Aporphine alkaloids from the roots of Stephania viridiflavens

Further investigation on the phytochemistry of the medicinal plant Stephania viridiflavens led to the isolation of a new naturally occurring aporphine alkaloid, (+)-6R, 6aS-isocorydine N-oxide (1), together with three known aporphine alkaloids: (+)-6R, 6aS-corydine N-oxide (2), (+)-N-methyl-laurotetanine (3) and (+)-stepharine (4). The structure and stereochemistry of 1 were determined on the basis of spectroscopic methods and confirmed by synthesis. Alkaloids 2-4 were isolated for the first time from this species.