Synthesis and anticonvulsant activity of aromatic tetramethylcyclopropanecarboxamide derivatives

Article abstract of DOI:10.1016/j.bmc.2008.03.051

As part of our ongoing research on potential new antiepileptic drugs (AEDs), a series of tetramethylcyclopropanecarboxamide derivatives containing benzene ring were designed, synthesized, and evaluated for anticonvulsant activities in the murine maximal electroshock (MES) and subcutaneous pentylenetetrazole (scMet) seizure tests. The most potent compound emerging from this study was N-(2,2,3,3-tetramethylcyclopropanecarboxamide)-p-phenyl-sulfonamide (21), possessing an ED₅₀ value of 26 mg/kg in the rat-MES test and a remarkable PI (PI = TD₅₀/ED₅₀) value above 19. The better anticonvulsant potency of compound 21 and its wider safety margin compared to valproic acid (VPA) and zonisamide make it a potential candidate to become a new AED second-generation to VPA.

Full text of DOI:10.1016/j.bmc.2008.03.051

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 6297–6305
Synthesis and anticonvulsant activity of aromatic
tetramethylcyclopropanecarboxamide derivatives
Jakob Avi Shimshoni,a Meir Bialera,b and Boris Yagenb,c,
*
aDepartment of Pharmaceutics, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
bDavid R. Bloom Center for Pharmacy, School of Pharmacy, Faculty of Medicine,
The Hebrew University of Jerusalem, Jerusalem, Israel
cDepartment of Medicinal Chemistry and Natural Products, School of Pharmacy, Faculty of Medicine,
The Hebrew University of Jerusalem, Jerusalem 91120, Israel
Received 22 November 2007; revised 12 March 2008; accepted 20 March 2008
Available online 23 March 2008
Abstract—As part of our ongoing research on potential new antiepileptic drugs (AEDs), a series of tetramethylcyclopropanecarb-
oxamide derivatives containing benzene ring were designed, synthesized, and evaluated for anticonvulsant activities in the murine
maximal electroshock (MES) and subcutaneous pentylenetetrazole (scMet) seizure tests. The most potent compound emerging from
this study was N-(2,2,3,3-tetramethylcyclopropanecarboxamide)-p-phenyl-sulfonamide (21), possessing an ED50 value of 26 mg/kg
in the rat-MES test and a remarkable PI (PI = TD50/ED50) value above 19. The better anticonvulsant potency of compound 21 and
its wider safety margin compared to valproic acid (VPA) and zonisamide make it a potential candidate to become a new AED sec-
ond-generation to VPA.
Ó 2008 Published by Elsevier Ltd.
1. Introduction
Epilepsy is one of the most common neurological condi-
COOH
COOH
tions, occurring in about 1% of the global population.1
Valproic acid (VPA, Fig. 1) is a major antiepileptic drug
(AED) in the treatment of epilepsy and is also approved
for the treatment of bipolar disorder, migraine prophy-
laxis, and neuropathic pain.1–4 Nevertheless, VPA’s clin-
ical use is limited by two life-threatening side effects:
teratogenicity and hepatotoxicity.5–9 Since several of
the currently available AEDs have been associated with
severe side effects and fail to control seizures in about
30% of epileptic patients, there is a substantial need
for the development of new, more effective and less toxic
AEDs.10
VPA (1)
TMCA (2)
CONH2
CONHCH3
MTMCD (4)
TMCD (3)
Many analogues and derivatives of VPA were synthe-
sized in an attempt to find a superior compound that
CONHOCH3
CONHCONH2
OM-TMCD (5)
TMCU (6)
Keywords: 2,2,3,3-Tetramethylcyclopropanecarboxylic acid; Valproic
acid; Phenyl-alkyl-amines; Sulfonamides; Anticonvulsants; Structure–
activity relationships; Maximal electroshock seizure test; Subcutaneous
pentylenetetrazole seizure test.
Figure 1. Chemical structures of VPA, TMCA, TMCD, MTMCD,
OM-TMCD, and TMCU.
*
would retain the anticonvulsant activity correlated with
the basic structure of VPA but would not cause the
Corresponding author. Tel.: +972 2 6758606; fax: +972 2 6757246;
e-mail: yagen@cc.huji.ac.il
0968-0896/$ - see front matter Ó 2008 Published by Elsevier Ltd.
doi:10.1016/j.bmc.2008.03.051

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adverse effects associated with VPA use.11,12 2,2,3,3-
Tetramethylcyclopropanecarboxylic acid (TMCA, 2,
Fig. 1) is a cyclic analogue of VPA displaying weak anti-
convulsant activity. Unlike VPA, the presence of two
quaternary carbons in the TMCA structure at the b-po-
sition to the carbonyl group prevents the formation of
hepatotoxic metabolites with a terminal double bond,
analogous to 4-ene-VPA.8,9 As part of our ongoing re-
search program we have synthesized and evaluated the
anticonvulsant activity of several coupling products of
TMCA with urea and its N-alkyl derivatives as well as
thiourea and iminourea.13 The most active compound
in this series was 2,2,3,3-tetramethylcyclopropanecar-
bonylurea (TMCU, 6, Fig. 1), being 17 and 7 times more
potent than VPA in the rat maximal electroshock seizure
(MES) and the subcutaneous pentylenetetrazole seizure
(scMet) tests, respectively.
