General procedure for the synthesis of (2S,4R)-1-Boc-2-carbamoyl-4-hydroxypyrrolidine from (2S,4R)-1-Boc-2-cyano-4-hydroxypyrrolidine: 7.82 g (34 mmol) of (2S,4R)-1-Boc-2-carbamoyl-4-hydroxypyrrolidine was dissolved in 80 mL of pyridine, followed by a slow addition of 12 mL (84 mmol) trifluoroacetic anhydride. The reaction mixture was cooled to -20 °C and the reaction was stirred at this temperature. Upon completion of the reaction, the mixture was warmed to room temperature and stirring was continued for 24 hours. The excess trifluoroacetic anhydride was quenched by adding an appropriate amount of water. To the reaction mixture was added 200 mL of ethyl acetate, and the organic layer was washed sequentially with 10% aqueous hydrochloric acid (adjusting the pH to 3-5), 50 mL of 2 N sodium hydroxide solution, and 50 mL of saturated saline. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to give an oily product. Yield: 5.35 g (74% yield).
