Non-carboxylic analogues of naproxen: Design, synthesis, and pharmacological evaluation of some 1,3,4-oxadiazole/thiadiazole and 1,2,4-triazole derivatives

Article abstract of DOI:10.1002/ardp.200700065

A series of substituted 1,3,4-oxadiazole (2-7 and 14-19), 1,2,4-triazole (20-25), and 1,3,4-thiadiazole (26-31) derivatives of naproxen have been synthesized by cyclization of 2-(6-methoxy-2-naphthyl)propanoic acid hydrazide 1 and N¹[2-(6-methoxy-2-naphthyl) propanoyl]-N⁴-alkyl/aryl- thiosemicarbazides (8-13) under various reaction conditions. All the compounds were screened for their anti-inflammatory activity by carrageenan-induced rat paw edema test method. Compounds showing high anti-inflammatory activity were also tested for their analgesic, ulcerogenic, and lipid peroxidation. Few of the synthesized compounds showed significant anti-inflammatory and analgesic activities along with reduced ulcerogenic effect and lipid peroxidation.

Full text of DOI:10.1002/ardp.200700065

Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
M. Amir et al.
577
Full Paper
Non-carboxylic Analogues of Naproxen: Design, Synthesis,
and Pharmacological Evaluation of some 1,3,4-Oxadiazole/
Thiadiazole and 1,2,4-Triazole Derivatives
Mohammad Amir, Harish Kumar, and Sadique A. Javed
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Hamdard University, New Delhi, India
A series of substituted 1,3,4-oxadiazole (2–7 and 14–19), 1,2,4-triazole (20–25), and 1,3,4-thiadia-
zole (26–31) derivatives of naproxen have been synthesized by cyclization of 2-(6-methoxy-2-
naphthyl)propanoic acid hydrazide 1 and N1[2-(6-methoxy-2-naphthyl) propanoyl]-N4-alkyl/aryl-
thiosemicarbazides (8–13) under various reaction conditions. All the compounds were screened
for their anti-inflammatory activity by carrageenan-induced rat paw edema test method. Com-
pounds showing high anti-inflammatory activity were also tested for their analgesic, ulcero-
genic, and lipid peroxidation. Few of the synthesized compounds showed significant anti-inflam-
matory and analgesic activities along with reduced ulcerogenic effect and lipid peroxidation.
Keywords: Anti-inflammatory / Naproxen / 1,3,4-Oxadiazoles / Thiadiazoles / 1,2,4-Triazoles /
Received: March 27, 2007; accepted: July 24, 2007
DOI 10.1002/ardp.200700065
COX-1 and subsequently its gastric cytoprotective role.
Recently, it was discovered that COX exist in two iso-
forms, COX-1 and COX-2, which are regulated differently
[6, 7]. COX-1 provides cytoprotection in the gastrointesti-
nal tract whereas inducible COX-2 mediates inflamma-
tion [8, 9]. Thus the discovery of COX-2 provided the
rationale for the development of drugs devoid of GI disor-
ders while retaining clinical efficacy as anti-inflamma-
tory agents. But the recent reports showed that selective
COX-2 inhibitors (coxibs) could lead to adverse cardiovas-
cular effects [10]. Therefore, development of novel com-
pounds having anti-inflammatory and analgesic activity
with an improved safety profile is still a necessity.
Synthetic approaches based upon NSAIDs chemical
modification have been taken with the aim of improving
their safety profile. The literature survey revealed that
derivatization of the carboxylate function of NSAIDs also
resulted in retained anti-inflammatory activity with
reduced ulcerogenic potential [11–14]. Furthermore, it
has been reported in the literature that certain com-
pounds bearing 1,3,4-oxadiazole/thiadiazole and 1,2,4-
triazole nucleus possess significant anti-inflammatory
activity [15–18]. In view of these observations and in con-
tinuation of our research program on the synthesis of 5-
membered heterocyclic compounds of aryl alkanoic acid
Introduction
The majority of non-steroidal anti-inflammatory drugs
(NSAIDs) act via inhibition of cyclooxygenase thus pre-
venting prostaglandin biosynthesis. However, this mech-
anism of action is also responsible for their main undesir-
able side effect, gastrointestinal (GI) ulceration and renal
injury [1]. The increase in hospitalization and deaths due
to GI-related disorders parallels the increased use of
NSAIDs [2]. Naproxen was one of the leading NSAIDs used
for relieving arthritic pain, but its long-term use invites
GI complications ranging from stomach irritation to life-
threatening GI ulceration and bleeding [3–5]. These clini-
cal shortcomings comprise a major challenge confront-
ing medicinal chemists to develop safer agents that spare
Correspondence: Dr. Mohammad Amir, Department of Pharmaceutical
Chemistry, Faculty of Pharmacy, Hamdard University, New Delhi-110
062, India.
