Synthesis, X-ray crystallographic study, pharmacology and docking of hydrazinyl thiazolyl coumarins as dengue virus NS2B/NS3 serine protease inhibitors

A series of total twenty-one thiazole-coumarin derivatives 7a-u, linked via hydrazine linkage were synthesized through Hantzsch cyclisation. Out of twenty-one derivatives, fourteen derivatives viz. 7b-d, 7g, 7i-k, 7n and 7p-u are the novel derivatives. The structures of the synthesized compounds were established by extensive spectroscopic studies (FTIR, H-1 NMR, C-13 NMR, 2D NMR, LC-MS) and elemental analysis. The structure of (E)-6-methoxy-3-(1-(2-(4-p-tolylthiazol-2-yl)hydrazono)ethyl)-2H-chromen-2-one (7d) was unambiguously confirmed by X-ray crystallography analysis. Hybrid molecules were evaluated for their potential as anti-tubercular agents against Mycobacterium tuberculosis H37Rv ATCC 25618, and anti-bacterial agents against Eschericia coli, Enterobacter aerogenes, Salmonella typhi, Streptococcus pneumoniae and Staphylococcus aureus. All the compounds displayed considerable potency against all the pathogens with MIC values ranging from 31.25 to 250 mu g/mL, therein compounds 7i, 7j, 7k, 7q and 7t displayed superior inhibitory activities compared to standard drugs streptomycin, kanamycin, vancomycin and isoniazid. Molecular docking studies were performed to check the potential as dengue virus NS2B/NS3 serine protease inhibitors, by comparing to standards 4-hydroxypanduratin, panduratin and ethyl 3-(4-(hydroxymethyl)-2-methoxy-5-nitrophenoxy)propanoate with DS of -3.379, -3.189 and -3.381, respectively. All the compounds were found to exhibit potency against the DENV virus. In particular, compound 7c (DS -5.141) and 7l (DS -3.894) were found to be even better than the standards followed by compounds 7j (DS -3.113) and 7q (DS -3.561).