[C:1]([O:5][C:6]([NH:8][CH2:9][C:10]1[CH:11]=[C:12]([CH2:17][CH:18]([O:24][CH:25]([CH3:27])[CH3:26])[C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH:13]=[CH:14][C:15]=1[OH:16])=[O:7])([CH3:4])([CH3:3])[CH3:2].C1C(=O)N([Br:35])C(=O)C1>C(#N)C.C(OCC)(=O)C>[Br:35][C:14]1[CH:13]=[C:12]([CH2:17][CH:18]([O:24][CH:25]([CH3:26])[CH3:27])[C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH:11]=[C:10]([CH2:9][NH:8][C:6]([O:5][C:1]([CH3:4])([CH3:2])[CH3:3])=[O:7])[C:15]=1[OH:16]402 mg of ethyl 3-(3-[(tertiary butoxycarbonyl)amino]methyl-4-hydroxyphenyl)-2-isopropoxypropionate was dissolved in 5 ml acetonitrile, and 200 mg N-bromosuccimide was added. After stirring at room temperature for 1 hour, the reaction mixture was diluted with ethyl acetate. The organic layer was successively washed with water and brine, dried over anhydrous magnesium sulfate and the solvent was evapoarated. The residue was purified by silica gel column chromatography, and from fractions eluted with hexane-ethyl acetate (5:1), 433 mg of ethyl 3-(3-bromo-5-[(tertiary butoxycarbonyl)amino]methyl-4-hydroxyphenyl)-2-isopropoxypropionate was obtained.
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