Synthesis of Biologically Active Carbazoles

Carbazole and tetrahydrocarbazole ring systems are major artifacts of many naturally occurring biologically active compounds. There has been strong interest in carbazole alkaloids by chemists and biologist due to the intriguing structural features and promising biological activities. Diels-Alder reactions of 3-vinylindoles were carried out with methyl acrylate as dienophiles under microwave conditions to furnish the unreported tetrahydrocarbazoles, regio and stereoselectively in good yields. Further dehydrogenation resulted in new substituted carbazoles. Indolo[2, 3-a]pyrrolo[3, 4-c]carbazole alkaloids form a class of compounds endowed with potent antitumor, antiviral and antimicrobial activities. This family has raised considerable attention because of the central role of these molecules in the regulation of cell cycle progression and specific enzyme inhibition. The objective is to develop a methodology for the synthesis of biologically active derivatives of pentacyclic carbazole systems. The route involves simple reactions to get 2-vinylindoles by lithiation, deprotection and dehydration of protected indole and further [4+2] cycloaddition reactions.