Synthesis and anticonvulsant activity of 1-substituted-7-benzyloxy-4,5- dihydro-[1,2,4]triazolo[4,3-a]quinoline

Article abstract of DOI:10.1248/bpb.28.1216

Starting from 6-hydroxy-3,4-dihydro-1H-quinoline-2-one, a series of 1-substituted-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines was synthesized and their structures were characterized using IR, ¹H-NMR, MS, and elemental analysis techniques. Anticonvulsant activity was evaluated in the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scMet) test, and rotarod neurotoxicity test. The most active compound was 7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4a. Its ED₅₀ in the MES and scMet tests was 17.3 and 24mg·kg^-1, respectively. The safest compound was 4g, 1-phenyl-7-benzyloxy-4,5-dihydro-[1,2, 4]triazolo[4,3-a]quinoline, with TD₅₀ and protective index (PI) (PI=TD₅₀/ED₅₀) values of greater than 300mg·kg ^-1 and 13, respectively. The PI value of compound 4g was better than that of most marketed drugs. Structure-activity relationships are also described in this paper.

Full text of DOI:10.1248/bpb.28.1216

1216
Biol. Pharm. Bull. 28(7) 1216—1220 (2005)
Vol. 28, No. 7
Synthesis and Anticonvulsant Activity of 1-Substituted-7-Benzyloxy-4,5-
dihydro-[1,2,4]triazolo[4,3-a]quinoline
a
a
a
a
b
,a
*
Li-Jing CUI, Zhi-Feng XIE, Hu-Ri PIAO, Gao LI, Kyu-Yun CHAI, and Zhe-Shan QUAN
a College of Pharmacy, Yanbian University; Yanji, Jilin 133000, P. R. China: and b Department of Chemistry, Wonkwang
University; Iksan 570–749, Korea. Received January 17, 2005; accepted March 17, 2005
Starting from 6-hydroxy-3,4-dihydro-1H-quinoline-2-one, a series of 1-substituted-7-benzyloxy-4,5-dihydro-
[1,2,4]triazolo[4,3-a]quinolines was synthesized and their structures were characterized using IR, 1H-NMR, MS,
and elemental analysis techniques. Anticonvulsant activity was evaluated in the maximal electroshock (MES)
test, subcutaneous pentylenetetrazol (scMet) test, and rotarod neurotoxicity test. The most active compound was
7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4a. Its ED50 in the MES and scMet tests was 17.3 and
24 mg·kgꢀ1, respectively. The safest compound was 4g, 1-phenyl-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline, with TD50 and protective index (PI) (PIꢁTD50/ED50) values of greater than 300 mg·kgꢀ1 and 13, re-
spectively. The PI value of compound 4g was better than that of most marketed drugs. Structure–activity rela-
tionships are also described in this paper.
Key words [1,2,4]triazolo[4,3-a]quinoline; anticonvulsant; maximal electroshock test; pentylenetetrazole; neurotoxicity
Epilepsy, one of the most common neurologic diseases, is CHEMISTRY
characterized by epileptic seizures, which are evoked by un-
expected, high-level neuronal discharges in the brain.1) Since
Melting points were determined in open capillary tubes
the anticonvulsant agents currently used in the treatment of and are uncorrected. IR spectra were recorded (in KBr ) on a
epilepsy have certain disadvantages such as notable side ef- FT-IR1730, 1H-NMR spectra were measured on a BRUKER-
fects and inefficient therapy in some seizure types, a clear 300, and all chemical shifts are given in ppm relative to
need for safer and more effective antiepileptic drugs is well tetramethysilane. Mass spectra were measured on an
known.1—3) Therefore the development of new antiepileptic AP12000 (EIS, 70 eV). Elemental analyses were performed
drugs with approved therapeutic properties is an important on a Pekin-Elmer 204Q. Microanalyses of C, N, and H were
challenge for medicinal chemists.
performed using a Heraeus CHN Rapid Analyzer.
