The condensation of 4-chloro-2,3-dimethylpyridine N-oxide (I) with 3-methoxypropanol (II) by means of NaH in DMSO gives 4-(3-methoxypropoxy)-2,3-dimethylpyridine N-oxide (III), which is treated with acetic anhydride at 90 C yielding 2-(acetoxymethyl)-4-(3-methoxypropoxy)-3-methylpyridine (IV). The hydrolysis of (IV) with NaOH in ethanol affords 2-(hydroxymethyl)-4-(3-methoxypropoxy)-3-methylpyridine (V), which by treatment with SOCl2 in dichloromethane is converted into 2-(chloromethyl)-4-(3-methoxypropoxy)-3-methylpyridine (VI). The condensation of (VI) with 2-mercaptobenzimidazole (VII) by means of NaOH in ethanol gives 2-[4-(3-methoxypropoxy)-3-methylpyridin-2-ylmethylthio]benzimidazole (VIII), which is oxidized with m-chloroperbenzoic acid in ether - dichloromethane to afford 2-[4-(3-methoxypropoxy)-3-methylpyridin-2-ylsulfinyl]benzimidazole (IX). Finally, this compound is treated wtih aqueous Na2CO3.
A synthesis for [14C]-labeled E-3810 has been described: The cyclization of o-phenylenediamine (I) with [14C]-labeled carbon disulfide (II) by means of aqueous KOH gives the potassium salt of [14C]-2-mercaptobenzimidazole (III), which is treated with acetic acid to obtain the corresponding thiol (IV). The condensation of (IV) with 2-(chloromethyl)-4-(3-methoxypropoxy)-3-methylpyridine (V) by means of NaOH in refluxing ethanol yields [14C]-labeled 2-[4-(3-methoxypropoxy)-3-methylpyridin-3-ylmethylthio]benzimidazole (VI). The oxidation of (VI) with m-chloroperbenzoic acid in dichloromethane affords the corresponding sulfoxide (VIII), which is finally treated with 0.1 N NaOH in ethanol.