To a solution of 1,1-dimethylethyl 3-[hydroxy(diphenyl)methyl]-1-piperazine carboxylate (0.50 g, 1.4 mmol) in tetrahydrofuran (5 mL) were sequentially added diisopropylethylamine (2 mL) and chloroacetyl chloride (0.46 g, 4.1 mmol) with ice cooling, and the mixture was stirred for 4 hours while elevating the temperature to room temperature. To the reaction solution was added ethyl acetate, and the resulting mixture was washed with water, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified with silica gel column chromatography (hexane:ethyl acetate=4:1) to obtain the title compound (0.28 g, yield 46%).
