Synthesis and anticonvulsant activity of novel purine derivatives

Article abstract of DOI:10.1016/j.ejmech.2014.07.074

A series of new purines containing triazole and other heterocycle substituents was synthesized and evaluated for their preliminary anticonvulsant activity and neurotoxicity by using the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) and rotarod neurotoxicity (TOX) tests. Among the compounds studied, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the most potent compound, with a median effective dose of 23.4 mg/kg and a high protective index of more than 25.6 after intraperitoneal administration in mice. Compound 5e showed significant oral activity against MESinduced seizures in mice, with an ED50 of 39.4 mg/kg and a PI above 31.6. These results demonstrate that compound 5e possesses better anticonvulsant activity and is safer than the commercially available drugs carbamazepine and valproate in MES, scPTZ and TOX models.

Full text of DOI:10.1016/j.ejmech.2014.07.074

European Journal of Medicinal Chemistry 84 (2014) 574e583
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and anticonvulsant activity of novel purine derivatives
,
, *
Shi-Ben Wang a, Peng Jin b, Fu-Nan Li c *, Zhe-Shan Quan a
a College of Pharmacy, Yanbian University, No. 977, Park Road, Yanji, Jilin, 133002, China
b Department of Pharmacology, Ischemic/Hypoxic Disease Institute, Seoul National University, College of Medicine, 103 Daehak-ro, Jongno-gu,
Seoul, 110-799, Republic of Korea
c School of Pharmaceutical Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian, 361102, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new purines containing triazole and other heterocycle substituents was synthesized and
evaluated for their preliminary anticonvulsant activity and neurotoxicity by using the maximal elec-
troshock (MES), subcutaneous pentylenetetrazole (scPTZ) and rotarod neurotoxicity (TOX) tests. Among
the compounds studied, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the most potent com-
pound, with a median effective dose of 23.4 mg/kg and a high protective index of more than 25.6 after
intraperitoneal administration in mice. Compound 5e showed significant oral activity against MES-
induced seizures in mice, with an ED50 of 39.4 mg/kg and a PI above 31.6. These results demonstrate
that compound 5e possesses better anticonvulsant activity and is safer than the commercially available
drugs carbamazepine and valproate in MES, scPTZ and TOX models.
Received 10 January 2014
Received in revised form
19 July 2014
Accepted 21 July 2014
Available online 22 July 2014
Keywords:
Synthesis
Purine
Triazole
© 2014 Published by Elsevier Masson SAS.
Maximal electroshock
Neurotoxicity
Pentylenetetrazole
1. Introduction
synthesis, and these compounds exhibiting a range of biological
properties, including anticonvulsant [8,9], antibacterial [10,11],
Epilepsy is a heterogeneous neurological disorder characterized
by the onset of spontaneous convulsive and non-convulsive sei-
zures. This disorder affects over 50 million people worldwide, and it
is estimated that only 50% of patients are adequately treated for
their symptoms with currently available antiepileptic drugs (AEDs).
Of the remaining patients, approximately 20% are either inade-
quately treated or treated at the expense of severe side effects,
leaving approximately 30% of patients with refractory epilepsy
[1,2]. Conventional antiepileptic agents (phenytoin and carbamaz-
epine) and recent antiepileptic drugs (gabapentin, vigabatrin,
remacemide, and loreclezole) are clinically effective against
different types of seizures. However, many AEDs have serious side
effects [3e7]. Therefore, the continued search for safer and more
effective AEDs is necessary.
antifungal [12], antimalarial [13], anticancer [14e16], and anti-
inflammatory [17] activities.
Previously, we reported the synthesis of several triazole-
containing heterocycles, including triazoloquinolines, triazoloph-
thalazines, triazolobenzothiazines, and triazolobenzooxazepines,
and evaluated their anticonvulsant activity. The majority of these
heterocycles exhibited potent anticonvulsant activity [18e21]
(Fig. 1). Here, a series of 7-alkyl-7H-[1,2,4]triazolo[4,3-g]purine
derivatives (4aeo) was designed to combine both purine and tri-
azole moieties. Based on the anticonvulsant activities of com-
pounds 4aeo, another series of 9-alkyl-6-(1H-1,2,4-triazol-1-yl)-
9H-purine derivatives (5aep) was designed and synthesized
through the ring-opening of compounds 4aeo. For the sake of
having a structureeactivity relationship, the triazole ring in com-
pounds 5aep was replaced by other heterocycles such as imidazole,
methylimidazole, or pyrazole rings to give compounds 6e8 and 9,
and their structures were characterized using IR, 1H NMR, MS, and
13C NMR techniques. The anticonvulsant activity of the titled
compounds was evaluated using the maximal electroshock test in
mice, and their neurotoxicity was evaluated using the rotarod test.
The activity of compound 5e against pentylenetetrazole-induced
seizures was also established.
The purine nucleus is one of the most important and widely
exploited heterocyclic ring for the development of bioactive mol-
ecules. The literature contains many examples of purine derivative
* Corresponding authors.
E-mail addresses: fnlee5@xmu.edu.cn (F.-N. Li), zsquan@ybu.edu.cn (Z.-S. Quan).
http://dx.doi.org/10.1016/j.ejmech.2014.07.074
0223-5234/© 2014 Published by Elsevier Masson SAS.

S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
575
OR
OR
O
RO
S
N
N
N
N
RO
N
N
N
N
N
N
N
N
N
III
I
IV
II
R=-CH2Ph
R=-C7H15
ED50=11.0 (mg/kg)
PI=8.0
R=-CH2Ph (o-F)
ED50=17.0 (mg/kg)
PI=14.3
R=-C7H15
ED50=6.9 (mg/kg)
PI=9.5
ED50=22.8 (mg/kg)
PI=12.0
R
N
R
N
N
N
N
N
N
N
N
N
R
R
N
N
N
N
N
N
Ring opening
Bioisosterism
6a-b
7a-b
N
N
N
N
R
N
R
N
N
N
N
N
N
N
N
N
N
N
N
N
4a-o
5a-p
N
S
N
HN
N
8a-b
9a-b
Fig. 1. Structures of some compounds containing triazole and target compounds.
2. Results and discussion
described pharmacological evaluation was accepted by Ethics
Commission of China. Primary studies of anticonvulsants in mice
involved two tests: MES and neurotoxicity tests. The most prom-
ising derivatives were subjected to quantitative determination of
their ED50 and TD50. Experiments were performed in KunMing
mice (weighing 18e22 g) purchased from the Laboratory of Animal
Research, College of Pharmacy, Yanbian University, Yanji, Jilin
Province, China. The animals had free access to food and water,
except during the testing period. The test compounds were dis-
solved in DMSO.
The MES seizure model was used for preliminary screening of
purine derivatives. All the compounds were administered by
intraperitoneal injection in triplicate at doses of 30 and 100 mg/kg.
The findings were recorded at 0.5 h, and the results are presented in
Table 1 and Table 2 (phase I).
The MES test showed that some derivatives of the series 4aeo
were active at a dose of 100 mg/kg (Table 1), indicating their ability
to prevent the seizer spread. Four derivatives (4bee) out of the six
alkyltriazolopurines (4aef) showed anticonvulsant activity. The
length of the alkyl chain appeared to affect the anticonvulsant ac-
tivity of the alkyl-substituted derivatives (4aef). We observed a
correlation between the length of the alkyl chain of compounds
(4aef) and the corresponding anticonvulsant activity. An increase
in the length of the alkyl chain gradually increased the anticon-
vulsant activity, with the maximum anticonvulsant activity being
shown by compound 4c (R ¼ C6H13), after which a gradual decrease
in activity was observed. In this study, the activity curve of the alkyl
chain substituted derivatives was bell-shaped with a maximum
activity peak. Compound 4c showed the maximum activity peak,
which may reflect the optimal partition coefficient associated with
the easiest crossing of biological membranes. Among the benzyl
group-substituted derivatives (4geo), compounds 4g, 4j and 4o
2.1. Chemistry
6-Chloro-9-alkyl-9H-purines (2aep) were prepared by alky-
lating 6-chloro-9H-purine (1) using alkyl bromide or benzyl
chloride derivatives (Scheme 1) [22]. Treatment of 2aep with hy-
drazine hydrate in methanol afforded 1-(9-alkyl-9H-purin-6-yl)
hydrazines (3aeo) in a high yield [23]. Cyclization of compounds
3aeo with triethyl orthoformate yielded 7-alkyl-7H-[1,2,4]triazolo
[4,3-g]purines (4aeo). When 6-chloro-9-alkyl-9H-purines (2aep)
were allowed to react with different azoles such as triazole,
imidazole, methylimidazole and pyrazole in refluxing dime-
thylformamide (DMF) in the presence of K2CO3 [24,25], the 9-
chlorine atom of 2 was easily substituted by these heterocylces,
producing the corresponding purines: 9-alkyl-6-(1H-1,2,4-triazol-
1-yl)-9H-purine (5aep), 9-alkyl-6-(1H-imidazol-1-yl)-9H-purine
(6aeb), 9-alkyl-6-(4-methyl-1H-imidazol-1-yl)-9H-purine (7aeb),
and 9-alkyl-6-(1H-pyrazol-1-yl)-9H-purine (8aeb). 9-Alkyl-6-(3H-
1,2,4-triazol-3-ylthio)-9H-purines (9aeb) were synthesized by
reacting compounds 2aep with 1H (2H), (4H)-1,2,4-triazole-3-
thiol in acetonitrile in the presence of sodium methylate. The
structures of the targeted compounds were characterized using
spectral methods, and all spectral data corroborated the assumed
structures.
