To a solution of 3-(4-Chloro-2-nitro-benzylamino)-pyrrolidine-1-carboxylic acid tert-butyl ester (3.8 g, 10.7 mmol) in DMF (40 mL) was added Bromo-acetic acid methyl ester (1.01 mL, 10.7 mmol) and K2CO3 (1.48 g, 10.7 mmol). The resultant suspension was stirred at 70° C. overnight. The reaction mixture was diluted with water and ethyl ether. The organic extract was dried over MgSO4, filtered and concentrated to provide the desired product as an oil. The crude product was purified on SiO2 and concentrated to provide the desired product as an oil (2 g, 44%). LCMS (retention time=3.03, ES+428)
