Facile Synthesis of 7-epi-Taxane and Its Derivatives and Preliminary Evaluation of Anticancer Activity

7-epi-Taxane has been achieved efficiently in gram scale from natural taxane via inversion of the 7-hydroxyl group simply using Ag2O as catalyst and DMF as solvent. The catalyst could be quantitatively recovered by filtration without loss of catalytic activity. This condition is also applicable to the direct epimerization of taxane derivatives (e.g., docetaxel and paclitaxel) to 7-epi-taxane derivatives (e.g., 7-epi-docetaxel and 7-epi-paclitaxel). Furthermore, 33 ester derivatives of 7-epi-taxane with different amino acid moieties at the position of C-13 were successfully synthesized via esterification without protecting C-7-OH. Bioassay results revealed that compounds 13 and 18 have good selectivity against prostatic cancer cell line DU145, with IC50 value as low as 15.9 nmol/L for 18.