Synthesis, crystal structure and antimycobacterial activities of 4-indolyl-1,4-dihydropyridine derivatives possessing various ester groups

The present study reports the synthesis of a series of alkyl 4-(5/6-bromo-1H-indole-3-yl)-2,6,6/2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate derivatives by a simple, rapid and convenient modified Hantzsch condensation reaction under microwave irradiation. The structure elucidation of the target compounds was carried out by different spectral techniques including IR, H-1-NMR, COSY, C-13-NMR, and mass analysis. Additionally, the proposed structure of compound 3 was proved by single crystal X-ray analysis. In vitro anti-tubercular activity of the compounds was evaluated against Mycobacterium tuberculosis H(37)Rv. The obtained results indicated that some compounds exhibited moderate antimycobacterial activity with weak cytotoxicity. Among them, compounds carrying ethyl or isopropyl groups in their ester moiety were found to be the most active compounds in this series. Molecular modeling studies were carried out to gain an idea about the mechanism of action of the active compounds. According to the results, the interactions were found quite similar with the co-crystalized ligand of M. tuberculosis enoyl reductase (InhA).