ethyl (4E)-3-methyl-5-[4-(trifluoromethyl)phenyl]-2,4-pentadienoate → (2E,4E)-3-Methyl-5-[4-(trifluoromethyl)phenyl]-2,4-pentadien-1-ol

After a solution in which 150 mg (0.53 mmol) of ethyl (4E)-3-methyl-5-[4-(trifluoromethyl)phenyl]-2,4-pentadienoate ((2E)/(2Z)=5/1) as described in Reference example 8 were dissolved in 2 ml of toluene was stirred at 0° C., 0.7 ml (1.06 mmol) of a 1.SM diisobutyl aluminum hydride-toluene solution were added to the solution. After 20 minutes, ice-water was added to the reaction mixture and the mixture was stirred for 10 minutes. The insolubles were removed by filtration using Celite and the filtrate was extracted with ethyl acetate and dried, followed by evaporation of the solvent to obtain an oil. The oil was subjected to column chromatography using 5 g of silica gel and eluted with a mixed solvent of 30 to 40% ethyl acetate-hexane to obtain 90 mg of the title compound as an oil.