Synthesis and evaluation of 7-substituted-3,4-dihydrobenzo[f][1,4]oxazepin- 5(2H)-ones as anticonvulsant and hypnotic agents

Article abstract of DOI:10.1007/s00044-010-9434-y

A series of 7-substituted-3,4-dihydrobenzo[f] [1,4]oxazepin-5(2H)-ones was synthesized. The anticonvulsant effect and neurotoxicity of the compounds were evaluated with a maximal electroshock (MES) test and a rotated test in mice, respectively. Most of the compounds prepared exhibited anticonvulsant activities in the MES test, 7-(heptyloxy)-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)- one (10) was the most active. In the anti-MES potency test, it showed a median effective dose (ED50) of 19.0 mg/kg. The hypnotic effect of the compound 10 was initially investigated by using a pentobarbital-induced-sleep test. Middle (30 mg/kg) and high doses (60 mg/kg) of the compound 10 both significantly increased the pentobarbital- induced sleep from 20.9 ± 5.28 to 26.9 ± 6.14 and 45.67 ± 7.94 min, respectively. Springer Science+Business Media, LLC 2010.

Full text of DOI:10.1007/s00044-010-9434-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:996–1004
DOI 10.1007/s00044-010-9434-y
ORIGINAL RESEARCH
Synthesis and evaluation of 7-substituted-3,4-
dihydrobenzo[f][1,4]oxazepin-5(2H)-ones as anticonvulsant
and hypnotic agents
•
Xian-Qing Deng Ming-Xia Song Cheng-Xi Wei
•
•
•
Zhi-Gang Sun Zhe-Shan Quan
Received: 26 April 2010 / Accepted: 13 September 2010 / Published online: 26 September 2010
Ó Springer Science+Business Media, LLC 2010
Abstract A series of 7-substituted-3,4-dihydrobenzo[f]
[1,4]oxazepin-5(2H)-ones was synthesized. The anticon-
vulsant effect and neurotoxicity of the compounds were
evaluated with a maximal electroshock (MES) test and a
rotated test in mice, respectively. Most of the compounds
prepared exhibited anticonvulsant activities in the MES
test, 7-(heptyloxy)-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-
one (10) was the most active. In the anti-MES potency test,
it showed a median effective dose (ED50) of 19.0 mg/kg.
The hypnotic effect of the compound 10 was initially
investigated by using a pentobarbital-induced-sleep test.
Middle (30 mg/kg) and high doses (60 mg/kg) of the
compound 10 both significantly increased the pentobarbi-
tal-induced sleep from 20.9 5.28 to 26.9 6.14 and
45.67 7.94 min, respectively.
more than 2 million Americans and 60 million people
worldwide (Strine et al., 2005). Although the current drugs
provide adequate seizure control in many patients, it is
roughly estimated that up to 28–30% of patients are poorly
treated with the available antiepileptic drugs (AEDs)
(Kwan and Brodie, 2000; Spear, 2001). Moreover, many
AEDs have serious side effects (Al-Soud et al., 2003;
Meador, 2003), and lifelong medication may be required.
Toxicity, intolerance, and lack of efficacy are the limita-
tions of the current AEDs. Therefore, the continued search
for safer and more effective new AEDs is necessary.
In our previous work, a series of derivatives of
6-alkoxy-3,4-dihydro-2(1H)-quinolinone were found to
have anticonvulsant activities, among which 6-benzyloxy-
3,4-dihydro-2(1H)-quinolinone (I) showed the strongest
activity, with an ED50 value of 29.6 mg/kg in the maximal
electroshock (MES) test and a TD50 value of greater than
300 mg/kg (Quan et al., 2005). 7-(4-Fluorobenzylamino)-
2H-benzo[b][1,4]oxazin-3(4H)-one (II), the bioisoterism of
compound I, has also been shown to inhibit seizure with an
ED50 value of 31.7 mg/kg in MES (Piao et al., 2008).
Desirable effects of these agents prompted us to investigate
other heterocycles with similar pharmacological properties
(Fig. 1).
Keywords 1,4-Benzoxazepin-5(2H)-one Á Synthesis Á
Anticonvulsant Á Maximal electroshock Á Hypnosis
Introduction
Epilepsy, one of the most frequent neurological afflictions
in man characterized by excessive temporary neuronal
discharges resulting in uncontrolled convulsion, inflicts
As a part of our continuous efforts in this area, a series
of 7-alkyloxyl-3,4-dihydrobenzo[f][1,4] oxazepin-5(2H)-
ones (III) were designed and synthesized in this study.
Compounds III, the ring enlargement analogues of com-
pounds I through inserting an oxygen atom, were antici-
pated to possess a better anticonvulsant activity. The
anticonvulsant effect and neurotoxicity of the compounds
were evaluated with a MES test and a rotarod test in mice,
respectively. Seizure assays and neurotoxicity evaluations
were according to the antiepileptic drug development
(ADD) program which were developed by the National
X.-Q. Deng Á M.-X. Song Á Z.-S. Quan (&)
College of Pharmacy, Yanbian University,
No. 977, Park Road, Yanji, Jilin 133002, China
e-mail: zsquan@ybu.edu.cn
C.-X. Wei Á Z.-G. Sun
Institute of Neurosurgery, Inner Mongolia University for
Nationalities, No. 1742, Holin River Street, Tongliao, Inner
Mongolia Autonomous Region 028007, China
e-mail: sunzhigang101@yahoo.cn
123

Med Chem Res (2011) 20:996–1004
997
F
(Perkin–Elmer, USA). The major chemicals were pur-
chased from Aldrich Chemical Corporation.
