2
X
X
O
N
(CH3CO)2O /
C6H5COCl
p-NH2C6H4COOH
Pyridine; 6 h
R
N
R
Y
Y
Y
(2a-2c)
Anthranilic acid /
3,5-dibromo anthranilic acid
(1a-1c)
1. SOCl2
7 h
O
2. NH2NH2. H2O
CONHNH2
1a, 2a, 3a : X= H, Y= H, R= CH3
1b, 2b, 3b : X= H, Y= H, R= C6H5
1c, 2c, 3c : X= Br, Y= Br, R= CH3
X
N
4a : X= H, Y= H, R= CH3, R1= 4-CH3
N
R
4b : X= H, Y= H, R= CH3, R1= 3-NO2
4c : X= H, Y= H, R= CH3, R1= 4-OCH3
4d : X= H, Y= H, R= CH3, R1= 4-Cl
4e : X= H, Y= H, R= CH3, R1= 4-OH
4f : X= H, Y= H, R= CH3, R1= 4-N(CH3)2
4g : X= H, Y= H, R= C6H5, R1= 4-CH3
Y
(3a-3c)
H
C
DMF
10 h
C
C
O
H
R1
4h : X= H, Y= H, R= C6H5, R1= 3-NO2
4i : X= H, Y= H, R= C6H5, R1= 4-OCH3
4j : X= H, Y= H, R= C6H5, R1= 4-Cl
4k : X= H, Y= H, R= C6H5, R1= 4-OH
4l : X= H, Y= H, R= C6H5, R1= 4-N(CH3)2
4m : X= Br, Y= Br, R= CH3, R1= 4-CH3
4n : X= Br, Y= Br, R= CH3, R1= 3-NO2
4o : X= Br, Y= Br, R= CH3, R1= 4-OCH3
4p : X= Br, Y= Br, R= CH3, R1= 4-Cl
4q : X= Br, Y= Br, R= CH3, R1= 4-OH
4r : X=Br, Y= Br, R= CH3, R1= 4-N(CH3)2
R1
N
C
N
O
O
X
N
N
R
(4a-4r)
Y
Scheme 1 Synthetic protocols of intermediate and target compounds 4a–4r
For the identification of antiepileptic activity in mice,
test compounds were administered i.p. and challenged by
maximal electroshock seizure test (MES) and subcutaneous
pentylenetetrazole (scPTZ) test. Compounds found to be
active in these seizure challenges are generally regarded to
be significantly useful candidates in treatment of partial,
generalized, and even absence seizures. The data regarding
the antiepileptic screening of all the compounds are
reported in Table 1.
of these compounds. The promising activity of the com-
pounds may be attributed to the substitutions at the
hydrophobic domain. These compounds contain electron
donating groups at the para position of the distal aryl ring.
In general, it was observed that the para-substituted
derivatives exhibited better activity than meta-substituted
derivatives. This may be because of the fact that the para-
substituted derivatives are better fitted into the receptor
site. After 0.5 h, at 100 mg/kg compounds 4a, 4c, 4f, 4j,
4k, 4m, and 4o were showed protection indicating the
ability of these compounds to protect from seizures at
relatively lower dose. These compounds except 4c and 4k
were also active after 4.0 h at 300 mg/kg dose.
Out of several tested compounds, four compounds 4d,
4e, 4p, 4q, and 4r were found to be significantly active in
the electroshock investigation as they showed protection at
the lowest dose of 30 mg/kg after 0.5 h. But at higher
doses (100 mg/kg) these compounds continued to show the
activity after 4.0 h except 4e, which needs 300 mg/kg
indicating the rapid onset as well as long duration of action
Most of the compounds exhibited moderate to good
antiepileptic activity in the scPTZ screening. Compounds
that revealed protection in the scPTZ test, indicating the
123

Med Chem Res (2013) 22:1711–1722
1715
ability of substance to increasing seizure threshold, at a
dose of B100 mg/kg after 0.5 h included 4a, 4d, 4f, 4m,
and 4p. The above results were comparable to results
obtained for ethosuximide which is recognized as reference
antiepileptic for this screen. Among all tested compounds,
4m was found to be remarkably active at a dose between 30
and 100 mg/kg after 0.5 h, as it continued to show activity
after 4.0 h at 300 mg/kg dose. Except 4g and 4l rest of
compounds 4b, 4c, 4e, 4h–4k, 4n–4o, 4q, and 4r were
active at 300 mg/kg either after 0.5 or 4.0 h. It was
observed that in this method, the most active compound
has substitution at aryl ring of quinazolinone by electron
releasing group resulted in increased antiepileptic activity.
Many compounds that are 4a, 4c–4h, 4j, 4k, 4m, and 4o–
4r were showed activity in either MES or scPTZ model at any
one of the tested dose after 0.5 h. The study reveals that 83 %
of the compounds that is 4a, 4c–4g, 4i–4m, and 4o–4r were
shown activity in MES screening, whereas in scPTZ test
except4g and 4l, restof89 % ofthe compoundswereactiveat
any one of the tested dose. These reports revealed that maxi-
mum of compounds possessed some scPTZ selectivity.
Neurotoxicity study was evaluated by rotorod test in mice.
The study revealed that most of the candidate compounds
exhibited neurotoxicity at doses higher than widely prescribed
drugs phenytoin or carbamazepine. But while evaluating an
antiepileptic compounds, separation between antiepileptic and
neurotoxic dose is desirable. All the compounds evaluated for
their neurotoxicitystudyexcept4b,4g,4h,4i,4l,and4n,dueto
their poor response in antiepileptic activity. In neurotoxic study
at 100 mg/kg dose 4e was found to be neurotoxic. Compounds
4c, 4d, 4j, 4m, 4o, 4q, and 4r were showed neurotoxicity at
300 mg/kg, while all other compounds 4a, 4f, 4k, and 4p were
not found to be neurotoxic at maximum administered dose.
Ability to inhibit epilepsy when given by the oral route
is a valuable property of candidate antiepilepsy. This
screen discloses the time of onset, the approximate time of
peak effect (TPE) and the duration of antiepileptic activity
or neurotoxicity. We identified eight compounds 4a, 4d,
4e, 4f, 4m, 4p, 4q, and 4r from the initial screen that were
further evaluated for oral availability using the MES acute
seizure model and neurotoxicity in rats at a dose of 30
mg/kg. The results obtained are presented in Table 2.
