A solution of sodium bis(trimethylsilyl)amide in THF (58.7 mL, 58.75 mmol) was added dropwise to a stirred solution of (R)-tert-butyl 3-hydroxypyrrolidine-1-carboxylate (10 g, 53.41 mmol) in DMF (100 mL) over a period of 10 minutes under nitrogen. The resulting solution was stirred at ambient temperature for 10 minutes. Ethyl bromoacetate (8.92 g, 53.41 mmol) was added dropwise over 10 minutes (exotherm. Temperature kept below 30° C. using a cold water bath) and the reaction was stirred at ambient temperature for 20 hours.
