The alkaloidal components of eight Erythrina plants (Leguminosae), E. arborescence Roxb., E. orientalis (L.) MURR, E. crysta-galli LINN, E. crysta-galli (L.) cv. Maruba Deiko H. Murata, E. x bidwilli LINDL, E. poeppigiana (Walp) O. F. Cook, E. glauca WILLD, and E. variegata L. were examined. As a result of this study, five new oxo-erythrinan alkaloids, erythrinine (8), 11-hydroxyerysotrine (9), erysotramidine (10), erytharbine (11), crystamidine (12) and a di-benz[d,f]azonine type alkaloid, erybidine (2), were isolated respectively. Two tetrahydroprotoberberine type alkaloids, scoulerine (4) and coreximine (5), were also isolated from E. orientalis (L.) MURR.A new synthetic route to erythrinan alkaloids was developed, via the cia -C/D-ring fused 15-methoxy-16-hydroxyerythrinan-2, 8-dione (49) as a key intermediate, from the enol methyl derivative (48) which was obtained by Birch reduction of the benzyl amide (47). The total synthesis of (+/-)-erysotramidine (10), an oxo-erythrinan alkaloid, including a novel ring cleavage of the azatricyclo[3.2.0.0] compound (70) with phenylselenyl chloride is described.