Design and comparative anticonvulsant activity assessment of CNS-active alkyl-carbamoyl imidazole derivatives

Article abstract of DOI:10.1016/j.bmc.2016.07.018

A novel series of carbamoyl derivatives of alkylimidazole has been designed and their anticonvulsant activity was comparatively evaluated in the mice- and rats-maximal-electroshock (MES), subcutaneous-metrazol (scMet) seizure tests and the mice-6?Hz psych

Full text of DOI:10.1016/j.bmc.2016.07.018

Bioorganic & Medicinal Chemistry xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Design and comparative anticonvulsant activity assessment
of CNS-active alkyl-carbamoyl imidazole derivatives
Hafiz Mawasi a, David Bibi a, Meir Bialer a,b,
⇑
a Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, PO 12065, Jerusalem 91120, Israel
b David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Israel
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of carbamoyl derivatives of alkylimidazole has been designed and their anticonvulsant
activity was comparatively evaluated in the mice- and rats-maximal-electroshock (MES), subcuta-
neous-metrazol (scMet) seizure tests and the mice-6 Hz psychomotor (6 Hz) models. The ten new
designed molecules contain in their chemical structure imidazole, alkyl side-chain and carbamate as
three potential active moieties.
Received 20 March 2016
Revised 4 July 2016
Accepted 9 July 2016
Available online xxxx
In spite of the close structural features of the carbamoyl imidazole derivatives only compounds 7, 8, 13
and 16 were active at the MES test with ED50 values ranging from 12 to 20 mg/kg coupled with high pro-
tective index (PI = TD50/ED50) values of 4.1–7.3 after ip administration to rats. A similar phenomenon was
observed in mice where compounds 7, 8, 9, 12 had MES-ED50 values of 14–26 mg/kg. Compounds 7 and
13 also demonstrated anticonvulsant activity in the 6 Hz model with ED50 values of 32 and 44 mg/kg,
respectively. As the most active entities, compounds 7, 8 followed by 13 and 16, thus offer an optimal
efficacy–safety profile and consequently, might be promising candidates for development as new
antiepileptics.
Keywords:
New antiepileptic drugs
Alkyl-carbamoyl imidazole derivatives
Anticonvulsant activity
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
sant activity. (b) Substitution at the para position of the phenyl ring
exhibits a better therapeutic index than substitution at the ortho or
meta positions. (c) The anticonvulsant activity increased with an
increase in R however this was not the only parameter influencing
potency.5–7
Epilepsy is a common and chronic neurological disorder.1 In
spite of the availability of >20 old and new antiepileptic drugs
(AEDs) approximately 30% of the patients with epilepsy are not sei-
zure free, despite receiving AED therapy.2
Among the new clinical candidates synthesized in the 1980s as
AEDs there were two alkyl/aryl imidazole derivatives denzimol (1)
and nafimidone (2) (Fig. 1).3,4 Structure activity relationship (SAR)
studies of this series of compounds derived from the general for-
mula (3, Fig. 1) revealed the followings: (a) Branching or lengthen-
ing the aliphatic chain between the imidazole and the aryl moiety
or the presence of carbonyl and carbinol group in A (of formula 3
depicted in Fig. 2) altered minimally the compounds’ anticonvul-
Denzimol was active in the maximal electroshock (MES), metra-
zol (scMet)-induced seizure models and its major pharmacokinetic
(PK) parameters in humans were: clearance—0.3 L/h/kg; volume of
distribution—3 L/kg and half-life 5–7 h.5 When co-administered
with phenytoin or carbamazepine there was a clinically-relevant
elevation in the plasma levels of phenytoin and carbamazepine
and its primary metabolite carbamazepine epoxide.8
Nafimidone (2) is an imidazole derivative with an anticonvul-
sant profile similar to that of carbamazepine and phenytoin. A pilot
study showed 33–98% improvement in seizure control in 12
patients treated with nafimidone (600 mg/day) for up to one year.9
Subsequent studies showed that nafimidone had poor therapeu-
tic/toxic ratio coupled with profound inhibition of carbamazepine
and phenytoin metabolism in humans.10,11 These observations
led to the termination of its development as a new AED.
The discovery in the 1960s that meprobamate (4, Fig. 1) an old
dicarbamate anxiolytic also possessed anticonvulsant activity
prompted the design and evaluation of several anticonvulsant
Abbreviations: CNS, central nervous system; AED, antiepileptic drug; NIH,
National Institute of Health; SAR, structure–activity relationship; MES, maximal
electroshock seizure; scMet, subcutaneous metrazol; ED50, dose effective in 50% of
test subjects; TD50, dose neurotoxic in 50% of test subjects; PI, protective index;
BBB, blood–brain barrier; ip, intraperitoneally; CDI, 1,10-carbonyldiimidazole; TEA,
trimethylamine; DCM, dichloromethane; NMR, nuclear magnetic resonance; GC–
MS, gas chromatography–mass spectrometry; TLC, thin-layer chromatography.
⇑
Corresponding author. Tel.: +972 2 6758610; fax: +972 2 6757246.
E-mail address: bialer@md.huji.ac.il (M. Bialer).
http://dx.doi.org/10.1016/j.bmc.2016.07.018
0968-0896/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

2
H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
N
N
N
N
OH
O
denzimol (1)
nafimidone (2)
R1
n
N
N
A
R2
general structure of alkylimidazoles (3)
O
NH2
Cl OH
O
O
O
O
NH2
H2N
O
O
NH2
O
O
NH2
felbamOate (5)
carisbamate (6)
meprobamate (4)
Figure 1. Chemical structures of denzimol (1), nafimidone (2), general structure of alkylimidazoles (3), meprobamate (4), felbamate (5) and carisbamate (6).
