Design, synthesis and anticonvulsant activities of novel 1-(substituted/unsubstituted benzylidene)-4-(4-(6,8-dibromo-2-(methyl/phenyl)-4- oxoquinazolin-3(4H)-yl)phenyl) semicarbazide derivatives

Article abstract of DOI:10.1016/j.bmcl.2012.03.068

Novel quinazolinone derivatives 5a-5n were designed, synthesized and screened for antiepileptic activity using MES and scPTZ seizures tests. Neurotoxicity study was performed by rotorod test. Compounds 5c, 5d, 5g, 5j and 5k were found active in the prelim

Full text of DOI:10.1016/j.bmcl.2012.03.068

Bioorganic & Medicinal Chemistry Letters 22 (2012) 3072–3078
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and anticonvulsant activities of novel 1-(substituted/
unsubstituted benzylidene)-4-(4-(6,8-dibromo-2-(methyl/phenyl)-
4-oxoquinazolin-3(4H)-yl)phenyl) semicarbazide derivatives
Govindaraj Saravanan a, , Veerachamy Alagarsamy b, Chinnasamy Rajaram Prakash c
⇑
a Medicinal Chemistry Research Laboratory, Bapatla College of Pharmacy, Jawaharlal Nehru Technological University, Hyderabad, Andhra Pradesh, India
b Medicinal Chemistry Research Laboratory, M.N.R. College of Pharmacy, Sangareddy, Andhra Pradesh, India
c Department of Medicinal Chemistry, DCRM Pharmacy College, Inkollu, Andhra Pradesh, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel quinazolinone derivatives 5a–5n were designed, synthesized and screened for antiepileptic activ-
ity using MES and scPTZ seizures tests. Neurotoxicity study was performed by rotorod test. Compounds
5c, 5d, 5g, 5j and 5k were found active in the preliminary screening in MES model and/or scPTZ model.
Further all these five compounds were administered to rats, 5c and 5d showed better activity than Phe-
nytoin in oral route. Among all the title compounds tested, the most active one was 5c that revealed pro-
tection in MES at a dose of 30 mg/kg (ip) after 0.5 and 4 h. This molecule also provided protection in the
scPTZ at a dose of 100 mg/kg (0.5 h) and 300 mg/kg (4 h).
Received 3 November 2011
Revised 5 March 2012
Accepted 19 March 2012
Available online 23 March 2012
Keywords:
Quinazolin-4(3H)-one
Schiff base
Ó 2012 Elsevier Ltd. All rights reserved.
Epilepsy
In vivo studies
Neurotoxicity
Epilepsy is a collective term that includes over 40 different
types of human seizure disorders.1 According to the International
League Against Epilepsy (ILAE), epilepsy is defined as a brain disor-
der characterized by an enduring predisposition to generate
epileptic seizures and by the neurobiological, cognitive, psycholog-
ical and social consequences of this condition.2 Approximately 1%
of the world population at any one time (ꢀ50 million people
worldwide) is affected with this serious neurological disorder.3 In
fact, epilepsy is the third most frequent neurological disorder
encountered in the elderly after cerebrovascular disease and
dementia.4 Based on the main molecular mechanism of action cur-
rently 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.5 Currently,
the main treatment for epileptic disorder is the long-term and con-
sistent administration of AEDs. Despite the increasing understand-
ing of the pathogenesis of seizures, about one third of epilepsies
are poorly treated with the available AEDs.6 Although over 30 AEDs
are available, 25–30% of patients fail to achieve adequate seizure
control, while others experience disturbing adverse effects such
as headache, nausea, anorexia, ataxia, hepatotoxicity, drowsiness,
gastrointestinal disturbance, gingival hyperplasia and hirsut-
ism.7–9 In recent times several new drugs such as topiramate,10
tiagabine,11 felbamate,12 zonisamide13 and vigabatrin14 have
emerged to treat epilepsy. Although these drugs have been shown
to be effective in controlling the seizures, their efficacy does not
appear to be superior to that of the established AEDs such as diphe-
nyl hydantoin, carbamazepine and valproate.15 Therefore, it is
essential to search for new chemical entities for the treatment of
epilepsy with greater efficacy and fewer side effects. The confor-
mational analysis of previously well established drugs (Fig. 1)
showed that for anticonvulsant activity, the model must be com-
prised of (i) hydrogen acceptor/donor unit (HAD), (ii) one electron
donor atom (D) and (iii) a hydrophobic domain (A) (aryl ring
substituted/unsubstituted).16,17
The importance of heterocyclic compounds has long been rec-
ognized in the field of synthetic organic chemistry. Currently, het-
erocyclic compounds have been extensively studied due to their
important properties and applications. It is well known that a
number of heterocyclic compounds containing nitrogen exhibited
a wide variety of biological activity. Among these compounds, qui-
nazolinone derivatives have become especially noteworthy in re-
cent years due to their wide spectrum of biological activity.18–24
In addition bromides in the form of simple salts are still used as
anticonvulsants in both veterinary and human medicine, although
the latter use varies from country to country. As a pharmaceutical,
⇑
Corresponding author. Mobile: +91 9963023257.
E-mail address: sarachem1981@gmail.com (G. Saravanan).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.03.068

G. Saravanan et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3072–3078
3073
D
HAD
CH
A
A
O
OCH3
A
A
H
N
A
N
H3C
N
H
NH
H
O
O
D
N
O
D
HAD
N
H
O
H
HAD
Harkoseride
Phenytoin
Carbamazepine
F
D
N
H
H
N
D
D
N
N
O
A
CH3
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
N
HAD
NH2
CH3
O
CH3
A
N
H
D
O
A
N
H
NH2
F
O
B
O
D
B
F
NW1015
Retigabine
H
N
H
N
HAD
O
C
N
B
A
R1
D
Br
O
N
HAD
A
N
R
D
Br
Model compound structure
Figure 1. Pharmacophoric pattern of well known antiepileptics and model compound with its vital structural features: (A) hydrophobic aryl ring system (HAD) hydrogen
bond acceptor/donor domain, (D) electron donor moiety and (B) distal aryl ring.
simple bromide ion has inhibitory effects on the central nervous
system, and bromide salts were once a major medical sedative, be-
fore being replaced by shorter-acting drugs. They retain niche uses
as antiepileptic. More over dibromo derivatives were reported to
possess various biological activities.25–27 6,8-Dibromoquinazolin-
4(3H)-one represents a good template for preparation of some
new anticonvulsant agents since such a heterocyclic system pos-
sess the required pharmacophoric moiety. On the other hand Schiff
bases have gained importance because of physiological and phar-
macological activities associated with them.28 Compounds con-
taining azomethine group (–C@N–) in the structure are known as
Schiff bases, which are usually synthesized by the condensation
of primary amines and active carbonyl groups. The anticonvulsant
action of Schiff base is ascribed to its unique properties of being an
electron donor system and ability to act as a constrained pharma-
cophore at the receptor site.
