Ouvrardianines A and B, Two New Norditerpenoid Alkaloids from Aconitum ouvrardianum

Two new norditerpenoid alkaloids, ouvrardianines A and B ( 1 and 2 , resp.), together with eight known compounds, were isolated from Aconitum ouvrardianum. The structures of the new compounds were elucidated as (1 α ,6 α ,14 α ,16 β )‐8‐(acetyloxy)‐13‐hydroxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)aconit‐19‐en‐14‐yl benzoate ( 1 ) and (1 α ,6 α ,14 α ,16 β )‐8‐(acetyloxy)‐20‐formyl‐13‐hydroxy‐1,6,16‐trimethoxy‐4‐(methoxymethyl)aconitan‐14‐yl benzoate ( 2 ) on the basis of spectral analyses. The new compound 1 was found to contain the rare C(19)N imine group.