A new C20-diterpene alkaloid of the coryphine type has been isolated from the plant Aconitum coreanum (Levl.) Rapaics, and it has been called coryphidine. Its structure has been established on the basis of an analysis of IR and1H and13C NMR spectra. This is the second diterpene alkaloid having a hexahydro-N-methylindole fragment at C-17. Coryphidine contains an imide grouping, which is unusual for a diterpene skeleton. © 1992 Plenum Publishing Corporation.