Synthesis, anticonvulsant activity and molecular properties prediction of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4- dihydropyridine-3,5-dicarboxylates

Article abstract of DOI:10.1016/j.ejmech.2013.12.001

The synthesis and anticonvulsant properties of new N-diethylmalonyl derivatives of nifedipine and other isosteric analogues (7a-7n) were described. Anticonvulsant screening was performed by subcutaneous pentylenetetrazole (scPTZ) and maximal electroshock (MES) induced seizures tests. Majority of the compounds were effective in scPTZ and MES screens. Compound 7k showed good activity displaying maximum protection, which may be due to the presence of styryl moiety at position 4 of 1,4-dihydropyridine nucleus and the methyl groups of diester functionality. Compounds 7a-7d, 7g, 7i and 7k obeyed the Lipinski's "rule of five" and have drug-likeness. Based on computational prediction of molecular and pharmacokinetic properties, it was found that the compounds have good oral absorption.

Full text of DOI:10.1016/j.ejmech.2013.12.001

European Journal of Medicinal Chemistry 73 (2014) 97e104
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, anticonvulsant activity and molecular properties prediction
of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-
1,4-dihydropyridine-3,5-dicarboxylates
*
G. Prasanthi , K.V.S.R.G. Prasad, K. Bharathi
Institute of Pharmaceutical Technology, Sri Padmavathi Mahila Visvavidyalayam, Tirupathi 517502, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and anticonvulsant properties of new N-diethylmalonyl derivatives of nifedipine and other
isosteric analogues (7ae7n) were described. Anticonvulsant screening was performed by subcutaneous
pentylenetetrazole (scPTZ) and maximal electroshock (MES) induced seizures tests. Majority of the
compounds were effective in scPTZ and MES screens. Compound 7k showed good activity displaying
maximum protection, which may be due to the presence of styryl moiety at position 4 of 1,4-
dihydropyridine nucleus and the methyl groups of diester functionality. Compounds 7ae7d, 7g, 7i and
7k obeyed the Lipinski’s “rule of five” and have drug-likeness. Based on computational prediction of
molecular and pharmacokinetic properties, it was found that the compounds have good oral absorption.
Ó 2013 Elsevier Masson SAS. All rights reserved.
Received 25 January 2013
Received in revised form
22 November 2013
Accepted 3 December 2013
Available online 12 December 2013
Keywords:
Diethylmalonyl
Pyridine-3,5-dicarboxylates
Lipinski’s “rule of five”
Maximal electroshock method
Subcutaneous pentylenetetrazole method
1. Introduction
method [5,6]. 1-Malonyl-1,4-dihydropyridine derivatives (1 and 2)
(Fig. 1) were reported as novel carrier systems for the site specific
Epilepsy is a group of serious disorders of the brain character-
ized by recurrent spontaneous seizures. The efficacy of many
antiepileptic drugs (AEDs) is limited by the dose related toxicities
and diverse array of adverse side effects, due to the limited access
through the bloodebrain barrier, which is a major impediment for
the treatment of central nervous system (CNS) diseases [1,2]. The
limitations for AEDs are also due to the drugs acting as substrates
for P-glycoprotein (Pgp), which leads to multi drug resistance [3].
Various attempts have been made to overcome the limited access of
drugs to the brain and to reduce the systemic side effects that are
common with general treatments. The biologically active com-
pounds linked to a lipoidal dihydropyridine carrier, which can
easily penetrate the bloodebrain barrier were reported as novel
chemical delivery systems for the site specific and sustained de-
livery of drugs to the brain [4].
and sustained drug delivery to the brain which exhibited moderate
antidepressant activity comparable to imipramine [7,8].
In the present work, diethylmalonyl ester derivatives of nifedi-
pine bearing different substituted aryl moieties attached to posi-
tion 4 of 1,4-dihydropyridine(1,4-DHP) were synthesized. It was
planned to study the effect of phenyl ring and the nature of the
spacer moiety consisting of 1e2 carbon atoms connected to the 1,4-
DHP ring system. The compounds were evaluated for anticonvul-
sant activity by maximal electroshock and pentylenetetrazole
induced methods and also predicted for drug-likeness. The topo-
logical polar surface area, in vitro oral bioavailability and bloode
brain barrier permeability were calculated.
2. Results
Nifedipine is a 1,4-dihydropyridine derivative, possessing cal-
cium channel blocking and antihypertensive activities. It has also
been reported to prolong the latent period and reduce the duration
of tonic extensor phase of maximal electroshock induced seizure
2.1. Chemistry
The designed diethylmalonyl ester derivatives, 7ae7n were
successfully synthesized as illustrated in Scheme 1. The conden-
sation of commercially available aldehydes (5ae5e), alkylacetoa-
cetates (3 or 4) and ammonia solution in methanol provided
compounds 6ae6n in good yields. Compounds 6ae6n were
refluxed with diethyl-2-bromomalonate in absolute ethanol for
* Corresponding author. Tel.: þ91 9959008935.
E-mail addresses: prasanthi.gummalla@yahoo.com, deepa3108@gmail.com
(G. Prasanthi), bharathikoganti@yahoo.co.in (K. Bharathi).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.12.001

98
G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
CONHNH2
CONHN
C
H
NO2
Cl
H3COOC
N
COOCH3
N
HC
COOH
HC
COOH
H3C
N
H
CH3
COOCH2CH3
COOCH2CH3
1
6e
2
Fig. 1. Lead structures for target compounds 7ae7n.
15 h in 1:2 stoichiometric ratios affording compounds, 7ae7n in
good yields. The purity of the compounds was assessed by thin
layer chromatography. The detailed synthesis, physical data
(Table 1), spectral and analytical data are listed in the Experimental
protocol section.
2.2. Anticonvulsant activity
Acute toxicity studies were performed and all the compounds
were found to be safe upto 100 mg/kg body weight as no deaths were
observed. Hence, the safe dose was fixed as 10 mg/kg body weight.
Ar
O
ROOC
H3C
COOR
CH3
Ar-CHO
+
a
O
N
H
5a-5g
RO
6a-6n
(3) R=CH3
(4) R=CH2CH3
b
Ar
ROOC
COOR
H3C
O
N
CH3
O
H3CH2C
CH2CH3
O
O
7a-7n
Ar
R
Ar
R
7a
7b
7c
7d
7e
7f
H
CH3
7h
7i
C6H5CH2
C2H5
H
C2H5
CH3
C2H5
CH3
C2H5
CH3
C6H5CH2CH2-
C6H5CH2CH2-
C6H5CH=CH-
C6H5CH=CH-
CH3
C2H5
CH3
C2H5
CH3
C2H5
C6H5
C6H5
7j
7k
7l
C6H4-2-NO2
C6H4-2-NO2
C6H5CH2-
7m
7n
4-NO2C6H4CH=CH-
4-NO2C6H4CH=CH-
7g
Scheme 1. Synthetic protocol of the target compounds 7ae7n. Reagents and conditions: (a) ammonia solution, methanol, reflux 8e16 h; (b) diethyl-2-bromomalonate, absolute
ethanol, reflux 15 h.

