Synthesis and Antimicrobial Evaluation of 1,3,4-Oxadiazole-2-thione from Some Pyridine Carboxylic Acids

Abstract

The 5-(2-pyridyl)-1,3,4-oxadiazole-2-thione (

) and the bis-5-(2,6-pyridyl)-1,3,4-oxadiazole-2-thione (4b) have been synthesized from the corresponding 2-pyridine carboxylic acid (picolinic acid) (1a) and 2,5-pyridine dicarboxylic acid (1b) by similar method. The esterification of the acids with ethyl and methyl alcohols gave the corresponding esters 2a and 2b. The hydrazides 3a and 3b were obtained in good yields. The 1,3,4-oxadiazoles 4a and 4b were formed by treatment of the corres-ponding hydrazides with CS2 and KOH. The intermediates and the final products were characterized with IR, UV, 1H and 13C NMR and MS. The hydrazides 3a and 3b, the final products and the commercially available 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (5) were tested in vitro against the following micro organisms: Escherichia coli ATCC 25924, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATTC 29212, Staphylococcus aureus ATCC 25923 and Pseudomonas fluorescens ATCC 17552 and compared with the known antibiotics Cephalosporin (cefotaxim) and Gentamycin. The results have shown that the synthesized compounds have appreciable effects. The bis-5-(2,6-pyridyl)-1,3,4-oxadiazole-2-thione (4b) had the highest effect upon all the tested microorganisms in general and on the gramnegative bacteria Pseudomonas fluorescens in particular, where its effect exceeded that of the well known Cephalosporin (cefotaxim).