Design, synthesis, and anticonvulsant activity of 1-(pyrid-3- ylsulfonamido)-2-nitroethylenes

Article abstract of DOI:10.1021/jm981022n

The lipophilic 1-cycloalkylamino-1-(pyrid-3-yl-sulfonamido)-2- nitroethylenes were synthesized as bioisosteres of BM-34, an anticonvulsant sulfonylthiourea. Compound 17 (ip) emerged from the maximal electroshock seizure (MES) test with a 50% effective dos

Full text of DOI:10.1021/jm981022n

J . Med. Chem. 1998, 41, 3239-3244
3239
Design , Syn th esis, a n d An ticon vu lsa n t Activity of
1
-(P yr id -3-ylsu lfon a m id o)-2-n itr oeth ylen es
,
†
‡
†
§
Bernard Masereel,* J ohan Wouters, Lionel Pochet, and Didier Lambert
Department of Pharmacy and Laboratory of Molecular Structures, University of Namur, FUNDP, 61, rue de Bruxelles,
5
000 Namur, Belgium, and Laboratory of Medicinal Chemistry and Radiopharmacy, Catholic University of Louvain,
Avenue Mounier CMFA 73.40, 1200 Brussels, Belgium
Received April 4, 1998
The lipophilic 1-cycloalkylamino-1-(pyrid-3-yl-sulfonamido)-2-nitroethylenes were synthesized
as bioisosteres of BM-34, an anticonvulsant sulfonylthiourea. Compound 17 (ip) emerged from
the maximal electroshock seizure (MES) test with a 50% effective dose (ED50) of 8.25 mg/kg.
Its anticonvulsant profile was similar to that of phenytoin (ED50 ) 9.51 mg/kg) and of BM-34
(ED50 ) 1.19 mg/kg): active in the MES test and inactive in seizures induced by subcutaneous
injection of pentetrazole, strychnine, bicuculline, picrotoxin, or N-methyl-D,L-aspartate. The
neurotoxicity of 17 (TD50 ) 113.8 mg/kg) was lower than that of phenytoin (TD50 ) 65.5 mg/
kg) but higher than that of BM-34 (TD50 ) 147.2 mg/kg). Crystallographic study revealed
that BM-401 (17) was a zwitterionic structure. Its sulfonamido nitroethylene side chain adopted
a conformation which placed the two cycloalkyl rings face to face to form a single hydrophobic
area.
In tr od u ction
Nonclassical bioisosteric molecules are characterized
by a different number of atoms, by some similar phys-
icochemical parameters, and by a broadly similar bio-
1
logical activity. This concept has been applied to the
thiourea function of metiamide (1) and led to the
discovery of cimetidine (2), a cyanoguanidine with
histamine-H2 antagonism (Figure 1).2 Classically, the
1
,1-diamino-2-nitroethylene is another group considered
1
as a bioisostere of the thiourea function. This bio-
isosteric replacement has been used to design ranitidine
3
(
3), an antiulcer nitroethylene derivative (Figure 1).
Recently, the acylurea group of phenytoin was modified
into an anticonvulsant acylcyanoguanidine.4 A similar
strategy was also dedicated to the sulfonylurea function
of torasemide (4) and glibenclamide, an ATP-sensitive
+
K -channel blocker, which was transformed into a
sulfonylcyanoguanidine moiety to give compounds with
a similar pharmacological profile.5-7 In the present
work, we prepared lipophilic 1-amino, 1-sulfonamido,
2
-nitroethylene compounds (11-23) regarded as bio-
isosteres of the sulfonylthiourea BM-34 (5) (Figure 1)
structurally related to torasemide (4), a diuretic sulfo-
nylurea.8 Interestingly, BM-34 (5) was found devoid of
diuretic activity in rats but showed, in anticonvulsant
models, a higher potency, a lower neurotoxicity and a
profile similar to that of phenytoin.9 Epilepsy is a
neurological disorder that involves the depolarization
and interaction of ensembles of CNS neurons ultimately
to produce the abnormal behavior pattern seen during
the epileptic seizure.10 Valproate, phenytoin, and car-
F igu r e 1. Bioisosterism of the thiourea function.
bamazepine are still the major drugs used today al-
though phenytoin is much less used in Europe than in
the USA. Due to the numerous side effects of these
molecules, and the existence of refractory epilepsies,
new drugs with different mechanism of actions have
recently become available or await their approval:
vigabatrin, gabapentin, lamotrigine, oxcarbazepine, ti-
11,12
agabine, and remacemide.
Because some 20% of all
patients remain refractory to the current drugs or suffer
unacceptable side effects, there is still a need for new
antiepilectic drugs. BM-34 displayed an original tem-
plate for chemical modifications, and considering its
high anticonvulsant potency was a good lead for this
study.
*
Corresponding author: Professor B. Masereel, Department of
Pharmacy, University of Namur, FUNDP, 61, rue de Bruxelles, 5000
NAMUR, Belgium. Tel: + 32 (0)81 72 43 38. Fax: + 32 (0)81 72 43 38.
E-mail: bernard.masereel@fundp.ac.be.
†
Department of Pharmacy, University of Namur.
