Design and synthesis of anticonvulsants from a combined phthalimide-GABA-anilide and hydrazone pharmacophore

Article abstract of DOI:10.1016/j.ejmech.2006.08.010

Two series of pharmacophoric hybrids of phthalimide-GABA-anilides/hydrazones were designed and synthesized and evaluated for their anticonvulsant and neurotoxic properties. The structures of the synthesized compounds were confirmed by the use of their spe

Full text of DOI:10.1016/j.ejmech.2006.08.010

European Journal of Medicinal Chemistry 42 (2007) 146e151
http://www.elsevier.com/locate/ejmech
Original article
Design and synthesis of anticonvulsants from a combined
phthalimideeGABAeanilide and hydrazone
pharmacophore
Jegadeesan Vaigunda Ragavendran a, Dharmarajan Sriram a, Sravan Kumar Patel a,
Ingala Vikram Reddy a, Narayanan Bharathwajan a, James Stables b,
Perumal Yogeeswari a,
*
a Medicinal Chemistry Research Laboratory, Pharmacy Group, Birla Institute of Technology and Science, Vidya Vihar,
Pilani, Rajasthan 333031, India
b Epilepsy Branch, National Institutes of Health, Bethesda, MD, USA
Received 17 May 2006; received in revised form 19 July 2006; accepted 11 August 2006
Available online 28 September 2006
Abstract
Two series of pharmacophoric hybrids of phthalimideeGABAeanilides/hydrazones were designed and synthesized and evaluated for their
anticonvulsant and neurotoxic properties. The structures of the synthesized compounds were confirmed by the use of their spectral data besides
elemental analysis. Initial anticonvulsant screening was performed using intraperitoneal (i.p.) maximal electroshock-induced seizure (MES),
subcutaneous pentylenetetrazole (scPTZ), subcutaneous strychnine (scSTY), and intraperitoneal picrotoxin (ipPIC)-induced seizure threshold
tests. All of the compounds were ineffective in the MES test. Most of the compounds were found to be effective in the scSTY and ipPIC models
and very few compounds showed protection in the scPTZ model.
Ó 2006 Elsevier Masson SAS. All rights reserved.
Keywords: Anticonvulsants; Phthalimides; GABA; Pentylenetetrazole; Picrotoxin; Strychnine; Acid hydrazones; Amides
1. Introduction
CNS disorders in humans, namely anxiety, pain, and epilepsy
[5e7]. The peripheral administration of GABA cannot be use-
fully performed since this neurotransmitter is able to cross the
bloodebrain diffusion barrier (BBB) only when extremely
high doses are applied, which produce severe adverse side ef-
fects [8]. Hence, over the past few decades, research aimed at
achieving successful delivery of GABA into the CNS has re-
sulted in the discovery of various GABA analogs with im-
proved pharmacological activities [9]. In particular, due to
the promising anticonvulsant activity exhibited by various
substituted N-phenyl phthalimide derivatives [10e14], the
phthalimide pharmacophore has been incorporated into the
structure of GABA in an attempt to increase its lipophilicity
[15e18]. The simple N,N-phthaloyl GABA was reported to
be active against MES, scPTZ, bicuculline and 3-mercaptopro-
pionic acid-induced seizures [16], but possessed a low
Epilepsy is a collective term given to a group of syndromes
that involve spontaneous, intermittent, abnormal electrical ac-
tivity in the brain, which manifest as seizures. Worldwide, ep-
ilepsy is a major health problem affecting about 1e2% of the
population [1]. 4-Aminobutyric acid (GABA) is the principal
inhibitory neurotransmitter in the mammalian brain [2,3]. It
has been estimated that approximately 40% of synapses in
the central nervous system (CNS) are GABAergic [4]. Also,
it is well documented that attenuation of GABAergic neuro-
transmission is involved in the pathophysiology of several
* Corresponding author. Tel.: þ91 1596 244684; fax: þ91 1596 244183.
E-mail address: pyogee@bits-pilani.ac.in (P. Yogeeswari).