From these data, it was observed that the most active
compounds are 4e, 4p, and 4q which protected 100 % (4/4)
Table 1 Antiepileptic activity and neurotoxicity of compounds 4a–4r
administered intraperitoneally to mice
Compounds
MESa screening scPTZb screening NTc screening
0.5 hd 4.0 hd 0.5 hd
4.0 hd
0.5 hd 4.0 hd
4a
100
–
300
–
100
–
300
300
–
–
–
4b
ND
–
ND
300
–
4c
100
30
30
100
300
–
–
300
100
300
100
–
4d
100
300
300
–
300
300
300
–
300
100
–
4e
300
–
4f
4g
ND
ND
ND
–
ND
ND
ND
300
–
4h
–
300
–
–
4i
–
300
300
–
300
–
4j
100
100
–
300
–
4k
300
–
–
4l
300
300
–
–
ND
–
ND
300
ND
300
–
4m
100
–
[30e
300
300
–
4n
–
ND
300
–
Table 2 Antiepileptic activity and toxicity of compounds 4d, 4e, 4m,
4p, and 4q administered orally (30 mg/kg) to rats
4o
100
30
30
30
30
–
300
100
100
100
30
300
100
300
300
–
4p
300
300
–
Compounds
MESa
TOXb
4q
300
300
100
–
–
0.25 hc
0.5 hc
1 hc
2 hc
4 hc
4r
Phenytoinf
Ethosuximideg
300
100
–
4a
1/4
1/4
1/4
0/4
1/4
1/4
1/4
0/4
1/4
2/4
2/4
2/4
0/4
2/4
2/4
2/4
2/4
4/4
2/4
2/4
2/4
0/4
2/4
2/4
2/4
1/4
3/4
3/4
3/4
4/4
1/4
3/4
4/4
4/4
0/4
3/4
3/4
3/4
4/4
2/4
3/4
4/4
4/4
0/4
3/4
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
0/4 (–)d
–
–
100
300
4d
4e
The sign – (ndash) represents the absence of activity at maximum
dose administered (300 mg/kg)
4f
ND not determined
a
Maximal electroshock test (administered intraperitoneally to mice
at doses ranging from 30 to 300 mg/kg)
4m
4p
4q
b
Subcutaneous pentylenetetrazole test (administered intraperitone-
ally to mice at doses ranging from 30 to 300 mg/kg)
4r
Phenytoine
c
Neurotoxicity (administered intraperitoneally to mice at doses
ranging from 30 to 300 mg/kg)
a
Maximal electroshock test (dose of 30 mg/kg was administrated.
The data indicate: number of rats protected/number of rats tested)
d
Time of test after drug administration
b
e
Neurotoxicity (number of rats protected/number of rats tested)
scPTZ activity [30 means that the compound showed activity
between 30 and 100 mg/kg
c
Time after drug administration
f
d
Reference drug, data for phenytoin Ref. (Yogeeswari et al., 2005)
(–) No neurotoxicity at dose tested
g
e
Reference drug, data for ethosuximide ref (Rajak et al., 2009)
Reference drug, data for phenytoin ref (Yogeeswari et al., 2005)
123

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Med Chem Res (2013) 22:1711–1722
of rats at time points 2 and 4 h, 50 % (2/4) at 0.5 and 1 h
and 25 % (1/4) at 0.25 h. These molecules were more
active and showed longer duration of satisfactory action
than phenytoin. While, compounds 4a, 4d, and 4m were
found moderately effective in rat MES oral screen and
protected only 75 % (3/4) of rats at time points 2 and 4 h,
50 % (2/4) at 0.5 and 1 h, and 25 % (1/4) at 0.25 h. Rest of
tested compounds 4f and 4r were less effective and it
protected only 50 % (2/4) of tested animals at the time
point 0.5 h (4r) or 4 h (4f) and 25 % (1/4) at 1 h (4r) and
2 h (4f). All derivatives tested were non-neurotoxic when
given orally. The in vivo data in rats confirmed absorption
of compounds from gastrointestinal tract and also their
penetration to central nervous system. The inhibition of
electrically induced seizures that is characteristic for phe-
nytoin and phenytoin-like drugs may indicate the influence
of compound on voltage depended Na? channels as the
most plausible mechanism of antiepileptic action.
group and another hydrophobic distal aryl ring responsible
for controlling the pharmacokinetic properties of the anti-
epileptic. All eighteen title compounds were screened for
their antiepileptic activity by MES and scPTZ model along
with its neurotoxicity. In this series, generally compounds
possessing 2-methyl quinazolinone ring exhibited signifi-
cant antiepileptic activity in comparison to 2-phenyl qui-
nazolinone ring. Among the screened compounds 4d, 4e,
4p, 4q, and 4r were exhibited significant activity in MES
screening, while compound 4a, 4d, 4f, 4m, and 4p showed
significant antiepileptic activity in scPTZ model. These
eight compounds 4a, 4d, 4e, 4f, 4m, 4p, 4q, and 4r were
selected for oral administration in rats at 30 mg/kg dose.
Compounds 4e, 4p, and 4q exhibited better antiepileptic
activity in oral dose than standard drug phenytoin. The
most active one was 6,8-dibromo-3-(4-(5-(4-chlorophenyl)-
3-phenyl-4,5-dihydro-1H-pyrazole-1-carbonyl)phenyl)-2-
methylquinazolin-4-(3H)-one 4p that revealed protection
in the electrically induced seizures at a dose of 30 and
100 mg/kg (i.p.) after 0.5 and 4 h, respectively. This
molecule also provided protection in the scPTZ at a dose
of 100 and 300 mg/kg after 0.5 and 4 h, respectively.
Thus, the compound 4p emerged out as the lead molecule
with a wide spectrum of antiepileptic activity without any
neurotoxicity.