In the current study, we explored the anticonvulsant
activity and safety margin of a series of TMCD deriva-
tives containing benzene ring in their structure, in the
MES and scMet tests, in order to investigate if some
of these compounds might become new AED
candidates.18,19
2. Results and discussion
2.1. Synthesis
TMCA served as the starting material for the synthesis
of all aromatic tetramethylcyclopropanecarboxamide
derivatives (2, Scheme 1). It was converted by thionyl-
chloride to the corresponding acyl chloride (TMC-Cl)
by a method described in the literature.20 The com-
pounds presented in Table 1, except 21–23, were synthe-
sized by coupling at room temperature of TMC-Cl with
the suitable amines in dichloromethane.21 The products
were purified by crystallization from ethylacetate/petro-
leum ether. Their structures were identified by 1H NMR
and their purity established by thin-layer chromatogra-
phy and elemental analyses.
In the early seventies, Bentoit-Guyod et al., studied
the anticonvulsant structure–activity relationship
(SAR) of a large series of aromatic VPA amide
derivatives.14,15 Some of the compounds (e.g., di-n-
propylacetyl-(2-chloro-5-trifluoromethyl)-anilide), dem-
onstrated remarkable antipyretic and analgesic proper-
ties, although none of them showed superior
anticonvulsant activity and safety margin compared
to VPA. Recently, Netzeva et al. showed that an
improvement of VPA’s pharmacological profile can
be achieved by coupling VPA to certain aromatic ami-
no alkanes.16 An extensive SAR of various aromatic
and heteroaromatic sulfonamide derivatives of VPA
demonstrated the influence of the sulfonamide group
on the anticonvulsant activity of these VPA deriva-
tives.17 Zonisamide and acetazolamide are currently
used AEDs, containing a sulfonamide group in their
structure.1
Compounds 21–23 were prepared by coupling at room
temperature TMC-Cl with the suitable para amino sul-
fanylamides in acetone. Subsequently, the product was
purified and identified as described above.
2.2. Pharmacology
Since VPA has multiple mechanisms of action and the
specific mechanism primarily responsible for the antiepi-
leptic activity in patients is still unknown, a mechanistic
approach to develop new second-generation VPA drugs
a
b
COOH
COCl
CONHR
2
7-23
7 R= C6H5
16 R= CH2C6H4(2-Cl)
8 R= CH2C6H5
17 R= CH2C6H4(4-F)
9 R= CH2CH2C6H5
18 R= CONHC6H5
10 R= CH2CH2CH2C6H5
11 R= CH(CH3)C6H5
19 R= CH2CH2(1H-indole)
20 R= C6H2(3-chloro,4,6- SO2NH2)
21 R= C6H4(4-SO2NH2)
22 R= CH2C6H4(4-SO2NH2)
23 R= CH2CH2C6H4(4-SO2NH2)
12 R= CH2CH(CH3)C6H5
13 R= N-(CH3)CH(CH3)CH(OH)C6H5
14 R= CH(CH3)CH2OC6H3(1,5-dimethyl)
15 R= C6H4(4-acetyl)
Scheme 1. Synthetic route for aromatic TMCD derivatives. Reagents and conditions: (a) SOCl2, dichloromethane, rt, 8 h; (b) for compounds 7–21
and 23, dichloromethane, suitable amines, triethylamine, rt, 2–12 h; for compound 22, acetone, benzenesulfonamide, pyridine, rt, 12 h.

J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
6299
Table 1. Anticonvulsant activity and neurotoxicity of compounds 7–23 in the MES model following ip administration to micea
Compound
Dose (mg/kg)
Times after drug administration
Tox.b
0.5 h
2 h
4 h
CONH
c
7
300
—
NTd
—
—
—
—
—
—
3/4
3/4
1/4
—
CONHCH2
8
300
300
300
300
300
1/1
—
—
—
—
NT
NT
NT
NT
NT
CONHCH2CH2
9
CONHCH2CH2CH2
10
11
12
CONHCH
CH3
3/4
2/4
CONHCH2CH
CH3
CH3
OH
CONCHCH
CH3
13
300
—
NT
—
3/4
H3C
CH3
CONHCHCH2O
14
15
16
300
300
300
—
—
—
NT
NT
NT
—
1/1
—
—
—
—
H3C
CONH
COCH3
Cl
CONHCH2
(continued on next page)

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J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
Table 1 (continued)
Compound
Dose (mg/kg)
Times after drug administration
Tox.b
0.5 h
2 h
4 h
CONHCH2
F
17
18
19
20
21
22
23
300
—
NT
—
—
CONHCONH
300
300
300
100
100
300
—
—
—
—
—
—
NT
NT
NT
3/3
—
—
—
2/3
1/3
—
—
—
—
—
—
—
CONHCH2CH2
N
H
Cl
CONH
SO2NH2
SO2NH2
CONH
SO2NH2
CONHCH2
NHCH2CH2
SO2NH2
1/3
SO2NH2
NT
a Anticonvulsant activity expressed as the ratio between the number of animals protected and the number of animals tested.
