Dosmalfate is obtained in a multistep synthesis: The treatment of anhydrous 5-ethyl-2-methylpyridine (I) with chlorosulfonic acid (II) affords 5-ethyl-2-methylpyridine sulfur trioxide complex (III). Heating 1 mol of diosmin (IV) with 7 mol of (III) gives diosmin heptakis(hydrogensulfate) 5-ethyl-2-methylpyridinium salt (V), which by treatment with aqueous sodium hydroxide yields the diosmin heptakis(hydrogensulfate) sodium salt. Finally, the reaction of the sodium salt in an aqueous medium with an aqueous aluminum hydroxychloride solution yields the diosmin heptakis(hydrogensulfate) aluminum complex.