Synthesis of some newer analogues of 4-hydroxyphenyl acetic acid as potent anti-inflammatory agents

Article abstract of DOI:10.1002/jccs.200800030

A series of 1,3,4-oxadiazole and 1,2,4-triazole derivatives of 4-hydroxyphenyl acetic acid have been synthesized and evaluated for their anti-inflammatory activity by carrageenan induced rat paw edema method. The compounds, which showed good anti-inflammatory activity, were screened for their ulcerogenic and lipid peroxidation activities.

Full text of DOI:10.1002/jccs.200800030

Journal of the Chinese Chemical Society, 2008, 55, 201-208
201
Synthesis of Some Newer Analogues of 4-Hydroxyphenyl Acetic Acid as
Potent Anti-inflammatory Agents
Mohammad Amir,* Sadique A. Javed and Harish Kumar
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Hamdard University,
New Delhi - 110 062, India
A series of 1,3,4-oxadiazole and 1,2,4-triazole derivatives of 4-hydroxyphenyl acetic acid have been
synthesized and evaluated for their anti-inflammatory activity by carrageenan induced rat paw edema
method. The compounds, which showed good anti-inflammatory activity, were screened for their ulcer-
ogenic and lipid peroxidation activities.
Keywords: 1,3,4-Oxadiazoles; 1,2,4-Triazoles; Anti-inflammatory; Ulcerogenic; Lipid
peroxidation.
INTRODUCTION
with an improved therapeutic index.
It has been reported in the literature that derivatiza-
tion of the carboxylate function of representative NSAIDs
resulted in increased anti-inflammatory activity with re-
duced ulcerogenic effect.18,19 It was also observed that cer-
tain 5-membered heterocyclic compounds bearing 1,3,4-
oxadiazole and 1,2,4-triazole nuclei possess interesting
anti-inflammatory activity with fewer GI side effects.20-22
Moreover, phenolic compounds have also been reported to
possess good anti-inflammatory and antioxidant activi-
ties.23,24 In view of these observations and in continuation
of our research programmeon the synthesis of 5-membered
heterocyclic compounds of acetic acid derivatives,25,26 we
herein report the synthesis of some newer, more potent ana-
logues of 4-hydroxyphenyl acetic acid by replacing the
carboxylic acid group with 1,3,4-oxadiazole and 1,2,4-tri-
azole nuclei, which have been found to possess an interest-
ing profile of anti-inflammatory activity with significant
reduction in their ulcerogenic effect. The structure of the
newly synthesized compounds was confirmed by elemental
and spectral analysis.
The pharmacological activity of NSAIDs is related
to the suppression of prostaglandin biosynthesis from
arachidonic acid by inhibiting the enzyme cyclooxygen-
ases (COXs).1,2 Recently it was discovered that COX exists
in two isoforms, COX-1 and COX-2, which were regulated
differently.3-5 COX-1 provides cytoprotection in the gas-
trointestinal (GI) tract, whereas inducible COX-2 mediates
inflammation.6-8 Since most of the NSAIDs in the market
show greater selectivity for COX-1 than COX-2,9 chronic
use of NSAIDs may elicit appreciable GI irritation, bleed-
ing and ulceration.10 The GI toxicity of acidic non-steroidal
anti-inflammatory drugs is one of the most challenging
problems in medicinal chemistry, since these side effects
are usually related to the intrinsic mechanism responsible
for the desired activity.11,12 It is probably caused by a com-
bination of local irritation produced by direct contact of
free carboxylic group of NSAIDs and inhibition of enzyme
COX-1 responsible for gastric mucosal protection.1,13
A
survey of the literature has also revealed that local genera-
tion of various reactive oxygen species (ROS) may be play-
ing a significant role in the formation of gastric mucosal le-
sions associated with NSAID therapy.14,15 This fact was
further supported by the finding that indomethacin admin-
istration results in increased ROS production in the gastric
mucosa,16,17 followed by gastric ulceration. Thus the dis-
covery of molecules which combine anti-inflammatory and
antioxidant activities may lead to development of drugs
RESULTS AND DISCUSSION
Chemistry
The acid hydrazide 1 was prepared by esterification
of 4-hydroxyphenylacetic acid followed by treatment with
hydrazine hydrate in absolute ethanol. The reaction of
hydrazide 1 with carbon disulphide in alkaline medium af-
* Corresponding author. Tel: +91-11-26059878; Fax: +91-11-26059688 Extn. 5307; E-mail: mamir_s2003@yahoo.co.in

202 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Amir et al.
