Synthesis and potential anticonvulsant activity of new N-3-substituted 5,5-cyclopropanespirohydantoins

Article abstract of DOI:10.1016/j.ejmech.2008.02.024

Thirteen new 5-cyclopropanespirohydantoins with various N-3 substituents were synthesized and their pharmacological activity was determined with the objective to better understand their structure-activity relationship (SAR) for anticonvulsant activity. Th

Full text of DOI:10.1016/j.ejmech.2008.02.024

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European Journal of Medicinal Chemistry 44 (2009) 296e302
http://www.elsevier.com/locate/ejmech
Original article
Synthesis and potential anticonvulsant activity of new N-3-substituted
5,5-cyclopropanespirohydantoins
Qifeng Zhu, Yuanhu Pan, Zaixu Xu, Ruimin Li, Guofu Qiu, Wenjin Xu, Xianbing Ke,
*
Lamei Wu, Xianming Hu
State Key Laboratory of Virology, College of Pharmacy, Wuhan University, Wuhan 430072, China
Received 12 November 2007; received in revised form 2 January 2008; accepted 25 February 2008
Available online 7 March 2008
Abstract
Thirteen new 5-cyclopropanespirohydantoins with various N-3 substituents were synthesized and their pharmacological activity was deter-
mined with the objective to better understand their structureeactivity relationship (SAR) for anticonvulsant activity. The anticonvulsant effects
of these compounds were evaluated by maximal electroshock seizure (MES) test and subcutaneous pentylenetetrazole (scPTZ) test models in
mice. All compounds substituted with cyclopropyl group at fifth position of hydantoin ring showed better protection against MES test.
Compounds 5b, 5d, 5e, 5g and 5j were found to be the most potent compounds of this series and compared with the reference drug phenytoin
sodium in MES test. Compound 5j also showed equipotent activity with the standard drug sodium valproate at the doses of 20 and 40 mg kgꢀ1 in
scPTZ test.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Cyclopropanespirohydantoin; Anticonvulsant activity; Maximal electroshock seizure test; Pentylenetetrazole test
1. Introduction
analogs, such as 5,5-cyclopentanespirohydantoins [12], 5,5-
cyclohexanespirohydantoins [13], 5,5-cycloheptanespirohy-
dantoins [14], and 5,5-cyclooctanespirohydantoins [14], have
been synthesized and shown to have anticonvulsant activity.
In this paper, we set out to modify hydantoin by introducing
a three-membered ring to obtain spirocyclopropanated hydan-
toin analogs and examine their anticonvulsant activities by
electroshock (MES test) and PTZ (scPTZ test). It was
especially of great interest to see, whether the introduction
of a spiroannelated cyclopropane ring, which is known for
its alkene-like properties [15,16], causes any effect upon bio-
logical activities. The pharmacological activity of various N-3
substituted 5,5-cyclopropanespirohydantoins can help better
understand their structureeactivity relationship (SAR).
Epilepsy is a major neurological disorder affecting a large
section of people both male and female throughout the world.
Currently available drugs for the treatment of epilepsy are
symptomatically effective in only 60e70% of patients [1].
In recent times several new drugs such as topiramate [2], tia-
gabine [3], felbamate [4], zonisamide [5], and vigabatrin [6]
have emerged to treat epilepsy. Although these drugs have
been shown to be effective in controlling the seizures, their ef-
ficacy does not appear to be superior to that of the established
antiepileptic drugs (e.g. diphenylhydantoin, carbamazepine,
valproate) [1]. Therefore, it is essential to search for new
chemical entities for the treatment of epilepsy with greater
efficacy and fewer side effects. Most of the compounds with
anticonvulsant activity contain a cyclic ureide ring system
[7]. Then many hydantoin [8] and spirohydantoin [9e11]
2. Chemistry
The synthetic routes of compounds are outlined in Scheme 1.
Diethyl 2,2-dimethylcyclopropane-1,1-dicarboxylate 1 was
synthesized by a Michael initiated ring closure (MIRC) reaction
* Corresponding author.
E-mail address: xmhu@whu.edu.cn (X. Hu).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.02.024

Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
297
Scheme 1.
according to our previous studies [17,18]. Then monoester 2
was obtained after monosaponification in a 1 N NaOH/ethanol
(1.1 equiv) solution at room temperature for 12 h [18,19]. This
was then converted to corresponding acyl azide by using ethyl
chloroformate in the presence of N-methyl morpholine
(NMM) followed by reaction with sodium azide in a one-pot
synthesis. a-Carboethoxy isocyanate 3 was successfully gener-
ated by a Curtius reaction in situ on heating the acyl azide in tol-
uene solution at 75 ꢁC. Isocyanate 3 was allowed to react
directly with various amines without isolation. The desired a-
carboethoxy ureas 4 were readily obtained. However, no obvi-
ous reaction was observed between the aromatic amines with
strongly electron-withdrawing groups like nitro and methoxyl-
carbonyl and isocyanate 3 under the same condition. Attempts
to promote the reaction by prolonging the reaction time (24 h)
failed, presumably due to the weak nucleophilic attack of aro-
matic amines with strongly electron-withdrawing groups. Nev-
ertheless, the reactions would be carried out fast when the
catalytic amount of 4-methylbenzenesulfonic acid was added.
The proposed reaction mechanism is shown in Scheme 2. The
carbonyl of isocyanate can be activated by the form of the active
carbon cation in the presence of acid, which can also react with
the aromatic amines with strongly electron-withdrawing groups
by the nucleophilic attack.
same condition did not give the desired compound, but in-
stead, afforded the hydrolysis of methyl ester. Although exces-
sive amounts of Na (2 or 5 or 10 equiv) were attempted,
similar results were obtained.
All of these compounds were prepared as racemic mixtures
and no attempt was made to resolve the enantiomers.
3. Pharmacological results and discussion
The anticonvulsant activities of the synthesized compounds
were determined by in vivo test. The pharmacological data of
all the compounds of this series have been reported in Table 1.