b Toxicity.
c Not active.
d Not tested.
might be impracticable. Current development of new
CNS-active VPA derivatives and analogues is based on
pharmacokinetic- or pharmacodynamic-based structural
modifications of the VPA molecule utilizing anticonvul-
sant animal models that have gained a reputation for their
predictability since the discovery of phenytoin.22,23
Rational design of second-generation to VPA molecules
is applicable to the development of non-teratogenic and
non-hepatotoxic follow-up compounds to VPA. The
amide derivatives of TMCA are attractive lead com-
pounds for the development of non-teratogenic and
non-hepatotoxic second-generation to VPA CNS drugs,
since no terminal double bond could be formed during
the metabolism of these molecules. Recently, four new po-
tent anticonvulsant amide derivatives of TMCA, namely
2,2,3,3-tetramethylcyclopropanecarboxamide (TMCD,
3), N-methyl-TMCD (MTMCD, 4), N-methoxy-TMCD
(OM-TMCD, 5), and TMCU (6) have been synthesized
in our laboratory (Fig. 1).13,21 TMCD was active only in
the scMet test, while, MTMCD, OM-TMCD, and
TMCU showed better anticonvulsant potency than
VPA in the MES and scMet animal models tested along
with improved protective indexes.13,21 In rats, TMCU
emerged as the most potent compound in the MES test
(ED50 = 29 mg/kg) with a protective-index (PI = TD50/
ED50) 12 times larger than that of VPA. In the scMet test
OM-TMCD exhibited the highest potency and safety
margin (ED50 = 35 mg/kg and PI = 10).13

J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
6301
In this study, we synthesized a series of TMCD aromatic
derivatives with various branched and non-branched
alkyl and alkoxy groups attached to a phenyl ring with
various substituents (Scheme 1 and Table 1).
showed enhanced anticonvulsant activity in the scMet
test.16
Some commercially available drugs that possess anti-
convulsant activity in the MES and scMet tests, are uti-
lized clinically outside of epilepsy.24,25 Mexiletine, 1-
(2,6-dimethylphenoxy)-2-propanolamine used in the
treatment of arrhythmias, showed potent anticonvulsant
activity in the mice MES test (ED50 = 10 mg/kg).25
However, coupling mexiletine with TMCA leads to an
amide (14) with a significantly reduced anticonvulsant
activity (Tables 1 and 2). Although, TMCU is very ac-
tive in the MES and scMet tests,13 the coupling product
between phenylurea and TMCA (compound 18) failed
to yield a potent TMCD aromatic derivative (Tables 1
and 2). Ortho-chloro and para-fluoro derivatives of
compound 8, yielded compounds 16 and 17 that
exhibited reduced anticonvulsant activity compared to
8 (Tables 1 and 2).
