Synthesis and antimicrobial activity of some novel 2,5- and/or 6-substituted benzoxazole and benzimidazole derivatives

A new series of 2,5- and/or 6-substituted benzoxazoles (7a-f), benzimidazol es (8a-g) holding cyclohexyl or cyclopentyl moieties at position 2 and 5- o r 6-substituted-2-cyclohexylaminomethylbenzoxazoles (9a, b) was synthesized in order to determine their antimicrobial activities and feasible structur e-activity relationships. The synthesized compounds were tested in vitro ag ainst three Gram-positive, two Gram-negative bacteria and the yeast Candida albicans in comparison with several control drugs. Microbiological results showed that the synthesized compounds were possessing a broad spectrum of antibacterial activity against the tested microorganisms. 5-Chloro-2-(2-cyc lohexylethyl)benzimidazole (8g) was found as the most active compound again st the screened Gram-positive bacteria strains at a minimum inhibitory conc entration (MIC) value of 12.5 mu g/ml. However, it exhibited lower antibact erial potency than the compared control drugs. On the other side, compounds 7-9 indicated significant antibacterial activity against the Gram-negative enterobacter Pseudomonas aeruginosa having MIC values of 50 mu g/ml, provi ding either the same effect as tetracycline or higher activity than strepto mpcin, but showing less potency than the compared control drug gentamycin. Moreover, the synthesized compounds also possessed antimycotic activity aga inst the yeast C. albicans showing MIC values between 25-50 mu g/ml. (C) 19 98 Elsevier Science B.V. All rights reserved.