forded, after acidic treatment, 5-(4-hydroxyphenyl)meth-
yl-2-mercapto-1,3,4-oxadiazole 2. The IR spectra of com-
pound 2 revealed the presence of absorption bands at 1165
cm-1 for the C=S group and at 1662 cm-1 due to C=N stretch-
Protocol for synthesis of 4-hydroxyphenyl
acetic acid derivatives
Scheme I
1
ing vibrations. The H NMR spectrum of compound 2
showed a broad singlet at d 12.09 for the SH proton, con-
firming the formation of a mercaptotriazole ring. The mass
spectra showed a molecular ion peak M+ at m/z 208 corre-
sponding to the molecular formula C9H8N3O2S. The hydra-
zide on treatment with various aryl/alkyl isothiocyanates
gave N1-[2-(4-hydroxyphenyl)acetyl] N4-aryl/alkyl-3-thio-
semicarbazides 3a-i. The structure of thiosemicarbazide 3c
was confirmed by its IR spectrum, which displayed absorp-
tion bands at 3392 cm-1 for NH, 1696 cm-1 due to C=O and
1183 cm-1 corresponding to C=S stretching vibrations. The
1H NMR spectrum showed a singlet at d 9.27 for the NHAr-
Cl proton. The CSNH and CONH protons were obtained as
a broad singlet at d 9.69 confirming the presence of a thio-
semicarbazide group. The mass spectra showed a molecu-
lar ion peak M+ at m/z 335 corresponding to the molecular
formula C15H14ClN3O2S. The thiosemicarbazides were ox-
idatively cyclised to 5-(4-hydroxyphenyl)methyl-2-aryl/
alkylamino-1,3,4-oxadiazoles 4a-i by elimination of H2S
gas using iodine and potassium iodide in ethanolic sodium
hydroxide. The IR spectrum of oxadiazole 4a showed an
absorption peak at 1664 cm-1 due to C=N stretching vibra-
tion. Its 1H NMR spectrum showed a multiplet at d 6.66-
7.53 for 9 aromatic protons and a singlet for the NH proton
at d 9.02. In its 13C NMR spectrum, CH2 appeared at d 31.0.
The oxadiazole ring carbons C-5 and C-2 appeared at d
152.1 and d 168.2, respectively. The structure of compound
4a was further supported by its mass spectra, which showed
a molecular ion peak M+ at m/z 267 corresponding to mo-
lecular formula C15H13N3O2. The thiosemicarbazides 3a-i
on heating with 4N NaOH in ethanol underwent smooth
cyclisation through dehydration to afford 5-(4-hydroxy-
phenyl)methyl-4-aryl/alkyl-3-mercapto-1,2,4(H)-triazoles
5a-i (Scheme I). The structure of triazole 5g was confirmed
by its IR spectrum, which displayed absorption bands at
1645 cm-1 for C=N and at 1162 cm-1 corresponding to C=S
stretching vibrations. Its 1H NMR spectrum showed two
singlets at d 2.36 and d 3.70 for CH3 and CH2 protons, re-
spectively. The singlet of the SH proton was obtained at d
9.31. In its 13C NMR spectrum, a CH2 carbon appeared at d
30.5, whereas a CH3 carbon appeared at d 20.7. The tri-
azole ring carbons C-5 and C-3 were observed at d 151.7
and d 156.1, respectively. The structure of compound 5g
was further confirmed by its mass spectra, which showed a
molecular ion peak M+ at m/z 297 corresponding to the mo-
lecular formula C16H15N3OS. The purity of the compounds
was checked by TLC and elemental analysis.
Anti-inflammatory Activity
The anti-inflammatory activity of the synthesized
compounds 2, 4a-i & 5a-i was evaluated by the carrage-
enan induced paw edema method of Winter et al., edema
being measured after 3 and 4 hr of carrageenan treatment.
Since % inhibition was found to be greater after 4 hr, this
was made the basis of discussion. All compounds (2, 4a-i
& 5a-i) showed anti-inflammatory activity in this test at an
equimolar oral dose relative to 70 mg/kg ibuprofen. The
tested compounds showed anti-inflammatory activity rang-
ing from 37.37 to 83.83% (Table 2), and the standard drug
ibuprofen showed 86.36% inhibition after 4 hr. The oxadi-
azole derivative 4h having a 4-methoxyphenyl amino group
at the 2nd position of 1,3,4-oxadiazole nucleus, showed
77.77% activity, whereas the activity of 4a void of the
4-methoxy from the C-2 substituent in 4h was found to be
minimal (37.37%). When the 4-methoxy group was re-
placed by 2-chloro (4b) and 4-methyl (4g), the compounds
showed high activity, 65.55 and 62.62%, respectively.
However, replacement of this 4-methoxy group by the ha-
lide, 4-chloro (4c), 4-bromo (4d), 4-fluoro (4e), or C-2 sub-
stituent by n-butyl amino group (4i) showed lower activity.
The 1,2,4-triazole derivatives showed anti-inflamma-
tory activity ranging from 51.51 to 83.83% (Table 2) after 4

New Azole Analogues of 4-Hydroxyphenyl Acetic Acid
J. Chin. Chem. Soc., Vol. 55, No. 1, 2008 203
Table 1. Physical constants of synthesized compounds
N
N
N
N
R
HO
HO
N
O
SH
N
R
H
4a-i
5a-i
Compound
R
Yield (%)
M.P. (°C)
Mol. Formula
2
--
45
63
56
67
69
62
64
72
69
73
68
67
76
69
66
66
81
78
57
166
206
198
222
214
242
218
236
208
124
192
206
236
220
248
226
250
220
170
C9H8N3O2S
4a
4b
4c
4d
4e
4f
Phenyl
C15H13N3O2
C15H12ClN3O2
C15H12ClN3O2
C15H12BrN3O2
C15H12FN3O2
C16H15N3O2
C16H15N3O2
C16H15N3O3
C13H17N3O2
C15H13N3OS
C15H12ClN3OS
C15H12ClN3OS
C15H12BrN3OS
C15H12FN3OS
C16H15N3OS
C16H15N3OS
C16H15N3O2S
C13H17N3OS
2-Chlorophenyl
4-Chlorophenyl
4-Bromophenyl
4-Fluorophenyl
2-Methylphenyl
4-Methylphenyl
4-Methoxyphenyl
n-Butyl
4g
4h
4i
5a
5b
5c
5d
5e
5f
Phenyl
2-Chlorophenyl
4-Chlorophenyl
4-Bromophenyl
4-Fluorophenyl
2-Methylphenyl
4-Methylphenyl
4-Methoxyphenyl
n-Butyl
5g
5h
5i
hr. The highest activity was found for compound 5i having
an n-butyl group at 4th position of the triazole ring. When
this group was replaced by 2-methylphenyl group 5f, the
activity was found to be minimal (49.99%). The triazole
derivative 5d having a 4-bromophenyl group also showed
high activity (65.15%). The rest of the compounds showed
moderate activity.
