Phenol oxidation and biosynthesis. Part XXII. The alkaloids of Erythrina lysistemon, E. abyssinica, E. poeppigiana, E. fusca, and E. Lithosperma; the structure of erythratidine

Abstract

Erythrina lysistemon, E. abyssinica, E. poeppigiana, E. fusca, and E. lithosperma have been examined for alkaloids of biogenetic interest. In addition to the known Erythrina alkaloids, α- and β-erythroidine, eryosdine, erythraline. erythratine, and erysotrine, new alkaloids erythristemine. erythratidinone, and 3-demethoxyerythratidinone were isolated and characterised. The aporphine alkaloid isoboldine, and the benzyltetrahydroisoquinoline alkaloids (–)-orientaline and (+)-N-nororientaline were also isolated. A partial synthesis of erythratidine indicated a 2S configuration. A plausible biogenetic scheme for the new alkaloids is discussed.