On correlating the structures of the sample candidate
with their biological activity, it has been observed that, out
of eighteen tested compounds 4a–4r, eight compounds 4a,
4d, 4e, 4f, 4m, 4p, 4q, and 4r exhibited better activity in
MES and/scPTZ test. All the above-mentioned compounds
were all 2-methyl quinazolinone derivative. The nature of
substituted group on C2 of quinazoline ring appeared to
greatly influence the antiepileptic activity; the 2-methyl
derivative 4a–4f and 4m–4r exhibited higher antiepileptic
activity than the 2-phenyl derivative 4g–4l. At the same
2-methyl derivative, the compound with electron donating
substitution at distal aryl ring 4a, 4c–4f, 4m, and 4o–4r
exhibited higher antiepileptic activity than the compound
with electron withdrawing substitution 4b and 4n. Among
electron donating groups p-Cl, p-OH, and p-CH3 substi-
tuted compounds 4a, 4d–4e, 4m, and 4p–4q exhibited
better activity. Moreover, p-OCH3 and p-N(CH3)2 substi-
tuted compounds 4c, 4f, 4o, and 4r had slightly decrease
antiepileptic activity. However, the m-NO2 derivative 4b
and 4n did not exhibit significant antiepileptic activity. The
increases in antiepileptic activity of test compounds with
2-methyl quinazolinone derivatives may be attributed due
to the presence of extra one electron releasing group on
quinazolinone ring (which is absent in 2-phenyl deriva-
tives) which might be accountable for additional bonding
with the binding site.
Experimental
General
The chemicals and reagents used were obtained from var-
ious chemical units Qualigens, E. Merck India Ltd., CDH,
and SD Fine Chem. These solvents used were of LR grade
and purified before their use. The silica gel G used for
analytical chromatography (TLC) was obtained from E.
Merck India Ltd. Solvent systems were used ethyl ace-
tate:hexane:formic acid (4:4:2). All the melting points
(m.p.) were taken in open glass capillary and are uncor-
rected. 1H-NMR spectra were taken on a Bruker ultra
shield (300 MHz) NMR spectrometer in CDCl3 using tet-
ramethylsilane [(CH3)4Si] as internal standard. Chemical
shift (d) are expressed in ppm. Mass spectra were obtained
on a JEOL-SX-102 instrument using electron impact ion-
ization. All the IR spectra were recorded in KBr pellets on
a Jasco FT-IR 410 spectrometer. Elemental analysis was
performed on a Perkin Elmer model 240c analyzer and
were within 0.4 % of the theoretical values.
In summary, majority of clinically active AEDs possess a
nitrogen hetero atomic system with one or more phenyl
rings, at least one carbonyl group and hydrogen donor/
acceptor unit. Remembering the above fact we have
designed and synthesized eighteen title compounds. The
structure of the title compounds 4a–4r satisfied all the
pharmacophoric structural requirements that is, the pres-
ence of quinazolin-4(3H)-one moiety as hydrophobic por-
tion, N as electron donor system, the presence of carbonyl
Synthesis of 6,8-(dibromo/unsubstituted)-bromo-2-(methyl/
phenyl)-4H-benzo-(1,3)-oxazin-4-one (1a–1c)
For the synthesis of 2-methyl derivative, a mixture of
anthranilic acid/3,5-dibromo anthranilic acid 1.37/2.94 g
123

Med Chem Res (2013) 22:1711–1722
1717
(0.01 mol) and acetic anhydride 10.2 ml (0.1 mol) was
refluxed on gentle flame for 1 h (4 h for dibromo deriva-
tives) (Alagarsamy et al., 2002, 2003). The excess of acetic
anhydride was distilled off under reduced pressure and the
residue was dissolved in petroleum ether and kept aside for
1 h. The light brown solid 1a/1c which obtained was fil-
tered and dried.
C–HStr), 2911 (CH3 C–HStr), 2817 (COOH), 1735 (cyclic
C=Ostr), 1628 (C=Nstr), 1615 (C=Cstr); 1H-NMR
(300 MHz, CDCl3, d ppm): 2.55 (s, 3H, CH3), 6.80–7.82
(m, 8H, Ar–H), 9.97 (s, 1H, COOH); MS (m/z): 280 [M?];
Anal. Calcd for C16H12N2O3: C, 68.56; H, 4.32; N, 9.99.
Found: C, 68.71; H, 4.30; N, 10.02.
To a solution of anthranilic acid 13.7 g (0.1 mol) dissolved
in pyridine (60 ml), benzoyl chloride 28 g (0.2 mol) was added
to synthesize 2-phenyl derivative. The mixture was stirred for
30 min followed by treatment with 5 % NaHCO3 (15 ml). The
solid 1b obtained was recrystallized from ethanol.
4-(4-Oxo-2-phenylquinazolin-3(4H)-yl)benzoic acid (2b)
Yield = 70 %; m.p. 148 °C; IR (KBr) cm-1: 3091 (Ar C–
H
Str), 2864 (COOH), 1743 (cyclic C=Ostr), 1619 (C=Nstr),
1608 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d ppm):
6.76–7.63 (m, 13H, Ar–H), 10.01 (s, 1H, COOH); MS (m/
z): 342 [M?]; Anal. Calcd for C21H14N2O3: C, 73.68; H,
4.12; N, 8.18. Found: C, 73.55; H, 4.13; N, 8.15.
2-Methyl-4H-benzo[d][1,3]oxazin-4-one (1a) Yield =
71 %; m.p. 182 °C; IR (KBr) cm-1: 3096 (Ar C–HStr), 2882
(CH3 C–HStr), 1712 (cyclic C=Ostr), 1636 (C=Nstr), 1600
(C=Cstr), 1055 (cyclic C–O–Cstr); 1H-NMR (300 MHz,
CDCl3, d ppm): 2.38 (s, 3H, CH3), 6.92–7.40 (m, 4H, Ar–H);
MS (m/z): 161 [M?]; Anal. Calcd for C9H7NO2: C, 67.07; H,
4.38; N, 8.69. Found: C, 67.16; H, 4.40; N, 8.66.
4-(6,8-Dibromo-2-methyl-4-oxoquinazolin-3(4H)-yl)ben-
zoic acid (2c) Yield = 72 %; m.p. 204 °C; IR (KBr)
cm-1: 3079 (Ar C–HStr), 2926 (CH3 C–HStr), 2842
(COOH), 1718 (cyclic C=Ostr), 1644 (C=Nstr), 1625 (C=
1
Cstr), 558 (C–Br); H-NMR (300 MHz, CDCl3, d ppm):
2.31 (s, 3H, CH3), 6.89–7.46 (m, 4H, Ar–H), 7.55 (s, 1H,
C7–H of quinazoline), 7.89 (s, 1H, C5–H of quinazoline),
9.84 (s, 1H, COOH); MS (m/z): 440 [M?2]; Anal. Calcd
for C16H10Br2N2O3: C, 43.87; H, 2.30; N, 6.39. Found: C,
43.77; H, 2.29; N, 6.41.
