4-methoxyphenylacetyloxymethyl difluoromethanesulfonic acid sodium salt 、 、 Diphenylmethylphenylsulfonium trifluoromethanesulfonic acid sodium salt 以produced in <1> of Synthesis Example 4的产率得到4-Methoxyphenylacetic acid 2,2-difluoro-2-sulfoethyl ester diphenylmethylphenylsulfonium salt