Synthesis and structure-activity relationship studies on novel 8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,3-diazaspiro[4.5]decane-2,4-dione derivatives as anticonvulsant agents

Article abstract of DOI:10.1007/s00044-012-0265-x

A series of novel 8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,3-diazaspiro[4.5] decane-2,4-dione derivatives 7-36 was synthesized and their pharmacological activity was determined with the objective to better understand their structure-activity relationship for anticonvulsant activity. All the compounds were evaluated for their possible anticonvulsant activity by maximal electroshock seizure (MES) test and their neurotoxic effects were determined by rotarod test. Majority of the compounds were active in MES tests. Compounds 24, 27, and 34 showed a significant and protective effect on seizure, when compared with standard drug phenytoin. The compounds having amide bond showed moderate protective effect on MES induced seizures compared to sulfonamide.

Full text of DOI:10.1007/s00044-012-0265-x

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:2633–2644
DOI 10.1007/s00044-012-0265-x
ORIGINAL RESEARCH
Synthesis and structure–activity relationship studies on novel
8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,3-diazaspiro[4.5]decane-2,
4-dione derivatives as anticonvulsant agents
•
•
•
M. Madaiah M. K. Prashanth H. D. Revanasiddappa
B. Veeresh
Received: 2 July 2012 / Accepted: 28 September 2012 / Published online: 9 October 2012
Ó Springer Science+Business Media New York 2012
Abstract A series of novel 8-amino-3-[2-(4-fluorophen-
oxy)ethyl]-1,3-diazaspiro[4.5]decane-2,4-dione derivatives
7–36 was synthesized and their pharmacological activity
was determined with the objective to better understand
their structure–activity relationship (SAR) for anticonvul-
sant activity. All the compounds were evaluated for their
possible anticonvulsant activity by maximal electroshock
seizure (MES) test and their neurotoxic effects were
determined by rotorod test. Majority of the compounds
were active in MES tests. Compounds 24, 27, and 34
showed a significant and protective effect on seizure, when
compared with standard drug phenytoin. The compounds
having amide bond showed moderate protective effect on
MES induced seizures compared to sulfonamide.
affecting a large section of people both male and female
across the world. Every year approximately 250,000 new
cases are added to this figure. Epilepsy also poses a consid-
erable economic burden on the society. The direct costs of
epilepsy vary significantly depending on the severity of the
disease and the response to the treatment. The known
potential causes of epilepsy include brain tumors, infections,
traumatic head injuries, perinatal insults, developmental
malformations, cerebrovascular diseases, febrile seizures, and
status epileptics (Loscher, 2002). Many patients have seizures
that are resistant to the available medical therapies. Although
70–80 % of epileptics are currently controlled by a variety of
drugs, seizure protection is often accompanied by numerous
side effects including drowsiness, ataxia, gastrointestinal
disturbances, gingival hyperplasia, hirsutism, and megalob-
lastic anemia (Davies-Jones, 1988; Bialer et al., 2004).
Over the years, there has been considerable success in the
development of novel antiepileptic drugs (AED) along with
new improved formulations. These include older ‘‘first
generation’’ drugs such as carbamazepine, phenobarbital,
valproic acid, and newer, ‘‘second generation’’ drugs such
as lamotrigine, vigabatrin, tiagabine, topiramate, gabapen-
tin, and levetiracetam (Patel et al., 2006; Mc Cabe, 2000).
The selection of an antiepileptic drug for the treatment is
predicated on its efficacy for the specific type of seizures,
tolerability, and safety (Hwang and Kim, 2008; Kwan and
Brodie, 2000). Therefore, it is essential to search for newer
chemical entities for the treatment of epilepsy. A review on
the new structural entities having anticonvulsant activity
has recently appeared (Cosford et al., 1998). Quite recently,
spirohydantoin analogs have become an emerging new class
of potent anticonvulsants (Zha et al., 2004).
Keywords Spirohydantoins ꢀ Acid chloride ꢀ
Sulfonyl chloride ꢀ Anticonvulsant ꢀ Epilepsy
Introduction
Epilepsy is a common neurological affliction characterized by
excessive temporary neuronal discharge that affects about
1 % of the world’s population (Pessah et al., 2009). It is
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-012-0265-x) contains supplementary
material, which is available to authorized users.
M. Madaiah ꢀ M. K. Prashanth ꢀ H. D. Revanasiddappa (&)
Department of Studies in Chemistry, University of Mysore,
Manasagangotri, Mysore 570 006, India
e-mail: hdrevanasiddappa@yahoo.com
Hydantoins, a class of cyclic imides, have been demon-
strated to possess good anticonvulsant property (Merritt and
Putnam, 1938; Hassell et al., 1980). Depending on the nature
B. Veeresh
Department of Pharmacology, G Pullareddy College
of Pharmacy, Mehdipatnam, Hyderabad 580 028, India
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Med Chem Res (2013) 22:2633–2644
Synthesis of tert-butyl (4-oxocyclohexyl)carbamate (3)
of substitution on the hydantoin ring, a wide range of
other pharmacological properties, e.g., antihypertensive
(Edmunds et al., 1995), herbicidal (Hanessian et al., 1995),
anti-HIV (Comber et al., 1992), antibacterial (Oh et al.,
1995), and antiviral (Kim et al., 2001) activities, have also
been identified. This prompted the authors to prepare a new
class of spirohydantoin analogs, such as 1,3-diazaspirohyd-
antoins and study their anticonvulsant activity through
maximal electroshock seizure (MES) model, and their neu-
rotoxic effects were determined by rotorod test.
A mixture of dimethyl sulfoxide (5.54 g, 71.04 mmol) and
dichloromethane (50 mL) was stirred at -78 °C. Oxalyl
chloride (4.51 g, 35.53 mmol) was added dropwise, stirred
for 1 h, tert-butyl (4-hydroxycyclohexyl)carbamate (5.1 g,
23.68 mmol) in dichloromethane (25 mL) was added at
-78 °C, and allowed to be stirred for 2 h. After completion
of the reaction (TLC), it was quenched with triethylamine
(11.98 g, 118.44 mmol). The reaction mixture was poured
into water, extracted with dichloromethane (3 9 40 mL),
the product was dried over Na2SO4, and concentrated in
vacuo to get the crude product which was purified by column
chromatography over silica gel (60–120 mesh) using hex-
ane/ethyl acetate (6:4) as eluent to get the pure product.
Colorless liquid: (4.30 g, 85 %); 1H NMR (400 MHz,
DMSO-d6): d 8.40 (s, 1H), 3.90 (m, 1H), 1.77–1.78 (m, 2H),
1.62–1.63 (m, 4H), 1.53–1.54 (m, 2H), 1.42 (s, 9H); MS: m/z
213.3 (M?), 214.3 (M ? 1).
Experimental section
General
The starting materials and reagents were obtained from
commercial suppliers and were used without further purifi-
cation. Melting points were determined in one end open
capillary tubes on a Buchi 530 melting point apparatus and are
uncorrected. The 1H and 13C NMR spectra were recorded on
Bruker Advance 400 MHz NMR instrument using TMS as
internal standard and DMSO-d6/CDCl3 as solvent. Chemical
shift are given in parts per million (d-scale) and coupling
constant are given in Hertz. Mass spectra were recorded on
Perkin–Elmer LC–MS PE Sciex API/65 Spectrophotometer.
