To a mixture of 3-{[(1S)-2-(4,5-diphenyloxazol-2-yl)-2-cyclohexen-1-yl]methyl}benzoic acid (250 mg, 0.575 mmol) and α-toluenesulfonamide (98 mg, 0.575 mmol) in DMF (6 ml) was added 4-dimethylaminopyridine (105 mg, 0.863 mmol) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (220 mg, 1.15 mmol). After stirring the resulting mixture at room temperature for 16 hours, the reaction mixture was diluted with EtOAc (30 ml), washed with 1N-hydrochloric acid, water and brine successively, dried over dried over magnesium sulfate, and evaporated in vacuo. The residue was purified by silica gel column chromatography (hexane:EtOAc, 1:1 elution) to give N-benzylsulfonyl-3-{[(1S)-2-(4,5-diphenyloxazol-2-yl)-2-cyclohexen-1-yl]methyl}benzamide (216.4 mg, 64%).
