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800 ml of a solution of 52.4 ml of oxalyl chloride in methylene chloride was cooled to −78° C., 53.2 ml of DMSO was added dropwise to the solution, and the mixture was stirred at −78° C. for 0.5 hour. A solution of 75.5 g of benzyl 3-hydroxypiperidine-1-carboxylate dissolved in 200 ml of methylene chloride was added dropwise to the mixture, and further 293 ml of triethylamine was added dropwise to the same, and the mixture was stirred for 16 hours while a temperature thereof was gradually raised to room temperature. To the reaction mixture were added a saturated aqueous sodium bicarbonate solution and chloroform, the mixture was stirred and the liquids were separated. The organic layer was dried and concentrated to obtain 83.7 g of 1-benzyloxycarbonyl-3-piperidone. MS•APCI (m/z): 234 [M+H]+ (3) To a solution of 83.7 g of 1-benzyloxycarbonyl-3-piperidone dissolved in 1.2 liters of methylene chloride was added 55.0 g of (R)-(+)-1-(1-naphthyl)ethylamine, and after the mixture was stirred at room temperature for 2 hours, 69 ml of acetic acid and 160 g of sodium triacetoxy borohydride were added to the mixture, and the mixture was stirred at room temperature for 15 hours. To the reaction mixture was added an aqueous sodium hydroxide to make the mixture basic, and then, chloroform was added to the mixture, the mixture was stirred and the liquids were separated. The organic layer was dried and concentrated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate=4:1→0:1) to obtain 98.7 g of benzyl 3-[(R)-1-(naphthalen-1-yl)ethylamino]piperidine-1-carboxylate. MS•APCI (m/z): 389 [M+11]+ (4) To a solution of 40.95 g of triphosgene dissolved in 800 ml of methylene chloride was added dropwise a mixed solution containing 80.6 g of benzyl 3-[(R)-1-(naphthalen-1-yl)ethylamino]piperidine-1-carboxylate and 86.6 ml of triethylamine dissolved in 200 ml of methylene chloride at 0° C., and the mixture was stirred at room temperature for 16 hours. To the reaction mixture was added water, the mixture was stirred and the liquids were separated. The organic layer was dried and concentrated, and the residue was washed with 200 ml of diethyl ether, and the crystal collected by filtration was recrystallized from chloroform and diethyl ether to obtain 48.9 g of benzyl (R)-3-[chlorocarbonyl-(R)-1-(naphthalen-1-yl)ethylamino] piperidine-1-carboxylate.

1. stirringthe mixture was stirred at room temperature for 15 hours
2. stirringthe mixture was stirred
3. customthe liquids were separated
4. customThe organic layer was dried
5. concentrationconcentrated
6. customthe residue was purified by silica gel column chromatography (hexane:ethyl acetate=4:1→0:1)