A concise approach to the synthesis of all twelve 5-deoxyhexoses: d-tagatose-3-epimerase—a reagent that is both specific and general

2-Deoxy-d-glucitol and 2-deoxy-d-allitol, both prepared as crystalline polyols from d-erythronolactone, are oxidized by Gluconobacter thailandicus NBRC 3254 to 5-deoxy-d-threo-hexulose [5-deoxy-d-fructose = 5-deoxy-l-sorbose] and 5-deoxy-d-erythro-hexulose [5-deoxy-l-psicose = 5-deoxy-d-tagatose], respectively. d-Tagatose-3-epimerase (DTE) equilibrates 5-deoxy-d-fructose to 5-deoxy-d-psicose and 5-deoxy-l-psicose to 5-deoxy-l-fructose, providing substrates for the preparation of all eight d- and l-5-deoxy aldohexoses by aldose isomerases. This combination of chemical and biotechnological methods allows a concise approach to the synthesis of all twelve 5-deoxy hexoses and further demonstrates the range of deoxy sugar substrates on which DTE is active. NMR studies show that 5-deoxy-d-fructose exists solely as the β-pyranose form whereas both pyranoses of 5-deoxy-d-fructose [α:β. 22:78] are observed. [For the sake of clarity, all ketoses in this Letter are shown in blue, alditols in red and aldoses in purple.]