E-mail: mamir_s2003@yahoo.co.in
Fax: +91 11 260 59688, Extn. 5307
Abbreviations: carboxymethyl cellulose (CMC); gastrointestinal (GI);
malondialdehyde (MDA); non-steroidal anti-inflammatory drugs
(NSAIDs); serum glutamate oxaloacetate transaminase (SGOT); serum
glutamate pyruvate transaminase (SGPT)
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Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Scheme 1. Synthetic pathways to 1,3,4-oxadiazole (2–7 and 14-19), 1,2,4-triazole (20–25) and 1,3,4-thia-
diazole (26–31) derivatives of naproxen.
derivatives [19–21], we report herein the synthesis of ing with 4N NaOH in ethanol underwent smooth cycliza-
some newer, more potent analogues of 2-(6-methoxy-2- tion through dehydration to afford 4-alkyl/aryl-5-[1-(6-
naphthyl)propanoic acid (naproxen) by cyclizing the car- methoxy-2-naphthyl)ethyl]-3-mercapto-(4H)-1,2,4-tria-
boxylic group into 1,3,4-oxadiazole, 1,2,4-triazole, and zoles 20–25. 5-[1-(6-Methoxy-2-naphthyl)ethyl]-2-alkyl/
1,3,4-thiadiazole nuclei, which have been found to pos- aryl amino-1,3,4-thiadiazoles 26–31 were obtained by
sess an interesting profile of anti-inflammatory and anal- cyclization of thiosemicarbazides 8–13 after treatment
gesic activity with significant reduction in their ulcero- with cold concentrated sulphuric acid (Scheme 1). The
genic effect.
purity of various synthesized compounds was checked by
TLC and elemental analysis. Spectral data (1H-NMR, IR,
and mass) of the synthesized compounds were in full
agreement with the proposed structures.
Results and discussion
Chemistry
Biological studies
2-(6-Methoxy-2-naphthyl)propanoic acid hydrazide 1 was The anti-inflammatory activity of the synthesized com-
prepared by esterfication of 2-(6-methoxy-2-naphthyl)pro- pounds 2–7, 14–29, and 31 was evaluated by carra-
panoic acid followed by treatment with hydrazine geenan-induced paw edema method of Winter et al. [23],
hydrate in absolute ethanol. Treatment of the hydrazide edema being measured after 3 and 4 h of carrageenan
1 with appropriate aromatic acids in phosphorous oxy- treatment. Also, it was observed that compounds 7, 15,
chloride afforded 5-[1-(6-methoxy-2-naphthyl)ethyl]-2-sub- 22, 25, and 28 showed anti-inflammatory activity 78.02%,
stituted-1,3,4-oxadiazoles 2–7. Furthermore, hydrazide 1 74.99%, 75.75%, 76.51%, and 74.99% after 3 h, which was
on treatment with alkyl/aryl isothiocyanates gave N1[2-(6- found to be greater than standard drug naproxen
methoxy-2-naphthyl)propanoyl]-N4-alkyl/aryl-thiosemi-
(74.23%). When the activity of these compounds was
carbazides 8–13. These thiosemicarbazides were oxida- measured after 4 h, only compound 22 showed activity
tively cyclized to 5-[1-(6-methoxy-2-naphthyl)ethyl]-2- equivalent to naproxen 81.81%. The rest of the com-
alkyl/aryl amino-1,3,4-oxadiazoles 14–19 by elimination pounds showed a lower activity. Since%-inhibition was
of H2S using iodine and potassium iodide in ethanolic found to be more after 4 h, this was made the basis of dis-
sodium hydroxide. The thiosemicarbazides 8–13 on heat- cussion. All the derivatives of naproxen tested showed
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Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Azole Derivatives of Naproxen
579
Table 1. Physical data of the synthesized compounds.
Table 1. Continued.
Com-
pound
R
Yield Mp.
Mol.
Formula
Mol.
Wt.
Com-
pound
R
Yield Mp.
Mol.
Formula
Mol.
Wt.
(%)
(8C)
(%)
(8C)
2
57
186
C21H18N2O2
330
20
21
76
176
C19H23N3OS
341
71
124
C21H18ClN3OS
396
3
4
76
66
198
C21H17ClN2O2
C21H17ClN2O2
364
364
22
23
70
69
210
144
C21H18BrN3OS
C21H18FN3OS
440
379
A300
5
6
59
68
246
178
C21H16Cl2N2O2
C22H18Cl2N2O3
399
429
24
25
66
67
220
186
C22H21N3OS
C23H23N3OS
375
389
7
8
66
58
254
150
C27H30N2O2
C19H25N3O2S
414
359
26
27
61
59
122
170
C19H23N3OS
341
396
9
67
69
148
144
C21H20ClN3O2S
C21H20BrN3O2S
413
458
C21H18ClN3OS
10
28
29
64
57
240
170
C21H18BrN3OS
C21H18FN3OS
440
379
11
12
57
54
162
184
C21H20FN3O2S
C22H23N3O2S
397
393
30
31
61
66
252
216
C22H21N3OS
C23H23N3OS
375
13
14
61
53
158
128
C23H25N3O2S
C19H23N3O2
407
325
389
Satisfactory analysis for CHN was obtained for all the com-
15
16
61
60
154
C21H18ClN3O2
C21H18BrN3O2
379
424
pounds with in l0.3% of the theoretical values.
anti-inflammatory activity ranging from 13.63 to 81.81%
at an equimolar oral dose relative to 30 mg/kg naproxen
after 4 h, whereas the standard drug naproxen showed
81.81% inhibition at the same oral dose (Table 2). The
1,3,4-oxadiazole derivative of naproxen 7 having 1-(4-iso-
butylphenyl)ethyl group at second position of the oxadia-
zole ring showed anti-inflammatory activity (81.05%)
almost equal to the standard drug naproxen. The replace-
ment of this group by 2,4-dichlorophenoxy methyl 6 and
4-chlorophenyl amino 15 groups resulted in a slight
decrease of activity (77.19% and 77.27%, respectively).
