Keto-enol glycylgycine peptide bond tautomerismstudy at complexation with metal ions

Keto-enolglycylglycine peptide bond tautomerism depending on the pH of the reaction medium was studied. It has been shown that there is no conversionof theamide group into an iminol (enol) groupin an acidic environment. In an alkaline medium (pH 8.5) (at an equimolar ratio of the substrate and base) glycylglycineis converted from keto- form into monosodium enol derivative. At follow-up action on the reaction mixture with metal salts (pH 5)the enol form is converted into a ketone one to form metalsglicylglicinate in the keto- form. In a highly alkaline environment (pH 11-12) (substrateratio : alkali of 1: 2 mol) glycylglycineis converted from keto-form into the enol form of disodium derivative, followed by action on which with copper sulfate (II) double coppercomplex in the enol form isobtained.