Synthesis, antibacterial and analgesic activities of 4-[1-oxo-3-(substituted aryl)-2-propenyl]-3-(4-methylphenyl) sydnones

Article abstract of DOI:10.1155/2010/237473

A series of sydnone derivatives containing styryl ketone moiety, 4-[1-oxo-3-(substituted aryl)-2-propenyl]-3-(4-methylphenyl)sydnones (6a-i) has been synthesized and characterized by spectral data. The synthesized compounds have been screened for prelimin

Full text of DOI:10.1155/2010/237473

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2010, 7(1), 59-64
http://www.e-journals.net
Synthesis, Antibacterial and Analgesic
Activities of 4-[1-Oxo-3-(substituted aryl)-2-
propenyl]-3-(4-methylphenyl) sydnones
SHREENIVAS R. DESHPANDE* and K. VASANTAKUMAR PAI
*Department of Medicinal and Pharmaceutical Chemistry,
HSK College of Pharmacy, BVVS Campus, Bagalkote-587 101, Karnataka, India.
Department of Industrial Chemistry, Kuvempu University,
Jnana Sahyadri, Shankaraghatta-577 451, Shimoga Dist., Karnataka, India.
srinidesh@yahoo.com
Received 8 April 2009; Revised 23 May 2009; Accepted 20 July 2009
Abstract: A series of sydnone derivatives containing styryl ketone moiety,
4-[1-oxo-3-(substituted aryl)-2-propenyl]-3-(4-methylphenyl)sydnones (6a-i)
has been synthesized and characterized by spectral data. The synthesized
compounds have been screened for preliminary antibacterial activity by cup
plate method and analgesic activity by the method of acetic acid induced
writhing in mice. The chloro and nitro derivatives showed good antibacterial
activity against both gram positive and gram negative bacteria while the chloro
and furyl derivatives exhibited highest analgesic effect among the series.
Keywords: Synthesis, Sydnone, Styryl ketone, Antibacterial, Analgesic
Introduction
Sydnones are unique, dipolar heteroaromatic members of the general class mesoionic
compounds and chemically they are 1, 2, 3-oxadiazolium-5-olates1. A large number of
sydnone derivatives have been synthesized with biological interest2-5 and reported to possess
a wide spectrum of biological activities such as antiviral6, antimicrobial7, anti-
inflammatory8, analgesic8, anthelmintic8, antitumor9, free radical scavenging10 and nitric
oxide donor11 activities. The potential value of sydnones as biologically active substances is
found in their planar aromatic character, their relatively small size and variation in electron
density around the ring. It is thought that the ionic resonance structures of sydnones promote
significant interactions with biological molecules. Synthetic compounds containing styryl
ketone pharmacophore such as chalcones12, dehydrogingerone analogs13 and benzylidene
amino coumarins14 have been reported to exhibit analgesic and anti-inflammatory activities.