IR spectra were recorded using KBr on 8400S Shimadzu
Fourier Transform Spectrophotometer (mmax in cm-1). Silica
gel column chromatography was performed using Merck
7734 silica gel (60–120 mesh) and Merck made TLC plate.
Elemental analysis (C, H, and N) was undertaken with Perkin-
Elmer model 240C analyzer and the data showed good
agreement between the experimentally determined values and
the theoretically calculated values within 0.4 %.
Synthesis of tert-butyl (2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl)carbamate (4)
A mixture of tert-butyl (4-oxocyclohexyl)carbamate (4.3 g,
20.16 mmol) and ammonium carbonate (4.26 g, 44.35 mmol)
was taken in ethanol (25 mL) and water (25 mL). A solution
of sodium cyanide (2.07 g, 42.34 mmol) in water (10 mL)
was added dropwise and the reaction mixture was stirred at
room temperature for 24 h and heated to 50 °C for 24 h and
cooled to room temperature. After completion of the reaction
(TLC), the solid was filtered, washed with water (100 mL),
and dried in vacuo to get the hydantoin. White color solid:
1
(4.5 g, 79 %); H NMR (400 MHz, DMSO-d6): d 10.61 (s,
1H), 8.48 (s, 1H), 6.72 (s, 1H), 3.17 (s, 1H), 1.77–1.78 (m,
2H), 1.62–1.63 (m, 4H), 1.53–1.56 (m, 2H), 1.43 (s, 9H); MS:
m/z 283.3 (M?), 284.3 (M ? 1).
Synthesis
Synthesis of tert-butyl {3-[2-(4-fluorophenoxy)ethyl]-
2,4-dioxo-1,3-diazaspiro[4.5]dec-8-yl}carbamate (5)
Synthesis of tert-butyl (4-hydroxycyclohexyl)
carbamate (2)
A mixture of tert-butyl (2,4-dioxo-1,3-diazaspiro[4.5]dec-8-
yl)carbamate (4.5 g, 15.88 mmol), anhydrous potassium
carbonate (3.07 g, 22.23 mmol), and 1-(2-bromoethoxy)-4-
fluorobenzene (4.17 g, 19.05 mmol) in acetonitrile (50 mL)
was refluxed for 6 h. After completion of the reaction (TLC),
it was cooled to room temperature and filtered. Filtrate was
concentrated under vacuo to give the crude product which
was then purified by column chromatography over silica gel
(60–120 mesh) using chloroform/methanol (9:1) as eluent to
A
mixture of 4-aminocyclohexanol hydrochloride
(4 g, 26.47 mmol), triethylamine (5.35 g, 52.95 mmol), and
Boc anhydride (5.77 g, 26.47 mmol) in dry dichloromethane
(40 mL) was stirred at room temperature for 16 h. After
completion of the reaction (TLC), the reaction mixture was
poured into water and extracted with dichloromethane
(3 9 40 mL), the product was dried over anhydrous Na2SO4,
andconcentratedinvacuotogivethe crudeproduct whichwas
recrystallized from hexane to get the pure product. White
color solid: (5.10 g, 90 %); 1H NMR (400 MHz, DMSO-d6):
d 8.38 (s, 1H), 3.54 (m, 1H), 3.17 (m, 1H), 2.10 (d, J = Hz,
1H), 1.77–1.78 (m, 2H), 1.62–1.63 (m, 4H), 1.53–1.56 (m,
2H), 1.43 (s, 9H). MS: m/z 215.3 (M?), 216.3 (M ? 1).
1
get the pure product. White color solid: (5.4 g, 81 %); H
NMR (400 MHz, DMSO-d6): d 8.93 (s, 1H), 7.24–7.25 (m,
2H), 7.14–7.14 (m, 2H), 6.76 (d, J = 5.48 Hz, 1H), 4.51 (s,
2H), 3.21 (s, 1H), 1.80–1.80 (m, 2H), 1.68–1.69 (m, 2H),
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Med Chem Res (2013) 22:2633–2644
2635
1.54–1.57 (m, 2H), 1.43–1.45 (m, 2H), 1.39 (s, 9H); MS: m/z
391.4 (M?), 392.4 (M ? 1).
1H), 7.45–7.45 (m, 1H), 7.33–7.36 (m, 2H), 7.08–7.11 (m, 2H),
6.86–6.87 (m, 2H), 4.07 (t, J = 5.16 Hz, 2H), 3.67 (t,
J = 6.00 Hz, 2H), 3.37 (s, 1H), 2.56 (s, 3H), 1.30–1.63 (m, 8H);
MS: m/z 475.5 (M?), 476.5 (M ? 1); IR (KBr) 3,362 (N–H),
1,345 (S=O), 1,284 (S=O)cm-1; Calcd for C23H26FN3O5S:
C 58.09, H 5.51, N 8.84 %; Found: C 58.01, H 5.47, N,
8.80 %.
Synthesis of 8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,3-
diazaspiro[4.5]decane-2,4-dione (6)
A reactant tert-butyl{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-
1,3-diazaspiro[4.5]dec-8-yl}carbamate (5.4 g, 12.87 mmol)
was taken in dioxane (30 mL), cooled to 0 °C, and dioxane in
HCl (50 mL) was added and stirred at room temperature for
4 h. After completion of the reaction (TLC), dioxane was
removed under vacuum and the reaction mixture was neutral-
ized with sodium carbonate solution, the product was extracted
with dichloromethane (3 9 50 mL) and dried over Na2SO4,
and finally concentrated in vacuo to get the pure product. White
color solid: (3.4 g, 82 %); 1H NMR (400 MHz, DMSO-d6): d
8.84 (s, 1H), 7.23–7.24 (m, 2H), 7.13–7.13 (m, 2H), 6.02 (m,
2H), 4.50 (s, 2H), 2.60–0.00 (m, 1H), 2.19 (d, J = 8.00 Hz,
2H), 1.66–1.69 (m, 4H), 1.50–1.53 (m, 2H), 1.25–1.29 (m, 2H);
MS: m/z 291.3 (M?), 292.3 (M ? 1).
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-bromobenzene sulfonamide (9)
White color solid: (114 mg, 68 %); mp = 204 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.89 (s, 1H), 7.96 (d, J = 8.88 Hz,
2H), 7.80 (d, J = 7.84 Hz, 2H), 7.54 (t, J = 7.88 Hz, 1H),
7.10 (q, J = 2.20 Hz, 2H), 6.87 (q, J = 4.40 Hz, 2H), 4.08
(t, J = 5.72 Hz, 2H), 3.68 (t, J = 5.76 Hz, 2H), 3.39 (s, 1H),
1.32–1.61 (m, 8H); MS: m/z 540.4 (M?), 541.4 (M ? 1); IR
(KBr) 3,357 (N–H), 1,342 (S=O), 1,280 (S=O)cm-1; Calcd
for C22H23BrFN3O5S: C 48.90, H 4.29, N 7.78 %; Found: C
48.85, H 4.24, N 7.71 %.
