Exploring privileged structures: The combinatorial synthesis of cyclic peptides

Head-to-tail cyclic peptides have been reported to bind to multiple, unrelated classesof receptor with high affinity. They may therefore be considered to beprivileged structures. This review outlines the strategies by which bothmacrocyclic cyclic peptides and cyclic dipeptides or diketopiperazines havebeen synthesised in combinatorial libraries. It also briefly outlines someof the biological applications of these molecules, thereby justifying theirinclusion as privileged structures.