Cationic cyclization of bicyclic diterpenes

Abstract

Manool and agathadiol cyclize in formic acid to the 13-epimeric pimara-8,15-dienes and 14α-hydroxyhibane derivatives. The mechanistic and biosynthetic implications of these results are discussed in relation to other work involving cations in tetracyclic diterpenes. The nuclear magnetic resonance spectra of relevant tricyclic and tetracyclic diterpenes are documented.