Stereodivergent synthesis of 5-aminopipecotic acids and application in the preparation of a cyclic RGD peptidomimetic as a nanomolar alpha(v)beta(3) integrin ligand

A stereodivergent strategy was devised to obtain enantiopure cis and trans 5-aminopipecolic acids (5-APAs) in suitably protected forms to be employed in peptide synthesis as conformationally constrained alpha- and delta-amino acids. The cis isomer was used as a delta-amino acid to construct a cyclic RGD-containing peptidomimetic, the ability of which to compete with biotinylated vitronectin for binding with the isolated alpha(v)beta(3) integrin was measured (IC50 = 4.2 +/- 0.9 nM). A complete H-1 NMR and computational conformational analysis was performed to elucidate the reasons for the high affinity of this cyclic peptidomimetic in comparison with cilengitide.