[CH2:1]([O:8][C:9]([NH:11][C@H:12]([CH2:22]O)[CH2:13][CH2:14][C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C(Br)(Br)(Br)[Br:25].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>ClCCl>[CH2:1]([O:8][C:9]([NH:11][C@H:12]([CH2:22][Br:25])[CH2:13][CH2:14][C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1A solution of tert-butyl(4S)-4-{[(benzyloxy)carbonyl]amino}-5-hydroxypentanoate (5.0 g, 15.5 mmol) in dichloromethane (50 ml) was cooled to 0° C. and carbontetrabromide (6.15 g, 18.5 mmol) was added thereto. At the same temperature triphenylphosphine (5.68 g, 21.7 mmol) was divided to five portions and they were added to the reaction mixture for every 2 minutes and the mixture was stirred for 30 minutes. The solvent was removed in vacuo. To the residue was added diethyl ether and mixture was stirred. After removal of the resulting crystall by filtration, the filtrate was condensed in vacuo and the residue was purified with silica gel chromatography to give tert-butyl(4S)-4-{[(benzyloxy)carbonyl]amino}-5-bromopentanoate (4.5 g, 80%).
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