2.2. Pharmacology
The obtained compounds were submitted for in vivo evaluation
using the methods described in the Antiepileptic Drug Develop-
ment Program (ADD) of the National Institutes of Health according
to previously described testing procedures (USA) [26,27]. The

576
S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
R
N
N
R
N
N
R
N
N
N
N
N
S
N
N
N
N
N
N
N
9a-b
N
N
N
H
8a-b
4a-o
g
h
c
R
N
R
N
H
N
N
N
b
N
a
N
N
N
N
N
N
Cl
2a-p
Cl
NHNH2
6-Chloro-9H-purine
3a-n
f
d
e
R
R
N
R
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
7a-b
5a-p
N
6a-b
N
(a) K2CO3, RX, DMF, rt, 24h; (b) NH2NH2.H2O, CH3OH, reflux, 1h; (c) HC(OC2H5)3, reflux, 6h; (d) K2CO3,
1,2,4-triazole, DMF, reflux, 3h; (e) K2CO3, imidazole, DMF, reflux, 6h; (f) K2CO3, 4-methylimidazole, DMF,
reflux, 10h; (g) K2CO3, pyrazole, DMF, reflux, 6h; (h) 1H (2H),(4H)-1,2,4-triazole-3-thiol, CH3ONa, acetonitrile, rt,
18h. R: 4a -C4H9, 4b -C5H11, 4c -C6H13, 4d -C7H15, 4e -C8H17, 4f -C10H21, 4g -CH2C6H5 (o-Cl), 4h -CH2C6H5
(m-Cl), 4i -CH2C6H5 (p-Cl), 4j -CH2C6H5 (o-F), 4k -CH2C6H5 (m-F), 4l -CH2C6H5 (p-F), 4m -CH2C6H5 (p-CH3),
4n -CH2C6H5 (p-OCH3), 4o -CH2C6H5; 5a -C5H11, 5b -C6H13, 5c -C7H15, 5d -C8H17, 5e -C10H21, 5f -C12H25, 5g
-C14H29, 5h -CH2C6H5 (o-Cl), 5i -CH2C6H5 (m-Cl), 5j -CH2C6H5 (p-Cl), 5k -CH2C6H5 (o-F), 5l -CH2C6H5 (m-F),
5m -CH2C6H5 (p-F), 5n -CH2C6H5 (p-CH3), 5o -CH2C6H5 (p-OCH3), 5p -CH2C6H5, 6a -C10H21, 6b -CH2C6H5 (o-F),
7a -C10H21, 7b -CH2C6H5 (o-F), 8a -C10H21, 8b -CH2C6H5 (o-F), 9a -C10H21, 9b -CH2C6H5 (o-F)
Scheme 1. Synthetic route of target compounds.
protected against MES-induced seizures to varying degrees at the
dose of 100 mg/kg.
anticonvulsant activity increased. From 5e to 5g, as the alkyl chain
length increased, anticonvulsant activity decreased. Thus, the ac-
tivity curve of the alkyl chain-substituted derivatives was bell-
shaped, displaying a maximum activity peak. Compound 5e
demonstrated the maximum activity peak, which may reflect the
optimal partition coefficient associated with the easiest crossing of
the biological membranes. In the benzyl-substituted derivatives
5hep, variation in the substituents on the phenyl group affected
activity. The activity of derivatives with different halogen substi-
tution on the benzene ring was in the following order: m-Cl > o-
Cl > p-Cl, o-F > m-F > p-F. p-CH3 and p-OCH3 showed low activity
owing to their electron-donating moieties. An electron-
withdrawing group was a more profitable structural feature than
an electron-donating group.
Among all the compounds tested, compounds 4c and 4g
exhibited the most potent anticonvulsant activity against MES-
induced seizures, and these compounds were subjected to phase
II trials to quantify their preliminary anticonvulsant activity (indi-
cated by ED50) and neurotoxicity (indicated by TD50) in mice
(Table 3).
Most of the compounds in series 5aep were active in the MES
test, indicating that they can prevent seizure spread. Four com-
pounds, 5cee and 5k, protected against MES-induced seizures at a
dose of 30 mg/kg. At 100 mg/kg, most compounds showed pro-
tection, except 5g, 5j, and 5meo. Compounds 5bee, 5i, 5kel, and
5p showed protective effects at 100 mg/kg in all 3 mice tested.
Analysis of the activities of the synthesized compounds (5aep)
showed the following results. In the series of compounds 5aeg, the
length of the alkyl chain influenced the anticonvulsant activity of
the derivatives. From 5a to 5e, as the alkyl chain length increased,
Compounds 6, 7, 8, and 9 were designed and synthesized using
the bioisosterism strategy, replacing the triazole ring of compounds
5e and 5k with other heterocycles (i.e., imidazole, methylimidazole,
and pyrazole), and their preliminary anticonvulsant activities were

S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
577
Table 1
Table 2
Anticonvulsant activities of compounds (4aeo) and (5aep) in MES tests.
Anticonvulsant activities of compounds 6, 7, 8 and 9 in MES tests.
R
R
N
R
N
R
N
R
N
R
N
N
N
N
N
N
N
N
S
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
5a-p
N
N
HN
4a-o
N
6a-b
8a-b
9a-b
7a-b
Compound
R
MES (mg/kg)a
100
30
Compound
R
MES (mg/kg)
100
4a
4b
4c
4d
4e
4f
4g
4h
4i
eC4H9
eC5H11
eC6H13
eC7H15
eC8H17
eC10H21
eCH2C6H5 (o-Cl)
eCH2C6H5 (m-Cl)
eCH2C6H5 (p-Cl)
eCH2C6H5 (o-F)
eCH2C6H5 (m-F)
eCH2C6H5 (p-F)
eCH2C6H5 (p-CH3)
eCH2C6H5 (p-OCH3)
eCH2C6H5
eC5H11
eC6H13
eC7H15
eC8H17
0/3b
1/3
3/3
2/3
2/3
0/3
3/3
0/3
0/3
1/3
0/3
0/3
0/3
0/3
1/3
1/3
3/3
3/3
3/3
3/3
1/3
0/3
2/3
3/3
0/3
3/3
3/3
0/3
0/3
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
1/3
2/3
2/3
0/3
0/3
0/3
0/3
0/3
1/3
0/3
0/3
0/3
0/3
0/3
30
6a
6b
7a
7b
8a
8b
9a
9b
eC10H21
eCH2C6H5 (o-F)
eC10H21
eCH2C6H5 (o-F)
eC10H21
eCH2C6H5 (o-F)
eC10H21
1/3
3/3
3/3
0/3
3/3
1/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
eCH2C6H5 (o-F)
4j
4k
4l
4m
4n
4o
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
a PI of 6.4 under the same conditions. Compound 5e was safer than
the anticonvulsant drug carbamazepine. Compounds 5d and 5iel
also showed higher PI values than those shown by the marketed
anticonvulsant drugs in MES and TOX models.
To determine the oral time of peak effect (TPE) of compound 5e,
we conducted a time-course test; compound 5e reached the TPE at
1.5 h after administering oral medications (Fig 2). Next, we evalu-
ated the oral anticonvulsant activity of compound 5e against MES-
induced seizures and neurotoxicity in mice (Table 4), using carba-
mazepine as a reference. 9-Decyl-6-(1H-1,2,4-triazol-1-yl)-9H-pu-
eC10H21
eC12H25
eC14H29
eCH2C6H5 (o-Cl)
eCH2C6H5 (m-Cl)
eCH2C6H5 (p-Cl)
eCH2C6H5 (o-F)
eCH2C6H5 (m-F)
eCH2C6H5 (p-F)
eCH2C6H5 (p-CH3)
eCH2C6H5 (p-OCH3)
eCH2C6H5
rine (5e) showed an ED50 value of 39.4 mg/kg and a
TD50 > 1500 mg/kg, resulting in a PI > 38.1. The standard, carba-
mazepine, showed an ED50 value of 27.3 mg/kg and a TD50 value of
328.6 mg/kg, resulting in a PI of 12.0 under the same conditions.
Thus, compound 5e was safer than the anticonvulsant drug car-
bamazepine in MES and TOX models.
5m
5n
5o
5p
a
Maximal electroshock: doses of 30 and 100 mg/kg were administrated intra-
peritoneally in mice. The animals were examined 0.5 h after administration.
b
n1/n2: the animals protected/the animals tested.
Table 3
also evaluated. As shown in Table 2, compounds 6a and 6b (with
imidazole substitution) protected against MES-induced seizures at
100 mg/kg, but not at 30 mg/kg. Among compounds 7aeb, only
compound 7a showed anti-MES-induced seizure activity at
100 mg/kg, and none of the compounds showed protection at the
30 mg/kg dose. Compounds 8a and 8b, which contain pyrazole,
showed protective effects in 3/3 and 1/3 mice, respectively, at the
dose of 100 mg/kg in the MES tests. Introducing a sulfur atom be-
tween the purine and triazole resulted in compounds 9aeb, but
neither strategy yielded a compound that was protective at a dose
of 100 mg/kg.
