Synthesis of [14C]imidazole ring labeled metiamide, cimetidine and impromidine

The radiosynthesis of imidazole ring labeled [14C]metiamide, [14C]cimetidine and [14C]impromidine are described involving the reaction of the key common intermediate 2-[[(4-methyl-1H-[2-14C]imidazol-5-yl)methyl]thio]ethanamine (5) with methyl isothiocyanate, dimethyldithiocyanoiminocarbonate/methylamine and the novel dihydroimidazodiazepine (8), respectively. The ring labeled precursor (5) was prepared in five steps from potassium [14C]cyanide in an overall radiochemical yield of 63%, and having a specific activity of 9.3 mCi/mmol.