In the present study, we synthesized a series of novel 6,8-di-
bromo quinazolin-4(3H)-one derivative by substituting different
1-(substituted/unsubstituted benzylidene)-4-phenyl semicarbaz-
ide at the 3rd position and methyl/phenyl group at 2nd position.
Initially, 3,5-dibromanthranilic acid and acetic anhydride/benzoyl
chloride were used as starting materials to produce 6,8-dibro-
mo-2-(methyl/phenyl)-4H-benzo-(1,3)-oxazin-4-one 1a/1b by a
acetylation/benzoylation followed by ring closure reaction. In
the subsequent step, 3-(4-aminophenyl)-6,8-dibromo-2-(methyl/
phenyl)-quinazolin-4(3H)-one 2a/2b was synthesized through
simple reaction by treating compound 1a/1b with p-phenylene-
diamine with the elimination of water molecule. On stirring
with sodium cyanate and glacial acetic acid, compounds 2a/2b
gets converted to its respective urea derivatives 3a/3b. Before fi-
nal step, the compounds 3a/3b treated with hydrazine hydrate
to get respective semicarbazide derivatives 4a/4b. In the last
step, the compounds 5a–5n were synthesized by a Schiff base
reaction, in which a different aromatic aldehydes (carbonyl com-
pound) and amino derivative 4a/4b (Quinazolin-4(3H)-one ana-
Keeping all this in background, we tried to develop and explore
this particular class as potential anticonvulsant. In our present
study we made on attempt to synthesize different substituted ben-
zylidene semicarbazide derivatives containing quinazolin-4(3H)-
one moiety as antiepileptic agents.
log) undergoes nucleophilic addition, forming
a hemiaminal.
This reaction is followed by a dehydration to generate a title

3074
G. Saravanan et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3072–3078
compounds 5a–5n by forming a stable imine according to the
synthetic Scheme 1.
1724–1749 cmÀ1, and weak band at 1615–1649 cmÀ1, which can
be assignable to NH, C@O, and C@N vibrations, respectively. The fol-
lowing conclusions can be derived by comparing the NMR spectra of
synthesized compounds: (a) A singlet at d 2.17–2.45 ppm for 2-CH3
(only for 2-methyl quinazolinone derivative 5a–5g), (b) A multiplet
at d 6.75–8.16 ppm for Ar-CH, (c) A singlet at d 8.10–8.33 ppm for
C7–H of quinazolin-4(3H)-one, (d) A singlet at d 8.32–8.52 ppm
for C5–H of quinazolin-4(3H)-one, (e) A singlet at d 8.57–8.88 ppm
for Ar-NH, (f) A singlet at d 9.03–9.29 ppm for CH@N, (g) A singlet
at d 9.81–10.08 ppm for CONH. The physicochemical properties of
the synthesized compounds are given in Table 1.
For the identification of antiepileptic activity in mice, test com-
pounds were administered ip and challenged by maximal electro-
shock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure
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 2.
IR, 1H NMR, mass spectra, and elemental analyses of the synthe-
sized compounds are in accordance with the assigned structures.29
The IR spectra of all synthesized compounds showed some charac-
teristic peaks indicating the presence of particular groups. Forma-
tion of the 6,8-dibromo-4H-benzo-(1,3)-oxazin-4-one ring in
compound 1a/1b was confirmed by the presence of absorption peak
at 1706/1737 and 1047/1055 cmÀ1 in IR due to presence of C@O and
C–O–C stretching, respectively. The formations of compound 2a/2b
were confirmed by the absence of absorption bands around
1050 cmÀ1 corresponds to C–O–C stretching and appearance of peak
at 3360/3348 cmÀ1, respectivelyin IR corresponds to N–H stretching
of NH2. Appearance of singlet around d 3.83 ppm for two protons in
its 1H NMR spectra which might be assigned to NH2 group also con-
firms the formation of 2a/2b. In 1H NMR spectra appearance of a sin-
glet for single proton at d 8.55/8.61 ppm which might be assigned to
Ar-NH group of compound 3a/3b, respectively. Further presence of a
single proton in CONH of compound 4a/4b was confirmed by the
appearance of singlet at d 9.94/9.87 ppm. The IR spectrum of
Most of the compounds exhibited moderate to good antiepilep-
title compound shows absorption bands at 3341–3389 cmÀ1
,
tic activity in the MES screening.30,31 Out of several tested
NH2
O
O
Br
Br
COOH
NH2
Br
O
(CH3CO)2O /
C6H5COCl
p-NH2C6H4NH2
Pyridine; 6 h
N
N
R
N
R
Br (1a-1b)
Br
Br
(2a-2b)
3,5-Dibromoanthranilic acid
Glacial CH3COOH
NaOCN
Ethanol
H
N
NH2
O
N
C
O
Br
Br
Br
N
R
1a, 2a, 3a, 4a: R= CH3
1b, 2b, 3b, 4b: R= C6H5
Br
(3a-3b)
5a: R= CH3, R1= H
NH2NH2.H2O
5b: R= CH3, R1= 4-NO2
5c: R= CH3, R1= 4-OH
10-12 h
Ethanol
Reflux
5d: R= CH3, R1= 4-N(CH3)2
5e: R= CH3, R1= 3-NO2
H
N
H
N
5f: R= CH3, R1= 4-Cl
O
C
O
NH2
5g: R= CH3, R1= 4-OH-3OCH3
5h: R= C6H5, R1= H
5i: R= C6H5, R1= 4-NO2
5j: R= C6H5, R1= 4-OH
N
5k: R= C6H5, R1= 4-N(CH3)2
5l: R= C6H5, R1= 3-NO2
N
R
5m: R= C6H5, R1= 4-Cl
Br
(4a-4b)
5n: R= C6H5, R1= 4-OH-3OCH3
R1
Ethanol
Glacial CH3COOH
6-8 h
CHO
H
N
H
N
O
N
C
O
N
R1
N
R
Br
Title compounds (5a-5n)
Scheme 1. Synthetic protocols of title compounds 5a–5n.

