New 2-benzylsulfanyl-nicotinic acid based 1,3,4-oxadiazoles: their synthesis and biological evaluation.

A novel series of 5-(2-benzylsulfanyl-pyridin-3-yl)-2-(substituted)-sulfanyl-1,3,4-oxadiazoles 6a-j were synthesized from key intermediate 5-(2-benzylsulfanyl-pyridin-3-yl)-3H-[1,3,4]oxadiazole-2-thione 5. Nucleophilic substitution reactions with different electrophiles (E+), such as haloacetate and haloalkyl groups, were performed to get target compounds 6a-j. Compounds were characterized by NMR, mass, IR spectra and C, H, N analyses. All compounds were evaluated for their antimicrobial and antimycobacterial activities; selected analogs were screened for their anticancer activity on 60 tumor cell lines at single dose 1.00(-5) M. Unfortunately, none of the compounds showed a significant antitumor activity on 60 human tumor cell lines. However, compounds 6g and 6f with benzothiazole moiety (12.5 and 25 μg/ml) showed promising activity against Escherichia coli compared to ampicillin; compounds 6d, 6j bearing triazole and morpholine, respectively, showed promising antitubercular activity (25 μg/ml) compared to rifampicin.