60
S R. DESHPANDE et al.
Prompted by these observations, we thought it worth to synthesize compounds containing
both sydnone and styryl ketone moieties in the same molecule with an intention of having good
biological activities. The present communication describes the synthesis, antibacterial and
analgesic activities of 4-[1-oxo-3- (substituted aryl)-2-propenyl]-3-(4-methylphenyl) sydnones.
Experimental
General
The chemicals used were of analytical reagent grade. Melting points were determined in an
open capillary and are uncorrected. IR spectra were recorded as KBr disc on Thermonicolet
1
200 FT-IR spectrometer. H NMR spectra in CDCl3 were obtained on Bruker AC 200 (200
Mhz) spectrometer using TMS as internal standard. Mass spectra were taken on Finnigan-
Mat 1020 instrument (i.e, 70 eV). The progress of reactions and the purity of products were
analyzed by thin layer chromatography (TLC).
Animals
Albino mice of either sex weighing between 20 and 25 g, maintained on standard diet, water
ad libitum were used and the usage of animals was approved and permitted by Institutional
Animal Ethics Committee (IAEC).
Statistics
The values expressed were mean SD of a triplicate result. Data were analyzed by one-way
ANOVA (analysis of variance) followed by Dunnett multiple comparison test using Graph-
Pad prism software. The results were considered significant at p<0.05.
Synthesis of N-nitroso (4-methylphenyl)glycine(3)
Ethyl chloroacetate (73 g, 49 mL, 0.6 mol), p-toluidine (53 g, 0.5 mol) and anhydrous
sodium acetate (50 g, 0.6 mol) in 120 mL of alcohol were refluxed for 6 h. The reaction
mixture was left overnight at room temperature and poured into ice cold water, a precipitate
of N- (4-methylphenyl)glycine ethyl ester (1) was obtained (84 g, 0.43 mol, 87%, m.p. 48-49 oC).
To 1 (84 g, 0.43 mol) sodium hydroxide (20 g, 0.5 mol) in 225 mL of water was added and
the mixture was refluxed for 0.5 h. After cooling, the reaction mixture was acidified to pH 2
using hydrochloric acid under cooling. The precipitated N-(4-methylphenyl) glycine (2) was
filtered and washed with cold water (14.5 g, 0.09 mol, 21%, m.p. 115-117 oC). A solution of
sodium nitrite (6.3 g, 0.09 mol) in water (20 mL) was added to 2 (14.5 g, 0.09 mol) in water
(60 mL) at 0 oC during 0.5 h. Further stirring for an additional 2 h resulted in a clear solution
which was acidified with hydrochloric acid. The precipitated 3 was washed with cold water,
dried (12.5 g, 0.06 mol, 67%, m.p. 102-104 oC) and recrystallised with methanol.
Synthesis of 3-(4-methylphenyl) sydnone (4)
Acetic anhydride (25 mL) was added to 3 (12.5 g, 0.06 mol). The reaction mixture was left
overnight at room temperature (18 h) and poured into cold water. The separated 4 was
filtered, dried (9 g, 0.05 mol, 83%) and recrystallised using alcohol. M.p 139-141 oC; IR, cm-1
1
1753 (C=O, sydnone), 3139 (C-4 of sydnone C-H stretch); H NMR, δ ppm 2.48 (s, 3H,
CH3), 6.67 (s, 1H, sydnone C-4H) 7.34-7.61 (m, 4H, Ar-H)
Synthesis of 4-acetyl-3-(4-methylphenyl)sydnone (5)
To a suspension of phosphorous pentoxide (21.3 g, 0.15 mol) in 125 mL of dried benzene, in
a two necked flask with a reflux condenser equipped with calcium chloride guard tube was