0223-5234/$ - see front matter Ó 2006 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.08.010

J.V. Ragavendran et al. / European Journal of Medicinal Chemistry 42 (2007) 146e151
147
therapeutic index. In contrast, studies by Bialer and co-
workers [18] and Scriba [19] showed no anticonvulsant activ-
ity for N,N-phthaloyl GABA. Nevertheless, with an aim to
reduce the toxicity and improve the anticonvulsant activity
of N,N-phthaloyl GABA, various amide derivatives involving
aliphatic [17] and benzyl [19,20] amines were reported. In
view of the above reports, the present work is aimed at com-
bining the pharmacophoric features of phthalimide, GABA,
and anilides (Design #1 in Fig. 1) by synthesizing amide deriv-
atives of GABA and coupled with phthalimide. In another
study combination of phthalimide, GABA, and acid hydra-
zones (Design #2 in Fig. 1) was achieved by synthesizing
acid hydrazone derivatives of phthalimido GABA. The latter
modification was carried out, as various acid hydrazones
have been reported earlier as potent anticonvulsants [21,22].
in Tables 1 and 2. The chemical shifts obtained from 1H NMR
spectra confirmed the proposed structures. The COeNH pro-
ton resonated at d w 9.8e10.01 ppm and 10.7e11.2 ppm for
compounds 1e10 and 11e26, respectively. The aryl ring pro-
tons resonated at d w 6.7e8.2 ppm.
3. Results and discussion
The anticonvulsant activity of the titled compounds (1e26)
was determined using four animal models of seizure which in-
cluded maximal electroshock seizure (MES), subcutaneous
pentylenetetrazole (scPTZ), subcutaneous strychnine (scSTY),
and intraperitoneal picrotoxin (ipPIC)-induced seizure thresh-
old tests. The acute neurological toxicity was determined in
the rotarod test. The results are summarized along with the
data for standard drugs in Tables 1 and 2. All of the com-
pounds were ineffective in the MES test up to 300 mg/kg
(data not shown). Compounds that showed protection in the
scPTZ screen include 4, 6, 7, 10, 12, 21, and 24. These com-
pounds except 12 were found to be more potent when com-
pared to the standard drugs, phenytoin and ethosuximide.
Compounds effective at the dose of 30 mg/kg were 7 (4 h),
10 (4 h), and 21 (0.5 h). All the compounds except 6, 7, 9,
12e15, and 20e23 were effective against scSTY-induced sei-
zure threshold test. Compounds effective at the dose of
100 mg/kg were 1, 4, 11, 16e19, and 24e25. In the ipPIC-
induced seizure threshold test, all of the synthesized compounds
except 13 and 20 showed protection. Compound 4 was found to
be the most active compound in this study against ipPIC test as it
showed protection at 30 mg/kg at 0.5 h after administration. The
greater effectiveness of these compounds in ipPIC model sug-
gests that these compounds act by GABA mediation. Com-
pounds 4, 10, and 24 exhibited protection in all the three
animal models of seizure, viz. scPTZ, scSTY, and ipPIC. Com-
pounds 6, 7, 12, and 21 were active in the scPTZ and ipPIC
2. Synthesis
The synthetic protocols employed for the preparation of
N-aryl substituted 4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)
butanamides (1e10) and N-aryl/alkylidene-4-(1,3-dioxo-1,3-
dihydro-2H-isoindol-2-yl)butanoyl hydrazides (11e26) are
presented in Scheme 1. The 4-(1,3-dioxo-1,3-dihydro-2H-iso-
indol-2-yl)-N-(substituted phenyl)butanamides were obtained
by reaction of N-protected GABA with different substituted
anilines to give 1e10 in yields ranging between 47% and
75%. The N-aryl/alkylidene-4-(1,3-dioxo-1,3-dihydro-2H-iso-
indol-2-yl)butanoylhydrazones were obtained via reaction of
N-protected GABA with hydrazine hydrate after activation of
GABA with N,N0-dicyclohexyl carbodiimide (DCC), and sub-
sequently with variously substituted aldehydes and ketones to
give 11e26 in yields ranging between 32% and 78%. The pu-
rity was assessed by TLC; and the assignments of the struc-
tures were based on elemental and spectroscopic methods.
The physical data of the synthesized compounds are presented
O
R'
H
R
N
N
HN
R
R"
N
R
O
O
O
DESIGN#1
DESIGN#2
H2N
COOH
LINKER
O
O
H
H
N
N
N
N
N
O
O
O
R'
R"
O
R
1-10
11-26
Fig. 1. Anticonvulsant compounds designed by pharmacophore combination.