As shown in Table 1, 2,2,3,3-tetramethylcyclo-
propanecarbonylbenzylamide (8) and 2,2,3,3-tetrameth-
ylcyclopropanecarbonyl-(4-acetylphenyl)-amide (15) were
active in the mice MES test only at the highest dose
tested (300 mg/kg). In the mice scMet test compound 8
and 2,2,3,3-tetramethylcyclopropanecarbonylphenylethyl-
amide (9) provided full protection against the clonic sei-
zures only at 300 mg/kg (Table 2). Netzeva et al. showed
that the VPA analogues of both compounds 15 and 9
displayed remarkable anticonvulsant activity in the mice
scMet test.16 Thus, replacing the VPA moiety with
TMCA in these derivatives, resulted in a loss of activity
in the scMet test (Table 2). Similarly, valproylbenzyla-
mide, the VPA analogue of 8, previously synthesized
in our laboratory, displayed excellent anticonvulsant
activity in the scMet test with 50% of the animals pro-
tected at 100 mg/kg, whereas compound 8 demonstrated
a significant drop in the anticonvulsant activity in the
scMet test (Table 2). The same phenomenon was also
observed for 2,2,3,3-tetramethylcyclopropanecarbonyl-
(2-methyl-2-phenylethyl)-amide (12), in which the
replacement of the VPA moiety with TMCA, resulted
in a diminished anticonvulsant activity in the scMet test
(Table 2).16
Several currently available AEDs (e.g., acetazolamide,
zonisamide, and topiramate) contain sulfonamide or
sulfamate groups in their chemical structures
(Fig. 2).17 Masereel et al. extensively explored the SAR
of numerous aromatic and heterocyclic sulfonamide
derivatives of the corresponding amide of VPA, valpro-
mide (VPD), aiming to develop new VPA analogous and
derivatives with improved anticonvulsant profile.17 They
found that 5-valproylamide-1,3,4-thiadiazole-2-sulfon-
amide, displayed excellent anticonvulsant activity in
the mice MES test with improved PI-index in compari-
son to VPA.17 Another aromatic sulfonamide derivative
of VPD, 4-(valproylamide)-benzyl sulfonamide (the
VPA analogue of compound 22) has been found to be
a potent anticonvulsant in mice (MES-ED50 = 16 mg/
kg, PI > 19).26
Branching or increasing of the number of carbon atoms
beyond two in the alkyl chain connecting the phenyl
with the amine group (e.g. Compounds 10–13) resulted
in lack of activity in the MES test (Table 1). However,
the corresponding VPA analogues reported by Netzeva,
Table 2. Anticonvulsant activity and neurotoxicity of compounds 7–
23 in the scMet model following ip administration to micea
The compound N-(2,2,3,3-tetramethylcyclopropane-
carboxamide)-p-phenylsulfonamide (21) displayed excel-
lent anticonvulsant activity in the MES test at 100 mg/
kg and a wide safety margin (Table 1), however no anti-
Compound
Dose
(mg/kg)
Times after
drug
administration
Tox.b
0.5 h
4 h
c
N
N
7
8
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
3/4
1/4
—
3/4
2/4
3/4
—
—
—
—
—
—
—
—
—
—
1/1
1/1
—
—
—
—
—
—
—
—
—
—
—
—
—
—
9
SO2NH2
CH3CONH
10
11
12
13
14
15
16
17
18
19
20
21
22
23
S
Acetazolamide
SO3NH2
O
CH2SO2NH2
O
N
O
O
O
O
Topiramate
Zonisamide
a Anticonvulsant activity expressed as the ratio between the number of
animals protected and the number of animals tested.
Figure 2. Chemical structures of clinically approved AEDs containing
sulfonamide (acetazolamide and zonisamide) and sulfamate (topira-
mate) in their molecule.
b Toxicity.
c Not active.

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J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
convulsant activity was observed in the scMet test (Ta-
ble 2). This pharmacological profile of compound 21,
namely potent anticonvulsant activity in the MES test
and lack of activity in the scMet test, is shared by zon-
isamide (ZNS) and topiramate (TPM), two widely used
AEDs containing sulfonamide (ZNS) and sulfamate
(TPM) in their chemical structure (Fig. 2).22,27 The
insertion of a spacer methylene (compound 22) or an
ethylene group (compound 23) between the amine and
the phenyl ring of 21 reduced the anticonvulsant activity
in the MES test. Consequently, in the series of TMCD
alkylamine-p-phenylsulfonamide derivatives the length
and the characteristics of the alkyl chain linking the phe-
nyl ring with the amine group might have a crucial influ-
ence on the anticonvulsant activity. An addition of
sulfonamide group at ortho and chlorine-atom at the
meta-position to the phenyl ring of 21, yielded com-
pound 20, which lacked the anticonvulsant activity in
the MES test (Table 1).
creased anticonvulsant activity compared to compound
21. Additional carbon in the spacer (compound 23)
caused remarkable drop in the activity compared to 21.
The anticonvulsant profile of compound 21 resembles
that of zonisamide, an AED with a sulfonamide group
in its structure. Compound 21 possesses a similar
MES-ED50 value to that of zonisamide, however its PI
value is two times larger than that of zonisamide.22
Thus, the better anticonvulsant potency of compound
21, compared to VPA, one of the most widely used
AEDs, coupled with its wider safety margin make it a
potential candidate to become a new AED that is a sec-
ond-generation drug to VPA.
4. Experimental
4.1. Materials and methods
We have found that compound 21, the most potent aro-
matic sulfonamide derivative of TMCD in the mice-
MES model (Table 1) was also very potent and non-
toxic in the rat-MES test (ED50 = 26 mg/kg, PI > 19)
(Table 3). However in the rat-scMet test, it was inactive
up to 100 mg/kg (Table 3). Compound 21 is far less toxic
than zonisamide with a PI value greater than 19, com-
pared to zonisamide’s PI value of 9 (Table 3).22 Conse-
quently, the higher anticonvulsant activity of compound
21 in the MES test as compared to VPA and its substan-
tially wider safety margin than VPA and zonisamide,
makes this aromatic sulfonamide derivative of the cyclic
analogue of VPA a potential candidate to become a new
AED.
