Natural product leads for drug discovery: isolation, synthesis and biological evaluation of 6-cyano-5-methoxyindolo[2,3-a]carbazole based ligands as antibacterial agents.

Indolo[2,3-a]carbazole based inhibitors were synthesized from readily available indigo via a seven-step linear synthetic sequence with a moderate overall yield. The inhibitors were selectively and readily functionalized at the nitrogen on the indole portion of the carbazole unit. The synthesized analogs displayed moderate inhibitory activities toward Bacillus anthracis and Mycobacterium tuberculosis, indicating that indolo[2,3-a]carbazoles could serve as promising leads in the development of new drugs to combat anthrax and tuberculosis infections.