Triethylamine (11.5 mg, 0.104 mmol) was added to a solution (3R,6S)-3-amino-6-(2,3-difluorophenyl)-1-(2,2,2-trifluoroethyl)azepan-2-one (32 mg, 0.104 mmol) and p-nitrophenyl chloroformate (20 mg, 0.104 mmol) in tetrahydrofuran (1 mL) at 0° C. After 0.5 h, triethylamine (42 mg, 10.416 mmol) and 4-piperidin-4-ylpyridazin-3(2H)-one (19 mg, 0.104 mmol) were added and the mixture was allowed to warm to ambient temperature. After 1 h, the mixture was quenched with water, extracted with ethyl acetate, and washed with 1 N NaOH solution. The combined organic layer was dried over sodium sulfate, filtered, and concentrated. Purification by silica gel chromatography (1% methanol/dichloromethane→10% methanol/dichloromethane) gave the title compound (30 mg). MS 528.1999 (M+1).
