Combine a solution of oxalyl chloride (0.238 mL, 2.72 mmol) in dichloromethane (25 mL) with dimethyl sulfoxide (0.322 mL, 4.54 mmol) at −78° C. and stir. After 15 minutes, add a solution of (S)-2-(2-hydroxyethyl)piperazine-1,4-dicarboxylic acid di-tert-butyl ester (0.60 g, 1.82 mmol) in dichloromethane at −78° C. via cannula and stir at −78° C. After one hour, add triethylamine (1.27 mL, 9.08 mmol) and warm to room temperature overnight. Dilute the mixture with saturated aqueous sodium bicarbonate and extract three times with dichloromethane. Combine the organic layers, dry over sodium sulfate and concentrate under reduced pressure to give the title compound: mass spectrum (APCI): m/z=129.1 (M+1-2BOC).