The derivatives of triazole exhibit a variety of activities
6-Hydroxy-3,4-dihydro-1H-quinoline-2-one
1 6-Hy-
such as antitumor,4) antiinflammatory,5) antimicrobial,6,7) an- droxy-3,4-dihydro-2-(1H)-quinoline-2-one was prepared
tifugal,8) antithrombotic,9) antiplatelet,10) antiviral,11) and anti- from phenylamine and 3-chloro-propionylchloride using the
convulsant activities.12—14) In our search for new compounds method described previously,15) the total yield was 59%, mp
with anticonvulsant activity, 6-benzyloxy-3,4-dihydro-1H- 234—236 °C (value in the literature, 235—236 °C).
quinoline-2-one was found although its activity is low. To in-
6-Benzyloxy-3,4-dihydro-1H-quinoline-2-one 2
crease its anticonvulsant activity and taking into account the Sodium hydroxide (0.09 mol), 60 ml of absolute ethanol, and
anticonvulsant activity of triazole, we incorporated triazole 6-hydroxy-3,4-dihydro-(1H)-quinoline-2-one (0.03 mol) were
with 6-benzyloxy-3,4-dihydro-1H-quinolinone at the first added to a 100 ml round-bottomed flask equipped with a re-
and second position of the latter and obtained 7-benzyloxy- flux condenser, and chloromethyl–benzene (0.36 mol) was
4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline with more potent added dropwise to the mixture. The reaction mixture was re-
activity. To search for better compounds and elucidate struc- fluxed for 2.5 h and cooled. After being poured into 100 ml
ture–activity relationships, a series of 1-substituted-7-benzyl- of ice-water, a white solid was obtained through filtration,
oxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines was synthe- which was dried in a vacuum and recrystallized in
1
sized and their structures were characterized using IR, H- hexane–ethannol (5 : 1), with a yield of 72%. mp 159—
NMR, MS, and elemental analysis techniques. The anticon- 161 °C. IR (KBr) cmꢀ1: 3432 (N–H), 1675 (CꢁO), 1238,
1
vulsant activity was evaluated using the maximal eletroshock 1056 (C–O–C). H-NMR (CDCl3) d: 2.39 (t, 2H, Jꢁ7.1 Hz,
(MES) test and the subcutaneous pentylenetetrezole (sc-Met) CH2), 2.82 (t, 2H, Jꢁ7.1 Hz, CH2), 5.02 (s, 2H, CH2), 6.75—
test. Neurotoxicity was evaluated using the rotarod test.
6.87 (m, 3H, C6H3–), 7.31—7.46 (m, 5H, C6H5–), 9.94 (s,
Fig. 1. Synthesis of Compounds 4a—n
∗ To whom correspondence should be addressed. e-mail: zsquan@ybu.edu.cn
© 2005 Pharmaceutical Society of Japan

July 2005
1217
7-Benzyloxy-1-pentyl-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4d: Yieldꢁ72%, mp 88—90 °C. IR (KBr) cmꢀ1:
1615 (CꢁN), 1292 (C–N), 1242, 1028 (C–O–C), 1140
1H, NH). MS: (Mꢂ1) 254. Anal. Calcd for C16H15NO2: C,
75.87; H, 5.97; N, 5.53. Found: C, 75.71; H, 5.73; N, 5.38.
6-Benzyloxy-3,4-dihydro-1H-quinoline-2-thione 3
Some improvements were made based on the method de-
scribed previously.16) Acelonitrile 30 ml and triethylamine
20 ml were placed in a three-necked round-bottomed flask, to
which P2S5 1.3 g was added slowly in an ice bath and stirred
until dissolved. Then 2 was added with stirring. The mixture
was refluxed for 3 h in a nitrogen atmosphere. After remov-
ing the solvent under reduced pressure, the residue was dis-
solved in 30 ml of dichloromethane, washed with water
(30ꢃ3), and dried over anhydrous MgSO4. Evaporation of
the solvents gave a crude product that was purified by recrys-
tallization in hexane–ethanol (10 : 1) and a yellow solid was
obtained in a yield of 68%. mp 156—159 °C. IR (KBr) cmꢀ1:
1
(N–N). H-NMR (CDCl3) d: 0.91 (t, 3H, Jꢁ7.2 Hz, CH3),
1.25—1.47 (m, 6H, CH2), 1.88—1.92 (m, 2H, CH2), 2.96 (t,
2H, Jꢁ6.6 Hz, CH2), 3.04 (t, 2H, Jꢁ7.6 Hz, CH2), 3.11 (t,
2H, Jꢁ7.6 Hz, CH2), 5.10 (s, 2H, OCH2), 6.95 (d, 1H, Jꢁ9.2
Hz, H-8), 6.98 (s, 1H, H-6), 7.38 (d, 1H, Jꢁ9.2 Hz, H-9),
7.26—7.45 (m, 5H, C6H5) MS: (Mꢂ1) 348.1. Anal. Calcd
for C22H25N3O: C, 76.05; H, 7.25; N, 12.09. Found: C, 75.78;
H, 7.54; N, 12.32.
