Preparation of 14C- and 18O-labeled 2-[2-methoxy-4-(methylsulfinyl)phenyl]-1H-imidazo[4,5-c]-pyridine hydrochloride (LY175326), a cardiotonic with inotropic and vasodilator activities

Two different forms of 14C‐labeled 2‐methoxy‐4‐(methylthio) benzoic acid were prepared and employed in the synthesis of 14C‐labeled 2‐[2‐methoxy‐4‐(methylsulfinylphenyl]‐lH‐imidazo‐[4,5‐c]pyridine hydrochloride (LY175326), a cardiotonic with inotropic and vasodilator activities that is currently in clinical trials. The synthetic procedures described in this report allowed the introduction of the 14C‐label in the antepenultimate step. Additionally, an 18O‐labeled form of LY175326 was synthesized to facilitate kinetic analysis of the formation of its sulfide and sulfone metabolites.