1,5-Dimethyl-6H-pyridazino[4,5-b]carbazole, a 3-Aza Bioisoster of the Antitumor Alkaloid Olivacine

Abstract

A series of b-fused carbazoles structurally related to pyrido[4,3-b]carbazole-type alkaloids was prepared, utilizing the Diels–Alder reaction of 1-methylpyrano[3,4-b]indol-3(9H)-one with electron-deficient acetylenic dienophiles as the key step. The title compound (14) thus obtained in only four steps represents a new 3-aza analog of the antitumor natural product, olivacine.