Design, synthesis and characterization of novel Benzothiazolyl pyrazoles as potential antitubercular scaffold

Abstract

The present study validates the synthesis of two new series of benzothiazole conjugated pyrazole analogs by the coupling of benzothiazole hydrazine with 4-formyl pyrazole derivatives, which was set up by Vilsmeier-Haack reaction. The synthetic approach was initiated by coupling different acetophenones and phenyl hydrazine to synthesize the Schiff's bases, which further undergo cyclization with Vilsmeier-Haack reagent followed by the imine formation. A singlet at 7.1 ppm in 1 H NMR indicated the protons of azo methane linkage (Schiff's base formation). Synthesized compounds were characterized by FT-IR, LC-MS, 1 H NMR and 13 C NMR spectroscopic techniques. The peak at 1593 cm −1 (>C=N-) indicated the formation of the azo methane linkage in the synthesized compounds. In 1 H NMR spectroscopy, a singlet peak at 8.89 ppm indicated the pyrazole proton, which confirmed the presence of 5-membered pyrazole ring.The recently synthesized compounds were screened for the anticancer and anti-tubercular (anti-TB) activities. MIC values of the compounds for in-vitro anti-TB activity were 1.6 μg/ml and MIC value of the compounds for in-vitro anti-cancer activities were 67.65 µg/ml and 70.31 µg/ml, against HELA and KB cell lines respectively. Most active compounds were found to be less toxic, which was determined by MTT assay method with normal cell line (L292). Biological screening of the synthesized series of compounds reveals that, Compound 5b was the potent molecule. .