[OH-].[Li+].[C:3]([O:7][C:8]([NH:10][C@@H:11]([CH2:16][C:17]1[CH:22]=[CH:21][C:20]([O:23][CH:24]([CH3:26])[CH3:25])=[CH:19][CH:18]=1)[C:12]([O:14]C)=[O:13])=[O:9])([CH3:6])([CH3:5])[CH3:4]>O.CO>[C:3]([O:7][C:8]([NH:10][C@@H:11]([CH2:16][C:17]1[CH:22]=[CH:21][C:20]([O:23][CH:24]([CH3:26])[CH3:25])=[CH:19][CH:18]=1)[C:12]([OH:14])=[O:13])=[O:9])([CH3:5])([CH3:6])[CH3:4]Lithium hydroxide (160 mg, 6.8 mmol) in water (10 mL) was added to a solution of (S)-methyl 2-(tert-butoxycarbonylamino)-3-(4-isopropoxyphenyl)propanoate in methanol (30 mL). The reaction was stirred for 24 h., and was concentrated under reduced pressure to remove the methanol. The remaining water layer was adjusted to pH=3 using 1 N HCl aqueous solution, and was extracted with ethyl acetate. The organic phase was washed with saturated brine, dried over magnesium sulfate, filtered and concentrated under reduced pressure to give the crude product (2S)-2-[(tert-butoxycarbonyl)amino]-3-(4-isopropoxyphenyl)propanoic acid (1 g, 90%). Analytical LCMS (M+H-Boc)+: m/z=223.9.
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