2-Phenyl-4H-benzo[d][1,3]oxazin-4-one (1b) Yield =
80 %; m.p. 120 °C; IR (KBr) cm-1: 3077 (Ar C–HStr),
1751 (cyclic C=Ostr), 1625 (C=Nstr), 1616 (C=Cstr), 1038
1
(cyclic C–O–Cstr); H-NMR (300 MHz, CDCl3, d ppm):
6.95–7.78 (m, 9H, Ar–H); MS (m/z): 223 [M?]; Anal.
Calcd for C14H9NO2: C, 75.33; H, 4.06; N, 6.27. Found: C,
75.42; H, 4.05; N, 6.29.
Synthesis of 4-[6,8-(dibromo/unsubstituted)-4-oxo-2-
(methyl/phenyl)quinazolin-3(4H)-yl]benzohydrazide
(3a–3c)
6,8-Dibromo-4H-benzo[d][1,3]oxazin-4-one
Yield = 74 %; m.p. 175 °C; IR (KBr) cm-1: 3060 (Ar C–
Str), 2938 (CH3 C–HStr), 1706 (cyclic C=Ostr), 1623
(1c)
To 4-[6,8-(dibromo/unsubstituted)-4-oxo-2-(methyl/phenyl)
quinazolin-3(4H)-yl]benzoicacid 2a/2b/2c 2.80/3.42/4.38 g
(0.01 mol), thionyl chloride 1.78 g (0.015 mol) was added
and refluxed for 1 h. Then the excess of thionyl chloride was
distilled off and the reaction mixture was cooled in ice bath.
The product formed was immediately used for next step.
To the above product 40 ml of ethanol was added. To
this solution 95 % hydrazine hydrate 1 g (0.02 mol) was
slowly added with stirring. Then the mixture was refluxed
for 6 h followed by removal of excess solvent under
reduced pressure and resultant solution was poured in ice
cold water. The product separated 3a/3b/3c was filtered
and recrystallised from ethanol.
H
(C=Nstr), 1609 (C=Cstr), 1047 (cyclic C–O–Cstr), 576 (C–
Br); 1H-NMR (300 MHz, CDCl3, d ppm): 2.43 (s, 3H,
CH3), 7.78 (s, 1H, C7–H of quinazoline), 8.07 (s, 1H, C5–H
of quinazoline); MS (m/z): 321 [M?2]; Anal. Calcd for
C9H5Br2NO2: C, 33.89; H, 1.58; N, 4.39. Found: C, 34.01;
H, 1.59; N, 4.41.
Synthesis of 4-[6,8-(dibromo/unsubstituted)-4-oxo-2-
(methyl/phenyl)quinazolin-3(4H)-yl]benzoic acid (2a–2c)
4H-benzo[d](1,3)-oxazin-4-one 1a/1b/1c 1.61/2.23/3.19 g
(0.01 mol) and p-amino benzoic acid 1.37 g (0.01 mol)
were dissolved in 50 ml of anhydrous pyridine and heated
on sand bath for 6 h. The resulting solution was cooled in
ice bath and treated with 100 ml of 1 N hydrochloric acid.
The product separated 2a/2b/2c was filtered, washed with
water and crystallized from ethanol.
4-(2-Methyl-4-oxoquinazolin-3(4H)-yl)benzohydrazide (3a)
Yield = 76 %; m.p. 233 °C; IR (KBr) cm-1: 3351 (NHstr),
3108 (Ar C–HStr), 2905 (CH3 C–HStr), 1740 (cyclic C=Ostr),
1637 (C=Nstr), 1618 (C=Cstr); 1H-NMR (300 MHz, CDCl3,
d ppm): 2.29 (s, 3H, CH3), 5.54 (s, 2H, –NH2), 6.83–8.05 (m,
8H, Ar–H), 8.48 (s, 1H, NH of hydrazide); MS (m/z): 294
[M?]; Anal. Calcd for C16H14N4O2: C, 65.30; H, 4.79; N,
19.04. Found: C, 65.43; H, 4.77; N, 18.98.
4-(2-Methyl-4-oxoquinazolin-3(4H)-yl)benzoic acid (2a)
Yield = 75 %; m.p. 218 °C; IR (KBr) cm-1: 3083 (Ar
123

1718
Med Chem Res (2013) 22:1711–1722
Yield = 81 %; m.p. 231–233 °C; Rf 0.70; IR (KBr) cm-1
:
4-(4-Oxo-2-phenylquinazolin-3(4H)-yl)benzohydrazide (3b)
Yield = 70 %; m.p. 180 °C; IR (KBr) cm-1: 3378 (NHstr),
3085 (Ar C–HStr), 1726 (cyclic C=Ostr), 1613 (C=Nstr),
3131 (Ar C–HStr), 2945 (CH3 C–HStr), 1728 (cyclic C=Ostr),
1619 (C=Nstr), 1603 (C=Cstr), 1534 and 1313 (C–NO2); 1H-
NMR (300 MHz, CDCl3, d ppm): 2.31 (s, 3H, CH3 of qui-
nazoline), 3.09–3.13 (dd, J = 5.2 Hz, 1H, C4–H1 of pyra-
zole), 3.76–3.80 (dd, J = 5.4 Hz, 1H, C4–H2 of pyrazole),
5.56–5.59 (dd, J = 5.6 Hz, 1H, C5–H of pyrazole),
7.13–8.37 (m, 17H, Ar–H); MS (m/z): 529 [M?]; Anal. Calcd
for C31H23N5O4: C, 70.31; H, 4.38; N, 13.23. Found: C,
70.19; H, 4.40; N, 13.18.
1
1605 (C=Cstr); H-NMR (300 MHz, CDCl3, d ppm): 5.71
(s, 2H, –NH2), 6.97–7.92 (m, 13H, Ar–H), 8.35 (s, 1H, NH
of hydrazide); MS (m/z): 356 [M?]; Anal. Calcd for
C21H16N4O2: C, 70.77; H, 4.53; N, 15.72. Found: C, 70.85;
H, 4.54; N, 15.66.