These compounds when screened for their anticonvulsant ac-
tivity against maximal electroshock induced seizures tested
at 30 mg kgꢀ1 p.o., exhibited substantive anticonvulsant activ-
ity. The characteristic feature of this series is the presence of
the substituted cyclopropyl group at fifth position and the dif-
ferent substituted group at third position of hydantoin ring.
While evaluating the anticonvulsant activity, it was observed
that all compounds 5aem, substituted with different alkyl
and aryl at third position of hydantoin ring, have shown vary-
ing degrees (50e90% protection) of anticonvulsant activity.
Compounds 5b, 5d, 5e, 5g and 5j have shown most potent re-
sponse against MES test i.e. 90 and 80% protection. Among
the N-3-alkyl-substituted hydantoins, methyl substituent
(5b), hydroxy alkyl substituent (5e) and the straight chain bu-
tyl substituent (5d) have shown more potent response in com-
parison to other substituted derivatives. When the alkyl group
Finally, those N,N0-asymmetric ureas (4aek and 4m) cy-
clized on treatment with Na (1 equiv) in EtOH and provided
30-substituted spirohydantoins 5 with a cyclopropane ring in
good yields (yield ꢂ 92%). The reaction of urea 4l under the
Scheme 2.

298
Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
the dose of 7.5 mg kgꢀ1, equipotent at the dose of 15 mg kgꢀ1
while less potent activity at 30 mg kgꢀ1 p.o. than the standard
drug phenytoin sodium. Compound 5g showed equipotent an-
ticonvulsant activity at the dose of 7.5 mg kgꢀ1 with the stan-
dard drug phenytoin sodium while less potent activity at the
doses of 30 and 15 mg kgꢀ1 p.o.
Table 1
Pharmacological data of compounds 5aek and 5m
Compounds
Dose
(mg kgꢀ1 p.o.)
Anticonvulsant activity
(% inhibition)
For MES
model
For PTZ
model
For MES
model
For PTZ
model
5a
5b
30
30
15
7.5
30
30
15
7.5
30
15
7.5
30
30
15
7.5
30
30
30
15
7.5
30
30
0.2 mL
30
15
7.5
e
e
50*
90***
50*
40
e
60**
30
Therefore, considering the results of these compounds, it
may be concluded that compounds 5b, 5d and 5e have shown
more potent and equipotent activity as the standard drug phe-
nytoin sodium while compounds 5g and 5j have shown equi-
potent and less activity than the standard drug phenytoin
sodium in MES test.
Being the most potent compounds of this series, com-
pounds 5b, 5d, 5e, 5g and 5j were also tested for PTZ model
and compared with reference drug sodium valproate. Com-
pounds 5b, 5e, and 5g have shown less activity at all three
doses (20, 40 and 80 mg kgꢀ1) than the standard drug sodium
valproate. However, compound 5j has shown equipotent re-
sponse at the doses of 20 and 40 mg kgꢀ1 (i.e. 30 and 50% in-
hibition) and lower degree of protection (i.e. 70% inhibition)
at the dose of 80 mg kgꢀ1 than the reference drug sodium val-
proate. Compound 5d has been found to exhibit less potent re-
sponse at the doses of 40 and 80 mg kgꢀ1 (i.e. 40 and 60%
inhibition, respectively) and equipotent effect (i.e. 30% inhibi-
tion) at the dose of 20 mg kgꢀ1 (Table 1) in the PTZ model.
80
40
20
e
80
40
20
80
40
20
e
20
5c
5d
70**
90***
50*
20
e
60**
40
30
5e
90***
50*
30
70**
40
20
5f
5g
70**
80***
40
e
60**
40
80
40
20
e
20
20
5h
5i
50*
60**
80***
50*
30
e
e
e
5j
80
40
20
e
70**
50*
30
5k
5m
C.C.a
Phenytoin sodiumb
50*
60**
0
e
e
0.2 mL
e
e
0
90***
50*
20
e
e
e
4. Conclusion
e
e
Sodium valproatec
80
40
20
e
e
80***
50*
30
Considering the results of all the synthesized compounds,
the following may be concluded.
e
e
e
*P < 0.05; **P < 0.01; ***P < 0.001.
a
ꢃ All of the compounds substituted with cyclopropyl group
at fifth position of hydantoin ring showed better protection
against MES test but less response toward scPTZ test.
ꢃ Unbranched (i.e. 5b and 5d) and hydroxy (i.e. 5e) alkyl
substituents showed promising anticonvulsant activity in
MES test.
ꢃ p-Fluorophenyl compound (i.e. 5j) substituted at the third
position of hydantoin ring showed more promising results
than the other phenyl-substituted ones in both MES and
scPTZ tests.
0.5% Carboxymethyl cellulosee0.9% saline standard for control group.
Standard drug for MES pattern test.
Standard drug for PTZ seizure pattern test.
b
c
at the N-3 position was replaced by a phenyl ring, substitution
of a small lipophilic group like fluorine (5j) at the para posi-
tion of the N-3-phenyl ring of 5g resulted in increased activity,
which is in agreement with the reported SAR for spirohydan-
toins [11]. However, substitution with dichloro group (5k) at
the 30- and 50-position of the N-3-phenyl ring of 5g resulted
in decreased activity. Electron-donating group like methoxy
(5i) and strongly electron-withdrawing group like nitro (5m)
at the 4-position of the phenyl ring cause a decrease in activity
compared to 5g in MES test. From the above results, it is ob-
vious that among the N-3-phenyl-substituted derivatives, com-
pounds 5j and 5g have shown more potent response in
comparison to other compounds.
In the MES model, compounds 5b, 5d, 5e, 5g and 5j were
also tested at three graded doses i.e. 7.5, 15 and 30 mg kgꢀ1
p.o. Compounds 5b, 5d and 5e showed equipotent anticonvul-
sant activity as compared to standard drug phenytoin sodium
at the doses of 30 and 15 mg kgꢀ1 p.o. whereas compounds
5b and 5e showed more potent activity but compound 5d
showed equipotent activity at the dose of 7.5 mg kgꢀ1 p.o.
