Synthesis of a technetium-99m-labeled thymidine analog: a potential HSV1-TK substrate for non-invasive reporter gene expression imaging

{2-[5-(2′-Fluoro-2′-deoxyuridin-5-yl)pent-4(E)-enyl] [2-(2-mercaptoethyl)aminoethyl]aminoethanethiolato(3)-N,N′,S,S′}oxo-[99mTc]technetium(V), a potential viral thymidine kinase substrate, was synthesized by coupling 2′-fluoro-2′-deoxyuridine analog with a N2S2 radiometal chelator, followed by [Tc-99m]technetium conjugation. The chemical structure of the radioactive probe was characterized by 1H NMR and high resolution MS using Re-188 conjugated mimics. The radiochemical purity and yield were identified as 98% and 42%, respectively.