Lipid Peroxidation
All the compounds screened for ulcerogenic activity
were also analyzed for lipid peroxidation. Lipid peroxida-
tion is measured as nmole of malondialdehyde (MDA)/100
mg of gastric mucosa tissue. Ibuprofen (standard drug)
showed maximum lipid peroxidation (6.153
0.18),
whereas the control group showed 3.269 0.05. It was
found that all cyclised derivatives showing less ulcero-
genic activity also showed a reduction in lipid peroxidation
Table 2. Thus these studies showed that synthesized com-
pounds have inhibited the induction of gastric mucosal le-
sions, and results further suggested that their protective ef-
fect is related to the inhibition of lipid peroxidation in the
gastric mucosa.
Acute Ulcerogenicity
The compounds 4b-c, 4g-i, 5c-e & 5h-i that showed
anti-inflammatory activity higher than 55% were screened
for their ulcerogenic activity. All the compounds were
tested at an equimolar oral dose relative to 200 mg/kg
ibuprofen. The maximum reduction in ulcerogenic activity
(0.333 ± 0.10) was found in triazole derivatives 5c, 5e & 5i
having 4-chlorophenyl, 4-fluorophenyl and n-butyl groups,
respectively (Table 2). The other two triazole derivatives
5d & 5h showed a moderate severity index. The oxadiazole
derivative 4h showing high anti-inflammatory activity also
showed a reduction in severity index (0.417 ± 0.08). The
rest of the oxadiazole derivatives showed moderate sever-
ity indexes. The standard drug ibuprofen showed a high se-
verity index of 2.00 ± 0.12.
CONCLUSION
In summary, various 1,3,4-oxadiazole and 1,2,4-tri-
azole derivatives were prepared with the objective of de-
veloping better anti-inflammatory molecules with mini-
mum ulcerogenic activity. It was interesting to note that
five cyclised compounds 4b, 4g, 4h, 5d and 5i were found
to have more than 60% anti-inflammatory activity in com-

204 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Amir et al.
Table 2. Anti-inflammatory, ulcerogenic and lipid peroxidation activities of the synthesized
compounds
Anti-inflammatory activity#
(% inhibition ± SEM)
Ulcerogenic activity#
(Severity Index ± SEM) SEM/100 mg tissue#
nmol MDA content ±
Compound
After 3 hr After 4 hr
Control
0
0
0
3.269 ± 0.05a
Ibuprofen
2
83.32 ± 2.79
37.87 ± 2.53
33.33 ± 1.96
52.93 ± 2.15
48.03 ± 1.80
42.14 ± 1.80
35.29 ± 2.14
42.14 ± 2.35
55.87 ± 2.52
71.55 ± 2.35
41.16 ± 2.14
42.42 ± 3.03
45.45 ± 3.31
49.99 ± 2.03
57.57 ± 3.03
45.45 ± 2.34
43.93 ± 2.79
36.36 ± 2.34
48.48 ± 1.91
72.54 ± 1.96
86.36 ± 2.03a
46.96 ± 2.79a
37.37 ± 2.02a
65.65 ± 2.02a
55.55 ± 2.55a
48.48 ± 3.03a
44.44 ± 3.64a
54.54 ± 2.59a
62.62 ± 2.43a
77.77 ± 2.02c
57.57 ± 3.49a
51.51 ± 1.91a
51.51 ± 3.03a
59.08 ± 2.03a
65.15 ± 2.79a
56.78 ± 3.90a
49.99 ± 2.03a
45.45 ± 3.45a
59.08 ± 2.03a
83.83 ± 2.43a
2.000 ± 0.12a
6.153 ± 0.18a
-
-
4a
4b
4c
-
-
0.667 ± 0.16c
4.518 ± 0.07a
0.500 ± 0.00a
4.193 ± 0.12b
4d
4e
-
-
-
-
4f
-
-
4g
4h
4i
0.500 ± 0.13b
0.417 ± 0.08b
0.500 ± 0.00a
-
4.241 ± 0.14b
4.177 ± 0.16b
4.257 ± 0.07a
-
5a
5b
5c
-
-
0.333 ± 0.10b
0.417 ± 0.08b
0.333 ± 0.10b
-
4.122 ± 0.11b
4.160 ± 0.14b
4.131 ± 0.15b
-
5d
5e
5f
5g
5h
5i
-
-
0.417 ± 0.08b
0.333 ± 0.10b
4.134 ± 0.13b
4.113 ± 0.13b
Data were analyzed by Student’s t test for n = 6; a p < 0.0001, b p < 0.001, c p < 0.01.