Synthesis, Antibacterial and Analgesic Activities
61
added 4 (8.9 g, 0.05 mol). The mixture was heated to reflux while being stirred. Glacial
acetic acid (2.9 mL, 0.05 mol) was added drop wise through a dropping funnel over a period
of 10 min. The stirred reaction mixture was heated for 5 h. After cooling to room
temperature, the benzene was decanted and the remaining black residue was extracted twice
with 20 mL benzene. Combined extract were evaporated to dryness to yield 5 (5.6 g, 0.025
o
mol, 51%) and it was recrystallised from aqueous alcohol. M.p 82-84 C; IR, cm-1 1759
1
(C=O, sydnone), 1668 (COCH3); H-NMR, δ ppm 2.50 (s, 3H, CH3), 2.56 (s, 3H, COCH3),
7.33-7.63 (m, 4H, Ar-H)
General procedure for synthesis of 6a-g
Synthesis of 4-[1-oxo-3-(3,4,5-trimethoxy phenyl)-2-propenyl]-3-(4-methylphenyl)
sydnone(6d)
A mixture of 5 (0.22 g, 0.001 mol), sodium hydroxide aqueous solution (0.06 g,
0
0.0015 mol, 0.3 mL) and ethanol (95%, 2 mL) was cooled (5-10 C) and to this was added
with 3,4,5-trimethoxybenzaldehyde (0.3 g, 0.0015 mol) while being stirred. The reaction
mixture was stirred further for 1 h. The precipitated 6d was filtered washed thoroughly with
cold water and recrystallised from ethanol (95%) and ethyl acetate (1:1) mixture, Yield 63%.
0
M.p. 116-118 C; IR, cm-1 1753 (C=O, sydnone), 1675 (C=O, styryl ketone); 1H NMR, δ ppm
2.46 (s, 3H, CH3), 3.92 (s, 9H, OCH3 ), 6.8 (d, 1H, α olefinic), 7.81 (d, 1H, β olefinic), 7.11-
7.6 (m, 6H, Ar-H). 6c: 1H NMR, δ ppm 2.49 (s, 3H, CH3), 6.76 (d, 1H, α olefinic), 7.39-7.63
(m, 9H, Ar-H and β olefinic) 6a: MS, m/z 306 (M+). Rests of the compounds were
synthesized in the similar fashion.
General procedure for Synthesis of 6h-i
Synthesis of 4-[1-oxo-3- (4-hydroxy-3-methoxyphenyl)-2-propenyl]-3-(4-methylphenyl)
sydnone (6h)
Into the suspension of 5 (0.22 g, 0.001 mol) and vanillin (0.15 g, 0.001 mol) in 2 mL of ethanol
0
(95%) dry hydrogen chloride gas was passed for 0.5 h under cooling condition (5 C). The
reaction mixture was left overnight at room temperature and poured into cold water. The
separated 6h was filtered, washed, dried in air and recrystallised from ethanol (95%).Yield 55%.
o
M.p 211-213 C; IR, cm-1 1760 (C=O, sydnone), 1649 (C=O, styryl ketone); 1H NMR, δ ppm
2.45 (s, 3H, CH3), 3.93 (s, 3H, OCH3), 7.0-7.7 (m, 9H, Ar-H and olefinic), 9.89 (s, 1H, OH).
Compound 6i was synthesized in the similar fashion.
Biological activity
The compounds 6a-i were screened for preliminary antibacterial activity by Cup Plate method15
at 10, 20 and 50 µg in DMSO against Staphylococcus aureus, Bacillus subtilis (Gram-positive)
and Escherichia coli, Salmonella typhi (Gram-negative) grown on nutrient agar medium and the
diameter of zone of inhibition was taken as a measure of antibacterial activity; norfloxacin at 20
µg concentration was employed as standard drug. The newly synthesized compounds were
tested for acute toxicity studies in mice16 and then screened for analgesic activity by acetic acid
induced writhing in mice17 at 100 mg/kg b.w.; aspirin at 100 mg/kg b.w. was used as standard
drug and percentage inhibition of writhes was calculated to assess the analgesic activity.
Results and Discussion
3-(4-Methylphenyl) sydnone (4) was prepared according to reported method18 wherein, 4-toluidine
was condensed with ethyl chloroacetate in presence of anhydrous sodium acetate to give
ethyl ester of N- (4-methylphenyl) glycine (1), which upon hydrolysis with sodium hydroxide