The introduction of 2-chlorophenyl 4, 4-chlorophenyl 3
A300
17
18
19
55
51
54
174
A300
136
C21H18FN3O2
C22H21N3O2
C23H23N3O2
363
359
373
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580
M. Amir et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Table 2. Anti-inflammatory activity of the synthesized compounds.
Compound
Anti-inflammatory activity %
Compound
Anti-inflammatory activity %
inhibition lSEMa)
inhibition lSEMa)
After 3h
After 4 h
After 3 h
After 4 h
2
3
4
5
6
7
14
15
26.51 l 3.60
53.78 l 3.60
62.11 l 2.80
49.24 l 1.40
73.48 l 2.16
78.02 l 3.60
45.45 l 3.52
74.99 l 3.27
11.36 l 1.94
44.69 l 3.60
52.27 l 2.81
74.23 l 3.03
29.54 l 3.05b)
55.29 l 3.97b)
62.11 l 2.80b)
51.51 l 0.96b)
77.19 l 2.37
81.05 l 3.60
46.96 l 3.45b)
77.27 l 2.35
13.63 l 1.66b)
49.24 l 3.20b)
55.30 l 2.73b)
81.81 l 2.65
19
20
21
22
23
24
25
26
27
28
29
31
47.72 l 1.95
18.93 l 3.20
52.26 l 2.56
75.75 l 2.25
33.33 l 4.18
17.42 l 4.30
76.51 l 2.17
71.20 l 2.53
29.54 l 3.85
74.99 l 2.56
20.45 l 3.47
38.63 l 4.02
52.28 l 2.81b)
23.47 l 2.47b)
55.29 l 2.47b)
81.81 l 2.04
36.36 l 4.84b)
18.94 l 3.79b)
79.54 l 1.95
74.99 l 1.94
32.57 l 3.97b)
78.02 l 1.82
24.23 l 3.65b)
41.66 l 4.30b)
16
17
18
Naproxen
a)
Relative to the standard; the data was analyzed by ANOVA followed by dunnett's multiple comparision test for n = 6.
p a 0.01.
b)
and 2,4-dichlorophenyl 5 groups at position two of the that the triazole derivative of naproxen 22, having a 4-
oxadiazole ring resulted in further decrease of activity bromophenyl group at the 4th position of triazole ring,
(62.11%, 55.29%, and 51.51%, respectively). Replacement having maximum anti-inflammatory activity also
of these groups by phenyl 2 and 4-bromophenyl amino showed maximum analgesic effect 86.6%, which is more
16 groups resulted in sharp decrease of activity (29.54% than the standard drug naproxen (73.5%). The oxadiazole
and 13.63%, respectively).
derivatives 6 and 15 showed good analgesic activity
1,2,4-Triazole derivatives of naproxen showed anti- (58.7% and 57.6%, respectively). The rest of the com-
inflammatory activity ranging from 18.94 to 81.81%. The pounds showed moderate to weak analgesic activity.
maximum reduction in paw edema 81.81% (equal to nap-
The compounds, which were screened for their analge-
roxen) was shown by compound 22 having a 4-bromo- sic effect, were further tested for their acute ulcerogenic-
phenyl group at position four of triazole ring. When this ity at an equimolar oral dose relative to 90 mg/kg nap-
group was replaced by the 2-methylphenyl group 24, a roxen. The ulcerogenic activity was carried out by the
sharp decrease in activity (18.94%) was observed, whereas method of Ciolli et al. [25]. Results showed that all the
replacement by 2,4-dimethylphenyl 25, resulted in an tested compounds exhibited reduction in the severity
only slight decrease in activity (79.54%). The other tria- index (Table 3) in comparison to the standard drug nap-
zole derivatives showed weak anti-inflammatory activity. roxen (severity index 2.250 l 0.11). The 1,3,4-thiadiazole
The cyclization of the carboxylic group of naproxen into derivative 28 having 4-bromophenyl amino group at the
the thiadiazole ring also showed good anti-inflammatory 2nd position of the thiadiazole ring showed minimum
activity ranging from 24.23% to 78.02%. Compound 28 ulcerogenicity (severity index 0.417 l 0.08), whereas tria-
having a 4-bromophenyl amino group at position two of zole derivative 25 and thiadiazole derivative 26 showed
the thiadiazole ring showed 78.02% inhibition in rat paw maximum severity index (0.833 l 0.17 and 0.833 l 0.25,
edema. The activity was found to be slightly decreased respectively). It was noted that triazole derivative 22
(74.99%) when this group was replaced by a n-butylamino which showed maximum anti-inflammatory and analge-
group 26. The other compounds showed moderate to sic activity also showed a very low severity index of 0.583
weak anti-inflammatory activity.
l 0.08 as compared to naproxen. In general, the tested
The compounds which showed A70% anti-inflamma- compounds showed a better GI safety profile compared
tory activity were further tested for their analgesic activ- to the reference drug.
ity at the same oral dose as the one used for the anti-
All the compounds screened for ulcerogenic activity
inflammatory activity. The analgesic activity was carried were also analyzed for lipid peroxidation [26]. Lipid per-
out by the tail immersion method [24] and results are pre- oxidation was measured as nanomol of malondialdehyde
sented as%-analgesia in Table 3. The analgesic activity of (MDA)/100 mg of gastric mucosa tissue. It has been
compounds 6, 7, 15, 22, 25, 26, and 28 was found to be in reported in the literature that compounds showing less
the range from 20.8 to 86.6%. It was interesting to note ulcerogenic activity also showed reduced MDA content, a
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Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Azole Derivatives of Naproxen
581
Table 3. Analgesic, ulcerogenic, and lipid peroxidation activity of selected compounds.
