Design of Functional Chiral Cyclen-Based Radiometal Chelators for Theranostics.

A series of water-soluble chiral cyclen-based chelators with chemical handles for selective targeting have been synthesized (cyclen = 1,4,7,10-Tetraazacyclododecane). Optical studies, relaxivity measurements, and competitive titrations were performed to show the versatility of these chiral chelators. The complexations of L3, L4, and L5 with Lu, Y, Sc and Cu were successfully demonstrated in around 90% to 100% yields. Efficient and rapid radiolabeling of L5 with Lu was achieved under mild conditions with 96% yield. The chelators exhibit near quantitative labeling efficiencies with a wide range of radiometal ions, which are promising for the development of targeting specific radiopharmaceutical and molecular magnetic resonance imaging contrast agents.