Compound 5j showed more potent anticonvulsant activity at
5. Experimental
5.1. Chemistry
Reagents were purchased from commercial sources. Sol-
vents and reagents were dried and purified according to the lit-
erature methods. Melting points were uncorrected and
measured on an XT-4 apparatus. IR spectra were recorded
from KBr pellets at a range of 400e4000 cmꢀ1 on a Per-
1
kineElmer (Spectrum One) spectrometer. H and 13C NMR
spectra were obtained on a Varian Mercury VX300 apparatus
in DMSO-d6 and CDCl3 with TMS as internal standard. The
elemental analysis (C, H, N) data were obtained from a Vari-
oEL III (German) elemental analyzer.

Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
299
1
5.1.1. The synthesis of 1-(ethoxycarbonyl)-2,2-
dimethylcyclopropanecarboxylic acid 2
(KBr, cmꢀ1): 3350 (NeH), 1724 (C]O), 1651 (C]O). H
NMR (300 MHz, CDCl3): d 0.91 (d, 1H, J ¼ 2.4 Hz, Cpre
H), 1.15 (s, 3H, eCH3), 1.23 (t, 3H, J ¼ 7.2 Hz, eCH3),
1.25 (s, 3H, eCH3), 1.67 (d, 1H, J ¼ 2.4 Hz, CpreH), 2.77
(d, 3H, J ¼ 2.4 Hz, CH3), 4.16 (q, 2H, J ¼ 7.2 Hz, CH2),
4.87 (br s, 1H, NH), 5.21 (s, 1H, NH). MS (m/z): 237
[M þ Na]. Anal. Calcd for C10H18N2O3: C, 56.06; H, 8.47;
N, 13.07; Found: C, 55.98; H, 8.52; N, 12.96%.
To a solution of diethyl 2,2-dimethylcyclopropane-1,1-di-
carboxylate 1 (4.8 g, 22 mmol) in EtOH (25 mL) was added
1 N sodium hydroxide (25 mL, 1.1 equiv, 25 mmol), and the
resulting mixture was stirred at room temperature for 12 h.
EtOH was removed under reduced pressure, water was added
to the residue, and the mixture was acidified by means of a sat-
urated KHSO4 solution and extracted with ethyl acetate
(3 ꢄ 30 mL). The combined extracts were dried over
Na2SO4 and evaporated to give product 2 (3.75 g, 90%) as
a colorless oil: IR (KBr, cmꢀ1): 2983 (OeH), 1732 (C]O),
5.1.2.3. Ethyl 2,2-dimethyl-1-(3-isopropylureido) cyclopropa-
necarboxylate (4c). White solid (63%); Mp: 137e139 ꢁC. IR
(KBr, cmꢀ1): 3370 (NeH), 1723 (C]O), 1646 (C]O). H
1
1
1698 (C]O). H NMR (300 MHz, CDCl3): d 1.25 (s, 3H, e
NMR (300 MHz, CDCl3): d 0.89 (d, 1H, J ¼ 2.7 Hz, Cpre
H), 1.12 (s, 3H, eCH3), 1.13 (s, 3H, eCH3), 1.16e1.22 (m,
6H, 2-CH3), 1.24 (t, 3H, J ¼ 5.1 Hz, eCH3), 1.66 (d, 1H,
J ¼ 2.7 Hz, CpreH), 3.90e3.95 (m, 1H, CH), 4.14e4.17 (m,
2H, CH2), 4.61 (br s, 1H, NH), 4.99 (br s, 1H, NH). 13C
NMR (150 MHz, CDCl3): d 14.54, 20.08, 21.81, 23.52,
23.58, 28.20, 42.26, 43.45, 61.62, 158.11, 171.98. MS (m/z):
265 [M þ Na]. Anal. Calcd for C12H22N2O3: C, 59.48; H,
9.15; N, 11.56; Found: C, 59.25; H, 9.33; N, 11.64%.
CH3), 1.33 (t, 3H, J ¼ 7.2 Hz, eCH3), 1.38 (s, 3H, eCH3),
1.78 (s, 1H, CpreH), 1.85 (s, 1H, CpreH), 4.29 (q, 2H,
J ¼ 7.2 Hz, CH2), 11.28 (br s, 1H, OH). 13C NMR
(150 MHz, CDCl3): d 13.92, 20.75, 21.66, 26.94, 33.50,
38.54, 62.08, 171.30, 181.29.
5.1.2. General procedure for the synthesis of N,N0-
asymmetric ureas 4aem
Compound 2 (10 mmol) was dissolved in dry THF (30 mL)
and cooled to e15 ꢁC. After the addition of EtOCOCl
(11 mmol) and NMM (12 mmol), the mixture was stirred for
20 min. A solution of NaN3 (25 mmol) in H2O was added
and stirred for 1 h at e10 ꢁC. The solution was then diluted
with H2O and extracted with EtOAc. The organic layers
were washed with brine, dried over Na2SO4 and concentrated
under reduced pressure to give crude acyl azide. This crude
acyl azide could be further purified by a flash column chroma-
tography (PEeEtOAc, 4:1, Rf ¼ 0.7). Purified acyl azide was
dissolved in toluene (30 mL) and the resulting solution was
heated to 75 ꢁC under stirring. After gas evolution had stopped
toluene was removed under reduced pressure to afford a-car-
boethoxy isocyanate 3 as clear oil. This a-carboethoxy isocy-
anate 3 was directly used in the next step without further
purification. Amine (10 mmol) was added to a stirred suspen-
sion of isocyanate 3 in appropriate solvent (40 mL) at r.t.
(when highly reactive amines were used, they should be dis-
solved in solvent and added dropwise). The solvent was re-
moved under reduced pressure when the reaction was
completed (detected by TLC) and the products 4 were purified
by a column chromatography.
