Carbohydrate Chemistry Volume 13

A Review of the Literature Published during 1979

By J. F. Kennedy, N. R. Williams

The Royal Society of Chemistry

Copyright © 1982 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-0-85186-112-8

Contents

Part I Mono-, Di-, and Tri-saccharides and their Derivatives,
1 Introduction, 3,
2 Free Sugars, 4,
3 Glycosides, 17,
4 Ethers and Anhydro-sugars, 44,
5 Acetals and Ketals, 53,
6 Esters, 57,
7 Halogeno-sugars, 73,
8 Amino-sugars, 78,
9 Miscellaneous Nitrogen Derivatives, 89,
10 Thio- and Phosphoro-sugars, 101,
11 Deoxy-sugars, 107,
12 Unsaturated Derivatives, 113,
13 Branched-chain Sugars, 123,
14 Dicarbonyl Compounds and their Derivatives, 131,
15 Sugar Acids and Lactones, 136,
16 Inorganic Derivatives, 145,
17 Alditols and Cyclitols, 150,
18 Antibiotics, 157,
19 Nucleosides, 173,
20 N.m.r. Spectroscopy and Conformational Features, 199,
21 Other Physical Methods, 214,
22 Separatory and Analytical, 223,
23 Stereospecific Syntheses from Carbohydrates, 227,
Part II Macromolecules,
1 Introduction, 233,
2 General Methods, 237,
3 Plant and Algal Polysaccharides, 247,
4 Microbial Polysaccharides, 274,
5 Glycoproteins, Glycopeptides, and Animal Polysaccharides, 313,
6 Enzymes, 417,
7 Glycolipids and Gangliosides, 544,
8 Chemical Synthesis and Modification of Oligosaccharides Polysaccharides, Glycoproteins, Enzymes, and Glycolipids, 572,
Author Index, 705,

CHAPTER 1

Introduction

Interest in the chemistry of mono- and di-saccharides continues unabated, with nearly 1300 references being mentioned in Part I of this report. Glycosides alone account for nearly 200 references, in part reflecting both the expanding range of glycosidic natural products being discovered, and the increasing study of di- and tri-saccharides following the advent in recent years of several efficient methods for the synthesis of α-glycosides. Likewise the range of complex carbohydrate-containing antibiotics shows no signs of reaching a limit, posing fresh challenges to synthesis which chemists have eagerly accepted; two elegant syntheses of spectinomycin are reported in Chapter 18. There is also great interest being shown in glucose as a convenient asymmetric source material for the synthesis of a wide range of chiral natural products, which is reflected in Chapter 23.

A text on aspects of asymmetry in carbohydrates has appeared, which includes reviews on the composition of reducing sugars in solution, asymmetric reactions of carbohydrates containing carbonyl groups, and prochirality and pseudoasymmetry in carbohydrate biochemistry, besides articles on nitro-sugar stereochemistry, chiral sulphur derivatives, and carbohydrate crown-ether compounds. A general survey of organic chemistry includes an extensive account of monosaccharide chemistry.

The latest issue in the series ‘Advances in Carbohydrate Chemistry and Biochemistry’ contains appreciations of the late Professors J. A. Mills and J. V. Karabinos, and includes a review on the chemistry of glycosiduronic acids.

CHAPTER 2

Free Sugars

The composition of reducing sugars in aqueous solution has been surveyed. A review on the structural properties of the anomeric centre in pyranoses and pyranosides has appeared. Three reviews concerning properties of fructose have been published, dealing with its metabolism, its chemical structure and properties, and its chemistry with some emphasis on the relationship between molecular structure and calculated and experimental values of optical activity, and such properties as taste. The production of nutritive sweeteners by acidic and enzymic hydrolysis of starch has been reviewed.

