Oxidative C-Ring Opening of Abietane Diterpenes with Ammonium ­Cerium(IV) Nitrate

The oxidation reaction of 11,12-di- O-methylcarnosol with ammonium cerium(IV) nitrate (CAN) gave an abietane diterpene with the C-ring opened and a diester function. The structure of this diester was established by spectroscopic analysis and by chemical means. The reaction of 11,12-di- O-dimethylgaldosol with CAN gave a similar result, yielding a δ-lactone which structure was established as 7-hydroxy-11,12- SECO-8,13-abietadien-12,7:20,6β-dilacton-11-oic acid methyl ester by spectroscopic analysis and chemical means. These results could be useful to accede to other natural -products like rosmic acid.