Synthesis and antibacterial activities of 1,3,4-oxadiazole derivatives containing 5-methylisoxazole moiety

5-(5-Methylisoxazol-3-yl)-4-substituted aminomethyl-2-thio-1,3,4-oxadiazoles 3a-e and 4-acetyl-2-(5-methylisoxazol-3-yl)-5-substituted-1,3,4-oxadiazoles 5a-c have been synthesized by Mannich reaction of 5-(5-methylisoxazol-3-yl)-1,3,4-oxadiazol-2-thiol 2 with amines and cyclization of hydrazones with acetic anhydride, respectively. Moreover, 2-aryl-5-(5-methylisoxazol-3-yl)-1,3,4-oxadiazoles 6a-c have been obtained by direct condensation of 5-methylisoxazol-3-acetic acid hydrazizide with aromatic acid in the presence of POCl₃. The compounds synthesized have been confirmed by their elemental analyses and spectral data. Their antibacterial activities have also been evaluated.