G. Saravanan et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3072–3078
3075
Table 1
Physicochemical data of all synthesized test compounds 5a–5n
H
N
H
N
O
C
O
N
R1
Br
N
N
R
Br
Compound
R
R1
Mp (oC)
Yield (%)
Molecular formula
Analysis (%), found (calcd): C; H; N
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
H
4-NO2
4-OH
4-N(CH3)2
3-NO2
4-Cl
4-OH-3-OCH3
H
4-NO2
4-OH
4-N(CH3)2
3-NO2
4-Cl
148–150
235–237
226–228
251–253
192–194
274–276
286–288
197–199
269–271
189–191
156–159
257–259
209–211
238–240
75
70
71
77
73
70
72
75
78
71
74
80
76
72
C23H17Br2N5O2
C23H16Br2N6O4
C23H17Br2N5O3
C25H22Br2N6O2
C23H16Br2N6O4
C23H16Br2ClN5O2
C24H19Br2N5O4
C28H19Br2N5O2
C28H18Br2N6O4
C28H19Br2N5O3
C30H24Br2N6O2
C28H18Br2N6O4
C28H18Br2ClN5O2
C29H21Br2N5O4
49.58 (49.75); 3.10 (3.09); 12.65 (12.61)
46.14 (46.02); 2.68 (2.69); 13.97 (14.00)
48.51 (48.36); 2.99 (3.00); 12.22 (12.26)
50.06 (50.19); 3.70 (3.71); 14.01 (14.05)
46.13 (46.02); 2.68 (2.69); 14.05 (14.00)
46.99 (46.85); 2.72 (2.73); 11.85 (11.88)
48.04 (47.94); 3.18 (3.19); 11.69 (11.65)
54.66 (54.48); 3.11 (3.10); 11.32 (11.35)
50.59 (50.78); 2.75 (2.74); 12.73 (12.69)
53.23 (53.10); 3.01 (3.02); 11.02 (11.06)
54.71 (54.56); 3.67 (3.66); 12.76 (12.73)
50.90 (50.78); 2.73 (2.74); 12.64 (12.69)
51.46 (51.60); 2.79 (2.78); 10.78 (10.75)
52.68 (52.51); 3.18 (3.19); 10.53 (10.56)
4-OH-3-OCH3
to the substitutions at the hydrophobic domain. These compounds
contain electron donating groups such as hydroxy, dimethylamino
and methoxy group at the distal aryl ring. At a dose of 100 mg/kg,
after 0.5 h compounds5a, 5b, 5e, 5h, 5k and 5n were showed pro-
tection indicating the ability of these compounds to protect from
seizures at relatively lower dose. These compounds except 5b were
also active after 4.0 h at 300 mg/kg dose.
Table 2
Antiepileptic activity and neurotoxicity of compounds 5a–5n administered intraper-
itoneally to mice
Compound
MESa screening
scPTZb screening
NTc screening
0.5 hd
4.0 hd
0.5 hd
4.0 hd
0.5 hd
4.0 hd
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
100
100
30
300
—
30
300
—
100
100
300
—
—
—
—
300
300
300
—
—
—
300
—
Compounds that revealed protection in the scPTZ test32 repre-
senting the ability of substance to increasing seizure threshold.
Among entire tested compounds in scPTZ test, 5c, 5d, 5g and 5k
were found to be significantly active at a dose of 100 mg/kg after
0.5 h and these compounds continued to show activity after 4.0 h
at 300 mg/kg dose. The above results were equal to results ob-
tained for ethosuximide which is recognized as reference AEDs
for this screen. Except 5f and 5m, rest of compounds 5a, 5b, 5e,
5h, 5i, 5j, 5l and 5n were active at 300 mg/kg after 0.5 and/or
4.0 h. It was observed that in this method, the most active com-
pound have substitution at distal aryl ring by electron releasing
group resulted in increased antiepileptic activity.
30
30
300
300
ND
—
300
—
ND
—
100
300
30
100
—
300
—
100
300
—
—
100
300
300
300
100
—
300
300
—
300
300
300
—
100
ND
—
300
ND
300
—
30
100
—
300
300
—
—
ND
ND
100
100
—
ND
ND
300
100
—
—
—
—
100
30
300
30
300
—
—
—
Phenytoine
Ethosuximidef
—
—
100
300
Numerous compounds that are,5a, 5c–5e, 5g, 5h, 5j, 5k and 5n
were showed activity in either MES or scPTZ model at any one of
the tested dose after 0.5 h. The study reveals that 79% of the com-
pounds that is 5a–5h, 5j, 5k and 5n were shown activity in MES
screening, whereas in scPTZ test except 5f and 5m, rest of 86% of
the compounds were active at any one of the tested dose. This
information revealed that most of compounds possessed some
scPTZ selectivity. In general it was observed that the 2-methyl qui-
nazolin-4(3H)-one analogs exhibited better activity than corre-
sponding 2-phenyl quinazolin-4(3H)-one. This may be because of
the fact that the 2-methyl derivatives are better fitted into the
receptor site.
ND—Not determined.
The sign—(mdash) represents an absence of activity at maximum dose adminis-
tered (300 mg/kg).
a
Maximal electroshock test (administered intraperitoneally to mice at doses
ranging from 30 to 300 mg/kg).
b
Subcutaneous pentylenetetrazole test (administered intraperitoneally to mice
at doses ranging from 30 to 300 mg/kg).
c
Neurotoxicity (administered intraperitoneally to mice at doses ranging from 30
to 300 mg/kg).
d
Time of test after drug administration.
Reference drug, data for phenytoin Ref. 6.
Reference drug, data for ethosuximide Ref. 35.
e
f
The neurotoxicity study33,34 revealed that the majority of the
candidate compounds exhibited neurotoxicity at doses higher than
commonly prescribed drugs phenytoin or carbamazepine. But
while evaluating an antiepileptic compounds, separation between
antiepileptic and neurotoxic dose is desirable. Due to its poor re-
sponse in antiepileptic activity, apart from 5f, 5i, 5l and 5m, rest
of all compounds were screened for its neurotoxicity study. At
100 mg/kg dose 5h and 5n were found to be neurotoxic after
0.5 h. Compounds 5b, 5d, 5e and 5j were showed neurotoxicity
compounds in the electroshock investigation, four compounds 5c,
5d, 5g and 5j were found to be significantly active. Out of these
four compounds, 5c and 5d showed protection at the lowest dose
of 30 mg/kg after 0.5 h and 4.0 h. Whereas, compounds 5g and 5j
displayed protection at the lowest dose of 30 mg/kg after 0.5 h.
