The mesylation of aniline (I) with methanesulfonyl chloride gives the sulfonamide (II), which is condensed with 1-acetylpiperidine-4-carbonyl chloride (III) by means of AlCl3 in dichloromethane to give N-[4-(1-acetylpiperidin-4-ylcarbonyl)phenyl]methanesulfonamide (IV). Deacetylation of (IV) with HCl in water yields the piperidine (V), which is finally condensed with 2-methyl-6-vinylpyridine by means of sodium acetate in methanol - water. The same procedure has been performed with [14C]-labeled aniline in order to obtain [14C]-labeled E-4031.