The biosynthesis of monoterpenoid indole alkaloids from strictosidine

Abstract

The differential incorporation of doubly labelled strictosidine and vincoside into several indole alkaloids belonging to the Corynanthe(3α and 3β series), Aspidosperma, and Iboga types in three plant families has been studied, and it has been demonstrated that only strictosidine is incorporated while vincoside is metabolically inert in these plants with regard to alkaloid formation. During the conversion of strictosidine into the 3β-indole alkaloids, the hydrogen atom at the 3-position is lost, while it is retained during the biosynthesis of the 3α alkaloids. The chemical synthesis of [7-³H]secologanin, an important intermediate for further work in the biosynthesis of monoterpenoid alkaloids, is also described.