Cl.[CH3:2][O:3][C:4](=[O:8])[C@H:5]([CH3:7])[NH2:6].C(=O)([O-])[O-].[K+].[K+].[CH2:15](Br)[C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1>CN(C=O)C>[CH2:15]([NH:6][C@@H:5]([CH3:7])[C:4]([O:3][CH3:2])=[O:8])[C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1L-alanine methyl ester hydrochloride (15.0 g, 107 mmol) was dissolved in N,N′-dimethylformamide (150 mL), added potassium carbonate (32.5 g, 235 mmol) and benzyl bromide (18.4 g, 107 mmol) and the mixture was stirred at 80° C. overnight. Then, the mixture was reverted to room temperature, the reaction solution was filtered through a pad of celite, extracted with ethyl acetate, washed with water and brine, dried over sodium sulfate, and concentrated in vacuo. The obtained residue was purified by silica-gel column chromatography (hexane/ethyl acetate), and the title compound (12.7 g, 61%) was obtained as a colorless oil.
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