All reagents were purchased from Sigma–Aldrich. Prod-
uct formation follow-up was performed by means of
TLC techniques. TLC analyses were performed on pre-
coated silica gel on aluminum sheets (Kieselgel 60 F254
Merck).
,
Chemical structure and purity of the newly synthesized
compounds were assessed by TLC, NMR, and elemental
analysis. Melting points were determined on a Buchi 530
capillary melting point apparatus. 1H NMR spectra
were recorded on a Varian Mercury-Series NMR 300
spectrometer. Chemical shifts (d scale) are reported in
parts per million (ppm) relative to the indicated refer-
ence. Coupling constants (J values) are given in Hertz
(Hz). Elemental analyses were performed on a 2400-2
Perkin-Elmer C, H, N analyzer.
3. Conclusions
C, H, N analyses of all newly synthesized compounds
had satisfactory results (within 0.4 of theoretical
values).
We have designed a series of TMCD aromatic deriva-
tives and evaluated their anticonvulsant profile in the
traditional animal models for anticonvulsant activity,
the MES and scMet models.23 In the MES model com-
pounds 8 and 15 were active at 300 mg/kg, whereas in
the scMet test only compounds 8 and 9 displayed anti-
convulsant activity at 300 mg/kg (Table 2).
4.2. General procedure A for the synthesis of aromatic
2,2,3,3-tetramethylcyclopropylcarboxamide derivatives
(7–19)
2,2,3,3-Tetramethylcyclopropanecarbonyl
chloride
The most potent compound in the MES test emerging
from this study was 21 (Tables 1–3). The one carbon
spacer in the side chain of compound 22 led to a de-
(TMC-Cl) (3 g, 9 mmol) dissolved in dry dichlorometh-
ane (30 mL) was slowly added to a stirred cooled solu-
tion of suitable amine (23 mmol) and triethylamine
Table 3. Anticonvulsant activity and toxicity of N-2,2,3,3-tetramethylcyclopropanecarboxamide)-p-phenylsulfonamide (21), VPA and zonisamide
following oral administration to rats
Compound
MESa (ED50, mg/kg)
scMetb (ED50, mg/kg)
Tox.c (TD50, mg/kg)
PI(MES)d
PI(scMet)
VPAe
Zonisamidee
21
485 (324–677)
21 (18–25)
26 (14–42)
646 (466–869)
>300
>100
784 (503–1176)
192 (155–242)
>500
1.6
9.1
1.2
—
—
>19
Values in parentheses are 95% confidence intervals determined by probit analysis.
a Maximal electroshock test.
b Subcutaneous pentylenetetrazol test.
c Toxicity.
d Protective index (TD50/ED50).
e Data taken from reference.25

J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
6303
(3.8 g, 38 mmol) in dry dichloromethane (100 mL).
After addition, the reaction mixture was stirred for 3 h
at room temperature. The organic solvent was then
evaporated under vacuum and the residue dissolved in
ethyl acetate (100 mL) and washed three times with
10 mL of distilled water. The organic fraction was dried
over MgSO4, filtered, and evaporated.
CH2), 3.141–3.235 (m, 1H: CH2), 3.581–3.672 (m, 1H:
CH), 5.26 (s, 1H: NH), 7.197–7.356 (m, 5H: H-Ar).
Anal. Calcd for C17H25NO: C, 78.72; H, 9.71; N, 5.39.
Found: C, 78.75; H, 9.82; N, 5.43.
4.2.7.
2,2,3,3-Tetramethylcyclopropanecarbonyl
(2-
hydroxy-1-methyl-2-phenyl-ethyl)-N-methylamide (13).
This compound was obtained as solid in 89% yield,
mp 89–90 °C. 1H NMR (300 MHz, CDCl3 d TMS):
1.005 (s, 1H: CH), 1.104–1.213 (m, 15H: CH3), 2.669
(s, 3H: CH3), 4.443 (s, 1H: CH), 4.835 (s, 1H: CH),
7.247–7.381 (m, 5H: H-Ar). Anal. Calcd for
C18H27NO2: C, 74.68; H, 9.41; N, 4.84. Found: C,
74.85; H, 9.67; N, 4.85.
The obtained products were purified by crystallization
using ethylacetate/petroleum ether mixture (1:3).
4.2.1. 2,2,3,3-Tetramethylcyclopropanecarbonyl phenyl
amide (7). This compound was obtained as solid in
75% yield, mp 150–151 °C. 1H NMR (300 MHz, CDCl3
d TMS): 0.994 (s, 1H: CH), 1.211–1.323 (d, J = 0.112,
12H: CH3), 7.06–7.492 (m, 5H: H-Ar), 7.201 (s, 1H:
NH). Anal. Calcd for C14H19NO: C, 77.38; H, 8.81;
N, 6.45. Found: C, 77.26; H, 9.05; N, 6.44.
4.2.8.