5.1.2.4. Ethyl 2,2-dimethyl-1-(3-butylureido) cyclopropanecar-
boxylate (4d). White solid (80%); Mp: 70e72 ꢁC. IR (KBr,
1
cmꢀ1): 3364 (NeH), 1724 (C]O), 1640 (C]O). H NMR
(300 MHz, CDCl3): d 0.91e0.94 (m, 3H, CH3), 0.95 (d, 1H,
J ¼ 4.5 Hz, CpreH), 1.20 (s, 3H, eCH3), 1.30 (s, 3H, e
CH3), 1.26e1.30 (m, 3H, eCH3), 1.33e1.41 (m, 2H, e
CH2), 1.44e1.52 (m, 2H, eCH2), 1.71 (d, 1H, J ¼ 4.5 Hz,
CpreH), 3.18e3.27 (m, 2H, CH2), 4.19 (q, 2H, J ¼ 7.2 Hz,
CH2), 4.86 (br s, 1H, NH), 5.09 (br s, 1H, NH). 13C NMR
(150 MHz, CDCl3): d 13.99, 14.49, 20.10, 20.16, 21.84,
28.21, 32.54, 40.15, 43.45, 61.51, 158.95, 172.16. MS (m/z):
279 [M þ Na]. Anal. Calcd for C13H24N2O3: C, 60.91; H,
9.44; N, 10.93; Found: C, 61.15; H, 9.35; N, 10.64%.
5.1.2.5. Ethyl 2,2-dimethyl-1-[3-(1-hydroxybutan-2-yl) ureido]
cyclopropanecarboxylate (4e). White solid (63%); Mp: 75e
77 ꢁC. IR (KBr, cmꢀ1): 3373 (NeH), 1708 (C]O), 1668
(C]O). 1H NMR (300 MHz, CDCl3): d 0.90 (d, 1H,
J ¼ 7.2 Hz, CpreH), 0.95 (t, 3H, J ¼ 4.8 Hz, eCH3), 1.12
(s, 6H, 2-CH3), 1.26 (t, 3H, eCH3), 1.40e1.58 (m, 2H,
CH2), 1.70 (d, 1H, J ¼ 7.2 Hz, CpreH), 3.51e3.54 (m, 3H,
eCH2, eCH), 3.63 (br s, 1H, OH), 4.16 (q, 2H, J ¼ 7.2 Hz,
CH2), 5.39 (br s, 1H, NH), 5.86 (br s, 1H, NH). 13C NMR
(150 MHz, CDCl3): d 10.80, 14.49, 20.13, 22.00, 24.76,
28.35, 28.45, 43.48, 54.58, 61.70, 66.52, 160.02, 172.51. MS
(m/z): 295 [M þ Na]. Anal. Calcd for C13H24N2O4: C, 57.33;
H, 8.88; N, 10.29; Found: C, 57.21; H, 9.03; N, 10.44%.
5.1.2.1. Ethyl 2,2-dimethyl-1-ureidocyclopropanecarboxylate
(4a). White solid (52%); Mp: 127e129 ꢁC. IR (KBr, cmꢀ1):
3355 (NeH), 1704 (C]O), 1658 (C]O). 1H NMR
(300 MHz, CDCl3): d 0.98 (d, 1H, J ¼ 4.6 Hz, CpreH), 1.20
(s, 3H, eCH3), 1.27 (t, 3H, J ¼ 7.2 Hz, eCH3), 1.29 (s, 3H,
eCH3), 1.72 (d, 1H, J ¼ 4.6 Hz, CpreH), 4.19 (q, 2H,
J ¼ 7.2 Hz, CH2), 4.97e5.01 (m, 2H, NH), 5.62 (br s, 1H,
NH). MS (m/z): 223 [M þ Na]. Anal. Calcd for C9H16N2O3:
C, 53.98; H, 8.05; N, 13.99; Found: C, 54.05; H, 7.83; N,
14.18%.
5.1.2.6. Ethyl 2,2-dimethyl-1-(3-benzylureido) cyclopropane-
carboxylate (4f). White solid (54%); Mp: 110e112 ꢁC. IR
1
(KBr, cmꢀ1): 3348 (NeH), 1721 (C]O), 1638 (C]O). H
NMR (300 MHz, CDCl3): d 0.77 (d, 1H, J ¼ 4.5 Hz, Cpre
H), 1.11 (s, 3H, eCH3), 1.17 (t, 3H, J ¼ 7.2 Hz, eCH3),
1.20 (s, 3H, eCH3), 1.49 (d, 1H, J ¼ 4.5 Hz, CpreH), 4.06
(q, 2H, J ¼ 7.2 Hz, CH2), 4.14 (dd, 1H, J ¼ 15.3 Hz,
5.1.2.2. Ethyl 2,2-dimethyl-1-(3-methylureido) cyclopropane-
carboxylate (4b). White solid (58%); Mp: 133e135 ꢁC. IR

300
Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
J ¼ 5.1 Hz, CH2), 4.28 (dd, 1H, J ¼ 15.3 Hz, J ¼ 6.6 Hz,
CH2), 6.41 (s, 1H, NH), 6.62 (s, 1H, NH), 7.19e7.33 (m,
5H, AreH). 13C NMR (150 MHz, CDCl3): d 14.49, 20.04,
21.89, 28.39, 43.40, 44.33, 61.68, 127.42, 127.49, 128.76,
139.50, 158.83, 172.05. MS (m/z): 313 [M þ Na]. Anal. Calcd
for C16H22N2O3: C, 66.18; H, 7.64; N, 9.65; Found: C, 66.02;
H, 7.73; N, 9.92%.
1H, NH), 6.91e6.97 (m, 2H, AreH), 7.08 (s, 1H, NH),
7.26e7.29 (m, 2H, AreH). 13C NMR (150 MHz, CDCl3):
d 14.51, 20.20, 22.06, 28.28, 28.56, 43.50, 61.88, 115.95,
122.35, 134.61, 156.58, 160.92, 172.59. MS (m/z): 317
[M þ Na]. Anal. Calcd for C15H19FN2O3: C, 61.21; H, 6.51;
N, 9.52; Found: C, 61.05; H, 6.33; N, 9.64%.