Laboratory of Molecular Structures, University of Namur.
Catholic University of Louvain.
‡
§
S0022-2623(98)01022-X CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/24/1998

3
240 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 17
Masereel et al.
Sch em e 1. Synthesis of 1-Amino-1-[(4-cycloalkylamino-
Ta ble 1. Lipophilicity, Anticonvulsant and Diuretic Activity of
the Nitroethylene Derivatives
pyrid-3-yl)sulfonamido]-2-nitroethylenes Related to BM-
a
3
4
MES testb
diuresisc
(mL/kg)
compd
R1
C6H11
C6H11
C6H11
C7H13
C7H13
C7H13
C8H15
C8H15
C8H15
3-CH3C6H4
torasemide
R2
log Pa 0.5 h
3 h
1
1
1
1
1
1
1
1
1
2
1
2
3
4
5
6
7
8
9
0
4
C6H11
C7H13
C8H15
C6H11
C7H13
C8H15
C6H11
C7H13
C8H15
C6H11
+1.67
+1.97
+2.27
+1.99
+2.30
+2.57
+2.31
+2.59
+2.86
+1.66
+0.47
0/6
0/6
2/6
1/6
1/6
1/6
1/6
2/6
0/6
1/6
0/6
4/7
5/7
4/7
5/6
5/6
4/7
7/7
5/6
3/7
2/6
0/6
20
20
21
18
25
23
22
20
22
29
88
a
Values are means of three determinations obtained by the RP-
a
(
i) R2-NH2, C2H5OH; (ii) H2O2, CH3COOH; (iii) R2-NH2,
HPLC method. b Rate of mice (n ) 6-7) protected against elec-
troshock (50 mA; 0.2 s) after ip injection of 30 mg/kg. Urinary
volume excreted over 4 h by rats after oral administration of 30
mg/kg. Control is 22 mL/kg.
CH3OH; (iv) R1-NH2, 2-propanol; (v) 1 equiv of NaOH, DMF,
dioxane.
c
The synthesis, the physicochemical and the anti-
convulsant properties of the novel nitroethylene deriva-
tives are discussed.
Ta ble 2. Correlation between the Logarithm of the Partition
Coefficient (log P) Determined by the Shake-Flask Technique
and the Logarithm of the Capacity Factor (log k′) Obtained by
RP-HPLC
Resu lts a n d Discu ssion
Ch em istr y. The 1,1-bismethylsulfanyl-2-nitroethyl-
ene13 6 was refluxed with 1.2 equiv of cycloalkylamine
to give the corresponding 1-cycloalkylamino-1-methyl-
sulfanyl-2-nitroethylene
8 (Scheme 1). 1-Methyl-
sulfanyl-1-methylsulfinyl-2-nitroethylene 7 prepared by
1
4
compd
R1
R2
log Pa
log k′ b
oxidation of 6 and treatment with isopropylamine at
room temperature led to 1-isopropylamino-1-methyl-
sulfanyl-2-nitroethylene. On the other hand, the 4-aryl-
21
CH3CH2
C5H9
3-CH3C6H4
C6H11
(CH3)2CH
(CH3)2CH
(CH3)2CH
C6H11
-0.482
+0.538
+1.116
+1.588
-0.627
-0.243
-0.072
+0.166
2
2
5
,15
23
amino- and 4-cycloalkylaminopyrid-3-ylsulfonamides
1
1
1
3
0 were synthesized by the reaction of 4-chloropyrid-
-ylsulfonamide 9 with the corresponding aryl or
a
1
5
Partition coefficient in 1-octanol phosphate buffer pH 7.40. log
P ) (2.662 log k′) + 1.206; r ) 0.997; n ) 4. b Capacity factor
determined by RP-HPLC. All values are the mean of three
determinations.
cycloalkylamine. Finally, the sodium salt of 10 reacted
with the required 1-substituted amino-1-methylsulfanyl-
2
-nitroethylene 8 to obtain the sulfonamidonitroethyl-
enes derivatives 11-23 (Tables 1 and 2).
Lip op h ilicity. The novel nitroethylene derivatives
(Table 1) are considered as the bioisosteres of their
sulfonylurea and sulfonylthiourea counterparts which
are neuroprotective16 or anticonvulsant drugs. Beside
the active carrier systems present in the blood-brain
barrier endothelium, the brain penetration is probably
related to the overall drug lipophilicity. This later
parameter is commonly expressed as the logarithm of
the partition coefficient (log P) between a lipophilic
phase (1-octanol) and an aqueous buffer. To reach the
9
1
5
F igu r e 2. Lipophilicity of the sulfonylureas (b), -thioureas
(0),15 and -cyanoguanidines (9)5 compared to their nitro-
ethylene counterparts (O).
