Synthesis and antimicrobial evaluation of some new 3-alkyl-, 3-(2-naphthyl)isocoumarins and their (dl)-3,4 dihydroderivatives

Abstract

3-(Substituted)isocoumarins 3a-c are synthesized by the condensation of homophthalic acid 1 with acid chlorides 2a-c, which on alkaline hydrolysis give keto-acids 4a-c. (dl)-3-(Substituted)-3,4-dihydroisocoumarins 7a-c are obtained by the reduction of keto-acids 4a-c to racemic hydroxy-acids 6a-c followed by cyclodehydration using acetic anhydride. The compounds 3a-c, 4a-c, 5c and 7a-c are assayed for antifungal activity against T. longifusus, C. albicans, A. flavus, M. canis, F. solani and C. glaberata. Structure activity relationship reveals that the antifungal activity of naphthyl substituted isocoumarin is better than that of alkyl substituted isocomarins. Same compounds are also evaluated for in vitro antibacterial activity against different strains of gram-negative and gram-positive bacteria. Antifungal activities of 3c, 5c and 7c are found to be quite higher than the standard drugs against T. longifusus and A. flavus.