Cl.[CH3:2][O:3][C:4](=[O:11])[C@H:5]([CH2:7][CH:8]([CH3:10])[CH3:9])[NH2:6].C(=O)([O-])[O-].[Na+].[Na+].Cl[C:19]([O:21][CH2:22][C:23]1[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1)=[O:20]>O1CCOCC1>[CH3:2][O:3][C:4](=[O:11])[C@H:5]([CH2:7][CH:8]([CH3:10])[CH3:9])[NH:6][C:19]([O:21][CH2:22][C:23]1[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1)=[O:20]To a solution of leucine methyl ester hydrochloride (5.0 g, 27.5 mmol) in 1,4-dioxane (50 mL) was added sodium carbonate (30.3 mL, 2M in water) followed by benzyl chloroformate (4.69 g, 27.5 mmol). The mixture stirred at room temperature for 24 hours when partitioned between ethyl acetate and water. The organic layer was collected, dried (MgSO4), filtered and concentrated to give the title compound as a colorless oil (7.67 g, 100%). 1HNMR (400 MHz, CDCl3) δ7.39 (m, 5H), 5.38 (d, 2H), 5.12 (s, 2H), 4.42 (m, 1H), 3.75 (s, 3H), 1.73-1.50 (m, 3H), 0.94 (m, 6H).
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