Cyclic DGR-peptidomimetic containing a bicyclic reverse turn inducer as a selective αvβ5 integrin ligand

3-Aza-6,8-dioxabicyclo[3.2.1]octane-based amino acids as reverse turn inducers have been introduced into cyclic peptidomimetics containing the RGD or DGR retro-sequence, in order to achieve a stereochemical scanning of the binding capability of the resulting molecules towards αvβ3 and αvβ5 integrins, resulting in retro-inverso DGR peptides as micromolar ligands. A comparative analysis between the conformational preferences of 4 and of its isomer 3, having the opposite RGD sequence, was reported with respect to the binding activity, giving insight into the factors affecting the preferential binding of 4 to the αvβ5 integrin.