Synthetic Studies on Taxol:  Highly Stereoselective Construction of the Taxol C-Ring via S_N2‘ Reduction of an Allylic Phosphonium Salt

The highly stereoselective construction of the C3 stereogenic center of the taxol C-ring is described. The trans isomer at the C3−C8 position of the taxol C-ring, which is required for the total synthesis, as well as its diastereomeric cis isomer were successfully synthesized with highly diastereoselective S_N2‘ reduction of the allylic phosphonium salts.