But at higher doses (100 mg/kg) compound 5g continued to show
the activity after 4.0 h while 5j needs 300 mg/kg dose indicating
the fast onset as well as long duration of action of these com-
pounds. The hopeful activity of the compounds may be ascribed

3076
G. Saravanan et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3072–3078
Table 3
antiepileptic activity. At the same electron donating substituted
derivative, 2-methyl quinazolin-4(3H)-one analog 5c, 5d and 5g
exhibited higher antiepileptic activity than the corresponding 2-
phenyl quinazolin-4(3H)-one analog 5j, 5k and 5n. The increases
in antiepileptic activity of test compounds with 2-methyl quinaz-
olinone derivatives may be attributed due to the presence of extra
one electron releasing group on quinazolinone ring (which is ab-
sent in 2-phenyl derivatives) which might be accountable for addi-
tional bonding with the binding site.
Antiepileptic activity and toxicity of compounds 5c, 5d, 5g, 5j and 5k administered
orally (30 mg/kg) to rats
Compound
MESa
1 hc
TOXb
0.25 hc
0.5 hc
2 hc
4 hc
5c
5d
5g
5j
2/8
2/8
0/8
0/8
0/8
2/8
6/8
6/8
4/8
0/8
1/8
8/8
7/8
7/8
2/8
0/8
3/8
6/8
8/8
8/8
0/8
2/8
0/8
6/8
8/8
8/8
0/8
4/8
0/8
6/8
0/8 (—)d
0/8 (—)d
0/8 (—)d
0/8 (—)d
0/8 (—)d
0/8 (—)d
5k
In summary, most of clinically active AEDs possess a nitrogen
hetero atomic system with one or more phenyl rings, at least one
carbonyl group and hydrogen acceptor/donor unit. Remembering
the above fact we have designed and synthesized novel 1-(substi-
tuted/unsubstituted benzylidene)-4-(4-(6,8-dibromo-2-(methyl/
phenyl)-4-oxoquinazolin-3(4H)-yl)phenyl)semicarbazide deriva-
tives. The structure of the title compounds 5a–5n satisfied all the
pharmacophoric structural requirements that is, presence of qui-
nazolin-4(3H)-one moiety as hydrophobic portion, N as electron
donor system, presence of carbonyl group and another hydropho-
bic distal aryl ring responsible for controlling the pharmacokinetic
properties of the antiepileptic. Entire title compounds were
screened for their antiepileptic activity by MES and scPTZ model.
The active compounds were also tested for its neurotoxicity. Gen-
erally in this series, electron donating groups containing com-
pound exhibited higher antiepileptic activity than the electron
withdrawing groups containing compound. At the same electron
donating substituted derivative, compounds possessing 2-methyl
quinazolinone ring exhibited significant antiepileptic activity in
comparison to 2-phenyl quinazolinone ring. Among the screened
compounds 5c, 5d, 5g, 5j and 5k were exhibited significant activity
in MES screening and/or scPTZ model. These five compounds were
selected for oral administration in rats at 30 mg/kg dose. Com-
pounds 5c and 5d exhibited better antiepileptic activity in oral
dose than standard drug Phenytoin. The most active one was 1-
(4-hydroxybenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-oxoqui-
nazolin-3(4H)-yl)phenyl) semicarbazide 5c that revealed protec-
tion in the electrically induced seizures at a dose of 30 mg/kg (ip)
after 0.5 and 4 h. This molecule also provided protection in the
scPTZ at a dose of 100 and 300 mg/kg after 0.5 and 4 h, respec-
tively. As a result the compound 5c emerged out as the pilot mol-
ecule with a broad spectrum of antiepileptic activity without any
neurotoxicity.
Phenytoine
a
Maximal electroshock test (dose of 30 mg/kg was administrated. The data
indicate: number of rats protected /number of rats tested).
b
Neurotoxicity (number of rats protected /number of rats tested).
Time after drug administration.
(—) No neurotoxicity at dose tested.
Reference drug.
c
d
e
at 300 mg/kg after 0.5 and/or 4.0 h, whereas all other compounds
5a, 5c, 5g and 5k were not found to be neurotoxic at maximum
administered dose.
Ability to inhibit epilepsy when given by the oral route is a valu-
able 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
five compounds 5c, 5d, 5g, 5j and 5k 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 3.
From these information it was observed that the most active
compounds are 5c and 5d which protected 100% (8/8) of rats at
time points 2 and 4 h, 88% (7/8) at 1 h, 75% (6/8) at 1 h, and 25%
(2/8) at 0.25 h. These molecules were more active and showed
longer duration of satisfactory action than phenytoin. The other
compounds 5g and 5j were moderately effective in rat MES oral
screen and protected only 50% (4/8) of tested animals at the time
point 0.5 and 4 h, respectively. Moreover these compounds 5g
and 5j protected 25% (2/8) of tested animals at 1 and 2 h, respec-
tively. Whereas 5k was found to be least effective, this compound
protected only 38% (3/8) of rats at 1 h and 13% (1/8) of tested ani-
mals at 0.5 h. All derivatives tested were non-neurotoxic when gi-
ven 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 phenytoin and phenytoin-like
drugs may point out the influence of compounds on voltage de-
pended Na+ channels as the most probable mechanism of antiepi-
leptic action.
On correlating the structures of the title compounds with their
biological activity, it has been observed that, out of several tested
compounds 5a–5n, four compounds 5c, 5d, 5g and 5j were found
to be active in MES method (at 30 mg/kg); whereas 5c, 5d, 5g
and 5k were found to be active against scPTZ test (at 100 mg/kg).
Out of these compounds except 5j and 5k, rest of compounds 5c,
5d and 5g were active in both MES and scPTZ test. All the above
mentioned five compounds that is, 5c, 5d, 5g, 5j and 5k contains
electron donating substituents at the hydrophobic domain (distal
aryl ring). The nature of substituted group at hydrophobic domain
appeared to greatly influence the antiepileptic activity; compounds
with electron releasing groups 5c, 5d, 5g, 5j, 5k and 5n exhibited
higher antiepileptic activity than the compounds containing elec-
tron withdrawing groups 5b, 5e, 5f, 5i, 5l and 5m. Among electron
donating groups p-OH substituted compounds 5c and 5j exhibited
better activity than p-N(CH3)2 and p-OH-m-OCH3 substituted com-
pounds 5d, 5g, 5k and 5n which had slighter lower activity. How-
ever, the unsubstituted derivative 5a and 5h exhibits moderate
Acknowledgments
The authors gratefully acknowledge the management of Bapatla
College of Pharmacy for providing infrastructure facilities to carry
out this research work. The authors are also wish to thank the Cen-
tral Instrumentation Facility, IIT Chennai, India for the spectral
analysis of the compounds used in this study.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2012.03.068.