1-Benzyl-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4e: Yieldꢁ78%, mp 94—96 °C. IR (KBr)
cmꢀ1:1610 (CꢁN), 1296 (C–N), 1246, 1026 (C–O–C), 1132
1
(N–N). H-NMR (CDCl3) d: 2.95 (t, 2H, Jꢁ7.0 Hz, CH2),
1
3.14 (t, 2H, Jꢁ7.0 Hz, CH2), 4.42 (s, 2H, CH2), 5.05 (s, 2H,
OCH2), 6.79 (dd, 1H, Jꢁ2.4, 8.8 Hz, H-8), 6.95 (d, 1H,
Jꢁ2.0 Hz, H-6), 7.14 (d, 1H, Jꢁ8.8 Hz, H-9), 7.16—7.38 (m,
10H, 2ꢃC6H5) MS: (Mꢂ1) 368. Anal. Calcd for C24H21N3O:
C, 78.45; H, 5.76; N, 11.44. Found: C, 78.74; H, 5.82; N,
11.83.
3437 (N–H), 1237, 1052 (C–O–C). H-NMR (CDCl3) d:
2.74 (t, 2H, Jꢁ7.4 Hz, CH2), 2.89 (t, 2H, Jꢁ7.4 Hz, CH2),
5.05 (s, 2H, CH2), 6.85—7.03 (m, 3H, C6H3), 7.32—7.44 (m,
5H, C6H5), 12.14 (s, 1H, NH). MS: (Mꢂ1) 270. Anal. Calcd
for C24H21N3O: C, 71.34; H, 5.61; N, 5.20. Found: C, 71.74;
H, 5.82; N, 5.33.
7-Benzyloxy-1-(4-chloro-benzyl)-4,5dihydro-[1,2,4]tri-
azolo[4,3-a]quinoline 4f: Yieldꢁ80%, mp 176—178 °C. IR
(KBr) cmꢀ1 1612 (CꢁN), 1308 (C–N), 1242, 1022
General Procedure for the Synthesis of 1-Substituted-
7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines
4a—n The method described previously was used with
some improvements. Compound 3, suitable acylhydrazine,
and cyclohexanol 60 ml were added to a 100 ml three-necked
round-bottomed flask, and the mixture was refluxed for 6 h in
a nitrogen atmosphere. Solvents were removed under reduced
pressure, and the residue was extracted twice with
dichloromethane 30 ml. The dichloromethane layer was
washed three times with water (30ꢃ3) and dried over anhy-
drous MgSO4. After removing the solvents, products was pu-
rified by silica gel column chromatography (dichloromethane :
methanolꢁ10 : 1).
7-Benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline
4a: Yieldꢁ64.5%, mp 174—176 °C. IR (KBr) cmꢀ1: 1614
(CꢁN), 1311 (C–N), 1255, 1022 (C–O–C), 1155 (N–N). 1H-
NMR (CDCl3) d: 3.03 (t, 2H, Jꢁ7.2 Hz, CH2), 3.22 (t, 2H,
Jꢁ7.4 Hz, CH2), 5.09 (s, 2H, CH2), 6.94—7.24 (m, 3H, H-6,
H-8, H-9), 7.26—7.42 (m, 5H, C6H5), 8.67 (s, 1H, H-1). MS:
(Mꢂ1) 278. Anal. Calcd for C17H15N3O: C, 73.63; H, 5.45;
N, 15.15. Found: C, 73.41; H, 5.63; N, 15.38.
