Four New Nor-Diterpenoid Alkaloids from Aconitum brachypodum

Four new C19‐nor‐diterpenoid alkaloids, named brachyaconitines A–D (1–4), were isolated from the roots of Aconitum brachypodum Diels. Their structures were elucidated as 3‐O‐acetyl‐20‐deethyl‐20‐formylaconitine (1), 3‐O‐acetyl‐19,20‐didehydro‐20‐deethylaconitine (2), 3‐O‐acetyl‐8‐de(acetyloxy)‐7,8,17,20‐tetradehydro‐20‐deethyl‐7,17‐secoaconitine (3), and 1‐O‐methylflavaconitine (4) by means of MS, IR, 1D‐ and 2D‐NMR analyses. The structure of compound 1 was confirmed by an X‐ray diffraction experiment.