central nervous system, the log P value of a drug should
be higher than +1.5.17 The capacity factor (log k′) of
compounds 21-23 and 11 was measured using a RP-
HPLC assay (Table 2).5 Their log k′ values were
significantly correlated to their partition coefficient (log
P) determined by using the 1-octanol/phosphate buffer
pH 7.40 system (Table 2).18 The log P values of the
nitroethylene derivatives 11-20 (Table 1) were extrapo-
lated from their log k′ values. The log P of the molecules
bearing two cycloalkyl residues are ranging from +1.67
to +2.86. These values are in the range which can cross
the blood-brain barrier. The log P increased with the
C-atom number included in the R1 and R2 cycloalkyl
(Figure 2). Whatever the size of the cycloalkyl residues
(Table 1), the log P values were similar for the com-
pounds having an identical total number of methylenes
(compare 12, 14; 13, 15, 17; 16, 18). The increase of
one methylene unit resulted in an enhanced lipophilicity
of 0.30 () ∆log P CH2). The lipophilicity of the m-tolyl

1
-(Pyrid-3-ylsulfonamido)-2-nitroethylenes
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 17 3241
Ta ble 3. Neurotoxicity (TD50) and Anticonvulsant Profile of BM-401 (17), BM-34 (5), and Phenytoin
ED50 and PI (mg/kg)a
time of
drug
peak effect
TD50 (mg/kg)
MES
PTZ
STR
BIC
PIC
NMLDA
b
>100c
>100
>100
BM-401 (17)
BM-34 (5)
phenytoin
3 h
4 h
2 h
113.8 (96.4-121.2)
147.2 (102.4-187.5)
65.5 (52.5-72.1)
8.25 (5.1-13.4) PI ) 13.8
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
1.19 (0.53-2.68) PI ) 123.7
9.51 (2.57-15.4) PI ) 6.9
a
Eight OF-1 male mice per group. b 95% confidence interval. c No protection up to 100 mg/kg.
Ta ble 4. Crystallographic Data, Optimized and Theoretical
Valuesa of the Torsional Angles, and Energy Level of the Four
Conformers of 17
F igu r e 3. Time-course activity of BM-401 (17) (30 mg/kg ip)
in the MES test. Eight OF-1 male mice for each time.
conformer φ1 (deg) φ2 (deg) φ3 (deg) φ4 (deg) E (kcal/mol)
moiety was close to that of a cyclohexyl (compare 11 and
crystal
â
+69.4 +107.5 +172.5
-5.8
+3.3
(0)
2
0) (Table 1). At pH 7.40, the nitroethylene compounds
+45.5
+90)
+57.9 -176.1
(+90) (180)
8.53
15.56
13.10
11.94
were systematically more lipophilic (∆log P ) +0.15 to
(
9
+
0.30) than their urea bioisosteres (P < 0.01) as well
R
γ
δ
-117.2
+49.3 -152.3 +130.2
(+90) (180) (180)
+54.1 -159.7 +134.2
as the sulfonylthiourea counterparts (∆log P ) +0.16
to +0.20).9 In the same experimental conditions, the
nitroethylenes derivatives were significantly (P < 0.01)
less lipophilic than the corresponding sulfonylcyan-
oguanidines (∆log P ) -0.27 to -1.04).5 Thus the
lipophilicity of these bioisostere functions is ordered as
follows: SO2NH-C(dN-CN)-NH > SO2NH-C(dCH-
NO2)-NH > SO2NH-CS-NH g SO2NH-CO-NH.
P h a r m a cology. The anticonvulsant activity of the
nitroethylene derivatives was examined at 30 mg/kg (ip)
in mice by using the maximal electroshock seizure
(-90)
+62.4
(
+90)
+49.9
+90)
(+90)
+54.4
(+90)
(180)
-2.1 +131.6
(0) (180)
(180)
(
a
Theoretical values are in parentheses.
(85 mg/kg), strychnine (1.20 mg/kg), picrotoxin (3.15 mg/
kg), N-methyl-D,L-aspartic acid (NMLDA, 340 mg/kg),
or bicuculline (2.70 mg/kg) (Table 3). These results
suggested that neurotransmitters such as glycine, GABA,
or NMDA were not directly involved in the mechanism
of action of 17 but do not preclude downstream modula-
tion of their sites. Thus its pharmacological profile was
similar to that of phenytoin and BM-34. As BM-34, 17
was structurally close to torasemide, a diuretic sulfo-
(
MES) test which detect drugs that prevent spread of
1
9
tonic-clonic seizures. The MES test was applied 0.5
and 3 h after drug injection, and the rate of protected
mice noted (Table 1). For each drug, a poor protection
against MES was observed 0.5 h after the ip adminis-
tration. At this time, 13 and 18 exhibited the best
protection (33.3%). Evaluated 3 h after the drug injec-
tion, the protection rate was higher than 50% for each
group treated by the compounds 11-18. Compound 17
provided complete protection against induced seizures
in mice at this dose level (Table 1). The weak activity
observed at 0.5 h could be related to a lower drug
concentration in the central nervous system at that
time. The most potent molecule 17, called BM-401, was
the nitroethylene counterpart of BM-34 (5), which was
the most active compound among the sulfonylureas and
sulfonylthioureas previously studied.9
8
nylurea (Figure 1). Conversly to some lipophilic sul-
9
fonylureas and sulfonylthioureas, 17 (30 mg/kg) had
no diuretic activity in rats (Table 1).