References and notes
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Mp 186–188 °C; IR (KBr) cmÀ1: 3348 (NHstr); 3044 (Ar-CHstr); 1741 (C@O);
1639 (C@N); 683 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 3.94 (s, 2H, NH2);
6.89–7.95 (m, 9H, Ar-H); 8.23 (s, 1H, C7–H of quinazoline); 8.37 (s, 1H, C5–H of
quinazoline); MS (EI) m/z 473 [M+2]; Anal. Calcd for C20H13Br2N3O: C, 50.99; H,
2.78; N, 8.92. Found: C, 51.17; H, 2.77; N, 8.90.
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Synthesis
of
1-(4-(6,8-dibromo-2-(methyl/phenyl)-4-oxoquinazolin-3(4H)-
yl)phenyl)urea (3a-3b): Compound 2a/2b (4.09/4.71 g, 0.01 mol) was
dissolved in 10 mL glacial acetic acid and the volume was diluted to 100 mL
with the same in a conical flask. To it a solution of NaOCN (Sodium cyanate)
(0.65 g, 0.01 mol) and 50 mL of warm water was then added slowly with
continuous stirring. Then the reaction mixture was allowed to stand for
30 min, and then cooled in crushed ice, allowed to stand for further 30 min.
The product 3a/3b thus obtained was filtered and washed with cold water,
finally dried at 100 °C. The product was recrystallized at least once from
ethanol to give the pure form.
1-(4-(6,8-Dibromo-2-methyl-4-oxoquinazolin-3(4H)-yl)phenyl)urea (3a): Yield
70%, Mp 245–247 °C; IR (KBr) cmÀ1: 3375 (NHstr); 3059 (Ar-CHstr); 2952
(CH3-CHstr); 1720 (C@O of quinazoline); 1647 (C@N); 678 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 2.23 (s, 3H, CH3); 3.67 (s, 2H, NH2); 6.90–8.07 (m, 4H,
Ar-H); 8.26 (s, 1H, C7–H of quinazoline); 8.32 (s, 1H, C5–H of quinazoline); 8.55
(s, 1H, Ar-NH); MS (EI) m/z 454 [M+2]; Anal. Calcd for C16H12Br2N4O2: C, 42.51;
H, 2.68; N, 12.39. Found: C, 42.65; H, 2.69; N, 12.34.
22. Mohamed, M. S.; Kamel, M. M.; Kassem, E. M. M.; Abotaleb, N.; Abd-El-moez, S.
L.; Ahmed, M. F. Eur. J. Med. Chem. 2010, 45, 3311.
23. Shukla, J. S.; Shukla, R. J. Indian Chem. Soc. 1989, 66, 209.
24. Alagarsamy, V.; Rajasolomon, V.; Meena, R.; Ramseshu, K. V. Biol. Pharm. Bull.
2005, 1091, 28.
1-(4-(6,8-Dibromo-4-oxo-2-phenylquinazolin-3(4H)-yl)phenyl)urea (3b): Yield
76%, Mp 279–281 °C; IR (KBr) cmÀ1: 3381 (NHstr); 3075 (Ar-CHstr); 1739
(C@O of quinazoline); 1620 (C@N); 685 (C-Br); 1H NMR (300 MHz, CDCl3, d
ppm): 3.75 (s, 2H, NH2); 6.83–7.99 (m, 9H, Ar-H); 8.22 (s, 1H, C7–H of
quinazoline); 8.49 (s, 1H, C5–H of quinazoline); 8.61 (s, 1H, Ar-NH); MS (EI) m/z
516 [M+2]; Anal. Calcd for C21H14Br2N4O2: C, 49.05; H, 2.74; N, 10.90. Found: C,
49.21; H, 2.73; N, 10.87.
25. Panneerselvam, P.; Rather, B. A.; Reddy, D. R. S.; Kumar, N. R. Eur. J. Med. Chem.
2009, 44, 2328.
26. Changwen, Y.; Junhui, Y.; XiaoFeng, L.; Rong, Y.; Yabiao, W.; Jun, L.; Yuliang, W.
Pestic. Biochem. Phys. 2010, 97, 194.
27. Laddha, S. S.; Bhatnagar, S. P. Bioorg. Med. Chem. 2009, 17, 6796.
28. Wang, M.; Wang, L. F.; Li, Y. Z.; Li, Q. X.; Xu, Z. D.; Qu, D. M. Trans. Met. Chem.
2001, 26, 307.
Synthesis
of
4-(4-(6,8-dibromo-2-(methyl/phenyl)-4-oxoquinazolin-3(4H)-
yl)phenyl) semicarbazide (4a–4b): The compounds 3a/3b (4.52/5.14 g,
0.01 mol) was dissolved in 30 mL of absolute ethanol. To this 2.5 mL of
hydrazine hydrate was added and entire mixture was refluxed for 10–12 h
with stirring. The contents were concentrated to half of its volume and poured
onto crushed ice. The resultant precipitate was filtered, thoroughly washed
with water, dried and recrystallized from ethanol.
4-(4-(6,8-Dibromo-2-methyl-4-oxoquinazolin-3(4H)-yl)phenyl)semicarbazide
(4a): Yield 74%, Mp 215–217 °C; IR (KBr) cmÀ1: 3376 (NHstr); 3061 (Ar-CHstr);
2944 (CH3-CHstr); 1732 (C@O of quinazoline); 1628 (C@N); 659 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 2.31 (s, 3H, CH3); 5.79 (s, 2H, NH2); 6.94–7.86 (m, 4H,
Ar-H); 8.18 (s, 1H, C7–H of quinazoline); 8.35 (s, 1H, C5–H of quinazoline); 8.52
(s, 1H, Ar-NH); 9.94 (s, 1H, CONH); MS (EI) m/z 469 [M+2]; Anal. Calcd for
29. General: The chemicals and reagents used were obtained from various
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 acetate/Hexane/Formic acid (3:3:4). All
the melting points were taken in open glass capillary and are uncorrected. 1H
NMR spectra were taken on a Bruker ultra shield (300 MHz) NMR spectrometer
in CDCl3 using tetramethylsilane [(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 ionization. All the IR spectra were recorded
in KBr pellets on a Jasco FT-IR 410 spectrometer. Elemental analyses were
performed on a Perkine Elmer model 240C analyzer and were within 0.4% of
the theoretical values.
