C(O[C:4](=O)[CH2:5][C:6]1[CH:11]=[CH:10][C:9]([Br:12])=[CH:8][CH:7]=1)C.[H-].[Na+].[C:16]([O:20][C:21](=[O:27])[NH:22][CH2:23][CH2:24][CH2:25]Br)([CH3:19])([CH3:18])[CH3:17]>CS(C)=O>[CH2:16]([O:20][C:21](=[O:27])[CH2:4][CH:5]([C:6]1[CH:7]=[CH:8][C:9]([Br:12])=[CH:10][CH:11]=1)[CH2:25][CH2:24][CH2:23][NH:22][C:21]([O:20][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:27])[CH3:17]A solution of (4-bromo-phenyl)-acetic acid ethyl ester (2.31 g, 9.50 mmol) in dimethylsulfoxide (6 mL) was added to the suspension of sodium hydride (407 mg, 60% in oil, 10.17 mmol) and stirred 3 min. A solution of (3-bromo-propyl)-carbamic acid tert-butyl ester (2.03 g, 8.52 mmol) in dimethylsulfoxide (6 mL) was added to the solution and stirred at 50° C. for 30 min. The resulting solution was partitioned between ethyl acetate and saturated aqueous ammonium chloride. The aqueous layer was extracted with ethyl acetate. The combined organic layer was washed with water and brine, dried by passing through Celite column, and concentrated in vacuo. The residue was purified by silica gel chromatography eluting ethyl acetate/hexane (4/1 to 3/1, v/v) to afford 3-(4-Bromo-phenyl)-6-tert-butoxycarbonylamino-hexanoic acid ethyl ester (2.43 g, 74%).
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