Preparation of Monosaccharides

Some glycosidic linkages have proved stable to hydrogen fluoride solvolysis. Attempts to isolate monosaccharides by solvolysis of the O-specific polysaccharide (13) of Shigella sonnet phase 1 with hydrogen fluoride and of the capsular polysaccharide (14) of Streptococcus pneumoniae type 1 failed. Prior acetylation of the free amino groups of the diamino sugar did not render the polymer susceptible to the solvolysis. 

The glycosidic linkages of derivatives of 5,7-diamino-3,5,7,9-tetradeoxy-L-g/ycero-L-manno-nonulosonic (pseudaminic) acid proved stable towards hydrogen fluoride at room temperature. It has been possible to isolate free 

Solvolysis with hydrogen fluoride was successfully employed to obtain partially methylated sugars in the methylation analysis of carbohydrates. 

Isolation of the alditol (23) on solvolysis with hydrogen fluoride of the methylated oligosaccharide fragment of P. aeruginosa L yi 0 10a O-spe- 

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Preparation of Monosaccharides and Oligosaccharides from Bacterial Polysaccharides... 

The preferred source materials for preparation of monosaccharides are the homopolysaccharides built of repeated residues of a single sugar. A more-complex natural product may be used if the desired monosaccharide can be selectively liberated by hydrolysis, or if other sugars present in the hydrolyzate can be conveniently eliminated, for example, by fermentation. Alternatively, a more-complex... 

A comprehensive review (260 refs.) on the synthesis of carbohydrates from noncarbohydrate sources covers the use of benzene-derived diols and products of Sharpless asymmetric oxidation as starting materials, Dodoni s thiazole and Vogel s naked sugar approaches, as well as the application of enzyme-catalysed aldol condensations. The preparation of monosaccharides by enzyme-catalysed aldol condensations is also discussed in a review on recent advances in the chemoenzymic synthesis of carbohydrates and carbohydrate mimetics, in parts of reviews on the formation of carbon-carbon bonds by enzymic asymmetric synthesis and on carbohydrate-mediated biochemical recognition processes as potential targets for drug development, as well as in connection with the introduction of three Aldol Reaction Kits that provide dihydroxyacetone phosphate-dependent aldolases (27 refs.). A further review deals with the synthesis of carbohydrates by application of the nitrile oxide 1,3-dipolar cycloaddition (13 refs.). ... 

Bognar et al have employed this general synthesis for the preparation of monosaccharides incorporating benzothiazole. Thus, the condensation of o-aminothiophenol with acetylated aldonic acid chlorides (16) or nitriles (17) readily affords the benzothiazole derivatives (18), which may be deacetylated to the parent monosaccharides by treatment with alkali. 

A wide range of glucal and alkyl 2,3-dideoxy-D-co t/rr< -hex-2-enopyranoside derivatives have been reported in a study of the preparation of monosaccharide compounds containing two double bonds. 6-Sulphonyl esters of D-glucal could be converted into analogues with 6-deoxyalk-5-ene functionality by way of 6-deoxy-6-iodo intermediates, but corresponding methods did not lead to 2,3 5,6-di-unsaturated products. ... 

Such symps are used in the preparation of confections, preserves, and other foodstuffs. The maltose in malt symps is important in brewing (see Beer). Intravenous feeding (primarily in Europe and Japan) and sports beverage formulations take advantage of the fact that energy release from maltose becomes accessible to the body at a slower rate than energy suppHed by monosaccharides (31). 

A classical, and still most useful, physicochemical parameter for characterizing glycosaminoglycans is their specific optical rotation. For pure heparins from common sources, [a]80 = + 45 to + 53 ° (see Table II). The actual value depends on the relative proportions of monosaccharide constituents (that is, the L-idosyluronic acid residues make a less positive contribution than the n-glucosyluronic residues), and on the degree of sulfation of the preparation (that is, although sulfate groups may have little direct influence on the molecular rotation, they lower the value by acting as diluents ). 

A typical procedure calls for reaction of the hemiacetal donor with dicydohexyl carbodiimide and copper(I) chloride (0.1 equiv) at 80 °C, followed by an addition of the acceptor and continued heating. As an early demonstration of this protocol, oc-riboside 86 was prepared in moderate yield but with exclusive stereoselectivity [141]. Further measures were required for the glycosylation of monosaccharide acceptors, such as addition of p-toluenesulfonic add (0.1 equiv) to promote the formation of disaccharide 87 [144]. The method was more suitably applied to the synthesis of O-acyl glycopeptides, as evidenced by the formation of 88 in 60% yield [143,144]. Various peptides with non-nudeophilic side chains were found to be amenable to this stereoselective reaction. The [3-selectivity was suggested to arise from a preponderance of the a-isourea intermediate 85 in the activation step. 

Reaction of nitromethane and monosaccharide-derived dialdehydes is a useful tool that has been broadly used for the preparation of nitro and amino sugars, and carbocycles.30 Dialdehydes can easily be obtained by oxidative cleavage of conveniently protected monosaccharides with sodium periodate. Their subsequent Henry reaction with a nitroalkene, commonly nitromethane, usually gives isomeric mixtures that require the isolation of the major isomer.31 Thus, treatment of the D-ribose derivative 27 with sodium periodate gave dialdehyde 28, which was subjected to a Henry reaction with nitromethane, to afford nitrosugar 29 as an epimeric mixture (Scheme 11).32... 

In 1966 Landor and co-workers reported the preparation of chiral derivatives of LAH by its reaction with monosaccharide derivatives (46,61). These studies have been reviewed by Inch (62). Landor and co-workers planned to construct... 

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