1
(C–O–C), 1126 (N–N). H-NMR (CDCl3) d: 2.98 (t, 2H,
Jꢁ7.6 Hz, CH2), 3.12 (t, Jꢁ7.6 Hz, 2H, CH2), 4.44 (s, 2H,
CH2), 5.03 (s, 2H, CH2), 6.77 (dd, Jꢁ2.6, 8.8 Hz , 1H, H-8),
6.93 (d, Jꢁ2.4 Hz, 1H, H-6), 7.17 (d, Jꢁ8.8 Hz, 1H, H-9),
7.13—7.40 (m, 9H, C6H5, C6H4) MS: (Mꢂ1) 403. Anal.
Calcd for C24H20ClN3O: C, 71.73; H, 5.02; N, 10.46. Found:
C, 71.48; H, 5.13; N, 10.17.
7-Benzyloxy-1-phenyl-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4g: Yieldꢁ72%, mp 147—150 °C. IR (KBr)
cmꢀ1: 1610 (CꢁN), 1306 (C–N), 1250, 1012 (C–O–C), 1097
1
(N–N). H-NMR (CDCl3) d: 3.04 (t, 2H, Jꢁ6.8 Hz, CH2),
3.18 (t, 2H, Jꢁ6.8 Hz, CH2), 5.05 (s, 2H, CH2), 6.66 (dd, 1H,
Jꢁ2.8, 8.8 Hz, H-8), 6.81 (d, 1H, Jꢁ8.8 Hz, H-9), 6.97 (d,
1H, Jꢁ2.4 Hz, H-6), 7.34—7.63 (m, 10H, 2ꢃC6H5). MS:
(Mꢂ1) 354.2. Anal. Calcd for C23H19N3O: C, 78.16; H, 5.42;
N, 11.89. Found: C, 77.81; H, 5.61; N, 11.57.
7-Benzyloxy-1-(3-methoxy-phenyl)-4,5-dihydro-[1,2,4]tri-
azolo[4,3-a]quinoline 4h: Yieldꢁ92%, mp 126—128 °C. IR
(KBr) cmꢀ1: 1614 (CꢁN), 1290 (C–N), 1252, 1028
7-Benzyloxy-1-methyl-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4b: Yieldꢁ71%, mp 116—118 °C. IR (KBr)
cmꢀ1:1620 (CꢁN), 1290 (C–N), 1244, 1026 (C–O–C), 1134
1
(C–O–C), 1144 (N–N). H-NMR (CDCl3) d: 3.04 (t, 2H,
Jꢁ6.8 Hz, CH2), 3.18 (t, 2H, Jꢁ7.0 Hz, CH2), 3.82 (s, 3H,
CH3), 5.04 (s, 2H, CH2), 6.67 (dd, 1H, Jꢁ2.4, 8.8 Hz, H-8),
6.86 (d, 1H, Jꢁ8.8 Hz, H-9), 6.97 (d, 1H, Jꢁ2.4 Hz, H-6),
7.06—7.41 (m, 9H, C6H5, C6H4). MS: (Mꢂ1) 384. Anal.
Calcd for C24H21N3O2: C, 75.18; H, 5.52; N, 10.96. Found:
C, 75.29; H, 5.35; N, 11.14.
1
(N–N). H-NMR (CDCl3) d: 2.74 (s, 3H, CH3), 2.96 (t, 2H,
Jꢁ6.8 Hz, CH2), 3.11 (t, 2H, Jꢁ6.6 Hz, CH2), 5.03 (s, 1H,
OCH2), 6.94 (dd, 1H, Jꢁ2.8, 8.8 Hz, H-8), 6.98 (d, 1H,
Jꢁ2.8 Hz, H-6), 7.39 (d, 1H, 9.0 Hz, H-9), 7.35—7.44 (m,
5H, C6H5). MS: (Mꢂ1) 292. Anal. Calcd for C18H17N3O: C,
74.20; H, 5.88; N, 14.42. Found: C, 74.52; H, 5.62; N, 14.10.