Compound
Analgesic activitya)
Ulcerogenic activity nmol MDA content
(Severity index lSEM)d) lSEM/100 mg tissued)
Pre-treatment normal Post-treatment after % Inhibition
0 h (s)
4 h (s)
6
7
15
22
25
26
28
1.05 l 0.070
1.11 l 0.119
1.25 l 0.208
1.28 l 0.149
1.54 l 0.164
1.46 l 0.078
1.28 l 0.157
1.17 l 0.086
–
1.67 l 0.113c)
1.66 l 0.197c)
1.97 l 0.193b)
2.40 l 0.154b)
1.86 l 0.166c)
2.07 l 0.077
1.91 l 0.059
2.03 l 0.039b)
–
58.7
50.2
57.6
86.6
20.8
41.8
48.9
73.5
–
0.750 l 0.17e)
0.583 l 0.08e)
0.500 l 0.00e)
0.583 l 0.08e)
0.833 l 0.17e)
0.833 l 0.25e)
0.417 l 0.08e)
2.250 l 0.11
0.00
5.53 l 0.34e)
5.45 l 0.47e)
4.78 l 0.21e)
5.43 l 0.45e)
5.54 l 0.37e)
5.80 l 0.46e)
4.70 l 0.29e)
9.04 l 0.24
3.25 l 0.05
Naproxen
Control
a)
Relative to normal; the data was analyzed by paired student's t-test for n = 6.
b)p a 0.0001.
c)p a 0.005.
d)
Relative to standard; the data was analyzed by ANOVA followed by dunnett's multiple comparision test for n = 6.
p a 0.01.
e)
Table 4. Effect of compounds on serum enzymes, total protein, and total albumin.
Compound
SGOT Units/mla)
SGPT Units/mla)
Alkaline
Total protein
(g/dL)a)
Total albumin
(g/dL)a)
Phophatasea)
Control
148.67 l 1.50
142.17 l 0.98b)
129.33 l 0.76b)
139.67 l 1.65b)
27.67 l 0.84
25.33 l 0.61
18.83 l 0.60b)
23.17 l 0.75b)
13.06 l 0.25
18.69 l 0.16b)
14.85 l 0.14b)
14.25 l 0.14b)
1.80 l 0.01
1.82 l 0.05
1.89 l 0.12
1.59 l 0.05
1.67 l 0.01
1.74 l 0.06
1.74 l 0.13
1.44 l 0.05
7
22
28
a)
Relative to control; the data was analyzed by ANOVA followed by dunnett's multiple comparison test, for n = 6.
p a 0.01.
b)
byproduct of lipid peroxidation. Naproxen (standard liver samples do not show any significant pathological
drug) showed maximum lipid peroxidation (9.04 l 0.24) changes in comparison to the control group (Fig. 1). No
whereas the control group showed 3.25 l 0.05. It was hepatocyte necrosis or degeneration was seen in any of
found that all cyclized derivatives showing less ulcero- the samples.
genic activity also showed reduction in lipid peroxida-
In conclusion, various oxadiazole, thiadiazole, and tri-
tion Table 3. Thus, these studies demonstrate that the azole derivatives of naproxen were prepared with the
synthesized compounds have inhibited the induction of objective of developing better anti-inflammatory mole-
gastric mucosal lesion.
cules with minimum ulcerogenic activity. It was interest-
The 1,3,4-oxadiazole, 1,2,4-triazole, and 1,3,4-thiadia- ing to note that seven cyclized compounds 6, 7, 15, 22, 25,
zole derivatives of naproxen 7, 22, and 28, respectively, 26, and 28 were found to have significant anti-inflamma-
showing potent anti-inflammatory activity with reduced tory activity. When these compounds were subjected to
ulcerogenicity and lipid peroxidation were further stud- analgesic activity by the tail immersion method in mice,
ied for their hepatotoxic effect. All the compounds were except 25, all compounds showed significant activity.
studied for their effect on biochemical parameters Compound 22 was found to have a higher analgesic activ-
(serum enzymes, total protein, and total albumin) [27–
ity (86.6%) than the standard drug naproxen (75.5%).
29] and histopathology of liver [30]. As shown in Table 4, These compounds were also tested for ulcerogenic activ-
activities of the liver enzymes serum glutamate oxaloace- ity and showed a significant reduction in the severity
tate transaminase (SGOT) and serum glutamate pyruvate index compared to the standard reference drug. From
transaminase (SGPT), alkaline phosphatase, and total pro- these studies, compound 22, 4-(4-bromophenyl)-5-[1-(6-
tein, total albumin almost remain the same with respect methoxy-2-naphthyl)ethyl]-3-mercapto-(4H)-1,2,4-triazole
to the control values. The histopathological studies of the has emerged as the lead compound, which showed maxi-
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582
M. Amir et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Figure 1. Histopathological studies of the liver.
mum anti-inflammatory and analgesic effects along with ogy, All India Institute of Medical Sciences (AIIMS), New Delhi,
reduction in ulcerogenic potential and lipid peroxida- for carrying out the histopathological studies.
tion Thus the series provided new opportunities for possi-
ble modification of pharmacophoric requirements and
future exploitations.
