The condensation of 2-(trifluoromethyl)benzylamine (I) with thiodiglycolic anhydride (II) affords the mono-amide (III). Subsequent Fischer esterification of acid (III) with MeOH and H2SO4 gives rise to the amide-ester (IV). Oxidation of the sulfide group of (IV) by means of m-chloroperbenzoic acid produces a mixture of sulfoxide (V) and the analogous sulfone (VI), which are separated by column chromatography. Finally, the desired sulfone ester (VI) is hydrolyzed under basic conditions to the corresponding carboxylic acid.