N-Bromosuccinimide (0.25 g) and azobisisobutyronitrile (0.023 g) were sequentially added to a benzene (6.3 mL) solution of the obtained tert-butyl 2-(2-(methoxymethoxy)-5-methylbenzamido)-4-phenylbenzoate (0.63 g), followed by heating to reflux for 30 minutes. The reaction mixture was cooled to room temperature, and then a saturated aqueous solution of sodium bicarbonate and ethyl acetate were added thereto. The organic layer was separated, washed with a saturated aqueous solution of sodium chloride, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography [eluent: 100-90% hexane/ethyl acetate] to obtain 0.51 g of tert-butyl 2-(5-(bromomethyl)-2-(methoxymethoxy)benzamido)-4-phenylbenzoate as a white solid.
