Galactonic 6-0-methyl

Methylene, Me ester. Methyl 4-C-acetyl-6-deoxy-2,3-0-methylene-D-galactonate. Methyl eurekanate C10H16O7 248.232... 

J. Yoshimura and M. Matsuzawa, Stereoselective synthesis of methyl 4-C-acetyl-6-deoxy-2,3-O-methylene-D-galactonate and -D-gluconate. Determination of the D-galacto configuration of methyl eurekanate by synthesis, Carbohydr. Res. S5 C1 (1980). 

Jones and Peat23 separated methylated agar into an acidic and a neutral fraction by precipitation methods. From the hydrolyzate of the acidic fraction they isolated 2,4,6-trimethyl-D-galacto e, 2,3,4,6-tetra-methyl-D-galactose, and 3,6-anhydro-2,5-dimethyl-L-galactonic acid (XII, as the crystalline amide of m. p. 173°). The structure assignment of XII was made on the following basis. The rotation of its amide, [a]D —75.7°... 

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),... 

Chloric acid, in conjunction with catalysts (particularly vanadium pentaoxide), is used for the oxidation of aldonic acids or lactones to the 2-glyculosonic acids. Thus, D-glucono-1,4-lactone (9) and potassium D-galactonate in methanol, in the presence of phosphoric acid and vanadium pentaoxide, are oxidized by chloric acid to methyl D-arabino-2-hexulosonate (10) and methyl D-/yxo-2-hexulosonate, respectively.38 At moderate temperatures in the absence of a catalyst, aldoses, ketoses, and sucrose are inert to the action of chlorates over a several weeks time period 39 bromates in alkaline solution also exert no oxidative action (Scheme 5). 

L-Galactonic acid, I, 69 and calcium salt, I, 70 —, 3,6-anhydro-2,4-dimethyI-, methyl ester, II, 77... 

Many functional derivatives incorporating a thiazole ring in their structure have been produced by this method. An illustrative example is the condensation of pentaacetyl-D-galactonic acid thioamide with chloroacetone to give 4-methyl-2-(D-galactopen-taacetoxypentyl)thiazole which is deacetylated in the usual way (Scheme 164) (69ACH(62)179). 

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