Under a nitrogen atmosphere, zinc powder (0.295 g, 4.513 mmol) and zinc chloride (0.1 g, 0.752 mmol) were added to a DMF (5 mL) solution of compound (56) (0.5 g, 1.504 mmol), and the resultant mixture was agitated at 80° C. for 8 hours. The reaction mixture was quenched with 20 mL of 1N hydrochloric acid aqueous solution, and extracted with 10 mL of toluene three times. Combined organic layers were washed with a saturated aqueous solution of sodium hydrogencarbonate, water and saturated brine, and then dried over magnesium sulfate, and a solvent was distilled off by an evaporator. The residue was purified by silica gel column chromatography, and thus 2-ethoxy-1,8-difluoro-7-propyl-9,10-dihydrophenanthrene-9,10-diol (57) (0.3 g, yield 59.7%) was obtained.
