Kinetics of the Pyridoxal-Catalyzed Dealdolation and β Elimination of Some Aromatic β-Hydroxy α-Amino Acids

Article abstract of DOI:10.1021/ja00376a032

The rates of dealdolation and β elimination of a number of para-substituted phenylserines have been determined by proton NMR.Electron-withdrawing substituents on the amino acid side chain enhance the dealdolation rate.In the substituted phenylserine β elimination and dealdolation were found to occur as parallel reactions.The metal ion-pyridoxal catalyzed systems undergo reaction more rapidly than the metal-free pyridoxal-catalyzed systems.A reaction mechanism for the parallel dealdolation and β-elimination reactions is proposed.In the case of one of the amino acids, phenylthreonine, the rate constants for the metal-free Schiff base were resolved into the specific rate constants for the individual solution components, and the variations obtained for the specific rate constants are interpreted in terms of the proposed reaction mechanism.