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The efficient isomerization of l-rhamnose [the only cheaply available deoxy hexose] to 1-deoxy-l-psicose, 1-deoxy-d-psicose, 1-deoxy-l-fructose, 1-deoxy-d-fructose, 1-deoxy-l-tagatose, 6-deoxy-l-psicose, 6-deoxy-d-psicose, 6-deoxy-l-fructose, 6-deoxy-d-fructose, and 6-deoxy-l-tagatose is described. The conversion of rhamnose to ten of the sixteen 1- and 6-deoxyketohexoses is accomplished in water in three steps. The range of substrates for d-tagatose-3-epimerase (DTE) is extended to 1- and 6-deoxyketoses. An authentic sample of 6-deoxy-d-psicose is prepared from d-psicose. © 2009 Elsevier Ltd. All rights reserved.

Microbial oxidation of 2-C-methyl-d-ribitol and 2-C-methyl-d-arabinitol by Gluconobacter thailandicus NBRC 3254 produces 4-C-methyl-l-ribulose and 4-C-methyl-d-ribulose, respectively. Further, 4-C-methyl-l-ribulose and 4-C-methyl-d-ribulose were equilibrated by d-tagatose-3-epimerase (DTE) with 4-C-methyl-l-xylulose and 4-C-methyl-d-xylulose, respectively. These transformations demonstrate that polyol dehydrogenase and DTE act on branched synthetic sugars. The green preparation of all of the stereoisomers of 4-C-methyl pentuloses illustrates the ability of biotechnology to generate novel branched monosaccharides. © 2008 Elsevier Ltd. All rights reserved.