4-(6,8-Dibromo-2-methyl-4-oxoquinazolin-3(4H)-yl)ben-
zohydrazide (3c) Yield = 73 %; m.p. 247 °C; IR (KBr)
cm-1: 3365 (NHstr), 3097 (Ar C–HStr), 2892 (CH3 C–HStr),
1739 (cyclic C=Ostr), 1621 (C=Nstr), 1609 (C=Cstr), 570
3-(4-(5-(4-Methoxyphenyl)-3-phenyl-4,5-dihydro-1H-pyra-
zole-1-carbonyl)phenyl)-2-methylquinazolin-4(3H)-one (4c)
1
Yield = 78 %; m.p. 223–225 °C; Rf 0.83; IR (KBr) cm-1
:
(C–Br); H-NMR (300 MHz, CDCl3, d ppm): 2.34 (s, 3H,
CH3), 5.47 (s, 2H, –NH2), 6.85–7.69 (m, 4H, Ar–H), 7.71
(s, 1H, C7–H of quinazoline), 8.08 (s, 1H, C5–H of qui-
nazoline), 8.42 (s, 1H, NH of hydrazide); MS (m/z): 454
[M?2]; Anal. Calcd for C16H12Br2N4O2: C, 42.51; H,
2.68; N, 12.39. Found: C, 42.43; H, 2.67; N, 12.35.
3156 (Ar C–HStr), 2932 (CH3 C–HStr), 1725 (cyclic C=Ostr),
1643 (C=Nstr), 1621 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d
ppm): 2.15 (s, 3H, CH3 of quinazoline), 3.17–3.20 (dd,
J = 6.0 Hz, 1H, C4–H1 of pyrazole), 3.62–3.66 (dd,
J = 5.2 Hz, 1H, C4–H2 of pyrazole), 3.73 (s, 3H, –OCH3),
5.48–5.53 (dd, J = 5.8 Hz, 1H, C5–H of pyrazole), 7.47–8.50
(m, 17H, Ar–H); MS (m/z): 514 [M?]; Anal. Calcd for
C32H26N4O3: C, 74.69; H, 5.09; N, 10.89. Found: C, 74.86; H,
5.07; N, 10.86.
Synthesis of 6,8-(dibromo/unsubstituted)-2-(methyl/
phenyl)-3-(4-(5-(substituted phenyl)-3-phenyl-4,5-dihydro-
1H-pyrazole-1-carbonyl) phenyl)-quinazolin-4(3H)-one
(4a–4r)
3-(4-(5-(4-Chlorophenyl)-3-phenyl-4,5-dihydro-1H-pyr-
azole-1-carbonyl)phenyl)-2-methylquinazolin-4(3H)-one
(4d) Yield = 75 %; m.p. 196–198 °C; Rf 0.65; IR (KBr)
cm-1: 3119 (Ar C–HStr), 2923 (CH3 C–HStr), 1737 (cyclic
Different aromatic chalcones were prepared according to
the reported method (Kini and Gandhi, 2008). Various
aromatic chalcone (0.005 mol) was added to the 4-[6,8-
(dibromo/unsubstituted)-4-oxo-2-(methyl/phenyl)quinazo-
lin-3(4H)-yl]benzo hydrazide 3a/3b/3c 1.47/1.78/2.26 g
(0.005 mol) in 100-ml round bottom flask containing 25 ml
of N,N-dimethyl formamide. The above mixture was
refluxed at 120–140 °C for a period of 10 h. Then the
reaction mixture was cooled, poured into a beaker con-
taining ice cold water and kept aside for 24 h. The obtained
product 4a–4r was separated by filtration, dried over the
filter paper and recrystallised using ethanol.
1
C=Ostr), 1625 (C=Nstr), 1614 (C=Cstr), 852 (C–Cl); H-
NMR (300 MHz, CDCl3, d ppm): 2.72 (s, 3H, CH3 of
quinazoline), 3.06–3.11 (dd, J = 5.2 Hz, 1H, C4–H1 of
pyrazole), 3.75–3.78 (dd, J = 5.8 Hz, 1H, C4–H2 of pyr-
azole), 5.57–5.60 (dd, J = 5.6 Hz, 1H, C5–H of pyrazole),
7.19–8.26 (m, 17H, Ar–H); MS (m/z): 520 [M?2]; Anal.
Calcd for C31H23ClN4O2: C, 71.74; H, 4.47; N, 10.80.
Found: C, 71.92; H, 4.49; N, 10.77.
3-(4-(5-(4-Hydroxyphenyl)-3-phenyl-4,5-dihydro-1H-pyra-
zole-1-carbonyl)phenyl)-2-methylquinazolin-4(3H)-one (4e)
2-Methyl-3-(4-(3-phenyl-5-p-tolyl-4,5-dihydro-1H-pyrazole-
1-carbonyl)phenyl) quinazolin-4(3H)-one (4a) Yield =
76 %; m.p. 190–192 °C; Rf 0.78; IR (KBr) cm-1: 3115 (Ar
C–HStr), 2928 (CH3 C–HStr), 1744 (cyclic C=Ostr), 1631
(C=Nstr), 1609 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d
ppm): 2.19 (s, 3H, CH3 of quinazoline), 2.70 (s, 3H, Ar–
CH3), 3.14–3.16 (dd, J = 5.8 Hz, 1H, C4–H1 of pyrazole),
3.70–3.74 (dd, J = 5.6 Hz, 1H, C4–H2 of pyrazole),
5.51–5.54 (dd, J = 6.0 Hz, 1H, C5–H of pyrazole),
7.25–8.46 (m, 17H, Ar–H); MS (m/z): 498 [M?]; Anal.
Calcd for C32H26N4O2: C, 77.09; H, 5.26; N, 11.24. Found:
C, 76.94; H, 5.28; N, 11.21.
Yield = 74 %; m.p. 255–257 °C; Rf 0.89; IR (KBr) cm-1
3581 (OHstr), 3142 (Ar C–HStr), 2950 (CH3 C–HStr), 1748
:
1
(cyclic C=Ostr), 1634 (C=Nstr), 1618 (C=Cstr); H-NMR
(300 MHz, CDCl3, d ppm): 2.43 (s, 3H, CH3 of quinazo-
line), 3.16–3.19 (dd, J = 6.0 Hz, 1H, C4–H1 of pyrazole),
3.68–3.71 (dd, J = 5.6 Hz, 1H, C4–H2 of pyrazole),
5.54–5.58 (dd, J = 5.4 Hz, 1H, C5–H of pyrazole), 5.72 (s,
1H, OH), 7.32–8.59 (m, 17H, Ar–H); MS (m/z): 500 [M?];
Anal. Calcd for C31H24N4O3: C, 74.38; H, 4.83; N, 11.19.