At the time of peak effect (3 h), the neurotoxicity was
evaluated by the rotorod procedure in mice20 which
detects motor coordination deficits. The median toxic
dose (TD50) of 17 (113.8 mg/kg) was higher than that of
phenytoin (65.5 mg/kg) and lower than that of BM-34
(147.2 mg/kg). The protective index (PI ) TD50/ED50)
of 17 was better than that of phenytoin but lower than
that of BM-34 (Table 3).
X-r a y Cr ysta llogr a p h y a n d Molecu la r Mod elin g.
In the crystal, 17 adopted a zwitterionic form resulting
from the transfer of the sulfonamide proton to the
nitrogen atom of the pyridine ring (Table 4). Valence
angle C -N -C (119.1°) close to 120° also suggested
The time-course activity (Figure 3) of 17 (30 mg/kg)
gave a peak effect (Tmax ) 3 h) shorter than that of BM-
3
4 (Tmax ) 4 h) but longer than phenytoin (Tmax ) 2
9
h). At that time, the MES ED50 value of 17 (8.25 mg/
kg) was similar to that of phenytoin (9.51 mg/kg) but
higher than that of BM-34 (1.19 mg/kg) determined in
1
2
13
14
protonation of the pyridine ring. This zwitterionic
structure was in agreement with the intermolecular
interaction which revealed an interaction between the
protonated nitrogen of the pyridinum ring and an
oxygen of the nitro group. An intramolecular H-bond
which involved the nitrogen N9 (Table 4) and one oxygen
9
the same test conditions (Table 3).
When examined at doses up to 100 mg/kg (ip), 17, BM
3
4, and phenytoin did not protect mice against convul-
sions induced by subcutaneous injection of pentetrazole

3
242 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 17
Masereel et al.
of the sulfonyl group reinforced the molecular packing.
Crystallographic studies of several sulfonylureas, sul-
fonylthioureas, or sulfonylcyanoguanidines related to 17
revealed four different conformations (R, â, γ, δ), defined
with an excess of cyclohexylamine (2.1 mL, 18 mmol) for 18 h.
After cooling, the formed precipitate was collected by filtration,
washed with ice-cold ethanol, and dried to give the title
2
compound (2.02 g, 75%): mp 101-103 °C; IR (KBr) 1563 (NO )
-
1
1
cm ; H NMR (DMSO-d
cyclohexyl), 2.45 (s, 3H, SCH
1H, NH). Anal. (C H N O S) C, H, N, S.
6
, 300 MHz) δ 1.05-1.95 (m, 11H,
by typical values of the torsion angles φ1, φ2, φ3, and φ4
3
), 6.68 (s, 1H, CHNO ), 10.37 (b,
2
5
(
Table 4). In the crystal, the values of the torsion
9
16
2
2
angles of the sulfonamidonitroethylene side chain in-
1-Cycloh exyla m in o-1-[(4′-cyclooctyla m in o)p yr id -3′-yl-
su lfon a m id o)]-2-n itr oeth ylen e (17). The sodium salt of
4-cyclooctylaminopyrid-3-ylsulfonamide 105 (1.08 g, 3.5 mmol))
and 0.90 g (4.2 mmol) of 1-cyclohexylamino-1-methylsulfanyl-
dicated that 17 adopted a â conformation as observed
,15
2
1
in torasemide (Table 4). To establish the relative
energies of the R, â, γ, and δ conformations, only the
torsion angles (φ1 to φ4) defining the different geometries
were studies. The other rotable torsion angles, in
particular those of the two cycloalkyl rings, were fixed
to their initial values measured in the crystal. Confor-
mational analysis showed that the â conformation
corresponded to the preferred geometry of 17 as com-
pared to the energy level of the R (∆E ) 7.03 kcal/mol),
the γ (∆E ) 4.57 kcal/mol), or the δ conformation (∆E
2
(
6
-nitroethylene 8 were dissolved in a mixture of 1,4-dioxane
3 mL) and N,N-dimethylformamide (2 mL) and refluxed for
h. After evaporation of solvents under reduced pressure,
the residue was dissolved in water (50 mL) and 2.5N NaOH
(2 mL). The solution was extracted three times with diethyl
ether (50 mL) and adjusted to pH 3 with dilute HCl. The
precipitate was collected by filtration, washed with water,
dried, and crystallized from absolute ethanol (50 mL) to afford
the title compound (0.76 g, 48%): mp 186-188 °C; IR (KBr)
-1
1
1
(
577 (NO
m, 26H, cyclohexyl and cyclooctyl), 6.70 (s, 1H, CH-NO
(d, 1H, 5H-pyridine), 7.42 (d, 1H, pyridine-NH), 8.22 (d, 1H,
H-pyridine), 8.57 (s, 1H, 2H-pyridine), 10.25 (d, 1H, NH-
cyclohexyl). Anal. (C21 S) C, H, N, S.
2
) cm ; H NMR (DMSO-d
6
, 300 MHz) δ 0.96-1.97
)
3.41 kcal/mol). In the â conformation, both cycloalkyl
2
), 7.10
rings were close and formed a single hydrophobic area.
