Diterpenoids. XXVI. Synthesis of 11-Methoxy-diterpenoids.(1). Synthesis of Antipodal 11-Methoxy-deoxypodocarpic Acid Derivatives

Abstract

7-Oxo esters (IV) and (V) derived from l-abietic acid (III) were converted to half esters (XI) and (XV), respectively. Intramolecular cyclization of XV gave the expected 11-methoxy oxo ester (XVI), but that of XI yielded the undesirable bicyclo [3, 3, 1] n onane ester (XVII) via a methoxy migration of the methoxy carbonyl group. 11-Hydroxy diterpenoid is not only a potential intermediate for the syntheses of taxodione (I) and callicarpone (II), but also is regarded as an important substance for an oxidative substitution of A-ring or 10-methyl group from its 11-hydroxyl group.