O
O
O
O
N
H
N
O
N
H
N
O
N
H
N
N
N
N
(9)
(7)
(8)
O
O
O
O
N
N
O
N
H
N
O
N
N
N
N
N
H
H
(12)
(10)
(11)
O
O
O
O
N
N
O
N
H
N
O
N
H
N
N
N
N
H
(14)
(13)
(15)
O
O
N
H
N
N
(16)
Figure 2. Structures of synthesized and tested carbamoyl alkylimidazoles.
carbamates.12–14 SAR studies of carbamates showed that deriva-
tives with two alkyl groups attached at C-2 possess stronger mus-
cle paralyzing activity, whereas the presence of a phenyl group at
the 2 position enhances anticonvulsant activity.14–16 Felbamate (5,
Fig. 1), exhibited a broad anticonvulsant activity and was approved
by the FDA in 1993 as a new AED for monotherapy with great
expectations.17,18 However, it is currently not used frequently in
clinical practice due to the fatal aplastic anemia and hepatotoxicity
associated with its therapy.19 However, given its usefulness in
therapy-resistant epilepsies felbamate is part of the current
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
3
Table 1
antiepileptic arsenal. Felbamate clinical use presents safety con-
cerns, but they can be avoided or minimized with requisite mea-
sures and precautions.20 Another anticonvulsant carbamate that
reached phase III clinical trials was carisbamate (6, Fig. 1); how-
ever, its new drug application (dossier) to the FDA and EMA was
withdrawn in 2010 due to lack of consistent efficacy across a clin-
ically-relevant dose range.21
In 2012 we showed that very minor structural changes in
branched alkyl carbamates had a significant influence on the phar-
macological profile of the tested compounds.22 Subsequently, in
the current study we have synthesized ten new carbamoyl deriva-
tives of alkylimidazole depicted in Figure 2 and their anticonvul-
sant activity and neurotoxicity were comparatively evaluated in
order to establish if some of these alkylimidazole derivatives might
become potential candidates for further development as new AEDs.
Anticonvulsant activity in the MES and 6 Hz models and neurotoxicity (minimal
behavioral impairment) of compounds 8–17 administered ip to mice
Compound
Dose (mg/kg)
MESa
6 Hza,b
Toxa
0.5 h
2.0 h
0.5 h
2.0 h
0.5 h
2.0 h
7
30
100
300
1/4
4/4
2/2
0/4
2/4
0/0
0/4
4/4
2/2
0/4
4/4
1/1
0/8
6/8
8/8
0/8
1/8
8/8
8
30
100
300
1/4
4/4
/
0/4
3/4
/
0/4
3/4
/
0/4
2/4
/
0/8
7/8
8/8
0/8
0/8
4/4
9
30
100
300
3/4
4/4
/
0/4
4/4
/
1/4
3/4
/
0/4
1/4
/
0/8
4/8
8/8
0/8
0/8
8/8
10
11
12
13
14
15
16
30
100
300
1/4
4/4
/
0/4
4/4
/
0/4
2/4
/
0/4
1/4
/
0/8
5/8
4/4
0/8
0/8
4/4
2. Results
30
100
300
0/4
4/4
/
0/4
3/4
/
0/4
2/3
/
0/4
0/4
/
0/8
2/7
8/8
0/8
0/7
8/8
2.1. Chemistry
30
100
300
4/4
4/4
1/1
0/4
4/4
1/1
0/4
4/4
/
0/4
3/4
/
0/8
6/8
8/8
0/8
0/8
8/8
Compounds 7–16 (Fig. 2) were synthesized in a two step reac-
tion according to Scheme 1. The alkyl alcohols were either com-
mercially available or were synthesized according to literature
procedure.22 By the reaction of the appropriate alkyl alcohol with
CDI in the presence of TEA in DCM, the intermediate compound
2 (alkylimidazole carboxylate) was synthesized (Scheme 1), after
washing with water without any further purification in high yields.
Compound 3 was prepared by adding 1-(3-aminopropyl)imidazole
to intermediate 2 in DCM and in presence of TEA for few hours at
room temperature. Compounds 7–16 (Fig. 2) were obtained with
isolated yields ranging between 65% and 82%.
30
100
300
1/4
4/4
/
0/4
4/4
/
0/4
4/4
/
0/4
1/4
/
0/8
8/8
4/4
0/8
0/8
/
30
100
300
0/4
4/4
1/1
0/4
4/4
0/0
0/4
3/4
/
0/4
0/4
/
0/8
1/8
1/1
0/8
0/8
0/0
30
100
300
0/4
3/4
0/4
0/4
4/4
2/2
0/4
0/3
0/1
0/4
0/4
0/0
0/8
1/8
7/8
0/8
0/8
6/8
30
100
300
4/4
4/4
/
1/4
4/4
/
1/4
3/4
2/2
0/4
3/4
0/0
0/8
1/8
8/8
0/8
0/8
8/8
2.2. Pharmacology
a
Data indicate number of mice protected/number of mice tested. The animals
The anticonvulsant activity profile of compounds 7–16 was
determined using the MES test, which measures seizure spread,
scMet test, which measures seizure threshold and the 6 Hz (32
and 44 mA) psychomotor test. These tests are mechanism-inde-
pendent animal seizure models that enable identification of com-
pounds preventing seizure spread.23,24 Compounds 7–16 were
administered ip to mice and po to rats at fixed doses of 30, 100
or 300 mg/kg, and the anticonvulsant protection was observed at
different times after dosing. The method applied here allowed
the determination of the number of animals (in a group consisting
of 4 or 8 mice or rats) protected against electrically- or chemically-
induced seizures as well as the estimation of the time course of
anticonvulsant activity together with time of peak effect (TPE).
Table 1 presents the anticonvulsant activity and neurotoxicity
or minimal behavioral impairment of compounds 7–16 at the
mice-MES and mice 6 Hz (32 mA) tests (ip). At the 6 Hz model
(32 mA), almost all compounds did not show any protection at
30 mg/kg. However, compounds 7 and 8 showed partial protection
with no neurotoxicity at a dose of 50 mg/kg (Table 1 of Supporting
information) at the 6 Hz (44 mA) test.
were examined at two pretreatment times: 0.5 and 2 h.
b
The 6 Hz psychomotor test is run with 32 mA.
and oral dosing. All tested compounds showed no neurotoxicity
at 30 mg/kg and the most potent compounds were 7–10, 12, 13
and 16 after ip administration. The results showed significant dif-
ference between efficacy and neurotoxicity at the tested doses for
compounds 7–10 and 12–16 at the rat-MES test.
