In a round-bottomed flask, 2-(6-fluoro-3-methylsulfanyl-imidazo[1,5-a]pyridin-1-yl)-5-(2-trimethylsilanyl-ethoxymethyl)-5H-pyrrolo[2,3-b]pyrazine-7-carboxylic acid [(R)-2-(3-cyano-azetidin-1-yl)-1-methyl-2-oxo-ethyl]-amide (105 mg, 0.155 mmol) was dissolved in dichloromethane (4 ml). The solution was cooled to 0° C. and m-CPBA (75%, 79 mg, 0.343 mmol) was added. The ice bath was removed and the reaction mixture was stirred at room temperature overnight. Additional m-CPBA (75%, 36 mg, 0.155 mmol) was added and the reaction mixture was stirred at room temperature for 30 min. A solution of 10% aqueous Na2S2O3 (3 ml) was added and the biphasic mixture was stirred at room temperature for 1 h. The reaction mixture was diluted with water and extracted with dichloromethane. The organic layer was washed with saturated aqueous NaHCO3. The aqueous layer was extracted dichloromethane (2×). The combined organic layers were dried over sodium sulfate, filtered and concentrated. The residue was chromatographed over silica gel with MeOH/CH2Cl2/0.5% NH4OH (gradient 0-2.5% MeOH) to afford 25 mg (25%) of 2-(6-fluoro-3-methanesulfonyl-imidazo[1,5-a]pyridin-1-yl)-5-(2-trimethylsilanyl-ethoxymethyl)-5H-pyrrolo[2,3-b]pyrazine-7-carboxylic acid [(R)-2-(3-cyano-azetidin-1-yl)-1-methyl-2-oxo-ethyl]-amide as a light brown oil.