General procedure for the synthesis of 7–36
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-
diazaspiro[4.5]dec-8-yl}-2-fluobenzene sulfonamide (10)
A
mixture of 8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,
3-diazaspiro[4.5]decane-2,4-dione (100 mg 0.31 mmol), tri-
ethylamine (0.46 mmol), and sulfonyl chlorides/acid chlo-
rides (0.34 mmol) in dichloromethane (4 mL) was stirred at
room temperature for 16 h. After completion of the reaction
(TLC), it was quenched with saturated sodium bicarbonate
solution; the product was extracted with dichloromethane
(3 9 4 mL), dried over Na2SO4, and concentrated in vacuo
to get the crude product which was next purified by column
chromatography on silica employing dichloromethane/
methanol (9:1) as elutant to obtain the pure product.
White color solid: (104 mg, 70 %); mp = 175 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.88 (s, 1H), 8.10 (d, J = 8.28 Hz,
1H), 7.80 (d, J = 1.56 Hz, 1H), 7.71 (t, J = 1.00 Hz, 1H),
7.35–7.35 (m, 2H), 7.08–7.10 (m, 2H), 6.86–6.86 (m, 2H),
4.08 (t, J = 5.72 Hz, 2H), 3.67 (t, J = 5.84 Hz, 2H), 3.34 (s,
1H), 1.45–1.63 (m, 8H); MS: m/z 479.5 (M?), 480.5
(M ? 1); IR (KBr) 3,368 (N–H), 1,347 (S=O), 1,283
(S=O) cm-1; Calcd for C22H23F2N3O5S: C 55.11, H 4.83, N
8.76 %; Found: C 55.08, H 4.81, N 8.72 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2,5-dimethyl benzenesulfonamide (11)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro
[4.5]dec-8-yl}-3,4-dimethyl benzenesulfonamide (7)
White color solid: (107 mg, 70 %); mp = 180 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.84 (s, 1H), 7.67–7.69 (m, 2H),
7.18–7.20 (m, 1H), 7.09–7.10 (m, 1H), 6.99–6.99 (m, 2H),
6.86–6.89 (m, 2H), 4.06 (t, J = 5.76 Hz, 2H), 3.67 (t,
J = 5.76 Hz, 2H), 3.33 (s, 1H), 2.45 (s, 3H), 2.25 (s, 3H),
1.51–1.59 (m, 2H), 1.46 (t, J = 4.32 Hz, 2H), 1.33 (d,
J = 9.06 Hz, 2H), 1.18 (t, J = 7.22 Hz, 2H); MS: m/z 489.6
(M?), 490.6 (M ? 1); IR (KBr) 3,355 (N–H), 1,336 (S=O),
1,278 (S=O) cm-1; Calcd for C24H28FN3O5S: C 58.88, H
5.76, N 8.58 %; Found: C 58.81, H 5.70, N 8.51 %.
White color solid: (102 mg, 67 %); mp = 180 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.87 (s, 1H), 7.63 (s, 1H), 7.61 (s,
1H), 7.50–7.52 (m, 1H), 7.30 (d, J = 7.96 Hz, 1H),
7.07–7.08 (m, 2H), 6.85–6.86 (m, 2H), 4.07 (t, J = 5.76 Hz,
2H), 3.67 (t, J = 5.76 Hz, 2H), 3.33 (s, 1H), 2.26 (d,
J = 10.72 Hz, 6H), 1.28–1.59 (m, 8H); MS: m/z 489.6 (M?),
490.6 (M ? 1); IR (KBr) 3,361 (N–H), 1,344 (S=O), 1,281
(S=O)cm-1; Calcd for C24H28FN3O5S: C 58.88, H 5.76, N
8.58 %; Found: C 58.81, H 5.70; N, 8.52 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-methylbenzene sulfonamide (8)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-methylbenzene sulfonamide (12)
White color solid: (105 mg, 71 %); mp = 178 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.85 (s, 1H), 7.86 (s, 1H), 7.84 (s,
White color solid: (102 mg, 69 %); mp = 176 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.83 (s, 1H), 7.32–7.33 (m, 4H),
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Med Chem Res (2013) 22:2633–2644
7.22 (d, J = 7.88 Hz, 1H), 7.08–7.08 (m, 2H), 6.89–6.93 (m,
2H), 4.12 (t, J = 5.72 Hz, 2H), 3.72 (t, J = 5.76 Hz, 2H),
3.34 (s, 1H), 2.45 (s, 3H), 1.18–1.90 (m, 8H); MS: m/z 475.5
(M?), 476.5 (M ? 1); IR (KBr) 3,362 (N–H), 1,342 (S=O),
1,281 (S=O) cm-1; Calcd for C23H26FN3O5S: C 58.09, H
5.51, N 8.84 %; Found: C 58.02, H 5.48, N 8.82 %.
3.43 (s, 1H), 2.28 (s, 3H), 1.65 (d, J = 11.84 Hz, 1H),
1.49–1.59 (m, 6H), 1.37 (d, J = 11.00 Hz, 1H); MS: m/z
489.6 (M?), 490.6 (M ? 1); IR (KBr) 3,352 (N–H), 1,337
(S=O), 1,277 (S=O) cm-1; Calcd for C24H28FN3O5S: C
58.88, H 5.76, N 8.58 %; Found: C 58.81, H 5.72, N 8.50 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-fluobenzene sulfonamide (17)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-chlorobenzene sulfonamide (13)
White color solid: (105 mg, 70 %); mp = 175 °C; 1H
NMR (400 MHz, DMSO-d6): d 8.87 (s, 1H), 7.93–7.95 (m,
1H), 7.58–7.65 (m, 3H), 7.48 (t, J = 1.52 Hz, 1H),
7.08–7.12 (m, 2H), 6.85–6.88 (m, 2H), 5.08 (t,
J = 5.72 Hz, 2H), 3.68 (t, J = 11.40 Hz, 2H), 3.38 (s,
1H), 1.57–1.60 (m, 8H); MS: m/z 479.5 (M?), 480.5
(M ? 1); IR (KBr) 3,362 (N–H), 1,346 (S=O), 1,287
(S=O) cm-1; Calcd for C22H23F2N3O5S: C 55.11, H 4.83,
N 8.76 %; Found: C 55.09, H 4.81, N 8.73 %.
White color solid: (108 mg, 70 %); mp = 190 °C; 1H
NMR (400 MHz, DMSO-d6): d 8.88 (s, 1H), 7.96 (s, 1H),
7.81–7.82 (m, 1H), 7.75–7.78 (m, 1H), 7.66–7.69 (m, 1H),
7.61 (t, J = 7.92 Hz, 1H), 7.08–7.12 (m, 2H), 6.85–6.89
(m, 2H), 4.08 (t, J = 5.68 Hz, 2H), 3.68 (t, J = 5.76 Hz,
2H), 3.33 (s, 1H), 1.32–1.58 (m, 8H); MS: m/z 496 (M?),
497 (M ? 1); IR (KBr) 3,354 (N–H), 1,341 (S=O), 1,282
(S=O) cm-1; Calcd for C22H23ClFN3O5S: C 53.28, H 4.67,
N 8.47 %; Found: C 53.21, H 4.60, N 8.42 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3,5-dimethylbenzene sulfonamide (18)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-fluoro-2-methyl benzenesulfonamide (14)
White color solid: (108 mg, 71 %); mp = 182 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.88 (s, 1H), 7.40–0.00 (m, 3H),
7.07–7.14 (m, 2H), 6.84–6.91 (m, 4H), 4.10 (t, J = 5.68 Hz,
2H), 3.70 (t, J = 5.84 Hz, 2H), 3.37 (s, 1H), 2.29 (s, 6H),
1.41–1.52 (m, 8H); MS: m/z 489.6 (M?), 490.6 (M ? 1); IR
(KBr) 3,364 (N–H), 1,347 (S=O), 1,280 (S=O) cm-1; Calcd
for C24H28FN3O5S: C 58.88, H 5.76, N 8.58 %; Found: C
58.82, H 5.71, N 8.52 %.