Found: C, 74.49; H, 4.85; N, 11.16.
3-(4-(5-(4-(Dimethylamino)phenyl)-3-phenyl-4,5-dihydro-
1H-pyrazole-1-carbonyl) phenyl)-2-methylquinazolin-4(3H)
-one (4f) Yield = 82 %; m.p. 237–239 °C; Rf 0.80; IR
2-Methyl-3-(4-(5-(3-nitrophenyl)-3-phenyl-4,5-dihydro-1
H-pyrazole-1-carbonyl) phenyl)quinazolin-4(3H)-one (4b)
123

Med Chem Res (2013) 22:1711–1722
1719
(KBr) cm-1: 3136 (Ar C–HStr), 2931 (CH3 C–HStr), 1723
3.73–3.79 (dd, J = 5.6 Hz, 1H, C4–H2 of pyrazole),
5.54–5.59 (dd, J = 5.8 Hz, 1H, C5–H of pyrazole),
7.21–8.47 (m, 22H, Ar–H); MS (m/z): 582 [M?2]; Anal.
Calcd for C36H25ClN4O2: C, 74.41; H, 4.34; N, 9.64.
Found: C, 74.57; H, 4.36; N, 9.60.
1
(cyclic C=Ostr), 1648 (C=Nstr), 1622 (C=Cstr); H-NMR
(300 MHz, CDCl3, d ppm): 2.24 (s, 3H, CH3 of quinazo-
line), 2.87 (s, 6H, –N(CH3)2), 3.07–3.14 (dd, J = 5.4 Hz,
1H, C4–H1 of pyrazole), 3.65–3.72 (dd, J = 5.8 Hz, 1H,
C4–H2 of pyrazole), 5.49–5.55 (dd, J = 6.0 Hz, 1H, C5–H
of pyrazole), 7.16–8.35 (m, 17H, Ar–H); MS (m/z): 527
[M?]; Anal. Calcd for C33H29N5O2: C, 75.12; H, 5.54; N,
13.27. Found: C, 75.26; H, 5.52; N, 13.22.
3-(4-(5-(4-Hydroxyphenyl)-3-phenyl-4,5-dihydro-1H-pyra-
zole-1-carbonyl)phenyl)-2-phenylquinazolin-4(3H)-one (4k)
Yield = 78 %; m.p. 263–265 °C; Rf 0.81; IR (KBr) cm-1
:
3524 (OHstr), 3118 (Ar C–HStr), 1726 (cyclic C=Ostr), 1632
(C=Nstr), 1615 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d
ppm): 3.18–3.24 (dd, J = 5.8 Hz, 1H, C4–H1 of pyrazole),
3.70–3.76 (dd, J = 5.2 Hz, 1H, C4–H2 of pyrazole),
5.56–5.61 (dd, J = 5.6 Hz, 1H, C5–H of pyrazole), 5.85
(s, 1H, OH), 7.22–8.55 (m, 22H, Ar–H); MS (m/z): 562
[M?]; Anal. Calcd for C36H26N4O3: C, 76.85; H, 4.66; N,
9.96. Found: C, 77.01; H, 4.65; N, 9.93.
2-Phenyl-3-(4-(3-phenyl-5-p-tolyl-4,5-dihydro-1H-pyrazole-
1-carbonyl)phenyl) quinazolin-4(3H)-one (4g) Yield =
79 %; m.p. 199–201 °C; Rf 0.68; IR (KBr) cm-1: 3127 (Ar
C–HStr), 2941 (CH3 C–HStr), 1745 (cyclic C=Ostr), 1628
(C=Nstr), 1613 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d
ppm): 2.53 (s, 3H, Ar–CH3), 3.18–3.21 (dd, J = 6.2 Hz,
1H, C4–H1 of pyrazole), 3.77–3.80 (dd, J = 5.6 Hz, 1H,
C4–H2 of pyrazole), 5.55–5.60 (dd, J = 5.2 Hz, 1H, C5–H
of pyrazole), 7.30–8.54 (m, 22H, Ar–H); MS (m/z): 560
[M?]; Anal. Calcd for C37H28N4O2: C, 79.27; H, 5.03; N,
9.99. Found: C, 79.13; H, 5.05; N, 9.96.
3-(4-(5-(4-(Dimethylamino)phenyl)-3-phenyl-4,5-dihydro-
1H-pyrazole-1-carbonyl)
phenyl)-2-phenylquinazolin-4
(3H)-one (4l) Yield = 72 %; m.p. 258–260 °C; Rf 0.75;
IR (KBr) cm-1: 3133 (Ar C–HStr), 2926 (CH3 C–HStr),
1
1749 (cyclic C=Ostr), 1624 (C=Nstr), 1602 (C=Cstr); H-
3-(4-(5-(3-Nitrophenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-
carbonyl)phenyl)-2-phenylquinazolin-4(3H)-one (4h) Yield
= 75 %; m.p. 244–246 °C; Rf 0.87; IR (KBr) cm-1: 3145
(Ar C–HStr), 1722 (cyclic C=Ostr), 1646 (C=Nstr), 1629
NMR (300 MHz, CDCl3, d ppm): 2.83 (s, 6H, –N(CH3)2),
3.10–3.15 (dd, J = 5.4 Hz, 1H, C4–H1 of pyrazole), 3.68–
3.77 (dd, J = 5.8 Hz, 1H, C4–H2 of pyrazole), 5.52–5.58
(dd, J = 6.0 Hz, 1H, C5–H of pyrazole), 7.29–8.48 (m,
22H, Ar–H); MS (m/z): 589 [M?]; Anal. Calcd for
C38H31N5O2: C, 77.40; H, 5.30; N, 11.88. Found: C, 77.56;
H, 5.28; N, 11.84.
1
(C=Cstr), 1522 and 1319 (C–NO2); H-NMR (300 MHz,
CDCl3, d ppm): 3.11–3.17 (dd, J = 5.4 Hz, 1H, C4–H1 of
pyrazole), 3.71–3.75 (dd, J = 5.2 Hz, 1H, C4–H2 of pyr-
azole), 5.53–5.57 (dd, J = 5.8 Hz, 1H, C5–H of pyrazole),
7.25–8.46 (m, 22H, Ar–H); MS (m/z): 591 [M?]; Anal.
Calcd for C36H25N5O4: C, 73.09; H, 4.26; N, 11.84. Found:
C, 73.26; H, 4.27; N, 11.80.