As a result of preliminary screening (Tables 1 and 2), thirteen
compounds were subjected to phase II trials to quantify their pre-
liminary anticonvulsant activity and neurotoxicity in mice. We
compared the results of our compounds with the marketed anti-
convulsant drugs, carbamazepine and valproate. As shown in
Table 3, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the
most active and promising compound in this study, with an ED50 of
23.4 mg/kg and a TD50 value of more than 700 mg/kg, resulting in a
PI value higher than 25.6. The standard, carbamazepine, showed an
ED50 value of 11.8 mg/kg and a TD50 value of 76.1 mg/kg, resulting in
Quantitative anticonvulsant data in mice (i.p.).
Compound
ED50 (MES)a
TD50 (NT)b
PIc
4c
4g
5b
5c
5d
5e
5i
5k
5l
5p
6b
7a
51.2 (44.1e59.5)d
51.9 (44.6e60.2)
43.9 (37.8e51.0)
31.5 (23.5e42.2)
33.2 (24.8e44.5)
23.4 (17.0e32.2)
65.4 (56.3e75.9)
29.9 (25.8e34.8)
45.9 (39.5e53.3)
66.6 (57.3e77.4)
61.4 (52.9e71.3)
67.5 (58.1e78.4)
66.5 (57.3e77.3)
11.8 (8.5e16.4)
272 (247e338)
102.5 (88.2e119.0)
314.6 (234.9e421.5)
209.8 (156.6e281.0)
104.9 (78.3e140.5)
247.4 (184.7e331.5)
>700
487.7 (419.9e566.5)
448.9 (386.5e521.4)
384.3 (330.8e446.3)
314.6 (234.9e421.5)
115.4 (86.1e154.6)
196.1 (146.4e262.7)
241.2 (180.1e241.2)
76.1 (55.8e103.7)
426 (369e450)
2.0
6.1
4.8
3.3
7.4
>25.6
7.5
15.0
8.3
4.7
1.8
2.9
3.6
6.4
1.6
8a
Carbamazepine
Valproate
a
ED50: median effective dose affording anticonvulsant protection in 50% of ani-
mals, the dose is measured in mg/kg.
b
TD50: median toxic dose eliciting minimal neurological toxicity in 50% of ani-
mals, the dose is measured in mg/kg.
c
PI: protective index (TD50/ED50).
95% confidence intervals given in parentheses.
d

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S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
modified compounds also showed higher neurotoxicity, which led
them to have a lower PI compared to those of compounds 5aep.
When we introduced a sulfur atom in triazole (1H (2H), (4H)-1,2,4-
triazole-3-thiol), compounds (9aeb) showed almost no anticon-
vulsant activity compared to that shown by compounds containing
the triazole ring. These data indicate that separating the triazole
from the purine, instead of incorporating the triazole into the pu-
rine, displayed the best anticonvulsant activity and most favorable
PI. Therefore, the isolated triazole ring may be one of the active
centers.
3. Conclusion
Based on our previous work, we designed and synthesized
several series of purine derivatives and evaluated their preliminary
anticonvulsant activities using the maximal electroshock, subcu-
taneous pentylenetetrazole and rotarod tests. Among these com-
pounds, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the
most potent, with an ED50 value of 23.4 mg/kg and a PI value above
25.6. Compound 5e possessed better anticonvulsant activity and
higher safety than the marketed drugs, carbamazepine and val-
proate, as well as previously reported triazole derivatives (I, II, III,
and IV) in MES, sc-PTZ and TOX models. In addition, Compound 5e
exhibited an ED50 value of 39.4 mg/kg and PI > 31.6 by oral
administration, indicating that it possesses better anticonvulsant
activity and higher safety than carbamazepine in MES and TOX
models.
Fig. 2. Time-course of compound 5e (50 mg/kg) in the MES test (p.o.).
Table 4
Pharmacological evaluation of compound 5e and carbamazepine administered
orally to mice.
Compound
ED50 (MES)
TD50 (NT)
PI
5e
39.4 (34.0e45.6)
27.3 (19.7e37.9)
>1500
328.6 (229.9e469.7)
>38.1
Carbamazepine
12.0
To further investigate the preliminary anticonvulsant activity of
compound 5e in a chemical model, convulsions were induced using
PTZ. Compound 5e was administered to mice at 50 mg/kg, a dose
higher than its ED50 value and far below its TD50 value. The refer-
ence drug, carbamazepine, was also administered at 50 mg/kg. In
the sc-PTZ model, carbamazepine inhibited clonic seizures, tonic
seizures, and death by 0, 100, and 80%, respectively. Compound 5e
inhibited clonic seizures, tonic seizures, and death by 20, 90, and
70%, respectively (Fig 3). Thus, compound 5e and carbamazepine
can protect the mice from tonic seizures and death in the sc-PTZ
model.
In this study, we prepared six series of compounds and evalu-
ated their preliminary anticonvulsant activities, and we established
the following SARs.
When the triazole ring of compounds 4aeo and 5aep was
opened, their anticonvulsant activities were stronger and the PIs
were higher for 5aep compared to 4aeo. When the triazole ring in
compounds 5aep was replaced with other heterocycles (i.e.,
imidazole, methylimidazole, and pyrazole), the resultant com-
pounds, (6aeb), (7aeb), and (8aeb), had slightly decreased activity
compared with the compounds containing the triazole ring. These
4. Experimental
4.1. Chemistry
Melting points were determined in open capillary tubes and
were uncorrected. IR spectra were recorded (in KBr) on an
IRPrestige-21 (PerkineElmer, Waltham, MA, USA). 1H NMR and 13
C
NMR spectra were measured on an AV-300 spectrometer (Bruker,
Switzerland), with all chemical shifts given in ppm relative to tet-
ramethylsilane. Mass spectra were measured on an HP1100LC
(Agilent Technologies, USA). The purity of all the synthesized
compounds was checked by a thin-layer chromatography per-
formed on Merck Silica gel GF254 aluminum plates, using the
following systems: A. dichloromethane/methanol (40:1), B. ethyl
acetate. High resolution mass spectra were measured on an MALDI-
TOF/TOF mass spectrometer (Bruker Daltonik, Germany). The major
chemicals were purchased from Aldrich Chemical Corporation.
4.1.1. General procedure for the synthesis of 7-alkyl-7H-[1,2,4]
triazolo[4,3-g]purine (4aeo)
In a round-bottomed flask, compound (3aeo) (5.3 mmol) was
dissolved in triethoxymethane (20 ml), the solution was refluxed
for 12 h, and the solvent was removed under reduced pressure. The
residue was purified by silica gel chromatography using (CH2Cl2
:
CH3OH ¼ 60 : 1). The yield, melting point, and spectral data for each
compound are shown below.
4.1.1.1. 7-Butyl-7H-[1,2,4]triazolo[4,3-g]purine (4a). Yield: 57%, mp:
176e177 ꢀC, Rf ¼ 0.15A, Rf ¼ 0.17B, Chemical formula: C10H12N6. 1H
NMR (DMSO-d6, 300 MHz)
d
: 0.83 (t, 3H, J ¼ 7.53 Hz, eCH3),
1.19e1.85 (m, 4H, eCH2e), 4.31 (q, 2H, J ¼ 6.90 Hz, eCH2e), 8.40 (s,
1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-
H). 13C NMR (DMSO-d6, 75 MHz)
d: 14.40, 22.55, 26.36, 44.36,
120.29, 136.04, 136.50, 139.74, 142.35, 144.85. IR (KBr) cmꢁ1: 1641
1384. MS-EI m/z 217 (M þ 1). ESI-HRMS calcd for C10H12N6þ
([M þ H]þ): 217.1196; found: 217.1202.
Fig. 3. Effects of compound 5e on sc-PTZ-induced seizure in mice (i.p.).

