Psicose, Sorbose and Tagatose

Deacetylation of tetraacetyl-L-sorbose phenylosazone121 (LII) may involve a Walden inversion on carbon 4 with the formation of an L-hexose phenylosazone dianhydride (LIII). The antipode had been prepared previously from tetraacetyl-D-gulose phenylosazone (synonym, tetra-acetyl-D-sorbose phenylosazone). 

A N-glycoside of L-sorbose, p-phenetidine L-sorboside, was synthesized in low yield by Kuhn and Birkofer.122 L-Sorbose was condensed in 

Methyl L-sorboside was discovered by Fischer,128 while its antipode was prepared for the first time by Lobry de Bruyn and Van Ekenstein.21 From a comparison of the [ ]d values of the glycosides with that of the ketoses, Hudson and Brauns124 designated both isomers as the alpha anomers. 

Since the methyl L-sorboside ([ ]d — 88°) is more levorotatory than the parent sugar L-sorbose ([ ]d — 43°), it was considered to be the alpha anomer of this L-ketose. In the same manner methyl D-sorboside ]D + 88°) was designated as the alpha form since it was more dextrorotatory than its parent sugar of the D-series, namely D-sorbose ([a]D + 43°). (See also page 113.) 

When methyl a-L-sorboside was methylated and the resulting penta-methyl derivative was hydrolyzed, a tetramethyl-L-sorbose was obtained. Oxidation of the latter with nitric acid gave dextrorotatory dimethoxy-succinic acid126 (LVII), from which fact it became evident that a normal pyranoside structure is present in the methyl a-L-sorboside, since this dimethoxysuccinic acid could only have arisen if carbons 4 and 5 were methylated. From a comparison of the rate of hydrolysis of ethyl a-L-sorboside126 with the methyl a-derivative the authors assumed that it 

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III. Reactions of Psicose, Sorbose and Tagatose 1. Qualitative and Quantitative Testa... 

The separation on several columns of the isomeric forms of several aldohexoses and the four ketohexoses (fructose, psicose, sorbose and tagatose) as their pertrimethylsilyl ether derivatives has been reported, and a mathematic approach used in an attempt to relate retention times to structures. 

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