ABSTRACT
We report herein the first systematic crystal structural investigation of azaproline incorporated in homo- and heterochiral diprolyl peptides. The X-ray crystallography data of peptides 1-5 illustrates that stereodynamic nitrogen in azaproline adopted the stereochemistry of neighbouring proline residue without depending on its position in the peptide sequence. Natural bond orbital analysis of crystal structures indicates OazPro -C'Pro of peptides 4 and 5 participating in nâπ* interaction with stabilization energy about 1.21-1.33â kcal/mol. Density functional theory calculations suggested that the endo-proline ring puckering favoured over exo-conformation by 6.72-7.64â kcal/mol. NBO and DFT data reveals that the nâπ* interactions and proline ring puckering stabilize azaproline chirality with the neighbouring proline stereochemistry. The CD, solvent titration, variable-temperature and 2D NMR experimental results further supported the crystal structures conformation.
Subject(s)
Nitrogen , Proline , Protein Conformation , Proline/chemistry , Peptides/chemistry , Magnetic Resonance SpectroscopyABSTRACT
We report the synthesis and biological and physiochemical properties of a series of azaGly-appended peptidomimetics. We have developed a simple and facile synthesis for azapeptides on solid support without any side reaction. The azaGly is inserted by in situ reaction of disuccinimidyl carbonate with free amine followed by treatment of hydrazine hydrate at room temperature. The new series of peptidomimetics was prepared by azaGly scanning of heptapeptide Arg-Pro-Arg-Nle-Tyr-Dap-Nle (Akt-01), a GSK-3ß-derived Akt inhibitor. The azaGly-appended peptides showed significant improvement in biological activity and serum stability, with retention of conformation as evidenced by NMR and CD studies. The results clearly demonstrate that azaGly-appended peptides are new peptidomimetics. Their synthesis makes this approach highly useful for the development of novel peptidomimetics of therapeutic potential.
