To a solution of 3-acetyl-2-(4-acetylbenzyl)-6-bromo-4-phenyl-2H-isoquinolin-1-one (297 mg) in THF (10 ml) was added methyl magnesium bromide (1M tetrahydrofuran solution, 1.89 ml) under ice-cooling and the mixture was stirred under ice-cooling for 1 hr. The reaction solution was poured into saturated aqueous ammonium chloride solution, extracted with ethyl acetate, washed with brine and dried by adding sodium sulfate. The solvent was evaporated under reduced pressure and the obtained residue was purified by silica gel column chromatography (n-hexane/ethyl acetate=9/1→3/2) to give the title compound (258 mg, 83%).
