A solution of DMSO (31.4 μl, 0.44 mmol) in dichloromethane (1 ml) was added drop wise to a solution of oxalyl chloride (19 μl, 0.22 mmol) in dichloromethane (2 ml) at −78° C. under argon. After 15 min at −78° C., A solution of methyl [(2S,4R)-1-(biphenyl-4-ylcarbonyl)-4-hydroxypyrrolidin-2-yl]acetate (50 mg, 0.15 mmol) in dichloromethane (1 ml) was added drop wise. The reaction mixture was stirred at −78° C. for 1 hour and triethylamine (0.102 ml, 0.74 mmol) was added and allowed to warm to room temperature. The reaction mixture was diluted with ethyl acetate, washed with water then brine. The organic phase was dried (MgSO4) and concentrated to afford the methyl [(2S)-1-(biphenyl-4-ylcarbonyl)-4-oxopyrrolidin-2-yl]acetate (66 mg). Yield: 100%. HPLC purity: 99%
