[O:1]=[C:2]1[CH2:15][C:4]2([CH2:7][N:6]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:5]2)[CH2:3]1.[BH4-].[Na+].C([O-])(O)=O.[Na+]>CO>[OH:1][CH:2]1[CH2:3][C:4]2([CH2:7][N:6]([C:8]([O:10][C:11]([CH3:13])([CH3:12])[CH3:14])=[O:9])[CH2:5]2)[CH2:15]1To a solution of tert-butyl 6-oxo-2-azaspiro[3.3]heptane-2-carboxylate (507 mg, 2.4 mmol) in MeOH (5.0 mL) was added NaBH4 (182 mg, 4.8 mmol) at 0° C. under N2. It was stirred at 0° C. for 30 min. The solution was concentrated by evaporator in vacuo to give crude solid. A saturated solution of NaHCO3 (30 mL) was added. The aqueous mixture was extracted with DCM (4×30 mL). The combined organic solution was dried over anhydrous Na2SO4 and then concentrated by evaporation in vacuo to afford tert-butyl 6-hydroxy-2-azaspiro[3.3]heptane-2-carboxylate (511 mg, 100%) as a white solid.
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