S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
579
4.1.1.2. 7-Pentyl-7H-[1,2,4]triazolo[4,3-g]purine (4b). Yield: 49%,
mp: 198e200 ꢀC, Rf ¼ 0.14A, Rf ¼ 0.16B, Chemical formula:
1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
75 MHz) d: 46.95, 120.49, 126.67, 127.87, 128.38, 131.12, 133.75,
C
11H14N6. 1H NMR (DMSO-d6, 300 MHz)
d
: 0.82 (t, 3H, J ¼ 6.75 Hz,
136.62, 136.62, 139.45, 139.60, 142.40, 144.78. IR (KBr) cmꢁ1: 1645
1387. MS-EI m/z 285 (M þ 1). ESI-HRMS calcd for C13H9ClN6þ
([M þ H]þ): 285.0650; found: 285.0639.
eCH3), 1.25e1.85 (m, 6H, eCH2e), 4.30 (q, 2H, J ¼ 6.60 Hz, eCH2e),
8.41 (s, 1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.41 (s, 1H,
Pyrimidine-H). 13C NMR (DMSO-d6, 75 MHz)
d: 14.22, 22.01, 28.53,
29.81, 44.33, 120.26, 136.07, 136.52, 139.73, 142.34, 144.85. IR (KBr)
4.1.1.9. 7-(4-Chlorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4i).
cmꢁ1: 1643 1381. MS-EI m/z 231 (M þ 1). ESI-HRMS calcd for
Yield: 64%, mp: 198e200 ꢀC, Rf ¼ 0.13A, Rf ¼ 0.16B, Chemical
C
11H14Nþ6 ([M þ H]þ): 231.1353; found: 231.1361.
formula: C13H9ClN6. 1H NMR (DMSO-d6, 300 MHz)
d: 5.57 (s, 2H,
eCH2e), 7.34e7.41 (dd, 4H, Ar-H), 8.55 (s, 1H, Triazole-H), 9.33 (s,
4.1.1.3. 7-Hexyl-7H-[1,2,4]triazolo[4,3-g]purine (4c). Yield: 63%, mp:
195e196 ꢀC, Rf ¼ 0.16A, Rf ¼ 0.21B, Chemical formula: C12H16N6. 1H
1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
75 MHz) d: 46.92, 120.48, 129.17, 129.17, 129.90, 129.90, 133.05,
NMR (DMSO-d6, 300 MHz)
d
: 0.81 (t, 3H, J ¼ 6.75 Hz, eCH3),
136.05, 136.53, 136.61, 139.60, 142.38, 144.77. IR (KBr) cmꢁ1: 1641
1384. MS-EI m/z 285 (M þ 1). ESI-HRMS calcd for C13H9ClN6þ
([M þ H]þ): 285.0650; found: 285.0641.
1.24e1.84 (m, 8H, eCH2e), 4.30 (q, 2H, J ¼ 7.50 Hz, eCH2e), 8.42 (s,
1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.42 (s, 1H, Pyrimidine-
H). 13C NMR (DMSO-d6, 75 MHz)
d: 14.26, 22.37, 26.03, 30.07,
31.06, 44.35, 120.26, 136.06, 136.51, 139.73, 142.34, 144.85. IR (KBr)
4.1.1.10. 7-(2-Fluorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4j).
cmꢁ1: 1642 1384. MS-EI m/z 245 (M þ 1). ESI-HRMS calcd for
Yield: 53%, mp: 248e250 ꢀC, Rf ¼ 0.14A, Rf ¼ 0.15B, Chemical
C
12H16Nþ6 ([M þ H]þ): 245.1509; found: 245.1516.
formula: C13H9FN6. 1H NMR (DMSO-d6, 300 MHz)
d: 5.63 (s, 2H,
eCH2e), 7.15e7.39 (m, 4H, Ar-H), 8.50 (s, 1H, Triazole-H), 9.32 (s,
4.1.1.4. 7-Heptyl-7H-[1,2,4]triazolo[4,3-g]purine (4d). Yield: 67%,
mp: 188e189 ꢀC, Rf ¼ 0.15A, Rf ¼ 0.17B, Chemical formula:
1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
75 MHz) d: 41.85, 115.88, 116.15, 120.36, 123.72, 125.28 (d, Jc-
C
13H18N6. 1H NMR (DMSO-d6, 300 MHz)
d
: 0.80 (t, 3H, J ¼ 6.00 Hz,
¼ 3.75 Hz), 130.40 (d, Jc-f ¼ 3.75 Hz), 130.86 (d, Jc-f ¼ 8.25 Hz),
f
eCH3), 1.19e1.84 (m, 10H, eCH2e), 4.30 (q, 2H, J ¼ 7.50 Hz, eCH2e),
136.63 (d, Jc-f ¼ 6.75 Hz), 139.68, 142.57, 144.75, 161.99 (d, Jc-
8.41 (s, 1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.42 (s, 1H,
¼ 244.5 Hz). IR (KBr) cmꢁ1: 1641 1386. MS-EI m/z 269 (M þ 1).
f
Pyrimidine-H). 13C NMR (DMSO-d6, 75 MHz)
d
: 14.32, 22.41, 26.33,
ESI-HRMS calcd for C13H9FNþ6 ([M þ H]þ): 269.0945; found:
28.53, 30.12, 31.53, 44.35, 120.27, 136.05, 136.51, 139.72, 142.34,
144.85. IR (KBr) cmꢁ1: 16411384. MS-EI m/z 259 (M þ 1). ESI-HRMS
calcd for C13H18Nþ6 ([M þ H]þ): 259.1666; found: 259.1675.
269.0937.
4.1.1.11. 7-(3-Fluorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4k).
Yield: 43%, mp: 234e235 ꢀC, Rf ¼ 0.14A, Rf ¼ 0.16B, Chemical for-
4.1.1.5. 7-Octyl-7H-[1,2,4]triazolo[4,3-g]purine (4e). Yield: 57%, mp:
189e191 ꢀC, Rf ¼ 0.20A, Rf ¼ 0.19B, Chemical formula: C14H20N6. 1H
mula: C13H9FN6. 1H NMR (DMSO-d6, 300 MHz)
d: 5.59 (s, 2H,
eCH2e), 7.14e7.40 (m, 4H, Ar-H), 8.56 (s, 1H, Triazole-H), 9.33 (s,
NMR (DMSO-d6, 300 MHz)
d
: 0.81 (t, 3H, J ¼ 6.00 Hz, eCH3),
1H, Imidazole-H), 9.42 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
1.19e1.85 (m, 12H, eCH2e), 4.30 (q, 2H, J ¼ 6.60 Hz, eCH2e), 8.41 (s,
75 MHz)
d
: 47.02, 115.00 (d, Jc-f ¼ 21.7 Hz), 115.39 (d, Jc-f ¼ 21.0 Hz),
1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-
120.48, 123.97, 124.01, 131.35 (d, Jc-f ¼ 8.25 Hz), 136.63, 139.64,
139.86 (d, Jc-f ¼ 7.5 Hz), 142.42, 144.79, 164.26 (d, Jc-f ¼ 243.0 Hz). IR
(KBr) cmꢁ1: 1641 1386. MS-EI m/z 269 (M þ 1). ESI-HRMS calcd for
H). 13C NMR (DMSO-d6, 75 MHz)
d: 14.35, 22.48, 26.36, 28.82,
28.96, 30.09, 31.59, 44.35. 120.27, 136.05, 136.51, 139.73, 142.35,
144.85. IR (KBr) cmꢁ1: 1644 1388. MS-EI m/z 273 (M þ 1). ESI-HRMS
calcd for C14H20Nþ6 ([M þ H]þ): 273.1822; found: 273.1829.
C
13H9FNþ6 ([M þ H]þ): 269.0945; found: 269.0941.
4.1.1.12. 7-(4-Fluorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4l).
4.1.1.6. 7-Decyl-7H-[1,2,4]triazolo[4,3-g]purine (4f). Yield: 57%, mp:
184e185 ꢀC, Rf ¼ 0.21A, Rf ¼ 0.22B, Chemical formula: C16H24N6. 1H
Yield: 47%, mp: 218e220 ꢀC, Rf ¼ 0.15A, Rf ¼ 0.17B, Chemical
formula: C13H9FN6. 1H NMR (DMSO-d6, 300 MHz)
d: 5.56 (s, 2H,
NMR (DMSO-d6, 300 MHz)
d
: 0.82 (t, 3H, J ¼ 6.00 Hz, eCH3),
eCH2e), 7.15e7.45 (dd, 4H, Ar-H), 8.55 (s, 1H, Triazole-H), 9.33 (s,
1.19e1.85 (m, 16H, eCH2e), 4.31 (q, 2H, J ¼ 5.85 Hz, eCH2e), 8.42 (s,
1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
1H, Triazole-H), 9.33 (s, 1H, Imidazole-H), 9.42 (s, 1H, Pyrimidine-
75 MHz)
d
: 46.90, 115.89, 116.17, 120.47, 130.35 (d, Jc-f ¼ 9.0 Hz),
H). 13C NMR (DMSO-d6, 75 MHz)
d
: 14.38, 22.52, 26.34, 28.84,
133.33 (d, Jc-f ¼ 3.0 Hz), 136.51, 136.61, 139.58, 142.31, 144.78,
163.80 (d, Jc-f ¼ 242.2 Hz). IR (KBr) cmꢁ1: 1641 1386. MS-EI m/z
269 (M þ 1). ESI-HRMS calcd for C13H9FNþ6 ([M þ H]þ): 269.0945;
found: 269.0932.
29.09, 29.30, 29.30, 30.08, 31.71, 44.36, 120.28, 136.06, 136.50,
139.74, 142.36, 144.85. IR (KBr) cmꢁ1: 1641 1384. MS-EI m/z 301
(M þ 1). ESI-HRMS calcd for C16H24Nþ6 ([M þ H]þ): 301.2135; found:
301.2146.
4.1.1.13. 7-(4-Methylbenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4m).
4.1.1.7. 7-(2-Chlorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4g).
