Synthesis, characterization, anti-mycobacterial activity and in silico study of new 2,5-disubstituted-1,3,4-oxadiazole derivatives.

A series of new 2,5-disubstituted-1,3,4-oxadiazole derivatives (5a-j and 6a-j) have been designed and synthesized in four-steps. Sixteen compounds among the twenty compounds are reported for the first time. The compounds were characterized and confirmed by the FTIR, 1D- and 2D-NMR and HRMS analyses, and were tested against Mycobacterium smegmatis and Mycobacterium tuberculosis H37Ra. Compound 5d was the most active against M. smegmatis with MIC value of 25 µM, and exhibited cidal activity with MBC of 68 µM, respectively. The time-kill assay showed the good killing rate at 77% with the combination of isoniazid (INH). In addition, checkboard assay confirmed the interaction of compound 5d was categorised as additive. Docking simulation has been performed to position 5d into the pantothenate synthetase active site with binding free energy value -8.6 kcal mol-1. It also occupied the same active site as that of standard native ligand with similar interactions, which clearly indicate their potential as pantothenate synthetase inhibitor.