Milieu dependence of isomeric composition of 1-deoxy-d-erythro-hexo-2,3-diulose in aqueous solution determined by high-resolution NMR spectroscopy Original Research Article

In this study, high-resolution 1H (600.03 MHz) and 13C NMR spectroscopy (150.89 MHz) were used to elucidate the structures of the identifiable isomers of a complex mixture of equilibrating 1-deoxy-d-erythro-hexo-2,3-diulose (1-DG) (1) isomers in aqueous solution. Approximately 15 isomers were formed from the investigated deoxy-ketohexose, and the equilibrium of the isomers is dependent on the pH values and temperature. In contrast to non-hydrated isomers, hydrated 1-DG (1) isomers were exclusively formed in aqueous solution. Their relative concentration increased when the pH was increased to more basic conditions. An increase in solution temperature led to the elimination of water and an increase in the relative concentration of the non-hydrated 1-DG (1) isomers. The observed influence of different conditions on the isomeric composition was explained for all isomers. Also, these observations provided information for structure elucidation. Furthermore, the reaction behaviour of 1-DG (1) under basic conditions at high temperatures (up to 347.5 K) was interpreted and described.