Triethylamine (0.015 mL, 0.107 mmol) was added to a solution of (3R,6S)-3-amino-1-(2-methoxyethyl)-6-phenylazepan-2-one (28 mg, 0.107 mmol) and 4-nitrophenyl chloroformate (22 mg, 0.107 mmol) in tetrahydrofuran (2 mL) at 0° C. After 30 min, 2-oxo-1-(4-piperidinyl)-2,3-dihydro-1H-imidazo[4,5-b]pyridine dihydrochloride (37 mg, 0.128 mmol), diisopropylethylamine (0.074 mL, 0.427 mmol) and dichloromethane (2.5 mL) were added and the mixture allowed to warm to ambient temperature. After 18 h, saturated aqueous sodium carbonate was added and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated aqueous sodium carbonate (3×), saturated brine, dried over magnesium sulfate, filtered and concentrated. Purification by silica gel chromatography (100% dichloromethane→93% dichloromethane/methanol) gave the title compound (45 mg). MS 507.2737 (M+1).
