Synthesis and Biological Evaluation of Some New Coumarin Derivatives as Antimicrobial Agents

A series of new 7-[2-(3-alkyl/aryl-4-arylthiazol-2(3H)-ylidene)hydrazono)propoxy]-4methyl-2H-chromen-2-ones, (6-9a-e), was prepared by the reaction of appropriate N-alkyl/aryl2-[1-(4-methyl-2-oxo-2H-chromen-7yloxy)propan-2-ylidene]hydrazine carbothioamides (4a-d) and phenacyl bromides (5a-e). The purity of all new compounds was checked by TLC and elucidation of their structures was confirmed by IR, 1 H NMR, and mass spectrometry along with elemental microanalyses. All the target compounds were evaluated for their possible antimicrobial activity. Most of the tested compounds showed weak to moderate antibacterial activity against most of the bacterial strains used in comparison with gatifloxacin as a reference drug. The most active compounds were 6b, 6c, 7b, 8b, 8c, and 9c against B. cereus, E. coli and S. marcescens. Results of antifungal activity revealed that all compounds showed weak to moderate activity against S. brevicaulis, while ketoconazole as a reference drug was completely inactive. Compounds 6a, 6b, 6c, 6e and 7b were even more active than ketoconazole against F. oxysporum.