1 Isolation and Synthesis

Analyses by t.l.c. and g.l.c. of honeys from Robinia spp. and honeydew have shown that the former contains evlose and the latter melezitose as well as the usual mono- and di-saccharides. 3-Deoxytetrulose, useful for synthesis of 2-hydroxybutanoic acid, has been isolated in 4% yield from sodium bicarbonate treatment of xylan. Incubation of Aspergillus fumigatus with inulin produces di-D-fructofuranose 1,2′: 2,1′-dianhydride. An improved method for the preparation of crystalline β-lactose from heating a supersaturated solution of α-lactose hydrate has been reported. Differential scanning calorimetry was used to determine its true melting point. Improved yields of β-lactose have also been claimed from treatment of α-lactose hydrate with 0.02% sodium hydroxide in alcohols for 2 h. Methanol gave the best yields provided water content was below 10%.11 A blue-green alga, Agmenellum quadruplicatum, has been used to prepare 13C-labelled D-glucose, 2-O-α-D-glucosyl glycerol, 2-O-α-D-glucosyl glyceric acid, and sucrose by photobiosynthesis from 20 mole % 13CO2 as carbon foodstock.

A further paper on the cold-plasma decomposition of methane-water mixtures in the presence of apatite has appeared (see vol. 12, p. 6). Glucose 6-phosphate and ribose 5-phosphate were found among the products.

Reports on further studies of the formose reaction continue to appear. An investigation of solid catalysts has shown that selectivity can be achieved using a tobermorite or calcium oxalate; the major products were branched-chain sugar alcohols, 2-hydroxymethylglycerol, and 2,4-bis(hydroxymethyl)- and 3-hydroxy-methyl-pentitol. The same group has studied the effect of different solvent systems on the reaction. The calcium oxide-catalysed reaction was found to require a hydroxylic solvent and the induction period was shown to be related to the concentration of dissolved Ca2+ ion. The reaction in 90% and 100% methanol was analysed in detail; the formation of formaldehyde hemiacetal was shown to be essential, and competition between the Cannizzaro reactions and sugar formation was the important factor affecting sugar yield. High temperatures have been shown to produce hexoses from formaldehyde-calcium hydroxide. At 98°C the induction period was 15 s and the reaction gave 84% hexoses at 18% formaldehyde conversion, of which 90% was glucose. No branched-chain sugars were detected. Conversion was complete within 3 min. Higher conversions or lower temperatures gave more complex mixtures. The calcium hydroxide-catalysed reaction has been studied to determine the effects of pH and catalyst-formaldehyde ratio; a greater proportion of carbohydrate is produced when the latter is higher. With lower catalyst concentrations Cannizzaro products become dominant. Three 2-deoxy-sugars were formed in a one-step crossed formose reaction of acetaldehyde and formaldehyde.

High performance liquid chromatography has been used to study the mechanism and kinetics of the formose reaction. The mechanism proposed is shown in Scheme 1. Previous emphasis on mixed aldol condensations between C2 and C3 fragments is not supported, these providing only minor pathways.

The Fischer-Kiliani synthesis has been used to prepare 13C-enriched carbohydrates. The nitriles formed using Na 13CN were reduced over Pd-BaSO4 at pH 4.2 and 25 °C to give pentoses and hexoses in 60-90% yield. 1-Amino-1-deoxyalditols were produced in ~10% yield and their formation was favoured when hemiacetal formation was hindered in the parent aldoses. Preparation of glycolaldehyde, glyceraldehyde, erythrose, and threose with 13C-enrichment at various specific positions for use in determining proportions of cyclic hemiacetal and linear gem-diol by means of n.m.r., has been reported. The same group has described systems for multilabelling of aldoses using K 13CN and K 14CN by sequential addition and reduction of the nitrile with deuterium gas. Compounds prepared include DL-[1-14C, 2H]glyceraldehyde, D-[1-13C, 2H]erythrose, D-[1-13C, 2H]threose, D-[2-13C,2 H]ribose, D-[2-13C, 2H]arabinose, methyl alpha- and β-D-[2-13C, 2H]ribofuranoside, DL-[3-2H]erythrose, DL-[3- 2H]threose, DL-[1-13c, 2H]glyceraldehyde 3-phosphate, and D-[1-13C, 2H]ribose 5-phosphate. The cyanohydrin synthesis has been used in the preparation of 2,4,5,6,8-penta-O-acetyl-3,7-anhydro-D-threo-L-talo- (1) and -L-galacto-octose (2), utilizing the reduction procedure due to Moffatt et al. (see vol. 7, p. 27).

Aldol condensations analogous to the formose reaction have been utilized to synthesise mixtures of trioses, tetroses, pentoses, and hexoses from 3-oxo compounds. The same paper describes the synthesis of hexoses from barium hydroxide treatment of acrolein dibromide.

