Design, synthesis, and anticonvulsant screening of some substituted piperazine and aniline derivatives of 5-phenyloxazolidin- 2,4-diones and 5,5-diphenylimidazolidin-2,4 diones

Article abstract of DOI:10.1007/s00044-011-9805-z

Substituted piperazine and aniline derivatives of oxazolidin-2,4-diones and imidazolidin-2,4-diones were synthesized by N3 alkylation and screened for their anticonvulsant activity by the maximal electroshock (MES) test, and their neurotoxicity was evaluated by the rotarod test. Among all the synthesized derivatives, compounds 4b, 6c, 6d, 10b, 11a, 11b, and 11d were found to exhibit maximum seizure protection in MES test and were devoid of any neurotoxic effects. Furthermore, the functional activity of these compounds were evaluated in vivo for 5-HT_1A receptor affinity by using rectal body temperature and lower lip retraction in rats, while head twitch response in mice was performed for the determination of probable affinity toward HT_2A receptor. The results of these tests demonstrated that compounds 4b, 6c, 6d, 10b, 11a, 11b, and 11d exhibited 5-HT_1A (pre- and postsynaptic) agonist/ antagonist features whereas compounds 11a and 11b exhibited antagonist action for HT_2A receptor. From the in vivo studies it was observed that a majority of aniline derivatives (6c, 6d, 11a, 11b, 11d) were found to be more active as compared to their bulky piperazine congeners (4b, 10b). Thus, the overall reduction in the bulkiness of the derivatives without compromising the lipophilicity is well appreciated for providing insights into the structural requirements necessary for development of new effective molecules having anticonvulsant effect.

Full text of DOI:10.1007/s00044-011-9805-z

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:2807–2822
DOI 10.1007/s00044-011-9805-z
ORIGINAL RESEARCH
Design, synthesis, and anticonvulsant screening of some
substituted piperazine and aniline derivatives of 5-phenyl-
oxazolidin-2,4-diones and 5,5-diphenylimidazolidin-2,4 diones
•
Meenakshi Dhanawat Anupam G. Banerjee
•
S. K. Shrivastava
Received: 16 May 2011 / Accepted: 6 October 2011 / Published online: 25 October 2011
Ó Springer Science+Business Media, LLC 2011
Abstract Substituted piperazine and aniline derivatives
of oxazolidin-2,4-diones and imidazolidin-2,4-diones were
synthesized by N3 alkylation and screened for their anti-
convulsant activity by the maximal electroshock (MES)
test, and their neurotoxicity was evaluated by the rotarod
test. Among all the synthesized derivatives, compounds 4b,
6c, 6d, 10b, 11a, 11b, and 11d were found to exhibit
maximum seizure protection in MES test and were devoid
of any neurotoxic effects. Furthermore, the functional
activity of these compounds were evaluated in vivo for
5-HT1A receptor affinity by using rectal body temperature
and lower lip retraction in rats, while head twitch response
in mice was performed for the determination of probable
affinity toward 5-HT2A receptor. The results of these tests
demonstrated that compounds 4b, 6c, 6d, 10b, 11a, 11b,
and 11d exhibited 5-HT1A (pre- and postsynaptic) agonist/
antagonist features whereas compounds 11a and 11b
exhibited antagonist action for 5-HT2A receptor. From the
in vivo studies it was observed that a majority of aniline
derivatives (6c, 6d, 11a, 11b, 11d) were found to be more
active as compared to their bulky piperazine congeners (4b,
10b). Thus, the overall reduction in the bulkiness of the
derivatives without compromising the lipophilicity is well
appreciated for providing insights into the structural
requirements necessary for development of new effective
molecules having anticonvulsant effect.
Keywords Anticonvulsants ꢀ Heteroaryl ꢀ
Piperazine derivative ꢀ Aniline derivative ꢀ MES ꢀ
Neurotoxicity
Introduction
The term epilepsy is derived from the Greek word epi-
lepsia, meaning ‘‘falling sickness’’. Epilepsy is one of the
most common neurological disorders, affecting around 50
million people worldwide (http://www.who.int/mediacen
tre/factsheets/fs999/en/index.html, Accessed 25 March
2011). In the past decade, several new anticonvulsant drugs
such as felbamate, lamotrigine, gabapentin, tiagabine, to-
piramate have been approved by US-FDA for the treatment
of epilepsy (Pastalos, 1999). However to-date, antiepileptic
drug therapy is marred by a number of limitations (Baulac,
2003) as available drugs are effective only in 60–80% of
epileptic patients. Hence, there is a need for the develop-
ment of newer anticonvulsants with enhanced therapeutic
profile.
Oxazolidinedione and imidazolidinedione are the key
structural element of many biologically active compounds.
Oxazolidine-2,4-diones have been reported to be clinically
evaluated as a hypnotic and antiepileptic agent, e.g., trid-
ione, paradione, dimedione, and malidone which have been
employed for the treatment of epilepsy (Livingston and
Boks, 1955). Apart from this they have also been reported
to possess antimicrobial (Shankarananth et al., 2010) and
antihyperglycemic properties (Dow et al., 1991; Momose
et al., 2002).
M. Dhanawat ꢀ A. G. Banerjee ꢀ S. K. Shrivastava (&)
Department of Pharmaceutics, Institute of Technology,
Banaras Hindu University, Varanasi 221 005, India
e-mail: skshrivastava.phe@itbhu.ac.in
Similarly, imidazolidinedione (glycolylurea), the core
moiety of phenytoin is effective against most type of partial
seizures. A number of 5,5-disubstituted imidazolidinedi-
ones have found use in medicine as hypnotics and for the
M. Dhanawat
e-mail: mdanawat.rs.phe@itbhu.ac.in
123

