Disulfide and amide-bridged cyclic peptide analogues of the VEGF81-91 fragment: Synthesis, conformational analysis and biological evaluation

The design, synthesis, conformational studies and binding affinity for VEGFR-1 receptors of a collection of linear and cyclic peptide analogues of the β-hairpin fragment VEGF81-91 are described. Cyclic 11-mer peptide derivatives were prepared from linear precursors with conveniently located Cys, Asp or Dap residues, by the formation of disulfide and amide bridges, using solid-phase synthesis. Molecular modelling studies indicated a tendency to be structured around the central β-turn of the VEGF81-91 β-hairpin in most synthesized cyclic compounds. This structural behavior was confirmed by NMR conformational analysis. The NHCO cyclic derivative 7 showed significant affinity for VEGFR-1, slightly higher than the native linear fragment, thus supporting the design of mimics of this fragment as a valid approach to disrupt the VEGF/VEGFR-1 interaction.