Yield: 51%, mp: 192e193 ꢀC, Rf ¼ 0.16A, Rf ¼ 0.18B, Chemical for-
Yield: 55%, mp: 222e224 ꢀC, Rf ¼ 0.13A, Rf ¼ 0.17B, Chemical for-
mula: C14H12N6. 1H NMR (DMSO-d6, 300 MHz)
d: 2.24 (s, 3H, eCH3),
mula: C13H9ClN6. 1H NMR (DMSO-d6, 300 MHz)
d
: 5.66 (s, 2H,
5.50 (s, 2H, eCH2e), 7.12e7.25 (dd, 4H, Ar-H), 8.53 (s, 1H, Triazole-
eCH2e), 7.02e7.54 (m, 4H, Ar-H), 8.47 (s, 1H, Triazole-H), 9.31 (s,
H), 9.32 (s, 1H, Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR
(DMSO-d6, 75 MHz) d: 21.10, 47.40, 120.39, 127.99, 127.99, 129.71,
1H, Imidazole-H), 9.42 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
75 MHz)
d
: 45.62, 120.41, 128.15, 129.65, 130.01, 130.28, 132.40,
129.71, 134.06, 136.40, 136.58, 137.68, 139.61, 142.33, 144.79. IR
134.13, 136.57, 136.64, 139.81, 142.72, 144.78. IR (KBr) cmꢁ1: 1641
1384. MS-EI m/z 285 (M þ 1). ESI-HRMS calcd for C13H9ClN6þ
([M þ H]þ): 285.0650; found: 285.0642.
(KBr) cmꢁ1: 1641 1388. MS-EI m/z 265 (M þ 1). ESI-HRMS calcd for
C
14H12Nþ6 ([M þ H]þ): 265.1196; found: 265.1183.
4.1.1.14. 7-(4-Methoxybenzyl)-7H-[1,2,4]triazolo[4,3-g]purine (4n).
Yield: 57%, mp: 201e203 ꢀC, Rf ¼ 0.14A, Rf ¼ 0.16B, Chemical for-
4.1.1.8. 7-(3-Chlorobenzyl)-7H-[1,2,4]triazolo[4,3-g]purine
(4h).
Yield: 46%, mp: 280e282 ꢀC, Rf ¼ 0.14A, Rf ¼ 0.18B, Chemical for-
mula: C14H12N6O. 1H NMR (DMSO-d6, 300 MHz)
d: 3.71 (s, 3H,
mula: C13H9ClN6. 1H NMR (DMSO-d6, 300 MHz)
d
: 5.58 (s, 2H,
eOCH3), 5.48 (s, 2H, eCH2e), 6.88e7.35 (dd, 4H, Ar-H), 8.52 (s, 1H,
eCH2e), 7.29e7.44 (m, 4H, Ar-H), 8.55 (s, 1H, Triazole-H), 9.33 (s,
Triazole-H), 9.33 (s,1H, Imidazole-H), 9.41 (s,1H, Pyrimidine-H). 13
C

580
S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
NMR (DMSO-d6, 75 MHz)
d
: 47.15, 55.55, 114.54, 114.54, 120.40,
1577. MS-EI m/z 300 (M þ 1). ESI-HRMS calcd for C15H21N7þ
([M þ H]þ): 300.1931; found: 300.1939.
129.00, 129.64, 129.64, 136.38, 136.58, 139.55, 142.21, 144.78,159.41.
IR (KBr) cmꢁ1: 1641 1384. MS-EI m/z 281 (M þ 1). ESI-HRMS calcd
for C14H12N6Oþ ([M þ H]þ): 281.1145; found: 281.1137.
4.1.2.5. 9-Decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5e). Yield:
55%, mp: 78e79 ꢀC, Rf ¼ 0.40A, Rf ¼ 0.47B. Chemical formula:
C
17H25N7. 1H NMR (CDCl3, 300 MHz)
d: 0.87 (t, 3H, J ¼ 6.64 Hz,
4.1.1.15. 7-Benzyl-7H-[1,2,4]triazolo[4,3-g]purine (4o). Yield: 47%,
mp: 212e213 ꢀC, Rf ¼ 0.15A, Rf ¼ 0.17B, Chemical formula:
eCH3), 1.25e1.99 (m, 16H, eCH2e), 4.36 (t, 2H, J ¼ 7.23 Hz, eCH2e),
8.21 (s, 1H, Triazole-H), 8.31 (s, 1H, Triazole-H), 8.90 (s, 1H,
Imidazole-H), 9.71 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
C
13H10N6O. 1H NMR (DMSO-d6, 300 MHz)
d: 5.56 (s, 2H, eCH2e),
7.28e7.34 (m, 5H, Ar-H), 8.54 (s, 1H, Triazole-H), 9.33 (s, 1H,
Imidazole-H), 9.41 (s, 1H, Pyrimidine-H). 13C NMR (DMSO-d6,
d
: 14.10, 22.64, 26.61, 28.96, 29.22, 29.37, 29.42, 29.88, 31.82, 44.46,
122.33, 145.02, 145.21, 145.72, 152.04, 154.02, 154.43. IR (KBr) cmꢁ1
:
75 MHz) d: 47.60, 120.43, 127.93, 127.93, 128.37, 129.20, 129.20,
136.46, 136.60, 137.07, 139.67, 142.41, 144.81. IR (KBr) cmꢁ1: 1642
1387. MS-EI m/z 251 (M þ 1). ESI-HRMS calcd for C13H10N6þ
([M þ H]þ): 251.1040; found: 251.1029.
1604 1577. MS-EI m/z 328 (M þ 1). ESI-HRMS calcd for C17H25N7þ
([M þ H]þ): 328.2244; found: 328.2232.
4.1.2.6. 9-Dodecyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5f). Yield:
4.1.2. General procedure for the synthesis of 9-alkyl-6-(1H-1,2,4-
triazol-1-yl)-9H-purine (5aep)
72%, mp: 67e68 ꢀC, Rf ¼ 0.39A, Rf ¼ 0.46B, Chemical formula:
C
19H29N7. 1H NMR (CDCl3, 300 MHz)
d
: 0.88 (t, 3H, J ¼ 6.61 Hz, eCH3),
A solution of 2aep (2 mmol), 1H-1,2,4-triazole (2.2 mmol), and
K2CO3 (2.2 mmol) in N,N-dimethylformamide (30 ml) was refluxed
for 3 h. After evaporating 2/3 volume of the solution, the residue
was poured into ice water. The precipitate was filtered and washed
with water to produce a white solid. All the compounds were
recrystallized in ethanol to produce the pure compound (5aep).
1.25e1.99 (m, 20H, eCH2e), 4.36 (t, 2H, J ¼ 7.23 Hz, eCH2e), 8.21 (s,
1H, Triazole-H), 8.31 (s,1H, Triazole-H), 8.91 (s,1H, Imidazole-H), 9.71
(s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 14.14, 22.70, 26.63,
28.98, 29.35, 29.39, 29.49, 29.58, 29.64, 29.67, 31.92, 44.47, 122.35,
145.04, 145.21, 145.71, 152.05, 154.05, 154.44. IR (KBr) cmꢁ1: 1602
1577. MS-EI m/z 356 (M þ 1). ESI-HRMS calcd for C19H29N7þ
([M þ H]þ): 356.2557; found: 356.2549.
4.1.2.1. 9-Pentyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine(5a). Yield: 64%,
mp: 109e111 ꢀC, Rf ¼ 0.37A, Rf ¼ 0.46B, Chemical formula: C12H15N7.
4.1.2.7. 9-Tetradecyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5g).
1H NMR (CDCl3, 300 MHz)
d
: 0.89 (t, 3H, J ¼ 6.82 Hz, eCH3),
Yield: 63%, mp: 66e67 ꢀC, Rf ¼ 0.38A, Rf ¼ 0.47B, Chemical for-
1.31e2.00 (m, 6H, eCH2), 4.34 (t, 2H, J ¼ 7.23 Hz, eCH2e), 8.20 (s,1H,
mula: C21H33N7. 1H NMR (CDCl3, 300 MHz)
d: 0.87 (t, 3H,
Triazole-H), 8.29 (s,1H, Triazole-H), 8.89 (s,1H, Imidazole-H), 9.70 (s,
J ¼ 6.00 Hz, eCH3), 1.25e1.96 (m, 24H, eCH2e), 4.35 (t, 2H,
J ¼ 7.11 Hz, eCH2e), 8.20 (s, 1H, Triazole-H), 8.30 (s, 1H, Triazole-
H), 8.90 (s, 1H, Imidazole-H), 9.71 (s, 1H, Pyrimidine-H). 13C NMR
1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 13.83, 22.06, 28.67,
29.55, 44.42, 122.30, 145.00, 145.21, 145.70, 152.02, 153.97, 154.40. IR
(KBr) cmꢁ1: 1606 1577. MS-EI m/z 258 (M þ 1). ESI-HRMS calcd for
(CDCl3, 75 MHz) d: 14.12, 22.67, 26.44, 26.61, 28.98, 29.33, 29.37,
C
12H15Nþ7 ([M þ H]þ): 258.1462; found: 258.1455.
29.46, 29.57, 29.62, 29.87, 31.88, 44.46, 49.73, 122.32, 145.01,
145.20, 145.70, 152.03, 154.02, 154.42. IR (KBr) cmꢁ1: 1606 1577.
MS-EI m/z 384 (M þ 1). ESI-HRMS calcd for C21H33Nþ7 ([M þ H]þ):
384.2870; found: 384.2861.