G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
99
Table 1
PTZ induced model
Physical data of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-
400
300
200
100
0
1,4-dihydropyridine-3,5-dicarboxylates (7ae7n)
Ar
COOR
ROOC
H3C
O
N
CH3
O
H3CH2C
CH2CH3
O
O
Compound
R
Ar
Mol. formula
M.P (ꢀC)
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
CH3
C2H5
CH3
C2H5
CH3
C2H5
CH3
C2H5
CH3
C2H5
CH3
C2H5
CH3
C2H5
H
H
C18H25NO8
C20H29NO8
C24H29NO8
C26H33NO8
C24H28N2O10
C26H32N2O10
C25H31NO8
C27H35NO8
C26H33NO8
C28H37NO8
C26H31NO8
C28H35NO8
C26H30N2O10
C28H34N2O10
220
226
224
228
225
229
226
230
228
234
237
238
238
239
test compounds
C6H5
C6H5
2-NO2C6H4
2-NO2C6H4
CH2C6H5
Fig. 2. Comparison of latency period with test compounds in PTZ method. Compounds
7ae7n were used at the dose of 10 mg/kg, whereas, diazepam was used as a standard.
CH2C6H5
except 7a. Compounds 7h and 7k showed increased latency period
and protection against mortality comparable to diazepam (5 mg/kg,
i.p). Compounds 7c, 7d, 7e, 7g, 7l, 7m and 7n showed increased
latency period better than diazepam, but exhibited moderate pro-
tection against mortality.
CH2CH2C6H5
CH2CH2C6H5
CH]CHC6H5
CH]CHC6H5
CH]CHC6H4-4-NO2
CH]CHC6H4-4-NO2
In the maximal electroshock method, compounds 7b, 7c, 7e, 7k,
7m and 7n showed significant protection against electroconvulsive
seizures (Table 2 and Fig. 3). However, other compounds 7a, 7d, 7fe
j and 7l did not show significant protection.
The anticonvulsant activity of compounds 7ae7n was evaluated
by the subcutaneous pentylenetetrazole (scPTZ) and maximal
electroshock (MES) screening methods, following oral administra-
tion of the compounds into male Wistar albino rats at the dose of
10 mg/kg and observations were made after 1 h [9,10]. The results
were shown in Table 2 and Fig. 2. All the compounds showed sig-
nificant protection against pentylenetetrazole induced convulsions,
2.3. Calculation of drug-likeness properties
Drug-likeness appears as a promising paradigm to encode the
balance among the molecular properties of a compound that
Table 2
Anticonvulsant activity of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4-dihydropyridine-3,5-dicarboxylates by scPTZ and MES methodsat 10 mg/kg
dose (p.o).
Test compounds
scPTZa
MESb
Latency period (s)
Protection against
mortality (%)
Duration of limb
extension (s)
Percentage protection
against electroconvulsive
seizures (%)
Mean ꢁ SEM
Mean ꢁ SEM
Control
Diazepam
Phenytoin
Nifedipine
7a
7b
7c
7d
7e
7f
7g
7h
7i
72 ꢁ 2
e
16 ꢁ 1
e
266 ꢁ 9***
e
66.6
e
e
e
6 ꢁ 1***
7 ꢁ 1***
13 ꢁ 1ns
9 ꢁ 1***
12 ꢁ 1*
13 ꢁ 1ns
10 ꢁ 1***
12ꢁ1ns
14 ꢁ 1ns
14 ꢁ 1ns
13 ꢁ 1ns
15 ꢁ 1ns
9 ꢁ 2***
12 ꢁ 1ns
7 ꢁ 1***
8 ꢁ 1***
62.5
56.8
14.5
41.6
25
16.6
39.6
22.9
14.5
10.4
20.8
8.3
215 ꢁ 3***
126 ꢁ 23**
192 ꢁ 5***
>300***
283 ꢁ 9***
295 ꢁ 3***
230 ꢁ 10***
285 ꢁ 5***
265 ꢁ 3***
>300***
246 ꢁ 7***
268 ꢁ 18***
>300***
>300***
>300***
33.3
0
0
33.3
0
0
0
33.3
66.6
66.6
33.3
100
0
7j
7k
7l
7m
7n
41.6
22.9
52.1
50
0
0
Values are expressed as mean ꢁ SEM, n ¼ 6. One way analysis of variance (ANOVA) followed by Dunnett’s method.
a
The test compounds were administered orally 1 h before the injection of PTZ (80 mg/kg, i.p) control: 0.5% sodium carboxymethylcellulose. Standard: nifedipine (30 mg/kg,
p.o) and diazepam (5 mg/kg, i.p). ***p < 0.0001 vs. control, **p < 0.05 vs. control.
b
The test compounds were administered 1 h before the application of maximal electroshock (150 mA, 0.2 s). Standard: nifedipine (30 mg/kg, p.o) and phenytoin (30 mg/kg,
oral). ***p < 0.0001 vs control, *p < 0.05 vs control, ns p > 0.05 vs control (not significant).

100
G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
Table 4
20
15
10
5
MES induced model
Prediction of pharmacokinetic properties of dialkyl 1-(di(ethoxycarbonyl)methyl)-
2,6-dimethyl-4-substituted-1,4-dihydropyridine-3,5-dicarboxylates (7ae7n).
Compound HIA (%) PCaco2 (nm/s) PMDCK (nm/s) iPPB (%) BB (Cbrain/Cblood
)
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
87.7
90.8
97.5
98.4
81.6
85.5
98.0
98.7
98.4
99.0
98.8
99.3
88.9
91.4
6.86
5.95
16.87
19.62
2.88
8.66
18.69
57.45
9.29
1.13
0.15
68.0
1.58
13.11
0.19
8.57
0.14
0.04
0.04
37.8
41.6
62.0
72.2
63.9
73.3
75.1
81.7
80.6
85.2
77.3
83.2
88.7
89.6
0.347
0.629
0.476
0.900
0.149
0.250
0.566
0.988
0.258
0.441
0.224
0.411
0.019
0.032
2.00
20.22
24.36
20.97
24.53
20.90
24.37
6.61
0
3.58
HIA (%), percentage human intestinal absorption; PCaco2 (nm/s), Caco2 cell perme-
ability in nm/s; PMDCK (nm/s), MadineDarby canine kidney cell permeability in
nm/s; iPPB(%), in vitro plasma protein binding (percentage); BB (Cbrain/Cblood), in vivo
bloodebrain barrier penetration.
test compounds
Fig. 3. Comparison of duration of limb extension with test compounds in MES method.
Compounds 7ae7n were used at the dose of 10 mg/kg, whereas, phenytoin and
nifedipine (30 mg/kg) were used as standards.
compounds displayed HIA more than 81% and bloodebrain barrier
penetration less than 2.0.
influences its pharmacodynamics and pharmacokinetics and ulti-
mately optimizes their absorption, distribution, metabolism and
excretion (ADME) in human body like a drug [11]. These parameters
allow to ascertaining oral absorption or membrane permeability
that occurs when the evaluated molecule follows Lipinski’s rule of
five [molecular weight (MW) ꢂ500 Da, log P ꢂ 5, H-bond donors
(HBD) ꢂ5 and H-bond acceptors (HBA) ꢂ10]. Molecules violating
more than one of these parameters may have problems with
bioavailability and high probability of failure to display drug-
likeness [12,13]. Other parameters that included are number of
rotatable bonds which indicate the flexibility of the molecule,
volume and polar surface area. The in silico estimation of human
intestinal absorption of a drug candidate involves numerous in vitro
methods like percent human intestinal absorption (HIA), Caco2
(PCaco2) and MDCK (PMDCK) cell models and BBB (Cbrain/Cblood) for
the prediction of oral drug absorption and bloodebrain barrier
penetrations respectively.