148
J.V. Ragavendran et al. / European Journal of Medicinal Chemistry 42 (2007) 146e151
O
O
reflux ( 3h)
Toluene
O
COOH
H2N
+
N
H5C2
C2H5
N
O
COOH
O
C2H5
CH2Cl2
(0-3°C)
CH2Cl2
(0-3°C)
NH2.NH2.H2O
R1
R2
O
NH2
O
N
R1
N
CONHNH2
R3CHO / R3COR4
O
CONH
O
(6-8h)
1-10
AcOH
EtOH
R2
O
N
R3
R4
N
NH
O
O
11-26
Scheme 1. Synthetic protocol of the titled compounds.
models, while compounds 1e3, 5, 8, 11, and 16e19 were active
in the scSTYand ipPIC models. Compounds that were found to
be completely inactive up to 300 mg/kg in any of these models
were 13 and 20. In the neurotoxicity screening, the acid
hydrazones except 17 and 21 showed no neurotoxicity at the
maximum dose tested (300 mg/kg) compared to the amide de-
rivatives except 9. All of the amide derivatives were neurotoxic
at the anticonvulsant dose. Overall with respect to effectiveness,
the amide derivatives (1e10) were more potent than acid hydra-
zones (11e26) in scPTZ (40% vs 12.5%), scSTY (70% vs 44%)
Table 1
Physical and anticonvulsant data of 4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-(substituted phenyl)butanamides
Compound R1
R2
Yield (%) M.P. (ꢀC)a ClogPb Rfc Intraperitoneal injection in miced
scPTZ screen
0.5 h 4 h
scSTY screen
ipPIC screen
Neurotoxicity screen
0.5 h
4 h
0.5 h
4 h
0.5 h
4 h
1
2
3
4
5
6
7
8
9
10
H
4-Cl
65
148e150 3.55
163e166 3.72
130e132 3.01
162e164 2.73
150e152 3.69
139e142 4.06
135e138 3.69
149e152 3.32
151e154 3.63
142e144 3.90
0.62
0.59
0.64
0.45
0.56
e
e
e
e
e
e
e
100
300
300
100
300
e
300
e
300
300
300
30
e
e
30
e
300
300
e
H
2-CF3 55
3-F 47
H
e
300
300
300
e
300
100
e
300
e
300
100
100
100
300
e
2-CH3
2-CH3
4-Br
6-CH3 58
5-CH3 75
3-CH3 67
4-CH3 54
4-CH3 51
100
e
e
300
300
300
300
300
e
300
100
300
300
100
100
e
0.58 100
2-CH3
H
0.62
0.61
0.65
e
e
e
30
e
e
e
e
300
e
e
e
e
H
3-Cl
2-Br
2-CH3 67
52
300
300
e
e
0.63 300
30
e
300
e
e
300
100
e
100
100
e
Phenytoin
Ethosuximide
e
e
e
e
e
e
e
e
e
300
e
e
e
e
e
e
a
b
c
d
Elemental analyses for C, H, N were within ꢁ0.4% of the theoretical values.
ClogP was calculated using www.logp.com.
Mobile phase CHCl3eCH3OH (9:1).
Doses of 30, 100 and 300 mg/kg were administered. The figures in the table indicate the minimum dose whereby bioactivity was demonstrated in half or more
of the mice. The dash (e) indicates an absence of activity at the maximum dose administered (300 mg/kg).

J.V. Ragavendran et al. / European Journal of Medicinal Chemistry 42 (2007) 146e151
149
Table 2
Physical and anticonvulsant data of N-aryl/alkylidene-4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)butanoyl hydrazides
Compound R3
R4
Yield (%) M.P. (ꢀC)a ClogPb Rfc Intraperitoneal injection in miced
scPTZ screen scSTY screen
ipPIC screen
Neurotoxicity screen
0.5 h
4 h
0.5 h
4 h
0.5 h
4 h
0.5 h
4 h
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
H
H
H
H
H
C6H5
55
55
47
58
152e155 3.14
158e160 3.08
154e157 3.10
140e143 3.08
129e132 2.48
150e154 3.05
165e169 3.01
151e154 2.99
158e161 2.57
152e155 2.11
147e150 3.50
169e172 2.34
143e147 4.27
168e171 2.49
167e169 3.00
147e150 3.03
0.71
0.61 300
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
100
e
100
e
100
300
e
300
300
100
300
100
100
e
100
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
100
e
3-NO2-C6H4
4-NO2-C6H4
2-OH-C6H4
e
0.64
0.57
0.71
0.76
0.53
0.56
0.49
0.68
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
4-OH, 3-OCH3-C6H3 78
e
e
e
e
CH3 C6H5
54
51
52
67
32
45
67
75
35
48
72
e
100
100
100
100
e
100
e
100
e
100
e
300
e
e
CH3 4-NO2-C6H4
CH3 2-OH-C6H4
CH3 4-OH-C6H4
CH3 3-NH2-C6H4
CH3 4-CH3-C6H4
C2H5 CH3
300
e
e
e
e
e
0.45 30
e
e
e
e
300
300
300
100
300
300
e
e
e
100
e
0.54
0.69
e
e
C6H5 C6H5
e
e
e
e
Cyclopentylene
Cyclohexylene
5-Chloro isatinyl
Phenytoin
0.55 100
100
100
e
e
e
e
e
e
e
0.57
0.67
e
e
e
e
e
e
e
e
e
e
e
300
e
e
e
100
e
Ethosuximide
e
e
e
e
e
e
a
b
c
d
Elemental analyses for C, H, N were within ꢁ0.4% of the theoretical values.
