Amino acids as CH-acids 17. Increase in the amino acid ?-proton mobility in Schiff base copper complexes with pyridine or N-2-pyridinecarbonyl-2?-aminobenzaldehyde ligands

Abstract

1. The reversible replacement of methanol by methylate ion in the equatorial plane of the copper complex of N-salicylidene-S-valine has been studied spectrophotometrically; study has also been made of the kinetics of the MeO− ion-catalyzed racemization of the S-valine fragment of this complex in methanol solution at 25°C. 2. Pyridine and N-salicylidene-S-valine form a mixed complex with copper ions, the kinetic CH-acidity of this complex being higher than that of copper N-salicylidene-S-valinate. 3. N-2-Pyridinecarbonyl-2-aminobenzaldehyde has been synthesized and its Schiff base with S-valine used as ligand in a copper complex. Under the action of MeO−, the S-valine fragment of this complex racemizes 90 times more rapidly than the S-valine fragment of copper N-salicylidene-S-valinate.