Syntheses of functionalised pyrido[2,3-b]indoles

Abstract

Two complementary routes for the synthesis of highly functionalised pyrido[2,3-b]indolesare described, starting from the readily available 2-amino-3-cyano-1-(4-methoxybenzyl)tetrahydroindole and methyl 2-aminoindole-3-carboxylate, respectively. The use of methyl 3-methoxycrotonate for pyridine-ring annelation, and the application of the 4-methoxybenzyl moiety as a protecting group for the indole nitrogen, are key features in these high yielding routes. Further transformations of the derived pyrido[2,3-b]indoles are presented.