Studies in terpenoid biosynthesis. Part VIII. The formation of the trichothecane nucleus

Abstract

The incorporation of [2-³H₂]-, (4R)-[4-³H]-, and [5-³H₂]-mevalonate, [2-³H]geranyl pyrophosphate, and [1-³H₂]-and [2-³H]-farnesyl pyrophosphate into the trichothecane nucleus is described. The results define the manner of folding of the farnesyl pyrophosphate and exclude a γ-bisabolene intermediate in the biosynthesis. The central prenyl (4R)-[4-³H]-label is retained in the biosynthesis and is transferred to C-2 of the trichothecane. The relative numbers of [2-³H₂]- and [5-³H₂]-mevalonoid labels that are incorporated suggest that the carbonyl group of trichothecin might arise through the rearrangement of an epoxide.