Methoxyabietane Diterpenoid from the Root of Salvia phlomoides and Structural Correction of Another Diterpene from Cryptomeria japonica

A reinvestigation of the acetone extract of the root of Salvia phlomoides (Labiatae) allowed the isolation of a new abietane diterpenoid whose structure (6,11-dihydroxy-12-methoxy-5,8,11,13-abietatetraen- 7-one) was established by exhaustive NMR spectroscopic studies and by partial synthesis from 14-deoxycoleon U, another abietane constituent of the same extract. The physical and spectroscopic data of the methoxyabietane isolated from S. phlomoides were identical to those reported for another diterpenoid previously found in Cryptomeria japonica (Taxodiaceae), to which the regioisomeric structure 6,12-dihydroxy-11-methoxy-5,8,11,13-abietatetraen-7-one had been erroneously attributed by other authors.