Thiourea derivatives as chelating agents for bioconjugation of rhenium and technetium.

Potential tetradentate thiocarbamoylbenzamidine derivatives H4 L have been synthesized from the corresponding benzimidoyl chlorides and triglycine. They are suitable chelating agents for the oxidotechnetium(v) and oxidorhenium(v) cores and form stable, neutral [MO(HL)] complexes with an equatorial SN3 coordination sphere and an additional, uncoordinated carboxylic group, which can be used for bioconjugation. Representatives of the rhenium and99 Tc products have been isolated and analyzed with spectroscopic methods and X-ray diffraction. Bioconjugates of these complexes with angiotensin-II have been synthesized and structurally characterized. Analogous99m Tc complexes have been produced and tested in vitro and in vivo. The experiments confirm a considerable stability for the [99m Tc(HL)] product as well as for its bioconjugate and recommend this class of compounds for further bioconjugation studies towards clinical applications.