[CH2:1]([O:8][C:9]([NH:11][CH:12]([CH:17]([CH3:19])[CH3:18])[CH:13]([OH:16])[C:14]#[N:15])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.N1C=CC=CC=1.[C:26](OC(=O)C)(=[O:28])[CH3:27]>C(OCC)(=O)C>[CH2:1]([O:8][C:9]([NH:11][C@@H:12]([CH:17]([CH3:19])[CH3:18])[CH:13]([O:16][C:26](=[O:28])[CH3:27])[C:14]#[N:15])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1To a solution containing 3-[(benzyloxycarbonyl)amino]-2-hydroxy-4-methylpentanenitrile (32.0 g, 0.12 mol) and pyridine (59 mL) was added acetic anhydride (73.6 g, 68 mL, 0.72 mol) dropwise at RT. After 3 h the reaction was diluted with ethyl acetate and washed with water. The organic layer was separated, dried (anhydrous magnesium sulfate) and evaporated. The residue was purified by column chromatography (silica gel, 1:1 hexane:ethyl acetate) to give 33.08 g (94.0 of 3-(S)-[(benzyloxycarbonyl)amino]-2-acetoxy-4-methylpentanenitrile- as a viscous yellow oil; TLC Rf =0.70 (silica gel, 1:1 hexane:ethyl acetate).
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