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Med Chem Res (2012) 21:2807–2822
treatment of chorea (Maryland, 1943). Apart from this,
imidazolidines have been reported to possess a wide array
of pharmacological properties such as antidiabetic, (Cheng
et al., 2010) antitumor, (Rodgers et al., 1977) microbicidal,
(Mulwad et al. 2011; Albuquerque et al., 1999) HIV
protease inhibitors, (Flosi et al., 2006) antiarrhythmic,
(Pekala et al., 2005; Matsukura et al., 1992) antifungal,
(Dolezel et al., 2009) antibacterial and anti-inflammatory
(Menezes et al., 1992).
arylpiperazin-1-yl)-ethyl]-5 phenyl-oxazolidine-2,4-dione
(10a–f); 3-[(p-aniline)-ethyl]-5-phenyl-oxazolidine-2,4-dione
(11a–e) derivatives with an ethyl spacer between imide
nitrogen atom and 4-arylpiperazine or p-aniline derivative
moiety (Schemes 1, 2; Table 1).
Experimental
Serotonin (5-HT) plays a crucial role in many of the
physiological and pathophysiological processes in the
brain. Presently, there has been a growing evidence sug-
gesting the involvement of serotoninergic neurotransmis-
sion in the modulation of a wide variety of experimentally
induced seizures along with enhanced seizure susceptibility
as observed in some genetically prone rats (Salgado-
Commissariat et al., 1996); (Filakovszky et al., 1999);
All the chemicals were purchased from Sigma Aldrich and
solvents from Merck and were used without further puri-
fication. All reactions were monitored by thin-layer chro-
matography (TLC) performed on Merck silica gel 60 F254
aluminum sheets (Merck; Darmstadt, Germany). Spots
were detected by their absorption under UV light
(k = 254 nm) or were visualized with iodine vapors.
The spectroscopic analyses (IR, NMR, and MS) besides
the C, H, N, O analyses were used for structural confirmation
of the synthesized derivatives. Melting points (m. p.) were
determined in open capillary tubes by using STUART
(SMP10, UK) and are uncorrected. The Infra-Red (IR)
spectra were recordrd on a Shimadzu 8300 FT-IR spectro-
photometer using KBr pellets and solid run in solution.
The 1H and 13C NMR spectra were recorded on a Bruker
Avance DPX (300 MHz) spectrometer. Chemical shifts
were reported in parts per million (ppm) units relative to
Tetra Methyl Silane (TMS) which was used as an internal
standard. Splitting patterns are as follows: s, singlet; d,
doublet; t, triplet; m, multiplet. A mass spectrum was
obtained on a Hewlett Packard model GCD-1800A Elec-
tron Impact Mass Spectrometer (EIMS) at 70 eV ionizing
beam using direct insertion probe. Elemental analyses (C,
H, N, O) of the compounds were performed using Exeter
CE-440 Elemental Analyzer instrument and results
obtained were within 0.4% of the theoretical values.
(Graf et al., 2004). Modulation of 5-HT1A/2A receptors
plays an important aspect in mediating the anticonvulsant
action through these receptors.
It is well reported that aryl-piperazines exhibits good
affinity with 5-HT1A/2A receptors. This specificity depends
critically on the nature of the specific heterocyclic nuclei
(A), on the aromatic substitution (B) and on the length
(n) of the poly-methylene chain usually (n = 2) (Fig. 1). In
addition to piperazine, several aniline derivatives were also
developed as anticonvulsants in this study. The piperazine
ring is replaced by a linear secondary amine followed by an
aryl nucleus. The purpose of this replacement was to
evaluate the effect of reduction of the bulkiness of the
pharmacophoric part on the anticonvulsant activity. Thus
the final structure of the synthesized derivatives constituted
of the oxazolidin-2,4-diones and disubstituted hydantoins
designed so as to include the common pharmacophoric
features such as specific heterocyclic nuclei (A), a poly-
methylene chain (with the length kept constant as n = 2)
and various piperazine and aniline derivatives forming the
aromatic substitution (B) (Fig. 1).
Chemistry
Thus, in the course of developing new potential anti-
convulsant agents mediating their action through 5-HT1A
/
General procedure for the preparation of 3-[(4-
arylpiperazin-1-yl)-ethyl]-5,5-diphenyl-imidazolidine-
2,4-dione (4a–f)
5-HT2A receptor we focused our attention on the synthesis
of a new series of 3-[(4-arylpiperazin-1-yl)-ethyl]-5,
5-diphenyl-imidazolidine-2,4-dione (4a–f); 3-[(p-aniline)-
ethyl]-5,5-diphenyl imidazolidine-2,4-dione (6a–e); 3-[(4-
Step 1: Procedure for the synthesis of 5,5-
diphenylhydantoin (1)
O
Synthesis of 5,5-diphenylhydantoin 1 was carried out using
Biltz synthesis (1908) reported by Schmidt (2008) and
Dunnavant and James (1956).
A = Non-pharmacophoric part
B
n
N
O
A
B = Pharmacophoric
N
H
5,5-Diphenyl-imidazolidine-2,4-dione (1) Melting point:
298–300°C; yield: quantitative; IR (KBr, vmax cm-1): 3270
Fig. 1 Proposed pharmacophore
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Med Chem Res (2012) 21:2807–2822
2809
Scheme 1 Synthetic
procedures (a) KOH,
NH2CONH2, (b) KOH, DMF,
1-bromo-2-chloro ethane/RT,
1–2 h, (c) DMSO, RT/reflux,
2–3 h
O
O
Ph
HN
O
HN
Ph
Ph
Ph
b
N
a
NH
Cl
O
O
O
2
1
5a-e(Substituted
Aniline Derivatives)
3a-f (Substituted
Piperazine
Derivatives)
c
c
O
Ph
Ph
O
H
Ph
Ph
N
N
R
NH
N
R
N
N
HN
O
O
4a-f
6a-e
Scheme 2 Synthetic
O
procedures (a) dry ethanol,
conc. H2SO4, reflux, (b) urea,
NaH, NaOEt, ice bath—3.5 h
reflux, (c) KOH, DMSO,
1-bromo-2-chloro ethane/RT,
1–2 h, (d) DMSO, RT/Reflux,
2–3 h
O
O
OH
O
HN
a
b
OH
O
OH
O
8
7
O
O
3a-f (Substituted
Piperazine
Derivatives)
Cl
O
N
N
N
R
N
O
c
O
O
9
c
10 a-f
5a-e(Substituted
Aniline Derivatives)
O
O
O
N
N
R
H
11 a-e
1
(N–H), 3000 (C=CH, aromatic), 1633 (C=O); H NMR
(CDCl3, 300 MHz): d 10.7 (s, 1H, N3), d 8.9 (s, 1H, N1),
7.2 (m, 10H, 2Ph); 13C NMR (CDCl3): 170.7, 160, 143,
129, 128.4, 126, 75.5; MS (m/z): 253.27 (M ? 1); Anal.
calcd. For C15H12N2O2 C, 71.42; H, 4.79; N, 11.10; O,
12.68 Found C, 71.68; H, 4.75; N, 11.08; O, 12.65.
reaction was monitored by TLC (EtOAc: Hexane 1:4) The
reaction mixture was subsequently washed with ethyl
acetate (100 ml), water (3 9 30 ml), brine (2 9 50 ml),
dried over (Na2SO4), and evaporated to dryness. The crude
product 2 obtained, was purified by column chroma-
tography.
Step 2: Procedure for the synthesis of 3-(2-chloro-ethyl)-
5,5-diphenyl-imidazolidine-2,4-dione (2)
3-(2-Chloro-ethyl)-5,5-diphenyl-imidazolidine-2,4-dione
(2) Melting point: 267–269°C; yield: 76% IR (KBr,
vmax cm-1): 3306 (N–H), 1650 (C=O), 1437 (aromatic
1
To a solution of the 5,5-diphenylhydantoin (4.75 mmol) in
DMSO (dimethyl sulphoxide), KOH (10 ml; 14.4 mmol)
was added (14.3 mmol), along with 1-bromo-2-chloroeth-
ane (11.9 mmol). The resulting reaction mixture was stir-
red at room temperature for 1 h. The completion of
C=C); H NMR (CDCl3, 300 MHz) d 7.3–7.2 (m, 10H,
2Ph), 6.1 (s, 1H, NH), 3.9 (t, 2H, CH2Cl), 3.8-3.7 (t, 2H,
NCH2); 13C NMR (CDCl3): 174.5, 156.8, 137.5, 128.9,
128.5, 125.4, 67.9, 40.0, 31.9; MS (m/z): 315.77 (M ? 1);
Anal. Calc for C17H15ClN2O2: C, 64.87; H, 4.80; Cl, 11.26;
123

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Med Chem Res (2012) 21:2807–2822
Table 1 Structures and physicochemical data of compounds
O
O
O
Ph
Ph
Ph
Ph
H
N
R
N
N
N
HN
N
R
NH
O
4a-f
6a-e
O
O
O
O
N
N
R
N
N
N
R
O
H
O
10a-f
11a-e
Yield
(%)
Mol. Wt
(calc.)
Compd no.
4a
R
Formulae
OH
F
C27H28N4O3
55
60
57
456.54
458.53
474.98
4b
4c
C27H27FN4O2
C27H27ClN4O2
Cl
NO2
CH3
4d
C27H27N5O4
62
485.53
4e
4f
C28H30N4O2
C26H27N5O2
C23H21N3O3
58
67
65
454.56
441.52
387.43
N
OH
6a
6b
6c
Cl
F
C23H20ClN3O2
C23H20FN3O2
55
70
405.88
389.42
6d
OCH3
C24H23N3O3
65
401.46
123

Med Chem Res (2012) 21:2807–2822
2811
Table 1 continued
Yield
(%)
Mol. Wt
(calc.)
Compd no.
R
Formulae
CH3
OH
6e
C24H23N3O2
55
65
385.46
381.43
10a
C21H23N3O4
F
10b
10c
C21H22FN3O3
C21H22ClN3O3
67
60
383.42
399.87
Cl
10d
C21H22N4O5
55
410.42
NO2
CH3
10e
10f
11a
C22H25N3O3
C20H22N4O3
C17H16N2O4
67
56
62
379.45
366.41
312.32
N
OH
11b
11c
11d
11e
Cl
C17H15ClN2O3
C17H15FN2O3
C18H18N2O4
C18H18N2O3
60
58
65
55
330.77
314.31
326.35
310.35
F
OCH3
CH3
N, 8.90; O, 10.17; Found: C, 65.12; H, 4.75; N, 8.1; O,
10.14.
reaction was monitored by TLC (MeOH: DCM 1:9). The
solvent was evaporated and the residue was treated with water
(50 ml) and the precipitate was filtered off, washed with
water. The crude product obtained was purified by column
chromatography to afford the products (4a–f).
Step 3: General procedure for the synthesis of compound
(4a–f)
3-(2-Chloro-ethyl)-5,5-diphenylhydantoin
2
appropriate 4-phenylpiperazine derivatives (3a–f) (0.001
(0.005 mol),
3-{2-[4-(4-Hydroxy-phenyl)-piperazin-1-yl]-ethyl}-5,5-diphenyl-
imidazolidine-2,4-dione (4a) Semisolid mass; yield:
55%; IR (solid run in solution, vmax cm-1): 3444 (OH),
mol) and DMSO were refluxed for 4 h. The completion of
123

