Total Synthesis of Enantiopure Phalarine via a Stereospecific Pictet−Spengler Reaction: Traceless Transfer of Chirality from l-Tryptophan

An appropriately constructed 2-substituted derivative of l-tryptophan undergoes conversion to a prephalarine structure in a single step. The reaction occurs in a diastereoselective fashion, leading shortly thereafter to the naturally occurring version of the alkaloid phalarine.