A tetrahydrofuran (50 ml) solution of 2-ethoxy-1,7,8-trifluoronaphthalene (9.4 g) was cooled to −60° C. Then, a 1.58 M butyllithium/hexane solution (47 ml) was added dropwise to this solution, followed by stirring for 2 hours. A tetrahydrofuran (50 ml) solution of trans-4-(trans-4-butylcyclohexyl)cyclohexylacetoaldehyde (13.2 g) was added dropwise at −50° C. . After stirring for 2 hours, the reaction temperature was increased to 0° C. 10% hydrochloric acid was added to the reaction solution. The reaction solution was extracted with ethyl acetate, washed with brine, and concentrated. The residue was recrystallized from ethyl acetate, and 7-ethoxy-3-[2-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-1-hydroxyethyl]-1,2,8-trifluoronaphthalene was obtained.
