Puberunine and Puberudine, Two New C18-Diterpenoid Alkaloids from Aconitum barbatum var. puberulum

Two C18-diterpenoid alkaloids, puberunine (1) and puberudine (2), together with four other new alkaloids, including the first examples having β-oriented substitution at C-3 and a rare chloro-substituent were isolated from Aconitum barbatum var. puberulum. Their structures were elucidated by spectroscopic methods. Puberunine and puberudine, which possess a unique rearranged E ring and an opened A ring, respectively, represent new subtypes of the C18-diterpenoid alkaloids. A plausible biosynthetic pathway of 1 and 2 was proposed.