Tagatose solution

The composition of 6-0-methyl-D-ii/ to-2-hexulose (6-O-methyl-D-tagatose) in aqueous solution at 35° is 21% of a-furanose, 69% of/ -fura-nose, and 10% of the keto form.15 The ratio of a- to / -furanose for 6-0-methyl-D-psicose was found to be — 2.4 1 that of a- to / pyranose for 5-O-methyl-D-psicose, —1.25 1 the proportion of the keto form was not determined.13... 

The solubility and hygroscopicity of tagatose are similar to those of sucrose, but the viscosity of solutions is lower. As a reducing sugar it is less stable in acid conditions and liable to take part in Maillard reactions. 

For L-sorbose and D-tagatose, the spectrum of the lyophilizate of the equilibrated solution is essentially identical with that of the one crystalline modification, of each, known. These results agree with the interpretation that the sugar in the equilibrium solution exists almost entirely in the form known in the crystalline state (see p. 30). 

When D-tagatose is added to a basic aqueous solution, an equilibrium mixture of three monosaccharides is obtained. What are these monosaccharides ... 

In this context, it appears to be of relevance to briefly mention some comparable reaction systems for ketose epimerization. Petrus and his group, as well as Petrus, Serianni and co-workers, recently reported the stereospecific molybdic acid catalyzed isomerization of 2-hexuloses to branched-chain aldoses [55-57]. Upon treatment with a catalytic amount of molybdic acid in aqueous solution, the 2-ketohexoses, o-fructose, L-sorbose and o-tagatose, underwent a stereospecific intramolecular rearrangement to give the corresponding 2-C-hydroxyme-thylaldoses, 2-C-hydroxymethyl-D-ribose (o-hamamelose), 2-C-hydroxymethyl-L-lyxose and 2-C-hydroxymethyl-o-xylose, respectively (see Petrus, Petrusova and Hricovfniova, this vol.). 

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