In conclusion, the synthesis of the 1-amino, 1-sulfon-
amido, 2-nitroethylenes as bioisosteres of the anticon-
vulsant BM-34 led to the discovery a novel anticonvul-
sant 17, called BM-401, exhibiting a pharmacological
profile similar to that of phenytoin and BM-34. 17 was
less neurotoxic and showed anticonvulsant activity
similar to that of phenytoin. Additional experiments
are warranted to elucidate the mechanism of action of
6
33 5 4
H N O
This procedure was used for the synthesis of the compounds
1
1-23.
1
-Cycloh exyla m in o-1-[(4′-cycloh exyla m in o)p yr id -3′-yl-
su lfon a m id o)]-2-n it r oet h ylen e (11). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 4.0 mmol) and 1-cyclohexylamino-1-
methylsulfanyl-2-nitroethylene 8 (0.9 g, 4.2 mmol): yield 78%
(
1
(
6
1.32 g); mp 187-189 °C; 1H NMR (DMSO-d
6
, 300 MHz) δ
.15-1.95 (m, 22H, two cyclohexyl), 6.72 (s, 1H, CH-NO ), 7.20
d, 1H, 5H-pyridine), 7.38 (d, 1H, pyridine-NH), 8.27 (d, 1H,
H-pyridine), 8.57 (s, 1H, 2H-pyridine), 10.32 (d, 1H, NH-
cyclohexyl). Anal. (C19 S) C, H, N, S.
-Cycloh ep t yla m in o-1-[(4′-cycloh exyla m in o)p yr id -3′-
1
7. This nitroethylene derivative presents an interest-
2
ing alternative to BM-34 for which the thiourea function
is well-known to be responsible for agranulocytosis
2
,22,23
neutropenia and aplastic anemia.
29 5 4
H N O
1
Exp er im en ta l Section
ylsu lfon a m id o)]-2-n itr oeth ylen e (12). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 4.0 mmol) and 1-cycloheptylamino-1-
Ch em istr y. Melting points were determined on a B u¨ chi
B-540 capillary apparatus. IR spectra were recorded as KBr
pellets on a Perkin-Elmer 1750 FT spectrophotometer. The
methylsulfanyl-2-nitroethylene 8 (0.96 g, 4.2 mmol): yield 56%
1
1
(0.98 g); mp 186-188 °C; H NMR (DMSO-d , 300 MHz) δ 1.18-
H NMR spectra were taken on a Brucker (300 MHz) instru-
ment in DMSO-d with HMDS as an internal standard;
6
1
.92 (m, 24H, cyclohexyl and cycloheptyl), 6.70 (s, 1H, CH-
NO ), 7.19 (d, 1H, 5H-pyridine), 7.40 (d, 1H, pyridine-NH), 8.26
d, 1H, 6H-pyridine), 8.58 (s, 1H, 2H-pyridine), 10.37 (d, 1H,
NH-cycloheptyl). Anal. (C20 S) C, H, N, S.
6
chemical shifts were reported in δ values (ppm) relative to
2
(
internal HMDS. The abbreviation s ) singlet, d ) doublet, t
31 5 4
H N O
)
triplet, m ) multiplet, and b ) broad signal were use
throughout. Elemental analyses (C, H, N, S) were performed
on a Carlo-Erba elemental analyzer and were within (0.4%
of the theoretical values. All reactions were routinely checked
by TLC on silica gel Merck 60F254.
1-Cyclooctyla m in o-1-[(4′-cycloh exyla m in o)p yr id -3′-yl-
su lfon a m id o)]-2-n it r oet h ylen e (13). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 4.0 mmol) and 1-cyclooctylamino-1-
1
-Meth ylsu lfa n yl-1-m eth ylsu lfin yl-2-n itr oeth ylen e (7).
methylsulfanyl-2-nitroethylene 8 (1.1 g, 4.7 mmol): yield 51%
1
Hydrogen peroxide (30%, 11.3 mL) was added dropwise to a
(0.90 g); mp 171-174 °C; H NMR (DMSO-d
6
, 300 MHz) δ 1.12-
stirred solution of 1,1-bismethylsulfanyl-2-nitroethylene13 (6,
1.97 (m, 26H, cyclohexyl and cyclooctyl), 6.69 (s, 1H, CH-NO
2
),
1
6.5 g, 100 mmol) in acetic acid (450 mL) and heated to 60 °C.
7.19 (d, 1H, 5H-pyridine), 7.40 (d, 1H, pyridine-NH), 8.27 (d,
1H, 6H-pyridine), 8.58 (s, 1H, 2H-pyridine), 10.38 (d, 1H, NH-
After 17 h of reaction, the medium was evaporated under
reduced pressure and the crude residue crystallized from
methylethyl ketone (50 mL) to give the title compound (7.50
cyclooctyl). Anal. (C21
33 5 4
H N O S) C, H, N, S.
1-Cycloh exyla m in o-1-[(4′-cycloh ep t yla m in o)p yr id -3′-
ylsu lfon a m id o)]-2-n itr oeth ylen e (14). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 3.7 mmol) and 1-cyclohexylamino-1-
-
1 1
g, 41%): mp 118-120 °C; IR (KBr) 1549 (NO
DMSO-d , 300 MHz). Anal. (C NO ) C, H, N, S.
-Isopr opylam in o-1-m eth ylsu lfan yl-2-n itr oeth ylen e (8).