ClogP was calculated using www.logp.com.
Mobile phase CHCl3eCH3OH (9:1).
Doses of 30, 100 and 300 mg/kg were administered. The figures in the table indicate the minimum dose whereby bioactivity was demonstrated in half or more
of the mice. The dash (e) indicates an absence of activity at the maximum dose administered (300 mg/kg).
and ipPIC (100% vs 88%) while in consideration to neurotoxic-
ity, the acid hydrazones were less neurotoxic than the amide de-
rivatives. The compounds of this study exhibited comparable
lipophilicity (Tables 1 and 2) indicating that lipophilicity alone
cannot account for differences in anticonvulsant activity but
rather a better fit into a putative molecular target due to favor-
able steric interactions.
Themostactivecompoundofthisstudywasfoundtobe4-(1,3-
dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-(2,6-dimethylphenyl)bu-
tanamide (4) as it is effective at both the time-points observed ex-
cept in the scPTZ model. The activity due to this combination of
phthalimido pharmacophore and 2,6-dimethylphenyl pharmaco-
phore is in accordance with the earlier reports in which the 2,6-di-
methyl anilide, ameltolide was proved to be the most potent
compound with an ED50 of 2.6 mg/kg. Recently, we reported a se-
ries of 2,6-dimethylphenyl semicarbazones [23] as potent anticon-
vulsants. Hence the 2,6-dimethylphenyl functionality plays an
important role in the anticonvulsant action of these compounds.
5. Experimental protocols
5.1. Chemistry
Melting points were determined in open capillary tubes on
a Buchi 530 melting point apparatus and are uncorrected. Infra-
red (IR) and proton nuclear magnetic resonance (1H NMR)
spectra were recorded for the compounds on JASCO IR Report
100 (KBr) and Brucker Avance (300 MHz) instruments, respec-
tively. Chemical shifts are reported in parts per million (ppm)
using tetramethyl silane (TMS) as an internal standard. All ex-
changeable protons were confirmed by the addition of D2O. El-
emental analyses (C, H, and N) were undertaken with a Perkine
Elmer model 240C analyzer and all analyses were consistent
with theoretical values (within ꢁ0.4%) unless indicated. The
homogeneity of the compounds was monitored by ascending
thin layer chromatography (TLC) on silica gel-G (Merck)-
coated aluminium plates, visualized by iodine vapor and UV
light. The eluant system was chloroformemethanol (9:1).
5.1.1. General procedure for the preparation of 4-(1,3-di-
oxo-1,3-dihydro-2H-isoindol-2-yl)-N-(substituted phenyl)-
butanamides (1e10)
4. Conclusions
The present study reports the synthesis of pharmacophoric
combinations of phthalimideeGABAeanilide/hydrazones as
candidate anticonvulsants. Of the two series of pharmaco-
phoric hybrids, the phthalimideeGABAeanilides were found
to be more effective than the corresponding phthalimideeGA-
BAehydrazone derivatives.
N-protection of GABA was achieved by the reaction of
GABA (0.05 mol) with phthalic acid anhydride (0.05 mol),
with concomitant removal of water [19]. Equimolar quantities
of N,N-phthaloyl GABA (0.03 mol) and substituted anilines
(0.03 mol) were condensed in the presence of DCC (0.03 mol)
in dichloromethane, by stirring at ice-cold conditions (0e3 ꢀC)

150
J.V. Ragavendran et al. / European Journal of Medicinal Chemistry 42 (2007) 146e151
for 6e8 h [24]. The IR spectra of 4-(1,3-dioxo-1,3-dihydro-2H-
isoindol-2-yl)-N-(substituted phenyl)butanamides (1e10) were
identical in the following aspects: 3345, 3030, 1785,
1640 cmꢂ1; 1H NMR (DMSO) d (ppm) spectra of some repre-
sentative compounds are as follows.