7-Benzyloxy-1-propyl-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4c: Yieldꢁ75%, yellow oil. IR (KBr) cmꢀ1: 1612
(CꢁN), 1295 (C–N), 1254, 1026 (C–O–C), 1134 (N–N). 1H-
NMR (CDCl3) d: 1.07 (t, 3H, Jꢁ7.2 Hz, CH3), 1.88—1.96
(m, 2H, CH2), 2.95 (t, 2H, Jꢁ6.8 Hz, CH2), 3.01 (t, 2H,
Jꢁ7.6 Hz, CH2), 3.11 (t, 2H, Jꢁ7.5 Hz, CH2), 5.09 (S, 2H,
OCH2), 6.94 (dd, 1H, Jꢁ2.8, 9.2 Hz, H-8), 6.98 (d, 1H,
Jꢁ2.8 Hz, H-6), 7.39 (d, 1H, 9.2 Hz, H-9), 7.26—7.44 (m,
5H, C6H5). MS: (Mꢂ1) 320. Anal. Calcd for C20H21N3O: C,
75.21; H, 6.63; N, 13.16. Found: C, 75.54; H, 6.87; N, 13.39.
7-Benzyloxy-1-m-tolyl-4,5-dihydro-[1,2,4]triazolo[4,3-
a]quinoline 4i: Yieldꢁ78%, mp 138—140 °C. IR (KBr)
cmꢀ1: 1610 (CꢁN), 1290 (C–N), 1250, 1045 (C–O–C), 1142
1
(N–N). H-NMR (CDCl3) d: 2.40 (s, 3H, CH3), 3.06 (t, 2H,
Jꢁ7.0 Hz, CH2), 3.23 (t, 2H, Jꢁ6.8 Hz, CH2), 5.05 (s, 2H,
CH2), 6.67 (dd, 1H, Jꢁ2.4, 8.8 Hz, H-8), 6.86 (d, 1H, Jꢁ8.8
Hz, H-9), 6.98 (d, 1H, Jꢁ2.4 Hz, H-6), 7.26—7.49 (m, 9H,
C6H5, C6H4). MS: (Mꢂ1) 368. Anal. Calcd for C24H21N3O:
C, 78.45; H, 5.76; N, 11.44. Found: C, 78.22; H, 5.94; N,
11.44.
7-Benzyloxy-1-(3-chloro-phenyl)-4,5-dihydro-[1,2,4]tri-

1218
Vol. 28, No. 7
Table 1. Phase I Anticonvulsant and Toxicity Data in Mice (i.p.)a)
MESb) ScMetc)
azolo[4,3-a]quinoline 4j: Yieldꢁ80%, mp 174—176 °C. IR
(KBr) cmꢀ1: 1620 (CꢁN), 1294 (C–N), 1248, 1043
(C–O–C), 1151 (N–N). H-NMR (CDCl3) d: 3.04 (t, 2H,
Rotarod toxicity
1
Compd.
Jꢁ6.6 Hz, CH2), 3.18 (t, 2H, Jꢁ6.8 Hz, CH2), 5.05 (s, 2H,
CH2), 6.70 (dd, 1H, Jꢁ2.4, 8.8 Hz, H-8), 6.82 (d, 1H, Jꢁ8.8
Hz, H-9), 6.99 (d, 1H, Jꢁ2.4 Hz, H-6), 7.26—7.66 (m, 9H,
C6H5, C6H4) MS: (Mꢂ1) 389. Anal. Calcd for C23H18ClN3O:
C, 71.22; H, 4.68; N, 10.83. Found: C, 71.39; H, 4.36; N,
11.12.
