Galactose chloride

Write structural formulas for the a and 3 methyl pyranosides formed by reaction of o galactose with methanol in the presence of hydrogen chloride... 

Although the pronounced reactivity at the C-4 position is evident, examples of the formation of polychlorinated sugars are available. Thus treatment of D-galactose (85) with sulfuryl chloride in pyridine followed... 

Alternatively, penta-O-acetyl-galactose can be converted to the known 2,3,4,6-tetra-O-acetylgalactopyranosyl azide59 which after treatment with sodium methoxide in methanol and subsequent pivaloylation with pivaloyl chloride in pyridine, also furnishes the O-pivaloylated galactosyl azide60. 

A mixture of 10 g. of D-galactose, 10 ml. of ethyl acetoaeetate, 10 ml. of ethanol, and 5 g. of zinc chloride is heated on a steam bath during 75 minutes. The mixture is cooled, 45 ml. of water is added, and the solution is extracted with two 30-ml. portions of benzene. The aqueous layer is then extracted with nine 15-ml. portions of ethyl acetate. The united extracts are washed successively with an aqueous solution of sodium bisulfite and with an aqueous solution of sodium bicarbonate, dried with anhydrous sodium sulfate, filtered, and the filtrate evaporated to dryness, affording 4.5 g. of a sirup. This is saponified with 12.5 ml. of 10% sodium hydroxide solution, and then acidified (to Congo Red) with phosphoric acid. The aqueous solution is extracted with successive 30-ml. portions of ethyl acetate, and these are dried with anhydrous sodium sulfate, and individually evaporated to dryness. Extracts after the fourth yield a solid product m. p., 130°. Recrystallized from petroleum ether plus acetic acid, the compound has m. p. 132-134° yield, variable, ca. 2%.54... 

In a laboratory study by Schlekat et al. [15], it was demonstrated that coating silica particles with an exopolymer prepared from an estuarine bacterium enhanced the sorption of cadmium on to the particles. The composition of the exopolymer was glucose, galactose and glucuronic acid in the ratio 5 2 1. These investigations also compared the effects of salinity, pH and different concentrations of cadmium. Increasing salinity resulted in less cadmium associated with the particles, presumably due to competition with the chloride ion. The pH had a dramatic effect, resulting in only ca. 10% absorbed at pH 5 to more than 95% at pH 9. 

As indicated later (see Section VI,8), on addition of the chloride of praseodymium, europium, or other lanthanides to mono- or poly-sac-charide phosphates in D20, the signals of carbon atoms substituted with phosphate groups are recognizable, as they are displaced, relative to the rest of the 13C-n.m.r. spectrum.155 However, this diagnostic method is not applicable to sulfated polysaccharides, as signal displacements were not observed on addition of praseodymium or europium chloride to a solution of a,/3-D-galactose 6-sulfate or its sodium salt.156... 

The first benzoylated nitrile of an aldonic acid was prepared by Brigl, Muhlschlegel and Schinle by benzoylation of the n-manno-n- oZa-heptononitrile the hexabenzoyl derivative was obtained. A series of benzoylated nitriles has recently been prepared by Restelli de Labriola and Deulofeu by treatment of the oximes of L-rhamnose, D-glucose, D-galactose and D-mannose with benzoyl chloride and pyridine. They were the sole products and were obtained in high yields. 

Alkyl (or acyl) derivatives of the 6-amino-6-deoxy carbohydrates are examples of derivatives in which the hydrophilic and hydrophobic moieties are linked at other positions than C-1. Thus 6-amino-6-deoxy-D-galactose derivatives 34 were prepared from l,2 3,4-di-0-isopropylidene-6-0-tosyl-a-D-galacto-pyranose by the following reactions (1) substitution of the leaving group at C-6 by a phthaloyl function, (2) hydrazinolysis to afford a 6-amino-6-deoxy intermediate, (3) reaction of acyl or sulfonyl chlorides at the amino function, (4) deprotection of the acetal rings to afford the expected glycolipid 34 [56]. 

Neighboring-group participation by the vicinal, trans-acetoxyl group (see p. 125) serves to explain the abnormal behavior of methyl 4-0-acetyl-2,3-anhydro-6-0-benzyl- or -trityl-a-D-gulopyranoside with hydrogen chloride in acetone, or with 80% aqueous acetic acid, which give D-galactose, instead of the D-idose, derivatives.67 In the same way, 2-0-acetyl-3,4-anhydro-D-altropyranosides yield D-man-nosides, not D-idosides.9 6z(see p. 125). 

D-Galactose was converted by ethanethiol and hydrochloric acid into crystalline D-galactose diethyl dithioacetal, which was acetonated with acetone-zinc chloride. The product (15) was reduced to the L-fu-citol derivative (16) with Raney nickel. The overall yield of 16 was 29%, and it was characterized as the crystalline 6-p-toluenesulfonate 17. Oxidation of 16 by the Pfitzner-Moffatt reagent55 proceeded readily and, after O-deacetonation, and purification of the product by chromatography on a column of silica gel, L-fucose (18 13% overall yield from D-galactose) and L-fucitol (19 1% yield) were isolated (see Scheme 3). 

---