Cl.[NH2:2][C@@H:3]([CH2:8][CH:9]1[CH2:14][CH2:13][CH2:12][CH2:11][CH2:10]1)[C:4]([O:6][CH3:7])=[O:5].C(=O)([O-])[O-].[K+].[K+].[CH2:21](Br)[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1>CN(C)C=O>[CH2:21]([N:2]([C@@H:3]([CH2:8][CH:9]1[CH2:14][CH2:13][CH2:12][CH2:11][CH2:10]1)[C:4]([O:6][CH3:7])=[O:5])[CH2:8][C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1)[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1Methyl 2(S)-amino-3-cyclohexylpropionate hydrochloride (150 g) was dissolved in N,N-dimethylformamide (1200 ml). Thereto was added pulverized potassium carbonate (330.7 g), and benzyl bromide (254.6 g) was dropwise added to the obtained suspension while stirring. After the dropwise addition, the inner temperature was raised to 50° C., and the reaction mixture was stirred at said temperature for 9 hours. The reaction mixture was cooled and filtered. Water (600 ml) and diisopropyl ether (600 ml) were added to the filtrate for partition, and the organic layer was separated. The water layer was re-extracted with diisopropyl ether (300 ml), and the combined organic layer was washed with 5% hydrochloric acid (600 ml), 5% aqueous sodium hydrogencarbonate (600 ml), and 25% aqueous sodium chloride sequentially and dried over magnesium sulfate. The solvent was distilled away to give 204.6 g of methyl 2(S)-(N,N-dibenzylamino)-3-cyclohexylpropionate.
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