3. Discussion
We have synthesized fourteen derivatives of 1-(di(ethox-
ycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4-dihydro-pyri-
dine-3,5-dicarboxylates, 7ae7n with various substituents like
phenyl, benzyl, phenethyl, styryl and 4-nitrostyryl at position 4 and
increased the structural diversity at positions 3 and 5 by intro-
ducing methyl and ethyl groups. The reaction involved substitution
of diethylmalonyl group on the nitrogen of the 1,4-DHP ring. The
intermediate 1,4-dihydropyridine derivatives, 6ae6n were pre-
pared by Hantzsch condensation of methylacetoacetate (3) or
ethylacetoacetate (4) with various commercially available aromatic
aldehydes and ammonia solution [14,15].
The IR spectra of the synthesized compounds 7ae7n showed a
weak band at 3025e3015 cmꢃ1, due to the HeC]CeH stretch of
The above mentioned parameters were calculated for 7ae7n
and the results were presented in Tables 3and 4. From the data
obtained, it was observed that derivatives 7ae7d, 7g, 7i and 7k
were found to obey the Lipinski rule, whereas 7e, 7f, 7h, 7j, 7l, 7m
and 7n were found to violate in HBA and/or MW. All the
trans styryl group and a strong absorption band at 1730e1715 cmꢃ1
,
due to the C]O stretching of the
1H NMR spectra of compounds 7ae7n showed a triplet corre-
sponding to the CH3 protons at 1.2e1.4 ppm and a quartet at
4.1e4.3 ppm indicating the 2 protons of CH2. A characteristic
a,b-unsaturated ester moiety. The
d
d
Table 3
Structural properties of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4-dihydropyridine-3,5-dicarboxylates (7ae7n).
Compd
%ABS
MW
c log P
HBD
HBA
nviolations
nrotb
Volume
TPSA
Rule
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
e
<500
383
411
459
487
504
532
473
501
487
515
485
513
530
558
ꢂ5
<5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
<10
9
9
9
9
11
11
9
9
9
9
9
9
11
11
ꢂ1
0
0
0
0
2
2
0
1
0
1
0
1
2
2
e
e
e
71.6
71.6
71.6
71.6
55.7
55.7
71.6
71.6
71.6
71.6
71.6
71.6
55.7
55.7
1.38
1.88
2.49
3.27
2.77
3.55
2.57
3.349
2.95
3.73
3.03
3.82
3.31
4.09
11
13
12
14
13
15
13
15
14
16
13
15
14
16
347.88
381.48
419.31
452.92
442.65
476.25
436.11
469.72
452.92
486.52
446.73
480.33
470.06
503.67
108.4
108.4
108.4
108.4
154.28
154.28
108.45
108.45
108.45
108.45
108.45
108.45
154.28
154.28
%ABS, percentage of absorption; MW, molecular weight; HBD, number of H-bond donors; HBA, number of H-bond acceptors; nviolations, number of violations; nrotb, number
of rotatable bonds; TPSA, topological polar surface area.

G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
101
downfield shift of the CH protons attached to the nitrogen of the
dihydropyridine moiety was observed at 5.1e5.6 ppm. The aryl
protons were observed as multiplets at 6.5e7.9 ppm. A double
doublet appeared at
6.1e6.5 ppm (J ¼ 12e15 Hz) indicating the e
the derivatives were found not to have adequate bloodebrain
2
ꢀ
d
barrier penetration, as the TPSA values are more than 60 A .
Compounds 7ae7n showed human intestinal absorption of
more than 81% and are well absorbed (Table 4). All the compounds
are weakly bound to plasma proteins with optimum concentration
of unbound drug available for cell penetration. Compounds, 7ae7l
were found to have moderate penetration to CNS (0.98e0.14),
whereas 7m and 7n have low penetration (less than 0.1). However,
these compounds exhibited good anticonvulsant activity. There is
lack of correlation between anticonvulsant activity and poor brain
penetration of compounds 7m and 7n.
The computational data pertaining to the good oral absorption
of the compounds supported the oral anticonvulsant activity of this
series of compounds. A previous study on a series of 1-malonyl-1,4-
dihydropyridine derivatives demonstrated their ability to cross the
bloodebrain barrier at detectable concentrations [8]. But in our
study, computational TPSA calculations indicated that the com-
pounds containing 1-diethylmalonyl-1,4-dihydropyridine moiety
did not show adequate bloodebrain barrier penetration. The
calculated values did not correlate with the reported biological
activities of 1-malonyl-1,4-dihydropyridine derivatives as novel
carrier systems for the site specific and sustained drug delivery to
the brain and requires further experimental studies.
d
d
CH]CHe of styryl moiety present in 7ke7n. The mass spectra of
compounds (7ae7n) showed the molecular ion peaks at their
respective molecular weights and the elemental analysis for the
compounds is within the limits of ꢁ0.4% of theoretical values.
The compounds were evaluated for anticonvulsant activity at a
dose of 10 mg/kg orally in scPTZ and MES models. The results ob-
tained from scPTZ model revealed that compounds possessing 4-
phenyl substitution and methyl or ethyl group of 3,5-diester func-
tionality respectively as in 7c and 7d showed good activity than the
unsubstituted derivatives, 7a and 7b. 4-Benzyl and 4-phenethyl
substitutions were introduced as in 7g, 7h and 7i, 7j comprising
of one and two carbon separations respectively, between the
phenyl and 1,4-DHP ring system. This has led to retention of activity
when compared to 7c and 7d possessing no carbon spacer between
the phenyl and 1,4-DHP ring system, but improved the protection
against mortality.
Introduction of a double bond between the two carbon ethyl
spacer of 7i and 7j produced compounds 7k and 7l, which were also
found to possess similar latency period, but in 7k complete pro-
tection against mortality was observed. This may be attributed to
the presence of styryl moiety and the methyl group of ester func-
tionality. The electron withdrawing nitro group in the form of 2-
nitrophenyl and 4-nitrostyryl groups was attached to the 1,4-DHP
as in 7e, 7f and 7m, 7n respectively. There was no improvement
in activity in case of 7e and 7f, whereas 7m and 7n showed
increased latency period. The presence of styryl moiety attached to
1,4-DHP resulted in increase in the latency period and the activity is
comparable to the standard drug diazepam. However, the presence
of nitro group on styryl moiety improved the latency period, but
decreased the percentage protection against mortality. Replace-
ment of methyl group of ester functionality by ethyl did not influ-
ence the latency period as well as percentage protection.
4. Conclusion
The results obtained revealed that majority of the compounds
synthesized exhibited potent anticonvulsant activity in the PTZ
model. Only compound 7k showed significant protection against
mortality. Introduction of styryl and 4-nitrostyryl group on 1,4-
dihydropyridine nucleus resulted in analogues possessing good
anticonvulsant activity. Computational drug-likeness and TPSA
calculations revealed that the compounds showed good intestinal
absorption.
