Synthesis of a new tricyclic tetraazatriacetic acid as ligand for gadolinium(III)

Polyazapolycarboxylic acids are known to be efficient ligands for the development of gadolinium-based contrast agents used in magnetic resonance imaging (MRI). Given that rigidification of the ligand structure seems to be an important structural parameter to increase the relaxivity of the corresponding gadolinium complex, we have synthesized a new tricyclic tetraazatriacetate ligand from commercially available trans-2-aminocyclohexanol. In the synthetic routes described here, the 2-nitrobenzenesulfonamide chemistry was used to selectively functionalize the polyamine precursors.