White color solid: (114 mg, 74 %); mp = 186 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.85 (s, 1H), 7.84–7.92 (m, 2H),
7.24 (t, J = 9.00 Hz, 2H), 7.10 (t, J = 8.72 Hz, 2H),
6.86–6.89 (m, 2H), 4.07 (t, J = 5.72 Hz, 2H), 3.67 (t,
J = 5.72 Hz, 2H), 3.34 (s, 1H), 2.56 (s, 3H), 1.59 (q,
J = 10.56 Hz, 3H), 1.42 (d, J = 11.04 Hz, 3H), 1.32 (d,
J = 8.88 Hz, 1H), 1.18 (d, J = 11.12 Hz, 1H); MS: m/z
493.5 (M?), 494.5 (M ? 1); IR (KBr) 3,364 (N–H), 1,346
(S=O), 1,287 (S=O) cm-1; Calcd for C23H25F2N3O5S: C
55.97, H 5.11, N 8.51 %; Found: C 55.97, H 5.11, N 8.51 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-ethylbenzene sulfonamide (19)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-methoxybenzene sulfonamide (15)
White color solid: (113 mg, 74 %); mp = 169 °C; 1H
NMR (400 MHz, DMSO-d6): d 8.86 (s, 1H), 7.70–7.72 (m,
3H), 7.69–7.70 (m, 2H), 7.08–7.12 (m, 2H), 6.85–6.89 (m,
2H), 4.07 (t, J = 5.76 Hz, 2H), 3.67 (t, J = 5.84 Hz, 2H),
3.34 (s, 1H), 2.65 (q, J = 7.68 Hz, 2H), 1.41–1.59 (m, 8H),
1.19 (t, J = 7.20 Hz, 3H); MS: m/z 489.6 (M?), 490.6
(M ? 1); IR (KBr) 3,360 (N–H), 1,341 (S=O), 1,283
(S=O) cm-1; Calcd for C24H28FN3O5S: C 58.88, H 5.76, N
8.58 %; Found: C 58.84, H 5.72, N 8.51 %.
White color solid: (103 mg, 67 %); mp = 181 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.87 (s, 1H), 7.19–7.74 (m, 2H),
7.61 (d, J = 7.88 Hz, 1H), 7.06–7.12 (m, 4H), 6.84–6.89 (m,
2H), 4.07 (t, J = 5.84 Hz, 2H), 3.75 (s, 3H), 3.67 (t,
J = 5.80 Hz, 2H), 3.34 (s, 1H), 1.16–1.57 (m, 8H); MS: m/z
491.5 (M?), 492.5 (M ? 1); IR (KBr) 3,359 (N–H), 1,340
(S=O), 1,281 (S=O) cm-1; Calcd for C23H26FN3O6S: C
56.20, H 5.33, N 8.55 %; Found: C 56.36, H 5.30, N 8.51 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-methylbenzene-sulfonamide (20)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-methylbenzyl sulfonamide (16)
White color solid: (107 mg, 72 %); mp = 179 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.87 (s, 1H), 7.58–7.71 (m, 2H),
7.35–7.44 (m, 3H), 7.08–7.13 (m, 2H), 6.85–6.88 (m, 2H),
4.07 (t, J = 11.40 Hz, 2H), 3.67 (t, J = 5.76 Hz, 2H), 3.34
(s, 1H), 2.30 (s, 3H), 1.51–1.58 (m, 2H), 1.46 (t,
J = 4.36 Hz, 2H), 1.33 (d, J = 9.04 Hz, 2H), 1.18 (t,
White color solid: (112 mg, 74 %); mp = 167 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.83 (s, 1H), 7.23–7.23 (m, 2H),
7.10–7.17 (m, 5H), 6.89–6.93 (m, 2H), 4.21 (d, J = 1.84 Hz,
2H), 4.12 (t, J = 5.64 Hz, 2H), 3.72 (t, J = 5.68 Hz, 2H),
123

Med Chem Res (2013) 22:2633–2644
2637
J = 7.28 Hz, 2H); MS: m/z 475.5 (M?), 476.5 (M ? 1); IR
(KBr) 3,358 (N–H), 1,339 (S=O), 1,278 (S=O) cm-1; Calcd
for C23H26FN3O5S: C 58.09, H 5.51, N 8.84 %; Found: C
58.02, H 5.47, N 8.80 %.
(KBr) 3,378 (N–H), 1,677 (C=O) cm-1; Calcd for
C24H26FN3O4: C 65.59, H 5.96, N 9.56 %; Found: C 65.54,
H 5.91, N 9.50 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-
diazaspiro[4.5]dec-8-yl}-2-phenylacetamide (25)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-cyanobenzene sulfonamide (21)
White color solid: (103 mg, 75 %); mp = 200 °C; 1H NMR
White color solid: (105 mg, 69 %); mp = 221 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.86 (s, 1H), 8.34 (d, J = 8.00 Hz,
1H), 8.04–8.09 (m, 2H), 7.90 (t, J = 7.80 Hz, 1H), 7.81 (t,
J = 7.64 Hz, 1H), 7.10 (t, J = 8.80 Hz, 2H), 6.86–6.89 (m,
2H), 4.32 (t, J = 7.68 Hz, 2H), 3.68 (t, J = 5.68 Hz, 2H), 3.39
(s, 1H), 1.67 (t, J = 12.75 Hz, 2H), 1.43–1.52 (m, 2H), 1.34 (d,
J = 9.28 Hz, 2H), 1.26 (d, J = 1.24 Hz, 2H); MS: m/z 486.5
(M?), 487.5 (M ? 1); IR (KBr) 3,369 (N–H), 1,368 (S=O),
1,287 (S=O) cm-1; Calcd for C23H23FN4O5S: C 56.78, H 4.77,
N 11.52 %; Found: C 56.73, H 4.71, N 11.48 %.