5. Experimental protocol
Compounds exhibiting activity against pentylenetetrazole test
can inhibit petit-mal seizures [16]. PTZ can induce seizures by
depressing chloride channel function by binding to picrotoxin site
in the GABA receptor complex. Drugs that can exhibit anticonvul-
sant activity against PTZ induced convulsions can raise seizure
threshold in the brain, enhancing GABAA receptor mediated
inhibitory neurotransmitter [17]. In the present study, the anti-
convulsant activity of the test compounds against PTZ induced
seizures may be due to inhibition of T-type Ca2þ currents and also
GABA receptor mediated inhibitory neurotransmission.
In the maximal electroshock model, compounds 7m and 7n
bearing 4-nitrostyryl group displayed good protection against sei-
zures. Compounds containing styryl, 2-nitrophenyl and unsub-
stituted 1,4-dihydropyridine ring showed moderate activity. Other
compounds did not exhibit significant activity. The activity of all the
derivatives was less than phenytoin (30 mg/kg). Substitution by
diethylmalonyl moiety at position 1 of nifedipine retained the
anticonvulsant activity.
5.1. Chemistry
Aldehydes and esters were procured from SigmaeAldrich and
Merck chemicals. All other chemicals are of AR grade. Purity of the
samples was monitored by TLC analysis using precoated aluminium
plates (Merck), coated with Silica Gel (Kieselgel 60) with F254 in-
dicator. Melting points were determined in open capillaries using
Analab melting point apparatus and were uncorrected. IR spectra
were recorded as KBr diluted pellets on a Jasco FTIR (FTIR-4100)
Spectrophotometer. 1H NMR spectra were carried out on Jeol-
400 MHz NMR spectrophotometer (JNM-400) using TMS as inter-
nal reference. Chemical shifts (d values) are given in parts per
million (ppm) using CDCl3 as solvent coupling constants (J) in Hz.
Splitting patterns are designated as follows: s, singlet; d, doublet; t,
triplet; q, quartet; dd, doublet of doublet; m, multiplet.
Accurate masses were obtained on LCMS (Schimadzu) APCI
model LC-2010 EV. Elemental analyses were performed on Perkin
Elmer 2400 C, H, N elemental analyser.
Drug-likeness was calculated by using Molinspiration and pre-
ADMET softwares and the data indicated that compounds 7ae7d,
7g, 7i and 7k obeyed the Lipinski’s rule-of-five (Table 3). Other
compounds such as 7e, 7f, 7h, 7j, 7l, 7m and 7n were found not to
have drug-likeness and not complied with more than one
descriptor. Topological polar surface area (TPSA) is recognized as a
good indicator of drug absorption in the intestine (TPSA less than
5.1.1. General method for the synthesis of dialkyl 2,6-dimethyl-4-
substituted-1,4-dihydro-pyridine-3,5-dicarboxylates (6ae6n)
A solution of aldehyde (0.01 mol), methylacetoacetate (0.03 mol,
3.2 ml) or ethylacetoacetate (0.03 mol, 3.8 ml) in methanol (20 ml)
was treated with ammonia solution (0.02 mol) and refluxed for 8e
16 h. After the completion of the reaction, the mixture was cooled
and evaporated to separate compounds 6ae6n. The crude com-
pound was purified by double recrystallization with methanol. The
yield obtained was 52e60%.
2
ꢀ
140 Angstroms squared [A ]) and bloodebrain barrier penetration
2
ꢀ
(TPSA less than 60 A ) [18,19]. The compounds exhibited compu-
2
ꢀ
tational topological polar surface area values less than 140 A and
have good intestinal absorption except 7e, 7f, 7m and 7n. However,

102
G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
5.1.2. General method for the synthesis of dialkyl 1-
5.1.2.5. Dimethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylate (7e).
0.03 mol (3.2 ml) of methylacetoacetate and 0.01 mol (1.51 g) of 2-
nitrobenzaldehyde were used and obtained the compound as
bright yellow crystals with 55% yield; IR (KBr) nmax, cmꢃ1: 3083
(AreCeH str), 2986 and 2955 (Alk, CeH str),1731 (ester, eC]O str),
(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4-
dihydro-pyridine-3,5-dicarboxylates, 7ae7n (Scheme 1)
To a stirred solution of 6ae6n (10 mmol) in 30 ml absolute
ethanol, a solution of diethyl-2-bromomalonate (20 mmol, 3.2 g) in
20 ml of absolute ethanol was added. The mixture was refluxed for
15 h; the completion of the reaction was monitored by TLC using n-
hexane:acetone (8:2). The solution was concentrated and the solid
was separated and recrystallized with aqueous ethanol to
obtain compounds 7ae7n [8].
1725 and 1717 (C]O str,
str, NO2), 1349 (NeO sym. str, NO2), 1164 (Alph, CeN str). 1H NMR
(400 MHz, CDCl3)
a,b unsaturated ester), 1433 (NeO asym.
d
(ppm): 1.28 (t, 6H, J ¼ 7.0 Hz, 2(CH3) of CH2CH3),
1.73 (s, 6H, 2(CH3) at C-2 and C-6), 3.74 (s, 6H, 2(CH3) of COOCH3 at
C-3 and C-5), 4.2 (q, 4H, J ¼ 7.0 Hz, 2(CH2) of COOCH2CH3), 4.29 (s,
1H, CH), 4.49 (s, 1H, CH(C-4)), 8.05 (m, 4H, C6H4NO2). Mass m/z:
502.9 (Mþ), 503.9 (M þ H) þ. Anal. Calcd for C24H28N2O10: C, 57.14;
H, 5.59; N, 5.55. Found: C, 57.08; H, 5.56; N, 5.51.
5.1.2.1. Dimethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethylpyridine-3,5- dicarboxylate (7a). 0.03 mol (3.2 ml) of
methylacetoacetate and 0.01 mol (0.55 ml) of formaldehyde were
used and obtained the compound as brown crystals with 48% yield;
IR (KBr) nmax, cmꢃ1: 3099 and 3083 (AreCeH str), 2996 and 2952
5.1.2.6. Diethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
(Alk, CeH str), 1731 (ester, eC]O str), 1721 (C]O str,
a
,
b
-unsatu-
dimethyl-4-(2-nitrophenyl)
pyridine-3,5-dicarboxylate
(7f).