# Relative to ibuprofen.
parison to the standard drug (ibuprofen 86.36%) against
carrageenin induced paw edema in rats. The presence of a
4-methoxyphenylamino group at the second position of the
oxadiazole ring (4h) showed a maximum anti-inflamma-
tory activity of 77.77%. The compounds having a 2-chloro
phenyl amino group 4b and 4-methyl amino group 4g also
showed a high activity of 65.65 and 66.62%, respectively.
It was further noted that the presence of the n-butyl group at
the fourth position of the triazole ring (5i) showed the
highest anti-inflammatory activity 83.83%, whereas the
presence of an n-butyl amino group at the second position
in an oxadiazole ring (4i) showed lower activity (57.57%).
The presence of a 4-bromophenyl group at the fourth posi-
tion of a triazole nucleus (5d) also showed high activity
(65.15%).
these studies, compound 5i, a triazole derivative, has emerged
as a lead compound, which showed maximum reduction in
ulcerogenic activity and lipid peroxidation. Thus the basic
objective of reducing ulcerogenic potential of synthesized
compounds was achieved, and the series provided a new
opportunity for possible modification of pharmacophoric
requirements and future exploitations.
EXPERIMENTAL
Melting points were determined in open capillary
tubes and are uncorrected. IR (KBr) spectra were recorded
on a Nicolet, 5PC FTIR spectrometer (nmax in cm-1). 1H and
13C NMR spectra were recorded at 300 and 75 MHz, re-
spectively, on a Bruker DRX-300 spectrometer using TMS
as internal reference (chemical shift in d ppm). Mass spec-
tra were recorded on a Jeol SX-102 spectrometer. Chemi-
cals were purchased from Merck Chemical Company, S. D.
Fine (India) and Qualigens (India). Ethyl-2-(4-hydroxy-
phenyl) acetate was prepared by a procedure given in the
These compounds were tested for ulcerogenic activ-
ity and showed a significant reduction in the severity index
compared to the standard reference drug. It was noted that
triazole derivatives showed maximum reduction in ulcero-
genic activity followed by oxadiazole derivatives. From

New Azole Analogues of 4-Hydroxyphenyl Acetic Acid
literature.27
J. Chin. Chem. Soc., Vol. 55, No. 1, 2008 205
NH-C=S), 10.09 (bs, 1H, OH); MS (m/z) 335 (M+); Anal.
Calcd for C15H14ClN3O2S: C, 53.65; H, 4.20; N, 12.51.
Found: C, 53.53; H, 4.29; N, 12.45.
4-Hydroxyphenyl acetic acid hydrazide (1)
To a mixture of ethyl-2-(4-hydroxyphenyl) acetate
(0.01 mol) and hydrazine hydrate (0.20 mol), absolute eth-
anol (50 mL) was added, and it was refluxed for 24 hr on a
water bath. The mixture was concentrated, cooled and
poured into crushed ice. It was kept for 4-5 hr at room tem-
perature, and the solid mass that separated out was filtered,
dried and recrystallized from ethanol.
IR: (KBr) cm-1 3596 (OH), 3406 (N-H), 2981 (C-H),
1690 (C=O), 1582 (C=C); 1H NMR (DMSO-d6): d 3.20 (s,
2H, CH2), 4.19 (s, 2H, NH2), 6.65 (d, 2H, 2,6-ArH), 7.05
(d, 2H, 3,5-ArH), 9.13 (s, 1H, CONH), 9.22 (bs, 1H, OH).
N1-[2-(4-hydroxyphenyl)acetyl] N4-(4-methoxyphenyl)-
3-thiosemicarbazide (3h)
IR: (KBr) cm-1 3571 (OH), 3237 (N-H), 2963 (C-H),
1660 (C=O), 1572 (C=C), 1146 (C=S); 1H NMR (DMSO-
d6): d 3.51 (s, 2H, CH2), 3.81 (s, 3H, OCH3), 6.65 (d, 2H,
2,6-ArH), 7.01 (d, 2H, 3,5-ArH), 7.32 (d, 2H, 2¢,6¢-ArH-
OCH3), 7.45 (d, 2H, 3¢,5¢-ArH-OCH3), 9.23 (s, 1H, NHAr-
OCH3), 9.58 (bs, 2H, CONH-NH-C=S), 10.02 (bs, 1H,
OH); MS (m/z) 331 (M+); Anal. Calcd for C16H17N3O3S: C,
57.99; H, 5.17; N, 12.68. Found: C, 57.80; H, 5.10; N,
12.72.
5-(4-Hydroxyphenyl)methyl-2-mercapto-1,3,4-oxadi-
azole (2)
General procedure for 5-(4-hydroxyphenyl)methyl-2-
aryl/alkylamino-1,3,4-oxadiazoles (4a-i)
A mixture of 4-hydroxyphenyl acetic acid hydrazide
1 (0.005 mol), potassium hydroxide (0.005 mol) and car-
bon disulphide (5 mL) in ethanol (50 mL) was refluxed on a
water bath for 10 hr. The solution was then concentrated,
cooled and acidified with dilute hydrochloric acid. The
solid that separated out was filtered and recrystallized from
ethanol.
