A Novel Entry to the Taxane Structural Unit

Taxanes, such as, e.g., taxinin Β 1 or taxol 2, are unu­ sual hydroxylated diterpenes which occur in plants of the family Taxaceae, to which the yew tree (Taxus baccata L.) belongs. The antileukemic and antitumoral activities of some taxanes and the problems encountered in the syn­ thesis of the unusual tricyclic carbon skeleton 3 have aroused increasing interest in recent years . According to in vitro experiments, less substituted taxane derivatives could also be biologically active. For this reason it ap­ peared to us that the synthesis of a tricyclic taxane skele­ ton with functional groups in ring A and ring Β which should be readily convertible into hydroxy groups might prove rewarding. We report here on a stereoselective route to the tricycle 4.