On the Formation of Amino Acids by Gamma-Ray-Induced Carboxylation of Amines in Aqueous Solutions

Abstract

n-propylamine, isoamylamine, and pyrrolidine were used as model substrates. The carboxylation process was studied as a function of the radiation dose, the pH value of the solution, and the concentration of amine and carbon dioxide. The yield of the amino acids formed was found to be strongly dependent on them. In all cases, by carboxylation of the individual amine a number of amino acids is formed. The main products formed by carboxylating 0.1 M1 ethylamine (pH 6.5) are: alanine (Gi = 0. 51), a-aminobutyric acid (Gi = 1.10), a-aminoisobutyric and y-aminobutyric acid (total Gi = 0.29), glycine (Gi = 0.12), proline (Gi = 0.08), and norvaline (at pH 8.1, Gi = 0.60). In the carboxylation of 0.1 M n-propylamine (pH 6.4) the following compounds are obtained: a-aminobutyric acid (Gi = 1.25), a-aminoisobutyric and y-aminobutyric acid (total Gi = 0.58), valine (Gi = 0.70), alanine (Gi = 0.17), and aspartic acid (Gi = 0.05), besides traces of other amino acids. The carboxylation of 0.1 M isoamylamine (pH 6.4) leads to the following amino acids: leucine (Gi = 0.76), norvaline (Gi = 0.50), valine (Gi = 0.30), a-aminobutyric acid (Gi = 0.10), and a-aminoisobutyric and y-aminobutyric acid (total Gi = 0.20). Proline (Gi = 0.40) was found as the main product by carboxylation of 0.01 M pyrrolidine at pH 5.6. Preliminary experiments on the amination of 0.1 M acetic acid and of 0.01 M and 0.1 M n-propionic acid were carried out. Mechanisms for the formation of amino acids are suggested.