The synthesis and properties of Gla- and Phe-containing analogues of cyclic RGD pentapeptides

Cyclopentapeptides containing the Arg-Gly-Asp motif have been synthesised using solid-phase assembly of side-chain-protected linear precursors, followed by solution-phase cyclisation. The replacement of the Asp residue by γ-carboxyglutamic acid (Gla) is a novel feature which gives rise to an analogue which inhibits cell adhesion, yet its congeners do not show activity in binding assays with recombinant integrin receptors. NMR techniques support a β/γ-turn conformation in most of the analogues.