H
O
N
O
Synthesis of 6-methoxy-2,3-dihydrochromen-4-one
O
N
O
N
H
H
oxime (2)
II
I
6-Methoxy-2,3-dihydrochromen-4-one (compound 1)
(7.8 g, 0.044 mol), pyridine (8 ml) and hydroxylamine
hydrochloride (9.17 g, 0.132 mol) were placed into a
round-bottomed flask containing 150 ml of methanol. The
reaction mixture was stirred for 4 h at 70°C. After
removing most of the solvent (1/4 was remained), the
mixture was added to 100 ml of ice-water, filtered and then
recrystallized from alcohol to get 7.95 g of a colorless
solid. 1H-NMR (DMSO-d6, 300 MHz), d 2.79 (t, 2H,
J = 6.1 Hz, N–CH2), 3.73 (s, 3H, O–CH3), 4.11 (t, 2H,
J = 6.1 Hz, O–CH2), 6.82–7.26 (m, 3H, Ar–H), 11.26 (s,
1H, N–OH). IR (KBr) cm-1: 3345 (O–H), 1616 (C=N). MS
m/z 194 (M ? 1).
Fig. 1 Structures of compounds I and II
Institute of Neurological and Communicative Disorders
and Stroke (NINCDS) (Krall et al., 1978; Porter et al.,
1984).
In addition, in the process of evaluating their anticon-
vulsant activity and neurotoxicity, strong hypnotic effects
were discovered. Therefore, the hypnotic effect of the most
active compound 10 was tested using a pentobarbital-
induced-sleep test. The synthesized compounds were
characterized using IR, 1H-NMR, MS, and elemental
analysis techniques (Scheme 1).
Synthesis of 7-methoxy-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (3)
Experimental section
Compound 2 (2.6 g, 0.013 mol) and polyphosphoric acid
(PPA) (45 g) were placed into a three-necked round-bot-
tomed flask. The mixture was heated and stirred with a
blade stirrer at 90°C for 4 h. 100 ml water was added to the
mixture after the temperature of the mixture was equal to
room temperature, and then the aqueous layer was
extracted with CH2Cl2 for three times. The combined
organic layer was dried overnight with anhydrous magne-
sium sulphate. The evaporation of the solvent gave a crude
product which was purified by silica gel column chroma-
tography with CH2Cl2–CH3OH (30:1) to give a white solid.
Chemistry
The melting points were determined in open capillary
tubes. The IR spectra were recorded (In KBr) on a FT-
1
IR1730. H-NMR spectra were measured on an AV-300
(Bruker, Switzerland), and all chemical shifts were given in
parts per million relative to tetramethysilane. Mass spectra
were measured on an HP1100LC (Agilent Technologies,
USA). Elemental analyses were performed on a 204Q CHN
Scheme 1 Synthesis of
Compounds 5–25
O
HO
O
N
O
H3CO
NH
H3CO
H3CO
CH3OH; 80°C for 4 h
PPA
.
H2NOH HCl
O
90°C for 4 h
O
3
2
1
O
O
RO
NH
RBr
HO
NH
BBr3
ethanol; 90°C for 24 h
CH2Cl2; r.t.
O
O
5-25
4
R:
5: -C2H5
6: n-C3H7
7: n-C4H9
9: n-C6H13
10: n-C7H15
11: n-C8H17
13: -CH2C6H5
17: -CH2C6H4(p-Cl)
21: -CH2C6H4(p-Br)
22: -CH2C6H4(o-Br)
23: -CH2 C6H4(p-CH3)
14: -CH2C6H4 (p-F) 18: -CH2C6H4(m-Cl)
15: -CH2C6H4(m-F) 19: -CH2C6H4 (o-Cl )
8: n-C5H11 12: n-C12H25 16: -CH2C6H4 (o-F) 20: -CH2C6H3 (2,6-Cl2) 24: -CH2C6H4(p-OCH3)
25:-CH2C6H3(3,4-(OCH3)2)
123

998
Med Chem Res (2011) 20:996–1004
M.p. 90–92°C, yield = 62%. 1H-NMR (CDCl3, 300 MHz),
d 3.24 (q, 2H, J = 5.2 Hz, N–CH2), 3.73 (s, 3H, O–CH3),
4.17 (t, 2H, J = 5.0 Hz, O–CH2), 6.96 (d, 1H, J = 8.8 Hz,
Ar–H), 7.03 (dd, 1H, J1 = 2.9 Hz, J2 = 8.8 Hz, Ar–H),
7.16 (d, 1H, J1 = 2.9 Hz, Ar–H). 8.34 (s, 1H, –NH–). IR
(KBr) cm-1: 3204 (NH), 1674 (C=O). MS (m/z): 194
(M ? 1).
(s, 1H, –NH–). IR (KBr) cm-1: 3204 (NH), 1674 (C=O).
MS (m/z): 208 (M ? 1). Anal. Calcd. for C11H13NO3: C,
63.76; H, 6.32; N, 6.76. Found: C, 63.94; H, 6.54; N, 6.44.
7-Propoxy-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-
one (6)
M.p. 65–67°C; yield 65%. 1H-NMR (DMSO, 300 MHz): d
0.96 (t, 3H, J = 7.4 Hz, –CH2CH3), 1.70 (m, 2H,
J = 7.0 Hz, –CH2–), 3.24 (q, 2H, J = 5.2 Hz, –NHCH2–),
3.89 (t, 2H, J = 6.5 Hz, –OCH2–), 4.17 (t, 2H,
J = 5.1 Hz, –OCH2–), 6.95 (d, 1H, J = 8.8 Hz, Ar–H),
7.02 (q, 1H, J1 = 3.0 Hz, J2 = 8.8 Hz, Ar–H), 7.15 (d, 1H,
Synthesis of 7-hydroxy-3,4-
dihydrobenzo[f][1,4]oxazepin-5(2H)-one (4)
To a stirred solution of boron tribromide (50 mmol) in
anhydrous dichloromethane (20 ml), a dichloromethane
solution of compound 3 (1.93 g, 10 mmol) was added
dropwise and the reaction continued for 1 h at 0°C and an
additional 2 h at 20°C. Following the addition of 30 ml ice
cold water, the organic layer was separated and the aque-
ous layer extracted with ethyl acetate. The combined
organic layer was dried overnight with anhydrous magne-
sium sulfate and evaporated under reduced pressure to get a
brown solid which was recrystallized from alcohol to get a
J = 3.0 Hz, Ar–H), 8.32 (s, 1H, –NH–). IR (KBr) cm-1
:
3287 (NH), 1623 (C=O). MS (m/z): 222 (M ? 1). Anal.
