Buré, C., Marceau, P., Meudal, H. and Delmas, A.F.
Journal of Peptide Science 18 (3) 147-154
publié le , mis à jour le
C-terminally modified peptides aldehyde (glycinal and alpha-oxo aldehyde peptides) and ketone (pyruvic acid-containing
peptide) were synthesised to get new insights into the mechanism of acido-catalysed oxime ligation. Their tetrahedral
hydrated forms were investigated in solution and in the gas phase, using NMR and in-source collision-induced dissociation mass
spectrometry, respectively, and the kinetics of the oximation reactions followed using analytical HPLC. The results obtained confirmed
that the first step of the oximation reaction was the limiting step for the pyruvic acid-containing peptides because of the
steric effect and of the carbon angular strain of the ketone. The second step is the determining step for the aldehyde peptides
because the basicity of the oxygen of the hydroxyl function of the tetrahedral form is greater for glycinal than for alpha-oxo
aldehyde. These data strongly suggest that the hydrated form of the aldehyde partner has to be considered when oxime
reactions are performed in aqueous buffer.