Macrorhynines A and B, Two Novel Norditerpenoid Alkaloids from Aconitum macrorhynchum

Two novel norditerpenoid alkaloids, macrorhynines A and B (1 and 2), together with seven known compounds, were isolated from Aconitum macrorhynchum. The structures of the new compounds were elucidated as (1α,6α,14α)-8-acetoxy-1,6,16-trimethoxy-4-(methoxymethyl)aconitan-14-yl 4-methoxybenzoate (1) and (1α,6α,14α)-8-acetoxy-13-hydroxy-1,6,16-trimethoxy-4-(methoxymethyl)aconitan-14-yl 4-methoxybenzoate (2) on the basis of spectral analyses. The novel compounds were found to contain the rare C(19)N, azomethine, group.