Fucose acetal

L-Fucose was first prepared synthetically as its 1,2 3,4-di-0-isopro-pylidene acetal. Fucose acetals have been of interest in connection with... 

Erwinia gum (ZANFLO) Erwinia tahitica Sucrose, Maltose, Lactose, Glucose-syrup D-Glucose, D-Galactose, D-Guluronic acid L-Fucose, Acetate... 

Modifications of the basic structure (Fig. 8) show replacement of the sulfate group by acetate, fucose, methylfuco.se, sulfo-methylfucose, acetyl-methylfucose... 

A cyclic hexaacetyl oxime (XII) was also isolated by mild acetylation of D-galactose oxime and by treatment with sodium acetate and acetic anhydride. A cyclic aldoxime acetate (XIII) was also obtained by Voto6ek from D-fucose oxime, and by Restelli de Labriola and Deulofeu ... 

D-Fucose (Rhodeose). Voto6ek obtained tetraacetyl-D-fucononitrile in 25% yield by treating D-fucose oxime with sodium acetate-acetic anhydride. The nitrile, degraded with ammonia and silver oxide, yielded 5-desoxy-D-lyxose diacetamide in 40% yield. The diacetamide compound was hydrolyzed with 5% hydrochloric acid and the 5-desoxy-D-lyxose was obtained in solution and characterized as the p-bromo-phenylosazone. Hydrolysis of the diacetamide compound with 6 N sulfuric acid was realized by Voto6ek and Valentin and the 5-desoxy-D-lyxose was isolated as a sirup. 

With L-fucose oxime Restelli de Labriola and Deulofeu obtained the nitrile in 52% yield by the action of pyridine-acetic anhydride. 

A solution of L-fucose (4.92 g, 30 mmol) in anhydrous DMF (50 mL) was stirred with a desiccant (Drierite or Sikkon, 1 g) at 0°C (ice bath), and 2-methaxypropene (2.16 g, 30 mmol) was added followed by p-toluenesulfonic acid (-20 ing). After 1 h at 0°C, an additional stoichiometric amount of reagent (2.16 g) was added, and stirring was continued for 2 h at 0°C. Sodium carbonate (-5 g) was added, and the mixture was stirred further 1 h at room temperature. The solids were filtered off, and the filtrate was evaporated under diminished pressure at 40°C to a syrup that contained (TLC, ethyl acetate) one major product plus minor, fast-migrating components. Rapid chromatography of the product on a column of silica gel gave pure, crystalline 3,4-O-isopropylidene-L-fucopyranose 31 yield 3.7 g (-60%) mp 110-111°C, [ ]D -90 - -70° (24 h, equil. e 0.2, water). 

The procedure used for L-fucose was applied with L-rhamnose (4.22 g, 30 mmol) except that twice the stoichiometric amount of 2-methoxypropenc (4.32 g, 60 mmol) was added directly at the beginning of die reaction. The TIC of the crude amorphous residue (that remained after removal of the solvent) showed essentially only one spot (purity > 95% by NMR) corresponding to the attempting acetal (yield 5.2 g, 85%). Purification by rapid column chromatography (1 1 ethyl acetate/petroleum ether) gave pure, syrupy 2,3-0-isopropylidene-L-ffaamnopyianose 32 (4.9 g, 80%) that eventually crystallized by slow... 

Isbell and co-workers (51) have tried to minimize the oxygen reaction and to maximize the peroxide reaction. When a large excess of peroxide and a low temperature were maintained, they found that the monosaccharides are converted almost quantitatively to formic and two-carbon acids. Table II presents results for the peroxide oxidation of 14 sugars. The total acid produced from aldo-hexoses under favorable conditions is about six moles, consisting almost entirely of formic acid. Aldopentoses react more rapidly than aldo-hexoses and yield about five moles of formic acid per mole of pentose. Fructose and sorbose yield approximately five moles of total acid of which four moles are formic acid. Glycolic acid was identified qualitatively but not determined quantitatively. L-Rham-nose and L-fucose yield about five moles of acid, including four moles of formic acid. Acetic acid was identified only qualitatively. 

Schmidt and Wernicke74 have described a synthesis of digitalose starting with D-fucose dibenzyl mercaptal, which on condensation with acetone yielded the 4,5-isopropylidene derivative (LXXIV). Elimination of the dibenzyl mercaptal residues with mercuric chloride and cadmium carbonate in methanol gave 4,5-isopropylidene-D-fucose dimethylacetal (LXXV), from which the 2-benzyl ether was obtained on treatment with sodium and benzyl chloride. Methylation produced 2-benzyl-3-methyl-4,5-iso-propylidene-D-fucose dimethyl acetal (LXXVI), from which the iso-propylidene group was eliminated on treatment with methanolic hydrogen chloride, which also effected glycopyranoside formation (LXXVII). The... 

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