New norditerpenoid alkaloids from Aconitum septentrionale

Article abstract of DOI:10.1016/S0040-4020(01)90782-3

A study of the alkaloids present in the roots of Aconitum septentrionale Koelle has led to the isolation of four new norditerpenoid alkaloids: 8-O-methyllycaconitine (1), 6-O-acetylacosepticine (2), acoseptrigine (3), and acoseptriginine (4), besides seven known alkaloids: lappaconine (5), N-acetylsepaconitine (6), puberaconitine (7), lappaconitine (8), N-deacetyllappaconitine (9), lycoctonine (10), and lapaconidine (11). The structures of these alkaloids were determined by spectral data and chemical correlation with alkaloids of established structures. Thus, 8-O-methyllycaconitine (1) was converted to septentrionine (12) by treatment with methanolic ammonia. Saponification of 6-O-acetylacosepticine (2) and acoseptrigine (3) with 5% ethanolic KOH yielded acoseptricine (13) and 14-O-methylforesticine (14), respectively. A synthetic sample of lappaconine (5) was prepared from lappaconitine (8) by alkaline hydrolysis. Acidic hydrolysis of N-acetylsepaconitine (6) afforded sepaconitine (15). N-acetylsepaconitine (6) and puberaconitine (7) have not been previously isolated from A. septentrionale. ¹³C chemical shifts for C(5), C(10), C(13) and N-CH₂-CH₃ of lapaconidine (11) have been revised on the basis of DEPT measurements.