6,8-Dibromo-2-methyl-3-(4-(3-phenyl-5-p-tolyl-4,5-dihy-
dro-1H-pyrazole-1-carbonyl) phenyl)quinazolin-4(3H)-
one (4m) Yield = 74 %; m.p. 206–208 °C; Rf 0.90; IR
(KBr) cm-1: 3095 (Ar C–HStr), 2921 (CH3 C–HStr), 1738
(cyclic C=Ostr), 1623 (C=Nstr), 1612 (C=Cstr), 574 (C–Br);
1H-NMR (300 MHz, CDCl3, d ppm): 2.45 (s, 3H, CH3 of
quinazoline), 2.66 (s, 3H, Ar–CH3), 3.22–3.24 (dd, J =
6.0 Hz, 1H, C4–H1 of pyrazole), 3.66–3.72 (dd, J = 5.2
Hz, 1H, C4–H2 of pyrazole), 5.49–5.53 (dd, J = 5.6 Hz,
1H, C5–H of pyrazole), 7.05–8.16 (m, 13H, Ar–H), 8.32 (s,
1H, C7–H of quinazoline), 8.50 (s, 1H, C5–H of quinazo-
line); MS (m/z): 658 [M?2]; Anal. Calcd for
C32H24Br2N4O2: C, 58.56; H, 3.69; N, 8.54. Found: C,
58.74; H, 3.68; N, 8.57.
3-(4-(5-(4-Methoxyphenyl)-3-phenyl-4,5-dihydro-1H-pyra-
zole-1-carbonyl)phenyl)-2-phenylquinazolin-4(3H)-one (4i)
Yield = 80 %; m.p. 235–237 °C; Rf 0.76; IR (KBr) cm-1
:
3109 (Ar C–HStr), 1743 (cyclic C=Ostr), 1635 (C=Nstr),
1616 (C=Cstr); 1H-NMR (300 MHz, CDCl3, d ppm):
3.19–3.23 (dd, J = 6.0 Hz, 1H, C4–H1 of pyrazole),
3.69–3.74 (dd, J = 5.4 Hz, 1H, C4–H2 of pyrazole), 3.81
(s, 3H, –OCH3), 5.50–5.55 (dd, J = 5.2 Hz, 1H, C5–H of
pyrazole), 7.15–8.34 (m, 22H, Ar–H); MS (m/z): 576 [M?];
Anal. Calcd for C37H28N4O3: C, 77.07; H, 4.89; N, 9.72.
Found: C, 76.96; H, 4.95; N, 9.75.
3-(4-(5-(4-Chlorophenyl)-3-phenyl-4,5-dihydro-1H-pyra-
zole-1-carbonyl)phenyl)-2-phenylquinazolin-4(3H)-one (4j)
6,8-Dibromo-2-methyl-3-(4-(5-(3-nitrophenyl)-3-phenyl-4,5-
dihydro-1H-pyrazole-1-carbonyl)phenyl)quinazolin-4(3H)-
one (4n) Yield = 77 %; m.p. 250–252 °C; Rf 0.62; IR
(KBr) cm-1: 3138 (Ar C–HStr), 2952 (CH3 C–HStr), 1746
(cyclic C=Ostr), 1645 (C=Nstr), 1623 (C=Cstr), 1541 and
1324 (C–NO2), 559 (C–Br); 1H-NMR (300 MHz, CDCl3, d
Yield = 73 %; m.p. 210–212 °C; Rf 0.72; IR (KBr) cm-1
3124 (Ar C–HStr), 1731 (cyclic C=Ostr), 1617 (C=Nstr),
:
1
1609 (C=Cstr), 868 (C–Cl); H-NMR (300 MHz, CDCl3, d
ppm): 3.09–3.15 (dd, J = 6.2 Hz, 1H, C4–H1 of pyrazole),
123

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Med Chem Res (2013) 22:1711–1722
6,8-Dibromo-3-(4-(5-(4-(dimethylamino)phenyl)-3-phenyl-
4,5-dihydro-1H-pyrazole-1-carbonyl)phenyl)-2-methylqui-
nazolin-4(3H)-one (4r) Yield = 75 %; m.p. 275–277 °C;
Rf 0.71; IR (KBr) cm-1: 3117 (Ar C–HStr), 2958 (CH3 C–
ppm): 2.18 (s, 3H, CH3 of quinazoline), 3.18–3.21 (dd,
J = 5.6 Hz,
1H,
C4–H1
of
pyrazole),
3.74–
3.78 (dd, J = 5.8 Hz, 1H, C4–H2 of pyrazole), 5.56–5.61
(dd, J = 5.4 Hz, 1H, C5–H of pyrazole), 7.21–8.07 (m,
13H, Ar–H), 8.20 (s, 1H, C7–H of quinazoline), 8.47 (s,
1H, C5–H of quinazoline); MS (m/z): 689 [M?2]; Anal.
Calcd for C31H21Br2N5O4: C, 54.17; H, 3.08; N, 10.19.
Found: C, 54.30; H, 3.07; N, 10.17.
H
Str), 1725 (cyclic C=Ostr), 1623 (C=Nstr), 1611 (C=Cstr),
1
562 (C–Br); H-NMR (300 MHz, CDCl3, d ppm): 2.49 (s,
3H, CH3 of quinazoline), 2.82 (s, 6H, –N(CH3)2), 3.10–
3.16 (dd, J = 5.2 Hz, 1H, C4–H1 of pyrazole), 3.69–3.73
(dd, J = 5.4 Hz, 1H, C4–H2 of pyrazole), 5.50–5.56 (dd,
J = 6.2 Hz, 1H, C5–H of pyrazole), 7.09–8.17 (m, 13H,
Ar–H), 8.35 (s, 1H, C7–H of quinazoline), 8.64 (s, 1H, C5–
H of quinazoline); MS (m/z): 687 [M?2]; Anal. Calcd for
C33H27Br2N5O2: C, 57.83; H, 3.97; N, 10.22. Found: C,
57.98; H, 3.95; N, 10.19.