62
S R. DESHPANDE et al.
afforded N- (4-methylphenyl) glycine (2); this on nitrosation with sodium nitrite and
hydrochloric acid yielded N-nitroso-N- (4-methylphenyl) glycine (3). Thus obtained 3 was
cyclo-dehydrated using acetic anhydride to 4. Treatment of 4 with glacial acetic acid in
presence of phosphorous pentoxide19 afforded 4-acetyl 3-(4-methylphenyl) sydnone 5. The
compounds, 4-[1-oxo-(3-substituted aryl)-2-propenyl]-3-(4-methylphenyl)sydnones 6a-i
were synthesized employing Claisen-Schmidt reaction by treating 5 with different aryl
aldehydes in presence of either base or acid (Scheme 1). The physical data of compounds
6a-i are presented in Table 1.
CH3COONa
ClCH2COOC2H5
H3C
NHCH2COOC2H5
H3C
NH2
+
1
NaOH
NaNO2
(CH3CO)2O
H3C
NHCH2COOH
H3C
NCH2COOH
N
O
2
3
COCH3
CH3COOH / P2O5
H3C
N
N
OH- or H+
R-ArCHO /
H3C
N
N
+
+
O
O
O
O
4
5
COCH=CH-Ar-R
O
H3C
N
N
+
O
6a-i
Scheme-1
Table 1. Physical data and yields of 4-[1-oxo-3- (substituted aryl)-2-propenyl]- 3-(4-
methylphenyl) sydnones (6a-i).
Compd
Ar
R
H
Mol Formula Mol. Wt. Yield, % m.p, 0C
C18H14N2O3
C16H12N2O4
306
296
62
57
60
63
58
62
56
55
137-139
128-130
134-136
116-118
138-140
181-182
122-124
211-213
6a
H
6b
6c
6d
6e
6f
O
4-Cl
C18H13N2O3Cl 340.5
3,4,5-OCH3
4-NO2
C21H20N2O6
C18H13N3O5
C20H19N3O3
C18H13N3O5
396
351
349
351
352
4-N(CH3)2
2-NO2
6g
6h
4-OH, 3-OCH3 C19H16N2O5
2-OH
C21H15N3O4
373
61
241-242
6i
N

Synthesis, Antibacterial and Analgesic Activities
63
IR spectrum of 4 exhibited a strong band at 1753 cm-1 due to sydnone ketone and at
3139 cm-1 for C-4 of sydnone C-H stretch. The 1H NMR spectrum of 4 showed a singlet at δ
6.67 for H atom at C-4 of sydnone. The signals at δ 2.48 and δ 7.34-7.61 can be accounted
for methyl and aromatic protons respectively.
A band at 1668 cm-1 and absence of band at 3139 cm-1 exhibited by compound 5 in IR
spectrum confirmed the acetylation at C-4 sydnone. The 1H NMR spectrum of 5, showed the
signal at δ 2.53 and absence of signal at δ 6.67 confirming the acetyl protons at C-4 of
sydnone.
The IR spectra of 6a-i showed the bands due to C=O of sydnone and styryl ketone at
1
1753-1760 cm-1 and 1649-1675 cm-1 respectively. In H NMR spectra, these compounds
showed the doublets due to the protons attached to the carbon atoms of α, β unsaturated
ketone moiety at 7.2-7.8, but in most of the cases, were observed merging with aromatic
protons. The mass spectrum of 6a showed the M+ ion peak at m/e 306 confirming its
molecular weight.
All the compounds showed moderate antibacterial activity against both Gram-positive
and Gram-negative organisms at 10 and 20 µg cncentrations. At 50 µg, compounds 6c and
6e exhibited good activity against Staph. Aureus and B. subtilis, while 6c and 6i showed
good activity against E. coli and 6e and 6i possessed good activity against S. typhi.
Compounds having electron withdrawing substituents such as chloro and nitro at para
position, for example, 6c and 6e showed good activity against both Gram-positive and
Gram-negative organisms (Table 2).
Table 2. Antibacterial activity data of 6a-i.
Zone of Inhibition, mm
Compound
Staph. aureus
B. subtilis
E. coli
S. typhi
10 µg 20 µg 50 µg 10 µg 20 µg 50 µg 10 µg 20 µg 50 µg 10 µg 20 µg 50 µg
2
4
6
1
5
--
3
2
--
6
7
8
8
3
4
5
3
6
2
5
4
1
7
8
9
10
11
9
11
7
1
5
8
4
6
2
5
3
7
9
12
14
19
13
17
10
16
14
18
--
3
5
2
4
3
3
--
6
5
9
8
6a
6b
12
16
10
11
8
12
13
12
15
9
8
9
9
12
8
10
6
6c
6d
6e
5
7
7
10
5
6
9
4
5
6f
6g
7
8
9
10
9
10
9
8
13
11
15
7
7
8
6
6h
6i
3
12
6
5
14
8
13
21
10
17
Norfloxacin
No deaths were seen in acute toxicity study of 6a-i after 24 h of administration of doses
up to 1000 mg/kg b.w. But there were few changes in the behavioral response like alertness,
touch response and restlessness at 1000 mg/kg b.w. Therefore, 1/10th of the maximum
tolerated dose i.e., 100 mg/kg b.w. was chosen for the pharmacological studies.
Compounds 6a-6e and 6g showed highly significant analgesic activity (p<0.01) while 6f
and 6i showed significant activity (p<0.05) against control. Compounds 6b and 6c showed
highest activity among the series (Table 3). The presence of chloro group at para position of
the phenyl group that comes from aldehyde enhanced the activity. Trimethoxy group when
present on the phenyl ring sustained activity while N, N-dimethylamino group at para
position did not sustain the activity.

