A New Access to the Cleavage of the N-19 Bond of Norditerpenoid Alkaloids and Their Derivatives by Formation of Oxaziridines

A new N,19-seco-norditerpenoid alkaloidal compound (5) possessing an oxaziridine group from yunaconitine (1) was furnished by using a new method in five steps involving acetylation, imination, quaternization, formation ofN,O-mixed ketal, and oxidation in 50% overall yields.