0.5 h
4 h
0.5 h
4 h
0.5 h
4 h
e)
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
30d)
30
100
300
100
—
—
—
—
300
100
—
100
—
—
—
—
100
—
100
100
300
—
300
—
100
100
100
—
—
—
—
—
—
—
100
100
100
300
—
—
—
300
300
—
—
—
100
300
—
—
—
—
—
—
—
—
—
—
7-Benzyloxy-1-(2,5-dichloro-phenyl)-4,5-dihydro-
[1,2,4]triazolo[4,3-a]quinoline 4k: Yieldꢁ60%, mp 172—
174 °C. IR (KBr) cmꢀ1: 1626 (CꢁN), 1296 (C–N), 1242,
30
100
100
—
—
100
—
—
—
—
—
—
—
—
1
1026 (C–O–C), 1155 (N–N), 600 (C–Cl). H-NMR (CDCl3)
d: 3.06 (t, 2H, Jꢁ6.8 Hz, CH2), 3.38 (t, 2H, Jꢁ6.8 Hz, CH2),
5.03 (s, 2H, CH2), 6.60 (d, 1H, Jꢁ9.2 Hz, H-9), 6.66 (dd, 1H,
Jꢁ2.4, 9.2 Hz, H-8), 6.97 (d, 1H, Jꢁ2.4 Hz, H-6), 7.26—
7.68 (m, 8H, C6H5, C6H4). MS: (Mꢂ1) 425. Anal. Calcd for
C23H17Cl2N3O: C, 65.41; H, 4.06; N, 9.95. Found: C, 65.27;
H, 4.38; N, 9.75.
—
30
—
—
—
300
—
—
—
—
a) All tested compounds were dissolved in polyethylene glycol-400. b) The maxi-
mal electroshock test was induced 30 min post administration of the tested compounds.
c) Subcutaneous pentylenetetrazol (85 mg·kgꢀ1) 30 min after the tested compounds
were administered for 30 min. d) Doses are denoted in mg·kgꢀ1
.
e) —ꢁno activity
7-Benzyloxy-1-pyridin-4-yl-4,5-dihydro-[1,2,4]tri-
azolo[4,3-a]quinoline 4l: Yieldꢁ77%, mp 176—179 °C. IR
(KBr) cmꢀ1: 1606 (CꢁN), 1309 (C–N), 1248, 1018
at 300 mg·kgꢀ1
.
1
tered at three dose levels (30, 100, and 300 mg/kg i.p., to a
total of 6 mice, using 2 for each dose) with anticonvulsant
activity and neurotoxicity assessed at 30-min and 4-h inter-
vals after administration. Anticonvulsant efficacy was mea-
sured in the MES test and the scMet test. In the MES test,
seizures were elicited with a 60 Hz alternating current of
50 mA intensity in mice. The current was applied via corneal
electrodes for 0.2 s. Abolition of the hind-leg tonic-extensor
component of the seizure indicated protection against the
spread of MES-induced seizures. The scMet test involved
subcutaneous injection of a convulsant dose (CD97) of
pentylenetetrazol (85 mg/kg in mice). Elevation of the
pentylenetrazol-induced seizure threshold was indicated by
the absence of clonic spasms for at least 5-s duration over a
30-min period following administration of the test com-
pound. Anticonvulsant drug-induced neurologic deficit was
detected in mice using the rotorod ataxia test.
(C–O–C), 1152 (N–N). H-NMR (CDCl3) d: 3.05 (t, 2H,
Jꢁ8 Hz, CH2), 3.17 (t, 2H, Jꢁ8 Hz, CH2), 5.05 (s, 2H, CH2),
6.71 (d, 1H, Jꢁ8 Hz, H-8), 6.83 (d, 1H, Jꢁ8 Hz, H-9), 7.00
(s, 1H, H-6), 7.33—7.40 (m, 5H, C6H5), 7.58 (d, 2H, Jꢁ4
Hz, H-2ꢄ, H-6ꢄ), 8.75 (d, 2H, Jꢁ4 Hz, H-3ꢄ, H-5ꢄ) MS:
(Mꢂ1) 355. Anal. Calcd for C22H18N4O: C, 74.56; H, 5.12;
N, 15.81. Found: C, 74.69; H, 5.01; N, 16.11.
7-Benzyloxy-1-phenoxymethyl-4,5-dihydro-[1,2,4]tri-
azolo[4,3-a]quinoline 4m: Yieldꢁ90%, mp 136—138 °C.