L-Gulose, required for synthetic work associated with bleomycin, has been prepared by a new route from D-glucose (Scheme 2). A new synthesis of D-arabinose from D-glucose involves periodate oxidation of the glucose derivative (3) (Scheme 3). The reaction is thought to be general for all aldoses that form 1,2-O-isopropylidene derivatives.

The formation of higher-sugar dialdose derivatives by dimerization of terminal acetylenic sugars and polymerization of enosuloses is covered in Chapter 12.

2 Physical Measurements

In an attempt to correlate gross structure of solute-water with packing and stereochemistry, the partial molal volumes and isentropic partial molal compressibilities were measured for sugars, uronic acids, and some di- and trisaccharides in water at 25 °C. Attempts to systematize the results were unsuccessful. In a different approach, the structural transitions at saturation temperature using Arrhenius plots of results obtained by conductance measurements on electrolyte-sucrose-water solution were determined. These transitions were postulated to be due to the ability of the sucrose to form intermolecular hydrogen bonds with the solvent, so that at saturation temperature it was considered to have entered the total structure of the solution.

The bonding of glucose to a yeast α-glucosidase has been studied using a fluorescent probe complexed to the enzyme.

Isotope effects in the acid-catalysed mutarotation of D-glucose have been studied by polarography in the presence and absence of acetone with either water or deuterium oxide solvent. It was concluded that the difference in isotope effects for the acetone-water reaction from that in water alone was due to the rate-determining step in the former cleavage being of the C-H bond of the enol form of acetone, whereas in water alone the rate determining step involved cleavage of the O-H bond at C-1. Two papers on the effect of Cu2+ and Ca2+ ions on the rate of mutarotation of D-glucose have appeared. The first-order rate constant was shown to be independent of pH in the range 3 .0 to 6.2, but increasing the temperature changed the equilibrium concentrations. The calculated thermodynamic parameters indicated that Cu2+ complexed at C-1. Studies on the mutarotation of alpha- and β-D-glucose in gels of poly(2-hydroxyethylmethacrylate) using polarimetry have been reported. The effect of incorporation of 4-vinylpyridine as co-polymer was investigated. With the copolymer the rate approximated to that of the reaction in bulk water; in its absence the rate was essentially zero. The results were interpreted as arising from the difference in activity of water in the gels with or without 4-vinylpyridine. The ionization and mutarotation of D-glucose, D-mannose, and D-fructose in aqueous alkali has been examined using 13C n.m.r. By means of curves of 13C n.m.r. shifts with increasing pH (13C-n.m.r. ‘titration’) pKa values and differences in acid strengths of the alpha- and β-anomers were determined. The shifts were not explainable by simple ionization but probably originate in a rapid equilibrium between cyclic and acyclic rotamer ionized forms; base catalysis thus causes a weakening of the ring C-O bond in the generated sugar anion. As models for the analysis of oligosaccharides, the 1H n.m.r. spectra of many pentoses, hexoses, glucosamine, galactosamine, fucose, and several di- and tri-saccharides in D2O have been determined. (For an account of the application of the method to oligosaccharide analysis see Chapter 20.)

The proportions of open-chain forms in fructose and sorbose in aqueous solution have been determined at 80°C using 13C n.m.r. to detect the carbonyl group. The proportions were 3 and 2% respectively. Laser Raman spectroscopy has been shown to distinguish the five- and six-membered rings of D-fructose in aqueous solution. In agreement with other methods the furanose-pyranose ratio was found to be 41: 59. The temperature-dependence of the pyranose-furanose equilibria in aqueous solution has been studied by g.1.c. Equilibration at 0 °C gave the following proportions: β-pyranose, 84.8%; α-furanose, 4.1%; β-furanose, 11.1%; at 50 °C the proportions were 55.8, 12.3, and 31.9% respectively. Similar isomerizations were found to occur on melting.