4.1.2.2. 9-Hexyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5b). Yield: 60%,
mp: 76e77 ꢀC, Rf ¼ 0.39A, Rf ¼ 0.45B, Chemical formula: C13H17N7.
1H NMR (CDCl3, 300 MHz)
d
: 0.87 (t, 3H, J ¼ 6.62 Hz, eCH3),
1.29e1.98 (m, 8H, eCH2e), 4.35 (t, 2H, J ¼ 7.24 Hz, eCH2e), 8.21 (s,
4.1.2.8. 9-(2-Chlorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5h).
Yield: 53%, mp: 157e158 ꢀC, Rf ¼ 0.37A, Rf ¼ 0.42B, Chemical for-
1H, Triazole-H), 8.30 (s, 1H, Triazole-H), 8.89 (s, 1H, Imidazole-H),
9.70 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 13.87,
mula: C14H10ClN7. 1H NMR (CDCl3, 300 MHz)
d: 5.65 (s, 2H, eCH2e),
22.38, 26.24, 29.80, 31.08, 44.43, 122.32, 144.99, 145.22, 145.69,
152.01, 153.95, 154.40. IR (KBr) cmꢁ1: 1603 1577. MS-EI m/z 272
(M þ 1). ESI-HRMS calcd for C13H17Nþ7 ([M þ H]þ): 272.1618; found:
272.1609.
7.29e7.49 (m, 4H, Ar-H), 8.29 (s, 1H, Triazole-H), 8.31 (s, 1H,
Triazole-H), 8.94 (s, 1H, Imidazole-H), 9.72 (s, 1H, Pyrimidine-H).
13C NMR (CDCl3, 75 MHz)
d: 45.51, 122.15, 127.63, 130.19, 130.52,
130.71, 132.11, 133.71, 145.12, 145.76, 152.37, 154.05, 154.45. IR (KBr)
cmꢁ1: 1602 1577. MS-EI m/z 312 (M þ 1). ESI-HRMS calcd for
4.1.2.3. 9-Heptyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5c). Yield:
C
14H10ClNþ7 ([M þ H]þ): 312.0759; found: 312.0750.
58%, mp: 52e54 ꢀC, Rf ¼ 0.37A, Rf ¼ 0.45B, Chemical formula:
C
14H19N7. 1H NMR (CDCl3, 300 MHz)
d: 0.85 (t, 3H, J ¼ 6.40 Hz,
4.1.2.9. 9-(3-Chlorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5i).
Yield: 78%, mp: 147e149 ꢀC, Rf ¼ 0.36A, Rf ¼ 0.43B, Chemical for-
eCH3), 1.25e2.94 (m, 10H, eCH2e), 4.34 (t, 2H, J ¼ 7.20 Hz, eCH2e),
8.20 (s, 1H, Triazole-H), 8.28 (s, 1H, Triazole-H), 8.88 (s, 1H,
Imidazole-H), 9.69 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
mula: C14H10ClN7. 1H NMR (CDCl3, 300 MHz)
d: 5.50 (s, 2H, eCH2e),
7.23e7.34 (m, 4H, Ar-H), 8.22 (s, 1H, Triazole-H), 8.31 (s, 1H,
d
: 13.99, 22.47, 26.56, 28.62, 29.87, 31.54, 44.45, 122.31, 144.99,
145.21, 145.72, 152.02, 153.99, 154.41. IR (KBr) cmꢁ1: 1602 1577. MS-
Triazole-H), 8.94 (s, 1H, Imidazole-H), 9.70 (s, 1H, Pyrimidine-H).
13C NMR (CDCl3, 75 MHz)
d: 47.10, 122.18, 125.91, 127.95, 129.13,
EI m/z 286 (M þ 1). ESI-HRMS calcd for C14H19Nþ7 ([M þ H]þ):
286.1775; found: 286.1769. ESI-HRMS calcd for
C
14H19Nþ7
130.60, 135.21, 136.44, 136.56, 145.25, 145.38, 152.52, 154.12.,
154.32. IR (KBr) cmꢁ1: 1602 1577. MS-EI m/z 312 (M þ 1). ESI-HRMS
calcd for C14H10ClNþ7 ([M þ H]þ): 312.0759; found: 312.0747.
([M þ H]þ): 286.1775; found: 286.1766.
4.1.2.4. 9-Octyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5d). Yield:
45%, mp: 77e79 ꢀC, Rf ¼ 0.38A, Rf ¼ 0.48B, Chemical formula:
4.1.2.10. 9-(4-Chlorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
C
15H21N7. 1H NMR (CDCl3, 300 MHz)
d: 0.86 (t, 3H, J ¼ 6.67 Hz,
(5j). Yield: 66%, mp: 185e186 ꢀC, Rf ¼ 0.37A, Rf ¼ 0.41B, Chemical
eCH3), 1.25e1.99 (m, 12H, eCH2e), 4.35 (t, 2H, J ¼ 7.24 Hz, eCH2e),
8.21 (s, 1H, Triazole-H), 8.31 (s, 1H, Triazole-H), 8.90 (s, 1H,
Imidazole-H), 9.71 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
formula: C14H10ClN7. 1H NMR (CDCl3, 300 MHz)
d: 5.50 (s, 2H,
eCH2-), 7.28e7.38 (dd, 4H, Ar-H), 8.20 (s, 1H, Triazole-H), 8.31 (s,
1H, Triazole-H), 8.93 (s, 1H, Imidazole-H), 9.70 (s, 1H, Pyrimidine-
d
: 14.03, 22.54, 26.60, 28.91, 29.02, 29.87, 31.64, 44.44, 122.31,
H). 13C NMR (CDCl3, 75 MHz)
d: 47.11, 122.18, 129.28, 129.28,
144.99, 145.21, 145.72, 152.02, 153.98, 154.40. IR (KBr) cmꢁ1: 1602
129.48, 129.48, 133.09, 134.91, 145.15, 145.26, 145.36, 152.43, 154.08,

S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
581
154.29. IR (KBr) cmꢁ1: 1602 1577. MS-EI m/z 312 (M þ 1). ESI-HRMS
calcd for C14H10ClNþ7 ([M þ H]þ): 312.0759; found: 312.0751.
75 MHz) d: 47.77, 122.20, 127.89,127.89, 128.87, 129.27, 129.27, 134.58,
145.08, 145.28, 145.58, 152.35, 154.00, 154.39. IR (KBr) cmꢁ1: 1602
1577. MS-EI m/z 278 (M þ 1). ESI-HRMS calcd for C14H11N7þ
([M þ H]þ): 278.1149; found: 278.1142.
4.1.2.11. 9-(2-Fluorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5k). Yield: 64%, mp: 168e170 ꢀC, Rf ¼ 0.36A, Rf ¼ 0.40B, Chemical
formula: C14H10FN7. 1H NMR (CDCl3, 300 MHz)
d: 5.57 (s, 2H,
4.1.3. General procedure for the synthesis of 9-alkyl-6-(1H-imidazol-
1-yl)-9H-purine (6aeb)
eCH2e), 7.10e7.43 (m, 4H, Ar-H), 8.28 (s, 1H, Triazole-H), 8.29 (s,
1H, Triazole-H), 8.92 (s, 1H, Imidazole-H), 9.70 (s, 1H, Pyrimidine-
A solution of 6-chloro-9-alkyl-9H-purine (2 mmol), imidazole
(2.2 mmol), and K2CO3 (2.2 mmol) in N, N-dimethylformamide
(30 ml) was refluxed for 6 h. After evaporating 2/3 volume of the
solution, the residue was poured into ice water, and the product
was recrystallized from ethyl acetate with a moderate yield.
H). 13C NMR (CDCl3, 75 MHz)
d
: 41.75, 116.15 (d, Jc-f ¼ 21.0 Hz),
121.76, 121.95 (d, Jc-f ¼ 12.5 Hz), 124.89 (d, Jc-f ¼ 3.7 Hz), 130.83,
131.19 (d, Jc-f ¼ 8.2 Hz), 145.05, 145.30, 145.73, 152.34, 154.00,
154.31, 162.47 (d, Jc-f ¼ 246.0 Hz). IR (KBr) cmꢁ1: 1602 1577. MS-EI
m/z 296 (M þ 1). ESI-HRMS calcd for C14H10FNþ7 ([M þ H]þ):
296.1054; found: 296.1056.
4.1.3.1. 9-Decyl-6-(1H-imidazol-1-yl)-9H-purine (6a). Yield: 56%,
mp: 93e94 ꢀC, Rf ¼ 0.42A, Rf ¼ 0.63B, Chemical formula: C19H26N6.