C16H13Br2N5O2: C, 41.14; H, 2.81; N, 14.99. Found: C, 41.28; H, 2.80; N, 14.94.
4-(4-(6,8-Dibromo-4-oxo-2-phenylquinazolin-3(4H)-yl)phenyl)semicarbazide
(4b): Yield 71%, Mp 294–296 °C; IR (KBr) cmÀ1: 3352 (NHstr); 3046 (Ar-CHstr),
1745 (C@O of quinazoline); 1631 (C@N); 660 (C-Br); 1H NMR (300 MHz, CDCl3,
d ppm): 5.81 (s, 2H, NH2); 7.01–8.04 (m, 9H, Ar-H); 8.25 (s, 1H, C7–H of
quinazoline); 8.38 (s, 1H, C5–H of quinazoline); 8.64 (s, 1H, Ar-NH); 9.87 (s, 1H,
CONH); MS (EI) m/z 531 [M+2]; Anal. Calcd for C21H15Br2N5O2: C, 47.66; H,
2.86; N, 13.23. Found: C, 47.81; H, 2.87; N, 13.18.
General procedure for the synthesis of 1-(substituted/unsubstituted benzylidene)-
4-(4-(6,8-dibromo-2-(methyl/phenyl)-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5a–5n): Title compounds (5a–5n) were synthesized
Synthesis of 6,8-dibromo-2-(methyl/phenyl)-4H-benzo-(1,3)-oxazin-4-one (1a–
1b): For the synthesis of 2-methyl derivative
a
mixture of 3,5-
dibromoanthranilic acid (2.95 g, 0.01 mol) and acetic anhydride (10.2 mL,
0.1 mol) was refluxed on gentle flame for 1 h. 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 which
obtained was filtered and dried.35
by
adding
4-(4-(6,8-dibromo-2-(methyl/phenyl)-4-oxoquinazolin-3(4H)-
To a solution of 3,5-dibromoanthranilic acid (29.5 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.25
6,8-Dibromo-2-methyl-4H-benzo-(1,3)oxazin-4-one (1a): Yield 69%, Mp 175 °C;
IR (KBr) cmÀ1: 3060 (Ar-CHstr); 2938 (CH3-CHstr); 1706 (C@O); 1623 (C@N);
1047 (Cyclic C–O–Cstr); 654 (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 (EI) 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.
yl)phenyl)semicarbazide 4a/4b (4.67/5.29 g, 0.01 mol) as fraction portions
with the well stirred mixture of different aromatic aldehydes (0.01 mol) in
ethanol (50 mL) and few mL of glacial acetic acid. Then this mixture was
refluxed for 6–8 h and kept aside. The product thus separated out was filtered,
dried and recrystallized from ethanol. The method used for the preparation and
isolation of the compounds gave materials of good purity, as evidenced by their
spectral analyses and by thin layer chromatography. The title compounds are
found to be soluble in chloroform, dimethyl sulfoxide, and
dimethylformamide.
1-Benzylidene-4-(4-(6,8-dibromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5a): IR (KBr) cmÀ1: 3345 (NHstr); 3081 (Ar-CHstr);
2957 (CH3-CHstr); 1744 (C@O of quinazoline); 1620 (C@N); 662 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 2.34 (s, 3H, CH3); 7.07–7.91 (m, 9H, Ar-H); 8.27 (s,
1H, C7–H of quinazoline); 8.45 (s, 1H, C5–H of quinazoline); 8.72 (s, 1H, Ar-NH);
9.09 (s, 1H, CH@N); 9.91 (s, 1H, CONH); MS (EI) m/z 557 [M+2].
1-(4-Nitrobenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5b): IR (KBr) cmÀ1: 3351 (NHstr); 3104 (Ar-CHstr);
2940 (CH3-CHstr); 1727 (C@O of quinazoline); 1649 (C@N); 1543 & 1318 (NO2);
696 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.17 (s, 3H, CH3); 6.93–8.04 (m,
8H, Ar-H); 8.30 (s, 1H, C7–H of quinazoline); 8.52 (s, 1H, C5–H of quinazoline);
8.69 (s, 1H, Ar-NH); 9.15 (s, 1H, CH@N); 9.88 (s, 1H, CONH); MS (EI) m/z 602
[M+2].
1-(4-Hydroxybenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5c): IR (KBr) cmÀ1: 3513 (OHstr); 3389 (NHstr); 3096
(Ar-CHstr); 2951 (CH3-CHstr); 1734 (C@O of quinazoline); 1632 (C@N); 671 (C-
Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.22 (s, 3H, CH3); 5.85 (s, 1H, OH); 6.86–
7.89 (m, 8H, Ar-H); 8.14 (s, 1H, C7–H of quinazoline); 8.37 (s, 1H, C5–H of
quinazoline); 8.61 (s, 1H, Ar-NH); 9.18 (s, 1H, CH@N); 10.03 (s, 1H, CONH); MS
(EI) m/z 573 [M+2].
6,8-Dibromo-2-phenyl-4H-benzo-(1,3)-oxazin-4-one (1b): Yield 72%, Mp 208 °C;
IR (KBr) cmÀ1: 3052 (Ar-CHstr); 1737 (C@O); 1626 (C@N); 1055 (Cyclic C–O–
C
str); 672 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 7.12–8.06 (m, 5H, Ar-H);
8.27 (s, 1H, C7–H of quinazoline); 8.41 (s, 1H, C5–H of quinazoline); MS (EI) m/z
383 [M+2]; Anal. Calcd for C14H7Br2NO2: C, 44.13; H, 1.85; N, 3.68. Found: C,
44.30; H, 1.84; N, 3.67.
Synthesis
of
3-(4-aminophenyl)-6,8-dibromo-2-(methyl/phenyl)-quinazolin-
4(3H)-one (2a–2b): 6,8-dibromo-2-(methyl/phenyl)-4H-benzo-(1,3)-oxazin-4-
one 1a/1b (3.19/3.81 g, 0.01 mol) and p-phenylenediamine (1.08 g, 0.01 mol)
was 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 dilute
hydrochloric acid. The product separated 2a/2b was filtered, washed with
water and crystallized from ethanol.