(400 MHz, DMSO-d6):
d
9.00 (s, 1H), 8.51 (d,
J = 276.68 Hz, 1H), 7.44–7.46 (m, 5H), 7.07 (t, J = 8.76 Hz,
2H), 6.87–6.90 (m, 2H), 4.14 (s, 1H), 4.11 (t, J = 5.72 Hz,
2H), 3.71 (t, J = 5.80 Hz, 2H), 3.40 (s, 2H), 1.65–1.75 (m,
8H); MS: m/z 439.5 (M?), 440.5 (M ? 1); IR (KBr) 3,364
(N–H), 1,658 (C=O) cm-1; Calcd for C24H26FN3O4: C 65.59,
H 5.96, N 9.56 %; Found: C 65.54, H 5.90, N 9.51 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-fluorobenzamide (26)
2-Chlorobenzyl{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-
1,3-diazaspiro[4.5]dec-8-yl}carbamate (22)
White color solid: (100 mg, 72 %); mp = 202 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.99 (s, 1H), 8.26 (d, J = 8.04 Hz,
1H), 7.49–7.54 (m, 2H), 7.24–7.28 (m, 2H), 7.06–7.10 (m,
2H), 6.88–6.91 (m, 2H), 4.10–4.13 (m, 3H), 3.71 (t,
J = 5.84 Hz, 2H), 1.41–1.70 (m, 8H); MS: m/z 443.4 (M?),
White color solid: (108 mg, 71 %); mp = 191 °C; 1H
NMR (400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.35 (d,
J = 8.04 Hz, 1H), 7.84 (q, J = 8.60 Hz, 2H), 7.53 (q,
J = 11.04 Hz, 2H), 7.05–7.09 (m, 2H), 6.87–6.90 (m, 2H),
4.80 (s, 2H), 4.09–4.14 (m, 2H), 3.69 (t, J = -8.32 Hz,
2H), 1.35–1.86 (m, 8H); MS: m/z 489.9 (M?), 491
444.4 (M ? 1); IR (KBr) 3,369 (N–H), 1,671 (C=O) cm-1
;
Calcd for C23H23F2N3O4: C 62.30, H 5.23, N 9.48 %; Found:
C 62.27, H 5.20, N 9.42 %.
(M ? 1); IR (KBr) 3,368 (N–H), 1,670 (C=O) cm-1
;
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-methylbenzamide (27)
Calcd for C24H25ClFN3O5: C 58.84, H 5.14, N 8.58 %;
Found: C 58.78, H 5.10, N 8.51 %.
White color solid: (99 mg, 72 %); mp = 213 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.01 (s, 1H), 8.23 (d, J = 8.16 Hz,
1H), 7.61 (q, J = 4.00 Hz, 2H), 7.33 (d, J = 4.96 Hz, 2H),
7.08 (t, J = 8.68 Hz, 2H), 6.88–6.92 (m, 2H), 4.13 (q,
J = 5.68 Hz, 3H), 3.72 (t, J = 5.84 Hz, 2H), 2.35 (s, 3H),
1.43–1.86 (m, 8H); MS: m/z 439.5 (M?), 440.5 (M ? 1); IR
(KBr) 3,373 (N–H), 1,670 (C=O) cm-1; Calcd for
C24H26FN3O4: C 65.59, H 5.96, N 9.56 %; Found: C 65.51,
H 5.89, N 9.51 %.
4-Chlorophenyl{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-
1,3-diazaspiro[4.5]dec-8-yl}carbamate (23)
White color solid: (112 mg, 76 %); mp = 198 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.01 (s, 1H), 8.35 (d, J = 8.04 Hz,
1H), 7.84 (q, J = 8.60 Hz, 2H), 7.53 (q, J = 11.04 Hz, 2H),
7.05–7.08 (m, 2H), 6.86–6.90 (m, 2H), 4.09–4.14 (m, 3H),
3.69 (t, J = 8.32 Hz, 2H), 1.35–1.86 (m, 8H); MS: m/z 475.9
(M?), 477 (M ? 1); IR (KBr) 3,372 (N–H), 1,675
(C=O) cm-1; Calcd for C23H23ClFN3O5: C 58.05, H 4.87, N
8.83 %; Found: C 58.01, H 4.84, N 8.80 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-chlorobenzamide (28)
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-methylbenzamide (24)
White color solid: (104 mg, 73 %); mp = 231 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.01 (s, 1H), 8.41 (d, J = 7.96 Hz,
1H), 7.87 (s, 1H), 7.79 (d, J = 7.76 Hz, 1H), 7.60 (t,
J = 0.92 Hz, 1H), 7.50 (t, J = 7.88 Hz, 1H), 7.08 (t,
J = 8.64 Hz, 2H), 6.88–6.91 (m, 2H), 4.12 (q, J = 1.00 Hz,
3H), 3.72 (t, J = 5.76 Hz, 2H), 1.33–1.87 (m, 8H); MS: m/z
459.9 (M?), 461 (M ? 1); IR (KBr) 3,376 (N–H), 1,679
(C=O) cm-1; Calcd for C23H23ClFN3O4: C 60.07, H 5.04, N
9.14 %; Found: C 60.01, H 5.02, N 9.10 %.
White color solid: (101 mg, 74 %); mp = 213 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.18 (d, J = 8.12 Hz,
1H), 7.72 (d, J = 8.16 Hz, 2H), 7.24 (d, J = 8.04 Hz, 2H),
7.05–7.09 (m, 2H), 6.87–6.91 (m, 2H), 4.15 (s, 1H), 4.11 (t,
J = 5.76 Hz, 2H), 3.71 (t, J = 5.84 Hz, 2H), 2.34 (s, 3H),
1.13–1.85 (m, 8H); MS: m/z 439.5 (M?), 440.5 (M ? 1); IR
123

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Med Chem Res (2013) 22:2633–2644
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}benzamide (29)
J = 8.04 Hz, 1H), 7.84 (q, J = 1.80 Hz, 2H), 6.93 (q,
J = 1.84 Hz, 2H), 7.05–7.09 (m, 2H), 6.87–6.90 (m, 2H),
4.12 (q, J = 5.72 Hz, 3H), 3.71 (t, J = 5.80 Hz, 2H),
1.35–1.86 (m, 8H); MS: m/z 459.9 (M?), 461 (M ? 1); IR
(KBr) 3,376 (N–H), 1,677 (C=O) cm-1; Calcd for
C23H23ClFN3O4: C 60.07, H 5.04, N 9.14 %; Found: C
60.04, H 5.01, N 9.10 %.
White color solid: (100 mg, 76 %); mp = 189 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.02 (s, 1H), 8.28 (d, J = 8.04 Hz,
1H), 7.82 (d, J = 7.48 Hz, 2H), 7.51 (d, J = 7.20 Hz, 1H),
7.45 (t, J = 10.88 Hz, 2H), 7.08 (t, J = 8.76 Hz, 2H), 6.90
(q, J = 4.32 Hz, 2H), 4.10–4.17 (m, 3H), 3.72 (t,
J = 5.76 Hz, 2H), 1.34–1.87 (m, 8H); MS: m/z 425.5 (M?),
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-(trifluoromethyl) benzamide (34)
426.5 (M ? 1); IR (KBr) 3,365 (N–H), 1,667 (C=O) cm-1
;
Calcd for C23H24FN3O4: C 64.93, H 5.69, N 9.88 %; Found:
C 64.89, H 5.61, N 9.84 %.