The irradiation effects of 60Co γ-rays on crystalline mannose have been studied by e.s.r. to investigate how the nature and concentration of unpaired electron species trapped in the solid vary with dose and period of storage at room temperature. The results were compared with those of lyoluminescence studies. Sucrose and rhamnose crystals have been shown to trap electrons intermolecularly when X-irradiated at low temperature. The hyperfine couplings of the electron with the protons of hydroxy-groups forming the trap and the relative stabilities of the trapped electron were determined. A similar study was performed on dulcitol and L-arabinose at 4.2 K. Sugar radicals, formed by u.v. irradiation between 200 and 300 nm, have been shown to be stable at room temperature and were able to initiate polymerization of acrylamide in water. The e.s.r intensity was in the order sucrose > methyl α-D-glucopyranoside [much greater than] cellobiose > D-xylose > D-glucose ≈ D-fructose and this was reflected in their relative abilities to initiate the acrylamide polymerization.

The rate of protonation of the hydroxy-groups of D-glucose in DMSO have been measured by following the chemical shifts of the protons of all hydroxy-groups and the coupling JOH,CH for α- and β-D-glucose. The results showed kO-6 ≈ kO-2 > kO-3 > kO-4 > kO-1. A kinetic investigation of the formose reaction has shown that the reaction is first order in formaldehyde (k1 [??] 10-7 – 10-6 s-1).

The difference in solubility of alpha- and β-D-glucose in water has been ascribed to the fact that the α-anomer can form a hydrogen bond with water at the ring oxygen giving in termolecular linkages, thus aiding nucleation. This bonding is diminished by the presence of the equatorial hydroxy-group of the β-anomer. G.c. and n.m.r. have been used to study the retention of alcohols by anhydrous α-lactose and the results compared with those obtained in the vapour phase or by freeze-drying. The retention decreased in the order MeOH > EtOH > PrOH ≈ BuOH.

3 Isomerizations

The kinetic parameters for aldose and ketose transformations in the D-glucose-D-mannose-D-fructose system at 27 °C on aluminate resin and hydroxide resin have been obtained. On both resins hydroxide ion catalyses isomerization. By complexation, resin-bound aluminate stabilizes D-fructose so that the equilibrium mixture contains 72% of the ketose. Lower temperatures were found to give the highest yields of D-fructose. A similar study on maltose gave a yield of 63% maltulose at 24 °C, but higher temperatures caused elimination of D-glucose at C-4. In a study of isomerization, enolization , etc. of monosaccharides in aqueous alkali, u.v. spectroscopy has been used to obtain reaction rate constants for the scheme:

sugar + OH- [??] sugar anion [??] enediol anion [right arrow] β-elimination products [right arrow] final products.

The reaction was carried out with the exclusion of oxygen to prevent oxidation of the enediol. The band at 310 nm was assigned to the enediol anion. A report of an investigation of the suitability of several bases as catalysts for preparing D-psicose from D-fructose has appeared. The yields were determined by l.c. and pyridine was found to be the most effective base studied. Mixtures formed by boiling a concentrated solution of o-fructose (1 kg 1-1) in pyridine under reflux contained 12.4% D-psicose, 25.8% D-fructose, and lesser quantities of D-glucose and D-mannose. The D-psicose was isolated by removal of solvent, and fermentation of other sugars by bakers’ yeast. The entire process was completed within three days to give gram quantities in 6.8% overall yield. Dipotassium hydrogen phosphate isomerizes pent-2-uloses to mixtures of pentoses and isomeric pent-2-uloses. The product equilibrium depends on initial concentrations and temperature. L-Rhamnose and L-fucose have been shown to isomerize under alkaline conditions. With pyridine or DCC, 6-deoxy-L-ribo-pentulose, 6-deoxy-L-arabino-pentulose, and L-quinovose were produced from L-rhamnose although almost half the starting material was recovered. With calcium hydroxide and triethylamine 6-deoxy-L-arabino-pentulose was the only product. Similar results were reported for L-fucose. The molybdate-catalysed epimerization of heptoses has been shown to yield, in addition to the expected C-2 epimers, C-3 epimers and some heptuloses. The reaction was applied to [D-glycero-D-galacto, -D-talo-, -D-gulo-, and -D-ido-heptose. Molybdate has been used to isomerize 2,6-anhydro-1-deoxy-1-nitro-D-galactitol (4) to the corresponding L-iditol (5) which could be converted to L-xylose by treatment with alkaline hydrogen peroxide.

(Continues…)Excerpted from Carbohydrate Chemistry Volume 13 by J. F. Kennedy, N. R. Williams. Copyright © 1982 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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