Unexpected amine-triggered skeletal modification of fascaplysin and its derivatives: rapid access to δ,γ-biscarbolines

Abstract

An unsuccessful attempt to directly construct alkaloid iheyamine A from a fascaplysin framework resulted in the discovery of a novel synthetic approach to alkylated δ,γ-biscarboline derivatives. With the easy-to-operate reaction conditions of this protocol, 18 alkylated biscarbolines have been prepared in moderate to good yields. An unexpected domino transformation was proposed to involve a pyridinium ring-opening/aza-electrocyclization/oxidative deformylation sequence.