2H, CH2), 2.2 (t, 2H, CH2), 3.6 (t, 2H, CH2), 7.7e8.12 (m,
8H, Aryl-H), 8.1 (s, 1H, Carbimino-H), 11.2 (s, 1H, CONH,
D2O exchangeable).
5.1.2.3. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )-
(2-hydroxyphenyl)methylene]butanoyl hydrazide (14). 1.92
(m, 2H, CH2), 2.1 (t, 2H, CH2), 3.62 (t, 2H, CH2), 6.7e7.7
(m, 8H, Aryl-H), 8.1 (s, 1H, Carbimino-H), 9.8 (s, 1H, OH,
D2O exchangeable), 11.3 (s, 1H, CONH, D2O exchangeable).
5.1.1.1. N-(4-Chlorophenyl)-4-(1,3-dioxo-1,3-dihydro-2H-iso-
indol-2-yl)butanamide (1). 2.1 (m, 2H, CH2), 2.4 (t, 2H,
CH2), 3.5 (t, 2H, CH2), 7.42e7.88 (m, 8H, Aryl-H), 9.88 (s,
1H, CONH, D2O exchangeable).
5.1.2.4. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )-
5.1.1.2. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-(3-fluo-
rophenyl)butanamide (3). 2.0 (m, 2H, CH2), 2.34 (t, 2H,
CH2), 3.56 (t, 2H, CH2), 7.01e7.77 (m, 8H, Aryl-H), 9.89
(s, 1H, CONH, D2O exchangeable).
(4-hydroxy-3-methoxyphenyl)methylene]butanoyl
hydrazide
(15). 1.96 (m, 2H, CH2), 2.2 (t, 2H, CH2), 3.58 (t, 2H,
CH2), 3.7 (s, 3H, OCH3), 6.8e7.8 (m, 7H, Aryl-H), 8.1 (s,
1H, Carbimino-H), 9.8 (s, 1H, OH, D2O exchangeable), 11.1
(s, 1H, CONH, D2O exchangeable).
5.1.1.3. N-(2,6-Dimethylphenyl)-4-(1,3-dioxo-1,3-dihydro-2H-
isoindol-2-yl)butanamide (4). 2.1 (m, 2H, CH2), 2.2 (bs, 6H,
2,6-(CH3)2), 2.3 (t, 2H, CH2), 3.5 (t, 2H, CH2), 7.10e7.70
(m, 7H, Aryl-H), 9.9 (s, 1H, CONH, D2O exchangeable).
5.1.2.5. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )-
1-phenylethylidene]butanoyl hydrazide (16). 1.2 (s, 3H, Carbi-
mino-CH3), 1.92 (m, 2H, CH2), 2.1 (t, 2H, CH2), 3.63 (t, 2H,
CH2), 7.4e7.7 (m, 9H, Aryl-H), 10.7 (s, 1H, CONH, D2O
exchangeable).
5.1.1.4. N-(4-Bromo-3-methylphenyl)-4-(1,3-dioxo-1,3-dihy-
dro-2H-isoindol-2-yl)butanamide (6). 2.0 (m, 2H, CH2), 2.3
(s, 3H, CH3), 2.4 (t, 2H, CH2), 3.6 (t, 2H, CH2), 7.20e7.80
(m, 7H, Aryl-H), 10.01 (s, 1H, CONH, D2O exchangeable).
5.1.2.6. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )-
1-(2-hydroxyphenyl)ethylidene]butanoyl hydrazide (18). 1.1
(s, 3H, Carbimino-CH3), 1.92 (m, 2H, CH2), 2.1 (t, 2H,
CH2), 3.63 (t, 2H, CH2), 6.9e7.8 (m, 8H, Aryl-H), 9.8 (s,
1H, OH, D2O exchangeable), 10.9 (s, 1H, CONH, D2O
exchangeable).
5.1.1.5.
4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-(4-
methylphenyl)butanamide (8). 2.1 (m, 2H, CH2), 2.32 (s, 3H,
CH3), 2.4 (t, 2H, CH2), 3.5 (t, 2H, CH2), 7.42e7.88 (m, 8H,
Aryl-H), 9.88 (s, 1H, CONH, D2O exchangeable).