3-(4-Aminophenyl)-6,8-dibromo-2-methylquinazolin-4(3H)-one (2a): Yield 75%,
Mp 221–223 °C; IR (KBr) cmÀ1: 3360 (NHstr); 3077 (Ar-CHstr); 2935 (CH3–
CHstr); 1722 (C@O); 1644 (C@N); 666 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm):
2.36 (s, 3H, CH3); 3.72 (s, 2H, NH2); 7.03–8.12 (m, 4H, Ar-H); 8.30 (s, 1H, C7–H
of quinazoline); 8.56 (s, 1H, C5–H of quinazoline); MS (EI) m/z 411 [M+2]; Anal.
Calcd for C15H11Br2N3O: C, 44.04; H, 2.71; N, 10.27. Found: C, 43.89; H, 2.72; N,
10.30.
1-(4-(Dimethylamino)benzylidene)-4-(4-(6,8-dibromo-2-methyl-4-
oxoquinazolin-3(4H)-yl) phenyl)semicarbazide (5d): IR (KBr) cmÀ1: 3368 (NHstr);
2992 (Ar-CHstr); 2936 (CH3-CHstr); 1743 (C@O of quinazoline); 1615 (C@N);
3-(4-Aminophenyl)-6,8-dibromo-2-phenylquinazolin-4(3H)-one (2b): Yield 73%,

3078
G. Saravanan et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3072–3078
657 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.45 (s, 3H, CH3); 2.98 (s, 6H,
N(CH3)2); 6.78–7.81 (m, 8H, Ar-H); 8.19 (s, 1H, C7–H of quinazoline); 8.40 (s,
1H, C5–H of quinazoline); 8.57 (s, 1H, Ar-NH); 9.04 (s, 1H, CH@N); 9.86 (s, 1H,
CONH); MS (EI) m/z 600 [M+2].
(OHstr); 3374 (NHstr); 3097 (Ar-CHstr); 1737 (C@O of quinazoline); 1625
(C@N); 668 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 3.69 (s, 3H, OCH3); 5.70
(s, 1H, OH); 6.98–7.99 (m, 12H, Ar-H); 8.22 (s, 1H, C7–H of quinazoline); 8.41 (s,
1H, C5–H of quinazoline); 8.85 (s, 1H, Ar-NH); 9.08 (s, 1H, CH@N); 9.86 (s, 1H,
CONH); MS (EI) m/z 665 [M+2].
Pharmacology: The animals used in the present study such as Swiss albino mice
weighing 20–25 g and Wistar rats weighing 150–200 g were procured from
Bapatla College of Pharmacy, Bapatla, India. Animals were maintained in
colony cages at 25 2 °C, relative humidity of 45–55%, maintained under 12 h
light and dark cycle and were fed with standard animal feed and water ad
libitum. Animals were maintained under standard conditions in an animal
house approved by committee for the purpose of control and supervision on
experiments on animals (CPCSEA). Institutional Animal Ethics Committee
approved the experimental protocol. The entire animals were acclimatized for
a week before use.
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 maximally active. These
seizures are extremely reproducible and are electro physiologically reliable
with human 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 electrical
stimulus in the MES test was 50 milliampere, 60 Hz, for mice and
150 milliampere, 60 Hz, for rats delivered for 0.2 seconds by an apparatus
similar to that initially described by Woodbury and Davenport.30,31 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 ip injection at various intervals while rats are initially
screened at a fixed dose of 30 mg/kg given by oral route.
The subcutaneous pentylenetetrazole seizure test (scPTZ): Subcutaneous injection
of the convulsant Pentylenetetrazole produces clonic seizures in laboratory
animals. The scPTZ test detects the ability of test compounds to raise the
seizure threshold of an animal and thus protect it from exhibiting a clonic
seizure. Animals are pretreated with various doses of the test compound given
by ip injection. The dose of Pentylenetetrazole which induce convulsions in
97% of animals (CD97: 85 mg/kg mice) is injected into a loose fold of skin in the
midline of the neck. The animals are placed in isolation cages to minimize
stress32 and observed for the next 30 min for the presence or absence of a
seizure. An episode of clonic spasms, approximately 3–5 s, of the fore and/or
hindlimbs, jaws, or vibrissae is taken as the endpoint. Animals which do not
meet this criterion are considered protected.
1-(3-Nitrobenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5e): IR (KBr) cmÀ1: 3343 (NHstr); 3070 (Ar-CHstr);
2934 (CH3-CHstr); 1738 (C@O of quinazoline); 1635 (C@N); 1548 & 1315 (NO2);
683 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.19 (s, 3H, CH3); 6.95–8.08 (m,
8H, Ar-H); 8.25 (s, 1H, C7–H of quinazoline); 8.51 (s, 1H, C5–H of quinazoline);
8.84 (s, 1H, Ar-NH); 9.27 (s, 1H, CH@N); 9.99 (s, 1H, CONH); MS (EI) m/z 602
[M+2].
1-(4-Chlorobenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-oxoquinazolin-3(4H)-
yl)phenyl)semicarbazide (5f): IR (KBr) cmÀ1: 3372 (NHstr); 3085 (Ar-CHstr);
2948 (CH3-CHstr); 1736 (C@O of quinazoline); 1627 (C@N); 753 (C–Cl); 669 (C-
Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.30 (s, 3H, CH3); 7.02–8.16 (m, 8H, Ar-
H); 8.33 (s, 1H, C7–H of quinazoline); 8.49 (s, 1H, C5–H of quinazoline); 8.71 (s,
1H, Ar-NH); 9.15 (s, 1H, CH@N); 9.92 (s, 1H, CONH); MS (EI) m/z 591 [M+2].
1-(4-Hydroxy-3-methoxybenzylidene)-4-(4-(6,8-dibromo-2-methyl-4-
oxoquinazolin-3(4H)-yl) phenyl)semicarbazide (5g): IR (KBr) cmÀ1: 3520 (OHstr);
3357 (NHstr); 3106 (Ar-CHstr); 2943 (CH3-CHstr); 1729 (C@O of quinazoline);
1631 (C@N); 675 (C-Br); 1H NMR (300 MHz, CDCl3, d ppm): 2.26 (s, 3H, CH3);
3.64 (s, 3H, OCH3); 5.77 (s, 1H, OH); 6.99–7.95 (m, 7H, Ar-H); 8.29 (s, 1H, C7–H
of quinazoline); 8.32 (s, 1H, C5–H of quinazoline); 8.65 (s, 1H, Ar-NH); 9.07 (s,
1H, CH@N); 9.84 (s, 1H, CONH); MS (EI) m/z 603 [M+2].