6,8-Dibromo-3-(4-(5-(4-methoxyphenyl)-3-phenyl-4,5-dihy-
dro-1H-pyrazole-1-carbonyl)phenyl)-2methylquinazolin-4(3H)
-one (4o) Yield = 73 %; m.p. 239–241 °C; Rf 0.77; IR
(KBr) cm-1: 3146 (Ar C–HStr), 2938 (CH3 C–HStr), 1721
(cyclic C=Ostr), 1615 (C=Nstr), 1607 (C=Cstr), 572 (C–Br);
1H-NMR (300 MHz, CDCl3, d ppm): 2.34 (s, 3H, CH3 of
quinazoline), 3.07–3.12 (dd, J = 5.4 Hz, 1H, C4–H1 of
pyrazole), 3.65–3.69 (dd, J = 5.2 Hz, 1H, C4–H2 of pyr-
azole), 3.85 (s, 3H, –OCH3), 5.52–5.57 (dd, J = 5.8 Hz,
1H, C5–H of pyrazole), 7.17–8.25 (m, 13H, Ar–H), 8.46 (s,
1H, C7–H of quinazoline), 8.59 (s, 1H, C5–H of quinazo-
line); MS (m/z): 674 [M?2]; Anal. Calcd for
C32H24Br2N4O3: C, 57.16; H, 3.60; N, 8.33. Found: C,
57.32; H, 3.61; N, 8.31.
Pharmacology
All the synthesized compounds were evaluated for their
antiepileptic effects using male albino mice (Swiss
18–25 g) and rat (Wistar 100–150 g). The primary quali-
tative evaluations were performed in mice involved two
epilepsy tests (MES and scPTZ). Acute neurological tox-
icity induced by the compounds in mice was assessed
through standardized rotorod test. In the initial screening,
candidate compounds were screened for their antiepileptic
potential through MES and scPTZ models in mice at a dose
level of 30, 100, and 300 mg/kg by intraperitoneal (i.p.)
route and the groups of mice are tested at different time
points (i.e., 0.5 and 4 h) post administration of the test
candidate. It is generally acknowledged that the MES
model, which uses an electrical stimulus, induces general-
ized tonic–clonic seizures. Through electrical induction, it
is used to help recognize those compounds which prevent
seizure spread. The scPTZ is a model where the myoclonic
seizures induced by chemical induction. It helps in identi-
fying those compounds that might act by increasing seizure
threshold. Each group consisted of six animals. The animals
were maintained in colony cages at 25 2 °C, relative
humidity of 45–55 %, under a 12 h light and dark cycle;
were fed standard animal feed (Olfert et al., 1993). All the
animals were acclimatized for a week before use. The
Institutional Animal Ethics committee approved the proto-
col adopted for the experimentation of animals.
6,8-Dibromo-3-(4-(5-(4-chlorophenyl)3-phenyl-4,5-dihy-
dro-1H-pyrazole-1-carbonyl) phenyl)-2-methylquinazo-
lin-4(3H)-one (4p) Yield = 71 %; m.p. 227–229 °C; Rf
0.84; IR (KBr) cm-1: 3123 (Ar C–HStr), 2947 (CH3 C–
H
Str), 1734 (cyclic C=Ostr), 1639 (C=Nstr), 1605 (C=Cstr),
1
859 (C–Cl), 566 (C–Br); H-NMR (300 MHz, CDCl3, d
ppm): 2.52 (s, 3H, CH3 of quinazoline), 3.15–3.19 (dd,
J = 5.2 Hz, 1H, C4–H1 of pyrazole), 3.61–3.67 (dd,
J = 6.0 Hz, 1H, C4–H2 of pyrazole), 5.47–5.50 (dd,
J = 5.4 Hz, 1H, C5–H of pyrazole), 7.03–7.96 (m, 13H,
Ar–H), 8.13 (s, 1H, C7–H of quinazoline), 8.36 (s, 1H, C5–
H of quinazoline); MS (m/z): 678 [M?2]; Anal. Calcd for
C31H21Br2ClN4O2: C, 55.01; H, 3.13; N, 8.28. Found: C,
54.90; H, 3.14; N, 8.31.
6,8-Dibromo-3-(4-(5-(4-hydroxyphenyl)-3-phenyl-4,5-dihy-
dro-1H-pyrazole-1-carbonyl)phenyl)-2-methylquinazolin-4
(3H)-one (4q) Yield = 76 %; m.p. 281–283 °C; Rf 0.69;
IR (KBr) cm-1: 3540 (OHstr), 3091 (Ar C–HStr), 2919
(CH3 C–HStr), 1745 (cyclic C=Ostr), 1644 (C=Nstr), 1627
(C=Cstr), 553 (C–Br); 1H-NMR (300 MHz, CDCl3, d ppm):
2.26 (s, 3H, CH3 of quinazoline), 3.21–3.24 (dd, J = 5.8
Hz, 1H, C4–H1 of pyrazole), 3.77–3.81 (dd, J = 5.2 Hz,
1H, C4–H2 of pyrazole), 5.58–5.61 (dd, J = 5.6 Hz, 1H,
C5–H of pyrazole), 5.79 (s, 1H, –OH), 7.16–8.03 (m, 13H,
Ar–H), 8.18 (s, 1H, C7–H of quinazoline), 8.41 (s, 1H, C5–
H of quinazoline); MS (m/z): 660 [M?2]; Anal. Calcd for
C31H22Br2N4O3: C, 56.56; H, 3.37; N, 8.51. Found: C,
56.70; H, 3.36; N, 8.49.
Antiepileptic activity
The maximal electroshock test (MES)
The MES is a model for generalized tonic–clonic seizures
and provides a hint of a compound’s ability to stop seizure
spread when all neuronal circuits in the brain are maxi-
mally active. These seizures are extremely reproducible
and are electro physiologically reliable with human
123

Med Chem Res (2013) 22:1711–1722
1721
thank the management of Bapatla college of Pharmacy for providing
infrastructure facilities to carry out this research work.
seizures. For the MES, a drop of anesthetic and electrolyte
solution (tetracaine hydrochloride (0.5 %) in saline
(0.9 %)) was applied to the eyes of individual animal
before to placement of the corneal electrodes. The elec-
trical stimulus in the MES test was 50 mA, 60 Hz, for mice
and 150 mA, 60 Hz, for rats delivered for 0.2 s by an
apparatus similar to previously reported method (Wood-
bury and Davenport, 1952; White et al., 1995). Abolition
of the hindleg tonic extensor component of the seizure was
used as the endpoint. Mice are initially tested with different
doses of 30, 100, and 300 mg/kg of test compound given
by i.p. injection at various intervals while rats are initially
screened at a fixed dose of 30 mg/kg given by oral route.
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