IR: (KBr) cm-1 3611 (OH), 2987 (C-H), 1662 (C=N),
1586 (C=C), 1165 (C=S); 1H NMR (DMSO-d6): d 3.70 (s,
2H, CH2), 6.77 (d, 2H, 2,6-ArH), 7.19 (d, 2H, 3,5-ArH),
9.69 (bs, 1H, OH), 12.09 (bs, 1H, SH); MS (m/z) 208 (M+);
Anal. Calcd for C9H8N3O2S: C, 51.91; H, 3.87; N, 13.45; S,
15.80. Found: C, 51.93; H, 3.89; N, 13.44; S, 15.82.
Asuspension of thiosemicarbazide (3a-i) (0.002 mol)
in ethanol (50 mL) was dissolved in aqueous sodium hy-
droxide (5N, 1 mL) with cooling and stirring resulting in
the formation of clear solution. To this, iodine in potassium
iodide solution (5%) was added dropwise with stirring till
the colour of iodine persisted at room temperature. The re-
action mixture was refluxed for 3 hr on a water bath. It was
then concentrated, kept overnight in the refrigerator, and
the solid thus separated out was recrystallized from etha-
nol.
5-(4-Hydroxyphenyl)methyl-2-phenylamino-1,3,4-
oxadiazole (4a)
General procedure for N1-[2-(4-hydroxyphenyl)acetyl]
N4-alkyl/aryl-3-thiosemicarbazides (3a-i)
IR: (KBr) cm-1 3572 (OH), 3323 (N-H), 2978 (C-H),
1664 (C=N), 1591 (C=C); 1H NMR (DMSO-d6): d 3.89 (s,
2H, CH2), 6.66-7.53 (m, 9H, aromatic), 9.02 (s, 1H, NH),
10.48 (s, 1H, OH); 13C NMR (DMSO-d6): d 31.0, 115.7,
124.9, 128.7, 129.6, 129.9, 134.0, 152.1, 156.5, 168.2; MS:
m/z 267 (M+); Anal. Calcd for C15H13N3O2: C, 67.41; H,
4.90; N, 15.72. Found: C, 67.39; H, 4.92; N, 15.71.
A mixture of 4-hydroxyphenyl acetic acid hydrazide
1 (0.10 mol), aryl/alkyl isothiocyanate (0.10 mol) and etha-
nol (50 mL) was refluxed on a water bath for 5-6 hr. It was
then concentrated, cooled and kept overnight in refrigera-
tor. The white solid that separated out was filtered, dried
and recrystallised from a suitable solvent.
5-(4-Hydroxyphenyl)methyl-2-(2-chlorophenylamino)-
1,3,4-oxadiazole (4b)
N1-[2-(4-hydroxyphenyl)acetyl] N4-(4-chlorophenyl)-3-
thiosemicarbazide (3c)
IR: (KBr) cm-1 3577 (OH), 3359 (N-H), 2988 (C-H),
1652 (C=N), 1560 (C=C), 712 (C-Cl); 1H NMR (DMSO-
d6): d 3.90 (s, 2H, CH2), 7.01-7.60 (m, 8H, aromatic), 8.99
(s, 1H, NH), 10.41 (s, 1H, OH); MS: m/z 301 (M+); Anal.
Calcd for C15H12ClN3O2: C, 59.71; H, 4.01; N, 13.93.
Found: C, 59.70; H, 3.99; N, 13.96.
IR: (KBr) cm-1 3612 (OH), 3392 (N-H), 3028 (C-H),
1696 (C=O), 1589 (C=C), 1183 (C=S); 1H NMR (DMSO-
d6): d 3.50 (s, 2H, CH2), 6.67 (d, 2H, 2,6-ArH), 7.08 (d, 2H,
3,5-ArH), 7.37 (d, 2H, 2¢,6¢-ArH-Cl), 7.46 (d, 2H, 3¢,5¢-
ArH-Cl), 9.27 (s, 1H, NHAr-Cl), 9.69 (bs, 2H, CONH-

206 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Amir et al.
5-(4-Hydroxyphenyl)methyl-2-(4-chlorophenylamino)-
1,3,4-oxadiazole (4c)
2.36 (s, 2H, CH3), 3.69 (s, 2H, CH2), 6.57 (d, 2H, 2,6-ArH),
6.69 (d, 2H, 3,5-ArH), 7.06 (d, 2H, 2¢,6¢-ArH-CH3), 7.26
(d, 2H, 3¢,5¢-ArH-CH3), 9.26 (s, 1H, NH), 13.25 (bs, 1H,
OH); 13C NMR (DMSO-d6): d 21.2, 31.0, 115.5, 117.2,
125.1, 128.4, 129.9, 131.5, 139.3, 152.1, 156.6, 168.3; MS:
m/z 281 (M+); Anal. Calcd for C16H15N3O2: C, 68.31; H,
5.37; N, 14.94. Found: C, 68.40; H, 5.43; N, 14.91.
