(3R,4S)-3-(2-Bromoacetyl)-4-ethyl-1-pyrrolidinecarboxylic acid phenylmethyl ester

synthetischeDimethylsulfoxonium 2-((3R,4S)-1-benzyloxycarbonyl-4-ethylpyrrolidin-3-yl)-2-oxo-ethylide (10.0 g, 28.5 mmol, 1.0 equivalents), THF (100 mL), and 33% HBr in AcOH (8.37 g, 34.1 mmol, 1.2 equivalents) were charged sequentially and heated to 40° C. The reaction mixture was agitated for 5 hours, cooled to 20° C, and then distilled under vacuum to approximately 65 mL. EtOAc (20 mL) and heptane (50 mL) were charged, and the reaction mixture was washed with water (5×50 mL). The organic layer was concentrated under vacuum and chased with EtOAc (2×50 mL) concentrating to dryness each time. N,N-dimethylacetamide (20 mL) was then charged to provide 30.8 g of a 24.0 wt/wt % solution of (3R,4S)-3-(2-Bromoacetyl)-4-ethyl-1-pyrrolidinecarboxylic acid phenylmethyl ester (yield: 73%).