Biosynthesis of indole diterpenes, emindole, and paxilline: involvement of a common intermediate.

The key step for construction of the carbon skeleton in the indole diterpenes, paxilline, and emindole DA was examined. Intact incorporation of multiply (2)H-labeled 3-geranylgeranylindole into two different fungal metabolites proves 3-geranylgeranylindole to be a biosynthetic intermediate. These results give evidence that indole diterpenes are biosynthesized via epoxidation of a common intermediate, and the subsequent cationic cyclization, analogous to those in the steroid biosynthesis. [structure: see text]