An efficient synthesis and biological screening of benzofuran and benzo[d]isothiazole derivatives for Mycobacterium tuberculosis DNA GyrB inhibition

A series of twenty eight molecules of ethyl 5-(piperazin-1-yl)benzofuran-2-carboxylate and 3-(piperazin-1-yl)benzo[d]isothiazole were designed by molecular hybridization of thiazole aminopiperidine core and carbamide side chain in eight steps and were screened for their in vitro Mycobacterium smegmatis (MS) GyrB ATPase assay, Mycobacterium tuberculosis (MTB) DNA gyrase super coiling assay, antitubercular activity, cytotoxicity and protein-inhibitor interaction assay through differential scanning fluorimetry. Also the orientation and the ligand-protein interactions of the top hit molecules with MS DNA gyrase B subunit active site were investigated applying extra precision mode (XP) of Glide. Among the compounds studied, 4-(benzo[d]isothiazol-3-yl)-N-(4-chlorophenyl)piperazine-1-carboxamide (26) was found to be the most promising inhibitor with an MS GyrB IC50 of 1.77 +/- 0.23 mu M, 0.42 +/- 0.23 against MTB DNA gyrase, MTB MIC of 3.64 mu M, and was not cytotoxic in eukaryotic cells at 100 mu M. Moreover the interaction of protein-ligand complex was stable and showed a positive shift of 3.5 degrees C in differential scanning fluorimetric evaluations. (C) 2014 Elsevier Ltd. All rights reserved.