IR: (KBr) cm-1 3575 (OH), 3314 (N-H), 2960 (C-H),
1
1633 (C=N), 1576 (C=C), 716 (C-Cl) cm-1; H NMR
(DMSO-d6): d 3.74 (s, 2H, CH2), 6.56 (d, 2H, 2,6-ArH),
6.69 (d, 2H, 3,5-ArH), 7.23 (d, 2H, 2¢,6¢-ArH-Cl), 7.53 (d,
2H, 3¢,5¢-ArH-Cl), 9.33 (s, 1H, NH), 10.55 (s, 1H, OH);
13C NMR (DMSO-d6): d 30.6, 115.1, 118.4, 124.3, 128.8,
129.2, 130.2, 134.0, 151.6, 156.1, 167.9; MS: m/z 301
(M+); Anal. Calcd for C15H12ClN3O2: C, 59.71; H, 4.01; N,
13.93. Found: C, 59.73; H, 3.99; N, 13.95.
5-(4-Hydroxyphenyl)methyl-2-(4-methoxyphenylami-
no)-1,3,4-oxadiazole (4h)
IR: (KBr) cm-1 3569 (OH), 3336 (N-H), 2976 (C-H),
1
1645 (C=N), 1574 (C=C) cm-1; H NMR (DMSO-d6): d
5-(4-Hydroxyphenyl)methyl-2-(4-bromophenylamino)-
1,3,4-oxadiazole (4d)
3.70 (s, 2H, CH2), 3.80 (s, 2H, OCH3), 6.57 (d, 2H, 2,6-
ArH), 6.69 (d, 2H, 3,5-ArH), 6.99 (d, 2H, 2¢,6¢-ArH-
OCH3), 7.10 (d, 2H, 3¢,5¢-ArH-OCH3), 9.29 (s, 1H, NH),
13.79 (bs, 1H, OH); 13C NMR (DMSO-d6): d 30.0, 55.4,
114.4, 115.5, 118.3, 124.6, 126.1, 129.5, 152.0, 156.1, 159.6,
168.1; MS: m/z 297 (M+); Anal. Calcd for C16H15N3O3: C,
64.64; H, 5.09; N, 14.13. Found: C, 64.50; H, 5.01; N,
14.06.
IR: (KBr) cm-1 3569 (OH), 3382 (N-H), 2988 (C-H),
1
1670 (C=N), 1591 (C=C), 596 (C-Br) cm-1; H NMR
(DMSO-d6): d 3.69 (s, 2H, CH2), 6.57 (d, 2H, 2,6-ArH),
6.70 (d, 2H, 3,5-ArH), 7.18 (d, 2H, 2¢,6¢-ArH-Br), 7.48 (d,
2H, 3¢,5¢-ArH-Br), 9.29 (s, 1H, NH), 10.41 (s, 1H, OH);
MS: m/z 346 (M+); Anal. Calcd for C15H12BrN3O2: C,
52.04; H, 3.49; N, 12.14. Found: C, 52.06; H, 3.53; N,
12.19.
5-(4-Hydroxyphenyl)methyl-2-n-butylamino-1,3,4-oxa-
diazole (4i)
5-(4-Hydroxyphenyl)methyl-2-(4-fluorophenylamino)-
1,3,4-oxadiazole (4e)
IR: (KBr) cm-1 3568 (OH), 3378 (N-H), 2966 (C-H),
1
1664 (C=N), 1573 (C=C) cm-1; H NMR (DMSO-d6): d
IR: (KBr) cm-1 3560 (OH), 3300 (N-H), 2980 (C-H),
1630 (C=N), 1573 (C=C), 1090 (C-F); 1H NMR (DMSO-
d6): d 3.77 (s, 2H, CH2), 6.59 (d, 2H, 2,6-ArH), 6.71 (d, 2H,
3,5-ArH), 7.08 (d, 2H, 2¢,6¢-ArH-F), 7.53 (d, 2H, 3¢,5¢-
ArH-F), 9.36 (s, 1H, NH), 10.47 (s, 1H, OH); MS: m/z 285
(M+); Anal. Calcd for C15H12FN3O2: C, 63.15; H, 4.24; N,
14.73. Found: C, 63.16; H, 4.23; N, 14.79.
0.76 (t, J = 6.7 Hz, 3H, CH3), 1.16-1.22 (m, 4H, CH2-CH2),
3.18 (s, 2H, CH2), 3.74 (t, J = 6.9 Hz, 2H, NHCH2), 6.68 (d,
2H, 2,6-ArH), 7.03 (d, 2H, 3,5-ArH), 9.38 (s, 1H, NH),
13.53 (bs, 1H, OH); MS: m/z 247 (M+); Anal. Calcd for
C13H17N3O2: C, 63.14; H, 6.93; N, 16.99. Found: C, 63.10;
H, 6.99; N, 17.01.
General procedure for 5-(4-hydroxyphenyl)methyl-4-
aryl/alkyl-3-mercapto-1,2,4(H)-triazoles (5a-i)
5-(4-Hydroxyphenyl)methyl-2-(2-methylphenylamino)-
1,3,4-oxadiazole (4f)
Asuspension of thiosemicarbazide (3a-i) (0.001 mol)
in ethanol (20 mL) was dissolved in aqueous sodium hy-
droxide solution (4N, 2 mL) and gently refluxed for 2 hr
on a water bath. The resulting solution was concentrated,
cooled and filtered. The pH of the filtrate was adjusted to
5-6 with dilute acetic acid and kept aside for 1 hr. The solid
thus separated out was filtered, washed with water, dried
and recrystallized with ethanol.