rated ester), 1120 (Aliph, CeN str). 1H NMR (400 MHz, CDCl3)
0.03 mol (3.8 ml) of ethylacetoacetate and 0.01 mol (1.51 g) of 2-
nitrobenzaldehyde were used and obtained the compound as
d
(ppm): 1.28 (t, 6H, J ¼ 7.0 Hz, 2(CH3) of COOCH2CH3), 1.71 (s, 6H,
2(CH3) of CH3 at C-2 and C-6), 3.15 (s, 2H, CH2 on C-4), 3.76 (s, 6H,
2(CH3) of COOCH3), 4.2 (q, 4H, J ¼ 7 Hz, 2(CH2) of COOCH2CH3), 4.31
(s, 1H, CH at N-1). Mass m/z: 383.9 (M þ H)þ. Anal. Calc. for
pale yellow colour crystals with 53% yield; IR (KBr) nmax, cmꢃ1
:
3083 (AreCeH str), 2986 and 2955 (Alk, CeH str), 1731 (ester, eC]
O str), 1725 and 1717 (C]O str, unsaturated ester), 1433 (NeO
asym. str, NO2), 1349 (NeO sym. str, NO2), 1164 (Alph, CeN str). 1H
NMR (400 MHz, CDCl3)
a,b
C
18H25NO8: C, 56.39; H, 6.57; N, 3.65. Found: C, 56.18; H, 5.41; N,
4.01.
d
(ppm): 1.27 (t, 12H, J ¼ 7.1 Hz, 4(CH3) of
COOCH2CH3), 1.71 (s, 6H, 2CH3 on C-2 and C-6), 4.21 (m, 8H, 4(CH2)
of COOCH2CH3), 4.35 (s, 1H, CH of NeCH(COOEt)2), 4.47 (s, 1H, CH
on C-4), 8.1e6.75 (m, 4H, AreH C6H4NO2). Mass m/z: 531.9 (Mþ),
532.9 (M þ H)þ. Anal. Calc. for C26H32N2O10: C, 58.64; H, 604; N,
5.26. Found: C, 58.41; H, 6.04; N, 5.24.
5.1.2.2. Diethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethylpyridine3,5- dicarboxylate (7b). 0.03 mol (3.8 ml) of eth-
ylacetoacetate and 0.01 mol (0.55 ml) of formaldehyde were used
and obtained the compound as pale brown colour crystals with 50%
yield; IR (KBr) nmax, cmꢃ1: 3101 and 3082 (AreCeH str), 2996 and
2952, 2852 (Alk, CeH str), 1735 (ester, eC]O str), 1723 and 1715
5.1.2.7. Dimethyl 1-(di(ethoxycarbonyl)methyl)-4-benzyl-1,4-
dihydro-2,6-dimethyl pyridine-3,5-dicarboxylate (7g). 0.03 mol
(3.8 ml) of ethylacetoacetate and 0.01 mol (1.20 g) of phenyl-
acetaldehyde were used and obtained the compound as pale yellow
crystals with 51% yield; IR (KBr) nmax, cmꢃ1: 3081 (AreCeH str),
2996 and 2852 (Alk, CeH str), 1732 (ester, eC]O str), 1715 (eCH]
CHeC]O, C]O str), 1150 (Alph, CeN str). 1H NMR (400 MHz,
(C]O str,
(400 MHz, CHCl3)
COOCH2CH2), 1.07 (s, 6H, 2(CH3) of CH3 at C-2 and C-6), 3.2 (s, 2H,
CH2(C-4)), 4.13 (m, 8H, 4(CH2) of COOCH2CH3), 4.29 (s, 1H, CH of Ne
CH(COOEt)2). Mass m/z: 410.9 (M)þ. Anal. Calc. for C20H29NO8: C,
58.38; H, 7.08; N, 3.40. Found: C, 58.18; H, 7.08; N, 3.39.
a,b
-unsaturated ester), 1150 (Alph, CeN str). 1H NMR
d
(ppm): 1.3 (t, 12H, J ¼ 7.3 Hz, 2(CH3) of
CDCl3)
d
(ppm): 1.32 (t, 6H, J ¼ 6.9 Hz, 2(CH3) of CH2CH3), 1.7 (s, 6H,
5.1.2.3. Dimethyl-1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-phenyl pyridine-3,5-dicarboxylate (7c). 0.03 mol
(3.2 ml) of methylacetoacetate and 0.01 mol (1.1 ml) of benzalde-
hyde were used and obtained the compound as yellow fine crystals
with 51% yield; IR (KBr) nmax, cmꢃ1: 3101 and 3082 (AreCeH str),
2996 and 2952, 2852 (Alk, CeH str), 1735 (ester, eC]O str), 1723
and 1715 (eCH]CHeC]O, C]O str), 1150 (Alph, CeN str). 1H NMR
2(CH3) C-2 and C-6), 2.59 (d, 2H, J ¼ 6.4 Hz, CH2 of CH2C6H5), 3.52 (t,
1H, J ¼ 6.4 Hz, CH on C-4), 4.2 (q, 4H, J ¼ 6.9 Hz, 2(CH2) of
COOCH2CH3), 4.31 (s, 1H, CH of CH(COOEt)2), 7.21e7.0 (m, 5H, AreH
in CH2C6H5). Mass m/z: 473.9 (M þ H)þ. Anal. Calc. for C25H31NO8: C,
63.41; H, 6.66; N, 2.96. Found: C, 63.28; H, 6.58; N, 2.95.
5.1.2.8. Diethyl 1-(di(ethoxycarbonyl)methyl)-4-benzyl-1,4-dihydro-
2,6-dimethyl pyridine-3,5-dicarboxylate (7h). 0.03 mol (3.8 ml) of
ethylacetoacetate and 0.01 mol (1.20 g) of phenylacetaldehyde
were used and obtained the compound as pale yellow fine crystals
with 50% yield; IR (KBr) nmax, cmꢃ1: 3099 (AreCeH str), 2852 (Alk,
(400 MHz, CDCl3)
d
(ppm): 1.3 (t, 6H, J ¼ 7.1 Hz, 2(CH3) of
COOCH2CH3), 1.69 (s, 6H, 2(CH3) (C-2 and C-6)), 3.75 (s, 6H, 2(CH3)
of COOCH3 (C-3 and C-5)), 4.22 (q, 4H, J ¼ 7.1 Hz, 2(CH2) of
COOCH2CH3), 4.31 (s,1H, CH of CH(COOEt)2), 4.46 (s,1H, CH on C-4),
7.2e6.98 (m, 5H, AreH of C6H5). Mass m/z: 458.9 (M)þ. Anal. Calc.
for C24H29NO8: C, 62.73; H, 6.36; N, 3.05. Found: C, 62.48; H, 6.35; N,
3.04.
CeH str), 1735 (ester, eC]O str), 1718 (eCH]CHeC]O, C]O str),
1
1155 (Alph, CeN str). H NMR (400 MHz, CDCl3)
d (ppm): 1.25 (t,
12H, J ¼ 7.1 Hz, 4CH3 of COOCH2CH3),1.72 (s, 6H, 2CH3 on C-2 and C-
6), 2.61 (d, 2H, J ¼ 6.8 Hz, CH2 of CH2C6H5), 3.53 (t, 1H, J ¼ 6.8 Hz, CH
on C-4), 4.12 (m, 8H, 4CH2 of CH2COOCH2CH3), 4.31 (s, 1H, CH of Ne
CH(COOEt)2), 4.5 (s, 1H, CH on C-4), 7.25e7.05 (m, 5H, AreH of
CH2C6H5). Mass m/z: 501.9 (M þ H)þ. Anal. Calc. for C27H35NO8: C,
64.65; H, 7.03; N, 2.79. Found: C, 64.42; H, 7.01; N, 2.77.
