D-Galactose dimethyl acetal

Percival and Thomson44 obtained a mixture of disaocharide esters from which, on hydrolysis and derivatization, they isolated 2,3,4,6-tetramethyl-D-galactose anilide and a mixture of methylated acids. From these acids they obtained 3,6-anhydro-2,5-dimethyl-L-galactonic acid, the structure of which was determined by almost the same means as those employed by Jones and Peat.23 On methanolysis of hexamethylagarobiose, Araki28 isolated 3,6-anhydro-2,5-dimethyl-L-galactose dimethyl acetal (XIII),... 

M. Kiso, A. Yasui, and A. Hasegawa, Syndiesis 2-azido-2-deoxy-3,4 S,6-di-0-isoptopy]-idene-aldehydn-D-mannose dimethyl acetal and 4-azido-4-deoxy-23 5,6-di-0-isopropyl-idene-oldeAyrio-D-galactose dimediyl acetal, Carbokydr. Res. 727 137 (1984). 

The method was used in studies of a fungal heterogalactan.150 The polysaccharide was subjected to successive tritylation, methylation, detritylation, p-toluenesulfonylation, reaction with sodium iodide, and, finally, reaction with sodium p-toluenesulfinate. The product was then treated with sodium methylsulfinyl carbanion in dimethyl sulfoxide, the product remethylated, and the polysaccharide material recovered by gel chromatography. The polymer was hydrolyzed, and the sugars in the hydrolyzate were analyzed, as the alditol acetates, by g.l.c.-m.s.1 The analysis revealed that —60% of the hexose residues that were unsubstituted at C-6 had been eliminated. As the product was still polymeric, it was concluded that these residues had constituted a part of side chains linked to a main chain of (1 — 6)-linked D-galactose residues. 

P. A. Levenc and G. M. Mayer, Pentamethyl-d-mannoae and peniametfayl-d-galactose and their dimethyl acetals, J. Biol Chan. 74695 (1927). 

Preparative application of the reaction to a partially protected sugar derivative is illustrated by the cleavage of D-galactose-4,5-monoacetonide dimethyl acetal (7) to D-threose-2,3-monoacetonide (8) and glyoxal dimethyl acetal (9). ... 

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