Calcd. for C12H15NO3: C, 65.14; H, 6.83; N, 6.33. Found:
C, 65.44; H, 6.57; N, 6.55.
7-Butoxy-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one
(7)
1
colorless solid. M.p. 118–120°C, yield = 90%, H-NMR
M.p. 80–82°C; yield 75%. 1H-NMR (DMSO, 300 MHz): d
0.92 (t, 3H, J = 7.4 Hz, –CH2CH3), 1.45 (m, 2H,
J = 7.3 Hz, –CH2–), 1.69 (m, 2H, J = 6.6 Hz, –CH2–),
3.24 (q, 2H, J = 5.1 Hz, –NHCH2–), 3.93 (t, 2H,
J = 6.4 Hz, –OCH2–), 4.17 (t, 2H, J = 5.0 Hz, –OCH2–),
6.94 (d, 1H, J = 8.8 Hz, Ar–H), 7.02 (q, 1H, J1 = 2.8 Hz,
J2 = 8.8 Hz, Ar–H), 7.14 (d, 1H, J = 2.8 Hz, Ar–H), 8.32
(s, 1H, –NH–). IR (KBr) cm-1: 3285 (NH), 1612 (C=O).
MS (m/z): 236 (M ? 1). Anal. Calcd. for C13H17NO3: C,
66.36; H, 7.28; N, 5.95. Found: C, 66.54; H, 7.43; N, 5.73.
(DMSO-d6, 300 MHz) d 3.20 (q, 2H, J = 5.09 Hz,
–NHCH2), 4.12 (t, 2H, J = 5.09 Hz, –OCH2), 6.84–7.00
(m, 3H, Ar–H), 8.22 (s, 1H, –NH–). IR (KBr) cm-1: 3194
(NH), 1647 (C=O).
General procedure for the synthesis of 7-alkyloxyl-3,
4-dihydrobenzo[f][1,4]oxazepin-5(2H)-ones (5–25)
K2CO3 (1.24 g, 0.009 mol), absolute ethanol (50 ml), and
7-hydroxy-3,4-dihydrobenzo[f] [1,4]oxazepin-5(2H)-one
(0.003 mol) were added to a 100 ml round-bottomed flask
equipped with a reflux condenser. After the mixture was
refluxed for 30 min, alkyl bromide, or benzyl chloride
derivatives (0.004 mol) were added into the mixture. The
reaction mixture was heated at reflux temperature for 24 h
and poured into 100 ml of water. The aqueous layer was
extracted with dichloromethane (30 ml 9 3). The com-
bined layer of dichloromethane was dried with anhydrous
MgSO4. The evaporation of the solvent gave a crude
product which was purified by silica gel column chroma-
tography with CH2Cl2–CH3OH (30:1) to a white solid.
7-(Pentyloxy)-3,4-dihydrobenzo[f][1,4]oxazepin-
5(2H)-one (8)
M.p. 57–59°C; yield 70%. 1H-NMR (DMSO, 300 MHz): d
0.88 (t, 3H, J = 6.7 Hz, –CH2CH3), 1.31–1.35 (m, 4H,
–CH2–), 1.68 (m, 2H, –CH2–), 3.24 (q, 2H, J = 5.0 Hz,
–NHCH2–), 3.91 (t, 2H, J = 6.4 Hz, –OCH2–), 4.17 (t, 2H,
J = 5.0 Hz, –OCH2–), 6.94 (d, 1H, J = 8.8 Hz, Ar–H),
7.02 (q, 1H, J1 = 2.8 Hz, J2 = 8.8 Hz, Ar–H), 7.14 (d, 1H,
J = 2.8 Hz, Ar–H), 8.32 (s, 1H, –NH–). IR (KBr) cm-1
:
3179 (NH), 1653 (C=O). MS (m/z): 250 (M ? 1). Anal.
Calcd. for C14H19NO3: C, 67.45; H, 7.68; N, 5.62. Found:
C, 67.69; H, 7.83; N, 5.40.
7-Ethoxy-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one
(5)
7-(Hexyloxy)-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-
one (9)
M.p. 126–128°C; yield 73%. 1H-NMR (DMSO,
300 MHz): d 1.30 (t, 3H, J = 6.9 Hz, –CH2CH3), 3.24 (q,
2H, J = 5.1 Hz, –NHCH2–), 3.99 (q, 2H, J = 6.9 Hz,
–OCH2–), 4.17 (t, 2H, J = 5.0 Hz, –OCH2–), 6.94 (d, 1H,
J = 8.8 Hz, Ar–H), 7.02 (q, 1H, J1 = 2.9 Hz, J2 =
8.8 Hz, Ar–H), 7.14 (d, 1H, J = 2.8 Hz, Ar–H), 8.32
M.p. 58–60°C; yield 79%. 1H-NMR (DMSO, 300 MHz): d
0.96 (t, 3H, J = 6.5 Hz, –CH2CH3), 1.38–1.82 (m, 8H,
–CH2–), 3.34 (q, 2H, J = 5.1 Hz, –NHCH2–), 4.01 (t, 2H,
J = 6.4 Hz, –OCH2–), 4.26 (t, 2H, J = 5.0 Hz, –OCH2–),
123

Med Chem Res (2011) 20:996–1004
999
7.03 (d, 1H, J = 8.8 Hz, Ar–H), 7.10 (q, 1H, J1 = 3.0 Hz,
J2 = 8.9 Hz, Ar–H), 7.23 (d, 1H, J = 3.0 Hz, Ar–H), 8.32
(s, 1H, –NH–). IR (KBr) cm-1: 3224 (NH), 1636 (C=O).
