Syntheses of 14C-labelled monoacidic metabolites of dithiopyr

Convenient methods for the selective hydrolysis of the thioester groups of dithiopyr to the corresponding carboxylic acid are described. 2-(Difluoromethyl)-4-(2-methylpropyl)-5-[(methylthio)carbonyl]-6-(trifluoromethyl)-3-pyridine-4-14C-carboxylic acid (2) was obtained by simple potassium hydroxide hydrolysis of 14C-labelled dithiopyr. A more involve strategy was necessary for the preparation of the isomeric carboxylic acid 6-(difluoromethyl)-4-(2-methylpropyl)-5-[(methylthio) carbonyl]-2-(trifluoromethyl)-3-pyridine-4-14C-carboxylic acid (3)