Diterpenoids. 45. Ozonolysis of phenolic dehydroabietic acid derivatives.

Ozonolysis of phenolic dehydroabietic acid derivatives with an isopropyl group at 13-position was investigated and the direction of cleavage of the aromatic ring by means of ozonolysis was found to be affected by the substitution pattern of hydroxyl group in the aromatic ring. Ozonolysis of the 12-hydroxy ester (12) afforded the pentanorlabdane type compounds, (13), (14), and (15), while ozonolysis of the 14-hydroxy ester (17) and (18) gave the drimane type products, (19) and (20).