White color solid: (112 mg, 73 %); mp = 217 °C; 1H
NMR (400 MHz, DMSO-d6): d 8.99 (s, 1H), 8.43 (d,
J = 8.08 Hz, 1H), 7.63–7.77 (m, 3H), 7.47 (d,
J = 7.44 Hz, 1H), 7.08 (d, J = 2.40 Hz, 2H), 6.88–6.91
(m, 2H), 4.11 (q, J = 5.12 Hz, 3H), 3.72 (t, J = 5.84 Hz,
2H), 1.44–1.84 (m, 8H); MS: m/z 493.5 (M?), 494.5
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-3-fluorobenzamide (30)
White color solid: (106 mg, 77 %); mp = 202 °C; 1H NMR
(400 MHz, DMSO-d6): d 8.98 (s, 1H), 8.26 (d, J = 8.04 Hz,
1H), 7.49–7.54 (m, 2H), 7.24–7.27 (m, 2H), 7.06–7.11 (m, 2H),
6.89–6.91 (m, 2H), 4.11–4.13 (m, 3H), 3.71 (t, J = 5.84 Hz,
2H), 1.40–1.71 (m, 8H); MS: m/z 443.4 (M?), 444.4 (M ? 1);
IR (KBr) 3,370 (N–H), 1,672 (C=O) cm-1; Calcd for
C23H23F2N3O4: C 62.30, H 5.23, N 9.48 %; Found: C 62.28, H
5.21, N 9.43 %.
(M ? 1); IR (KBr) 3,378 (N–H), 1,680 (C=O) cm-1
;
Calcd for C24H23F4N3O4: C 58.42, H 4.70, N 8.52 %;
Found: C 58.38, H 4.67, N 8.49 %.
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-2-chlorobenzamide (35)
White color solid: (106 mg, 74 %); mp = 231 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.38 (d, J = 8.12 Hz,
1H), 7.37–7.49 (m, 4H), 7.08 (q, J = 2.61 Hz, 2H),
6.88–6.91 (m, 2H), 4.11 (q, J = 6.48 Hz, 3H), 3.71 (t,
J = 5.88 Hz, 2H), 1.41–1.85 (m, 8H); MS: m/z 459.9 (M?),
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-fluorobenzamide (31)
White color solid: (102 mg, 74 %); mp = 202 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.29 (d, J = 8.08 Hz,
1H), 7.87–7.90 (m, 2H), 7.26–7.30 (m, 2H), 7.05–7.09 (m,
2H), 6.87–6.90 (m, 2H), 4.12 (q, J = 5.72 Hz, 3H), 3.71 (t,
J = 5.84 Hz, 2H), 1.35–1.86 (m, 8H); MS: m/z 443.4 (M?),
461 (M ? 1); IR (KBr) 3,372 (N–H), 1,676 (C=O) cm-1
;
Calcd for C23H23ClFN3O4: C 60.07, H 5.04, N 9.14 %;
Found: C 60.01, H 4.97, N 9.10 %.
444.4 (M ? 1); IR (KBr) 3,371 (N–H), 1,674 (C=O) cm-1
;
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-tert-butylbenzamide (36)
Calcd for C23H23F2N3O4: C 62.30, H 5.23, N 9.48 %; Found:
C 62.27, H 5.20, N 9.41 %.
White color solid: (110 mg, 73 %); mp = 249 °C; 1H
NMR (400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.18 (d,
J = 8.16 Hz, 1H), 7.74 (d, J = 8.44 Hz, 2H), 7.45 (d,
J = 8.48 Hz, 2H), 7.07 (t, J = 8.76 Hz, 2H), 6.87–6.90 (m,
2H), 4.09–4.12 (m, 3H), 3.71 (t, J = 5.80 Hz, 2H),
1.65–1.75 (m, 8H), 1.28 (s, 9H); MS: m/z 481.6 (M?), 482.6
(M ? 1); IR (KBr) 3,366 (N–H), 1,669 (C=O) cm-1; Calcd
for C27H32FN3O4: C 67.34, H 6.70, N 8.73 %; Found: C
67.28, H 6.67, N 8.70 %.
Phenyl{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro
[4.5]dec-8-yl}carbamate (32)
White color solid: (107 mg, 78 %); mp = 188 °C; 1H NMR
(400 MHz, DMSO-d6): d 9.02 (s, 1H), 8.35 (d, J = 8.04 Hz,
1H), 7.84 (q, J = 8.60 Hz, 2H), 7.53 (q, J = 11.04 Hz, 2H),
7.04–7.08 (m, 3H), 6.86–6.90 (m, 2H), 4.09–4.14 (m, 3H),
3.69 (t, J = 8.32 Hz, 2H), 1.35–1.86 (m, 8H); MS: m/z 441.5
(M?), 442.5 (M ? 1); IR (KBr) 3,366 (N–H), 1,669
(C=O) cm-1; Calcd for C23H24FN3O5: C 62.58, H 5.48, N
9.52 %; Found: C 62.50, H 5.42, N 9.48 %.
Pharmacology
N-{3-[2-(4-fluorophenoxy)ethyl]-2,4-dioxo-1,3-diazaspiro[4.5]
dec-8-yl}-4-chlorobenzamide (33)
The anticonvulsant activity was evaluated by MES test and
neurotoxicity screening. Albino mice (18–20 g) were pro-
cured from National Institute of Nutrition, Hyderabad. The
animals were kept in individual cages for 1 week to
White color solid: (108 mg, 75 %); mp = 231 °C; 1H
NMR (400 MHz, DMSO-d6): d 9.00 (s, 1H), 8.35 (d,
123

Med Chem Res (2013) 22:2633–2644
2639
acclimatize for laboratory conditions. They were allowed
free access of water and food.
protective effects on seizure when compared to vehicle
treated mice. Compounds 24, 27, and 34 were able to pro-
tect seizure effect significantly higher than others and this
effect was similar when compared to standard drug treated
mice. Compounds 7, 11, 18, 22, 23, 25, 26, 28, 29, 30, 31,
32, 33, 35, and 36 showed moderate protective effect on
seizure. Compounds 8, 9, 10, 13, 14, 15, 16, 17, 20, and 21
showed lower protective effect on seizure. Majority of the
compounds, except 7, 12, and 19 were active in MES tests
making them useful for broad spectrum of seizure types.
The bioactivity in MES test was exhibited by sulfon-
amide derivatives 7–21, when the hydrogen atom at the
position-21 was replaced by a phenyl ring; substitution
with small lipophilic group like fluoro, chloro at the ortho,
meta, and para position of the phenyl ring was found to
decrease the anticonvulsant activity; and strongly electron-
withdrawing group like cyano at the 2-position of the
phenyl ring caused a decrease in activity. However, sub-
stitution with two methyl groups at the phenyl ring of 7, 11,
and 18 resulted in increased activity. Similarly, in amide
derivatives such as 22–36, when the hydrogen atom at the
21-position was replaced by a phenyl ring the activity
increased but substitution with small electron-withdrawing
group on the phenyl ring resulted in moderate anticonvul-
sant activity. Compounds 24, 27, and 34 exhibited activity
at 100 mg/kg in MES test. Evidently, this distal hydro-
phobic center alters the bioavailability of the compounds.
In the neurotoxic experiments, the compounds were
administrated by oral route at 100 mg/kg in mice. The
tested compounds did not showed neurotoxicity at 0.5 and
1 h. The potent compounds 24, 27, and 34 did not show
neurotoxicity. Compounds 26, 30, and 31 showed 50 %
toxicity after 4 h of oral administration.
