[CH2:1]([O:3][C:4](=[O:27])[C@H:5]([NH:19]C(OC(C)(C)C)=O)[CH2:6][CH2:7][C:8](=O)[C:9]1[CH:14]=[C:13]([F:15])[C:12]([F:16])=[C:11]([F:17])[CH:10]=1)[CH3:2].Cl.C(OCC)(=O)C>C(OCC)(=O)C>[CH2:1]([O:3][C:4]([C@H:5]1[CH2:6][CH2:7][C:8]([C:9]2[CH:14]=[C:13]([F:15])[C:12]([F:16])=[C:11]([F:17])[CH:10]=2)=[N:19]1)=[O:27])[CH3:2]To a solution of (R)-2-t-butoxycarbonylamino-5-oxo-5-(3,4,5-trifluorophenyl)valeric acid ethyl ester (22.2 g) in ethyl acetate (30 mL) was added 4 N hydrochloric acid/ethyl acetate (163 mL), and the resultant solution was stirred at room temperature for 3 hours. Solvent was removed by distillation under reduced pressure, and the resulting residue was diluted with ethyl acetate and sodium bicarbonate water. The organic layer was partitioned, washed with brine, and then dried over anhydrous magnesium sulfate. Solvent was removed by distillation under reduced pressure, to thereby obtain the titled compound (12.4 g). The physical properties of this crude product were as follows.
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