4.1.2.12. 9-(3-Fluorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
1H NMR (CDCl3, 300 MHz)
d
: 0.88 (t, 3H, J ¼ 6.16 Hz, eCH3),
(5l). Yield: 84%, mp: 149e150 ꢀC, Rf ¼ 0.38A, Rf ¼ 0.42B, Chemical
1.25e1.96 (m, 16H, eCH2e), 4.32 (t, 2H, J ¼ 7.15 Hz, eCH2e),
7.26e7.28 (d, 1H, Imidazole-H), 8.10 (s, 1H, Imidazole-H), 8.41 (d,
1H, Imidazole-H), 8.80 (s, 1H, Imidazole-H), 9.19 (s, 1H, Pyrimidine-
formula: C14H10FN7. 1H NMR (CDCl3, 300 MHz)
d: 5.52 (s, 2H,
eCH2e), 7.03e7.35 (m, 4H, Ar-H), 8.22 (s, 1H, Triazole-H), 8.31 (s,
1H, Triazole-H), 8.94 (s, 1H, Imidazole-H), 9.70 (s, 1H, Pyrimidine-
H). 13C NMR (CDCl3, 75 MHz)
d: 14.09, 22.64, 26.64, 28.98, 29.22,
H). 13C NMR (CDCl3, 75 MHz)
d
: 47.17, 114.79 (d, Jc-f ¼ 21.7 Hz),
29.38, 29.43, 29.92, 31.82, 44.31, 117.33, 122.43, 130.66, 137.62,
144.38, 145.63, 152.10, 153.72. IR (KBr) cmꢁ1: 1602 1579. MS-EI m/z
327 (M þ 1). ESI-HRMS calcd for C19H26Nþ6 ([M þ H]þ): 327.2292;
found: 327.2285.
115.80 (d, Jc-f ¼ 21.0 Hz), 122.18, 123.39 (d, Jc-f ¼ 3.0 Hz), 131.05,
137.03 (d, Jc-f ¼ 6.7 Hz), 145.26, 145.40, 152.49, 154.09, 154.33,
164.68 (d, Jc-f ¼ 246.7 Hz). IR (KBr) cmꢁ1: 1602 1577. MS-EI m/z 296
(M þ 1). ESI-HRMS calcd for C14H10FNþ7 ([M þ H]þ): 296.1054;
found: 296.1044.
4.1.3.2. 9-(2-Fluorobenzyl)-6-(1H-imidazol-1-yl)-9H-purine
(6b).
Yield: 64%, mp: 150e152 ꢀC, Rf ¼ 0.44A, Rf ¼ 0.65B, Chemical for-
4.1.2.13. 9-(4-Fluorobenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
mula: C15H11FN6. 1H NMR (CDCl3, 300 MHz)
d: 5.54 (s, 2H, eCH2e),
(5m). Yield: 58%, mp: 187e189 ꢀC, Rf ¼ 0.36A, Rf ¼ 0.41B, Chemical
7.11e7.46 (m, 4H, Ar-H), 7.25 (s, 1H, Imidazole-H), 8.18 (s, 1H,
formula: C14H10FN7. 1H NMR (CDCl3, 300 MHz)
d
: 5.49 (s, 2H,
Imidazole-H), 8.40 (s, 1H, Imidazole-H), 8.83 (s, 1H, Imidazole-H),
eCH2e), 7.04e7.37 (dd, 4H, Ar-H), 8.19 (s, 1H, Triazole-H), 8.29 (s,
9.18 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 41.55,
1H, Triazole-H), 8.92 (s, 1H, Imidazole-H), 9.69 (s, 1H, Pyrimidine-
99.99, 115.83 (d, Jc-f ¼ 21.0 Hz), 117.34, 122.22, 124.86 (d, Jc-
H). 13C NMR (CDCl3, 75 MHz)
d
: 47.11, 116.16, 116.45, 122.23,
¼ 3.75 Hz), 130.62, 130.79 (d, Jc-f ¼ 3.75 Hz), 131.09, 137.60 (d, Jc-
f
129.93 (d, Jc-f ¼ 8.2 Hz), 130.50, 145.15, 145.34 (d, Jc-f ¼ 6.0 Hz),
¼
7.42 Hz), 144.42, 145.68, 152.38, 153.64, 164.53 (d, Jc-
f
152.40, 154.06, 154.30, 164.50 (d, Jc-f ¼ 247.5 Hz). IR (KBr) cmꢁ1
:
¼ 247.5 Hz). IR (KBr) cmꢁ1: 1602 1579. MS-EI m/z 295 (M þ 1). ESI-
f
1602 1577. MS-EI m/z 296 (M þ 1). ESI-HRMS calcd for C14H10FN7þ
HRMS calcd for C15H11FNþ6 ([M þ H]þ): 295.1102; found: 295.1100.
([M þ H]þ): 296.1054; found: 296.1047.
4.1.4. General procedure for the synthesis of 9-alkyl-6-(4-methyl-
1H-imidazol-1-yl)-9H-purine (7aeb)
4.1.2.14. 9-(4-Methylbenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5n). Yield: 53%, mp: 188e190 ꢀC, Rf ¼ 0.39A, Rf ¼ 0.43B, Chemical
6-Chloro-9-alkyl-9H-purine (2 mmol), 4-methylimidazole
(2.2 mmol), and K2CO3 (2.2 mmol) were placed into a round-
bottomed flask containing N, N-dimethylformamide (25 ml). After
stirring for 10 h at 150 ꢀC, the solvent was removed under reduced
pressure. The residue was purified by silica gel chromatography
(CH2Cl2 : CH3OH ¼ 100 : 1).
formula: C15H13N7. 1H NMR (CDCl3, 300 MHz)
d: 2.35 (s, 3H, eCH3),
5.47 (s, 2H, eCH2e), 7.17e7.25 (dd, 4H, Ar-H), 8.18 (s, 1H, Triazole-
H), 8.30 (s, 1H, Triazole-H), 8.93 (s, 1H, Imidazole-H), 9.71 (s, 1H,
Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 21.16, 47.62, 122.26,
127.96, 127.96, 129.94, 129.94, 131.51, 138.87, 145.08, 145.27, 145.56,
152.32, 154.02, 154.40. IR (KBr) cmꢁ1: 1604 1578. MS-EI m/z 292
(M þ 1). ESI-HRMS calcd for C15H13Nþ7 ([M þ H]þ): 292.1305; found:
292.1296.
4.1.4.1. 9-Decyl-6-(4-methyl-1H-imidazol-1-yl)-9H-purine
(7a).
Yield: 36%, mp: 28e29 ꢀC, Rf ¼ 0.47A, Rf ¼ 0.71B, Chemical formula:
C
19H28N6. 1H NMR (CDCl3, 300 MHz)
d
: 0.86 (t, 3H, J ¼ 6.52 Hz,
4.1.2.15. 9-(4-Methoxybenzyl)-6-(1H-1,2,4-triazol-1-yl)-9H-purine
eCH3), 1.24e1.97 (m, 16H, eCH2e), 2.89 (s, 3H, eCH3), 4.31 (t, 2H,
J ¼ 7.20 Hz, eCH2e), 7.08(s, 1H, Methylimidazole-H), 8.08 (s, 1H,
Methylimidazole-H), 8.49 (s, 1H, Imidazole-H), 8.83 (s, 1H,
(5o). Yield: 75%, mp: 174e175 ꢀC, Rf ¼ 0.35A, Rf ¼ 0.39B, Chemical
formula: C15H13N7O. 1H NMR (CDCl3, 300 MHz)
d: 3.81 (s, 3H,
eOCH3), 5.45 (s, 2H, eCH2e), 6.89e7.32 (dd, 4H, Ar-H), 8.17 (s, 1H,
Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 14.04, 17.77, 22.60,
Triazole-H), 8.30 (s, 1H, Triazole-H), 8.94 (s, 1H, Imidazole-H), 9.71
26.61, 28.95, 29.18, 29.34, 29.39, 29.87, 31.78, 44.29, 120.54, 123.63,
128.21, 144.13, 146.95, 147.45, 151.56, 153.56. IR (KBr) cmꢁ1: 1602
1579. MS-EI m/z 341 (M þ 1). ESI-HRMS calcd for C19H28N6þ
([M þ H]þ): 341.2448; found: 341.2448.
(s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 47.40, 55.33,
114.62, 114.62, 122.31, 126.50, 129.54, 129.54, 138.17, 145.05, 145.29,
145.47, 152.28, 153.97, 154.34. IR (KBr) cmꢁ1: 1604 1578. MS-EI m/z
308 (M þ 1). ESI-HRMS calcd for C15H13N7Oþ ([M þ H]þ): 308.1254;
found: 308.1244.
4.1.4.2. 9-(2-Fluorobenzyl)-6-(4-methyl-1H-imidazol-1-yl)-9H-pu-
rine (7b). Yield: 48%, mp: 140e142 ꢀC, Rf ¼ 0.50A, Rf ¼ 0.69B,
4.1.2.16. 9-Benzyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine
(5p). Yield:
Chemical formula: C16H14FN6. 1H NMR (CDCl3, 300 MHz)
d: 2.90 (s,
79%, mp: 165e166 ꢀC, Rf ¼ 0.37A, Rf ¼ 0.41B, Chemical formula:
3H, eCH3), 5.54 (s, 2H, eCH2e), 7.08e7.46 (m, 4H, Ar-H), 7.14 (s, 1H,
C
14H11N7. 1H NMR (CDCl3, 300 MHz)
d: 5.52 (s, 2H, eCH2e), 7.32e7.39
Methylimidazole-H), 8.17 (s, 1H, Methylimidazole-H), 8.50 (s, 1H,
(m, 5H, Ar-H), 8.19 (s, 1H, Triazole-H), 8.30 (s, 1H, Triazole-H), 8.93 (s,
Triazole-H), 8.86 (s, 1H, Imidazole-H), 9.18 (s, 1H, Pyrimidine-H). 13
C
1H, Imidazole-H), 9.71 (s, 1H, Pyrimidine-H). 13C NMR (CDCl3,
NMR (CDCl3, 75 MHz)
d
: 17.98, 41.54, 116.11 (d, Jc-f ¼ 21.0 Hz),

582
S.-B. Wang et al. / European Journal of Medicinal Chemistry 84 (2014) 574e583
120.54, 122.17 (d, Jc-f ¼ 14.2 Hz), 123.41, 124.85, 128.54, 130.83 (d, Jc-
(d, Jc-f ¼ 246.0 Hz). IR (KBr) cmꢁ1: 1608 1580. MS-EI m/z 328
(M þ 1). ESI-HRMS calcd for C14H10FN7Sþ ([M þ H]þ): 328.0775;
found: 328.0764.
