Galactopyranosid uronic acid, methyl

Model compounds related to the pectin molecule, namely, methyl (methyl a-D-galactopyranosid)uronate (110, R = H), and methyl 4-0-(methyl a-n-galactosyluronic acid)-(methyl a-D-galactopyranosid)uronate (110, R = methyl a-D-galactopyranosyluronic acid) have been subjected to treatment with sodium methoxide hi methanol and have undergone the expected elimination to give methyl (methyl 4-deoxy-(3-L-i/ireo-hex-4-enopyranosid)uronate (lll) from this compound, by hydrogenation... 

The reaction of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide with methyl (methyl 2-0-methyl-a-D-galactopyranosid)uronate in the presence of silver carbonate has yielded the crystalline pseudoaldobiouronic acid derivatives methyl [methyl 2-0-methyl-3-0- and 4-0-(2,3,4,6-tetra-0-acetyl-)3-D-gluco-pyranosyl)-a-D-galactopyranosid]uronate. Deacetylation of the compounds followed by Kuhn methylation afforded mainly crystalline, fully methylated products. 

Low yields of uronic acid usually result from the action of selective oxidants on glucosides and non-reducing acetals of the aldoses in which all the hydroxyl groups are free. However, a 56% yield of D-galacturonoside has been claimed for the oxidation of methyl a-D-galactopyranoside with nitrogen dioxide . 

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