Comparative quantitative evaluation at the rat-MES (ip) test
showed that compounds 7, 8, 13 and 16 had ED50 values ranging
between 12 to 20 mg/kg and high protective index (PI = TD50
ED50) with values of 4.1–7.3 (Table 3). A similar phenomenon
was observed in mice where compounds 7, 8, 9, 12 and 16 had
MES-ED50 values of 14–28 mg/kg (Table 4). Compounds 7 and 13
also demonstrated anticonvulsant activity in the mice-6 Hz
(32 mA) model with ED50 values of 32 and 44 mg/kg, respectively
(Table 4). At the scMet test, all compounds were inactive at a dose
of lower than 70 mg/kg.
A reasonable prediction of a compound’s potential as a new AED
candidate is based on the characterization of the compound’s anti-
convulsant profile in different animal (mice and/or rats) mod-
els.23,24 Although there are various anti-seizure animal models,
the MES and scMet seizure models remain the ‘gold standards’ in
early stages of discovery of new AEDs and have gained an apprecia-
ble degree of predictability since the MES was first utilized in the
discovery of the anticonvulsant activity of phenytoin (1938).23–26
The optimal balance between lipophilic and hydrophilic moi-
eties (logP) is a very important consideration in designing AEDs.27
Although clogP is not the only determinant of compounds’ BBB
/
Table 2 presents the anticonvulsant activity and neurotoxicity
of compounds 7–10 and 12–16 at the rat-MES test following ip
R''
R''
O
O
R''
(b)
(a)
R'
O
N
H
(3)
N
R'
O
N
R'
OH
N
N
(1)
(2)
Scheme 1. General synthesis of carbamoyle alkylimidazoles (3). Reagents and
conditions: (a) CDI, TEA, DCM, room temperature, 1–5 h; (b) 1-(3-aminopropyl)
imidazole, TEA, DCM, room temperature, 2–7 h (see Section 5).
permeability, previous studies showed that is
between anticonvulsant activity and ClogP values, mainly as a
a correlation
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

4
H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
Table 2
Anticonvulsant activity in the MES model and neurotoxicity of compounds 7–10 and 12–16 after ip and po administrations to rats (dose of 30 mg/kg)
Compound
Admin. route
MESa
Toxa
0.25 h
0.5 h
1.0 h
2.0 h
0.25 h
0.5 h
1.0 h
2.0 h
7
ip
po
4/4
1/4
4/4
0/4
3/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
8
ip
po
3/4
1/4
3/4
1/4
3/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
9
ip
po
2/4
0/4
4/4
1/4
3/4
2/4
3/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
10
12
13
14
15
16
ip
po
3/4
0/4
3/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
ip
po
4/4
2/4
4/4
3/4
2/4
2/4
2/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
ip
po
3/4
0/4
3/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
ip
po
1/4
0/4
1/4
0/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
ip
po
/
/
/
/
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
1/4
0/4
0/4
0/4
ip
po
4/4
1/4
4/4
0/4
4/4
0/4
4/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
a
Data indicate number of mice protected/number of mice tested. The animals were examined at four pretreatment times: 0.25, 0.5, 1 and 2 h.
Table 3
3. Discussion
Quantitative anticonvulsant data (ED50, TD50, and PI values) in rats dosed ipa
Compound
MES-ED50
PIc
scMet
PIc
Tox-TD50
(mg/kg) [95%CI]
The three major approaches for designing and developing new
AEDs are: (a) Target or mechanism of action-based design;31–34
(b) Design of follow-up compounds of existing AEDs;35,36 and (c)
the phenotypic or empirical approach that is based on the screen-
ing of drug candidates in anticonvulsant animal (rodent) mod-
els.35–38
In this study, we combined approaches b and c namely, the sec-
ond generation which aims to circumvent problems associated
with the first generation AEDs and the screening of drug candi-
dates in anticonvulsant animal (rodent) models of epilepsy. As a
result, we have designed, synthesized, and evaluated ten new car-
bamoyl alkylimidazole derivatives and explored how small modifi-
cations on the carbamate ester moiety, such as length and
branching, affect the anticonvulsant profile.
(mg/kg) [95%CI]a,b
(mg/kg)b
7
8
13
16
12 (8–17)
20 (14–29)
17 (14–20)
17 (13–21)
7.3
4.8
4.1
5.4
>88
>95
>70
>92
1.0
1.0
1.0
1.0
87 (63–123)
96 (76–125)
70 (51–85)
92 (57–114)
a
Median Effective (ED50) and Toxic (TD50) values. In squared parentheses are the
95% confidence intervals (95%CI) determined by probit analysis.
b
The time of peak effect was 0.25 h.
Protective Index (PI = TD50/ED50).
c
result of an increased blood–brain barrier (BBB) penetration.28,29
The branched aliphatic carbamoyl-alkylimidazoles 7 and 8 that
possessed the most potent (lowest) ED50 values had also the high-
est logP values (Table 5), which implies that BBB penetration due
to lipophilicity is an important factor in affecting drugs anticonvul-
sant efficacy.30
Nine of the 10 compounds synthesized and analyzed are very
closely related and our focus was to study the impact of the alkyl
side changes on the anticonvulsant activity while keeping constant
Table 4
Quantitative anticonvulsant data (ED50, TD50, and PI values) in mice dosed ipa
Compound
MESED50 (mg/kg) [95%CI]a,b
PIc
scMet (mg/kg)b
PIc
6Hz- ED50 (mg/kg) [95%CI]a,b
PIc
ToxTD50 (mg/kg) [95%CI]
7
8
9
12
13
16
18 (16–22)
24 (20–26)
26 (22–30)
14 (10–18)
NAd
28 (22–32)
25 (19–30)
485 (324–677)
20 (15–27)
3.3
2.8
3.9
5.5
—
3.1
>20
1.6
2.4
>70
>100
>85
0.9
0.67
1.2
0.96
—
32 (24–39)
NAd
2.0
—
—
—
1.4
0.64
65 (62–68)
67 (62–71)
102.0 (92–116)
77 (70–87)
60 (56–65)
86 (77–94)
>500
NAd
>80
NAd
44 (28–52)
135 (97–175)
NAd
>50
>250
646 (466–869)
21 (15–27)
1.7
Felbamate (5)e
VPA (17)e
SPD (18)f
1.2
2.3
—
—
1.8
784 (503–1176)
48 (32–36)
27 (24–30)
A dash indicates not tested.
a
Median effective (ED50) and toxic (TD50) values. In squared parentheses are the 95% confidence intervals (95%CI) determined by probit analysis.
b
c
d
e
f
The time of peak effect was 0.5 h.