¼ 3.0 Hz), 131.07(d, Jc-f ¼ 8.25 Hz), 144.03, 147.00, 147.64, 151.90,
f
153.50, 162.48 (d, Jc-f ¼ 246.0 Hz). IR (KBr) cmꢁ1: 1604 1579. MS-EI
m/z 309 (M þ 1). ESI-HRMS calcd for C16H14FNþ6 ([M þ H]þ):
309.1258; found: 309.1251.
4.2. Pharmacology
4.1.5. General procedure for the synthesis of 9-alkyl-6-(1H-pyrazol-
1-yl)-9H-purine (8aeb)
4.2.1. Anticonvulsant effects in the MES test [26,27]
Seizures were elicited using a 60 Hz alternating current with an
intensity of 50 mA in mice. The current was applied via corneal
electrodes for 0.2 s. Protection against the spread of MES-induced
seizures was defined as the abolition of the hind leg, and the
tonic maximal extension component of the seizure. Thirty minutes
after administration of the compounds, their activities were eval-
uated in the MES test.
A mixture of 6-chloro-9-alkyl-9H-purine (2 mmol), pyrazole
(2.2 mmol), and K2CO3 (2.2 mmol) in DMF (20 ml) was refluxed for
12 h. After removing half of the solvent,150 ml of water was poured
into the flask, and the precipitate was filtered and recrystallized in
ethyl acetate (or ethanol) to produce a white solid.
4.1.5.1. 9-Decyl-6-(1H-pyrazol-1-yl)-9H-purine (8a). Yield: 54%,
mp: 58e59 ꢀC, Rf ¼ 0.43A, Rf ¼ 0.51B, Chemical formula: C18H26N6.
4.2.2. Neurotoxicity (NT) screening [26,27]
1H NMR (CDCl3, 300 MHz)
d: 0.88 (t, 3H, J ¼ 6.45 Hz, eCH3),
The neurotoxicity of the compounds was measured in mice
using the rotarod test. Mice were trained to stay on an accelerating
rotarod (diameter, 3.2 cm) rotating at 10 rpm. Trained animals were
injected with the test compounds (i.p.) and neurotoxicity was
measured as the inability of the animal to maintain equilibrium on
the rod for at least 1 min in each of the trials.
1.25e1.95 (m, 16H, eCH2e), 4.33 (t, 2H, J ¼ 7.24 Hz, eCH2e), 6.59 (t,
1H, Pyrazole-H), 8.00 (s, 1H, Pyrazole-H), 8.15 (d, 1H, Pyrazole-H),
8.83 (s, 1H, Imidazole-H), 9.04 (s, 1H, Pyrimidine-H). 13C NMR
(CDCl3, 75 MHz) d: 14.10, 22.65, 26.62, 29.00, 29.23, 29.39, 29.43,
29.91, 31.83, 44.28, 108.93, 130.52, 144.64, 144.76, 151.96, 153.53,
154.06, 157.02. IR (KBr) cmꢁ1: 1602 1579. MS-EI m/z 327 (M þ 1).
ESI-HRMS calcd for C18H26Nþ6 ([M þ H]þ): 327.2292; found:
327.2292.
4.2.3. sc-PTZ-induced seizures [26,27]
Thirty minutes after the administration of the test compound,
85 mg/kg PTZ dissolved in saline was administered (s.c.). The ani-
mals (10 mice/group) were placed in individual cages and observed
for 0.5 h. The number of clonic seizure (ranging from exaggerated
twitches of the limbs to violent shaking or vibrating of the stiffened
extremities), tonic seizure (the extremities pull towards the body or
rigidly push away from it, usually with maximal extension of the
hind leg) and deaths were recorded.
4.1.5.2. 9-(2-Fluorobenzyl)-6-(1H-pyrazol-1-yl)-9H-purine
(8b).
Yield: 56%, mp: 179e180 ꢀC, Rf ¼ 0.46A, Rf ¼ 0.53B, Chemical for-
mula: C15H11FN6. 1H NMR (CDCl3, 300 MHz)
d: 5.54 (s, 2H, eCH2e),
6.57 (t, 1H, Pyrazole-H), 7.12e7.38 (m, 4H, Ar-H), 7.98 (s, 1H,
Pyrazole-H), 8.20 (s, 1H, Pyrazole-H), 8.85 (s, 1H, Imidazole-H), 9.03
(s, 1H, Pyrimidine-H). 13C NMR (CDCl3, 75 MHz)
d: 41.46, 109.01,
115.74 (d, Jc-f ¼ 21.0 Hz), 121.92, 122.8 (d, Jc-f ¼ 14.4 Hz), 124.79 (d, Jc-
¼ 3.75 Hz), 130.62, 130.68, 130.80 (d, Jc-f ¼ 8.25 Hz), 144.60, 144.73,
f
4.2.4. Pharmacological evaluation of compound 5e administered
orally to mice
147.35, 152.24, 153.95, 162.45 (d, Jc-f ¼ 247.5 Hz). IR (KBr) cmꢁ1
:
1604 1579. MS-EI m/z 295 (M þ 1). ESI-HRMS calcd for C15H11FN6þ
We determined the effect of compound 5e over time in the MES
test. A suspension of compound 5e (50 mg/kg) in 0.5% methylcel-
lulose was injected into mice by oral administration (p.o.). The mice
were divided into 6 groups (n ¼ 10). Subsequently, the animals
were subjected to the MES test at various times: 0.5, 1, 1.5, 2, 2.5,
and 3 h. The time of peak effect (TPE) was observed at 1.5 h after p.o.
injection. Then, compound 5e was evaluated for its anticonvulsant
activity against MES-induced seizures and neurotoxicity at its TPE,
when administered orally. This test involved the same procedures
used in the MES test and TOX test screening to determine the ED50
and TD50 values, except the test drug was administered orally to
mice.
([M þ H]þ): 295.1102; found: 295.1095.
4.1.6. Synthesis of 9-alkyl-6-(3H-1,2,4-triazol-3-ylthio)-9H-purine
(9aeb)
CH3ONa (2.2 mmol), 6-chloro-9-alkyl-9H-purine (2 mmol) and
1H (2H),(4H)-1,2,4-triazole-3-thiol were dissolved in acetonitrile
(30 ml) and stirred for 18 h at room temperature. After removing
the acetonitrile under reduced pressure, the residue was purified
by silica gel chromatography (CH2Cl2 : CH3OH ¼ 50 : 1).
4.1.6.1. 9-Decyl-6-(3H-1,2,4-triazol-3-ylthio)-9H-purine
(9a).
Yield: 75%, mp: 140e142 ꢀC, Rf ¼ 0.12A, Rf ¼ 0.13B, Chemical
formula: C17H25N7Sþ. 1H NMR (CDCl3, 300 MHz)
d: 0.87 (t, 3H,
Conflict of interest
J ¼ 6.60 Hz, eCH3), 1.25e1.96 (m, 16H, eCH2e), 1.73 (s, 1H,
eNHe), 4.34 (t, 2H, J ¼ 7.21 Hz, eCH2e), 8.18 (s, 1H, Triazole-H),
8.90 (s, 1H, Imidazole-H), 9.82 (s, 1H, Pyrimidine-H). 13C NMR
We declare that we have no conflict of interest with respect to
this study.
(CDCl3, 75 MHz) d: 14.07, 18.42, 22.63, 26.60, 28.95, 29.20, 29.86,
31.80, 44.48, 58.44, 122.16, 144.41, 145.64, 147.36, 152.15, 154.26,
163.24. IR (KBr) cmꢁ1: 1608 1579. MS-EI m/z 360 (M þ 1). ESI-
HRMS calcd for C17H25N7Sþ ([M þ H]þ): 360.1965; found:
360.1951.
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (No. 81160382) and National Science and
Technology Major Project of China (No. 2012ZX09103-101-044)
4.1.6.2. 9-(2-Fluorobenzyl)-6-(3H-1,2,4-triazol-3-ylthio)-9H-purine
(9b). Yield: 35%, mp: 156e158 ꢀC, Rf ¼ 0.11A, Rf ¼ 0.14B Chemical
References
formula: C14H10FN7S. 1H NMR (CDCl3, 300 MHz)
d: 1.85 (s, 1H,
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