[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]([NH:12][C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[C:9]([OH:11])=[O:10])=[CH:4][CH:3]=1.C(=O)([O-])O.[K+].[CH2:25](Br)[C:26]1[CH:31]=[CH:30][CH:29]=[CH:28][CH:27]=1.O>CN(C)C=O>[CH2:25]([O:10][C:9](=[O:11])[CH:8]([C:5]1[CH:4]=[CH:3][C:2]([Br:1])=[CH:7][CH:6]=1)[NH:12][C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[C:26]1[CH:31]=[CH:30][CH:29]=[CH:28][CH:27]=1(4-Bromo-phenyl)-tert-butoxycarbonylamino-acetic acid (780 mg, 2.4 mmol) was dissolved in N,N-dimethylformamide (15 mL) and to this was added potassium hydrogen carbonate (260 mg, 2.6 mmol) followed by benzyl bromide (281 μL, 2.4 mmol) and stirring continued at ambient temperature for 6 hours. The reaction was poured into water (50 mL) and extracted with ethyl acetate (2×60 mL). The organic extracts were washed with water (2×20 mL), brine, dried over sodium sulfate and filtered through a layer of silica gel. The filtrate was concentrated in vacuo and the residue crystallized from 100% hexane to give (4-bromo-phenyl)-tert-butoxycarbonylamino-acetic acid benzyl ester (500 mg, 50%).
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