5.1.2.11. Ethyl 2,2-dimethyl-1-[3-(3,5-dichlorophenyl) ureido]
cyclopropanecarboxylate (4k). White solid (53%); Mp:
163e165 ꢁC. IR (KBr, cmꢀ1): 3364 (NeH), 1723 (C]O),
5.1.2.7. Ethyl 2,2-dimethyl-1-(3-phenylureido) cyclopropane-
carboxylate (4g). White solid (55%); Mp: 153e155 ꢁC. IR
1
1
(KBr, cmꢀ1): 3375 (NeH), 1725 (C]O), 1651 (C]O). H
1653 (C]O). H NMR (300 MHz, CDCl3): d 1.06 (d, 1H,
NMR (300 MHz, DMSO-d6): d 0.94 (d, 1H, J ¼ 5.1 Hz,
CpreH), 1.21 (s, 3H, eCH3), 1.25 (t, 3H, J ¼ 7.2 Hz, e
CH3), 1.29 (s, 3H, eCH3), 1.72 (d, 1H, J ¼ 5.1 Hz, CpreH),
4.14 (q, 2H, J ¼ 7.2 Hz, CH2), 6.55 (s, 1H, NH), 6.89e6.94
(m, 1H, AreH), 7.18e7.23 (m, 2H, AreH), 7.39e7.42 (m,
2H, AreH), 8.27 (s, 1H, NH). MS (m/z): 299 [M þ Na].
Anal. Calcd for C15H20N2O3: C, 65.20; H, 7.30; N, 10.14;
Found: C, 65.31; H, 7.46; N, 9.88%.
J ¼ 5.1 Hz, CpreH), 1.26 (s, 3H, eCH3), 1.28 (s, 3H, e
CH3), 1.30 (t, 3H, J ¼ 6.9 Hz, eCH3), 1.87 (d, 1H,
J ¼ 5.4 Hz, CpreH), 4.26 (q, 2H, J ¼ 6.2 Hz, CH2), 6.21 (s,
1H, NH), 6.90e7.22 (m, 3H, AreH), 7.38 (s, 1H, NH). 13C
NMR (150 MHz, CDCl3): d 14.46, 20.39, 22.30, 28.28,
28.88, 43.43, 62.43, 117.17, 122.80, 135.13, 140.73, 155.80,
164.59. MS (m/z): 368 [M þ Na]. Anal. Calcd for
C15H18Cl2N2O3: C, 52.19; H, 5.26; N, 8.11; Found: C,
52.22; H, 5.18; N, 8.02%.
5.1.2.8. Ethyl 2,2-dimethyl-1-[3-(4-methylphenyl) ureido] cy-
clopropanecarboxylate (4h). White solid (57%); Mp: 120e
122 ꢁC. IR (KBr, cmꢀ1): 3342 (NeH), 1728 (C]O), 1654
(C]O). 1H NMR (300 MHz, CDCl3): d 0.82 (d, 1H,
J ¼ 5.1 Hz, CpreH), 1.14 (s, 3H, eCH3), 1.14 (t, 3H,
J ¼ 7.2 Hz, eCH3), 1.24 (s, 3H, eCH3), 1.54 (d, 1H,
J ¼ 5.1 Hz, CpreH), 2.21 (s, 3H, CH3), 4.01e4.12 (m, 2H,
CH2), 6.71 (s, 1H, NH), 7.03 (d, 2H, J ¼ 8.4 Hz, AreH),
7.26 (d, 2H, J ¼ 8.4 Hz, AreH), 8.41 (s, 1H, NH). 13C
NMR (150 MHz, CDCl3): d 14.52, 20.12, 21.01, 22.12,
28.22, 28.66, 43.45, 61.70, 120.97, 129.81, 133.40, 136.06,
156.90, 172.42. MS (m/z): 313 [M þ Na]. Anal. Calcd for
C16H22N2O3: C, 66.18; H, 7.64; N, 9.65; Found: C, 66.36;
H, 7.42; N, 9.49%.
5.1.2.12. Ethyl 2,2-dimethyl-1-[3-(4-methoxycarbonylphenyl)
ureido] cyclopropanecarboxylate (4l). White solid (45%);
Mp: 159e161 ꢁC. IR (KBr, cmꢀ1): 3391 (NeH), 1712
(C]O), 1687 (C]O). 1H NMR (300 MHz, DMSO-d6):
d 1.04 (d, 1H, J ¼ 5.1 Hz, CpreH), 1.23 (s, 3H, eCH3),
1.27 (s, 3H, eCH3), 1.26 (s, 3H, eCH3), 1.83 (d, 1H,
J ¼ 5.1 Hz, CpreH), 3.86 (s, 3H, CH3), 4.18e4.25 (m, 2H,
CH2), 7.36 (d, 2H, AreH), 7.85 (d, 2H, AreH). 13C NMR
(150 MHz, DMSO-d6): d 14.94, 20.27, 22.67, 27.28, 29.11,
42.86, 52.43, 61.13, 117.46, 122.61, 131.09, 145.46, 155.78,
166.64, 172.11. MS (m/z): 357 [M þ Na]. Anal. Calcd for
C17H22N2O5: C, 61.07; H, 6.63; N, 8.38; Found: C, 59.86;
H, 6.83; N, 8.21%.
5.1.2.9. Ethyl 2,2-dimethyl-1-[3-(4-methoxyphenyl) ureido] cy-
clopropanecarboxylate (4i). White solid (60%); Mp: 123e
125 ꢁC. IR (KBr, cmꢀ1): 3374 (NeH), 1725 (C]O), 1653
(C]O). 1H NMR (300 MHz, CDCl3): d 1.02 (d, 1H,
J ¼ 2.4 Hz, CpreH), 1.20 (s, 3H, eCH3), 1.26 (t, 3H,
J ¼ 3.6 Hz, eCH3), 1.24 (s, 3H, eCH3), 1.79 (d, 1H,
J ¼ 2.4 Hz, CpreH), 3.76 (s, 3H, CH3), 4.18 (q, 2H,
J ¼ 3.6 Hz, CH2), 5.69 (s, 1H, NH), 6.81 (d, 2H, J ¼ 3.9 Hz,
AreH), 7.03 (s, 1H, NH), 7.22 (d, 2H, J ¼ 3.9 Hz, AreH).
