[NH2:1][C@H:2]([C:4]1[CH:13]=[CH:12][C:7]([C:8]([O:10][CH3:11])=[O:9])=[CH:6][CH:5]=1)[CH3:3].[OH:14][C@H:15]([CH:19]([CH3:21])[CH3:20])[C:16](O)=[O:17].ON1C2C=CC=CC=2N=N1.C(N(CC)CC)C.Cl.CN(C)CCCN=C=NCC>C(Cl)Cl>[OH:14][C@H:15]([CH:19]([CH3:21])[CH3:20])[C:16]([NH:1][C@H:2]([C:4]1[CH:13]=[CH:12][C:7]([C:8]([O:10][CH3:11])=[O:9])=[CH:6][CH:5]=1)[CH3:3])=[O:17]A mixture of 4-[(1S)-1-aminoethyl]-benzoic acid, methyl ester (5.8 g; 49.1 mmol), (2R)-2-hydroxy-3-methyl-butanoic acid (9.3 g; 51.9 mmol), 1-hydroxybenzotriazole (0.82 g; 6.1 mmol), and triethylamine (22 mL; 158 mmol) in CH2Cl2 (120 mL) is treated with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (14.2 g; 74.1 mmol). The cloudy mixture is stirred at room temperature overnight. The reaction mixture is washed with 1N HCl (2×150 mL) then brine. The organic layer is dried over MgSO4, filtered, concentrated, and dried under high vacuum to provide the title compound as a white solid (10.24 g, 75%). This material is used in the next step without further purification. MS (m/z): 280.0 (M+1).
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