MS (m/z): 264 (M ? 1). Anal. Calcd. for C15H21NO3: C,
68.42; H, 8.04; N, 5.32. Found: C, 68.66; H, 8.31; N, 5.10.
J = 4.9 Hz, –OCH2–), 5.08 (s, 2H, Ar–CH2–), 6.95–7.46
(m, 8H, Ar–H), 8.34 (s, 1H, –NH–). IR (KBr) cm-1: 3189
(NH), 1689 (C=O). MS (m/z): 270 (M ? 1). Anal. Calcd.
for C16H15NO3: C, 71.36; H, 5.61; N, 5.20. Found: C, 71.61;
H, 5.67; N, 5.01.
7-(Heptyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (10)
7-(4-Fluorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (14)
M.p. 50–52°C; yield 71%. 1H-NMR (DMSO, 300 MHz): d
0.86 (t, 3H, J = 6.8 Hz, –CH2CH3), 1.35–1.38 (m, 8H,
–CH2–), 1.68 (m, 2H, J = 6.5 Hz, –CH2–), 3.24 (q, 2H,
J = 5.2 Hz, –NHCH2–), 3.92 (t, 2H, J = 6.4 Hz,
–OCH2–), 4.17 (t, 2H, J = 5.1 Hz, –OCH2–), 6.94 (d, 1H,
J = 8.8 Hz, Ar–H), 7.02 (q, 1H, J1 = 3.1 Hz,
J2 = 8.8 Hz, Ar–H), 7.14 (d, 1H, J = 3.0 Hz, Ar–H), 8.32
(s, 1H, –NH–). IR (KBr) cm-1: 3209 (NH), 1612 (C=O).
MS (m/z): 278 (M ? 1). Anal. Calcd. for C16H23NO3: C,
69.29; H, 8.36; N, 5.05. Found: C, 69.38; H, 8.31; N, 5.21.
M.p. 142–144°C; yield 70%. 1H-NMR (DMSO,
300 MHz): d 3.24 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.18 (t,
2H, J = 4.9 Hz, –OCH2–), 5.06 (s, 2H, Ar–CH2),
6.95–7.52 (m, 7H, Ar–H), 8.53 (s, 1H, –NH–). IR (KBr)
cm-1: 3210 (NH), 1656 (C=O). MS (m/z): 288 (M ? 1).
Anal. Calcd. for C16H14FNO3: C, 66.89; H, 4.91; N, 4.88.
Found: C, 67.08; H, 5.05; N, 4.69.
7-(3-Fluorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (15)
7-(Octyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (11)
M.p. 100–102°C; yield 75%. 1H-NMR (DMSO, 300 MHz):
d 3.26 (q, 2H, J = 5.2 Hz, –NHCH2–), 4.19 (t, 2H,
J = 4.9 Hz, –OCH2–), 5.12 (s, 2H, Ar–CH2–), 6.96–7.48
(m, 7H, Ar–H), 8.34 (s, 1H, –NH–). IR (KBr) cm-1: 3210
(NH), 1650 (C=O). MS (m/z): 288 (M ? 1). Anal. Calcd.
for C16H14FNO3: C, 66.89; H, 4.91; N, 4.88. Found: C,
66.99; H, 5.09; N, 4.62.
M.p. 62–65°C; yield 84%. 1H-NMR (DMSO, 300 MHz): d
0.84 (t, 3H, J = 6.6 Hz, –CH2CH3), 1.26–1.39 (m, 10H,
–CH2–), 1.67 (m, 2H, J = 6.6 Hz, –CH2–), 3.24 (q, 2H,
J = 5.1 Hz, –NHCH2–), 3.92 (t, 2H, J = 6.4 Hz, –OCH2–),
4.17 (t, 2H, J = 4.9 Hz, –OCH2–), 6.94 (d, 1H, J = 8.8 Hz,
Ar–H), 7.02 (q, 1H, J1 = 3.0 Hz, J2 = 8.8 Hz, Ar–H), 7.14
(d, 1H, J = 2.9 Hz, Ar–H), 8.32 (s, 1H, –NH–). IR (KBr)
cm-1: 3292 (NH), 1659 (C=O). MS (m/z): 292 (M ? 1).
Anal. Calcd. for C17H25NO3: C, 70.07; H, 8.65; N, 4.81.
Found: C, 70.30; H, 8.71; N, 4.67.
7-(2-Fluorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (16)
M.p. 108–110°C; yield 65.0%. 1H-NMR (DMSO,
300 MHz): d 3.25 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.19 (t,
2H, J = 4.9 Hz, –OCH2–), 5.12 (s, 2H, Ar–CH2–),
6.96–7.57 (m, 7H, Ar–H), 8.36 (s, 1H, –NH–). IR (KBr)
cm-1: 3291 (NH), 1662 (C=O). MS (m/z): 288 (M ? 1).
Anal. Calcd. for C16H14FNO3: C, 66.89; H, 4.91; N, 4.88.
Found: C, 67.03; H, 4.98; N, 4.64.
7-(Dodecyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (12)
M.p. 82–84°C; yield 72%. 1H-NMR (DMSO, 300 MHz): d
1.84 (t, 3H, J = 6.8 Hz, –CH2CH3), 1.05–1.38 (m, 18H,
–CH2–), 1.68 (m, 2H, J = 6.9 Hz, –CH2–), 3.25 (q, 2H,
J = 5.1 Hz, –NHCH2–), 3.92 (t, 2H, J = 6.3 Hz, –OCH2–),
4.17 (t, 2H, J = 5.0 Hz, –OCH2–), 6.94 (d, 1H, J = 8.8 Hz,
Ar–H), 7.01 (q, 1H, J1 = 2.9 Hz, J2 = 8.8 Hz, Ar–H), 7.14
(d, 1H, J = 2.8 Hz, Ar–H), 8.32 (s, 1H, –NH–). IR (KBr)
cm-1: 3199 (NH), 1677 (C=O). MS (m/z): 348 (M ? 1).