5.1.2.4. Diethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-phenylpyridine-3,5-dicarboxylate
(7d). 0.03
mol
(3.8 ml) of ethylacetoacetate and 0.01 mol (1.1 ml) of benzaldehyde
were used and obtained the compound as yellow bulky crystals
with 49% yield; IR (KBr) nmax, cmꢃ1: 3099 and 3081 (AreCeH str),
2996 and 2852 (Alk, CeH str), 1732 (ester, eC]O str), 1715 (eCH]
CHeC]O, C]O str), 1150 (Alph, CeN str). 1H NMR (400 MHz,
5.1.2.9. Dimethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-phenethyl pyridine-3,5-dicarboxylate (7i). 0.03 mol
(3.2 ml) of methylacetoacetate and 0.01 mol (1.34 g) of 3-
phenylpropionaldehyde were used and obtained the compound
as dull yellow crystals with 52% yield; IR (KBr) nmax, cmꢃ1: 3089
(AreCeH str), 2862 (Alk, CeH str), 1736 (ester, eC]O str), 1725 (e
CH]CHeC]O, C]O str), 1158 (Alph, CeN str). 1H NMR (400 MHz,
CDCl3)
d
(ppm): 1.23 (12H, t, J ¼ 7.3 Hz, 4(CH3) of COOCH2CH3), 1.71
(s, 6H, 2(CH3) on C-2 and C-6), 4.15 (m, 8H, 4(CH2) of COOCH2CH3),
4.25 (s, 1H, NeCH), 4.45 (s,1H, CH on C-4), 7.25e6.9 (m, 5H, AreH of
C6H5). Mass m/z: 487.9 (M þ H)þ. Anal. Calc. for C26H33NO8: C,
64.05; H, 6.82; N, 2.87. Found: C, 63.80; H, 6.80; N, 2.88.

G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
103
CDCl3)
d
(ppm): 1.29 (t, 6H, J ¼ 7.3 Hz, 2CH3 of COOCH2CH3), 1.6 (t,
2CH3 of COOCH2CH3), 2.32 (s, 6H, CH3 on C-2 and C-6), 3.75 (s, 6H,
CH3 COOCH3), 4.17 (q, 4H, J ¼ 7.3 Hz, 2CH2 of COOCH2CH3), 4.62 (d,
1H, J ¼ 6.3 Hz, CH on C-4), 5.6 (s, 1H, CH of NeCH (COOEt)2), 6.1 (dd,
1H, J ¼ 14.2 Hz, eCH]CHC6H5), 6.21 (d, 1H, J ¼ 14.2 Hz, CH]CHe
C6H5), 8.0e7.1 (m, 4H, AreH of C6H4NO2). Mass m/z: 529.9 (M)þ.
Anal. Calc. for C26H30N2O10: C, 58.96; H, 5.7; N, 5.28. Found: C,
58.38; H, 5.26; N, 5.27.
2H, J ¼ 6.9 Hz, CH2 of eCH2eCH2eC6H5), 1.75 (s, 6H, 2CH3 on C-2
and C-6), 2.6 (t, 2H, J ¼ 6.9 Hz, CH2 of CH2CH2Ph), 3.52 (t, 1H,
J ¼ 7.01 Hz, CH on C-4), 3.75 (s, 6H, CH3, COOCH3), 4.2 (q, 4H,
J ¼ 7.3 Hz, 2CH2 of COOCH2CH3), 4.31 (s, 1H, CH of NeCHe
(COOEt)2), 7.3e7.05 (m, 5H, AreH of CH2CH2C6H5). Mass m/z: 486.9
(M)þ. Anal. Calc. for C26H33NO8: C, 64.05; H, 6.82; N, 2.87. Found: C,
63.99; H, 6.80; N, 2.86.
5.1.2.14. Diethyl 1-(di(ethoxycarbonyl)methyl)-4-(4-nitrostyryl)-1,4-
dihydro-2,6-dimethyl pyridine-3,5-dicarboxylate (7n). 0.03 mol
(3.8 ml) of ethylacetoacetate and 0.01 mol (1.77 g) of 4-
nitrocinnamaldehyde were used and obtained the compound
as pale yellow crystals with 53% yield. IR (KBr) nmax, cmꢃ1: 3081
(AreCeH str), 3023 (tran-CeH str), 2996 and 2952 (Alk, CeH str),
5.1.2.10. Diethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-phenethyl pyridine-3,5-dicarboxylate (7j). 0.03 mol
(3.8 ml) of ethylacetoacetate and 0.01 mol (1.34 g) of 3-
phenylpropionaldehyde were used and obtained the compound
as dull yellow crystals with 53% yield; IR (KBr) nmax, cmꢃ1: 3081
(AreCeH str), 2996 (Alk, CeH str), 1732 (ester, eC]O str), 1721 (e
CH]CHeC]O, C]O str), 1154 (Alph, CeN str). 1H NMR (400 MHz,
1738 (ester, eC]O, str), 1723 (C]O str
(trans C]C str), 1433 (NeO asym. str, NO2), 1349 (NeO sym. str,
NO2). 1H NMR (400 MHz, CDCl3)
a,b-unsaturated ester), 1648
CDCl3)
d
(ppm): 1.29 (t, 12H, J ¼ 7.3 Hz, 4CH3 of COOCH2CH3), 1.6 (t,
d
(ppm): 1.28 (t, 12H, J ¼ 7.3 Hz,
2H, J ¼ 6.9 Hz, CH2 of eCH2eCH2eC6H5), 1.75 (s, 6H, 2CH3 on C-2
and C-6), 2.6 (t, 2H, J ¼ 6.9 Hz, CH2 of CH2CH2Ph), 3.52 (t, 1H,
J ¼ 7.01 Hz, CH on C-4), 4.2 (m, 8H, 4CH2 of COOCH2CH3), 4.31 (s,1H,
CH of NeCHe(COOEt)2), 7.3e7.05 (m, 5H, AreH of CH2CH2C6H5).
Mass m/z: 514.9 (M)þ. Anal. Calc. for C28H37NO8: C, 65.23; H, 7.23; N,
2.72. Found: C, 65.18; H, 7.21; N, 2.73.
4CH3 of COOCH2CH3), 2.32 (s, 6H, CH3 on C-2 and C-6), 4.17 (m, 8H,
4CH2 of COOCH2CH3), 4.62 (d, 1H, J ¼ 6.3 Hz, CH on C-4), 5.6 (s, 1H,
CH of NeCH (COOEt)2), 6.1 (dd, 1H, J ¼ 13.5 Hz, eCH]CHC6H5), 6.21
(d, 1H, J ¼ 13.5 Hz, CH]CHeC6H5), 8.0e7.1 (m, 4H, AreH of
C6H4NO2). Mass m/z: 558.9 (M þ H)þ. Anal. Calc. for C28H34N2O10: C,
60.21; H, 6.14; N, 5.02. Found: C, 60.18; H, 6.04; N, 5.01.