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Med Chem Res (2012) 21:2807–2822
1
3294 (N–H), 2821 (C–H), 1666 (C=O); H NMR (CDCl3,
300 MHz): d 7.3–7.1 (m, 10H, 2Ph), 6.9–6.8 (m, 4H, Ph),
5.2 (s, 1H, N–H, phenytoin), 5.1 (s, 1H, OH) 3.2 (t, 2H,
NCH2–NCH2), 3.1 (m, 4H, piperazine), 2.6 (t, 2H, NCH2–
NCH2), 2.5 (m, 4H, piperazine); 13C NMR (CDCl3): 168.9,
161.2, 143, 129, 128, 126, 116.4, 114.7, 73.3, 58.6, 52.6,
51.8, 43.2; MS (m/z): 457.54 (M ? 1); Anal. calcd for
C27H28N4O3 C, 71.03; H, 6.18; N, 12.27; O, 10.51 Found:
C, 71.24; H, 6.20; N, 12.30; O, 10.46.
(C–H), 1666 (C=O), 1315 (C–N); 1H NMR (CDCl3,
300 MHz): 7.6–7.4 (m, 10H, 2Ph), 6.9–6.4 (m, 4H, Ph), 5.3
(s, 1H, N–H, phenytoin), 3.9 (t, 2H, NCH2–NCH2), 3.7 (m,
4H, piperazine), 2.6 (t, 2H, NCH2–NCH2), 2.4 (m, 4H,
piperazine), 2.2 (s, 3H, CH3); 13C NMR (CDCl3): 168.9,
161.2, 143, 129, 128.4, 126, 116.4, 114.7, 73.3, 58.6, 52.6,
51.8, 43.2, 38.7; MS (m/z): 455.56 (M ? 1); Anal. calcd.
for C27H27N5O4 C, 73.98; H, 6.65; N, 12.33; O, 7.04 cal-
culated: C, 74.27; H, 6.67; N, 12.37; O, 7.06.
5,5-Diphenyl-3-[2-(4-pyridin-2-yl-piperazin-1-yl)-ethyl]-im-
idazolidine-2,4-dione (4f) Melting point: 264–266°C;
yield: 67%; IR (KBr, vmax cm-1): 3290, 1599 (N–H), 2831
(C–H), 1315 (C–N); 1H NMR (CDCl3, 300 MHz): d 8.2 (d,
1H, H-1, pyridyl), 7.5–7.3 (m, 10H, 2Ph), 6.6–6.5 (m, 3H,
H-2, H-3, H-4, pyridyl), 5.3 (s, 1H, N–H, phenytoin), 3.1 (t,
2H, NCH2–NCH2), 3.0 (m, 4H, piperazine), 2.6 (t, 2H,
NCH2–NCH2) 2.3 (m, 4H, piperazine); 13C NMR (CDCl3):
168.9, 161.2, 161.1, 148.9, 143, 138, 129, 128, 126, 113,
108, 73.3, 57.9, 55.1, 51.8, 43.2 (1C); MS (m/z): 442.52
(M ? 1); Anal. calcd. for C26H27N5O2; C, 70.73; H, 6.16;
N, 15.86; O, 7.25 Found: C, 70.65; H, 6.15; N, 15.83; O,
7.23%.
3-{2-[4-(4-Fluoro-phenyl)-piperazin-1-yl]-ethyl}-5,5-diphenyl-
imidazolidine-2,4-dione (4b) Melting point: 263–265°C;
yield: 60%; IR (KBr, vmax cm-1): 3306 (N–H), 2825
(C–H), 1685 (C=O); 1H NMR (CDCl3, 300 MHz): d
7.3–7.2 (m, 10H, 2Ph), 6.9–6.8 (m, 4H, Ph), 5.2 (s, 1H,
N–H, phenytoin), 3.9 (t, 2H, NCH2–NCH2), 3.8 (m, 4H,
piperazine), 3.1 (t, 2H, NCH2–NCH2), 2.7 (m, 4H, piper-
azine); 13C NMR (CDCl3): 168.9, 161.2, 143, 129, 128,
126, 116.4, 114.7, 73.3, 58.6, 52.6, 51.8, 43.2; MS (m/z):
459.43 (M ? 1); Anal.calcd. for C27H27FN4O2: C, 70.72;
H, 5.94; N, 12.22; O, 6.98; Found: C, 71.89; H, 5.93; N,
12.26; O, 6.97.
3-{2-[4-(4-Chloro-phenyl)-piperazin-1-yl]-ethyl}-5,5-diphenyl-
imidazolidine-2,4-dione (4c) Melting point: 263-265°C;
yield: 57% IR (KBr, vmax cm-1): 3286 (N–H), 2827 (C–H),
1657 (C=O); 1H NMR (CDCl3, 300 MHz): d 7.3–7.2
(m, 10H, 2Ph), 6.9–6.8 (m, 4H, Ph), 5.3 (s, 1H, N–H,
phenytoin), 3.9 (t, 2H, NCH2–NCH2), 3.7 (m, 4H, pipera-
zine), 3.1 (t, 2H, NCH2–NCH2), 3.0 (s, 4H, piperazine);
13C NMR (CDCl3): 168.9, 161.2, 143, 129, 128, 126,
116.4, 114.7, 73.3, 58.6, 52.6, 51.8, 43.2; MS (m/z): 475.98
(M ? 1); Anal. calcd. for C27H27ClN4O2; C, 68.27; H,
5.73; Cl, 7.46; N, 11.80; O, 6.74; Found: C, 68.54; H, 5.75;
Cl, 7.48; N, 11.84; O, 6.76.
General procedure for the preparation of 3-[(p-aniline)-
ethyl]-5,5-diphenyl imidazolidine-2,4-dione (6)
Steps 1 and 2 are same as described under the preparation
of 3-[(4-arylpiperazin-1-yl)-ethyl]-5,5-diphenyl-imidazoli-
dine-2,4-dione (4).
Step 3: General procedure for the synthesis of compound
(6a–e)
3-(2-Chloro-ethyl)-5,5-diphenylhydantoin 2 (0.005 mol)
along with various para substituted anilines (5a–
f) (0.001 mol) and DMSO were refluxed for appropriate
time till the completion of reaction monitored by TLC
(EtOAc:Hexane 2:1). The solvent was evaporated and the
residue was treated with water (50 ml). The precipitate was
filtered off, washed with water and the crude product
obtained was purified by column chromatography to afford
the products (6a–e).
3-{2-[4-(4-Nitro-phenyl)-piperazin-1-yl]-ethyl}-5,5-diphenyl-
imidazolidine-2,4-dione (4d) Melting point 265-267°C;
yield 62%; IR (KBr, vmax cm-1): 3315 (N–H), 2848 (C–H),
1
1667 (C=O); H NMR (CDCl3, 300 MHz): d 8.2–8.1 (d,
2H, Ph), 7.4–6.9 (m, 10H, 2Ph), 6.7–6.6 (s, 2H, Ph) 6.2 (s,
1H, N–H, phenytoin), 3.9 (t, 2H, NCH2–NCH2), 3.8 (m,
4H, piperazine) 3.4 (t, 2H, NCH2–NCH2,), 3.0 (m, 4H,
piperazine); 13C NMR (CDCl3): 166.9, 160.2, 141, 125,
122, 121, 116.4, 114.7, 70.3, 54.6, 50.6, 50.8, 42.2; MS
(m/z): 486.53(M ? 1): Anal. calcd. for C27H27N5O4; C,
66.79; H, 5.61; N, 14.42; O, 13.18 Found: C, 67.05; H,
5.63, N, 14.47; O, 13.23.
3-[2-(4-Hydroxy-phenylamino)-ethyl]-5,5-diphenyl-imida-
zolidine-2,4-dione (6a) Semisolid mass; yield: 65%; IR
(solid run in solution, vmax cm-1): 3456 (OH), 3323 (N–H),
1
2918 (C–H), 1655 (C=O), 1315 (C–N); H NMR (CDCl3,
300 MHz): d 7.4–7.1 (m, 10H, 2Ph), 7.3 (m, 4H, 1Ph), 6.1
(s, 1H, N–H, phenytoin), 5.1 (s 1H, OH), 3.9 (s, 1H, N–H,
aniline), 2.9 (t, 2H, NCH2), 2.6 (t, 2H, NCH2); 13C NMR
(CDCl3): 168.9, 161.2, 145.7, 143, 136.1, 129, 128.4, 126,
116.5, 113.7, 73.3, 49.8, 45; MS (m/z): 388.43 (M ? 1):
5,5-Diphenyl-3-[2-(4-p-tolyl-piperazin-1-yl)-ethyl]-imidaz-
olidine-2,4-dione (4e) Semisolid mass; yield: 58%; IR
(solid run in solution, vmax cm-1): 3387 (N–H), 2918
123

