Diisopropylethylamine → HCID 86648556, compound

tert-Butyl cis(±)-4-amino-3-azidopiperidine-1-carboxylate obtained in Example (81a) (about 0.29 mmol) was dissolved in dichloromethane (4 mL). Diisopropylethylamine (0.2 mL, 1.15 mmol) and 4-chloro-5-ethyl-1H-imidazole-2-carbonyl chloride obtained in Example (81b) (about 0.29 mmol) were added, followed by stirring for 2.5 hours. Dichloromethane was added to the reaction solution, and the organic layer was washed with 1 N hydrochloric acid, a 1 N aqueous sodium hydroxide solution and brine, and dried over anhydrous sodium sulfate. The residue obtained by concentration under reduced pressure was purified by silica gel column chromatography (elution solvent: hexane/ethyl acetate=90/10, 70/30, 55/45) to obtain 90.4 mg of the title compound (78%).