Anal. Calcd. for C21H33NO3: C, 72.58; H, 9.57; N, 4.03.
Found: C, 72.76; H, 9.63; N, 3.88.
7-(4-Chlorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (17)
M.p. 169–170°C; yield 94%. 1H-NMR (DMSO,
300 MHz): d 3.25 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.18 (t,
2H, J = 4.7 Hz, –OCH2–), 5.09 (s, 2H, Ar–CH2–),
6.96–7.46 (m, 7H, Ar–H), 8.34 (s, 1H, –NH–). IR (KBr)
cm-1: 3190 (NH), 1657 (C=O). MS (m/z): 304 (M ? 1).
Anal. Calcd. for C16H14ClNO3: C, 63.27; H, 4.65; N, 4.61.
Found: C, 63.45; H, 4.79; N, 4.53.
7-(Benzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (13)
M.p. 132–134°C; yield 81%. 1H-NMR (DMSO, 300 MHz):
d 3.25 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.18 (t, 2H,
123

1000
Med Chem Res (2011) 20:996–1004
7-(3-Chlorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (18)
(NH), 1665 (C=O). MS (m/z): 348 (M ? 1). Anal. Calcd.
for C16H14BrNO3: C, 55.19; H, 4.05; N, 4.02. Found: C,
55.37; H, 4.26; N, 3.79.
M.p. 88–90°C; yield 71%. 1H-NMR (DMSO, 300 MHz): d
3.25 (q, 2H, J = 4.7 Hz, –NHCH2–), 4.19 (t, 2H,
J = 4.7 Hz, –OCH2–), 5.11 (s, 2H, Ar–CH2–), 6.97–7.51
(m, 7H, Ar–H), 8.35 (s, 1H, –NH–). IR (KBr) cm-1: 3187
(NH), 1667 (C=O). MS (m/z): 304 (M ? 1). Anal. Calcd.
for C16H14ClNO3: C, 63.27; H, 4.65; N, 4.61. Found: C,
63.39; H, 4.77; N, 4.48.
7-(4-Methylbenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (23)
M.p. 168–169°C; yield 89%. 1H-NMR (DMSO,
300 MHz): d 2.3 (s, 3H, Ar–CH3), 3.24 (q, 2H, J = 5.1 Hz,
–NHCH2–), 4.18 (t, 2H, J = 5.0 Hz, –OCH2–), 5.03
(s, 2H, Ar–CH2–), 6.94–7.33 (m, 7H, Ar–H), 8.33 (s, 1H,
–NH–). IR (KBr) cm-1: 3200 (NH), 1658 (C=O). MS (m/z):
284 (M ? 1). Anal. Calcd. for C17H17NO3: C, 72.07; H,
6.05; N, 4.94. Found: C, 72.36; H, 6.14; N, 4.75.
7-(2-Chlorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (19)
M.p. 138–141°C; yield 49%. 1H-NMR (DMSO, 300 MHz):
d 3.25 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.19 (t, 2H,
J = 5.0 Hz, –OCH2–), 5.14 (s, 2H, Ar–CH2), 6.97–7.61
(m, 7H, Ar–H), 8.36 (s, 1H, –NH–). IR (KBr) cm-1: 3231
(NH), 1670 (C=O). MS (m/z): 304 (M ? 1). Anal. Calcd.
for C16H14ClNO3: C, 63.27; H, 4.65; N, 4.61. Found: C,
63.42; H, 4.77; N, 4.48.
7-(4-Methoxybenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (24)
M.p. 161–162°C; yield 47%. 1H-NMR (DMSO,
300 MHz): d 3.24 (q, 2H, J = 5.1 Hz, –NHCH2–), 3.75 (s,
3H, –OCH3), 4.18 (t, 2H, J = 4.8 Hz, –OCH2–), 4.99 (s,
2H, Ar–CH2–), 6.93–7.38 (m, 7H, Ar–H), 8.32 (s, 1H,
–NH–). IR (KBr) cm-1: 3183 (NH), 1653 (C=O). MS
(m/z): 230 (M ? 1). Anal. Calcd. for C17H17NO4: C, 68.21;
H, 5.72; N, 4.68. Found: C, 68.46; H, 5.89; N, 4.47.
7-(2,6-Dichlorobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (20)
M.p. 126–128°C; yield 27%. 1H-NMR (DMSO, 300 MHz):
d 3.28 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.20 (t, 2H,
J = 4.9 Hz, –OCH2–), 5.21 (s, 2H, Ar–CH2–), 6.98–7.58
(m, 7H, Ar–H), 8.37 (s, 1H, –NH–). IR (KBr) cm-1: 3179
(NH), 1683 (C=O). MS (m/z): 338 (M ? 1). Anal. Calcd.
for C16H13Cl2NO3:C, 56.82; H, 3.87; N, 4.14. Found: C,
56.97; H, 3.96; N,4.01.
7-(3,4-Dimethoxybenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (25)
M.p. 134–136°C; yield 36%. 1H-NMR (DMSO,
300 MHz): d 3.24 (q, 2H, J = 5.0 Hz, –NHCH2–), 3.75
(m, 6H, –OCH3), 4.18 (t, 2H, J = 4.9 Hz, –OCH2–), 4.99
(s, 2H, Ar–CH2–), 6.95–7.26 (m, 7H, Ar–H), 8.33 (s, 1H,
–NH–). IR (KBr) cm-1: 3172 (NH), 1676 (C=O). MS
(m/z): 330 (M ? 1). Anal. Calcd. for C18H19NO5: C, 65.74;
H, 5.81; N, 4.25. Found: C, 65.89; H, 5.87; N, 4.18.
