3H-[1,2]Dithiolo[3,4-b]pyridine-3-thione and Its Derivatives. Synthesis and Antimicrobial Activity.

A series of 2-substituted isothiazolo[5,4-b]pyridine-3(2H)-thiones, isothiazolo[5,4-b]pyridin-3(2H)-ones, N-substituted 2-sulfanylnicotinamides and the corresponding carbothioamide derivatives were synthesized and evaluated for their antimicrobial activity against several strains of Gram+ and Gram−bacteria and fungi. Chemical syntheses were resumed into a comprehensive cyclic route that enables the reversible conversion for each derivative of the series considered. Among the tested compounds the N-(aralkyl)-2-sulfanylnicotinamides show the highest fungitoxicity (MIC=1.25–5 μg/ml). The best activity towards Gram-positive bacteria was in the range of 2.5–5 μg/ml. Activity against Gram-negative bacteria was generally very poor for all compounds.