Protective Index (PI = TD50/ED50).
NA indicates not active.
Data taken from Ref. 23.
Data taken from Ref. 39.
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
5
Table 5
in the years 2001–2011, amounting to 13% approved by the FDA
and 9% worldwide.41 Compounds 7, 8, followed by 13 and 16, thus,
offer an optimal efficacy–safety profile and consequently, might be
promising candidates for development as new antiepileptics.
Lipophilicity data (ClogP) of the investigated compounds
Compound
ClogPa
1
2
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
3.18
2.21
0.91
0.49
0.95
2.9
2.52
1.35
1.34
2.19
1.31
2.15
1.25
1.06
1.34
2.76
2.23
4. Experimental section
4.1. Chemistry
Unless otherwise stated, all reagents were purchased from com-
mercial suppliers and used without further purification. Solvents
used in the reactions were distilled from appropriate drying agents
prior to use.
4.2. Materials and methods
Reactions were monitored by thin-layer chromatography (TLC)
on silica gel 60 F254 aluminum plates (Merck) and/or gas chro-
matography–mass spectrometry (GCMS). Visualization of com-
pounds on TLC was accomplished by (UV or KMnO4). GCMS
analysis was performed with HP5890 Series II GC equipped with
a Hewlett–Packard MS Engine (HP5989A) single quadrupole MS,
HP7673 autosampler, HP MS-DOS Chemstation, and HP-5MS capil-
a
ClogP was calculated by utilizing the ChemDraw Ultra
software, version 12.
all other chemical moieties (i.e. the imidazole, carbamates and the
spacer between them). Compound 7 is a carbamoyl valproyl-imi-
dazole and compounds 16 and 9 are homologues compounds of
7 with one or two less carbons, respectively. Similarly compounds
15, 10 and 13 are homologous compounds all containing a tert-
butyl alkyl moiety in their alkyl side chain.
lary column (0.25
lm ꢀ 15 m ꢀ 0.25 mm). The temperature pro-
gram was as follows: injector temperature, 180 °C; initial
temperature, 40 °C for 6 min; gradient of 20 °C/min until 140 °C;
gradient of 10 °C/min until 200 °C; and hold time, 3 min. The MS
parameters were set as follows: source temperature, 180 °C; trans-
fer line, 280 °C; positive ion monitoring; and EI-MS (70 eV). Col-
umn chromatography was performed using silica gel 60 (particle
size 0.040–0.063 mm: check if this is what you are using) pur-
chased from Sigma–Aldrich.
Although all synthesized and tested alkylimidazoles (except 12)
contain closely-related branched aliphatic side-chain with 5–9 car-
bons, only compounds 7, 8, 13 and 16 were active at the rat-MES
test with ED50 values ranging from 12 to 20 mg/kg coupled with
high PI values of 4.1–7.3. A similar phenomenon was observed in
mice where compounds 7, 8, 9, 12 had MES-ED50 values of 14–
28 mg/kg. The most active compounds 7 and 8 are carbamate
esters of the alcoholic congeners of valproic acid (VPA-17) and
sec-butylpropylacetamide (SPD-18), respectively (Fig. 3). Reduc-
tion of the valproyl (or iso-octanoyl) side chain of compound 7
by one or two carbons led to compounds 16 and 9, respectively
that were equipotent to 7 at mice-MES test but were four time less
potent (16) or inactive (9) at the 6 Hz test. In rat-MES test com-
pound 16 (but not 9) was equipotent to 7. The lower anticonvul-
sant activity of compound 16 following oral administration might
be due to low oral bioavailability. Among the carbamoyl-imidazole
derivatives containing a tert-butyl alkyl moiety, compound 13
being a constitutional isomer of 7 was the most active compound.
SPD is an amide derivative of VPA with unique anticonvulsant
activity that is more potent than VPA.40,41 As depicted in Table 4
compounds 7 and 8 were more potent than VPA and equipotent
to SPD at the rat-MES test but not at the scMet model. Compounds
7 and 13 also demonstrated anticonvulsant activity in the mice
6 Hz model with ED50 values of 32 and 44 mg/kg, respectively.
Compounds 16 and 8 are chiral compounds containing one and
two stereogenic carbons, respectively, that were synthesized and
analyzed here as racemate. Although there is a need to develop
and analyze individual enantiomers, racemate have not disap-
peared from the list of New Molecular Entirety (NME) approvals
Proton NMR spectra were recorded on Varian Mercury 300 MHz
spectrometer in deuterated solvent. Proton chemical shifts are
reported in ppm (d) relative to tetramethylsilane with the solvent
resonance employed as the internal standard (CDCl3, d 7.26 ppm).
Data are reported as follows: chemical shift, multiplicity (s = sin-
glet, d = doublet, t = triplet, q = quartet, m = multiplet)
Chemical structures of the newly synthesized compounds were
assessed by 1H NMR and elemental analysis. Elemental analysis
was performed on a 2400–2 Perkin–Elmer C, H, N analyzer. Ele-
mental analyses (C, H, N) were used to confirm the purity of all
newly synthesized compounds (>95%), results within 0.4 of theo-
retical values.
4.3. General procedure for the synthesis of compounds 7–16
Primary alcohol (50 mmol) was added to a mixture of CDI
(55 mmol) and TEA (55 mmol) in 50 mL DCM at room temperature.
The reaction mixture was stirred for 5 h at room temperature.
Water (25 mL) was added, and the organic layer was separated.
The aqueous phase was washed three times with 20 mL of DCM.
The organic extracts were combined and washed with brine, dried
over MgSO4, filtered, and evaporated under reduced pressure. The
obtained product 2 (Scheme 1) and TEA (105 mmol) were then dis-
solved in DCM (50 mL) and 1-(3-Aminopropyl)imidazole
(105 mmol) was added to the solution. The mixture was stirred
for 2–7 h at rt. Water (20 mL) was added to the reaction mixture,
separated and the organic phase was washed again with water
(2 ꢀ 20). The combined aqueous phases washed with 20 mL of
DCM. The organic extracts were then combined and washed with
brine, dried over MgSO4, filtered, and evaporated under reduced
pressure. The progress of the reaction was monitored using TLC
and gas chromatography–mass-spectrometry. The resulted com-
pounds (Fig. 2) were purified by flash column chromatography
O
O
OH
NH2
VPA (17)
SPD (18)
Figure 3. Chemical structure of valproic acid (VPA) and sec-butylpropylacetamide.
