To a mixed solution of (2,2-diethoxyethyl)((6-fluoropyridin-2-yl)methyl)amine (514 mg, 2.12 mmol) described in Production Example 1-1-1 and DMF (10 mL) were added a commercially available product of (2S)-3-(4-(tert-butoxy)phenyl)-2-(((9H-fluoren-9-ylmethoxy)carbonyl)amino)propanoic acid (886 mg, 2.12 mmol), triethylamine (355 μL, 2.54 mmol) and HATU (968 mg, 2.54 mmol) at room temperature. The resultant mixture was stirred at room temperature for 45 minutes. Water was added to the reaction mixture, and the resultant mixture was then extracted with ethyl acetate. An organic layer was washed with water and saturated brine, was then dried over anhydrous magnesium sulfate, and was then filtrated. The solvent was evaporated under a reduced pressure, and the resultant residue was purified by silica gel column chromatography (heptane:ethyl acetate=1:1 and then ethyl acetate) to give the title compound (1.37 g, yield: 94%).