Med Chem Res (2012) 21:2807–2822
2813
General procedure for the preparation of 3-[(4-
arylpiperazin-1-yl)-ethyl]-5 phenyl-oxazolidine-2,4-
dione (10)
Anal.calcd. for C23H21N3O3; C, 71.30; H, 5.46; N, 10.85;
O, 12.39; Found: C, 71.25; H, 5.48; N, 10.83; O, 12.41.
3-[2-(4-Chloro-phenylamino)-ethyl]-5,5-diphenyl-imidazo-
lidine-2,4-dione (6b) Melting point: 265–267°C; yield:
55%; IR (KBr, vmax cm-1): 3380 (N–H), 2818 (C–H), 1645
(C=O), 1300 (C–N); 1H NMR (CDCl3, 300 MHz): d
7.4–7.1 (m, 10H, 2Ph), 6.6 (m, 4H, 1Ph), 5.3 (s, 1H, N–H,
phenytoin), 4.2 (s, 1H, N–H, aniline), 3.9 (t, 2H, NCH2),
3.7 (t, 2H, NCH2); 13C NMR (CDCl3): 168.9, 161.2, 143,
141.6, 129.7, 129, 128, 126, 122, 113, 73.3, 49.8, 45; MS
(m/z): 406.88 (M ? 1); Anal.calcd. for C23H20ClN3O2; C,
68.06; H, 4.97; N, 10.35; O, 7.88 Found: C, 68.22; H, 4.95;
N, 10.39; O, 7.85.
Step 1: Procedure for the synthesis of ethyl mandelate (7)
A solution of DL-mandelic acid (hydroxyphenyl acetic
acid) (2.63 mmol) in ethanol (150 ml) containing concen-
trated sulfuric acid (0.25 ml) was refluxed for 1.5 h. After
cooling, the solution was diluted with ice-water, neutral-
ized by saturated aqueous sodium carbonate and the mix-
ture was extracted with ether. The combined ethereal
extracts were dried and evaporated to yield the final com-
pound 7.
3-[2-(4-Fluoro-phenylamino)-ethyl]-5,5-diphenyl-imidazo-
lidine-2,4-dione (6c) Melting point: 269–271°C; yield:
70%; IR (KBr, vmax cm-1): 3367 (N–H), 2900 (C–H), 1673
(C=O), 1313 (C–N); 1H NMR (CDCl3, 300 MHz): d
7.4–7.3 (m, 10H, 2Ph), 6.8–6.5 (m, 4H, 1Ph), 6.3 (s, 1H,
N–H, phenytoin), 4.1 (s, 1H, N–H, aniline), 3.2 (t, 2H,
NCH2), 3.1 (t, 2H, NCH2); 13C NMR (CDCl3): 168.9,
161.2, 150.5, 143, 139.1, 129, 128.4, 126, 116, 113, 73.3,
49.8, 45MS (m/z): 390.42 (M ? 1); Anal. calcd. for
C23H20FN3O2; C, 70.94; H, 5.18; N, 10.79; O, 8.22; Found:
C, 71.10; H, 5.17; N, 10.76; O, 8.19.
Hydroxy-phenyl-acetic acid ethyl ester (7) Melting point:
93–95°C; yield: quantitative; IR (KBr, vmax cm-1): 2983,
1454, 732 (–CH2–CH3), 1720 (Ester C=O); 1H NMR
(CDCl3, 300 MHz): d 7.30 (5H, m, Ph), 5.17 (1H, s,
PhCH), 4.28 and 4.20 (2d, 2H, CH2Me), 3.65 (1 H, br s,
OH) and 1.22 (t, 3H, Me); 13C NMR (CDCl3): 173.6,
138.4, 128.5, 128.3, 126.5 (Ph-C3, C5), 72.9 (CH), 62.1
(CH2) 14.0; MS (m/z): 181.20(M ? 1); Anal.calcd. for
C10H12O3; C, 66.65; H, 6.71; O, 26.64; Found: C, 66.70; H,
6.73; O, 26.59.
3-[2-(4-Methoxy-phenylamino)-ethyl]-5,5-diphenyl-imida-
zolidine-2,4-dione (6d) Melting point: 268–270°C; yield:
65%; IR (KBr, vmax cm-1): 3207 (N–H), 2907 (C–H), 1666
(C=O), 1298 (C–N); 1H NMR (CDCl3, 300 MHz): d
7.3–7.2 (m, 10H, 2Ph), 6.7–6.6 (m, 4H, 1Ph), 6.1 (s, 1H,
N–H, phenytoin), 5.9 (d, 1H, N–H, aniline), 3.7 (m, 3H,
OCH3), 3.9 (t, 2H, NCH2), 3.8 (t, 2H, NCH2); 13C NMR
(CDCl3): 168.9, 161.2, 150.4, 143, 135.8, 129, 128.4, 126,
114.9, 113.3, 73.3, 56, 49.8, 45; MS (m/z): 402.46
(M ? 1); Anal.calcd. for C24H23N3O3; C, 71.80; H, 5.77;
N, 10.47; O, 11.96 Found; C, 72.01; H, 5.79; N, 10.50; O,
11.94.
Step 2: Procedure for the synthesis of 5-phenyl-oxazolidin-
2,4-dione (8)
To a solution of ethoxide (prepared by dissolving 0.6 mol
of sodium in absolute ethanol) urea was added in one
portion. To this stirred solution, an ice-cold solution of
ester 7 (0.6 mol) in absolute ethanol was added gradually
over a period of 10 min at 0°C. The pasty mass obtained
was allowed to attain room temperature by allowing it to
stand for 20 min and then refluxed for 2 h. Excess of sol-
vent was removed by distillation and the resulting slurry
was stored at 5°C for 2 h. The disodium salt thus obtained
was washed with small portions of cold ethanol to afford
the final product 8.
5,5-Diphenyl-3-(2-p-tolylamino-ethyl)-imidazolidine-2,4-dione
(6e) Melting point: 266–268°C; yield: 55%; IR (KBr,
vmax cm-1): 3284 (N–H), 2989 (C–H), 1639 (C=O), 1301
1
5-Phenyl-oxazolidine-2,4-dione (8) Melting point: 123–
125°C; yield: quantitative; IR (KBr, vmax cm-1): 3373
(NH), 1606 (C=O); 1H NMR (CDCl3, 300 MHz): d 10.2 (s,
1H, N–H), 7.4-7.2 (m, 5H, 1Ph), 5.2 (s, 1H, methine); 13C
NMR (CDCl3): 170.7, 157.3, 135.9, 129.8, 129, 127.4,
92.4; MS (m/z): 178.16(M ? 1); Anal. calcd. for C9H7NO3
C, 61.02; H, 3.98; N, 7.91; O, 27.09 F Found: C, 61.12; H,
3.97; N, 7.88; O, 26.95.
(C–N); H NMR (CDCl3, 300 MHz): d 7.3–7.2 (m, 10H,
2Ph), 6.7–6.6 (m, 4H, 1Ph), 6.246 (s, 1H, N–H, phenytoin),
4.2 (d, 1H, N–H, aniline), 3.9 (t, 2H, NCH2), 3.7 (t, 2H,
NCH2), 2.6 (s, 3H, CH3); 13C NMR (CDCl3): 168.9, 161.2,
143, 140, 130, 129, 128.4, 126, 112.5, 73.3, 49.8, 45, 20.9;
MS (m/z): 386.46 (M ? 1); Anal.calcd. for C24H23N3O2;
C, 74.78; H, 6.01; N, 10.90; O, 8.30 Found: C, 75.02; H,
6.02; N, 10.89; O, 8.28.
123

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Med Chem Res (2012) 21:2807–2822
1
Step 3: Procedure for synthesis of (9)
(C=O); H NMR (CDCl3, 300 MHz): d 7.2 (m, 5H, 1Ph),
6.7–6.6 (m, 4H, Ph), 5.8 (s, 1H, methine), 3.6 (t, 2H,
NCH2–NCH2), 3.4 (m, 4H, piperazine), 3.1 (t, 2H, NCH2–
NCH2), 2.6 (m, 4H, piperazine); 13C NMR (CDCl3): 168.9,
155.9, 151.6, 140.1, 135.9, 129.8, 129.0, 129.8, 127.4,
116.4, 114.7, 90.2, 57.9, 55.1, 52.3, 42.3; MS (m/z):
384.42(M ? 1) Anal.calcd. for C21H22FN3O3; C, 65.78; H,
5.78; N, 10.96; O, 12.52 Found: C, 66.04; H, 5.80; N,
10.98; O, 12.57.
A mixture of 5-phenyl-oxazolidin-2,4-dione (1 mmol),
K2CO3 (1.3 mmol), alkyl halide (1.1 mmol) and DMF
(Dimethylformamide) were stirred at room temperature for
1.5–2 h. The completion of reaction was monitored by
TLC (100% EtOAc). After completion, the reaction mix-
ture was poured into ice-water. The crystallized product 9
thus obtained was filtered and washed with water.
3-(2-Chloro-ethyl)-5-phenyl-oxazolidine-2,4-dione (9)
Melting point: 127-129°C; yield: 84%; IR (KBr, vmax
cm-1) 2924 (C–H), 2854, 1456 (-CH2-), 1647 (C = O),
3-{2-[4-(4-Chloro-phenyl)-piperazin-1-yl]-ethyl}-5-phenyl-oxa-
zolidine-2,4-dione (10c) Melting point: 152–154°C; yield:
1
60%; IR (KBr, vmax cm-1): 2827 (C–H), 1658 (C=O); H
1
1732 (Ar C–C) 759 (C–Cl); H NMR (CDCl3, 300 MHz):
NMR (CDCl3, 300 MHz): d 7.2 (m, 5H, 1Ph), 7.0-6.5 (m,
4H, Ph), 6.0 (1H, methine), 3.4 (t, 2H, NCH2–NCH2), 3.1
(m, 4H, piperazine), 2.8 (t, 2H, NCH2–NCH2), 2.6 (m, 4H,
piperazine); 13C NMR (CDCl3): 168.9, 155.9, 142.6, 135.9,
129.8, 129.0, 127.4, 123.3, 114.5, 90.2, 57.9, 55.1, 52.3,
42.3; MS (m/z): 400.87(M ? 1); Anal. calcd. for
C21H22ClN3O3; C, 63.08; H, 5.55; N, 10.51; O, 12.00
Found: C, 63.15; H, 5.52; N, 10.52; O, 12.02.
d 7.4-7.2 (m, 5H, 1Ph), 5.2 (s, 1H, methine), 4.2 (d, 2H,
CH2Cl), 3.7-3.4 (s, 2H, NCH2); 13C NMR (CDCl3): 168.9,
155.5, 135.9, 129.8, 129, 127, 90, 45.4, 43.6; MS (m/z):
240.34(M ? 1); Anal.calcd. for C11H10ClNO3; C, 55.13;
H, 4.21; N, 5.84; O, 20.03 Found: C, 55.10; H, 4.20; N,
5.82; O, 20.06.
Step 4: General procedure for the synthesis of (10a–f)
3-{2-[4-(4-Nitro-phenyl)-piperazin-1-yl]-ethyl}-5-phenyl-oxa-
zolidine-2,4-dione (10d) Melting point: 149–151°C; yield:
55%; IR (KBr, vmax cm-1): 2848 (C–H), 1632 (C=O), 1599
(NO2), 1377 (NO2); 1H NMR (CDCl3, 300 MHz): d 8.0 (s,
2H, Ph–NO2), 7.2 (m, 5H, 1Ph), 6.8-6.6 (m, 2H, Ph), 6.7
(1H, methine), 3.6 (t, 2H, NCH2–NCH2), 3.4 (m, 4H,
piperazine), 2.8 (t, 2H, NCH2–NCH2), 2.7 (m, 4H, piper-
azine); 13C NMR (CDCl3):168.9, 155.9, 142.6, 135.9,
129.8, 129.0, 127.4, 123.3, 114.5, 90.2, 57.9, 55.1, 52.3,
42.3; MS (m/z): (M ? 1) 411.42 (M ? 1); Anal. calcd. for
C21H22N4O5; C, 61.45; H, 5.40; N, 13.65; O, 19.49 Found:
C, 61.35; H, 5.42, N, 13.62; O, 19.40.
To a solution of N3 alkylated 5-phenyl-oxazolidine-2,
4-dione 9 (3.32 mmol) in DMF, different piperazine
derivatives (3a–f) (8.06 mmol) were added. The reaction
mixture was allowed to stir at room temperature. TLC
(DCM: MeOH, 5%) was performed to confirm the com-
pletion of reaction. After complete removal of the solvent,
the reaction mixture was poured into water (20 ml) and the
aqueous phase extracted with ethyl acetate (3 9 20 ml).
The combined ethyl acetate layer was dried over anhydrous
sodium sulpfate (Na2SO4). The solvent was removed under
vacuum to give the crude compounds. The crude products
were purified by column chromatography to afford the final
products (10a–f).
5-Phenyl-3-[2-(4-p-tolyl-piperazin-1-yl)-ethyl]-oxazolidine-
2,4-dione (10e) Melting point: 150–152°C; yield: 67%;
1
IR (KBr, vmax cm-1): 2918 (C–H), 1666 (C=O); H NMR
3-{2-[4-(4-Hydroxy-phenyl)-piperazin-1-yl]-ethyl}-5-phenyl-
oxazolidine-2,4-dione (10a) Melting point: 145–147°C;
yield: 65%; IR (KBr, vmax cm-1): 3252 (OH), 2821 (C–H),
(CDCl3, 300 MHz): d 7.2 (m, 5H, 1Ph), 6.8–6.4 (m, 4H,
Ph), 6.2 (1H, methine), 3.6 (t, 2H, NCH2–NCH2), 3.2 (m,
4H, piperazine), 3.0 (t, 2H, NCH2–NCH2), 2.9 (m, 4H,
piperazine) 1.25 (s, 3H, –CH3); 13C NMR (CDCl3): 168.9,
155.9, 142.6, 135.9, 129.8, 129.0, 127.4, 123.3, 114.5,
90.2, 57.9, 55.1, 52.3, 42.3; MS (m/z): 380.45(M ? 1);
Anal.calcd. for C22H25N3O3; C, 69.64; H, 6.64; N, 11.07;
O, 12.65 Found: C, 70.01; H, 6.66; N, 11.11; O, 12.60.
1
1642 (C=O); H NMR (CDCl3, 300 MHz): d 7.2 (m, 5H,
1Ph), 6.5–6.4 (m, 4H, Ph), 6.2 (1H, methine), 5.1 (s, 1H,
–OH) 3.8 (t, 2H, NCH2–NCH2), 3.7 (m, 4H, piperazine),
3.5 (t, 2H, NCH2–NCH2), 3.4 (m, 4H, piperazine); 13C
NMR (CDCl3): 168.9, 155.9, 142.6, 135.9, 129.8, 129.0,
127.4, 123.3, 114.5, 90.2, 57.9, 55.1, 52.3, 42.3; MS (m/z):
382.43(M ? 1); Anal. calcd. for C21H23N3O4; C, 66.13; H,
6.08; N, 11.02; O, 16.78 found: C, 66.39; H, 6.10; N,
11.06; O, 16.84.
5-Phenyl-3-[2-(4-pyridin-2-yl-piperazin-1-yl)-ethyl]-oxazol-
idine-2,4-dione (10f) Melting point: 147–149°C; yield:
1
56%; IR (KBr, vmax cm-1): 2831 (C–H), 1683 (C=O); H
NMR (CDCl3, 300 MHz): d 8.1 (d, 1H, H-1, pyridyl), 7.1 (m,
5H, 1Ph), 6.6–6.5 (m, 3H, H-2, H-3, H-4, pyridyl), 6.4 (1H,
methine), 3.0 (t, 2H, NCH2–NCH2), 2.9 (m, 4H, piperazine),
3-{2-[4-(4-Fluoro-phenyl)-piperazin-1-yl]-ethyl}-5-phenyl-
oxazolidine-2,4-dione (10b) Melting point: 146–148°C;
yield: 67%; IR (KBr, vmax cm-1): 2825 (C–H), 1662
123