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

6
H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
using DCM/MeOH (95:5) as eluent. All compounds were fully char-
acterized by elemental analyses (C, H, N), 1H NMR, and GC/MS
spectra. Compounds 7–16 were obtained with yields ranging
between 65% and 82%.
156.32, 137.314, 129.16, 118.45, 67.41, 49.56, 43.10, 36.53, 31.72,
30.43, 26.05. Anal. Calcd for C13H23N3O2: C, 61.63; H, 9.15; N,
16.59. Found: C, 61.36; H, 9.19; N, 16.24.
4.4.4. 2-Ethylhexyl (3-(1H-imidazol-1-yl)propyl)carbamate (11)
This compound was prepared by following general procedure,
using 2-ethylhexanol (6.5 g, 50 mmol), CDI (55 mmol) and TEA
(55 mmol) in 50 mL DCM. The crude was purified by column chro-
matography with 95% DCM/MeOH as eluent, to afford 2-Ethylhexyl
(3-(1H-imidazol-1-yl)propyl)carbamate (11.1 g, 79%) as a colorless
viscous oil. MS-EI, m/z (%): 281. 1H NMR (300 MHz, CDCl3, d TMS):
0.80–1.00 (m, 6H), 1.25–1.40 (m, 6H), 1.45–1.62 (m, 2H), 1.65–1.80
(m, 1H), 1.95–2.05 (m, 2H), 3.08–3.24 (q, J = 6.4 Hz, 2H), 3.94–4.04
(m, 2H), 4.05–4.18 (t, J = 5.7 Hz, 2H), 4.70–4.86 (s, 1H), 6.91–6.97
(s, 1H), 7.03–7.09 (s, 1H), 7.46–7.53 (s, 1H). 13C NMR (75 MHz,
CDCl3) d 157.23, 137.01, 129.29, 121.70, 67.39, 44.30, 38.79,
31.55, 30.48, 28.81, 23.42, 22.93, 13.99, 10.84. Anal. Calcd for
4.4. 2-Propylpentyl (3-(1H-imidazol-1-yl)propyl)carbamate (7)
This compound was prepared by following general procedure,
using 2-n-Propyl-1-pentanol (6.5 g, 50 mmol), CDI (55 mmol) and
TEA (55 mmol) in 50 mL DCM. The crude was purified by column
chromatography with 95% DCM/MeOH as eluent, to afford 2-propy-
lpentyl (3-(1H-imidazol-1-yl)propyl)carbamate (10.5 g, 75%) as a yel-
low viscous oil. MS-EI, m/z (%): 281. 1H NMR (300 MHz, CDCl3, d
TMS): 0.80–0.90 (t, J = 6.8 Hz, 6H), 1.20–1.30 (m, 8H), 1.45–1.65
(m, 1H), 1.90–2.10 (m, 2H), 3.30–3.35 (m, 1H), 3.71–3.82 (m,
2H), 3.90–4.10 (m, 4H), 4.90–5.00 (s, 1H), 6.90–7.00 (s, 1H),
7.10–7.15 (s, 1H), 7.45–7.50 (s, 1H). 13C NMR (75 MHz, CDCl3) d
152.51, 132.25, 124.45, 114.04, 62.79, 48.66, 41.26, 39.43, 32.29,
28.64, 26.69, 14.98, 11.48. Anal. Calcd for C15H27N3O2: C, 64.02;
H, 9.67; N, 14.93. Found: C, 63.83; H, 9.77; N, 14.68.
C15H27N3O2: C, 64.02; H, 9.67; N, 11.37. Found: C, 63.86; H, 9.7;
N, 11.15.
4.4.5. Phenethyl (3-(1H-imidazol-1-yl)propyl)carbamate (12)
This compound was prepared by following general procedure,
using phenylethyl alcohol (6.1 g, 50 mmol), CDI (55 mmol) and
TEA (55 mmol) in 50 mL DCM. The crude was purified by column
chromatography with 95% DCM/MeOH as eluent, to afford phe-
nethyl (3-(1H-imidazol-1-yl)propyl)carbamate (10.5 g, 77%) as a
yellow viscous oil. MS-EI, m/z (%): 273. 1H NMR (300 MHz, CDCl3,
d TMS): 1.86–1.99 (m, 2H), 2.88–2.96 (t, J = 6.9 Hz, 3H), 3.08–3.18
(m, 2H), 3.87–3.98 (t, J = 7.0 Hz,2H), 4.23–4.31 (t, J = 7.0 Hz,2H),
5.34–5.45 (s, 1H), 6.88–6.92 (s, 1H), 7.18–7.23 (m, 3H), 7.25–7.31
(m, 2H), 7.40–7.45 (m, 2H), 7.45–7.50 (s, 1H). 13C NMR (75 MHz,
CDCl3) d 158.22, 137.95, 137.08, 129.22, 128.89, 128.43, 126.48,
118.89, 65.23, 44.22, 37.8, 35.46, 31.37. Anal. Calcd for
4.4.1. 3-Methyl-2-propylpentyl (3-(1H-imidazol-1-yl)
propyl)carbamate (8)
3-Methyl-2-propyl-1-pentanol was synthesized by following
the literature procedure.22 Compound (8) was prepared by follow-
ing general procedure, using 3-Methyl-2-propyl-1-pentanol (7.2 g,
50 mmol), CDI (55 mmol) and TEA (55 mmol) in 50 mL DCM. The
crude was purified by column chromatography with 95% DCM/
MeOH as eluent, to afford 3-Methyl-2-propylpentyl(3-(1H-imida-
zol-1-yl)propyl)carbamate (10.4 g, 71%) as a colorless oil. MS-EI,
m/z (%): 295. 1H NMR (300 MHz, CDCl3, d TMS): 0.79–0.92 (m,
9H), 1.06–1.20 (m, 2H), 1.22–1.52 (m, 6H), 1.52–1.66 (m, 2H),
1.92–2.07 (m, 2H), 3.07–3.23 (m, 2H), 3.92–4.07 (m, 2H), 4.70–
4.88 (s, 1H), 6.88–6.9 (s, 1H), 7.04–7.08 (s, 1H), 7.45–7.5 (s, 1H).
