7-Epipaclitaxel (crude) is a taxane-derived impurity arising from the epimerization of the C-7 hydroxyl group in Paclitaxel, resulting in an ฮฑ-configured stereocenter. It retains the core 12-membered oxetane ring, 6-membered lactone, and side-chain phenylisoserine ester characteristic of the taxane scaffold. The compound exhibits a benzoyl group at C-2 and a hydroxyl at C-13, with stereochemical inversion at C-7 compared to the parent drug. This impurity commonly forms during Paclitaxel synthesis via partial epimerization in acidic conditions. It serves as a critical HPLC reference standard for quantifying process-related epimerization byproducts in API batches.
