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

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.