24424-99-5

1187173-43-8

923009-50-1

Preparation of Example 44: tert-butyl 1-oxo-2,7-diazaspiro[4.5]decane-7-carboxylate (P44) was synthesized as follows: 2,7-diazaspiro[4.5]decan-1-one hydrochloride (600 mg, 3.15 mmol) was dissolved in 30 mL of dichloromethane (DCM). To this solution, triethylamine (TEA, 1.98 mL, 14.18 mmol) and di-tert-butyl dicarbonate (Boc2O, 895 mg, 4.10 mmol) were added sequentially. The reaction mixture was stirred at room temperature for 4 hours. After completion of the reaction, it was quenched by addition of water and the organic and aqueous layers were separated. The organic layer was washed with aqueous ammonium chloride (NH4Cl), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent to afford the target product tert-butyl 1-oxo-2,7-diazaspiro[4.5]decane-7-carboxylate (P44, 830 mg, quantitative yield) as a colorless oil. Mass spectrum (ESI) m/z: 255.2 [M + H]+.