3-(1-tert-Butoxycarbonyl-1-methylethoxy)phenylacetic acid (250 mg, 0.849 mmol) was dissolved in solvent mixture of dimethylformamide (10 μL)-dichloromethane (6 mL). Subsequently, oxalyl chloride [(COCl)2 (148 μL, 1.70 mmol)] was added at 0° C., the mixture was stirred for one hour at room temperature. The reaction mixture was added to a solution obtained by dissolving cyclohexylamine (0.97 mL, 8.49 mmol) in dichloromethane (1 mL) at 0° C., the mixture was stirred for one hour at room temperature. Chloroform was added to the reaction mixture. Washing was performed sequentially with 1M hydrochloric acid, water, and saturated brine, followed by drying over sodium sulfate. The mixture was subjected to concentration under reduced pressure and purification by silica gel column chromatography (chloroform/methanol=50/1), whereby the target compound was obtained (280 mg, 0.746 mmol, 87.8%).
