Diterpenoids. XL. Acid Catalyzed Rearrangement of Dehydroabietic Acid Derivatives

Abstract

Acid treatment in acetic anhydride of blocked cyclohexadienone derivatives (6a) and (6b) obtained from l-abietic acid (1) gave 14 and 16, respectively, through Wagner-Meer-wein rearrangement of the angular methyl group. On the other hand, under similar conditions, 6c and 6d were transformed into 18 and 20, respectively, as the result of an abnormal dienone phenol rearrangement, namely, aromatization of the B-ring with concomitant cleavage of C-C bond.