64
S R. DESHPANDE et al.
Table 3. Analgesic activity data of 6a-i.
Compound
Mean No. of
Writhes ( SD)
54 (06)
% Reduction
from Control ( SD)
25(01)**
36(02)**
35(02)**
26(04)**
28(01)**
18(00)*
6a
6b
46 (05)
47 (09)
6c
6d
53 (11)
52 (06)
6e
59 (07)
55 (05)
61 (10)
58 (08)
6f
6g
6h
6i
Aspirin
Control
24(02)**
15(03)
19(01)*
60(02)**
--
29 (09)
72 (07)
*p<0.05, **p<0.01
Conclusion
In the present work 4-[1-oxo-3- (substituted aryl)-2-propenyl]-3-(4-methylphenyl) sydnones
were conceived and synthesized with an augmented biological activity. The compounds
having electron-withdrawing substituents like chloro and nitro at para position exhibited
more antibacterial activity. The furyl and para chloro phenyl analogs showed good analgesic
activity. Thus, 3-(substituted phenyl)sydnone derivatives possessing substituted styrylketone
moieties appear to be another interesting source of antibacterial and analgesic compounds.
However, the difference in activity profile with structural modifications provides further
scope to explore the sydnones possessing stytyl ketone moiety for better bio-activity.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
Stewert F H C, Chem Rev., 1964, 64, 129.
Ollis W D and Ramsden C A, Adv Heterocycl Chem., 1976, 19, 1.
Kier L B and Roche E B, J Pharm Sci., 1967, 56, 149.
Ackermann E, Pharmazie, 1967, 22, 537.
Bos M and Leischhacker W F, Pharm Unserer Zeit., 1984, 13, 51.
Pandey V K, Mukesh and Tandon M, Indian J Heterocycl Chem., 2006, 15, 399.
Kavali J R and Badami B V, Il Farmaco, 2000, 55, 406.
Kalluraya B, Rahiman M A and Banji D, Indian J Chem., 2002, 41B, 1712.
Dunkley C S and Thoman C J, Bioorg Med Chem Lett., 2003, 13, 2899.
10. Mallur S G, Tiwari A K, Chinna Raju B, Suresh Babu K, Zehra Ali A, Sastry B S
and Madhusudana Rao J, Indian J Chem., 2007, 46B, 1686.
11. Satyanarayana K, Deshpande S R, Subbarao B and Rao M N A, Indian Drugs, 2002, 39, 578.
12. Elias G and Rao M N A, Eur J Med Chem., 1988, 23, 379.
13. Rao M N A, Naidoo L and Ramanan P N, Pharmazie, 1991, 46, 542.
14. Maddi V, Raghu K S and Rao M N A, J Pharm Sci., 1992, 81, 964.
15. Collins C H, Lyne P M and Grange J M, Collins and Lyne’s Microbiological
Methods, 7th Ed., Butterworth-Heinemann Ltd., Oxford, 1995, 178.
16. Dua P R, Testing of Natural Products for Acute Toxicity and CNS Activity; Central
Drug Research Institute: Lucknow, 1992, 26.
17. Anderson K R and de Beer E J M, Fed Proc., 1959, 18, 412 (Abstract No. 1626).
18. Earl J C and Mackney AW, J Chem Soc., 1935, 899.
19. Greco C V , Tobias J and Kier L B, J Heterocycl Chem., 1964, 4, 160.

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