Experimental
The authors are thankful to the Head of the Department Phar-
Melting points were determined in open capillary tubes and are
maceutical Chemistry, for providing laboratory facilities and
to the Central Drug Research Institute (CDRI) for spectral anal-
ysis of the compounds. The authors are also thankful to Mrs.
Shaukat Shah, in charge of the animal house, for providing
Wistar rats, and Dr. A. Mukherjee, MD, Department of Pathol-
uncorrected. IR (KBr) spectra were recorded on a Nicolet 5PC
FTIR spectrometer (mmax in cm– 1) (Nicolet, Madison, WI, USA) and
1H-NMR spectra were recorded in CDCl3/DMSO-d6 on a Bruker
DRX-300 (300 MHz FT NMR) spectrometer (Bruker Bioscience,
Billerica, MA, USA) using TMS as internal reference (chemical
shift in d ppm). Mass spectra were recorded at Jeol SX-102 (FAB)
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Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Azole Derivatives of Naproxen
583
spectrometer (Jeol, Tokyo, Japan). Chemicals were purchased
from Merck Chemical Company,Gibbstown, NJ, USA), S. D. Fine
(India) and Qualigens (India). Ethyl-2-(6-methoxy-2-naphthyl)pro-
panoate was prepared by the procedure given in the literature
[22].
compound exhibited the molecular ion peak at m/z 458 [M+],
other important fragments were found at m/z 460 [M++2], 378,
245, 213, 185, 171.
1H-NMR (CDCl3) 11: 1.51 (d, J = 6.8 Hz, 3H, CH3); 3.82–3.90 (m,
4H, CH and OCH3); 7.01–7.90 (m, 10H, ArH); 9.65 (bs, 1H, ArNH);
9.87 (bs, 1H, CSNH); 10.31 (bs, 1H, CONH).
1H-NMR (CDCl3) 12: 1.39 (d, J = 6.8 Hz, 3H, CH3); 1.94 (s, 3H, o-
CH3); 3.60–3.70 (m, 4H, CH and OCH3); 6.79–7.56 (m, 10H, ArH);
8.36 (bs, 1H, ArNH); 9.03 (bs, 1H, CSNH); 9.42 (bs, 1H, CONH).
Mass spectra of the compound exhibited the molecular ion peak
at m/z 393 [M+], other important fragments were found at m/z
243, 213, 185, 171.
Chemistry
2-(6-Methoxy-2-naphthyl)propanoic acid hydrazide 1
To
a mixture of ethyl-2-(6-methoxy-2-naphthyl)propanoate
(0.01 mol) and hydrazine hydrate (0.05 mol), absolute ethanol
(50 mL) was added and it was refluxed for 24 h on a water bath.
The mixture was concentrated, cooled, and poured into crushed
ice. It was kept for 4–5 h at room temperature and the solid
mass separated out was filtered, dried, and recrystallized from
ethanol. Mp 948C; Yield 61%; 1H-NMR (CDCl3): 1.60 (d, J = 7.1 Hz,
3H, CH3); 3.66 (q, J = 7.1 Hz, 1H, CH); 3.92 (s, 3H, OCH3); 6.70 (s,
2H, NH2); 7.13–7.79 (m, 7H, 6-ArH and CONH).
General procedure for the synthesis of 5-[1-(6-methoxy-2-
naphthyl)ethyl]-2-alkly/arylamino-1,3,4-oxadiazoles 14–
19
A suspension of 8–13 (0.002 mol) in ethanol (50 mL) was dis-
solved in aqueous sodium hydroxide (5N) with cooling and stir-
ring resulting in the formation of a clear solution. To this, iodine
in potassium iodide solution (5%) was added dropwise with stir-
ring till the color of iodine persisted at room temperature. The
reaction mixture was then refluxed for 3–5 h on a water bath. It
was then concentrated, cooled, and the solid separated out was
filtered, dried, and recrystallized with ethanol. The IR spectra of
the compounds 14–19 showed bands at 3310–3190 (N-H);
General procedure for the synthesis of 5-[1-(6-methoxy-2-
naphthyl)ethyl]-2-substituted-1,3,4-oxadiazoles 2–7
2-(6-Methoxy-2-naphthyl)propanoic acid hydrazide 1 (0.001 mol)
and the appropriate aromatic acid (0.001 mol) were dissolved in
phosphorus oxychloride and refluxed for 4–6 h. The reaction
was slowly poured over crushed ice and kept overnight. Solid
thus separated out was filtered, treated with dilute NaOH,
washed with water, and recrystallized with ethanol.
2954–2929 (C-H); 1653–1612 (C=N) cm– 1
.