All the experimental procedures were carried out in
accordance with Committee for the Purpose of Control and
Supervision of Experiments on Animals (CPCSEA)
guidelines. The study was reviewed and approved by the
Institutional Animal Ethics Committee, G. Pulla Reddy
College of Pharmacy, Hyderabad, India.
MES model
Maximal electroshock seizure (MES) model was used in the
present study to evaluate the anticonvulsant activity of the
drugs on mice. Seizures were induced in mice by delivering
electro shock of 150 mA for 0.2 s by means of a convulsi-
ometer through a pair of ear clip electrodes. The test com-
pounds (100 mg/kg) were administered by oral route 30 min
before the MES test. The animals were observed closely for
2 min. The percentage of inhibition of seizure relative to
control was recorded and calculated (Vogel and Vogel, 1997).
Phenytoin (100 mg/kg, p.o) was used as a standard drug.
Neurotoxicity screening
The minimal motor impairment was measured in mice by
the rotorod test. The mice were trained to stay on the
accelerating rotorod that rotates at 10 revolutions per min.
The rod diameter was 3.2 cm. Trained animals were given
an intraperitoneally (ip) injection of the test compounds at
dose of 100 mg/kg. Neurotoxicity was indicated by the
inability of animal to maintain equilibrium on the rod for at
least 1 min in each of the three trails.
Statistical analysis
In the present study, data were analyzed by one-way
analysis of variance (ANOVA) followed by Dunnet test to
compare the difference between the groups.
Discussion
Chemical synthesis
The synthetic pathway utilized in the preparation of
8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,3-diazaspiro[4.5]
decane-2,4-dione derivatives is outlined in Scheme 1. A
variety of combinatorial approaches have been described
by which pharmacophoric groups were attached to such
relativity rigid scaffold. The synthesis begins with the
protection of 4-aminocyclohexanol hydrochloride 1 with
Boc anhydride using dry dichloromethane as a solvent
(Wenya et al., 2010). The oxidation reaction was carried by
Swern oxidation (Ting et al., 2005) using dichloromethane,
dimethylsulfoxide, oxalyl chloride, and triethylamine as
the reagents at -78 °C, to form ketone 3. Under Bucherer–
Bergs condition, construction of azaspiro bicyclic hydan-
toin 4 was made (Brown et al., 1997; Scott et al., 1997).
Results
Pharmacological activity
Anticonvulsant assays were performed for all the synthe-
sized compounds 7–36. The compounds were injected
intraperitoneally into mice and evaluated in the maximal
electroshock (MES) and neurotoxicity screens, using dose
of 100 mg/kg and the observations were made at four
different time intervals (0.5, 1, 2, and 4 h). The results are
presented in Tables 1 and 2.
The initial anticonvulsant evaluation showed that all the
compounds, except 12 and 19 exhibited significant and
123

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Med Chem Res (2013) 22:2633–2644
Table 1 Results and effects of the compounds 7–36 in the maximal
electroshock seizure
Table 2 Neurotoxicity screening of synthesized compounds 7–36 in
the rotorod test
Intraperitoneal injection in micea
Compound
Neurotoxicity screen
2 h
Treatment
E/Fb
% Protection
4 h
Control (vehicle)
7.69
7.61
6.69
7.12
7.31
4.31
7.54
7.34
7.44
6.98
6.64
7.19
4.24
7.58
7.34
7.28
3.02
3.13
1.57
3.19
1.72
1.51
3.76
3.11
1.69
1.58
2.98
3.59
1.59
3.89
3.12
–
Standard
7
0/4
0/4
0/4
0/4
0/4
0/4
0/4
1/4
0/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
2/4
0/4
1/4
0/4
2/4
2/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
1/4
0/4
0/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
2/4
0/4
1/4
0/4
2/4
2/4
0/4
1/4
0/4
0/4
0/4
7
42.61
13.0
8
8
9
7.41
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
4.94
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
43.95
1.14
4.55
3.25
9.23
12.6
6.5
43.12
1.23
4.55
4.51
48.82
59.29
79.58c
47.21
48.12
78.62c
58.61
55.78
58.02
57.94
56.89
49.83
79.32c
49.41
48.15
Values are expressed as mean SE, n = 6 animals (mice) in each
group
The data in the table represent ratio between the numbers of the
animals that exhibited neurotoxicity against the number of tested
animals
a
100 mg/kg of dose were administered ip
b
E/F = extension/flexion [decrease in ratio of extension phase (in
seconds)/flexion phase (in seconds)]
c
p \ 0.05 when compared to standard drug treated mice
basification with sodium carbonate solution (Anna and
Andrzej, 2003). The aim of the step 6 was to introduce
respective sulfonyl chloride/acid chloride at the N-position
of azaspiro bicyclic moiety to lead the desired compounds
7–36 for structure–activity relationship (SAR) study (Susumu
et al., 1990; Guillaume et al., 2010). This was furnished by
normal nucleophilic substitution reactions with good yield.
The reaction was carried out in aqueous ethanolic medium
using sodium cyanide and ammonium carbonate at ele-
vated temperature. The introduction of the substituent aryl
groups at N-3 position of hydantoin ring was achieved via
selective N-alkylation reaction by reacting with aryl halide
in the presence of potassium carbonate and acetonitrile
solvent (Zha et al., 2004; Carmen et al., 1984). Target key
intermediate 6 was accomplished by deprotection of Boc
group from compound 5 with dioxane in HCl, followed by
1
The formation of the hydantoin ring was confirmed by H
NMR and Mass spectral studies.
The N-substitution of substituted 8-amino-3-[2-(4-flu-
[4.5]decane-2,4-dione
orophenoxy)ethyl]-1,3-diazaspiro
123

Med Chem Res (2013) 22:2633–2644
2641
Pharmacological activity
with different acid chlorides/sulfonyl chlorides was con-
firmed by the disappearance of NH2 group in 1H NMR and
IR spectra. The products obtained were purified by column
chromatography using hexane and ethyl acetate (8:2) as an
eluents. The absence of NH2 absorption bands in the IR
spectra confirmed that the synthesized compounds were
obtained via condensation. The appearance of strong
absorption band at around 3,350 cm-1 is due to the
stretching vibration of N–H band in the synthesized com-
pounds. The proton NMR spectral data agreed with respect
to the number of protons and their chemical shifts with the
proposed structures. The proton spectral data of the inter-
mediate, hydantoin 6 showed resonance at d 6.02 ppm (m,
2H, NH2). In all the synthesized compounds, the above
resonance disappeared and additional resonances assigned
to the –NH–S=O (d 7.96–7.94 ppm) and –NH–C=O (d
8.42–8.40 ppm) were observed, which confirmed the con-
densation between the amino group and carbonyl group.
The chemical structures, physical data, and yield of all the
synthesized compounds are given in Table 3.
