Hexadentate bispidine radiocopper complexes: emerging opportunities for the application in nuclear medicine

The advantageous properties of numerous 3,7-diazabicyclo[3.3.1]nonane (bispidine) derivatives have attracted much attention and caused intensive research efforts in different directions. An attractive goal represents the development of target-specific radiopharmaceuticals. For this purpose, bifunctional chelating agents are needed which have to show fast metal complexation kinetics, form complexes with high in vitro and in vivo stability and contain a group that can be linked to biomolecules. In this regard, hexadentate bispidines 1 – 3 containing pyridine units in C2, C4, N3, and N7 position have been shown to rapidly form stable radiocopper (such as ⁶⁴Cu and ⁶⁷Cu) complexes. Furthermore, the carboxylic groups of ligand 3 provide the possibility for coupling bio-molecules.