1H-NMR (CDCl3) 14: 0.71 (t, J = 6.9 Hz, 3H, CH3); 1.16–1.22 (m,
2H, CH3CH2); 1.55–1.62 (m, 2H, CH3CH2CH2); 1.73 (d, J = 6.9 Hz,
3H, CHCH3); 3.65 (t, J = 6.9 Hz, 2H, NCH2); 3.91 (s, 3H, OCH3); 4.15
(q, J = 6.9 Hz, 1H, CH); 7.12–7.70 (m, 7H, 6 ArH and NH). Mass
spectra of the compound exhibited the molecular ion peak at m/
z 325 [M+], other important fragments were found at m/z 310,
253, 213, 185, 171.
The IR spectra of the compounds 2–7 showed bands at 2953–
2929 (C-H); 1623–1600 (C=N) cm– 1
.
1H-NMR (CDCl3) 5: 1.67 (d, J = 7.0 Hz, 3H, CH3); 3.55 (s, 3H,
OCH3); 3.92 (q, J = 7.0 Hz, 1H, CH); 7.13–8.09 (m, 9H, ArH). Mass
spectra of the compound exhibited the molecular ion peak at m/
z 399 [M+], other important fragments were found at m/z 401
[M++2], 253, 213, 185, 171.
1H-NMR (CDCl3) 15: 1.80 (d, J = 7.0 Hz, 3H, CH3); 3.90 (s, 3H,
OCH3); 4.36 (q, J = 7.0 Hz, 1H, CH); 7.02–7.73 (m, 10H, ArH); 9.88
(bs, 1H, NH). 1H-NMR (CDCl3) 17: 1.80 (d, J = 6.9 Hz, 3H, CH3); 3.91
(s, 3H, OCH3); 4.36 (q, J = 6.9 Hz, 1H, CH); 6.93–7.72 (m, 10H,
ArH); 9.50 (bs, 1H, NH). Mass spectra of the compound exhibited
the molecular ion peak at m/z 363 (M+), other important frag-
ments were found at m/z 364 [M++1], 365 [M++2], 344, 253, 213,
185, 171.
1H-NMR (DMSO-d6) 6: 1.48 (d, J = 7.0 Hz, 3H, CH3); 3.87–3.93 (m,
4H, CH and OCH3); 4.70 (s, 2H, OCH2); 7.14–7.78 (m, 9H, ArH).
Mass spectra of the compound exhibited the molecular ion peak
at m/z 429 [M+], other important fragments were found at m/z
431 [M++2], 253, 213, 185, 171.
1H-NMR (DMSO-d6) 7: 0.97 [d, J = 6.5 Hz, 6H, (CH3)2]; 1.43 (d, J =
7.0 Hz, 3H, CH3); 1.52 (d, J = 7.0 Hz, 3H, CH3); 1.84-1.92 (m, 1H,
CHCH2); 2.47 (d, J = 7.0 Hz, 2H, CH2); 3.81-3.86 (m, 4H, CH &
OCH3); 3.94 (q, J = 7.0 Hz, 1H, CHCH3); 6.87–7.92 (m, 10H, ArH).
Mass spectra of the compound exhibited the molecular ion peak
at m/z 414 [M+], other important fragments were found at m/z
253, 213, 185, 171.
1H-NMR (CDCl3) 18: 1.79 (d, J = 7.0 Hz, 3H, CH3); 2.17 (s, 3H, o-
CH3); 3.91 (s, 3H, OCH3); 4.41 (q, J = 7.0 Hz, 1H, CH); 7.07–7.81 (m,
10H, ArH); 8.03 (bs, 1H, NH).
1H-NMR (CDCl3) 19: 1.79 (d, J = 7.1 Hz, 3H, CH3); 2.20 (s, 3H, o-
CH3); 2.29 (s, 3H, p-CH3); 3.91 (s, 3H, OCH3); 4.36 (q, J = 7.1 Hz, 1H,
CH); 6.96–7.73 (m, 9H, ArH); 8.03 (bs, 1H, NH). Mass spectra of
the compound exhibited the molecular ion peak at m/z 373 [M+],
other important fragments were found at m/z 374 [M++1], 358,
344, 253, 213, 185, 171.
General procedure for the synthesis of N1[2-(6-methoxy-
2-naphthyl)propanoyl]-N4-alkyl/aryl-thiosemicarbazides
8–13
A mixture of 2-(6-methoxy-2-naphthyl)propanoic acid hydrazide
1 (0.10 mol), alkyl/aryl isothiocyanate (0.10 mol) and ethanol
(50 mL) was refluxed for 2–8 h on a water bath. It was then con-
centrated, cooled, and kept overnight in the refrigerator. The
solid separated out was filtered, dried, and recrystallized with a
suitable solvent. The IR spectra of the compounds 8–13 showed
bands at 3316–3285 (N-H); 2955–2933 (C-H); 1683–1674 (C=O);
General procedure for the synthesis of 4-alkyl/aryl-5-[1-
(6-methoxy-2-naphthyl)ethyl]-3-mercapto-(4H)-1,2,4-
triazoles 20–25
A suspension of 8–13 (0.002 mol) in ethanol (50 mL) was dis-
solved in aqueous sodium hydroxide (4N), resulting in the for-
mation of a clear solution. The reaction mixture was refluxed
for 4–6 h on a water bath, concentrated, cooled, and filtered.
The pH of the filtrate was adjusted between 5–6 with acetic acid
and kept aside for 1–2 h. The solid separated out was filtered,
washed with water, dried, and recrystallized with ethanol. The
1108-1033 (C=S) cm– 1
.
