A solution of 816 mg of 4-hydroxymethyl-5-((Z)-2-tritylthioethen-1-yl)thiazole prepared in step e) in Example 1 in 25 ml of THF was cooled in ice, and 0.301 ml of triethylamine and 0.157 ml of thionyl chloride were added to the cooled solution under an argon atmosphere. The mixture was stirred at the same temperature for 20 min, brine was then added to the reaction solution, and the mixture was adjusted to pH 8 by the addition of sodium bicarbonate water. The mixture was extracted twice with ethyl acetate. The organic layers were combined, were washed with brine, were dried over anhydrous magnesium sulfate, were filtered, and were concentrated under the reduced pressure. The residue was purified by column chromatography on silica gel (hexane:ethyl acetate=5:1 to 1:1) to give 512 mg of 4-chloromethyl-5-((Z)-2-tritylthioethen-1-yl)thiazole.