7-(4-Bromobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (21)
M.p. 169–171°C; yield 84%. 1H-NMR (DMSO, 300 MHz):
d 3.24 (q, 2H, J = 5.0 Hz, –NHCH2–), 4.18 (t, 2H,
J = 4.9 Hz, –OCH2–), 5.07 (s, 2H, Ar–CH2–), 6.95–7.60
(m, 7H, Ar–H), 8.34 (s, 1H, –NH–). IR (KBr) cm-1: 3182
(NH), 1663(C=O). MS (m/z): 348 (M ? 1). Anal. Calcd. for
C16H14BrNO3: C, 55.19; H, 4.05; N, 4.02. Found: C, 55.38;
H, 3.84; N,4.26.
Pharmacology
The anticonvulsant activity of all the compounds was
evaluated. The in vivo anticonvulsant activity was assessed
by use of the standard described in the ADD program
(Krall et al., 1978; Porter et al., 1984). The acute toxicity
was evaluated by a rotarod test (Krall et al., 1978; Porter
et al., 1984). In the rotarod test, hypnotic activity was
found in some compounds, so the hypnotic effect of
compound 10 was initially investigated by using the pen-
tobarbital-induced-sleep test (Tsuji et al., 1996). All of the
compounds, which were dissolved in 3% Tween-80, were
evaluated for their anticonvulsant activity and compound
10 was evaluated for its hypnotic activity using KunMing
mice, ranging in weight from 18 to 25 g and purchased
7-(2-Bromobenzyloxy)-3,4-dihydrobenzo[f][1,4]
oxazepin-5(2H)-one (22)
M.p. 159–161°C; yield 58%. 1H-NMR (DMSO, 300 MHz):
d 3.27 (q, 2H, J = 5.1 Hz, –NHCH2–), 4.20 (t, 2H,
J = 5.0 Hz, –OCH2–), 5.10 (s, 2H, Ar–CH2–), 6.98–7.69
(m, 5H, Ar–H), 8.34 (s, 1H, –NH–). IR (KBr) cm-1: 3240
123

Med Chem Res (2011) 20:996–1004
1001
from the Laboratory of Animal Research, College of
Pharmacy, Yanbian University.
Results and discussion
Chemistry
Anticonvulsant activity and toxicity test in mice
6-Methoxy-2,3-dihydrochromen-4-one (1) was prepared by
the method reported by Cai et al., (2006). The Beckmann
rearrangement reaction is a good method to obtain seven-
membered heterocyclic amides, especially the 1,4-ben-
zoxazepin-5(2H)-ones (Bhalerao and Thyagarajan, 1968).
In this study, 6-methoxy-2,3-dihydrochromen-4-one (1)
reacted with hydroxylamine chloride to form 6-methoxy-
2,3-dihydrochromen-4-one oxime (2) with a high yield,
which then, under the Lewis acid condition, using PPA in
this case, became compound 3. In this step, the product in
the Beckmann rearrangement reaction was mostly the
expected product, 7-methoxy-3,4-dihydrobenzo[f][1,4]ox-
azepin-5(2H)-one (compound 3), rather than the regio-
isomer. This might be ascribed to the greater difficulty for
the aryl group to migrate. Demethylation of compound 3
by treatment with dichloromethane and boron tribromide,
as described by Bauer, produced 7-hydroxy-3,4-dihydro-
benzo[f][1,4]oxazepin-5(2H)-one (compound 4) (Bauer
et al., 1995). Then, compounds 5–25 were synthesized
through the reaction of compound 4 with halogenated
hydrocarbon and K2CO3 in ethanol.
The MES test was carried out by the methods described in
the ADD of the National Institutes of Health (USA).
Seizures were elicited with a 60 Hz alternating current of
50 mA intensity in mice (100% elicitation rate in normal
mice). The current was applied via corneal electrodes for
0.2 s. Protection against the spread of MES-induced sei-
zures was defined as the abolition of the hind leg and
tonic maximal extension component of the seizure. At
30 min after the administration of the compounds, the
activities were evaluated in MES test. In phase-I screen-
ing, each compound was administered at the dose levels of
30, 100, and 300 mg/kg for evaluating the preliminary
anticonvulsant activity. For determination of the median
effective dose (ED50) the median toxic dose (TD50), the
phase-II screening was prepared. Groups of ten mice were
given a range of intraperitoneal injection doses of the
tested compound until at least three points were estab-
lished in the range of 10–90% seizure protection or
minimal observed neurotoxicity. From the plot of this
data, the respective ED50 and TD50 values, 95% confi-
dence intervals, slope of the regression line, and the
standard error of the slope were calculated by means of a
computer program written at National Institute of Neuro-
logical Disorders and Stroke.
Pharmacology
As with any other class of drugs, the preclinical discovery
and development of a new chemical entity for the treatment
of epilepsy rely heavily on the use of predictable animal
models. At present, there are three in vivo models that are
routinely used by most AED discovery programs. They
include the MES, the subcutaneous pentylenetetrazol (sc-
PTZ), and the kindling model. Of these, the MES and sc-
PTZ seizure models represent the two animal seizure
models most widely used in the search for new AEDs
(White, 2003). In this study, the MES seizure model was
used for preliminary (phase I) screening of target com-
pounds 5–25 (Table 1). The results indicated that com-
pounds 6, 8, 9, 10, 13, 15, and 16 displayed anticonvulsant
activity at 100 mg/kg, while the others displayed anticon-
vulsant activity at a dose of 300 mg/kg. Almost all of these
compounds exhibited neurotoxicity at a dose of 300 mg/kg,
according to the initial rotarod test. Some compounds that
displayed anticonvulsant activity 4 h after administration
and no activity 12 h after administration were expected to
have long-acting effects.