2,2,3,3-Tetramethylcyclopropanecarbonyl-1-
methyl-2-(2,6-dimethyl-phenoxy)-ethylamide (14). This
compound was obtained as solid in 78% yield, mp
128–130 °C. 1H NMR (300 MHz, CDCl3 d TMS):
0.870 (s, 1H: CH), 1.165–1.294 (dd, J = 0.008,
J0 = 0.03, 12H: CH3), 1.385–1.408 (d, J = 0.023, 3H:
CH3), 2.27 (s, 6H: CH3), 3.677–3.788 (dd, J = 0.01,
J0 = 0.013, 2H: CH2), 4.35 (m, 1H: CH), 5.833–5.859
(d, J = 0.026, 1H: NH), 6.897–7.017 (m, 3H: H-Ar).
Anal. Calcd for C19H29NO2: C, 75.21; H, 9.63; N,
4.62. Found: C, 75.25; H, 9.56; N, 4.70.
4.2.2. 2,2,3,3-Tetramethylcyclopropanecarbonyl benzyl
amide (8). This compound was obtained as solid in
1
89% yield, mp 88–89 °C. H NMR (300 MHz, CDCl3
d TMS): 0.841 (s, 1H: CH), 1.137–1.274 (d, J = 0.137,
12H: CH3), 4.416–4.397 (d, 2H: CH2), 5.674 (s, 1H:
NH), 7.228–7.345 (m, 5H: H-Ar). Anal. Calcd for
C15H21NO: C, 77.88; H, 9.14; N, 6.05. Found: C,
78.02; H, 9.16; N, 6.16.
4.2.9. 2,2,3,3-Tetramethylcyclopropanecarbonyl-(4-acet-
yl-phenyl)-amide (15). This compound was obtained as
solid in 79% yield, mp 194–195 °C. 1H NMR
(300 MHz, CDCl3 d TMS): 1.012 (s, 1H: CH), 1.222–
1.324 (d, J = 0.102, 12H: CH3), 2.565 (s, 3H: CH3),
7.426 (s, 1H: NH), 7.577–7.606 (d, J = 0.029, 2H: H-
Ar), 7.892–7.921 (d, J = 0.029, 2H: H-Ar). Anal. Calcd
for C16H21NO2: C, 74.09; H, 8.16; N, 5.40. Found: C,
74.36; H, 8.33; N, 5.45.
4.2.3. 2,2,3,3-Tetramethylcyclopropanecarbonyl phenyl-
ethylamide (9). This compound was obtained as solid in
84% yield, mp 81–82 °C. H NMR (300 MHz, CDCl3 d
TMS): 0.757 (s, 1H: CH), 1.123–1.241 (d, J = 0.118,
12H: CH3), 2.78–2.826 (t, 2H: CH2), 3.463–3.529 (t,
2H: CH2), 5.405 (s, 1H: NH), 7.188–7.334 (m, 5H).
Anal. Calcd for C16H23NO: C, 78.31; H, 9.45; N, 5.71.
Found: C, 78.38; H, 9.6; N, 5.72.
1
4.2.4. 2,2,3,3-Tetramethylcyclopropanecarbonyl phenyl-
propylamide (10). This compound was obtained as solid
in 86% yield, mp 72–73 °C. 1H NMR (300 MHz, CDCl3
d TMS): 0.773 (s, 1H: CH), 1.139–1.25 (d, J = 0.111,
12H: CH3), 1.799–1.847 (m, 2H: CH2), 2.622–2.673 (t,
J = 0.026, 2H: CH2), 3.238–3.306 (q, J = 0.02, 2H:
CH2), 5.23 (s, 1H: NH), 7.163–7.281 (m, 5H). Anal.
Calcd for C17H25NO: C, 78.72; H, 9.71; N, 5.39. Found:
C, 78.44; H, 9.80; N, 5.37.
4.2.10.
2,2,3,3-Tetramethylcyclopropanecarbonyl-2-
chloro-benzylamide (16). This compound was obtained
as solid in 81% yield, mp 103–104 °C. 1H NMR
(300 MHz, CDCl3 d TMS): 0.856 (s, 1H: CH), 1.139–
1.241 (d, J = 0.102, 12H: CH3), 4.509–4.489 (d,
J = 0.02, 2H: CH2), 5.821 (s, 1H: NH), 7.189–7.388
(m, 4H: H-Ar). Anal. Calcd for C15H20NOCl: C,
67.79; H, 7.57; N, 5.27; Cl, 13.30. Found: C, 67.89; H,
7.50; N, 5.40; Cl, 13.13.
4.2.5.
