[F:1][C:2]1([F:17])[C:7](O)([OH:8])[CH2:6][CH2:5][N:4]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:3]1.[BH4-].[Na+].Cl.C([O-])(O)=O.[Na+]>CCO>[F:17][C:2]1([F:1])[CH:7]([OH:8])[CH2:6][CH2:5][N:4]([C:10]([O:12][C:13]([CH3:15])([CH3:14])[CH3:16])=[O:11])[CH2:3]1tert-Butyl 3,3-difluoro-4,4-dihydroxypiperidine-1-carboxylate (3.10 g, 12.2 mmol) was dissolved in 95% EtOH (50 mL) and the solution was treated with sodium borohydride (2.32 g, 61.2 mmol) and stirred at ambient temperature for 3 hours. The reaction was treated dropwise with 3N HCl until vigorous gas evolution ceased, then stirred at ambient temperature for 20 minutes (pH of the mixture was 3-4 at this point). The reaction was neutralized with saturated NaHCO3 and concentrated in vacuo. The residue was dissolved in ethyl acetate and water and the layers were separated. The aqueous layer was washed with ethyl acetate and the combined organic layers were washed with saturated NaCl, dried over Na2SO4 and concentrated in vacuo to provide the desired product as a white solid (1.39 g).
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