Synthesis and Biological Evaluation of New 3-Phenylthiazolidin-4-One and 3-Phenylthiazole Derivatives as Antimicrobial Agents

A new series of 3-phenylthiazolidin-4-ones <b>4a-h</b> and 3-phenylthiazoles <b>6a-i</b> were synthesized from the reaction of different 4-phenyl-3-thiosemicarbazone derivatives <b>3a-i</b> with dimethyl acetylenedicarboxylate and 4-bromophenacyl bromide, respectively. Preparation of 3-phenylthiazoles <b>6a-i</b> starting from 4-bromophenacyl bromide could be achieved through two pathways either directly or indirectly in which new intermediates <b>5a-i</b> were isolated. The <i>in vitro</i> antibacterial activities of the newly synthesized compounds were tested versus two panels of Gram-positive bacteria; (<i>Staphylococcus aureus</i>, <i>Bacillus subtilis</i>) and Gram-negative bacteria (<i>Escherichia coli</i>, <i>Pseudomonas aeuroginosa</i>). Also, these compounds were tested for their activities as anti-fungal versus a panel of two fungi (<i>Aspergillus flavus</i>, <i>Candida albicans</i>). Compounds <b>4d, 6a, 6d,</b> and <b>6f</b> showed excellent antimicrobial activity exceeded 90%. Compound <b>6d</b> had equivalent potency to Ampicillin in inhibiting the growth of (<i>Bacillus subtilis</i>) bacteria (% activity index= 100%). Most of the rest of compounds showed good antimicrobial activity (70–90%).