Mutarotation of 2-amino-2-deoxy-D-glucose

Abstract

The rate of mutarotation of 2-amino-2-deoxy-D-glucose hydrochloride at temperatures between 15 and 35 °C was found to be very similar to that of D-glucose. The reaction was found to be first order and there was no marked catalysis by the amino-sugar cation. In strongly acid solution acid catalysis was observed but the hydronium ion was considerably less effective in catalysing the mutarotation of the amino-sugar cation than it is in in its effect on the mutarotation of glucose. This difference is explained in terms of Coulombic interaction. On the other hand catalysis by acetate was found to be quantitatively closely similar with 2-amino-2-deoxyglucose and glucose. The rate of mutarotation between pH 5·5 and 8·3 was found to be greatly affected by the concentration of amino-sugar. Over this pH range several species of the amino-sugar exist in the aqueous solution and this fact and the presence of several catalytic species renders a quantitative interpretation of the results difficult. However, it appears that the rate of mutarotation over this neutral pH range is mainly affected by the concentration by the free amino-sugar base.