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.

A quantitative structure-activity relationship (QSAR) study on a few series of potent, highly selective inhibitors of nitric oxide synthase.

QSAR study was performed on a series of 1,2-dihydro-4-quinazolinamines, 4,5-dialkylsubstituted-2-imino-1,3-thiazolidine derivatives and 4,5-disubstituted-1,3-oxazolidin-2-imine derivatives studied by Tinker et al. [J Med Chem (2003), 46, 913-916], Ueda et al. [Bioorg Med Chem (2004) 12, 4101-4116] and Ueda et al. [Bioorg Med Chem Lett (2004) 14, 313-316], respectively, as potent, highly selective inhibitors of inducible nitric oxide synthase (iNOS). The iNOS inhibition activity of the whole series of compounds was analyzed in relation to the physicochemical and molecular properties of the compounds. The QSAR analysis revealed that the inhibition potency of the compounds was controlled by a topological parameter 1v (Kier’s first order valence molecular connectivity index), density (D), surface tension (St) and length (steric parameter) of a substituent. This suggested that the drug-receptor interaction predominantly involved the dispersion interaction, but the bulky molecule would face steric problem because of which the molecule may not completely fit in active sites of the receptor and thus may not have the optimum interaction.

Synthesis, Characterization and Screening of Anti-tubercular activity of 2, 5-Disubstituted-1, 3, 4-Oxadiazole.

The synthesis of 2-furyl-5-(substituted)-1,3,4-oxadiazoles was carried out by microwave irradiation of 2-furoic acid and ethanol followed by subsequent hydrazinolysis with hydrazine hydrate. Finally furan-2-acid hydrazide was treated with appropriate carboxylic acid in the presence of phosphorous oxychloride to produce title compounds. The structures of the newly synthesized compounds were established on the basis of spectral analysis such as IR, H1NMR and Mass spectral data. The synthesized compounds were screened for their anti-tubercular activity.