The neurotoxicity of the compounds was measured in
mice by the rotarod test. The mice were trained to stay on
an accelerating rotarod of diameter 3.2 cm that rotates at
10 rpm. Trained animals were given i.p. injection of the
test compounds. Neurotoxicity was indicated by the
inability of the animal to maintain equilibrium on the rod
for at least 1 min in each of the trials.
Pentobarbital-induced-sleep test in mice
Male and female mice (20–25 g) were averagely divided
into seven groups of ten and housed in a breeding room
with a 12 h light–dark cycle at 24 1°C. Compound 10
and the zopiclone were dissolved in 3% Tween-80. Each
group was i.p. injected with different doses of 10 and
zopiclone (10, 30, and 60 mg/kg) 30 min before the
intraperitoneal administration of pentobarbital sodium
(45 mg/kg). Sleep time was considered as the difference
between the time of loss and recovery of the righting reflex.
A control group was i.p. treated with 3% Tween-80 alone
to determine the duration of the hypnosis. The results were
analyzed using one-way-ANOVA followed by Dunnet’s
test.
Compounds 6, 8, 9, 10, 13, 15, and 16 were then
subjected to phase II trials for the quantification of their
anticonvulsant activity and neurotoxicity in mice. The
data were also compared with the marketed anticonvul-
sant drug phenobarbital (Table 2). The most active
123

1002
Med Chem Res (2011) 20:996–1004
Table 1 Phase I anticonvulsant and toxicity data in mice (i.p.)
Compds.
R
Dosage (mg/kg)
MES
0.5 h
Dosage (mg/kg)
Rotarod
0.5 h
4 h
4 h
5
–C2H5
100
100
100
100
100
30
1/3
3/3
2/3
3/3
3/3
2/3
2/3
3/3
3/3
3/3
3/3
3/3
1/3
2/3
3/3
0/3
3/3
1/3
0/3
0/3
0/3
0/3
0/3
2/3
1/3
2/3
0/3
1/3
1/3
1/3
3/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
100
100
100
100
100
100
100
300
100
300
100
100
100
100
300
100
300
100
100
100
100
0/3
3/3
3/3
3/3
3/3
3/3
2/3
3/3
1/3
2/3
3/3
3/3
3/3
3/3
3/3
3/3
3/3
3/3
3/3
0/3
3/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
6
n–C3H7
7
n–C4H9
8
n–C5H11
9
n–C6H13
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
n–C7H15
n–C8H17
100
300
100
300
100
100
100
100
300
100
300
100
100
100
100
n–C12H25
–CH2C6H5
–CH2C6H4 (p-F)
–CH2C6H4 (m-F)
–CH2C6H4 (o-F)
–CH2C6H4 (p-Cl)
–CH2C6H4 (m-Cl)
–CH2C6H4 (o-Cl)
–CH2C6H3 (2,6-Cl2)
–CH2C6H4(p-Br)
–CH2C6H4(o-Br)
–CH2C6H4(p-CH3)
–CH2C6H4(p-OCH3)
–CH2C6H3(3,4-(OCH3)2)
Table 2 Phase II quantitative anticonvulsant data in mice (i.p.)
Compds.
R
ED50 (mg/kg) (MES)
TD50 (mg/kg) (Rotarod)
PI
6
n–C3H7
78.3 (66.8 * 91.9)
56.8 (49.2 * 65.5)
47.3 (41.0 * 54.6)
19.0 (16.2 * 22.3)
73.1 (63.3 * 84.3)
73.1 (63.4 * 84.3)
45.6 (39.5 * 52.6)
21.8 (19.8 * 25.5)
11.8 (9.7–14.1)
169.7 (144.6 * 199.1)
105.7 (94.4 * 118.3)
105.7 (93.8 * 118.3)
47.3 (40.3 * 55.5)
76.2 (66.1 * 87.9)
73.1 (63.4 * 84.3)
52.8 (45.8 * 60.9)
69.0 (62.8 * 72.9)
76.1 (69.1–83.7)
2.2
1.9
2.2
2.5
1.0
1.0
1.2
3.2
6.4
8
n–C5H11
n–C6H13
n–C7H15
–CH2C6H5
–CH2C6H4 (m-F)
–CH2C6H4 (o-F)
–
9
10
13
15
16
Phenobarbital
Carbamazepine
–
compound was found to be 7-(heptyloxy)-3,4-dihydro-
benzo[f][1,4]oxazepin-5(2H)-one (10), which had an
ED50 value of 19.02 mg/kg and a protective index
(PI = TD50/ED50) value of 2.49. The compound 10 had
better anticonvulsant activity than phenobarbital, but it
exhibited higher neurotoxicity.
increase in ED50, and the compound 10, with the n-hep-
tyloxy substituted group, was the most active. The trend
reversed, however, when the alkyl chain had more than
seven carbon numbers. This suggested that the compound
with the n-heptyloxy substituted group had the optimal
lipid–water partition coefficient to cross the blood–brain
barrier.
