Aldose ethers from

An intramolecular ether (commonly called an intramolecular anhydride), formally arising by elimination of water from two hydroxy groups of a single molecule of a monosaccharide (aldose or ketose) or monosaccharide derivative, is named by attaching the (detachable) prefix anhydro- preceded by a pair of locants identifying the two hydroxy groups involved. 

The preparation of crystalline methyl ethers of iV-phenyl- or Af-p-tolyl-aldosylamine by condensation of aniline or p-toluidine with aldose methyl ethers proceeds, in many cases, readily and quantitatively in methanolic or ethanolic solution, either at room or reflux temperature. For this reason, such derivatives are frequently used to characterize aldose methyl ethers isolated during constitutional studies on polysaccharides. For D-glucose, for example, crystalline 2-0-methyl-, 6-0-methyl-,3,4-di-O-methyl-, 2,3,4-tri-O-methyl-, 2,4,6-tri-O-methyl-, " and 2,3,4,6-tetra-O-methyl-A-phenyl-n-glucosylamine have been prepared in this way. Although anomeric forms of A -arylaldosylamine methyl ethers are possible, such anomeric pairs have not been isolated. No similar derivatives have been obtained from ketose methyl ethers. 

A more common procedure for aldoses is their reduction with sodium borohydride to alditols and submission to GC-MS after conversion to TMS ethers [324], permethyl ethers, acetates or trifluoroacetates. This method was successfully employed in studies of the mechanism of conversion of deoxythymidine diphosphate D-glucose to deoxythymidine 4-oxo-6-deoxy-D-glucose by an oxidoreductase from E. coli [325]. An in-... 

At the temperatures commonly used in mass spectroscopy, this method is only valuable for the identification of such derivatives of D-fructose as the methyl ethers and acetates, but permits differentiation of ketoses from aldoses. ... 

In order to limit a set of Tables which, otherwise, would be extremely lengthy, only the commoner esters and ethers of the cyclic acetals of the aldoses and aldosides have been included. Esters of inorganic acids are omitted. Except for the tetroses, cyclic acetals of the aldehydo-aldos s are not included. The omission of cyclic acetals formed from trichloroace-taldehyde is made on the grounds that, of the large number of products, many are still but poorly defined. 

Solvated nearly colorless needles from alcohol or chloroform, dry at 105°. Turns yellow on exposure to light Dec 243. Sol in water, alcohol, acetone insol in ether. Oxidizes aldoses and ketoses, as well as other a-ketols, and is thereby reduced to a water-insoluble, deep red pigment, a triphenyl-formazan. LDjg i.v. in mice 5600 ug/kg, RTECS Vol. II, R, J. Lewis, R. L, Tatken, Eds. (1980) p 690. 

Tetroses and Pentoses - 4-0- -Butyldimethylsilyl-2,3-0-isopropylidene-L-threose (1) has been prepared in seven efficient steps from o-xylose. 3,4-0-Isopropylidene-D-eythrulose (4) has been synthesized from the known tetritol derivative 2 by primary protection as the silyl ether 3, followed by Dess-Martin oxidation and desilylation. Compound 2 was derived from D-isoascorbic acid (see Vol. 22, p. 178, refs. 9,10). In a similar reaction sequence, the enantiomer 5 has been obtained from L-ascorbic acid. The dehomologation of several di-0-isopropylidenehexofuranoses e.g., 6- 7) has been carried out in two steps without intermediate purification, by successive treatment with periodic acid in ethyl acetate, followed by sodium borohydride in ethanol. Selective reduction of 3-deoxy-D-g/jcero-pentos-2-ulose (8) to 3-deoxy-D-g/> cero-pent-2-ose (9) has been achieved enzymically with aldose reductase and NADPH." 4-Isopropyl-2-oxazolin-5-one (10) is a masked formaldehyde equivalent that is easily converted to an anion and demasked by mild acid hydrolysis. One of the three examples of its use in the synthesis of monosaccharides is shown in Scheme 1. ... 

Other reactions of carbohydrates include those of alcohols, carboxylic acids, and their derivatives. Alkylation of carbohydrate hydroxyl groups leads to ethers. Acylation of their hydroxyl groups produces esters. Alkylation and acylation reactions are sometimes used to protect carbohydrate hydroxyl groups from reaction while a transformation occurs elsewhere. Hydrolysis reactions are involved in converting ester and lactone derivatives of carbohydrates back to their polyhydroxy form. Enolization of aldehydes and ketones leads to epimerization and interconversion of aldoses and ketoses. Addition reactions of aldehydes and ketones are useful, too, such as the addition of ammonia derivatives in osazone formation, and of cyanide in the Kiliani-Fischer synthesis. Hydrolysis of nitriles from the Kiliani-Fischer synthesis leads to carboxylic acids. 

The products from perbenzylation (BnBr-KOH-DMSO) of six aldoses have been determined by - C-n.m.r. spectroscopy. After chromatographic removal of dibenzyl ether, the 8-pyranoside could be Isolated in yield from D-xylose, D-glucose, and D-mannose ... 

A series of aldoses has been reductively aminated (NaBH3CN) with octadecylamine to give hydrophobic conjugates as model compounds in the g.c.-m.s. analysis (as the N-acetylated O-trimethylsilyl ether derivatives) of reductivety aminated oligosaccharides from the Streptococcus pneumoniae capsular polysaccharide. Isosorbide dinitrate and its metabolites have been assayed in plasma by g.c. with electron-capture detection. ... 

The complexation of aldoses with cholesterol-derived boronic acids has been reviewed, and the changes in UV absorption and fluorescence intensity of a stilbene-type boronic acid on complexation with aldoses, especially D-fructose, have been studied with a view to their use in sugar-detection. Similar work has been carried out with diboronic acids derived from biphenyl and a -functionalized diaza-18-C-6 crown ether.A carbohydrate boronic acid derivative with liquid crystal properties referred to in Chapter 6, and further reports on boronate esters are noted in Chapter 17. 

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