To a mixture of 4′-{[4-(trans-3-acetylcyclobutyl)-5-oxo-7-propyl-4,5-dihydro[1,2,4]triazolo[1,5-a]pyrimidin-6-yl]methyl}biphenyl-2-carbonitrile (1.3 g), 30% hydrogen peroxide water (3.5 g) and chloroform (20 mL) was gradually added trifluoroacetic acid anhydride (7.7 mL) at room temperature, and the reaction mixture was warmed to 60° C. and stirred for 24 hr. Saturated aqueous sodium hydrogen carbonate and sodium thiosulfate were added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The obtained residue was dissolved in tetrahydrofuran (10 mL) and methanol (10 mL), 1N aqueous sodium hydroxide solution (5 mL) was added, and the mixture was stirred at room temperature for 30 min. 1N Aqueous hydrochloric acid solution was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography to give the title compound as a colorless solid (0.28 g, 23%).
