Glycine enolates: the effect of formation of iminium ions to simple ketones on alpha-amino carbon acidity and a comparison with pyridoxal iminium ions.

ABSTRACT: Equilibrium constants in D2O were determined by 1H NMR analyses for formation of imines/iminium ions from addition of glycine methyl ester to acetone and from addition of glycine to phenylglyoxylate. First-order rate constants, also determined by 1H NMR, are reported for deuterium exchange between solvent D2O and the alpha-amino carbon of glycine methyl ester and glycine in the presence of increasing concentrations of ketone and Brønsted bases. These rate and equilibrium data were used to calculate second-order rate constants for deprotonation by DO- and by Brønsted bases of the alpha-imino carbon of the ketone adducts. Formation of the iminium ion between acetone and glycine methyl ester and between phenylglyoxylate and glycine is estimated to cause 7 unit and 15 unit decreases, respectiv

SUBMITTER: Crugeiras J 

PROVIDER: S-EPMC2684581 | biostudies-literature | 2008 Feb

REPOSITORIES: biostudies-literature