[CH2:1]([O:8][C:9]([NH:11][C@H:12]([CH:16]=[O:17])[CH:13]([CH3:15])[CH3:14])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH2:18]([N:20](CC)CC)C.CC(C)(O)C#N>C(Cl)Cl>[CH2:1]([O:8][C:9]([NH:11][C@@H:12]([CH:13]([CH3:15])[CH3:14])[CH:16]([OH:17])[C:18]#[N:20])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1To a solution containing N-benzyloxycarbonyl-L-valinal 22.2 g, 0.094 mol) in methylene chloride (500 mL) and triethylamine (5.81 g, 8.0 mL, 0.057 mol) was added acetone cyanohydrin (24.23 g, 26.0 mL, 0.2847 mol). The reaction was allowed to stir at room temperature overnight and then concentrated under reduced pressure. The residue was taken up into ether and washed with brine (3×). The solvent was removed under reduced pressure and purified by column chromatography (silica gel; 1:2 acetone:hexane) to give 21.38 g (86.6%) of 3-(S)-[(benzyloxycarbonyl)amino]-2-hydroxy-4-methylpentanenitrile as a pale yellow oil; TLC Rf =0.33 (silica gel; 1:2 acetone:hexane).
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