Triethylamine (0.010 mL, 0.027 mmol) was added to a solution of (3R,6S)-3-amino-6-(2,3-difluorophenyl)-1-[2-(methylsulfinyl)ethyl]azepan-2-one (8.9 mg, 0.027 mmol) and 4-nitrophenyl chloroformate (5.4 mg, 0.027 mmol) in tetrahydrofuran (0.700 mL) at 0° C. After 45 min, 2-oxo-1-(4-piperidinyl)-2,3-dihydro-1H-imidazo[4,5-b]pyridine dihydrochloride (7.9 mg, 0.027 mmol) and triethylamine (0.040 mL, 0.108 mmol) were added and the mixture allowed to warm to ambient temperature. After 16 h, the mixture was concentrated. Purification by reverse phase HPLC (C-18, 95% water/acetonitrile→5% water/acetonitrile with 0.1% trifluoroacetic acid) gave the title compound. MS 575 (M+1).
