[C:1]([O:5][C:6](=[O:20])[NH:7][C@H:8]([CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)[C:9](=[O:12])[CH2:10][Cl:11])([CH3:4])([CH3:3])[CH3:2].[BH4-].[Na+]>C1COCC1.O>[C:1]([O:5][C:6](=[O:20])[NH:7][C@H:8]([CH2:13][C:14]1[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=1)[C@@H:9]([OH:12])[CH2:10][Cl:11])([CH3:4])([CH3:2])[CH3:3]To a stirred solution of (R)-1-Benzyl-3-chloro-2-oxopropylcarbamic acid tert-butyl ester (8.0 g, 27 mmol) in THF/water (200 mL, 9/1, v/v) at 0° C. is added NaBH4 (1.23 g, 32 mmol). After 30 min the mixture is concentrated under reduced pressure and the residue is suspended in a mixture of water and ethyl acetate (1:1, v/v). This mixture is cooled to 0° C. and the pH is adjusted to ˜2 by the slow addition of 2M NaHSO4. The phases are separated and the organic layer is washed with water and brine, dried over Na2SO4 and concentrated under reduced pressure to afford a white solid as a mixture of diastereomers (7.92 g, 27 mmol, ˜5:2 R,R:R,S), which is purified using General Purification Procedure C to afford the title compound as a white solid (4.45 g, 15 mmol).
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