Med Chem Res (2012) 21:2807–2822
2815
2.8 (t, 2H, NCH2–NCH2), 2.6 (m, 4H, piperazine); 13C NMR
(CDCl3): 168.9, 155.5, 135.9, 129.8, 129.0, 127.4, 161.1,
148.9, 138.0, 113.0, 108.9, 90.2, 57.9, 55.1, 52.2, 42.3; MS
(m/z): 367.41 M ? 1); Anal. calcd. for C20H22N4O3; C,
65.56; H, 6.05; N, 15.29; O, 13.10 Found: C, 65.82; H, 6.07;
N, 15.35; O, 13.15.
(C=O), 1498 (–CH2–); 1H NMR (CDCl3, 300 MHz): d 7.8-
7.3 (m, 5H, 1Ph), 7.2-7.0 (m, 4H, 1Ph), 6.1 (1H, methine),
4.2 (s, 1H, N–H, aniline), 3.6 (t, 2H, NCH2–NCH2), 2.9 (t,
2H, NCH2–NCH2); 13C NMR (CDCl3): 168.9, 161.1,
155.5, 150.5, 139.1, 135.9, 129.8, 129.0, 127.4, 116.3,
113.9, 50.2, 44.1; MS (m/z): 315.31 (M ? 1); Anal. calcd.
for C17H15FN2O3; C, 64.96; H, 4.81; N, 8.91; O, 15.27
Found: C, 65.90; H, 4.82; N, 8.90; O, 15.25.
General procedure for the preparation of 3-[(p-aniline)-
ethyl]-5-phenyl-oxazolidine-2,4-dione (11)
3-[2-(4-Methoxy-phenylamino)-ethyl]-5-phenyl-oxazolidine-
2,4-dione (11d) Melting point: 133–135°C; yield: 65%;
IR (KBr, vmax cm-1): 3308 (N–H), 2790 (C–H), 2835
Steps 1, 2 and 3 are same as described under the prepara-
tion of 3-[(4-arylpiperazin-1-yl)-ethyl]-5-phenyl-oxazoli-
dine-2,4-dione (10)
1
(–OCH3), 1679 (C=O); H NMR (CDCl3, 300 MHz): d
7.4–7.3 (m, 5H, 1Ph), 7.2–7.1 (m, 4H, 1Ph), 6.1 (1H,
methine), 4.9 (s, 1H, N–H, aniline), 4.2 (s, 3H, –OCH3), 3.6
(t, 2H, NCH2–NCH2), 2.6 (t, 2H, NCH2–NCH2); 13C NMR
(CDCl3): 168.9, 155.5, 150.4, 135.9, 135.8, 129.8, 129.0,
127.4, 114.9, 113.3, 90.2, 56.0, 50.2, 44.1; MS (m/z):
327.35 (M ? 1); Anal. calcd. for C18H18N2O4; Actual C,
66.25; H, 5.56; N, 8.58; O, 19.61 Found: C, 66.45; H, 5.55;
N, 8.60; O, 19.57.
Step 4: General procedure for the synthesis of (11a–e)
To a solution of aniline derivatives (5a–f) (8.06 mmol) in
DMSO (3.32 mmol) of N3 alkylated oxazolidin-2,4-dione
was added. After 2–4 h, depending upon completion of
reaction which was monitored by TLC (MeOH:DCM
0.5:9.5), the reaction was terminated followed by evapo-
ration of solvent. Compounds obtained were purified by
column chromatography to afford the final compounds
(11a–e).
5-Phenyl-3-(2-p-tolylamino-ethyl)-oxazolidine-2,4-dione (11e) Melt-
ing point: 140–142°C; yield: 55%; IR (KBr, vmax cm-1):
3308 (N–H), 2790 (C–H), 1654 (C=O), H NMR (CDCl3,
1
3-[2-(4-Hydroxy-phenylamino)-ethyl]-5-phenyl-oxazolidine-
2,4-dione (11a) Melting point: 128–130°C; yield: 62%;
IR (KBr, vmax cm-1): 3486 (–OH), 3308 (N–H), 2790 (C–
300 MHz): d 7.4–7.2 (m, 5H, 1Ph), 6.8-6.7 (m, 4H, 1Ph),
6.2 (1H, methine), 4.2 (s, 1H, N–H, aniline), 3.1-3.0 (2t,
4H, NCH2–NCH2), 1.9 (m, 3H, –CH3); 13C NMR (CDCl3):
168.9, 155.5, 140.5, 135.9, 129.8, 130.0, 129.0, 127.4,
126.1, 112.2, 90.2, 56.0, 50.2, 44.1, 20.9; MS (m/z): 311.35
(M ? 1); Anal. calcd. for C18H18N2O3; C, 69.66; H, 5.85;
N, 9.03; O, 15.47 Found: C, 69.55; H, 5.83; N, 9.01; O,
15.45.
1
H), 1649 (C=O), 1257 (C–O, Str), 1312 (C–N); H NMR
(CDCl3, 300 MHz): d 7.1–7.0 (m, 5H, 1Ph), 6.5–6.3 (m,
4H, 1Ph), 6.1 (1H, methine), 5.2 (s, 1H, –OH) 4.1 (s, 1H,
N–H, aniline), 2.9–2.6 (2t, 4H, NCH2–NCH2); 13C NMR
(CDCl3): 168.9, 155.5, 145.7, 136.1, 135.9, 129.8, 129.0,
127.4, 116.5, 113.7, 90.2, 56.0, 50.2, 44.1; MS (m/z):
312.32 (M ? 1); Anal. calcd. for C17H16N2O4; Actual C,
65.38; H, 5.16; N, 8.97; O, 20.49 Found: C, 65.34; H, 5.18,
N, 9.00; O, 20.57.
Pharmacology
Pharmacological experiments were carried out on Albino
Swiss mice (20–25 g) and Wistar rats (200–250 g) (pro-
cured from Central Animal Breeding House, Institute of
Medical Sciences, Banaras Hindu University) were used.
The animals were housed in plastic cages at an ambient
temperature of 25 2°C and 45–55% relative humidity
and maintained on a 12:12 h (7:00 a.m. to 7:00 p.m.) light–
dark cycle with free access to standard pellet diet and water
ad libitum. Animals were allowed to acclimatize to their
environment for at least 7 days before experimentation.
The animals were randomly distributed into different
groups of six animals each. Each animal was weighed,
caged separately, and had identification marks cryptically
encoding the dose level and group. All experimental pro-
tocols were approved by Institutional Animal Ethical
Committee (IAEC) [Approval No. Dean/10-11/155]
3-[2-(4-Chloro-phenylamino)-ethyl]-5-phenyl-oxazolidine-
2,4-dione (11b) Melting point: 130–132°C; yield: 60%;
IR (KBr, vmax cm-1): 3308 (N–H), 2790 (C–H), 1639
1
(C=O); H NMR (CDCl3, 300 MHz): d 7.4–7.3 (m, 5H,
1Ph), 7.2 (m, 4H, 1Ph), 6.3 (1H, methine), 4.0 (s, 1H, N–H,
aniline), 3.6-3.2 (2t, 4H, NCH2–NCH2); 13C NMR
(CDCl3): 168.9, 161.1, 155.5, 150.5, 139.1, 135.9, 129.8,
129.0, 127.4, 116.3, 113.9, 50.2, 44.1; MS (m/z): 331.77
(M ? 1); Anal. calcd. for C17H15ClN2O3; Actual C, 61.73;
H, 4.57; N, 8.47; O, 14.51 Found: C, 61.65; H, 4.58; N,
8.45; O, 14.49.
3-[2-(4-Fluoro-phenylamino)-ethyl]-5-phenyl-oxazolidine-
2,4-dione (11c) Melting point: 132–134°C; yield: 58%;
IR (KBr, vmax cm-1): 3290 (N–H), 2831 (C–H), 1663
123

