To a solution of 7-[4-(2-butoxyethoxy)phenyl]-N-[4-[hydroxy(2-pyridyl)methyl]-3-trifluoromethylphenyl]-1-(2,2,2-trifluoroacetyl)-2,3-dihydro-1-benzazepine-4-carboxamide (355 mg) in dichloromethane (10 ml) was added 3-chloroperbenzoic acid (205 mg), and the mixture was stirred overnight under nitrogen atmosphere. To the mixture was added water, and the mixture was extracted with ethyl acetate, washed with an aqueous solution of saturated sodium bicarbonate and saturated brine, and dried over magnesium sulfate. The solvent was distilled off under reduced pressure and the obtained residue was purified by silica gel column chromatography (ethyl acetate), to give 7-[4-(2-butoxyethoxy)phenyl]-N-[4-[hydroxy(1-oxidopyridin-2-yl)methyl]-3-trifluoromethylphenyl]-1-(2,2,2-trifluoroacetyl)-2,3-dihydro-1-benzazepine-4-carboxamide (176 mg) as colorless amorphous.