13C NMR (75 MHz, CDCl3) d 154.01, 133.75, 125.95, 115.54, 64.29,
50.16, 42.76, 40.93, 33.79, 30.14, 26.69, 14.98, 12.98. Anal. Calcd
for C16H29N3O2: C, 65.05; H, 9.89; N, 14.22. Found: C, 64.9; H,
9.7; N, 14.07.
C15H19N3O2: C, 65.91; H, 7.01; N, 15.37. Found: C, 65.58; H, 6.7;
N, 15.52.
4.4.6. 2,4,4-Trimethylpentyl (3-(1H-imidazol-1-yl)
propyl)carbamate (13)
This compound was prepared by following general procedure,
using 2,4,4-trimethyl-1-pentanol (6.5 g, 50 mmol), CDI (55 mmol)
and TEA (55 mmol) in 50 mL DCM. The crude was purified by col-
umn chromatography with 95% DCM/MeOH as eluent, to afford
4.4.2. 2-Ethylbutyl (3-(1H-imidazol-1-yl)propyl)carbamate (9)
This compound was prepared by following general procedure,
using 2-ethyl-1-butanol (5.1 g, 50 mmol), CDI (55 mmol) and TEA
(55 mmol) in 50 mL DCM. The crude was purified by column chro-
matography with 95% DCM/MeOH as eluent, to afford 2-Ethylbutyl
(3-(1H-imidazol-1-yl)propyl)carbamate (10.3 g, 82%) as a yellow
viscous oil. MS-EI, m/z (%): 253. 1H NMR (300 MHz, CDCl3, d
TMS): 0.83–0.93 (t, J = 7.4 Hz, 6H), 1.27–1.39 (m, 4H), 1.41–1.55
(m, 1H), 1.94–2.07 (m, 2H), 3.11–3.23 (m, 2H), 3.45–3.59 (s, 1H),
3.90–4.10 (m, 2H), 4.86–4.97 (s, 1H), 6.97–6.99 (s, 1H), 7.06–7.09
(s, 1H), 7.62–7.70 (s, 1H). 13C NMR (75 MHz, CDCl3) d 154.56,
134.47, 126.45, 116.33, 64.53, 41.86, 37.96, 35.35, 28.96, 20.61,
8.43. Anal. Calcd for C13H23N3O2: C, 61.63; H, 9.15; N, 16.59. Found:
C, 61.53; H, 9.17; N, 16.18.
2,4,4-Trimethylpentyl
(10.8 g, 77%) as a yellow viscous oil. MS-EI, m/z (%): 281. 1H NMR
(300 MHz, CDCl3, TMS): 0.88–0.92 (s, 12H), 0.93–0.98 (d,
(3-(1H-imidazol-1-yl)propyl)carbamate
d
J = 6.7 Hz, 3H), 0.97–1.07 (dd, J = 26.7 Hz, 1H), 1.21–1.29 (dd,
J = 14.1 Hz, 1H), 1.75–1.88 (m, 1H), 1.95–2.06 (m, 2H), 3.11–3.25
(m, 2H), 3.71–3.95 (m, 2H), 3.96–4.04 (t, J = 7.0 Hz, 2H), 4.69–
4.82 (s, 1H), 6.92–6.95 (s, 1H), 7.05–7.07 (s, 1H), 7.49–7.52 (s,
1H). 13C NMR (75 MHz, CDCl3) d 152.28, 132.31, 124.81, 114.02,
66.20, 42.33, 41.09, 39.52, 33.2, 26.81, 26.09, 24.50, 15.04. Anal.
Calcd for C15H27N3O2: C, 64.02; H, 9.67; N, 14.93. Found: C,
63.67; H, 9.41; N, 14.54.
4.4.3. 3,3-Dimethylbutyl (3-(1H-imidazol-1-yl)
4.4.7. 3-Methylpentan-2-yl (3-(1H-imidazol-1-yl)
propyl)carbamate (10)
propyl)carbamate (14)
This compound was prepared by following general procedure,
using 3,3-dimethyl-1-butanol (5.1 g, 50 mmol), CDI (55 mmol)
and TEA (55 mmol) in 50 mL DCM. The crude was purified by col-
umn chromatography with 95% DCM/MeOH as eluent, to afford
This compound was prepared by following general procedure,
using 3-methyl-2-pentanol (5.1 g, 50 mmol), CDI (55 mmol) and
TEA (55 mmol) in 50 mL DCM. The crude was purified by column
chromatography with 95% DCM/MeOH as eluent, to afford 3-
methylpentan-2-yl (3-(1H-imidazol-1-yl)propyl)carbamate (8.2 g,
65%) as a yellow viscous oil. MS-EI, m/z (%): 253. 1H NMR
(300 MHz, CDCl3, d TMS): 0.83–0.92 (m, 6H), 1.07–1.20 (m, 4H),
1.37–1.49 (m, 1H), 1.94–2.05 (m, 2H), 3.10–3.25 (m, 2H), 3.11–
3.24 (m, 2H), 3.96–4.04 (m, 1H), 4.65–4.79 (s, 1H), 6.92–6.96 (s,
1H), 7.05–7.08 (s, 1H), 7.47–7.51 (s, 1H). 13C NMR (75 MHz, CDCl3)
3,3-Dimethylbutyl
(3-(1H-imidazol-1-yl)propyl)carbamate
(10.2 g, 81%) as a yellow viscous oil. MS-EI, m/z (%): 253. 1H NMR
(300 MHz, CDCl3, d TMS): 0.90–0.96 (s, 9H), 1.49–1.57 (m, 2H),
1.95–2.05 (m, 2H), 3.08–3.24 (m, 2H), 3.94–4.04 (m, 2H), 4.05–
4.18 (t, J = 7.0 Hz, 2H), 4.70–4.86 (s, 1H), 6.91–6.97 (s, 1H), 7.03–
7.09 (s, 1H), 7.46–7.53 (s, 1H). 13C NMR (75 MHz, CDCl3) d
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
7
d 155.60, 137.31, 129.16, 118.45, 75.80, 49.56, 43.08, 35.38, 26.91,
25.95, 18.18, 15.96, 11.97. Anal. Calcd for C13H23N3O2: C, 61.63; H,
9.15; N, 16.59. Found: C, 61.32; H, 9.03; N, 16.96.
all of the animals were considered impaired. The TD50 and the 95%
confidence intervals were calculated by FORTRAN probit analysis.
