DITERPENES FROM SALVIA-MELLIFERA AND THEIR BIOGENETIC SIGNIFICANCE

The new diterpenes, 11,12-dihydroxy-20-nor-abieta-5(10),8,11,13-tetraen-1-one and isogaldosol, together with the known compounds carnosic acid, carnosol, rosmanol, rosmadial, galdosol and isorosmanol were isolated from the aerial part of Salvia mellifera. The structures of the new diterpenes were established from their spectral data and by chemical correlations. The co-occurrence of all these compounds in one species taken together with their chemical behaviour led to the postulation of a biogenetic pathway to highly oxidized abietatriene diterpenes in which enzymatic dehydrogenation processes and the participation of singlet-state oxygen appear to play an important role.