CHEMICAL EVIDENCE FOR THE PARTICIPATION OF A PEREPOXIDE INTERMEDIATE IN THE REACTION OF SINGLET OXYGEN WITH MONO-OLEFINS IN RELATIONSHIP WITH THE BIOGENETIC PATHWAY TO HIGHLY OXIDIZED ABIETANE DITERPENES

Chemical evidence has been obtained in two separate experiments for the participation of a perepoxide intermediate in the reaction of singlet oxygen with mono-olefins. The intramolecular trapping of such an intermediate in the reaction of 6,7-didehydrocarnosic acid derivatives with molecular oxygen in unequivocal singlet oxygen-generating conditions to give rosmanol and isorosmanol derivatives represents conclusive proof for the cited mechanism. Futhermore, such chemical evidence supports our earlier hypothesis of a biogenetic pathway to highly oxidized abietatriene diterpenes in which enzymatic dehydrogenation and singlet-state oxygen appear to play important roles.