IR (KBr) cmꢀ1: 1608 (CꢁN), 1309 (C–N), 1252, 1020
1
(C–O–C), 1120 (N–N). H-MNR (CDCl3) d: 2.98 (t, 2H,
Jꢁ7.0 Hz, CH2, 3.18 (t, 2H, Jꢁ7.2 Hz, CH2), 5.09 (s, 2H,
CH2), 5.38 (s, 2H, CH2), 6.91 (dd, 1H, Jꢁ9.0, 2.2 Hz, H-8),
7.00 (d, 1H, Jꢁ2.2 Hz, H-6), 7.13 (d, 1H, Jꢁ9.0 Hz, H-9),
7.02—7.77 (m, 10H, 2ꢃC6H5). MS: (Mꢂ1) 384. Anal.
Calcd for C24H21N3O2: C, 75.18; H, 5.52; N, 10.96. Found:
C, 75.02; H, 5.80; N, 11.24.
The pharmacologic parameters estimated in phase I
screening were quantified for compounds 4a—c, 4e, 4g—i,
and 4l in phase II screening (Table 2). Anticonvulsant activ-
ity was expressed in terms of the median effective dose
(ED50), and neurotoxicity was expressed as the median toxic
dose (TD50). For determination of the ED50 and TD50 values,
groups of 10 mice were given a range of intraperitoneal
doses of the test drug 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 respec-
tive ED50 and TD50 values, 95% confidence intervals, slope
of the regression line, and the standard error of the slope
were calculated by means of a computer program written at
National Institue of Neurological Disorders and Stroke.
7-Benzyloxy-1-(4-chloro-phenoxymethyl)-4,5-dihydro-
[1,2,4]triazolo[4,3-a]quinoline 4n: Yieldꢁ88%, mp 104—
106 °C. IR (KBr) cmꢀ1: 1610 (CꢁN), 1294 (C–N), 1236,
1
1020 (C–O–C), 1140 (N–N). H-MNR (CDCl3) d: 2.98 (t,
2H, Jꢁ6.8 Hz, CH2), 3.16 (t, 2H, Jꢁ7.0 Hz, CH2), 5.09 (s,
2H, CH2), 5.36 (s, 2H, CH2), 6.93 (dd, 1H, Jꢁ2.8, 8.8 Hz, H-
8), 6.98 (d, 1H, Jꢁ2.8 Hz, H-6), 7.07 (d, 1H, Jꢁ8.8 Hz, H-9),
7.24—7.71 (m, 9H, C6H5, C6H4). MS: (Mꢂ1) 419. Anal.
Calcd for C24H20ClN3O2: C, 68.98; H, 4.82; N, 10.06. Found:
C, 69.24; H, 4.68; N, 10.21.
PHARMACOLOGY
The MES test, scMet test, and rotarod test were carried out
by the Antiepileptic Drug Development Program (ADD),
Epilepsy Branch, National Institutes of Health, Bethesda,
MD, U.S.A.17,18) All compounds were tested for anticonvul-
sant activity with C57B/6 mice in the 18—25 g weight range
purchased from the Laboratory of Animal Research, College
of Pharmacy, Yanbian University. The tested compounds
were dissolved in polyethylene glycol-400.
RESULTS AND DISCUSSION
Based on previous reports,12—14) we knew that trazoles
have activity against both major and minor seizures. The
MES test is regarded as the pharmacologic model of grand
mal, and the sc-Met test as the pharmacologic model of petit
mal seizures. Therefore we carried out those two tests to
In Phase I screeng (Table 1) each compound was adminis-

July 2005
1219
Table 2. Phase II Quantitative Anticonvulsant Data in Mice (Test Drug Administered i.p.)
a)
ED50
Rotarod toxicity
PIb)
Compd.
