Synthesis and Microbiological Activity of Some Substituted N-(2−hydroxy-4-nitrophenyl)benzamides and Phenylacetamides as Possible Metabolites of Antimicrobial Active Benzoxazoles

Some new antimicrobial active N-(2−hydroxy-4-nitrophenyl)-p-substituted benzamide and phenylac-etamide analogues (I-II) were prepared by 2-step procedures from the corresponding carboxylic acids as possible metabolites of benzoxazoles. Their antimicrobial activities were tested against 3 Gram-positive and 2 Gram-negative bacteria with the fungus Candida albicans and were also compared with several control drugs. The compounds Ia, Id, IIa, and IIe were active at a MIC value of 12.5 g/mL against the Gram-positive microorganism Bacillus subtilis. Most of the compounds exhibited antifungal activity at a MIC value of 12.5 g/mL against C. albicans. On the other hand, the antimicrobial activity of some amide derivatives (Ia, Id, IIa-c) was also compared with their cyclic analogues, benzoxazole derivatives (III-IV). The compound Id signicantly possessed 2 or 3 dilutions better antimicrobial activity than its heterocyclic derivative, 2-(p-t-butylphenyl)-5-nitrobenzoxazole, IIId, against Staphylococcus aureus, Streptococcus faecalis, Klebsiella pneumonia, and Escherichia coli