An improved synthesis of latanoprost involving effective control on 15(S) diastereomer

An improved process for the synthesis of latanoprost having excellent optical purity (de 99.9%, [alpha](D)(20) = +35.37 degrees (c = 0.90, acetonitrile)) without use of preparative HPLC is described. This process involves effective purification of hydroxyl intermediate (5A) through solvent crystallization followed by inhibition of inversion of the chiral center at C-15 position. This was possible due to judicious use of diol intermediate (6) for double bond reduction prior to hydroxyl protection.