13C NMR (150 MHz, CDCl3): d 9.76, 15.34, 17.36, 23.33,
23.93, 38.65, 50.92, 56.86, 109.76, 118.52, 126.80, 151.77,
152.40, 167.68. MS (m/z): 329 [M þ Na]. Anal. Calcd for
C16H22N2O4: C, 62.73; H, 7.24; N, 9.14; Found: C, 62.55;
H, 7.36; N, 9.32%.
5.1.2.13. Ethyl 2,2-dimethyl-1-[3-(4-nitrylphenyl) ureido] cy-
clopropanecarboxylate (4m). Pale yellow solid (43%); Mp:
166e168 ꢁC. IR (KBr, cmꢀ1): 3385 (NeH), 1693 (C]O),
1605 (C]O). 1H NMR (300 MHz, DMSO-d6): d 0.84 (d,
1H, J ¼ 5.1 Hz, CpreH), 1.13 (t, 3H, J ¼ 7.2 Hz, eCH3),
1.14 (s, 3H, CH3), 1.23 (s, 3H, CH3), 1.54 (d, 1H,
J ¼ 5.1 Hz, CpreH), 4.60 (q, 2H, J ¼ 5.1 Hz, CH2), 7.07 (s,
1H, NH), 7.60 (d, 2H, AreH), 8.12 (d, 2H, AreH), 9.32 (s,
1H, NH). 13C NMR (150 MHz, DMSO-d6): d 14.92, 20.21,
22.67, 27.40, 29.10, 42.88, 61.14, 117.62, 125.83, 141.30,
147.42, 155.56, 171.96. MS (m/z): 344 [M þ Na]. Anal. Calcd
for C15H19N3O5: C, 56.07; H, 5.96; N, 13.08; Found: C, 55.89;
H, 6.08; N, 12.84%.
5.1.2.10. Ethyl 2,2-dimethyl-1-[3-(4-fluorophenyl) ureido] cy-
clopropanecarboxylate (4j). White solid (30%); Mp: 125e
127 ꢁC. IR (KBr, cmꢀ1): 3352 (NeH), 1711 (C]O), 1670
(C]O). 1H NMR (300 MHz, CDCl3): d 1.04 (d, 1H,
J ¼ 5.4 Hz, CpreH), 1.22 (s, 3H, eCH3), 1.26 (t, 3H,
J ¼ 3.6 Hz, eCH3), 1.28 (s, 3H, eCH3), 1.80 (d, 1H,
J ¼ 5.4 Hz, CpreH), 4.20 (q, 2H, J ¼ 6.6 Hz, CH2), 5.65 (s,
5.1.3. General procedure for the synthesis of 30-substituted
cyclopropanespirohydantoins 5aek and 5m
To a solution of compound 4 (1 mmol) and EtOH
(10 mL) was added sodium (1.2 mmol), and the reaction
mixture was stirred at room temperature for 2 h. EtOH
was removed under reduced pressure. Ethyl acetate and wa-
ter were added to the residue. The ethyl acetate layer was

Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
301
dried over anhydrous Na2SO4, concentrated, and recrystal-
lized to give compound 5.
(150 MHz, CDCl3): d 10.92, 18.39, 21.69, 22.50, 27.55,
28.19, 48.59, 56.03, 63.29, 159.31, 174.36. MS (m/z): 249
[M þ Na]. Anal. Calcd for C11H18N2O3: C, 58.39; H, 8.02;
N, 12.38; Found: C, 58.06; H, 8.26; N, 12.09%.
5.1.3.1. 1,1-Dimethyl-4,6-diazaspiro [2.4] heptane-5,7-dione
(5a). White solid (94%); Mp: 196e198 ꢁC. IR (KBr, cmꢀ1):
3441 (NeH), 1767 (C]O), 1722 (C]O). 1H NMR
(300 MHz, CDCl3): d 1.02 (s, 1H, CpreH), 1.03 (s, 1H,
CpreH), 1.18 (s, 3H, eCH3), 1.24 (s, 3H, eCH3), 8.15 (s,
1H, NH), 10.65 (s, 1H, NH). 13C NMR (150 MHz, CDCl3):
d 18.83, 22.28, 26.12, 26.36, 49.32, 157.66, 175.44. MS (m/
z): 177 [M þ Na]. Anal. Calcd for C7H10N2O2: C, 54.45; H,
6.54; N, 18.17; Found: C, 54.18; H, 6.66; N, 17.94%.
5.1.3.6. 1,1-Dimethyl-6-benzyl-4,6-diazaspiro [2.4] heptane-
5,7-dione (5f). White solid (95%); Mp: 142e144 ꢁC. IR
1
(KBr, cmꢀ1): 3218 (NeH), 1755 (C]O), 1712 (C]O). H
NMR (300 MHz, CDCl3): d 1.12 (d, 1H, J ¼ 5.1 Hz, Cpre
H), 1.21 (s, 3H, eCH3), 1.27 (s, 3H, eCH3), 1.28 (d, 1H,
J ¼ 5.1 Hz, CpreH), 4.57 (s, 2H, eCH2), 7.25e7.37 (m, 5H,
AreH), 8.57 (s, 1H, NH). 13C NMR (150 MHz, CDCl3):
d 18.53, 22.52, 26.99, 27.92, 42.50, 48.71, 127.98, 128.82,
136.57, 158.14, 173.23. MS (m/z): 267 [M þ Na]. Anal. Calcd
for C14H16N2O2: C, 68.83; H, 6.60; N, 11.47; Found: C, 68.96;
H, 6.32; N, 11.64%.
