Metalated Heterocycles in the Synthesis of Ellipticine Analogues. A New Route to the 10H-Pyridocarbazole Ring System

Article abstract of DOI:10.1021/jo00275a008

A synthesis of the 10H-pyrido<2,3-b>carbazole ring system is described, in which the key steps are regiospecific acylation of a 2-lithio-1-(phenylsulfonyl)indole (7) with 2,3-pyridinedicarboxylic anhydride (8), cyclization of the deprotected keto acid 10 to keto lactam 11 with acetic anhydride, and the addition of methyllithium to give, after reduction of the diol 12 with sodium borohydride, the target ring system.In this fashion, 5,11-dimethyl-10H-pyrido<2,3-b>carbazole (3) and the corresponding 7-methoxy (4) and 8-methoxy (5) derivatives were synthesized.