1H-NMR (CDCl3) 10: 1.47 (d, J = 6.8 Hz, 3H, CH3); 3.86–3.94 (m,
4H, CH and OCH3); 7.13–7.79 (m, 10H, ArH); 9.60 (bs, 1H, ArNH);
9.71 (bs, 1H, CSNH); 10.17 (bs, 1H, CONH). Mass spectra of the
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M. Amir et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
IR spectra of the compounds 20–25 showed bands at 2950–2918
(C-H); 2786–2715 (S-H); 1638–1604 (C=N) cm– 1
They were housed in a room at 25 l 28C, and 50 l 5% relative
humidity with 12 h light/dark cycle. The animals were randomly
allocated into groups at the beginning of all the experiments.
All the test compounds and the reference drugs were adminis-
tered orally, suspended in 0.5% carboxymethyl cellulose (CMC)
solution.
.
1H-NMR (CDCl3) 20: 0.72 (t, J = 6.9 Hz, 3H, CH3); 1.16–1.25 (m,
4H, CH3CH2CH2); 1.72 (d, J = 6.9 Hz, 3H, CHCH3); 3.81-3.92 (m, 4H,
CH and OCH3); 4.15 (t, J = 6.9 Hz, 2H, NCH2); 7.12–7.73 (m, 6H,
ArH); 10.83 (bs, 1H, SH). Mass spectra of the compound exhibited
the molecular ion peak at m/z 341 [M+], other important frag-
ments were found at m/z 342 [M++1], 308, 285, 282, 185, 171.
1H-NMR (CDCl3) 21: 1.67 (d, J = 7.0 Hz, 3H, CH3); 3.81–3.92 (m,
4H, CH & OCH3); 6.81–7.61 (m, 10H, ArH); 11.79 (bs, 1H, SH).
Mass spectra of the compound exhibited the molecular ion peak
at m/z 396 [M+], other important fragments were found at m/z
398 [M++2], 363, 328, 302, 185, 171.
Anti-inflammatory activity
The synthesized compounds were evaluated for their anti-inflam-
matory activity using carrageenan-induced hind paw edema
method of Winter et al. [23]. The animals were randomly allocated
into groups of six animals each. One group was kept as control
and received only 0.5% CMC solution. Group II was kept as stand-
ard and received naproxen (30 mg/kg, p. o.). Carrageenan solution
(0.1% in sterile 0.9% NaCl solution) in a volume of 0.1 mL was
injected subcutaneously into the sub-plantar region of the right
hind paw of each rat 1 h after the administration of the test com-
pounds and standard drugs. The right hind paw volume was
measured before and after 3 and 4 h of carrageenan treatment by
means of a plethysmometer. The percent anti-inflammatory
activity was calculated according to the following formula.
1H-NMR (CDCl3) 22: 1.67 (d, J = 6.8 Hz, 3H, CH3); 3.84–3.92 (m,
4H, CH & OCH3); 6.74–7.62 (m, 10H, ArH); 11.27 (bs, 1H, SH).
Mass spectra of the compound exhibited the molecular ion peak
at m/z 440 [M+], other important fragments were found at m/z
441 [M++1], 442 [M++2], 407, 327, 301, 185, 171.
1H-NMR (CDCl3) 23: 1.67 (d, J = 7.0 Hz, 3H, CH3); 3.87–3.92 (m,
4H, CH and OCH3); 6.97–7.61 (m, 10H, ArH); 11.99 (bs, 1H, SH).
1H-NMR (CDCl3) 24: 1.69 (d, J = 7.1 Hz, 3H, CH3); 1.97 (s, 3H,
CH3); 3.84-3.90 (m, 4H, CH & OCH3); 6.88–7.82 (m, 10H, ArH);
10.90 (bs, 1H, SH). Mass spectra of the compound exhibited the
molecular ion peak at m/z 375 [M+], other important fragments
were found at m/z 342, 316, 302, 185, 171.
Percent anti-inflammatory activity = (Vc – Vt/Vc)6100
where Vt represents the mean increase in paw volume in rats
treated with test compounds and Vc represents the mean
increase in paw volume in the control group of rats.
1H-NMR (CDCl3) 25: 1.69 (d, J = 7.0 Hz, 3H, CH3); 2.14 (s, 3H, o-
CH3); 2.43 (s, 3H, p-CH3); 3.79–3.91 (m, 4H, CH and OCH3); 6.79–
7.68 (m, 9H, ArH); 11.62 (bs, 1H, SH). Mass spectra ofthe com-
pound exhibited the molecular ion peak at m/z 389 [M+], other
important fragments were found at m/z 356, 330, 185, 171.
Analgesic activity
Analgesic activity was evaluated by the tail immersion method
[24]. Swiss albino mice allocated into different groups consisting
of six animals in each of either sex, weighing 25–30 g were used
for the experiment. Analgesic activity was evaluated after oral
administration of the test compounds at an equimolar dose rela-
tive to 30 mg/kg naproxen. Test compounds and standard drugs
were administered orally as suspension in CMC solution in
water (0.5% w/v). The analgesic activity was assessed before and
after an 4 h interval of administration of the test compounds
and standard drugs. The lower 5 cm portion of the tail was gen-
tly immersed into thermostatically controlled water at 55 l
0.58C. The time (in seconds) for tail withdrawal from the water
was taken as the reaction time with a cut-off time of immersion,
set at 10 s for both controls as well as treated animals.