Isopropylamine (3.8 mL, 45 mmol) was added to a solution of
2
) cm ; H NMR
(
6
4
H
7
3 2
S
1
methylsulfanyl-2-nitroethylene 8 (0.96 g, 4.5 mmol): yield 54%
1
4
1
1
-methylsulfanyl-1-methylsulfinyl-2-nitroethylene 7 in metha-
(0.88 g); mp 191-193 °C; H NMR (DMSO-d
6
, 300 MHz) δ 1.02-
nol (120 mL). The mixture was stirred for 30 min at 25 °C.
After evaporation of the solvent under reduced pressure, the
crude product was crystallized from 2-propanol (10 mL) to give
the title compound (2.01 g, 30%): mp 92-94 °C; IR (KBr) 1562
1.95 (m, 24H, cycloheptyl and cyclohexyl), 6.71 (s, 1H, CH-
NO ), 7.15 (d, 1H, 5H-pyridine), 7.41 (d, 1H, pyridine-NH), 8.24
(d, 1H, 6H-pyridine), 8.57 (s, 1H, 2H-pyridine), 10.35 (d, 1H,
NH-cyclohexyl). Anal. (C20 S) C, H, N, S.
1-Cycloh ep tyla m in o-1-[(4′-cycloh ep tyla m in o)p yr id -3′-
ylsu lfon a m id o)]-2-n itr oeth ylen e (15). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 3.7 mmol) and 1-cycloheptylamino-1-
2
31 5 4
H N O
-
1
1
(
NO
2s, 6H, C(CH
.55 (s, 1H, CH-NO
C, H, N, S.
2
) cm ; H NMR (DMSO-d
), 2.43 (s, 3H, CH
), 10.15 (b, 1H, NH). Anal. (C
6
, 300 MHz) δ 1.10 and 1.23
(
6
3
)
2
3
S), 3.84 (m, 1H, CH(CH
3
)
2
2
),
S)
2
6
H
12
N
2
O
1
-Cycloh e xyla m in o-1-m e t h ylsu lfa n yl-2-n it r oe t h yl-
methylsulfanyl-2-nitroethylene 8 (1.0 g, 4.3 mmol): yield 31%
1
3
1
en e (8). A solution of 1,1-bismethylsulfanyl-2-nitroethylene
6, 2.0 g, 12 mmol) in absolute ethanol (25 mL) was refluxed
(0.55 g); mp 139-141 °C; H NMR (DMSO-d
6
, 300 MHz) δ 1.10-
(
1.98 (m, 26H, two cycloheptyl), 6.70 (s, 1H, CH-NO
2
), 7.10 (d,

1
-(Pyrid-3-ylsulfonamido)-2-nitroethylenes
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 17 3243
1
H, 5H-pyridine), 7.40 (d, 1H, pyridine-NH), 8.26 (d, 1H, 6H-
N NaOH (2 mL). The solution was extracted three times with
diethyl ether (50 mL) and adjusted to pH 3 with dilute HCl.
The precipitate was collected by filtration, washed with water,
dried, and crystallized from absolute ethanol (40 mL) to afford
the title compound (0.79 g, 53%): mp 168-169 °C; IR (KBr)
pyridine), 8.55 (s, 1H, 2H-pyridine), 10.39 (d, 1H, NH-cyclo-
heptyl). Anal. (C21 S) C, H, N, S.
-Cyclooct yla m in o-1-[(4′-cycloh ep t yla m in o)p yr id -3′-
ylsu lfon a m id o)]-2-n itr oeth ylen e (16). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.1 g, 4.1 mmol) and 1-cyclooctylamino-1-
33 5 4
H N O
1
-
1
1
1570 (NO
2
) cm ; H NMR (DMSO-d
), 2.32 (s, 3H, aryl-CH ), 4.02 (m, 1H, CH(CH
), 6.95-7.50 (m, 5H, phenyl and 5H-
6
, 300 MHz) δ 1.05 (2s,
6H, C(CH
3
)
2
3
3 2
)
),
methylsulfanyl-2-nitroethylene 8 (1.2 g, 4.9 mmol): yield 63%
6.80 (s, 1H, CH-NO
pyridine), 8.18 (d, 1H, 6H-pyridine), 8.63 (s, 1H, 2H-pyridine),
9.38 (br s, 1H, pyridine-NH), 10.15 (d, 1H, NH-isopropyl). Anal.
2
1
(
1
1.20 g); mp 177-179 °C; H NMR (DMSO-d
6
, 300 MHz) δ
.20-1.97 (m, 28H, cycloheptyl and cyclooctyl), 6.69 (s, 1H,
CH-NO
2
), 7.10 (d, 1H, 5H-pyridine), 7.28 (d, 1H, pyridine-NH),
21 5 4
(C17H N O S) C, H, N, S.
8
1
.28 (d, 1H, 6H-pyridine), 8.58 (s, 1H, 2H-pyridine), 10.39 (d,
H, NH-cyclooctyl). Anal. (C22 S) C, H, N, S.