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Med Chem Res (2012) 21:2807–2822
Institute of Medical Sciences, Banaras Hindu University.
Experiments were conducted as per the Guidelines issued
for the Care and Use of Laboratory Animals as promul-
gated by the National Institutes of Health (NIH).
for at least 1 min in each of the three trials (Krall et al.,
1978; Stables and Kupferberg, 1997a, b).
In vivo 5-HT1A and 5-HT2A bioassay
Initially, all the synthesized derivatives were subjected
to evaluation for preliminary anticonvulsant screening in
mice. Seizure assay was carried out according to the Phase
I tests of the antiepileptic drug development (ADD) pro-
tocol developed by the National Institute of Neurological
and Communicative Disorders and Stroke (NINCDS)
(Krall et al., 1978; Stables and Kupferberg, 1997a, b;
Kupferberg and Stables, 1997).
N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-py-
ridinyl)-cyclohexane carboxamide trihydrochloride (WAY
100635), 8-Hydroxy-2-(di-n-propylamino) tetralin hydro-
bromide (8-OH-DPAT), and ( )-1-(2,5-dimethoxy-4-iodo-
phenyl)-2-aminopropane ( )-(DOI) in aqueous solutions
were used for the abovementioned studies.
The investigated compounds (4b, 6c, 6d, 10b, 11a, 11b,
11d) were suspended in 1% aqueous solution of Tween 80.
The suspensions were neutralized using a few drops of
0.1 M NaOH. 8-OH-DPAT and WAY 100635 were
injected subcutaneously (sc). The compounds 4b, 6c, 6d,
10b, 11a, 11b, 11d and ( )-DOI were administered
intraperitoneally (ip) in a volume of 2 ml/kg for rats and
10 ml/kg for mice. The data obtained were analyzed by
one-way analysis of variance followed by Dunnett’s test.
(Berendsen et al., 1989; Jurczyk et al., 2004; Dursun and
Handley, 1996; Schreiber et al., 1995).
Phase I involved the intraperitonial administration of the
compounds in mice as a suspension in 0.5% methylcellu-
lose. Phase I is a qualitative assay involving a small
number of mice (1–4) at dose levels of 30, 100, and
300 mg/kg. Compounds found active in Phase I evaluation
were advanced to Phase VIa of anticonvulsant drug
development protocol wherein the compounds were orally
administered into rats at a dose of 30 mg/kg. The anti-
convulsant screening of synthesized derivatives were per-
formed using the maximal electroshock (MES) test
whereas their neurotoxicity liability was evaluated using
the rotarod method.
Rectal body temperature of rats
In vivo anticonvulsant screening
Effects of the tested compounds given alone on the rectal
body temperature of rats were recorded 30, 60, 90, and
120 min after administration. In a separate study, the effect
of WAY 100635 (0.1 mg/kg) on hypothermia induced by
the tested compounds was evaluated. WAY 100635 was
administered 15 min before the tested compounds and the
rectal body temperature was recorded 30 and 60 min after
their injection. The results were expressed as a change in
body temperature (Dt) with respect to basal body temper-
ature, as measured at the beginning of the experiment.
Maximal electroshock (MES) test
In this test, seizures were elicited with a 60 Hz alternating
current of 50 mA intensity in mice and rats. The current
was applied through corneal electrodes for 0.2 s duration.
Abolition of the hind-leg tonic-extensor component of the
seizure indicated protection against the spread of MES
induced seizures. The synthesized compounds were sus-
pended in 0.5% methylcellulose and were administered in a
standard volume of 0.5 ml/20 g body weight at 30, 100,
300 mg kg-1. Control animals received 0.5% suspension
of methylcellulose and phenytoin was used as a reference
drug (30 mg kg-1). From this test, one can readily prese-
lect compounds that are effective in suppression of tonic–
clonic seizures and to a certain extent, of partial seizures
with or without secondary generalization in humans
(Rogawski, 2006; Ucar et al. 1998; Stables and Kupfer-
berg, 1997a, b).
Lower lip retraction (LLR)
The lower lip retraction (LLR) was assessed as per the
method described by Berendsen et al. (1989). The rats were
placed individually in cages and were scored for LLR for
three times (15, 30, and 45 min) after the administration of
the tested compounds or 8-OH-DPAT. The scoring of the
results were done as follows (0 = lower incisors not visi-
ble, 0.5 = partly visible, 1 = clearly visible).
The total maximum score amounted to three per rat. In a
separate experiment, the effect of the investigated com-
pounds or WAY 100635 on LLR induced by 8-OH-DPAT
(1 mg/kg) was tested. The compounds to be investigated or
WAY 100635 were administered 45 min and 15 min,
respectively, prior to 8-OH-DPAT and the animals were
scored 15, 30, and 45 min after 8-OH-DPAT adminis-
tration.
Rotarod performance test
Rotarod test was carried to measure the minimal motor
impairment in mice and rats. The animals were trained to
balance on the knurled rotating rod (3.2 cm diameter) that
rotates at 6 rpm. Neurotoxicity was indicated by the
inability of the animal to maintain equilibrium on the rod
123

Med Chem Res (2012) 21:2807–2822
2817
Head twitch method
Table 2 Evaluation of all synthesized compounds in MES and
rotarod test after intraperitoneal injection (30, 100, 300 mg/kg) in
mice (Phase I)
In order to acclimatize the mice to the experimental envi-
ronment, each animal was transferred to a cage, 30 min
before treatment. Head twitches were induced in mice by
( )-DOI (2.5 mg/kg). Immediately after the treatment, the
head twitches (rapid right and left movements of the head
with little or no involvement of the trunk) were counted for
20 min (Darmani et al., 1990). The investigated com-
pounds were administered 60 min before ( )-DOI. Their
5-HT2A antagonistic activity was compared to ketanserin
Intraperitoneal injection in mice
MES (h)a
0.5
NT (h)b
4
0.5
4
4a
–
300
30
–
–
300
–
4b
–
–
4c
–
–
–
4d
–
300
300
–
–
300
300
–
(ID50 = 0.14 mg/kg),
a
well-known5-HT2A receptor
4e
–
100
–
antagonist (Byrtus et al., 2005).
4f
–
6a
–
–
–
–
6b
–
–
–
–
In silico ADME studies
6c
100
300
–
30
100
–
–
–
6d
–
–
The QikProp 3.1 (Schrodinger; LLC, USA) program was
used to predict the ADME properties of the synthesized
analogs. Ligands were build using Maestro 8.5 build panel
6e
–
–
10a
10b
10c
10d
10e
10f
11a
11b
11c
11d
11e
Phenytoin
a
–
–
–
–
–
100
–
–
–
¨
and prepared by Ligprep 2.2 version v22208 (Schrodinger,
–
–
–
LLC, USA) application that used OPLS 2005 force field.
The best-fit ligands were neutralized before being used by
QikProp. The program was processed in normal mode, and
predicted properties for the best-fit molecules, consisting of
principal descriptors and physiochemical properties with
analyses of the log P (octanol/water), % human oral
absorption, Lipinski’s rule of five violation, CNS activity.
–
300
–
–
300
–
–
–
–
–
–
–
100
100
–
30
30
300
100
–
–
–
–
–
–
300
–
–
–
–
–
–
30
30
100
100
Results and discussion
MES test (number of animals protected/number of animals tested)
b
Chemistry
Neurotoxicity assessed by rotarod (number of animals exhibiting
toxicity/number of animals tested)
In this study we report the synthesis of a new series of
3-[(4-arylpiperazin-1-yl)-ethyl]-5,5-diphenyl-imidazoli-
dine-2,4-dione (4a–f); 3-[(p-aniline)-ethyl]-5,5-diphenyl
imidazolidine-2,4-dione (6a–e); 3-[(4-arylpiperazin-1-yl)-
ethyl]-5 phenyl-oxazolidine-2,4-dione (10a–f); 3-[(p-ani-
line)-ethyl]-5-phenyl-oxazolidine-2,4-dione (11a–e) deriv-
atives with an ethyl spacer between imide nitrogen atom
and 4-arylpiperazine or p-aniline derivative moiety.
The synthetic strategies adopted to obtain the target
compounds are depicted in Schemes 1 and 2, respectively.
The 1H-NMR spectra of the investigated compounds
revealed characteristic chemical shifts agreed with their
proposed structures. All compounds were isolated in their
pure form and molecular formulae were established on the
basis of elemental (C, H, N, O) analyses.
Table 3 Evaluation of compounds in MES and rotarod test after oral
administration (30 mg/kg) in rats (Phase VI a)
Oral drug administration in rat
MES (h)a
0.5
NT (h)b
0.5
4
4
4b
1/6
3/6
2/6
2/6
3/6
3/6
0/6
6/6
3/6
4/6
2/6
2/6
3/6
4/6
2/6
5/6
0/6
0/6
0/6
0/6
0/6
0/6
0/6
–
0/6
0/6
0/6
0/6
0/6
0/6
0/6
–
6c
6d
10b
11a
11b
11d
Phenytoin
a
5,5-diphenylhydantoin 1 was selectively alkylated at N3
position with 1-bromo-2-chloro-ethane to afford the
2-chloroethyl derivative 2. The IR spectra of both 1 and 2
showed the presence of N–H peaks at 3270 and
MES test (number of animals protected/number of animals tested)
b
Neurotoxicity assessed by rotarod (number of animals exhibiting
toxicity/number of animals tested)
123

