A new diterpenoid alkaloid, which has been called acoseptine, has been isol
ated from the plant Aconitum septentrionale Koelle. This is the first alkal
oid of the anhydrolycoctonine type with a C-8-C-17 bond and a carbonyl grou
p at C-7. The structure of acoseptine has been established on the basis of
IR, mass, and H-1 and C-13 NMR spectra.