2,2,3,3-Tetramethylcyclopropanecarbonyl
(1-
4.2.11. 2,2,3,3-Tetramethylcyclopropanecarbonyl-4-flu-
oro-benzylamide (17). This compound was obtained as
solid in 75% yield, mp 78–79 °C. H NMR (300 MHz,
CDCl3 d TMS): 0.851 (s, 1H: CH), 1.154–1.281 (d,
J = 0.127, 12H: CH3), 4.377–4.396 (d, J = 0.019, 2H:
CH2), 5.728 (s, 1H: NH), 7.009–7.260 (m, 4H: H-Ar).
Anal. Calcd for C15H20NOF: C, 72.26; H, 8.08; N,
5.61; F, 7.61. Found: C, 72.08; H, 8.08; N, 5.94; F, 7.08.
methyl-benzyl)-amide (11). This compound was obtained
as solid in 79% yield, mp 105–106 °C. 1H NMR
(300 MHz, CDCl3 d TMS): 0.843 (s, 1H: CH), 1.135–
1.27 (dd, J = 0.022, J0 = 0.046, 12H: CH3), 1.464–1.487
(d, J = 0.023, 3H: CH3), 5.11–5.18 (m, 1H: CH), 5.610
(s, 1H: NH), 7.233–7.341 (m, 5H: H-Ar). Anal. Calcd
for C16H23NO: C, 78.31; H, 9.45; N, 5.71. Found: C,
78.29; H, 9.53; N, 5.69.
1
4.2.12. 1-Phenyl-3-(2,2,3,3-tetramethylcyclopropanecar-
bonyl)-urea (18). This compound was obtained as solid
in 77% yield, mp 195–196 °C. 1H NMR (300 MHz,
CDCl3 d TMS): 1.214 (s, 1H: CH), 1.243–1.316 (d,
J = 0.073, 12H: CH3), 7.057–7.11 (d, J = 0.053, 1H: H-
Ar), 7.259–7.316 (m, 2H: H-Ar), 7.523–7.555 (d,
J = 0.032, 2H: H-Ar), 9.612 (s, 1H: NH), 10.679 (s,
4.2.6.
methyl-2-phenylethyl)-amide (12). This compound was
obtained as solid in 82% yield, mp 55–56 °C. H NMR
(300 MHz, CDCl3 d TMS): 0.707 (s, 1H: CH), 1.086–
1.218 (dd, J = 0.038, J0 = 0.049, 12H: CH3), 1.246–
1.273 (d, J = 0.027, 3H: CH3), 2.911–2.962 (m, 1H:
2,2,3,3-Tetramethylcyclopropanecarbonyl
(2-
1

6304
J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
1H: NH). Anal. Calcd for C15H20N2O2: C, 69.21; H,
7.74; N: 10.76. Found: C, 69.43; H, 7.88; N, 10.47.
9.02; S, 10.33. Found: C, 57.91; H, 7.07; N, 9.11; S,
10.45.
4.2.13. 2,2,3,3-Tetramethylcyclopropanecarbonyl-(1H-
indol-3-ethyl)-amide (19). This compound was obtained
as solid in 92% yield, mp 109–110 °C. 1H NMR
(300 MHz, CD3OD d TMS): 1.001 (s, 1H: CH), 1.139–
1.216 (d, J = 0.077, 12H: CH3), 2.883–2.931 (t,
J = 0.022, 2H: CH2), 3.404–3.453 (t, 2H: CH2), 6.981–
7.070 (m, 4H: H-Ar), 7.126 (d, J = 0.028, 1H: CH),
7.296–7.322 (d, J = 0.026, 1H: NH), 7.537–7.563 (d,
J = 0.026, 1H: NH). Anal. Calcd for C18H24N2O: C,
76.02; H, 8.51; N, 9.85. Found: C, 75.99; H, 8.61; N,
9.87.
4.3.4. 2,2,3,3-Tetramethylcyclopropanecarbonyl-(4-sulfa-
moyl-phenylethyl)-amide (23). This compound was ob-
tained as solid in 87% yield, mp 111–112 °C. H NMR
(300 MHz, CDCl3 TMS d): 0.765 (s, 1H: CH), 1.138–
1.244 (d, J = 0.106, 12H: CH3), 2.869–2.917 (t,
J = 0.024, 2H: CH2), 3.474–3.534 (q, J = 0.02, 2H:
CH2), 4.753 (s, 2H: SO2NH2), 5.45 (s, 1H: NH),
7.344–7.370 (d, J = 0.026, 2H: H-Ar), 7.855–7.881 (d,
J = 0.026, 2H: H-Ar). Anal. Calcd for C16H24N2O3S:
C, 59.23; H, 7.45; N, 8.63; S, 9.88. Found: C, 59.01;
H, 7.37; N, 8.86; S, 9.53.
1
4.3. General procedure B for the synthesis of aromatic
sulfonamide 2,2,3,3-tetramethylcyclopropyl carboxamide
derivatives (20–23)
4.4. Biological testing
The evaluation of anticonvulsant activity in the max-
imal electroshock (MES), subcutaneous pentylenetet-
razole (scMet) tests as well as the determination of
toxicity in the rotorod test and positional stence tests
were performed at the NIH-Epilepsy Branch as a part
of the Anticonvulsant Drug Development Program
according to the protocols described in reference.22
All compounds for testing were prepared either by
dissolving or suspending in 0.5% methylcellulose.