5.1.3.2. 1,1-Dimethyl-6-methyl-4,6-diazaspiro [2.4] heptane-
5,7-dione (5b). Needle-shaped crystals (95%); Mp: 155e
157 ꢁC. IR (KBr, cmꢀ1): 3431 (NeH), 1755 (C]O), 1703
(C]O). 1H NMR (300 MHz, CDCl3): d 1.18 (d, 1H,
J ¼ 3.0 Hz, CpreH), 1.29 (s, 3H, eCH3), 1.38 (s, 3H, e
CH3), 1.48 (d, 1H, J ¼ 3.0 Hz, CpreH), 3.04 (s, 3H, eCH3),
7.52 (br s, 1H, NH). 13C NMR (150 MHz, CDCl3): d 18.53,
22.55, 24.83, 26.99, 27.65, 48.78, 158.78, 173.80. MS (m/z):
191 [M þ Na]. Anal. Calcd for C8H12N2O2: C, 57.13; H,
7.19; N, 16.66; Found: C, 57.25; H, 7.25; N, 16.30%.
5.1.3.7. 1,1-Dimethyl-6-phenyl-4,6-diazaspiro [2.4] heptane-
5,7-dione (5g). White solid (93%); Mp: 155e157 ꢁC. IR
1
(KBr, cmꢀ1): 3447 (NeH), 1767 (C]O), 1709 (C]O). H
NMR (300 MHz, CDCl3): d 1.21 (d, 1H, J ¼ 3.0 Hz, Cpre
H), 1.43 (s, 3H, eCH3), 1.31 (s, 3H, eCH3), 1.59 (d, 1H,
J ¼ 3.0 Hz, CpreH), 6.74 (s, 1H, NH), 7.36e7.47 (m, 5H,
AreH). 13C NMR (150 MHz, CDCl3): d 18.46, 22.59, 27.42,
28.15, 48.41, 126.43, 128.23, 129.20, 132.11, 156.95,
172.24. MS (m/z): 253 [M þ Na]. Anal. Calcd for
C13H14N2O2: C, 67.81; H, 6.13; N, 12.17; Found: C, 68.06;
H, 5.91; N, 11.84%.
5.1.3.3. 1,1-Dimethyl-6-isopropyl-4,6-diazaspiro [2.4] hep-
tane-5,7-dione (5c). Needle-shaped crystals (92%); Mp:
122e124 ꢁC. IR (KBr, cmꢀ1): 3427 (NeH), 1768 (C]O),
1
1708 (C]O). H NMR (300 MHz, CDCl3): d 1.29 (d, 1H,
J ¼ 5.1 Hz, CpreH), 1.28 (s, 6H, 2-CH3), 1.36 (d, 6H, 2-
CH3), 1.42 (d, 1H, J ¼ 5.1 Hz, CpreH), 4.30e4.39 (m, 1H,
CH), 7.54 (br s, 1H, NH). 13C NMR (150 MHz, CDCl3):
d 18.41, 19.96, 22.53, 26.79, 27.74, 43.72, 48.13, 158.64,
173.52. MS (m/z): 219 [M þ Na]. Anal. Calcd for
C10H16N2O2: C, 61.20; H, 8.22; N, 14.27; Found: C, 61.08;
H, 8.11; N, 14.14%.
5.1.3.8. 1,1-Dimethyl-6-(4-methylphenyl)-4,6-diazaspiro [2.4]
heptane-5,7-dione (5h). White solid (93%); Mp: 178e
180 ꢁC. IR (KBr, cmꢀ1): 3445 (NeH), 1762 (C]O), 1713
(C]O). 1H NMR (300 MHz, CDCl3): d 1.20 (d, 1H,
J ¼ 5.1 Hz, CpreH), 1.29 (s, 3H, eCH3), 1.41 (s, 3H, e
CH3), 1.54 (d, 1H, J ¼ 5.1 Hz, CpreH), 2.38 (s, 3H, eCH3),
7.36 (s, 1H, NH), 7.26 (d, 2H, J ¼ 12 Hz, AreH), 7.29 (d,
2H, J ¼ 12 Hz, AreH). 13C NMR (150 MHz, CDCl3):
d 18.53, 21.41, 22.57, 27.51, 28.06, 48.51, 126.35, 129.47,
129.86, 138.23, 157.52, 172.52. MS (m/z): 267 [M þ Na].
Anal. Calcd for C14H16N2O2: C, 68.83; H, 6.60; N, 11.47;
Found: C, 69.06; H, 6.52; N, 11.64%.
5.1.3.4. 1,1-Dimethyl-6-butyl-4,6-diazaspiro [2.4] heptane-
5,7-dione (5d). Needle-shaped crystals (95%); Mp: 104e
106 ꢁC. IR (KBr, cmꢀ1): 3426 (NeH), 1755 (C]O), 1709
(C]O). 1H NMR (300 MHz, CDCl3): d 0.93 (t, 3H,
J ¼ 3.6 Hz, CH3), 1.16 (d, 1H, J ¼ 2.7 Hz, CpreH), 1.28 (s,
3H, eCH3), 1.31e1.36 (m, 2H, CH2), 1.37 (s, 3H, eCH3),
1.47 (d, 1H, J ¼ 2.7 Hz, CpreH), 1.60e1.63 (m, 2H, CH2),
3.52 (t, 2H, J ¼ 3.6 Hz, eCH2e), 7.57 (br s, 1H, NH). 13C
NMR (150 MHz, CDCl3): d 11.09, 15.74, 17.43, 19.75,
24.14, 24.89, 27.73, 35.90, 45.81, 156.03, 173.93. MS (m/z):
233 [M þ Na]. Anal. Calcd for C11H18N2O2: C, 62.83; H,
8.63; N, 13.32; Found: C, 62.76; H, 8.70; N, 13.45%.
