Solid-phase approach to the synthesis of cyclen scaffolds from cyclotetrapeptides

Cyclen derivs., as coordinating ligands, have recovered considerable interest for the development of diagnostic and therapeutic drugs, mimicking the binding site of metalloproteins. We demonstrate that the on-resin redn. of head-to-tail cyclotetrapeptides, anchored to a solid support by the side-chain of a trifunctional amino acid, is an efficient synthetic strategy. The proposed approach leads to the cyclen scaffold still bound to the resin, ready for further decorations.