[C:1]([O:5][C:6]([NH:8][C@@H:9]([C@H:13]([OH:22])[C:14]1[CH:19]=[CH:18][C:17]([O:20][CH3:21])=[CH:16][CH:15]=1)[C:10]([O-:12])=[O:11])=[O:7])([CH3:4])([CH3:3])[CH3:2].O[Li].O.CCOC(C)=O.O>CO.C1COCC1>[C:1]([O:5][C:6]([NH:8][C@@H:9]([C@H:13]([OH:22])[C:14]1[CH:19]=[CH:18][C:17]([O:20][CH3:21])=[CH:16][CH:15]=1)[C:10]([OH:12])=[O:11])=[O:7])([CH3:4])([CH3:3])[CH3:2]A mixture of (2S,3R)-2-(tert-butoxycarbonylamino)-3-hydroxy-3-(4-methoxyphenyl)propanoate (1.44 g, 4.44 mmol) and LiOH—H2O (280 mg, 6.66 mmol) in MeOH/THF (30 mL, 1:1) was stirred for 1 h at ambient temperature. EtOAc/water (30 mL/50 mL) was added and the two phases were separated. The aqueous phase was washed with EtOAc (30 mL×2) then acidified with dilute HCl to pH=5. The resulting mixture was extracted with EtOAc (50 mL×2). The organics were combined, dried over anhydrous sodium sulfate, and concentrated to afford (2S,3R)-2-(tert-butoxycarbonylamino)-3-hydroxy-3-(4-methoxyphenyl)propanoic acid (0.90 g, 65% yield) as a colorless solid.
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