5.1.3.9. 1,1-Dimethyl-6-(4-methoxyphenyl)-4,6-diazaspiro [2.4]
heptane-5,7-dione (5i). Needle-shaped crystals (94%); Mp:
143e145 ꢁC. IR (KBr, cmꢀ1): 3446 (NeH), 1759 (C]O),
1
1717 (C]O). H NMR (300 MHz, CDCl3): d 1.20 (d, 1H,
J ¼ 5.1 Hz, CpreH), 1.29 (s, 3H, eCH3), 1.40 (s, 3H, e
CH3), 1.55 (d, 1H, J ¼ 5.1 Hz, CpreH), 3.82 (s, 3H, e
OCH3), 7.00 (d, 2H, J ¼ 8.4 Hz, AreH), 7.05 (br s, 1H, NH),
7.32 (d, 2H, J ¼ 8.4 Hz, AreH). 13C NMR (150 MHz,
CDCl3): d 18.54, 22.57, 27.51, 28.06, 48.51, 55.72, 114.56,
124.82, 127.87, 157.64, 159.36, 172.67. MS (m/z): 283
[M þ Na]. Anal. Calcd for C14H16N2O3: C, 64.60; H, 6.20;
N, 10.76; Found: C, 64.79; H, 6.05; N, 10.43%.
5.1.3.5. 1,1-Dimethyl-6-(1-hydroxybutan-2-yl)-4,6-diazaspiro
[2.4] heptane-5,7-dione (5e). White solid (93%); Mp: 94e
95 ꢁC. IR (KBr, cmꢀ1): 3519 (NeH), 1760 (C]O), 1692
(C]O). 1H NMR (300 MHz, CDCl3): d 0.90 (m, 3H, e
CH3), 1.18 (d, 1H, J ¼ 5.1 Hz, CpreH), 1.26 (s, 3H, eCH3),
1.34 (s, 3H, eCH3), 1.47 (d, 1H, J ¼ 5.1 Hz, CpreH),
1.83e1.96 (m, 2H, eCH2), 3.73e3.91 (m, 3H, eCH2, e
CH), 4.07 (br s, 1H, OH), 7.60 (br s, 1H, NH). 13C NMR
5.1.3.10. 1,1-Dimethyl-6-(4-fluorophenyl)-4,6-diazaspiro [2.4]
heptane-5,7-dione (5j). Needle-shaped crystals (93%); Mp:

302
Q. Zhu et al. / European Journal of Medicinal Chemistry 44 (2009) 296e302
150e151 ꢁC. IR (KBr, cmꢀ1): 3447 (NeH), 1769 (C]O),
through ear electrodes for 0.25 s. Abolition of the hind limb
tonic extensor component of the seizure is defined as protec-
tion, and results are expressed as number of animals pro-
tected/number of animals tested.
1
1709 (C]O). H NMR (300 MHz, CDCl3): d 1.13 (d, 1H,
J ¼ 5.7 Hz, CpreH), 1.29 (s, 3H, eCH3), 1.41 (s, 3H, e
CH3), 1.56 (d, 1H, J ¼ 5.7 Hz, CpreH), 7.12e7.43 (m, 4H,
AreH), 7.73 (br s, 1H, NH). 13C NMR (150 MHz, CDCl3):
d 18.52, 22.51, 27.81, 28.23, 48.55, 116.18, 128.04, 128.28,
157.32, 161.55, 172.40 ppm. MS (m/z): 271 [M þ Na]. Anal.
Calcd for C13H13FN2O2: C, 62.90; H, 5.28; N, 11.28; Found:
C, 62.68; H, 5.15; N, 11.04%.
5.2.2. Pentylenetetrazole (PTZ) induced seizure test
For the chemically induced convulsant test according to the
method of Vamecq et al. [21], pentylenetetrazole was dis-
solved in sufficient 0.9% saline to allow subcutaneous
injections to mice. The animals given subcutaneous pentylene-
tetrazole (scPTZ) in a dose of 70 mg kgꢀ1 in the scruff of neck
were observed for at least 30 min for the presence or absence
of a seizure [22,23]. Standard drug in this model was sodium
valproate (80 mg kgꢀ1 p.o.) and was injected 60 min prior to
PTZ challenge. The failure to observe even a threshold seizure
(a single episode of clonic spasms of at least 5 s duration) is
defined as protection.
5.1.3.11. 1,1-Dimethyl-6-(3,5-dichlorophenyl)-4,6-diazaspiro
[2.4] heptane-5,7-dione (5k). Needle-shaped crystals (92%);
Mp: 194e196 ꢁC. IR (KBr, cmꢀ1): 3446 (NeH), 1770
(C]O), 1721 (C]O). 1H NMR (300 MHz, DMSO-d6):
d 1.17 (d, 1H, J ¼ 2.7 Hz, CpreH), 1.22 (s, 3H, eCH3),
1.27 (s, 3H, eCH3), 1.33 (d, 1H, J ¼ 2.7 Hz, CpreH), 7.54
(s, 2H, AreH), 7.63 (s, 1H, AreH), 8.90 (s, 1H, NH). 13C
NMR (150 MHz, DMSO-d6): d 23.73, 26.96, 32.08, 32.27,
53.11, 130.66, 132.54, 139.13, 140.06, 159.89, 177.02. MS
(m/z): 322 [M þ Na]. Anal. Calcd for C13H12Cl2N2O2: C,
52.19; H, 4.04; N, 9.36; Found: C, 52.26; H, 3.87; N, 9.23%.
References
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5.1.3.12. 1,1-Dimethyl-6-(4-nitrylphenyl)-4,6-diazaspiro [2.4]
heptane-5,7-dione (5m). Pale yellow needle-shaped crystals
(92%); Mp: 162e164 ꢁC. IR (KBr, cmꢀ1): 3217 (NeH),
1771 (C]O), 1716 (C]O). 1H NMR (300 MHz, DMSO-
d6): d 1.21 (d, 1H, J ¼ 5.4 Hz, CpreH), 1.25 (s, 3H, eCH3),
1.30 (s, 3H, eCH3), 1.37 (d, 1H, J ¼ 5.4 Hz, CpreH), 7.76
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