-Cycloh ep t yla m in o-1-[(4′-cyclooct yla m in o)p yr id -3′-
Lip op h ilicity. The lipophilicity of standard molecules (21-
3 and 11) listed in Table 2 was expressed as the logarithm
35 5 4
H N O
2
1
of the partition coefficient (log P) in 1-octanol/phosphate buffer
pH 7.40 by using the shake-flask technique.24 A RP-HPLC
system was also loaded to determine their log k′ values defined
as (t - t )/t where t is the sample retention time and t the
ylsu lfon a m id o)]-2-n itr oeth ylen e (18). The title compound
was obtained as previously described for compound 17 by
starting from 10 (1.0 g, 3.5 mmol) and 1-cycloheptylamino-1-
r
o
o
r
o
NO retention time detected at 254 nm.5 The stationary
-
methylsulfanyl-2-nitroethylene 8 (1.0 g, 4.3 mmol): yield 69%
3
1
(
1
1.14 g); mp 184-186 °C; H NMR (DMSO-d
6
, 300 MHz) δ
phase was an octadecyl column (Lichrospher 100RP-18, 15 cm
length, 5 µm porosity), and the mobile phase was a mixture of
phosphate buffer pH 7.40 with 2-propanol (70:30 v/v). A
correlation curve was calculated from log P and log k′ values
of the standards: log P ) (2.662 log k′) + 1.206; n ) 4; r )
0.997. By using the correlation curve, the log P values of other
compounds (Table 1) were then obtained by extrapolation of
their log k′ values evaluated by chromatography.
.22-1.95 (m, 28H, cyclooctyl and cycloheptyl), 6.70 (s, 1H,
CH-NO
8
1
2
), 7.09 (d, 1H, 5H-pyridine), 7.42 (d, 1H, pyridine-NH),
.26 (d, 1H, 6H-pyridine), 8.57 (s, 1H, 2H-pyridine), 10.38 (d,
H, NH-cycloheptyl). Anal. (C22 S) C, H, N, S.
-Cyclooctyla m in o-1-[(4′-cyclooctyla m in o)p yr id -3′-yl-
35 5 4
H N O
1
su lfon a m id o)]-2-n it r oet h ylen e (19). The title compound
was obtained as previously described for the compound 17 by
starting from 10 (1.0 g, 3.5 mmol) and 1-cyclooctylamino-1-
X-r a y Cr ysta llogr a p h y. Crystals of 17, C21
451.6, were obtained by slow evaporation of a concentrated
solution in EtOH/MeOH and studied by crystallography:
monoclinic, P2 /c, a ) 10.606(2) Å, b ) 13.231(3) Å, c )
6.776(2) Å, â ) 102.67(2)°, V ) 2296.8 Å , Z ) 4, µ ) 15.6
33 5 4 r
H N O S, M
methylsulfanyl-2-nitroethylene 8 (1.0 g, 4.1 mmol): yield 58%
)
1
(
1
(
6
1.00 g); mp 164-166 °C; H NMR (DMSO-d
6
, 300 MHz) δ
), 7.10
d, 1H, 5H-pyridine), 7.44 (d, 1H, pyridine-NH), 8.27 (d, 1H,
H-pyridine), 8.57 (s, 1H, 2H-pyridine), 10.39 (d, 1H, NH-cyclo-
octyl). Anal. (C23 S) C, H, N, S.
-Cycloh exylam in o-1-[4′-(3′′-m eth ylph en ylam in o)pyr id-
′-ylsu lfon a m id o]-2-n itr oeth ylen e (20). The title com-
pound was obtained as previously described for the compound
7 by starting from 10 (0.5 g, 1.9 mmol) and 1-cyclohexyl-
amino-1-methylsulfanyl-2-nitroethylene 8 (0.5 g, 2.3 mmol):
.10-1.93 (m, 30H, two cyclooctyl), 6.68 (s, 1H, CH-NO
2
1
3
1
-1
-3
cm , D
x
) 1.3060(5) g cm , λ(Cu KR) ) 1.54178 Å, F(000) )
68.0, T ) 290 K, 4503 unique reflections, R1 ) 0.0671 for
817 F > 4σ(F ) and wR2 ) 0.1677, GOF ) S ) 0.835.
Molecu la r Mod elin g. Internal geometries were optimized
by molecular mechanics (MM) with the Discover program
MSI, San Diego) using the cff91 Force Field. Those param-
eters reproduce well both ab initio optimized (LCAO-MO,
-21G*) and experimental (X-ray) geometries. Calculations
37 5 4
H N O
9
1
1
o
o
3
1
(
1
yield 25% (0.21 g); mp 144-146 °C; H NMR (DMSO-d
MHz) δ 0.98-1.85 (m, 11H, cyclohexyl), 2.34 (s, 3H, aryl-CH
.87 (s, 1H, CH-NO ), 7.01-7.45 (m, 5H, phenyl and 5H-
pyridine), 8.26 (d, 1H, 6H-pyridine), 8.59 (s, 1H, 2H-pyridine),
.45 (b, 1H, pyridine-NH), 10.33 (d, 1H, NH-cyclohexyl). Anal.
S) C, H, N, S.
-Isop r op yla m in o-1-[(4′-eth yla m in o)p yr id -3′-ylsu lfon -
6
, 300
3
3
),
were performed on the neutral (nonzwitterionic) form of 17.
