A mixture of 6.6 g of ethyl 3-(1-adamantyl)-2,2-difluoro-3-hydroxypropionate, prepared in Synthesis Example 1-11, 50 g of 1,4-dioxane, 8.0 g of 25 wt % sodium hydroxide, and 20 g of water was stirred for 2 hours. To the reaction solution, 2.0 g of 35 wt % hydrochloric acid was added, and then 53 g of an aqueous solution of 4-fluorophenyldiphenylsulfonium chloride and 100 g of methylene chloride were added. After stirring for 30 minutes, the organic layer was taken out, washed with water, and concentrated under reduced pressure. Methyl isobutyl ketone was added to the concentrate, which was concentrated again. Diisopropyl ether was added to the concentrate for crystallization. The resulting solid was dried in vacuum, obtaining 6.2 g of the target compound, 4-fluorophenyldiphenylsulfonium 3-(1-adamantyl)-2,2-difluoro-3-hydroxypropionate as white crystals (yield 57%).
