[CH3:1][O:2][C:3](=[O:27])[C@@H:4]([NH:16]C(OCC1C=CC=CC=1)=O)[CH2:5][C:6]([F:15])([F:14])[CH2:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1.O1CCOCC1.[ClH:34]>CO.[Pd]>[ClH:34].[CH3:1][O:2][C:3](=[O:27])[C@@H:4]([NH2:16])[CH2:5][C:6]([F:15])([F:14])[CH2:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1
A solution of (S)-2-benzyloxycarbonylamino-4,4-difluoro-5-phenyl-pentanoic acid methyl ester (7.806 g, 20.68 mmol) in 120 mL of methanol and 4 M HCl in dioxane (41.4 mmol, 10.3 mL) is hydrogenated over 10% Pd/C (1.0 g) at 50 psi. After 8 hr, another portion of 10% Pd/C (1.0 g) is added. After 24 hr, the catalyst is removed by filtration over a pad of Celite, and the filtrate is concentrated in vacuum. The resulting solid is dissolved in a minimum amount of methanol and slowly added to ether (150 mL). The resulting slurry is aged for 30 min and then filtered. The solid is dried under suction to afford (S)-2-amino-4,4-difluoro-5-phenyl-pentanoic acid methyl ester hydrochloride (4.950 g, 85.5%).
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