The tested compounds were given in a concentration
that permits optimal accuracy of dosage without the
volume contributing excessively to total body fluid.
Thus, the volume used in mice was 0.01 mL per gram
body weight, and in rats, 0.04 mL per 10 g body
weight.
TMC-Cl (3 g, 9 mmol) dissolved in dry acetone
(20 mL) was slowly added to stirred solution of suit-
able sulfonamide (9.2 mmol) and pyridine (9.1 mmol)
in dry acetone (50 mL). After addition, the reaction
mixture was stirred for 12 h at room temperature.
The organic solvent was then evaporated under vac-
uum and the residue dissolved in ethyl acetate
(100 mL) and washed three times with 20 mL of dis-
tilled water. The organic fraction was dried over
MgSO4, filtered, and evaporated.
The obtained products were purified by crystallization
using ethylacetate/petroleum ether mixture (1:3).
4.3.1. 2,2,3,3-Tetramethylcyclopropanecarbonyl-(2,4-dis-
ulfamoyl-5-chloro-phenyl)-amide (20). This compound
was obtained as solid in 52% yield, mp 230–232 °C. H
4.5. Determination of the median effective dose (ED50)
and the median neurotoxic dose (TD50)
1
NMR (300 MHz, CD3COCD3 d TMS): 0.961 (s, 1H:
CH), 1.248–1.306 (d, J = 0.058, 12H: CH3), 6.376 (s,
1H: NH), 6.556 (s, 2H: SO2NH2), 6.801 (s, 2H:
SO2NH2), 7.074 (s, 1H: H-Ar), 8.305 (s, 1H: H-Ar).
Anal. Calcd for C14H20N3O5ClS2: C, 41.02; H, 4.92;
N, 10.25; Cl, 8.65; S, 15.64. Found: C, 41.22; H, 4.99;
N, 10.16; Cl, 8.51; S, 15.17.
For the determination of the ED50 by the respective
anticonvulsant procedures, doses of the titled com-
pounds were varied until at least four points were estab-
lished between the dose level of no protection and 100%
protection. These data were then subjected to probit
analysis and the ED50 and 95% confidence intervals were
calculated.
4.3.2. N-(2,2,3,3-Tetramethylcyclopropanecarboxamide)-
p-phenylsulfonamide (21). This compound was obtained
as solid in 61% yield, mp 208–209 °C. 1H NMR
(300 MHz, CD3SOCD3 d): 1.171–1.224 (d, J = 0.053,
12H: CH3), 1.302 (s, 1H: CH), 7.197 (s, 2H: SO2NH2),
7.694 (m, 4H: H-Ar), 10.219 (s, 1H: NH). Anal. Calcd
for C14H20N2O3S: C, 56.73; H, 6.80; N, 9.45; S, 10.82.
Found: C, 57.00; H, 6.75; N, 9.66; S, 10.57.
The TD50 was determined by varying the dose of the
studied compounds until four points were established
between the dose level that induced no signs of min-
imal motor impairment in any of the animals, and
the dose at which all the animals were considered im-
paired. The TD50 and the 95% confidence intervals
were then calculated by probit analysis. The protec-
tive index was calculated by dividing the TD50 by
ED50.
4.3.3. 2,2,3,3-Tetramethylcyclopropanecarbonyl-(4-sulfa-
moyl-benzyl)-amide (22). This compound was obtained
as solid in 75% yield, mp 207–208 °C. 1H NMR
(300 MHz, CD3SOCD3 d): 1.102–1.162 (d, J = 0.06,
12H: CH3), 1.232 (s, 1H: CH), 4.257–4.277 (d,
J = 0.02, 2H: CH2), 7.269 (s, 2H: SO2NH2), 7.359–
7.387 (d, J = 0.028, 2H: H-Ar), 7.725–7.752 (d,
J = 0.027, 2H: H-Ar), 8.317 (t, J = 0.019, 1H: NH).
Anal. Calcd for C15H22N2O3S: C, 58.04; H, 7.14; N,
Acknowledgments
This work is abstracted from the Ph.D. thesis of Mr.
Jakob A. Shimshoni in partial fulfillment of the Ph.D.
degree requirements for The Hebrew University of
Jerusalem. The authors thank Mr. James P. Stables,
Director of the NIH-NINDS-Anticonvulsant Screening
Program (ASP), for testing the compounds.

J. A. Shimshoni et al. / Bioorg. Med. Chem. 16 (2008) 6297–6305
6305
11. Isoherranen, N.; Yagen, B.; Bialer, M. Curr. Opin. Neurol.
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