Total Synthesis of Oxyfagaronine, Phenolic Benzo[c]phenanthridine and General Synthetic Way of 2,3,7,8- and 2,3,8,9-Tetrasubstituted Benzo[c]phenanthridine Alkaloids

Abstract

Benzo[c]phenanthridine alkaloids such as oxynitidine, oxysanguinarine, oxyavicine and phenolic oxyfagaronine were synthesized from easily available starting benzonitriles 5 and toluamides 6 using a lithiated toluamide-benzonitrile cycloaddition reaction. The coupling reaction provided 3-arylisoquinolinones that were transformed to the benzo[c]phenanthridones. This method is highly efficient and could be useful for preparing diverse substituted aromatic benzo[c]phenanthridine compounds on a multi gram scale.