c)
MES
scMet
TD50
MES
scMet
4a
4b
4c
4e
4g
4h
4i
17.3 (14.8—20.4)e)
30.7 (26.1—36.1)
97.7 (84.0—113.7)
67.9 (59.6—77.4)
23.0 (18.8—28.0)
60.6 (52.9—69.4)
30.4 (27.2—34.1)
58.5 (45.9—74.5)
9.5 (8.1—10.4)
24.0 (21.6—26.7)
42.5 (35.4—50.9)
ꢅ100
ꢅ100
61.0 (56.5—65.9)
ꢅ100
58.9 (49.1—70.7)
ꢅ100
ꢅ300
ꢅ100
13.2 (5.8—15.9)
149 (123—177)
61.4 (51.4—73.3)
85.2 (78.1—92.9)
264
212 (177—254)
ꢅ300
237 (200—280)
183 (155—217)
176 (151—206)
65.5 (52.5—72.9)
71.6 (45.9—135)
69 (62.8—72.9)
426 (369—450)
3.5
2.8
2.7
3.1
2.6
2.0
ꢆ2.6
ꢆ2.1
ꢅ5
ꢆ2.4
3.1
ꢆ1.8
ꢆ0.22
ꢆ0.76
5.2
ꢅ13
3.9
6.0
3.0
6.9
8.1
3.2
1.6
4l
Phenytoind)
Carbamazepind)
Phenobarbitald)
Valproated)
8.8 (5.5—14.1)
21.8 (21.8—25.5)
272 (247—338)
2.9
a) Dose measured in mg·kgꢀ1
.
b) PIꢁTD50/ED50
.
c) Minimal neurotoxiciity was determined using the rotarod test after the tested compounds were administered for 30
min. d) Data from Huseyin et al., 1998.19) e) 95% confidence limits.
evaluate the anticonvulsant activity of the synthesized com- chlorine atom into the phenyl at the first position of the de-
pounds.
rivatives lead to a complete loss of potency, as seen in com-
The compounds were tested for anticonvulsant activity pounds 4f, 4j, 4k, and 4n, which did not exhibit any anticon-
using the procedures described previously.17,18) The initial vulsant activity in the MES test even at a dose of
evaluation (phase I) of anticonvulsant activity of synthesized 300 mg·kgꢀ1. Compounds substituted with a pyridine at the
compounds is presented in Table 1. The compounds were ad- first position exhibited less activity than those substituted
ministered intraperitoneally at three doses (30, 100, 300 with a phenyl. Compound 4l, which was substituted with
mg·kgꢀ1). Three tests were performed for each compound: pyridine at the first position, with an ED50 value of
MES-induced convulsions, sc-Met-induced convulsions, and 58.5 mg·kgꢀ1 in the MES test, was less active than com-
rotarod neurotoxicity test.
As a result of preliminary screening , compounds 4a—c, a phenyl at the first position.
pound 4g (ED50ꢁ23.0 mg·kgꢀ1) which was substituted with
4e, 4g—i, and 4l were subjected to phase II trials for quan-
The neurotoxicity of compounds with an unsubstituted
tification of their anticonvulsant activity and neurotoxicity in phenyl was less than that of those with a substituted phenyl.
mice. This phase provides an evaluation of the ED50 and Therefore compound 4g with a TD50 value of greater than
TD50 values. The 95% confidence interval, slope of the re- 300 mg·kgꢀ1, ED50 of 23.0 mg·kgꢀ1, and protective index
gression line, and SE of the slope were then calculated. (PIꢁTD50/ED50) of more than 13 was the safest among the
These data are shown in Table 2, which also includes com- compounds synthesized. Compared with the marketed drugs,
parisons with marketed antiepileptic drugs such as pheny- its ED50 value was comparable to that of phenobarbital in the
toion, carbamazepine, phenobarbital, and valproate. Some of MES test but its PI value was higher than that of phenytoin,
these derivatives showed a high degree of protection against carbamazepine, phenobarbital, and valproate. No dose-resis-
MES-induced seizures, although they were less effective tance tendency was seen. With the increase in dose, activity
against scMet-induced seizures.
against both types of seizure improved, although their toxic-
The following structure–activity relationships were ob- ity also became greater.
served. In a series of alkyl substitutions at the first position,
the increase in the carbon number at the first position de-
Acknowledgment This work was supported by the Na-
creased the anticonvulsant activity markedly. The ED50 val- tional Natural Science Foundation of China (No. 30460151).
ues of compounds 4a—c, which were H, CH3 and C3H7 at
the first position, were 17.3, 30.7, and 97.7 mg·kgꢀ1, respec- REFERENCES
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