5.1.2.11. Dimethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
5.2. Pharmacology
dimethyl-4-styryl
pyridine-3,5-dicarboxylate
(7k). 0.03
mol
(3.2 ml) of methylacetoacetate and 0.01 mol (1.32 g) of cinna-
maldehyde were used and obtained the compound as pale white
crystals with 50% yield; IR (KBr) nmax, cmꢃ1: 3081 (AreCeH str),
3023 (trans-CeH str), 2996 and 2952 (Alk, CeH str), 1738 (ester, e
Adult male Wistar rats (150e250 g) and Swiss albino mice (18e
20 g) were obtained from King Institute of Preventive Medicine,
Guindy, Chennai 32. The animals were acclimatized at least a week
under standard husbandry conditions, room temperature of
24 ꢁ 1 ꢀC, relative humidity 45e55% and a 12:12 h light/dark cycle.
The animals had free access to rodent pellet diet (Pranav Agro In-
dustry, Bangalore) and water under strict hygienic conditions. All
animal experiment protocols were approved by the Institutional
Animal Ethical Committee (IAEC) of Annamacharya college of
Pharmacy, Rajampet, India (1220/a/08/CPCSEA/ANCP/06).
C]O, str), 1723 (C]O str
a
,b
-unsaturated ester), 1648 (trans C]C
(ppm): 1.28 (t, 6H, J ¼ 7.1 Hz, 2CH3
str). 1H NMR (400 MHz, CDCl3)
d
of COOCH2CH3), 2.1 (s, 6H, 2CH3 on C-2 and C-6), 4.15 (q, 4H,
J ¼ 7.1 Hz of COOCH2CH3), 4.6 (d, 1H, J ¼ 6.3 Hz, CH on C-4), 5.15 (s,
1H, CH of NeCH(COOCH)2), 6.15 (dd, 1H, J ¼ 12.3 Hz, CH of eCH]
CHC6H5), 6.21 (d, 1H, J ¼ 12.3 Hz, eCH]CHeC6H5), 7.35e8.10 (m,
5H, AreH of CH]CHeC6H5). Mass m/z: 485.9 (M þ H)þ. Anal. Calc.
for C26H31NO8 found (theoretical); C 63.95 (64.32); H 6.04 (6.44); N
2.79 (2.88); O 27.22 (26.36). Anal. Calc. for C26H31NO8: C, 64.32; H,
6.44; N, 2.88. Found: C, 64.18; H, 6.41; N, 2.87.
5.2.1. Acute toxicity studies
The acute toxicity was estimated as per OECD-425 guidelines for
testing of chemicals acute oral toxicity [20]. The test was used to
find the safe dose for compounds 7ae7n. Swiss albino mice (18e
20 g) were divided into several groups each containing 5 animals.
Drugs were administered by oral route in different concentrations.
The animals were observed for their death over a period of seven
days.
5.1.2.12. Diethyl 1-(di(ethoxycarbonyl)methyl)-1,4-dihydro-2,6-
dimethyl-4-styryl pyridine-3,5-dicarboxylate (7l). 0.03 mol (3.8 ml)
of ethylacetoacetate and 0.01 mol (1.32 g) of cinnamaldehyde were
used and obtained the compound as white crystals with 55% yield;
IR (KBr) nmax, cmꢃ1: 3085 (AreCeeH str), 3021 (trans C]C str),
2986 and 2962 (Alk, CeH str), 1736 (ester, eC]O str), 1720 (C]O
5.2.2. Evaluation of anticonvulsant activity
str
CDCl3)
a
,
b
-unsaturated ester), 1645 (trans C]C str). 1H NMR (400 MHz,
(ppm): 1.28 (t, 12H, J ¼ 7.3 Hz, 4CH3 of COOCH2CH3), 2.32
5.2.2.1. The subcutaneous pentylenetetrazole seizure test (ScPTZ).
This method utilizes a dose of pentylenetetrazole (PTZ) 80 mg/kg in
rats that produces clonic seizures. The rats were divided into 16
groups of six rats each. Group 1 was the control group received
vehicle (0.5% sodium carboxymethylcellulose); group 2 received
(5 mg/kg, i.p) diazepam, groups 3e16 received (10 mg/kg, oral)
compounds 7ae7n respectively, which were prepared by sus-
pending in 0.5% sodium carboxymethylcellulose. All the drugs were
administered 1 h prior to the PTZ administration and the latency
period of the seizures and the mortality were observed [10]. The
seizure response was observed for a maximum period of 300sec.
d
(s, 6H, CH3 on C-2 and C-6), 4.17 (m, 8H, 2CH2 of COOCH2CH3), 4.62
(d, 1H, J ¼ 6.3, CH on C-4), 5.6 (s, 1H, CH of NeCH(COOEt)2), 6.1 (dd,
1H, J ¼ 12.8 Hz, eCH]CHC6H5), 6.21 (d, 1H, J ¼ 12.8 Hz, CH]CHe
C6H5), 7.35e7.1 (m, 5H, AreH of CH]CHeC6H5). Mass m/z: 512.9
(M)þ, 513.9 (M þ H)þ. Anal. Calc. for C28H35NO8: C, 65.48; H, 6.87; N,
2.73. Found: C, 65.38; H, 6.84; N, 2.72.
5.1.2.13. Dimethyl 1-(di(ethoxycarbonyl)methyl)-4-(4-nitrostyryl)-
1,4-dihydro-2,6-dimethyl
pyridine-3,5-dicarboxylate
(7m).
0.03 mol (3.2 ml) of methylacetoacetate and 0.01 mol (1.77 g) of 4-
nitrocinnamaldehyde were used and obtained the compound as
pale yellow crystals with 51% yield. IR (KBr) nmax, cmꢃ1: 3081 (Are
CeH str), 3023 (tran-CeH str), 2996 and 2952 (Alk, CeH str), 1738
5.2.2.2. The maximal electric shock (MES) test. The anticonvulsant
property of the drug in this model was assessed by its ability to
protect against maximal electric shock induced convulsions. The
rats were divided into 16 groups of six rats each. Group 1 was the
control group received vehicle; group 2 received (30 mg/kg, oral)
phenytoin, groups 3e16 received (10 mg/kg, oral) compounds 7ae
(ester, eC]O, str), 1723 (C]O str,
(trans C]C str), 1433 (NeO asym. str, NO2), 1349 (NeO sym. str,
NO2). 1H NMR (400 MHz, CDCl3)
(ppm): 1.28 (t, 12H, J ¼ 7.3 Hz,
a,b-unsaturated ester), 1648
d

104
G. Prasanthi et al. / European Journal of Medicinal Chemistry 73 (2014) 97e104
[6] C.K. Desai, R.K. Dikshit, S.M. Mansuri, U.H. Shah, Comparative evaluation of
anticonvulsant activity of calcium channel blockers in experimental animals,
Ind. J. Exp. Biol. 33 (2) (1995) 931e934.
[7] M. Abdel-Aziz, D. Abuo-RahmanGel, H.A. Hassan, H.H. Farag, N-malonyl-1,2-
dihydroisoquinoline as a novel carrier for specific delivery of drugs to the
brain, Arch. Pharm. (Weinheim) 343 (1) (Jan 2010) 54e60.
[8] H.A. Hassan, M. Abdel-Aziz, D. Abuo-Rahman Gel, H.H. Farag, 1-Malonyl-1,4-
dihydropyridine as a novel carrier for specific delivery of drugs to the brain,
Bioorg. Med. Chem. 17 (4) (Feb 15 2009) 1681e1692.