In past years the discovery and development of anticon-
vulsant drugs have been the noticeable research fields. The
search for newer compounds combining strong anticon-
vulsant activity is in progress. Many amide and sulfon-
amide derivatives have been discovered as potent
anticonvulsant drugs and the SAR studies have been
reported (Siddiqui et al., 2007). In the present study, the
anticonvulsant activity of 30 newly synthesized 8-amino-3-
[2-(4-fluorophenoxy)ethyl]-1,3-diazaspiro[4.5]decane-2,
4-dione derivatives of amides and sulfonamides in MES
models of seizures in mice was investigated. For several
decades, antiepileptic drug research has focused on iden-
tifying new potential drugs based on their anticonvulsant
activity against single acute seizures induced by various
stimulators, usually in mice and rats. All established AED
have anticonvulsant activity in at least MES model
(Loscher and Schmidt, 1994). Thus, this test may in some
way distinguish the potential utility of compounds against
O
HN
O
OH
NH
O
OH
a
b
c
HN
O
HN
O
HN
O
NH
2 HCl
O
O
O
1
4
2
3
d
O
F
O
O
O
F
N
O
F
O
NH
N
N
O
NH
NH
O
g
O
e
f
HN
O
HN
NH2
R
7-36
6
5
Scheme 1 Synthesis of 8-amino-3-[2-(4-fluorophenoxy)ethyl]-1,
3-diazaspiro[4.5]decane-2,4-dione (7–36). Reagent and condition
(a) Boc anhydride, triethylamine, dichloromethane, rt, 16 h; (b) oxalyl
chloride, triethylamine, dichloromethane/dimethylsulfoxide, -78 °C,
4 h; (c) ammonium carbonate, sodium cyanide, ethanol/water, rt,
24 h, 50 °C, 24 h; (d) anhydrous potassium carbonate, 1-(bromo-
methyl)-2-(difluoromethoxy)benzene, acetonitrile, reflux, 6 h;
(e) dioxane in HCl, rt 4 h; (f) sodium carbonate solution, rt, 1 h;
(g) R = sulfonyl chloride/acid chloride, triethylamine, dichlorometh-
ane, rt, 16 h
123

2642
Med Chem Res (2013) 22:2633–2644
different seizure types. In the present series of compounds,
many of them showed good anticonvulsant activity at
100 mg/kg compared to phenytoin. So, there is an increase
in anticonvulsant activity by molecular modifications
described in the present work. Regarding the sulfonamide
and amide series, Dimmock and others (Dimmock and
Baker, 1994; Dimmock et al., 2000) have proposed a
binding site hypothesis for these compounds eliciting
anticonvulsant activity.
Table 3 Chemical structure, yield, and melting point of the com-
pounds 7–36
Compound
R
Yield (%)
m.p. (°C)
7
3,4-(H3C)2C6H3SO2
2-H3CC6H4SO2
3- BrC6H4SO2
67
71
68
70
70
69
70
74
67
74
70
71
74
72
69
71
76
74
75
72
72
73
76
77
74
78
75
73
74
73
180
178
204
175
180
176
190
186
181
167
175
182
169
179
221
191
198
213
200
202
213
231
189
202
202
188
231
217
231
249
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
2- FC6H4SO2
2,5-(H3C)2C6H3SO2
4-H3CC6H4SO2
3- ClC6H4SO2
A scrutiny for certain selected structures for active an-
ticonvulsants has been shown to possess a hydrophobic unit
(R), an electron donor group (D), and hydrogen bond
domain unit (HBD). In the present series of compounds,
the active compounds possess all the requirements essential
for anticonvulsant activity as proposed by Dimmock and
others. Thus, our new proposal for a pharmacophore model
includes factors which are responsible for bioactivity is
shown in Fig. 1. From the results of this study, the fol-
lowing SARs could be derived. On the one/other hand, the
substitution pattern at different position of the sulfona-
mides was compared: dimethyl (7, 11, and 18) versus flu-
oro (10 and 17) versus chloro (13) versus methyl (8, 12,
and 20). This emphasizes that the hydrophobic and lipo-
philic domains in the molecule are responsible for the
potent anticonvulsant activity. In addition, comparing the
effect of electron donating (7, 8, 11, 12, 15, 18, and 19) and
electron-withdrawing (13 and 21) groups on the substituted
benzene sulfonamides, those with electron donating sub-
stitutions showed potent anticonvulsant activity. On the
other hand, the presence of methyl group at positions 2 and
5 on the phenyl moiety increased the activity.
4-F,2-H3CC6H3SO2
4-H3COC6H4SO2
4-H3CC6H4 CH2SO2
3-FC6H4SO2
3,5-(H3C)2C6H3SO2
4-H5C2C6H4SO2
3-H3CC6H4SO2
2-NCC6H4SO2
2-ClC6H4CH2ONHCO
4-ClC6H4ONHCO
4-CH3C6H4NHCO
C6H5CH2NHCO
2-FC6H4NHCO
3-CH3C6H4NHCO
3-ClC6H4NHCO
C6H5NHCO
3-FC6H4NHCO
4-FC6H4NHCO
C6H5ONHCO
4-ClC6H4NHCO
2-CF3C6H4NHCO
2-ClC6H4NHCO
4-(CH3)3CHC6H4NHCO
The substitution pattern at different positions of the
amides was compared: hydrogen (29) versus methyl (24
and 27) versus fluoro (26, 30, and 31) versus chloro (28 and
33). This emphasizes that the hydrophobic and lipophilic
Fig. 1 Anticonvulsant agent
showing essential
pharmocophoric elements
present in their structure, HBD
hydrogen bond domain;
D = electron donor;
R
R
O
HBD
O
HBD
R
R
N
N
D
NH
NH
O
O
O
D
D
R = hydrophobic unit
N
R
HN
R
HN
O
HBD
HN
O
HBD
O
S
O
HBD
Phenytoin
R
R
Compounds 7-21
Compounds 22-36
123

Med Chem Res (2013) 22:2633–2644
2643
summary of the seventh Eilat Conference (EILAT VII). Epilepsy
Res 61:1–48
domains in the molecule are responsible for the potent
anticonvulsant activity. In addition, comparing the effect of
electron donating (24, 27, and 36) and electron-withdraw-
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The compounds 7–36 practically did not reduce the
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chemically induced seizure models, showing no effect in
the MES test.
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Conclusion
Anticonvulsants have greatly improved the lives of people
with epilepsy. Approximately 70 % of the patients can
achieve complete freedom from seizures with appropriate
treatment (Scheuer and Pedley, 1997). In this study, all the
compounds having amide bond showed better anticonvul-
sant activity compared to sulfonamide. Methyl substituted
amides 24 and 23 and dimethyl substituted sulfonamides 7,
11, and 18 showed significant protective effects on MES
induced seizures. Similarly, it is quite apparent that there
are at least three parameters for the activity of anticonvul-
sant drugs, that is, (i) a lipophilic domain, (ii) a distal
hydrophobic center, and (iii) an electron-withdrawing
center (–CN=). Hydrophobic size appears to govern the
MES activity. The presence of methyl group showed
improved MES activity. Compounds 24, 27, and 34 without
a fluoro or chloro group showed anticonvulsant activity in
MES test as compared with compounds 12, 13, and 17 with
fluoro or chloro substituent. The synthesized compounds
confirmed the pharmacophore model requirements for the
activity such as (A) hydrophobic domain; (B) a lipophilic
domain; (C) electron withdrawing moiety; and (D) electro
donor acceptor in all the synthesized compounds.
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Acknowledgments The authors are grateful to G. Pullareddy Col-
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facilities to carry out the anticonvulsant activity. One of the authors
MM is thankful to the University of Mysore, Mysore for providing
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