Application of click chemistry to the design of ligand systems and functionalization of biomolecules suitable for radiolabelling with the technetium and rhenium tricarbonyl core; ; IAEA radioisotopes and radiopharmaceuticals series; Technetium-99m radiopharmaceuticals : status and trends

As the premier example of a click reaction, the Cu(I) catalysed cycloaddition of azides and terminal alkynes has found tremendous resonance throughout the scientific community. The reaction is characterized by mild reaction conditions, selectivity and the comparatively straightforward preparation of alkyne and azide building blocks. In addition to the numerous applications as a stable link between two chemical/biological components, triazole products are beginning to be recognized as ligands for a wide range of different metals. Combining the coordinative properties of triazole products and favourable reaction conditions, efficient triazole containing chelators for the M(CO)3 cores of technetium and rhenium can be readily synthesized and incorporated into molecules of diagnostic and therapeutic interest in a single step. In situ radiolabelling with technetium rapidly provides access to a set of radiolabelled derivatives for in vitro screening, and the viability of the approach has been demonstrated in vivo by comparing radioconjugates labelled with the tricarbonyl core via structurally analogous imidazole containing and triazole containing chelating systems.