BIOSYNTHESIS OF MONOTERPENOID INDOLE ALKALOIDS FROM STRICTOSIDINE

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