IR: (KBr) cm-1 3574 (OH), 3306 (N-H), 2960 (C-H),
1650 (C=N), 1571 (C=C); 1H NMR (DMSO-d6): d 2.16 (s,
2H, CH3), 3.70 (s, 2H, CH2), 6.60-7.18 (m, 8H, aromatic),
8.81 (s, 1H, NH), 11.25 (bs, 1H, OH); MS: m/z 281 (M+);
Anal. Calcd for C16H15N3O2: C, 68.31; H, 5.37; N, 14.94.
Found: C, 68.32; H, 5.40; N, 14.90.
5-(4-Hydroxyphenyl)methyl-2-(4-methylphenylamino)-
1,3,4-oxadiazole (4g)
5-(4-Hydroxyphenyl)methyl-4-phenyl-3-mercapto-
1,2,4(H)-triazole (5a)
IR: (KBr) cm-1 3580 (OH), 3294 (N-H), 2975 (C-H),
1
1663 (C=N), 1575 (C=C) cm-1; H NMR (DMSO-d6): d
IR: (KBr) cm-1 3574 (OH), 2974 (C-H), 1620 (C=N),

New Azole Analogues of 4-Hydroxyphenyl Acetic Acid
J. Chin. Chem. Soc., Vol. 55, No. 1, 2008 207
1578 (C=C), 1169 (C=S); 1H NMR (DMSO-d6): d 3.80 (s,
2H, CH2), 6.79-7.53 (m, 9H, aromatic), 10.09 (s, 1H, SH),
13.06 (s, 1H, OH); MS: m/z 283 (M+); Anal. Calcd for
C15H13N3OS: C, 63.58; H, 4.62; N, 14.83. Found: C, 63.60;
H, 4.66; N, 14.89.
5-(4-Hydroxyphenyl)methyl-4-(2-methylphenyl)-3-mer-
capto-1,2,4(H)-triazole (5f)
IR: (KBr) cm-1 3561 (OH), 2971 (C-H), 1647 (C=N),
1586 (C=C), 1157 (C=S); 1H NMR (DMSO-d6): d 2.31 (s,
3H, CH3), 3.78 (s, 2H, CH2), 6.57-7.37 (m, 8H, aromatic),
9.42 (s, 1H, SH), 13.60 (bs, 1H, OH); MS: m/z 297 (M+);
Anal. Calcd for C16H15N3OS: C, 64.62; H, 5.08; N, 14.13.
Found: C, 64.65; H, 5.00; N, 14.15.
5-(4-Hydroxyphenyl)methyl-4-(2-chlorophenyl)-3-mer-
capto-1,2,4(H)-triazole (5b)
IR: (KBr) cm-1 3576 (OH), 2963 (C-H), 1648 (C=N),
1588 (C=C), 1181 (C=S), 769 (C-Cl); 1H NMR (DMSO-
d6): d 4.00 (s, 2H, CH2), 6.71-7.53 (m, 8H, aromatic), 9.37
(s, 1H, SH), 13.83 (s, 1H, OH); MS: m/z 317 (M+); Anal.
Calcd for C15H12ClN3OS: C, 56.69; H, 3.81; N, 13.22.
Found: C, 56.63; H, 3.89; N, 13.29.
5-(4-Hydroxyphenyl)methyl-4-(4-methylphenyl)-3-mer-
capto-1,2,4(H)-triazole (5g)
IR: (KBr) cm-1 3547 (OH), 2979 (C-H), 1645 (C=N),
1
1591 (C=C), 1162 (C=S) cm-1; H NMR (DMSO-d6): d
2.36 (s, 3H, CH3), 3.70 (s, 2H, CH2), 6.56 (d, 2H, 2,6-ArH),
6.69 (d, 2H, 3,5-ArH), 7.07 (d, 2H, 2¢,6¢-ArH-CH3), 7.27
(d, 2H, 3¢,5¢-ArH-CH3), 9.31 (s, 1H, SH), 13.64 (bs, 1H,
OH); 13C NMR (DMSO-d6): d 20.7, 30.5, 115.1, 124.6,
128.0, 129.5, 129.7, 131.0, 139.0, 151.7, 156.1, 167.9; MS:
m/z 297 (M+); Anal. Calcd for C16H15N3OS: C, 64.62; H,
5.08; N, 14.13. Found: C, 64.56; H, 5.00; N, 14.09.
5-(4-Hydroxyphenyl)methyl-4-(4-chlorophenyl)-3-mer-
capto-1,2,4(H)-triazole (5c)
IR: (KBr) cm-1 3566 (OH), 2992 (C-H), 1649 (C=N),
1
1586 (C=C), 1178 (C=S), 784 (C-Cl) cm-1; H NMR
(DMSO-d6): d 3.74 (s, 2H, CH2), 6.56 (d, 2H, 2,6-ArH),
6.69 (d, 2H, 3,5-ArH), 7.23 (d, 2H, 2¢,6¢-ArH-Cl), 7.53 (d,
2H, 3¢,5¢-ArH-Cl), 9.32 (s, 1H, SH), 13.83 (s, 1H, OH); 13C
NMR (DMSO-d6): d 31.2, 115.5, 124.3, 129.5, 132.3,
135.3, 151.4, 156.5, 168.4; MS: m/z 317 (M+); Anal. Calcd
for C15H12ClN3OS: C, 56.69; H, 3.81; N, 13.22. Found: C,
56.60; H, 3.78; N, 13.25.
