Biosynthesis of terpenes and steroids. Part III. Squalene cyclisation in the biosynthesis of triterpenoids; the biosynthesis of fern-9-ene in Polypodium vulgare Linn

Abstract

An examination of the pentacyclic triterpenes of Polypodium vulgare Linn. has shown the presence of 21-epifern-9-ene, fern-7-ene, hopene-1, and an as yet unidentified triterpene hydrocarbon, in addition to the previously reported constituents. The biosynthesis of fern-9-ene was shown to involve a direct proton-catalysed cyclisation of squalene, rather than a cyclisation–reduction process based on 2,3-epoxysqualene.