The PIs were calculated by dividing the TD50 by the ED50
.
4.4.8. Neopentyl (3-(1H-imidazol-1-yl)propyl)carbamate (15)
This compound was prepared by following general procedure,
using neopentyl alcohol (4.4 g, 50 mmol), CDI (55 mmol) and TEA
(55 mmol) in 50 mL DCM. The crude was purified by column chro-
matography with 95% DCM/MeOH as eluent, to afford Neopentyl
(3-(1H-imidazol-1-yl)propyl)carbamate (7.8 g, 65%) as a colorless
viscous oil. MS-EI, m/z (%): 239. 1H NMR (300 MHz, CDCl3, d
TMS): 0.88–0.96 (s, 9H), 1.95–2.07 (m, 2H), 3.11–3.27 (m, 2H),
3.73–3.80 (s, 2H), 3.96–4.05 (t, J = 7 Hz, 2H), 4.74–4.89 (s, 1H),
6.90–6.95 (s, 1H), 7.03–7.09 (s, 1H), 7.48–7.54 (s, 1H). 13C NMR
(75 MHz, CDCl3) d 156.32, 137.31, 129.16, 118.45, 70.82, 49.56,
43.08, 31.68, 26.01, 25.95. Anal. Calcd for C12H21N3O2: C, 60.23;
H, 8.84; N, 17.56. Found: C, 59.89; H, 8.72; N, 17.37.
4.8. Calculation of ClogP
ClogP was calculated by means of ChemDraw-Ultra Software 8.
Acknowledgments
This work is abstracted from the PhD thesis of Mr. Hafiz Mawasi
in a partial fulfillment for the requirements of a PhD degree at The
Hebrew University of Jerusalem.
The authors thank Dr. Tracy Chen, Dr. John Kehne and Dr.
Shamsi Raeissi of the NIH–NINDS-Anticonvulsant Screening Pro-
gram (ASP) as well as Prof. H. Steve White from the University of
Utah for testing the compounds in their anticonvulsant program
and Dr. Aviva Friedman-Ezra from the Hebrew University for her
skilfull assistance with the 13C NMR analysis.
4.4.9. Hexan-3-yl (3-(1H-imidazol-1-yl)propyl)carbamate (16)
This compound was prepared by following general procedure,
using 3-hexanol (5.1 g, 50 mmol), CDI (55 mmol) and TEA
(55 mmol) in 50 mL DCM. The crude was purified by column chro-
matography with 95% DCM/MeOH as eluent, to afford hexan-3-yl
(3-(1H-imidazol-1-yl)propyl)carbamate (8.2 g, 65%) as a yellow
viscous oil. MS-EI, m/z (%): 253. 1H NMR (300 MHz, CDCl3, d
TMS): 0.84–0.96 (m, 6H), 1.24–1.39 (m, 2H), 1.43–1.62 (m, 4H),
1.94–2.05 (m, 2H), 3.12–3.24 (m, 2H), 3.94–4.03 (t, J = 6.5 Hz,2H),
3.93–4.05 (t, J = 7.0 Hz, 1H), 4.70–4.80 (s, 1H), 6.90–6.96 (s, 1H),
7.03–7.10 (s, 1H), 7.43–7.52 (s, 1H). 13C NMR (75 MHz, CDCl3) d
156.95, 137.05, 129.47, 118.83, 76.044, 44.34, 37.98, 31.69, 27.22,
18.57, 14.03, 9.57, 8.60. Anal. Calcd for C13H23N3O2: C, 61.63; H,
9.15; N, 16.59. Found: C, 59.19; H, 8.72; N, 17.37.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2016.07.018.
References and notes
1. Fisher, R. S.; Acevedo, C.; Arzimanoglou, A.; Bogacz, A.; Cross, J. H.; Elger, C. E.;
Engel, J., Jr.; Forsgren, L.; French, J. A.; Glynn, M.; Hesdorffer, D. C.; Lee, B. I.;
Mathern, G. W.; Moshé, S. L.; Perucca, E.; Scheffer, I. E.; Tomson, T.; Watanabe,
M.; Wiebe, S. Epilepsia 2014, 55, 475–482.
2. Téllez-Zenteno, J. F.; Hernández-Ronquillo, L.; Buckley, S.; Zahagun, R.; Rizvi, S.
Epilepsia 2014, 55, 829–834.
3. Nardi, D.; Tajana, A.; Leonardi, A.; Pennini, R.; Portioli, F.; Magistretti, M. J.;
Subissi, A. J. Med. Chem. 1981, 24, 727–731.
4.5. Biological testing/anticonvulsant activity
4. Walker, K. A.; Wallach, M. B.; Hirschfeld, D. R. J. Med. Chem. 1981, 24, 67–74.
5. Testa, B.; Bertin, D. Denzimol. In New Anticonvulsant Drugs; Meldrum, B. S.,
Porter, R. J., Eds.; John Libbey, 1986; pp 85–102.
6. Buhles, W. C., Jr; Wallach, M. B.; Chaplin, M. D.; Treiman, D. M. Nafimidone. In
New Anticonvulsant Drugs; Meldrum, B. S., Porter, R. J., Eds.; John Libbey, 1986;
pp 203–214.
7. Robertson, D. W.; Krushinski, J. H.; Beedle, E. E.; Leander, J. D.; Wong, D. T.;
Rathbun, R. C. J. Med. Chem. 1986, 29, 1577–1586.
8. Patsalos, P. N.; Shorvon, S. D.; Elyas, A. A.; Smith, G. J. Neurol. Neurosurg.
Psychiatry 1985, 48, 374–377.
