Synthesis and Antimicrobial Activity Evaluation of Novel 4-Thiazolidinones Containing a Pyrone Moiety

<div><p></p><p>A series of thiosemicarbazones <b>3a–d</b> and 4-thiazolidinones <b>5a–d, 7a–d,</b> and <b>9a–h</b> were synthesized and evaluated for their in vitro antimicrobial activity. Condensation of 3-acetyl-4-hydroxy-6-methyl-2<i>H</i> pyran-2-one<b>1</b> (dehydroacetic acid) with thiosemicarbazide <b>2a–d</b> in ethanol at room temperature yielded the thiosemicarbazones <b>3a–d</b>. These compounds were exploited to synthesize the 4-thiazolidinones <b>5a–d</b> via their reactions with ethyl 2-bromo propionate<b>4</b>. Derivatives <b>7a–d</b> were prepared by reaction of the thiosemicarbazones <b>3a–d</b> with phenyl bromoacetate <b>6</b>. The 4-thiazolidinones <b>9a–h</b> were obtained by treatment of compound <b>3a</b> or <b>3c</b> with maleimide derivatives <b>8a–d</b> in refluxing ethanol, under sulfuric acid catalysis. All compounds were screened in vitro for their antibacterial and antifungal activities against five human pathogens microorganisms: <i>Escherichia coli</i> ATCC 25992, <i>Pseudomonas aeruginosa</i> ATCC 27852, <i>Staphylococcus aureus</i> ATCC 43300<i>, Staphylococcus aureus</i> ATCC 25923, and <i>Candida albicans.</i></p>