[NH2:1][C@@H:2]([C:6]([OH:9])([CH3:8])[CH3:7])[C:3]([OH:5])=[O:4].[CH:10](=O)[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1.[BH4-].[Na+]>[OH-].[Na+]>[CH2:10]([NH:1][C@@H:2]([C:6]([OH:9])([CH3:8])[CH3:7])[C:3]([OH:5])=[O:4])[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1A mixture of (S)-2-amino-3-hydroxy-3-methylbutanoic acid (18.6 g, 140 mmol), aqueous NaOH solution (2 mol/L, 70 mL) and benzaldehyde (14.56 g, 137 mmol) was stirred at 25° C. for 1 hour and cooled to 0° C. Then to the mixture was added sodium borohydride (3 g, 80 mmol) portion wise with the temperature maintained below 10° C. Then the mixture was warmed to 25° C. and stirred for another 12 hours. The aqueous layer was washed with DCM (30 mL×3) and the organic layer was discarded. The aqueous layer was cooled to 5° C., and adjusted to pH 1-2 with con. HCl. The mixture was stirred at 5° C. for 4 hours, and filtered to give the title compound as a white solid (18.8 g, 60%). The compound was characterized by the following spectroscopic data:
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