Theoretical values of the starting geometries for the R, â, γ,
6
2
5
and δ conformations were taken from the literature. Those
9
geometries were optimized to a final RMS deviation of 0.01
kcal/mol.
20 25 5 4
(C H N O
1
Ma xim a l Electr osh ock Seizu r es Test. Each compound
was intraperitoneally injected to OF1 male mice (22-25 g; Iffa-
Credo, Les Oncins, France) at a dose volume of 10 mL/kg. At
the desired time, an electrical stimulus (50 mA; 60 Hz) was
delivered for 0.2 s through corneal electrodes. Protection
a m id o]-2-n itr oeth ylen e (21). The title compound was ob-
tained as previously described for compound 17 by starting
from 10 (0.7 g, 3.5 mmol) and 1-isopropylamino-1-methyl-
sulfanyl-2-nitroethylene 8 (0.7 g, 4.0 mmol): yield 37% (0.41
g); mp 163-164 °C; H NMR (DMSO-d
6
1
7
1
1
6
, 300 MHz) δ 1.04 (2s,
), 3.40 (m, 2H, CH ), 4.01 (m,
), 7.08 (d, 1H, 5H-pyridine),
.70 (m, 1H, pyridine-NH), 8.21 (d, 1H, 6H-pyridine), 8.57 (s,
H,2H-pyridine),10.10(d,1H,NH-isopropyl). Anal. (C12 S)
against seizures was defined as the abolition of the hind limb
H, C(CH
3
)
2
), 1.23 (1s, 3H, CH
3
2
tonic extension.9
,19
The preliminary screening (Table 1) was
H, CH<), 6.70 (s, 1H, CH-NO
2
conducted with groups of six or seven mice at an intra-
peritoneal dose of 30 mg/kg. The electroshock was applied at
.5 or 3 h after injection. The time-course activity of 17 was
19 5 4
H N O
0
C, H, N, S.
measured after injection of 30 mg/kg. The effective dose
protecting 50% of mice (ED50) was determined by treating
groups of eight mice with varying doses at the time of peak
effect. The ED50 and 95% confidence intervals were computed
by using the method of Litchfield and Wilcoxon.2
1
-Isop r op yla m in o-1-[(4′-cyclop en tyla m in o)p yr id -3′-yl-
su lfon a m id o)]-2-n it r oet h ylen e (22). The title compound
was obtained as previously described for compound 17 by
starting from 10 (0.7 g, 2.9 mmol) and 1-isopropylamino-1-
5
methylsulfanyl-2-nitroethylene 8 (0.6 g, 3.4 mmol): yield 25%
1
Ch em ica lly In d u ced Seizu r es. Pentetrazole (85 mg/kg),
strychnine (1.20 mg/kg), picrotoxin (3.15 mg/kg), and NMLDA
340 mg/kg) were dissolved in 0.9% NaCl (10 mg/kg). Bicu-
(
0.27 g); mp 172-173 °C; H NMR (DMSO-d
6
, 300 MHz) δ 1.10
(
2s, 6H, C(CH
3
)
2
), 1.23-1.90 (m, 9H, cyclopentyl), 2.05 (m, 1H,
), 7.20 (d, 1H, 5H-pyridine), 7.50
d, 1H, pyridine-NH), 8.25 (d, 1H, 6H-pyridine), 8.58 (s, 1H,
(
CH<), 6.75 (s, 1H, CH-NO
2
culline (2.70 mg/kg) was dissolved in warmed 0.1 N HCl and
0.9% NaCl (10 mL/kg) and used within 30 min after prepara-
tion. The proconvulsive chemicals (pentetrazole, strychnine,
bicuculline, picrotoxin, and NMLDA) were administered sub-
cutaneously at the time of peak effect obtained in the MES
(
2
23 5 4
H-pyridine),10.15(d,1H,NH-cyclopentyl). Anal. (C15H N O S)
C, H, N, S.
-Isop r op yla m in o-1-[4′-(3′′-m eth ylp h en yla m in o)p yr id -
′-ylsu lfon a m id o]-2-n itr oeth ylen e (23). The sodium salt
1
3
9
,19,26
5
,15
test and the anticonvulsant activity measured as described.
of 4-(3′-methylphenylamino)pyrid-3-ylsulfonamide 10
(1.09
The ED50 and 95% confidence intervals were computed by
g, 3.8 mmol) and 0.75 g (4.3 mmol) of 1-isopropylamino-1-
methylsulfanyl-2-nitroethylene 8 were dissolved in a mixture
of 1,4-dioxane (3 mL) and N,N-dimethylformamide (2 mL) and
refluxed for 4 h. After evaporation of solvents under reduced
pressure the residue was dissolved in water (50 mL) and 2.5
using the method of Litchfield and Wilcoxon.25
Neu r otoxicity. Neurotoxicity was defined as the failure
of an intraperitoneally treated mouse to maintain its equilib-
rium on rod rotating (6 rpm).9
,20
The determination of the

3
244 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 17
Masereel et al.
median toxic dose (TD50) and confidence intervals were cal-
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culated as mentioned previously.25
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0
.1%) was orally administered in male rats (Wistar 193-229
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