Abstract
Purpose : To synthesize some acetamide derivatives bearing azinane and 1,3,4-oxadiazole heterocyclic cores and to evaluate their antibacterial potentials. Methods : Ethyl piperidin-4-carboxylate (2) was converted to ethyl 1-[(4-chlorophenyl)sulfonyl]piperidin- 4-carboxylate (3), 1-[(4-chlorophenyl)sulfonyl]piperidin-4-carbohydrazide (4) and 5-[1-(4- chlorophenylsulfonyl)-4-piperidinyl]-1,3,4-oxadiazol-2-thiol (5) using three consecutive steps. The target molecules, 5-{1-[(4-chlorophenyl)sulfonyl]piperidin-4-yl}-2-{[N-(substituted)-2-acetamoyl]thio]}-1,3,4- oxadiazole (8a-n) were synthesized by stirring 5 and N-aryl-2-bromoacetamides (7a-n) in an aprotic polar solvent. The structures were corroborated by infrared (IR), electron impact mass spectrometry (EIMS) and proton/carbon nuclear magnetic resonance (1H/13C-NMR) spectroscopic techniques. The evaluation of antibacterial activity was based on the effect on the increase in absorbance of the broth medium due to log phase microbial growth. Results : Compound 8g bearing a 2-methylphenyl group was the most the active growth inhibitor of Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa , Staphylococcus aureus and Bacillus subtilis bacterial strains with minimum inhibitory concentrations (MIC) of 10.63±0.97, 10.31±1.00, 10.45 ± 0.94 and 11.77±5.00 μM, respectively. Ciprofloxacin was used as reference standard. Conclusion : All the synthesized compounds are moderate inhibitors but relatively more active against Gram-negative bacterial strains. 5-{1-[(4- Chlorophenyl)sulfonyl]piperidin-4-yl}-2-{[N-(2-methylphenyl)-2- acetamoyl]thio]}-1,3,4-oxadiazole (8g) is the most active growth inhibitor of all the strains except Staphylococcus aureus. Keywords : 1,3,4-Oxadiazole, Acetamides, Antibacterial activity, Piperidine
Highlights
The search for new drug candidates with more bioactivity potential is a key research interest in synthetic organic chemistry [1]
Piperidine or azinane, is found to be a part of many natural and synthetic bioactive compounds [12]. This moiety has applications as food additives, solvents, curing agents for rubber and intermediates for inorganic synthesis [13,14]. These different bioactive heterocyclic moieties have been included as a single unit in target molecules with the aim of possibly enhancing their antibacterial potential
The molecular formula was well supported by electron impact mass spectrometry (EIMS) spectrum and the proton integration curves in 1H-NMR spectrum
Summary
The search for new drug candidates with more bioactivity potential is a key research interest in synthetic organic chemistry [1]. 1,3,4-oxadiazole derivatives have been synthesized and evaluated for a number of biological activities including antidepressant, anticonvulsant, anticancer, antimicrobial, etc., during the last two decades [2,3,4,5,6,7,8,9,10,11] Another bioactive heterocyclic moiety, piperidine or azinane, is found to be a part of many natural and synthetic bioactive compounds [12]. Piperidine or azinane, is found to be a part of many natural and synthetic bioactive compounds [12] This moiety has applications as food additives, solvents, curing agents for rubber and intermediates for inorganic synthesis [13,14]. Chilled distilled water was added to the reaction mixture to obtain the precipitate of compound 3.
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