The composition of 2-keto aldoses in organic solvents as determined by NMR spectroscopy Original Research Article

The composition of the 2-keto aldoses d-glucosone (), 6-deoxy-d-glucosone (), d-allosone (), and d-galactosone () in organic solvents has been determined using NMR spectroscopy. Whereas these keto aldoses form mixtures with up to 15 different isomers in water, the number of forms is significantly decreased in organic solvents. Equilibrium mixtures of , , and in Me2SO, DMF, and pyridine consist to 70–90% of the prevailing α-1,5-pyranose form. Two bicyclic forms with a proportion of 80% are the main isomers of in pyridine. Generally, forms with non-hydrated keto functions prevail in non-aqueous solutions.