2818
Med Chem Res (2012) 21:2807–2822
Table 4 Effect of the investigated compounds and WAY 100635 on the rectal body temperature in rats
Treatment
Dose mg/kg
Dt SEM
30 min
60 min
0.0 0.1
90 min
120 min
Vehicle
–
10
20
10
20
10
20
10
20
10
20
10
20
10
20
0.1
-0.1 0.1
-0.9 0.2
-1.7 0.3
-0.5 0.1
-2.5 0.1
-0.5 0.1
-1.2 0.3
-0.6 0.2
-1.5 0.3
-0.4 0.1
-1.0 0.1
-0.2 0.1
-1.2 0.2
-0.5 0.1
-1.1 0.1
0.2 0.1
-0.2 0.1
-0.7 0.2
-1.6 0.2
-0.9 0.3
-2.9 0.1
-0.8 0.1
-1.8 0.2
-0.5 0.2
-1.4 0.1
-0.7 0.1
-1.6 0.1
-0.7 0.2
-1.5 0.1
-0.8 0.3
-1.5 0.2
0.1 0.1
0.0 0.1
-0.8 0.2
-1.7 0.2
-0.7 0.2
-1.5 0.1
-0.6 0.1
-1.3 0.1
-0.5 0.3
-1.4 0.1
-0.6 0.1
-1.1 0.1
-0.5 0.1
-1.3 0.1
-0.7 0.2
-1.3 0.1
0.2 0.1
4b
-0.7 0.1
-1.6 0.3
-0.7 0.1
-2.7 0.2
-0.6 0.2
-1.5 0.2
-0.4 0.1
-1.4 0.1
-0.6 0.2
-1.2 0.1
-0.5 0.1
-1.3 0.3
-0.8 0.1
-1.5 0.2
0.2 0.1
6c
6d
10b
11a
11b
11d
WAY100635
The investigated compounds (ip) and WAY 100635 (sc) were administered 30 min before the test. The absolute mean initial body temperatures
were within a range of 36.3 0.5 C. P \ 0.001 versus vehicle
Table 5 Induction of lower lip retraction (LLR) in rats by the
investigated compounds and WAY 100635 (A) and their effect on the
8-OH-DPAT (B)
Table 6 Effect of compounds 11a, 11b, and ketanserin on the
)-DOI* induced head twitch response in mice (*(( )-1-(2,5-
dimethoxy-4-iodophenyl)-2-aminopropane)
(
Treatment
Dose mg/kg
Mean SEM LLR score
Treatment
ID50 (mg/kg, ip)a
A
B
11a
11 (7.9–15.4)
8 (6.1–11.5)
11b
Vehicle
–
0.1 0.1
1.0 0.1
1.8 0.3
1.5 0.2
2.3 0.1
1.0 0.2
1.4 0.1
0.1 0.1
0.9 0.3
0.2 0.1
0.5 0.2
0.1 0.1
0.3 0.2
0.1 0.4
0.8 0.2
0.1 0.1
2.8 0.2
2.2 0.2
2.5 0.2
2.8 0.2
NT
Ketanserine
0.12 (0.07–0.20)
4b
10
20
10
20
10
20
10
20
10
20
10
20
10
20
0.1
a
ID50—the dose inhibiting the head twitches in mice by 50%; con-
fidence limit (90%) given in parenthesis. The investigated compounds
were administrated ip 60 min before ( )-DOI (2.5 mg/kg, ip)
6c
6d
2.3 0.1
2.5 0.1
0.4 0.1
0.7 0.2
0.8 0.1
0.8 0.1
0.4 0.2
0.6 0.3
0.8 0.1
0.9 0.2
0.3 0.2
10b
Table 7 Functional in vivo 5-HT1A/2A receptor activities of the
investigated compounds
11a
Compound
5HT1A activity
Presynaptic
5HT2A activity
Postsynaptic
11b
4b
Agonist
Agonist
Agonist
Agonist
Agonist
Agonist
Agonist
Agonist
NA
11d
6c
Agonist
NA
6d
Agonist
NA
WAY 100635
10b
11a
11b
11d
Antagonist
Antagonist
Antagonist
Antagonist
NA
Antagonist
Antagonist
NA
The investigated compounds (ip) and WAY 100635 (sc) were
administrated 15 min before the test (A), or 45 min before 8-OH-
DPAT (1 mg/kg, sc) (B) p \ 0.01 versus vehicle (A) or versus
vehicle ? 8-OH-DPAT (B) NT-not tested
123

Med Chem Res (2012) 21:2807–2822
2819
¨
Table 8 ADME screening by QikProp 3.1 (Schrodinger; LLC, USA)
Comp Ligand
no.
CNS FOSA
FISA
Q Plog Q Plog Q Plog Q Plog % Human oral Lipinski’s
rule of five
#Stars #rtvFG
no
P o/w
HERG
BB
Khsa
absorption
4a
S1Lig1
S1Lig2
S1Lig3
S1Lig4
S1Lig5
S1Lig6
S1Lig7
S1Lig8
S1Lig9
S1Lig10
S1Lig11
S2Lig1
S2Lig2
S2Lig3
S2Lig4
S2Lig5
S2Lig6
S2Lig7
S2Lig8
S2Lig9
S2Lig10
S2Lig11
1
1
189.95
190
127.57
3.3
-6.668 -0.669
0.394
79.529
94.405
95.91
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
1
1
0
2
1
2
2
1
2
2
1
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4b
72.847 4.254
72.855 4.512
-6.674
-6.704
0.105
0.156
0.576
0.65
4c
1
189.98
176.95
279.58
193.71
59.59
4d
-2
1
173.57
3.111
-6.316 -1.116
-6.729 -0.038
-6.892 -0.125
-5.126 -1.053
-5.755 -0.409
-5.715 -0.457
-5.743 -0.65
-5.757 -0.593
0.415
0.691
0.405
0.09
70.393
95.555
89.424
88.045
4e
73.644 4.322
82.376 3.68
4f
1
6a
-2
0
136.1
2.975
6b
55.971
55.965
148.77
144.19
201
86.807 4.324
86.797 4.069
86.941 3.933
86.984 4.139
0.411 100
0.34 100
6c
0
6d
0
0.313 100
0.452 100
6e
0
10a
10b
10c
10d
10e
10f
11a
11b
11c
11d
11e
0
147.17
88.14
2.42
3.14
3.36
2.11
3.18
2.44
2.35
3.52
3.24
3.07
3.33
-6.77
-6.96
-6.82
-6.89
-6.82
-6.86
-5.81
-5.87
-5.81
-5.85
-5.87
-0.75
0
0.19
0.1
76.87
0
205.3
91.12
91.64
67.64
90.58
83.96
85.48
0
201.03
201.03
289.21
204.28
76.17
92.49
-0.02
-1.24
-0.16
-0.28
-1.24
-0.49
-0.54
-0.73
-0.68
0.18
-0.05
0.22
-0.11
0.01
0.26
0.19
0.15
0.3
0
190.79
92.5
0
0
106.14
157.62
102.94
102.94
102.94
102.96
0
0
76.16
100
0
76.16
100
100
100
0
168.95
164.36
0
3306 cm-1, respectively. The subsequent condensation of
2 with the various different piperazine and aniline deriva-
tives was carried out by N-alkylation affording products
4a–f and 6a–e, respectively. The IR spectrum of 4a–f,
6a–e exhibited N–H peaks at (3387–3207 cm-1), CH2 peak
at (2818–2918 cm-1), and C=O peak at (1639–1645 cm-1).
1H-NMR spectrum of 4a–f, 6a–e showed aromatic peaks
from 7.4 to 6.9 ppm followed by signals for piperazine
protons between 3.8–3.1 ppm and 3.0–2.4 ppm (4a–f) and at
5.9–3.9 ppm for aniline N–H protons of (6a–e) confirming
the formation of the desired products.
(C–H), 2854 cm-1 1456 cm-1 (–CH2–), 1647 cm-1
,
(C=O), 1732 cm-1 (Ar C–C) 759 cm-1 (C–Cl). The sub-
sequent condensation of intermediate 9 with various
piperazine and aniline derivatives afforded products
10a–f and 11a–f, respectively. The IR spectrum of 10a–f,
11a–e exhibited C–H and C=O peaks at 2821–2918 cm-1
and 1632–1683 cm-1, respectively, whereas in 11a–e N–H
1
peaks were observed at (3308–3390 cm-1). The H-NMR
spectrum of 10a–f and 11a–e shows aromatic peaks at
7.2–7.1 and 7.8–7.0 ppm, followed by the presence of
piperazine protons at 3.7–2.9 and 3.4–2.6 ppm (10a–f) and
4.0–4.9 ppm for aniline N–H protons (11a–e).
Similarly DL-mandelic acid was used for the synthesis
of ethyl mandelate 7. IR spectra of ethyl mandelate 7
shows the absence of COOH group in the IR spectra and
presence of an ester linkage (1720 cm-1) which was sub-
The series of synthesized derivatives were characterized
by physical and spectral analyses. A wide range of both
para-substituted piperazine and aniline derivatives con-
sisting of both electron donating as well as electron with-
drawing groups were employed for the reaction with equal
ease.
1
sequently confirmed by H-NMR showing the disappear-
ance of acidic proton along with appearance of –CH2–CH3
protons. Condensation of 7 with urea in the presence of
sodium ethoxide yielded 5-phenyl-oxazolidine-2,4-dione 8
exhibiting N–H peaks at (3373 cm-1), and C=O peaks at
(1606 cm-1), respectively. Intermediate 8 was further
selectively alkylated at N3 position with 1-bromo-2-chlo-
roethane resulting in the formation of 9 which was con-
firmed by disappearance of N3 protons and presence of
peaks for N–CH2–CH2 protons at 4.2 ppm (d, 2H, CH2Cl),
3.7-3.4 ppm (s, 2H, N–CH2) and IR peaks at 2924 cm-1
Pharmacology
In vivo animal studies
The choice of appropriate animal models for the initial in
vivo testing of potential anticonvulsant compounds is one
of the most important steps in the successful search for new
123