1-Benzylidene-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-3(4H)-
yl)phenyl)semicarbazide (5h): IR (KBr) cmÀ1: 3365 (NHstr); 3053 (Ar-CHstr);
1731 (C@O of quinazoline); 1636 (C@N); 664 (C-Br); 1H NMR (300 MHz, CDCl3,
d ppm): 7.11–8.04 (m, 14H, Ar-H); 8.26 (s, 1H, C7–H of quinazoline); 8.39 (s,
1H, C5–H of quinazoline); 8.76 (s, 1H, Ar-NH); 9.03 (s, 1H, CH@N); 10.08 (s, 1H,
CONH); MS (EI) m/z 619 [M+2].
1-(4-Nitrobenzylidene)-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-3(4H)-
yl)phenyl)semicarbazide (5i): IR (KBr) cmÀ1: 3380 (NHstr); 3097 (Ar-CHstr); 1745
(C@O of quinazoline); 1618 (C@N); 1539 & 1312 (NO2); 698 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 6.84–7.90 (m, 13H, Ar-H); 8.15 (s, 1H, C7–H of
quinazoline); 8.48 (s, 1H, C5–H of quinazoline); 8.82 (s, 1H, Ar-NH); 9.16 (s, 1H,
CH@N); 9.87 (s, 1H, CONH); MS (EI) m/z 664 [M+2].
1-(4-Hydroxybenzylidene)-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-3(4H)-
yl)phenyl)semicarbazide (5j): IR (KBr) cmÀ1: 3516 (OHstr); 3348 (NHstr); 3052
(Ar-CHstr); 1735 (C@O of quinazoline); 1623 (C@N); 680 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 5.62 (s, 1H, OH); 6.97–8.01 (m, 13H, Ar-H); 8.21 (s,
1H, C7–H of quinazoline); 8.46 (s, 1H, C5–H of quinazoline); 8.73 (s, 1H, Ar-NH);
9.29 (s, 1H, CH@N); 9.81 (s, 1H, CONH); MS (EI) m/z 635 [M+2].
1-(4-(Dimethylamino)benzylidene)-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-
3(4H)-yl)phenyl)semicarbazide (5k): IR (KBr) cmÀ1: 3341 (NHstr); 3068 (Ar-
CHstr); 2944 (CH3-CHstr); 1732 (C@O of quinazoline); 1624 (C@N); 665 (C-Br);
1H NMR (300 MHz, CDCl3, d ppm): 2.83 (s, 6H, N(CH3)2); 7.04–8.13 (m, 13H, Ar-
H); 8.28 (s, 1H, C7–H of quinazoline); 8.50 (s, 1H, C5–H of quinazoline); 8.88 (s,
1H, Ar-NH); 9.14 (s, 1H, CH@N); 9.95 (s, 1H, CONH); MS (EI) m/z 662 [M+2].
1-(3-Nitrobenzylidene)-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-3(4H)-
yl)phenyl)semicarbazide (5l): IR (KBr) cmÀ1: 3382 (NHstr); 3108 (Ar-CHstr); 1724
(C@O of quinazoline); 1637 (C@N); 1542 and 1320 (NO2); 689 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 6.82–7.92 (m, 13H, Ar-H); 8.10 (s, 1H, C7–H of
quinazoline); 8.37 (s, 1H, C5–H of quinazoline); 8.74 (s, 1H, Ar-NH); 9.19 (s, 1H,
CH@N); 10.01 (s, 1H, CONH); MS (EI) m/z 664 [M+2].
1-(4-Chlorobenzylidene)-4-(4-(6,8-dibromo-4-oxo-2-phenylquinazolin-3(4H)-
yl)phenyl)semicarbazide (5m): IR (KBr) cmÀ1: 3356 (NHstr); 3083 (Ar-CHstr);
1749 (C@O of quinazoline); 1642 (C@N); 766 (C–Cl); 674 (C-Br); 1H NMR
(300 MHz, CDCl3, d ppm): 6.75–7.87 (m, 13H, Ar-H); 8.17 (s, 1H, C7–H of
quinazoline); 8.33 (s, 1H, C5–H of quinazoline); 8.68 (s, 1H, Ar-NH); 9.25 (s, 1H,
CH@N); 9.94 (s, 1H, CONH); MS (EI) m/z 653 [M+2].
Acute toxicity-minimal motor impairment: To assess a compound’s undesirable
side effects (toxicity), animals are monitored for overt signs of impaired
neurological or muscular function. In mice, the rotorod33,34 procedure is used
to disclose minimal muscular (MMI) or neurological impairment (MNI). When
a mouse is placed on a rod that rotates at a speed of 6 rpm, the animal can
maintain its equilibrium for long periods of time. The animal is considered
toxic if it falls off this rotating rod three times during a 1 min period. In
addition to MMI, animals may exhibit a circular or zigzag gait, abnormal body
posture and spread of the legs, tremors, hyperactivity, lack of exploratory
behavior, somnolence, stupor, catalepsy, loss of placing response and changes
in muscle tone.
30. Woodbury, L. A.; Davenport, V. D. Arch. Int. Pharmacodyn. Ther. 1952, 92, 97.
31. White, H. S.; Johnson, M.; Wolf, H. H.; Kupferberg, H. J. Ital. J. Neurol. Sci. 1995,
16, 73.
32. Swinyard, E. A.; Clark, L. D.; Miyahara, J. T.; Wolf, H. H. J. Physiol. 1961, 132, 97.
33. Dunham, M. S.; Miya, T. A. J. Am. Pharm. Assoc. Sci. 1957, 46, 208.
34. Rajak, H.; Deshmukh, R.; Aggarwal, N.; Kashaw, S.; Kharya, M. D.; Mishra, P.
Arch. Pharm. 2009, 342, 453.
35. Alagarsamy, V.; Muruganantham, G.; Venkateshaperumal, R. Biol. Pharm. Bull.
2003, 26, 1711.
1-(4-Hydroxy-3-methoxybenzylidene)-4-(4-(6,8-dibromo-4-oxo-2-
phenylquinazolin-3(4H)-yl)phenyl)semicarbazide (5n): IR (KBr) cmÀ1
: 3511