General procedure for the synthesis of 5-[1-(6-methoxy-
2-naphthyl)ethyl]-2-alkyl/aryl amino-1,3,4-thiadiazoles
26–31
The thiosemicarbazide 8–13 (0.001 mol) was added gradually
with stirring to cooled conc. sulphuric acid (10 mL) during
10 min. The mixture was further stirred for another 5 h in an ice
bath. It was then poured over crushed ice with stirring. The solid
separated out was filtered, washed with water, dried, and recrys-
tallized with ethanol. The IR spectra of the compounds 26–31
showed bands at 3369–3186 (N-H); 2934–2900 (C-H); 1626–
1606(C=N) cm– 1
.
1H-NMR (DMSO-d6) 26: 0.84 (t, J = 7.0 Hz, 3H, CH3); 1.30–1.35
(m, 2H, CH3CH2); 1.53–1.57 (m, 2H, CH3CH2CH2); 1.68 (d, J =
7.0 Hz, 3H, CHCH3); 3.28 (t, J = 6.9 Hz, 2H, NCH2); 3.83 (s, 3H,
OCH3); 4.59 (q, J = 7.0 Hz, 1H, CH); 7.19–7.85 (m, 6H, ArH); 8.22
(bs, 1H, NH).
Acute ulcerogenicity
Acute ulcerogenicity was determined according to Cioli et al.
[25]. The animals were allocated into different groups consisting
of six animals in each group. Ulcerogenic activity was evaluated
after oral administration of the test compounds at an equimolar
dose relative to 90 mg/kg naproxen. Control group received only
0.5% CMC solution. Food but not water was removed 24 h before
administration of the test compounds. After the drug treatment,
the rats were fed with normal a diet for 17 h and then sacrificed.
The stomach was removed and opened along the greater curva-
ture, washed with distilled water, and cleaned gently by dipping
in normal saline. The mucosal damage was examined by means
of a magnifying glass. For each stomach the mucosal damage
was assessed according to the following scoring system:
0.5: redness; 1.0: spot ulcers; 1.5: hemorrhagic streaks; 2.0:
ulcers A3 but F5; 3.0: ulcers A5. The mean score of each treated
group minus the mean score of the control group was regarded
as severity index of the gastric mucosal damage.
1H-NMR (CDCl3) 27: 1.82 (d, J = 7.0 Hz, 3H, CH3); 3.91 (s, 3H,
OCH3); 4.53 (q, J = 7.0 Hz, 1H, CH); 7.13–7.71 (m, 10H, ArH); 8.27
1
(bs, 1H, NH). H-NMR (DMSO-d6) 28: 1.72 (d, J = 6.5 Hz, 3H, CH3);
3.83 (s, 3H, OCH3); 4.63 (q, J = 7.0 Hz, 1H, CH); 7.16–7.68 (m, 10H,
ArH); 8.21 (bs, 1H, NH). Mass spectra of the compound exhibited
the molecular ion peak at m/z 440 [M+], other important frag-
ments were found at m/z 442 [M++2], 362, 243, 255, 185.
1H-NMR (DMSO-d6) 31: 1.72 (d, J = 7.0 Hz, 3H, CH3); 2.16 (s, 3H, o-
CH3); 2.23 (s, 3H, p-CH3); 3.82 (s, 3H, OCH3); 4.50 (q, J = 7.0 Hz, 1H,
CH); 7.05–7.87 (m, 9H, ArH); 8.21 (bs, 1H, NH).
Biological evaluation
Adult male Wistar strain rats of either sex, weighing 150–200 g
were used. The animals were allowed food and water ad libitum.
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Arch. Pharm. Chem. Life Sci. 2007, 340, 577–585
Azole Derivatives of Naproxen
585
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Lipid peroxidation
133.
Lipid peroxidation in the gastric mucosa was determined
according to the method of Ohkawa et al. [26]. After screening
for ulcerogenic activity, the gastric mucosa was scraped with
two glass slides, weighed (100 mg) and homogenized in 1.8 mL
of 1.15% ice cold KCl solution. The homogenate was supple-
mented with 0.2 mL of 8.1% sodium dodecyl sulphate (SDS),
1.5 mL of acetate buffer (pH 3.5), and 1.5 mL of 0.8% thiobarbitu-
ric acid (TBA). The mixture was heated at 958C for 60 min. After
cooling, the reactants were supplemented with 5 mL of a mix-
ture of n-butanol and pyridine (15 : 1 v/v), shaken vigorously for
1 min and centrifuged for 10 min at 4000 rpm. The supernatant
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1.566105 cm– 1 M– 1
.
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weighing 150–200 g. The animals were divided into four
groups, six rats in each. Group I was kept as control and receives
only vehicle (0.5% w/v solution of carboxymethylcellulose in
water), the other groups received test compounds at an equimo-
lar oral dose relative to 30 mg/kg naproxen in 0.5% w/v solution
of CMC in water once in a day for 15 days. After the treatment
(15 days) blood was obtained from all the groups of rats by punc-
turing the retro-orbital plexus. Blood samples were allowed to
clot for 45 min at room temperature and serum was separated
by centrifugation at 2500 rpm for 15 min and analyzed for vari-
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