Formal synthesis of chelamidine alkaloids and their derivatives.

A concise two-step operation of α-amination of aldehydes and subsequent Friedel-Crafts/Prins-type cyclization towards accessing tetrahydrobenzo[c]phenanthridine and related structures was developed. The reaction displayed a broad substrate scope and good tolerance to a variety of substituents such as different aromatic heterocyclic rings. In addition, the effectiveness of this protocol was also demonstrated in the formal synthesis of homochelidonine and chelamidine.