The length of the alkyl chain appeared to have a direct
impact on the anticonvulsant activity of the 7-alkyloxyl
derivatives. From compounds 5–10, the increase in the
length of the alkyl chain, from 2 to 7, paralleled the gradual
Some halogen-substituted derivatives were designed and
synthesized in this study. Of those derivatives (14–22), only
7-(2-fluorobenzyloxy)-3,4-dihydrobenzo[f][1,4]oxazepin-
123

Med Chem Res (2011) 20:996–1004
1003
Conclusions
***
60
***
***
A series of 7-substituted-3,4-dihydrobenzo[f][1,4]oxaze-
pin-5(2H)-ones was synthesized. The anticonvulsant effect
and neurotoxicity of the compounds were calculated with a
MES test and a rotarod test with intraperitoneally injected
mice. The results showed that all of the derivatives
exhibited anticonvulsant activities. Among the synthesized
compounds, 7-(heptyloxy)-3,4-dihydrobenzo[f][1,4]oxaze-
pin-5(2H)-one (10) was the most active. In the anti-MES
potency test, it showed a stronger activity with median
effective dose (ED50) of 19.0 mg/kg compare with the
reference drug phenobarbital (ED50 = 21.8 mg/kg). How-
ever, the value PI (2.49) of it is lower than phenobarbital
(PI = 3.17). The hypnotic effect of compound 10 was also
initially investigated in the pentobarbital-induced-sleep
test, and the results revealed that it could prolong the
duration of the hypnosis induced by pentobarbital in a
dose-dependent manner.
40
20
0
Fig. 2 Acute effects of compound 10 and zopiclone on the
pentobarbital-induced-sleep test. Derivatives were injected i.p.
30 min before intraperitoneally injected (45 mg/kg) of pentobarbital
sodium. Data represent means SEM of time between loss and
recovery of the righting reflex. *** P \ 0.001
Acknowledgments This work was supported by the National Nat-
ural Science Foundation of China (No. 30860340).
5(2H)-one (15) and 7-(3-fluorobenzyloxy)-3,4-dihydro-
benzo[f][1,4]oxazepin-5(2H)-one (16) possessed relatively
strong anticonvulsant activity with ED50 values of 73.1
and 45.6 mg/kg, respectively. All of the benzyloxy-
substituted derivatives displayed lower anticonvulsant
activity than that of the proper length alkoxyl-substituted
derivatives. In those benzyloxy-substituted derivatives,
different halogen atom substitutions contributed to the
anticonvulsant activity in the order of F [ Cl [ Br; the
introduction of an F atom on the benzyl ring increased
the anticonvulsant activity in the o position but not in the
m and p positions. Three electron-donor benzyloxy
derivatives were also designed and prepared, containing
p-CH3, p-OCH3, 3,4-(OCH3)2, respectively. The phar-
macology test revealed that their activities were obvi-
ously lower than the halogen-substituted derivatives.
The hypnotic effect of compound 10 was initially
investigated by using the pentobarbital-induced-sleep test
which was most widely used in the evaluation of hypnotic
effect. Zopiclone was used as the positive control. A low
dose of 10 (10 mg/kg) did not increase the duration of
hypnosis induced by pentobarbital (Fig. 2), the middle dose
of 10 (30 mg/kg) slightly increased the pentobarbital-
induced-sleep time without significant difference, while the
high dose of 10 (60 mg/kg) can significantly increased the
pentobarbital-induced-sleep time from 20.9 2.31 to
45.7 4.76 min. As shown in the Fig. 2, the activity of
compound 10 was close to that of zopiclone at the high
dose. It was clear that compound 10 could prolong the
duration of the hypnosis induced by pentobarbital in a
dose-dependent manner.
References
Al-Soud YA, Al-Masoudi NA, Ael-R Ferwanah (2003) Synthesis and
properties of new substituted 1, 2, 4-triazoles: potential antitu-
mor agents. Bioorg Med Chem 11:1701–1708
Bauer U, Amaro AR, Robertson LW (1995) A new strategy for the
synthesis of polychlorinated biphenyl metabolites. Chem Res
Toxicol 8:92–95
Bhalerao UT, Thyagarajan G (1968) Schmidt rearrangement of
chromanones. Can J Chem 46:3367–3374
Cai J, Li MD, Zhang JY, Zhou W, Hua WY, Ji M (2006) Synthesis of
3-amino-6-methoxy-3, 4-dihydro-2H-[1]benzopyran-4-one hydro-
chloride, an important intermediate of PD128907. Chinese J
New Drugs 15:987–989
Krall RL, Penry JK, White BG, Kupferberg HJ, Swinyard EA (1978)
Antiepileptic drug development: II. Anticonvulsant drug screen-
ing. Epilepsia 19:409–428
Kwan P, Brodie MJ (2000) Early identification of refractory epilepsy.
N Engl J Med 342:314–319
Meador KJ (2003) Newer anticonvulsants: dosing strategies and
cognition in treating patients with mood disorders and epilepsy.
J Clin Psychiatry 64(Suppl. 8):30–34
Piao ZT, Guan LP, Zhao LM, Piao HR, Quan ZS (2008) Synthesis of
novel 7-benzylamino-2H–1, 4-benzoxazin-3(4H)-ones as anti-
convulsant agents. Eur J Med Chem 43:1216–1221
Porter RJ, Cereghino JJ, Gladding GD, Hessie BJ, Kupferberg HJ,
Scoville B, White BG (1984) Antiepileptic drug development
program. Cleve Clin Q 51:293–305
Quan ZS, Wang JM, Rho JR, Kwak KC, Kang HC, Qun CS, Chai KY
(2005) Synthesis of 6-alkyloxyl-3, 4-dihydro-2(1H)-quinoliones
and their anticonvulsant activities bull Korean. Chem Soc
26:1757–1760
Spear BB (2001) Pharmacogenetics and antiepileptic drugs. Epilepsia
42:31–34
123

1004
Med Chem Res (2011) 20:996–1004
Strine TW, Kobau R, Chapman DP, Thurman DJ, Price P, Balluz
LS (2005) Psychological distress, comorbidities, and health
behaviors among U.S. adults with seizures: results from the
2002 National Health Interview Survey. Epilepsia 46:1133–
1139
Tsuji R, Isobe N, Kawasaki H (1996) Mechanism of prolongation of
pentobarbital-induced sleeping time by empenthrin in mice.
Toxicology 108:185–190
White HS (2003) Preclinical development of antiepileptic drugs: past,
present, and future directions. Epilepsia 44(Suppl 7):2–8
123