In a mixture of 0.4 mL of toluene and 7 mL of a 50% (W/V) aqueous sodium hydroxide solution was suspended 0.54 g of 2-(1-benzothiophen-5-yl)-1-ethanol, followed by adding thereto 1.45 g of 1-(3-chloropropyl)-3-(trityloxy)azetidine oxalate and 0.03 g of tetra-n-butylammonium bromide, and the resulting mixture was refluxed for 7 hours. After the reaction mixture was cooled, water and toluene were added thereto and the organic layer was separated. The organic layer was washed with a saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, and then distilled under reduced pressure to remove the solvent. The residue was purified by a column chromatography (eluent; chloroform:methanol=75:1) to obtain 0.59 g of 1-{3-[2-(1-benzothiophen-5-yl)ethoxy]propyl}-3-(trityloxy)azetidine as a light-yellow oil.
