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In 4.5 ml of methylene chloride were dissolved 200 mg (0.81 mmol) of 2-(p-toluenesulfonyloxy)-1,3-propanediol and 206 mg (0.91 mmol) of (2E,4E)-5-[4-(trifluoromethyl)phenyl]-2,4-pentadienal, and 15 mg of p-toluenesulfonic acid and 0.8 g of molecular sieves 4A were added to the solution, followed by stirring of the resulting mixture at 0° C. for 1 hour. An aqueous sodium hydrogencarbonate solution was added to the reaction mixture and the mixture was stirred for 10 minutes. Then, the molecular sieves were removed by filtration and the filtrate was extracted with methylene chloride. The oil obtained by evaporation of the solvent was separated by preparative thin layer chromatography of silica gel (developing solvent: 20% ethyl acetate-hexane) to obtain 107 mg (yield: 29%) of a trans isomer having less polarity and 153 mg (yield: 42%) of a cis isomer having higher polarity as an oil, respectively.

1. additionwere added to the solution
2. stirringthe mixture was stirred for 10 minutes
3. customThen, the molecular sieves were removed by filtration
4. extractionthe filtrate was extracted with methylene chloride
5. customThe oil obtained by evaporation of the solvent
6. customwas separated by preparative thin layer chromatography of silica gel (developing solvent: 20% ethyl acetate-hexane)
7. customto obtain 107 mg (yield: 29%) of a trans isomer