2820
Med Chem Res (2012) 21:2807–2822
Table 9 Details of descriptors (Schrodinger; LLC, USA)
S. Descriptor
no
Description
Recommended
range
1. CNS
Predictive central nervous activity
-2 (inactive) to ?2
(active)
2. FOSA
Hydrophobic component of the SASA (saturated carbon and attached hydrogen)
Hydrophilic components of SASA (SASA on N, O, and H on heteroatoms)
Predicted octanol/water coefficient
0.0–750.0
7.0–330.0
-2.0–6.5
\-5
3. FISA
4. QPlog Po/w
5. QPlog HERG
6. QPlog BB
7. QPlogKhsa
Predicted IC50 value for blockage of HERG K? channels
Predicted brain/blood partition coefficient
-3.0–1.2
-1.5–1.5
Prediction of human serum albumin
8. % Human oral
absorption
It predicts human oral absorption on 0 to 100% scale. The prediction is based on a quantitative [80% is
multiple linear regression model. This property usually correlates well with human oral-
absorption.
high \ 25% is
poor
9. Lipinski’s rule
of five
Lipinski’s rules of five are: mol_MW \ 500, QPlogPo/w \ 5, donorHB B 5, accptHB B 10.
Compounds that satisfy these rules are considered druglike. (The ‘‘five’’ refers to the limits,
which are multiples of 5
Maximum is 4
10. #stars
Number of property or descriptor values that fall outside the 95% range of similar values for
known drugs. A large number of stars suggest that a molecule is less drug-like than molecules
with few stars. The following are some of properties and descriptors are included in the
determination of #stars: Molecular weight, dipole, QPlogPw, QPlogPo/w, QlogS, solvent
accessible surface area (SASA) etc.
0–5
11. #rtvFG
This particular descriptor indicates the number of reactive functional groups. The presence of these 0–2
groups can lead to decomposition, reactivity, or toxicity problems in vivo.
antiepileptic drugs. Among the various chemo-convulsants
and physical stimuli used to induce experimental seizures,
MES is recognized as a valid and reliable means of
studying seizure mechanisms in the development of anti-
convulsant drugs. Rotarod performance test is used to
ascertain the impairment of motor performance, ataxia, loss
of skeletal muscular strength and acute neurotoxicity pro-
duced by drugs in preclinical studies.
C in the pharmacophore (Fig. 1), a majority of aniline
derivatives (6c, 6d, 11a, 11b, 11d) were found to be active
than the piperazine ones (4b, 10b). Amongst all the eval-
uated compounds in Phase VIa, the chloro derivative 11b
and fluoro derivative 6c of aniline were found to be highly
active in comparison to others.
The anticonvulsant action of these molecules was found
to be comparable to that of phenytoin, which was used as a
standard anticonvulsant drug. Overall, the aniline deriva-
tives were found to be more active as compared to their
piperazine congeners against MES (Tables 2, 3).
After the initial assessment for anti-MES activity in
Phase I, compounds 4b, 6c, 6d, 10b, 11a, 11b, 11d were
found to be active against epileptic seizures (Table 2) and
were devoid of any neurotoxicity. Preliminary results from
Phase I rotarod test demonstrated that compounds 4c, 4f,
6a, 6b, 6e, 10a, 10c, 10e, 10f, 11a, and 11e though did not
exibit any visible signs of neurotoxicity at the maximum
administered dose of 300 mg/kg, (Table 2) but were unable
to elicit any protection against the MES assay. As a result
compounds 4b, 6c, 6d, 10b, 11a, 11b, 11d were advanced
to phase VIa of anticonvulsant drug development protocol.
The results of the phase VIa studies are shown in Table 3
For the synthesized series of compounds, it was
observed that the anticonvulsant activity depends mainly
on the length of alkyl spacer between imide nitrogen atom
(here kept constant at n = 2, most active), 4-arylpiperazine
and aniline moiety, as well as on mode of substitution (all
para substituted) of the latter and the type of substituents
(electro positive and electro negative). With respect to part
In vivo receptor binding studies
The compounds found active in MES (4b, 6c, 6d, 10b, 11a,
11b, 11d) without any neurotoxic effects were further
taken up for in vivo receptor binding studies (Tables 4, 5,
6, 7). All the above-mentioned compounds tested, like
8-OH-DPAT, induced hypothermia in mice. Thus, the
results obtained from the hypothermia model are an
indicative that 4b, 6c, 6d, 10b, 11a, 11b and 11d behave
like presynaptic 5-HT1A receptor agonists.
Postsynaptic 5-HT1A affinity was assessed by LLR test.
Like 8-OH-DPAT, compounds 4b, 6c, and 6d evoked LLR
in rats, whereas 10b, 11a, 11b, and 11d like WAY100635,
inhibited LLR induced by 8-OH-DPAT (Table 5). The
above results demonstrated that 4b, 6c, and 6d exhibit
123

Med Chem Res (2012) 21:2807–2822
2821
features of post synaptic 5-HT1A receptor agonist, while
10b, 11a, 11b, and 11d behave like antagonists of these
receptors.
decomposition, reactivity or toxicity related problems in
vivo (Tables 8, 9).
To estimate the affinity toward 5-HT2A receptor, head
twitch method was used. Like ketanserin, a reference
5-HT2A receptor antagonist, compounds 11a and 11b
inhibited the head twitches induced by ( )-DOI, a 5-HT2A
receptor agonist, in mice (Table 6). In comparison to 11a
and 11b all other tested compounds elicited very less
affinity for the 5-HT2A receptor and were assigned as non
actives (NA) (Table 7). Hence, compounds 11a and 11b
may be classified as 5-HT2A receptor antagonists.
Conclusion
In conclusion, a new series of substituted piperazine and
aniline derivatives of 5-phenyl oxazolidin-2,4-diones and
5,5-diphenylimidazolidin-2,4 diones which were synthe-
sized by selective N3 alkylation can be graded as potential
ligands of 5-HT1A receptors. Thus from the in vivo animal
as well as receptor studies, it is evident that the aniline
derivatives of phenytoin and oxazolidine exhibit more
promising action than the more bulky piperazine deriva-
tives. This reduction in the overall bulkiness of the phar-
macophore without compromising the lipophilicity which
will be of further help for these molecules in crossing the
blood brain barrier so as to reach the target receptors for
eliciting the anticonvulsant effects.
From the results obtained by in vivo receptor studies, it
is evident that the tested compounds are characterized by
diverse activity at 5-HT1A receptors. Thus, we can finally
conclude that the compounds 4b, 6c, 6d showed charac-
teristics of pre- and post-synaptic 5HT1A receptor agonists;
compounds 10b, 11a, 11b, 11d exhibited characteristics of
5-HT1A agonist at both pre- and post-synaptic sites.
Moreover, compounds 11a and 11b exhibited properties of
potential 5-HT2A receptor antagonists (Table 7).
At this stage, we can conclude that reduction in bulki-
ness has a positive impact on the anticonvulsant activity of
the compounds. Moreover, compounds showing affinity
toward 5-HT1A/2A receptors can be further quantified (in
vitro) by radio ligand binding assays. Thus, this study helps
to provide a useful insight into the structural requirements
necessary for carrying out rationally based pharmacophoric
manipulations in order to obtain promising compounds
with anticonvulsant effects.
In silico ADME studies
One of the main goals in drug discovery is the identifica-
tion of innovative small molecular scaffolds exhibiting
high binding affinity and selectivity for the target together
with a reasonable absorption, distribution, metabolism and
excretion (ADME) profile, lead and/or drug likeness. Such
chemical entities are likely to be able to enter higher phases
of the drug development process. This has resulted in a
paradigm shift in identifying the drug likeness properties of
lead molecules early in the drug discovery process. Thus,
in vitro approaches are now widely used to investigate the
ADME properties of new chemical entities and, more
recently, computational modeling has been investigated as
a tool to optimize selection of the most suitable candidates
for drug development (Sengupta et al., 2007).
Acknowledgments The authors gratefully acknowledge the finan-
cial assistance given by University Grants Commission (UGC), New
Delhi for the grant of senior research fellowship to Ms. Meenakshi
Dhanawat.
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