Construction of Hexahydropyrido[3,2‐c]carbazole and Hexahydropyrrolo[3,2‐c]carbazole Skeletons for the Synthesis of Related Indole Alkaloids

Abstract

Synthesis of tetracyclic hexahydropyrido[3,2‐c]carbazoles (9a and 9b) and hexahydropyrrolo[3,2‐c]carbazoles (13a and 13b) structures was achieved via a new synthetic approach for the synthesis of related indole alkaloids such as deethylaspidospermidine and deethylibophyllidine. Hexahydropyrrolo[3,2‐c]carbazole structure was constructed for the first time starting from ethyl 4‐oxo‐cyclohexanecarboxylate in seven steps. Some tetrahydrocarbazole derivatives (4, 5, 6, 7, 11, and 12) were also synthesized.