Patent ID: 8772544

Claim:
A method for the purification of crude bimatoprost according to formula (I) comprising at least the steps of: (a) subjecting crude bimatoprost according to formula (I) to chromatography to form a product, wherein the chromatography is carried out using an achiral stationary phase comprising silica and an eluent comprising an alcohol and an apolar solvent, and wherein the alcohol is selected from methanol and ethanol and the apolar solvent is selected from heptane, hexane and cylcohexane; and (b) crystallizing the product obtained in step (a) from a solvent selected from ethers, acetonnitrile, alcohols, esters, or mixtures of any of these solvents to form pure bimatoprost containing less than 0.2% in total of any combination of 15R-bimatoprost and 5, 6-trans-bimatoprost.