5-(4-Hydroxyphenyl)methyl-4-(4-methoxyphenyl)-3-
mercapto-1,2,4(H)-triazole (5h)
IR: (KBr) cm-1 3568 (OH), 2991 (C-H), 1631 (C=N),
1
1589 (C=C), 1163 (C=S) cm-1; H NMR (DMSO-d6): d
3.69 (s, 2H, CH2), 3.80 (s, 3H, OCH3), 6.57 (d, 2H, 2,6-
ArH), 6.69 (d, 2H, 3,5-ArH), 6.99 (d, 2H, 2¢,6¢-ArH-
OCH3), 7.09 (d, 2H, 3¢,5¢-ArH-OCH3), 9.29 (s, 1H, SH),
13.25 (bs, 1H, OH); 13C NMR (DMSO-d6): d 30.6, 55.4,
114.3, 115.2, 124.6, 126.2, 129.5, 151.9, 156.2, 159.6,
168.1; MS: m/z 313 (M+); Anal. Calcd for C16H15N3O2S: C,
61.33; H, 4.82; N, 13.41. Found: C, 61.36; H, 4.89; N, 13.39.
5-(4-Hydroxyphenyl)methyl-4-(4-bromophenyl)-3-mer-
capto-1,2,4(H)-triazole (5d)
IR: (KBr) cm-1 3555 (OH), 2981 (C-H), 1657 (C=N),
1
1586 (C=C), 1186 (C=S) cm-1; H NMR (DMSO-d6): d
3.68 (s, 2H, CH2), 6.54 (d, 2H, 2,6-ArH), 6.68 (d, 2H, 3,5-
ArH), 7.21 (d, 2H, 2¢,6¢-ArH-Br), 7.50 (d, 2H, 3¢,5¢-ArH-
Br), 9.29 (s, 1H, SH), 13.70 (bs, 1H, OH); MS: m/z 362
(M+); Anal. Calcd for C15H12BrN3OS: C, 49.74; H, 3.34; N,
11.60. Found: C, 49.70; H, 3.29; N, 11.50.
5-(4-Hydroxyphenyl)methyl-4-n-butyl-3-mercapto-
1,2,4(H)-triazole (5i)
IR: (KBr) cm-1 3567 (OH), 2982 (C-H), 1629 (C=N),
1594 (C=C), 1174 (C=S) cm-1; 1H NMR (DMSO-d6): d 0.76
(t, J = 6.7 Hz, 3H, CH3), 1.16-1.27 (m, 4H, -CH2-CH2-),
3.20 (s, 2H, CH2), 3.74 (t, J = 6.9 Hz, 2H, N-CH2), 6.67 (d,
2H, 2,6-ArH), 7.02 (d, 2H, 3,5-ArH), 9.11 (s, 1H, SH),
13.55 (s, 1H, OH); 13C NMR (DMSO-d6): d 13.4, 19.2,
29.2, 30.0, 42.9, 114.9, 126.3, 129.6, 151.5, 155.8, 166.6;
MS: m/z 263 (M+); Anal. Calcd for C13H17N3OS: C, 59.29;
H, 6.51; N, 15.96. Found: C, 59.20; H, 6.59; N, 16.00.
5-(4-Hydroxyphenyl)methyl-4-(4-fluorophenyl)-3-mer-
capto-1,2,4(H)-triazole (5e)
IR: (KBr) cm-1 3545 (OH), 2986 (C-H), 1638 (C=N),
1596 (C=C), 1145 (C=S), 1090 (C-F); 1H NMR (DMSO-
d6): d 3.75 (s, 2H, CH2), 6.66 (d, 2H, 2,6-ArH), 6.76 (d, 2H,
3,5-ArH), 7.08 (d, 2H, 2¢,6¢-ArH-F), 7.21 (d, 2H, 3¢,5¢-
ArH-F), 9.99 (s, 1H, SH), 13.32 (bs, 1H, OH); MS: m/z 301
(M+); Anal. Calcd for C15H12FN3OS: C, 59.79; H, 4.01; N,
13.94. Found: C, 59.81; H, 4.00; N, 14.01.
Biological Studies
Adult male Wistar strain rats of either sex, weighing

208 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Amir et al.
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and water ad libitum. They were housed in a room at 25
2
°C and 50 5% relative humidity with a 12 hr light/dark cy-
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beginning of all the experiments. All the test compounds
and the reference drugs were administered orally, sus-
pended in 0.5% carboxymethyl cellulose (CMC) solution.
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ACKNOWLEDGEMENTS
We thank Hamdard University for providing neces-
sary facilities. We also thank IIT Delhi, CDRI Lucknow
and RRL Jammu for spectral analysis of the compounds.
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Received March 14, 2007.
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