[9] J. Obniska, H. Byrtus, K. Kaminski, M. Pawlowski, M. Szczesio, J. Karolak-
Wojciechowska, Design, synthesis and anticonvulsant activity of new N-
Mannich bases derived from spirosuccinimides and spirohydantoins, Bioorg.
Med. Chem. 18 (2010) 6134e6142.
7n respectively, which were prepared by suspending in 0.5% so-
dium carboxymethylcellulose. Maximal electric shock of 150 mA
current for 0.2 s was applied through corneal electrodes to induce
convulsions in the control, standard and test compounds treated
animals. Abolition or reduction in the duration of hind limb
extension was considered as the index for anticonvulsant activity
[21].
5.2.3. Statistical analysis
All values were expressed as mean value ꢁ SEM. Tests of sig-
nificance were analyzed by one way analysis of variance (ANOVA)
followed by Dunnett’s test.
[10] M. Shekarchi, M. Binesh Marvasti, M. Sharifzadeh, Abbas Shafiee, Anticon-
vulsant activities of 7-phenyl-5H-thiazolo [5,4-e][1,2,3,4]tetrazolo[5,1-c]pyr-
rolo[1,2-a][1,4]diazepine and 7-phenyl-5H-thiazolo[5,4-e][1,3,4]triazolo[5,1-
c]pyrrolo[1,2-a][1,4] diazepines, Iran. J. Pharm. Res. 1 (2005) 33e36.
[11] G. Vistoli, A. Pedretti, B. Testa, Assessing drug-likeness
e what are we
missing? Drug. Discov. Today 13 (7e8) (2008) 285e294.
5.2.3.1. Calculation of drug-likeness properties. The parameters
for drug-likeness were evaluated according to the Lipinski’s
rule-of-five, using the Supercomputing Facility for Bioinformatics
[12] C.A. Lipinski, F. Lombardo, B.W. Dominy, P.J. Feeny, Experimental and
computational approaches to estimate solubility and permeability in drug
discovery and development settings, Adv. Drug Deliv. Rev. 23 (1997) 3e25.
[13] Supercomputing Facility for Bioinformatics & Computational Biology-IIT Delhi,
Lipinski Filters. Available from: http://www.scfbio-iitd.res.in (last accessed
12.09.12).
[14] F. Catessi, M. Zacchigna, N. Pedemonte, L.J. Galietta, M.T. Mazzei, P. Fossa,
M. Giampieri, M. Mazzei, Synthesis of 4-thiophen-2-yl-1,4-dihydropyridines
as potentiators of CFTR chloride channel, Bioorg. Med. Chem. 17 (2009)
7894e7903.
&
Computational Biology-IIT Delhi [13] and TPSA values
from Molinspiration online property calculator tool kit [22]. Topo-
logical polar surface area was used to calculate the percentage
of absorption (%ABS) according to the equation:
%
ABS ¼ 109 ꢃ [0.345 ꢄ TPSA] [23]. In vitro %HIA, Caco2 and MDCK
cell permeabilities, plasma protein binding and bloodebrain bar-
rier penetration values were obtained from ADME calculator [24].
[15] A. Zarghi, H. Sadeghi, A. Fassihi, M. Faizi, A. Shafiee, Synthesis and calcium
antagonist activity of 1,4-dihydropyridines containing phenyl amino-
imidazolyl substituents, II Farmaco 58 (2003) 1077e1081.
[16] H. Hosseinzadeh, M. Madanifard, Anticonvulsant effects of Coriandrum sat-
ivum L. seed extracts in mice, Arch. Iran. Med. 3 (4) (2000) 81e84.
[17] S. Bolaris, C. Caterina, T. Valcana, M. Margarity, Pentylenetetrazole-induced
convulsions affect cellular and molecular parameters of the mechanism of
action of triiodothyronine in adult rat brain, Neuropharmacology 48 (2005)
894e902.
[18] P. Ertl, B. Rodhe, P. Selzer, Fast calculation of molecular polar surface areas as a
sum of fragment based contribution and its application to the prediction of
drug transport properties, J. Med. Chem. 43 (2000) 3714e3717.
[19] S. Prasanna, R.J. Doerksen, Topological polar surface area: a useful descriptor
in 2D-QSAR, Curr. Med. Chem. 16 (1) (2009) 21e41.
Appendix A. Supplementary data
Supplementary material associated with this article can be
found in the online version, at doi:10.1016/j.ejmech.2013.12.001.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
References
[20] OECD Guide Line for Testing of Chemicals. Available online: http://iccvam.
niehs.nih.gov/suppDocs/FedDocs/OECD/OECD_GL425.pdf (accessed 04.12.12).
[21] B.B. Subudhi, P.K. Panda, S.P. Swain, P. Sarangi, Synthesis, characterization and
anticonvulsant evaluation of some 1,4-dihydropyridines and 3,5-(substituted)
[1] M. Zaheen Hassan, S.A. Khan, M. Amir, Design, synthesis and evaluation of N-
(substituted benzothiazol-2-yl)amides as anticonvulsant and neuroprotective,
Eur. J. Med. Chem. 58 (2012) 206e213.
oxocarbamyl-1,4-dihydro-2,6-dimethyl-N-(2-(4-sulfamoyl
phenylamino)-
acetyl)-4-substitutedpyridines, Acta Pol. Pharm. 66 (2009) 147e153.
[22] Molinspiration Cheminformatics, Web-enabled Software for Large-scale
Calculation of Molecular Properties and Database Searches. Free Online Mo-
lecular Descriptor Calculations. Available from: http://www.molinspiration.
com/services/properties.html (last accessed 22.11.12).
[23] M.J. Ahsan, J.G. Samy, H. Khalilullah, M.S. Nomani, P. Saraswat, R. Gaur,
A. Singh, Molecular properties prediction and synthesis of novel 1,3,4-oxa-
diazole analogues as potent antimicrobial and antitubercular agents, Bioorg.
Med. Chem. Lett. 21 (2011) 7246e7250.
[2] P. Chen, N. Bodor, W.M. Wu, L. Prokai, Strategies to target kyotorphin ana-
logues to the brain, J. Med. Chem. 41 (1998) 3773e3781.
[3] E. Pop, E. Shek, T. Murakami, N.S. Bodor, Improved anticonvulsant activity of
phenytoin by a redox brain delivery system I: synthesis and some properties
of the dihydropyridine derivatives, J. Pharm. Sci. 78 (8) (August 1989) 609e
616.
[4] C. Luna-Tortos, B. Rambeck, U.H. Jurgen, W. Loscher, The antiepileptic drug
topiramate is a substrate for human P-glycoprotein but not multidrug resis-
tance proteins, Pharm. Res. 26 (2009) 2464e2470.
[24] PreADMET, A Web-based Application for Predicting ADME Data and Building
Drug-like Library Using In Silico Method. Available from: http://www.
preadmet.bmdc.org/index.php (last accessed 28.11.12).
[5] G. Masotti, A. Morettini, G. Galanti, G. Paoli, L. Poggesi, Antihypertensive ac-
tion of nifedipine: effects on arteries and veins, J. Clin. Pharmcol. 25 (1) (Jane
Feb 1985) 27e35.