Addition of methylmagnesium iodide to nitrile (I), followed by hydrolytic treatment, provided ketone (II), which was brominated in CHCl3-MeOH to give bromomethyl ketone (III). Alkylation of thiourea (V) with 3-(dimethylamino)propyl chloride (IV) produced S-alkyl isothiourea (VI). After hydrolysis of (VI) with NaOEt, the intermediate thiol (VII) was condensed with bromoketone (III) to yield the required thioether, which was finally converted to the citrate salt.