[C:1]([C@@H:3]1[CH2:7][C@@H:6](O)[CH2:5][N:4]1[C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])#[N:2].C(N(S(F)(F)[F:22])CC)C.C(=O)([O-])[O-].[Na+].[Na+]>ClCCl>[C:1]([C@@H:3]1[CH2:7][C@H:6]([F:22])[CH2:5][N:4]1[C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])#[N:2](2S,4R)-tert-Butyl 2-cyano-4-hydroxypyrrolidine-1-carboxylate 13d (49.7 g, 0.2344 mol) was dissolved in 1130 mL of dichloromethane with stirring under argon atmosphere. The mixture was cooled to −30° C. followed by addition of diethylaminosulfur trifluoride (56.7 g, 0.3516 mol). After stirred for 45 minutes, the reaction mixture was warmed up to −5° C. Then the mixture was reacted overnight at room temperature. The reaction was monitored by TLC until the disappearance of the starting materials. The reaction mixture was neutralized with saturated aqueous sodium carbonate solution to pH >7 at such a rate that the reaction temperature was kept below 20° C. Then ice water and 500 mL of dichloromethane were added. The separated organic phase was washed with 500 mL of saturated aqueous sodium hydrogen sulfate and 500 mL of saturated brine successively, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure in which the concentration temperature was kept below 38° C. to obtain the title compound (2S,4S)-tent-butyl 2-cyano-4-fluoropyrrolidine-1-carboxylate 13e (50 g, yield 100%) as a light yellow solid.
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