CC1(C)[O:6][C@H:5]([CH2:7][CH:8]=O)[C:4](=[O:10])O1.[NH2:12][CH:13]1[CH2:18][CH2:17][N:16]([C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH2:15][CH2:14]1.C(O)(=O)C.[BH-](OC(C)=O)(OC(C)=O)OC(C)=O.[Na+]>C(Cl)CCl>[OH:6][C@@H:5]1[CH2:7][CH2:8][N:12]([CH:13]2[CH2:14][CH2:15][N:16]([C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH2:17][CH2:18]2)[C:4]1=[O:10](R)-2-(2,2-Dimethyl-5-oxo-1,3-dioxolan-4-yl)acetaldehyde (16 g, 101 mmol) was dissolved in ClCH2CH2Cl (500 mL) and tert-butyl 4-aminopiperidine-1-carboxylate (40.5 g, 202 mmol) and acetic acid (6.94 mL, 121 mmol) were added and stirred at ambient temperature for 15 minutes. NaBH(OAc)3 (64.3 g, 304 mmol) was added in 3 portions and the reaction stirred at ambient temperature overnight. The reaction was carefully quenched with saturated aqueous NaHCO3. The reaction was partitioned between aqueous NaHCO3 and CH2Cl2, extracted, washed with 10% citric acid, brine, dried over Na2SO4, filtered and concentrated. The solids were purified over silica gel (5 to 10% methanol in EtOAc) to afford (R)-tert-butyl 4-(3-hydroxy-2-oxopyrrolidin-1-yl)piperidine-1-carboxylate (20.5 g, 72.1 mmol, 71.3% yield) as a white solid.
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