Diterpenoids. X. A Synthesis of c-Homohydrofluorene

Abstract

Previously, l-abietic acid (I) was transformed into hydrofluorene derivative, regarded as one of the basic structure of gibberellin, by application of the benzilic acid rearrangement. As successive transformation, a synthesis of c-homohydrofluorene (XX) has been realized by opening of B/C-ring juncture and successive ring closure of Δ^{8, 9}-unsaturated ester (X) prepared from (I).