The evaluation of anticonvulsant activity in the MES, scMet,
pilocarpine-induced status test and 6 Hz test, and the determina-
tion of neurotoxicity in the rotorod test were performed at the
National Institute of Health (NIH) Epilepsy Branch as a part of
the Anticonvulsant Drug Development Program according to the
protocols described.23,24
9. Treiman, D. M.; Wilensky, A. J.; Ben-Menachem, E.; Ojemann, L.; Yerby, M.;
Barber, K. O.; McCormick, K. B.; Cereghino, J. J.; White, B. G.; Swisher, K.
Epilepsia 1985, 26, 607–611.
4.6. Preparation of the compounds for testing
10. Treiman, D. M.; Ben-Menachem, E. Epilepsia 1987, 28, 699–705.
11. Fisher, R.; Blum, D. Epilepsia 1995, 36, S105–114.
The tested compounds were suspended in 0.5% methylcellulose
and administered intraperitoneally (ip) to adult male CF no. 1
albino mice (18–25 g) in a volume of 0.01 mL/g body weight and
(b) orally to adult male Sprague–Dawley albino rats (100–150 g)
in a volume of 0.04 mL per 10 g of body weight. The pentylenete-
trazol solution at convulsing dose was prepared by sufficient disso-
lution of pentylenetetrazol in 0.9% saline to make 0.85% solution
for administration to mice and 2.82% solution for administration
to rats.
12. Ludwig, B. J.; Piech, E. C. J. Am. Chem. Soc. 1951, 37, 5779–5781.
13. Ludwig, B. J.; Powell, E. C.; Berger, F. M. J. Med. Chem. 1968, 12, 462–474.
14. Close, W. J.; Spielman, M. A. Anticonvulsant drugs. In Medicinal Chemistry;
Hartung, W. H., Ed.; John Wiley and Sons: New York, 1961; pp 143–150.
15. Daleva, L.; Nikolova, M. Farmatsiya (Moscow) 1964, 14, 13–17.
16. Nikolova, M. Farmatsiya (Moscow) 1965, 15, 32ꢁ39.
17. Frey, H. H.; Bartels, I. Epilepsy Res. 1997, 27, 151–164.
18. Jensen, P. K. Epilepsia 1993, 34, S25–S29.
19. Pellock, J. M.; Perhach, J. L.; Sofia, R. D. Felbamate. In Antiepileptic Drugs; Levy,
R. H., Mattson, R. H., Meldrum, B. S., Perucca, E., Eds., 5th ed.; Lippincott
Williams & Wilkins Publishers: New York, 2002; pp 301–320.
20. Thakkar, K.; Billa, G. T.; Rane, J.; Chudasama, H.; Goswami, S.; Shah, R. Expert
Rev. Neurother. 2015, 15, 1373–1375.
4.7. Determination of the median effective dose (ED50) and the
21. Bialer, M.; Johannessen, S. I.; Levy, R. H.; Perucca, E.; Tomson, T.; White, H. S.
Epilepsy Res. 2009, 83, 1–43.
median neurotoxic dose (TD50
)
22. Hen, N.; Bialer, M.; Yagen, B. J. Med. Chem. 2012, 55, 2835–2845.
23. White, H. S.; Woodhead, J. H.; Wilcox, K. S.; Stables, J. P.; Kupferberg, H. J.; Wolf,
H. H. Discovery and Preclinical Development of Antiepileptic Drugs. In
Antiepileptic Drugs; Levy, R. H., Mattson, R. H., Meldrum, B. S., Perucca, E.,
Eds., 5th ed., 2002; pp 36–48.
24. Smith, M.; Wilcox, K. S.; White, H. S. Neurotherapeutics 2007, 4, 12–17.
25. Rogawski, M. A.; Loscher, W. Nat. Rev. Neurosci. 2004, 5, 553–564.
26. Bialer, M.; White, H. S. Nat. Rev. Drug Disc. 2010, 9, 68–83.
27. Palaty, J.; Abbott, F. S. J. Med. Chem. 1995, 38, 3398–3406.
28. Elmazar, M. M.; Hauck, R. S.; Nau, H. J. Pharm. Sci. 1993, 82, 1255–1258.
29. Abbott, F. S.; Acheampong, A. A. Neuropharmacology 1988, 27, 287–294.
30. Marchi, N.; Betto, G.; Fazio, V.; Fan, Q.; Ghosh, C.; Machado, A.; Janigro, D.
Epilepsia 2009, 50, 664–677.
For the determination of the ED50 by the respective anticonvul-
sant procedure, doses of the tested compounds were varied until a
minimum of 3–4 points was established between the dose level of
0% protection and 100% protection. These data were subjected to
the FORTRAN probit analysis program, and the ED50 and 95% con-
fidence intervals were calculated. The TD50 was determined by
varying the dose of the tested compounds until four points were
established between the dose level that induced no signs of mini-
mal motor impairment in any of the animals and the dose at which
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018

8
H. Mawasi et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
31. Bialer, M.; White, H. S. Nat. Rev. Drug Disc. 2010, 9, 68–83.
32. Loscher, W.; Klitgaard, E.; Twyman, R. E.; Schmidt, D. Nat. Rev. Drug Disc. 2013,
12, 757–776.
38. Perucca, E.; French, J.; Bialer, M. Lancet Neurol. 2007, 6, 793–804.
39. White, H. S.; Alex, A. B.; Pollock, A.; Hen, N.; Shekh-Ahmed, T.; Wilcox, K. S.;
McDonough, J. H.; Stables, J. P.; Kaufmann, D.; Yagen, B.; Bialer, M. Epilepsia
2012, 53, 134–146.
33. Perucca, E. CNS Drugs 2011, 25, 907–912.
34. Schmidt, D. Epilepsy Behav. 2011, 21, 342–343.
35. Bialer, M. Expert Opin. Invest. Drugs 2006, 15, 637–647.
36. Rogwaski, M. Epilepsy Res. 2006, 69, 273–284.
37. Bialer, M.; Yagen, B. Neurotherapeutics 2007, 4, 130–137.
40. Shekh-Ahmad, T.; Mawasi, H.; McDonough, J. H.; Yagen, B.; Bialer, M. Epilepsy
Behav. 2015, 15, 160–162.
41. Agranat, I.; Wainsctein, S. R.; Zusman, E. Z. Nat. Rev Drug Disc. 2012, 11, 972–
973.
Please cite this article in press as: Mawasi, H.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.07.018