Br.[OH:2][C:3]1[CH:8]=[CH:7][C:6]([CH2:9][CH2:10][C@@H:11]([NH2:15])[C:12]([OH:14])=[O:13])=[CH:5][CH:4]=1.C(N(CC)CC)C.[C:23]([O:27][C:28](ON=C(C1C=CC=CC=1)C#N)=[O:29])([CH3:26])([CH3:25])[CH3:24]>O1CCOCC1.O.C(OCC)(=O)C>[OH:2][C:3]1[CH:4]=[CH:5][C:6]([CH2:9][CH2:10][C@@H:11]([NH:15][C:28]([O:27][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:29])[C:12]([OH:14])=[O:13])=[CH:7][CH:8]=1To a stirred solution of (2R)-4-(4-hydroxyphenyl)-2-amino-butanoic acid hydrobromide (5.0 g, 18.18 mmol) and triethylamine (5.25 mL, 2 eq) in dioxane (50 mL) and water (50 mL) at 0° C. was added a solution of 2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitile (BOCON) (4.9 g) in dioxane (10 mL). The reaction mixture was allowed to warm up to room temperature and stirred for five hours when it became homogeneous: The reaction mixture was diluted with ethyl acetate (EtOAc) and the organic was seperated. The aqueous layer was acidified with citric acid (20%) and extracted with EtOAc. The combined organics were washed with brine, dried over magnesium sulfate, filtered and evaporated to give the desired material.
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