Under a nitrogen atmosphere, to a solution of 2′-fluoro-5′-methoxy-[1,1′-biphenyl]-2,4-diol (14.6 g) and 2,6-dimethylpyridine (10.2 mL) in toluene (100 mL) was added triisopropylsilyl trifluoromethanesulfonate (21.1 mL) at −15° C., and the mixture was stirred at −15° C. for 20 min. To the reaction mixture was added 1N hydrochloric acid, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure and the residue was purified by silica gel column chromatography (ethyl acetate/hexane) to give the title compound as a white amorphous solid.
