Strategic Evaluation of the Traceless Staudinger Ligation for Radiolabeling with the Tricarbonyl Core

The traceless Staudinger Ligation with its two variants is a powerful biorthogonal conjugation method not only for the connection of biomolecules, but also for the introduction of fluores-cence or radiolabels under mild reaction conditions. Herein, the strategic evaluation of the traceless Staudinger Ligation for Radiolabeling 99mTc using the [Tc(CO)₃] core was presented. A convenient and high-yielding three-step synthesis procedure of dipicolylamine-based phos-phanols as ligands for the mild radiolabeling was developed. The labeling was accomplished using a tricarbonyl kit and ^99mTc-pertechnetate generator eluate showing 87% radiochemical conversion. The respective rhenium-based, non-radioactive reference compounds were synthe-sized using (Et₄N)₂[Re(CO)₃Br₃] as precursor. All products were analyzed by NMR, MS and ele-mental analysis. Additional XRD analyses were performed.