5.1.2.7. N0-[(1E )-1-(3-Aminophenyl)ethylidene]-4-(1,3-dioxo-
1,3-dihydro-2H-isoindol-2-yl)butanoyl hydrazide (20). 0.98
(s, 3H, Carbimino-CH3), 1.92 (m, 2H, CH2), 2.1 (t, 2H,
CH2), 3.6 (t, 2H, CH2), 5.75 (s, 2H, NH2, D2O exchangeable),
6.8e7.8 (m, 8H, Aryl-H), 10.9 (s, 1H, CONH, D2O
exchangeable).
5.1.2. General procedure for the preparation of N-
aryl/alkylidene-4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-
butanoyl hydrazides (11e26)
As mentioned earlier, N-protection of GABA was achieved
by the already reported procedure [19]. Equimolar quantities
of N,N-phthaloyl GABA (0.03 mol) and hydrazine hydrate
(99e100%) (0.03 mol) were condensed in the presence of
DCC (0.03 mol) in dichloromethane, by stirring at ice-cold con-
ditions (0e3 ꢀC) for 6e8 h [24]. Equimolar quantities of N,N-
phthaloyl GABA hydrazide (0.03 mol) and different substituted
aldehydes and ketones (0.03 mol) were refluxed in the presence
of glacial acetic acid (0.06 mol) in ethanol for 6e8 h [21]. The
IR spectra of N-aryl/alkylidene-4-(1,3-dioxo-1,3-dihydro-2H-
isoindol-2-yl)butanoyl hydrazides (11e26) were identical in
5.1.2.8. N0-Cyclohexylidene-4-(1,3-dioxo-1,3-dihydro-2H-iso-
indol-2-yl)butanoyl hydrazide (25). 1.4 (m, 4H, ortho-CH2
of cyclohexyl), 1.77 (m, 6H, cyclohexyl), 1.9 (m, 2H, CH2),
2.2 (t, 2H, CH2), 3.6 (t, 2H, CH2), 7.7e7.8 (m, 4H, Aryl-H),
10.77 (s, 1H, CONH, D2O exchangeable).
5.1.2.9. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(3Z )-
the following aspects: 3020, 1785, 1640, 1610 cmꢂ1 1H
;
NMR (DMSO) d (ppm) spectra of some representative com-
pounds are as follows.
2-oxo-1,2-dihydro-3H-indol-3-ylidene]butanoyl
hydrazide
(26). 1.9 (m, 2H, CH2), 2.19 (t, 2H, CH2), 3.63 (t, 2H,
CH2), 7.3e7.9 (m, 7H, Aryl-H), 10.55 (s, 1H, CONH, D2O ex-
changeable), 11.1 (s, 1H, CONH of isatin, D2O exchangeable).
5.1.2.1. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )
phenylmethylene]butanoyl hydrazide (11). 1.9 (m, 2H, CH2),
2.2 (t, 2H, CH2), 3.5 (t, 2H, CH2), 7.5e7.9 (m, 9H, Aryl-H),
8.2 (s, 1H, Carbimino-H), 11.0 (s, 1H, CONH, D2O
exchangeable).
5.2. Pharmacology
Male albino mice (CF-1 strain, 18e25 g) were used as ex-
perimental animals. All the test compounds were suspended in
0.5% methyl cellulose in the case of MES and scPTZ screens
at NIH and 30% PEG for screening in the picrotoxin and
strychnine-induced seizure models at our lab. The animals
5.1.2.2. 4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N0-[(1E )-
(3-nitrophenyl)methylene]butanoyl hydrazide (12). 1.9 (m,

J.V. Ragavendran et al. / European Journal of Medicinal Chemistry 42 (2007) 146e151
151
were maintained at an ambient temperature of 22 ꢁ 1 ꢀC, in
groups of five per cage under standard laboratory conditions,
receiving standard laboratory chow and water ad libitum. A
12 h:12 h light/dark cycle was maintained throughout the ex-
perimental studies. All the tests have been performed in accor-
dance with the guidelines laid out by the Institutional Animal
Ethics Committee.
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Acknowledgements
[23] P. Yogeeswari, D. Sriram, R. Thirumurugan, J.V. Ragavendran,
K. Sudhan, Roheeth Kumar, J. Stables, J. Med. Chem. 48 (2005)
6202e6211.
One of the authors Mr. J.V. Ragavendran gratefully ac-
knowledges the junior research fellowship (JRF) granted by
the University Grants Commission (UGC), New Delhi, India.
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