(15 R)-Bimatoprost Acid

(15R)-Bimatoprost Acid is a diastereomeric impurity arising from the stereochemical inversion at the C-15 position of the parent prostaglandin F2α analog, Bimatoprost. It retains the core 20-carbon chain with a cyclopentane ring, hydroxyl groups at C-5, C-7, C-11, and C-13, and a conjugated double bond system between C-9 and C-11. The (15R) configuration introduces a spatially distinct carboxylic acid terminus, altering intermolecular interactions compared to the (15S) parent compound. This impurity is synthesized via enantioselective hydrolysis of Bimatoprost esters or through partial racemization during API manufacturing. It serves as a critical HPLC reference standard for quantifying stereoisomeric purity in bimatoprost formulations.