Carbohydrate Chemistry Volume 6

A Review of the Literature Published during 1972

By J. S. Brimacombe

The Chemical Society

Copyright © 1973 The Chemical Society
All rights reserved.
ISBN: 978-0-85186-052-7

Contents

Part I Mono-, Di-, and Tri-saccharides and their Derivatives,
1 Introduction, 3,
2 Free Sugars, 5,
3 Glycosides, 17,
4 Ethers and Anhydro-sugars, 30,
5 Acetals, 39,
6 Esters, 44,
7 Halogenated Sugars, 53,
8 Amino-sugars, 59,
9 Hydrazones, Osazones, and Related Compounds, 67,
10 Miscellaneous Nitrogen-containing Compounds, 72,
11 Thio-sugars, 83,
12 Derivatives with Nitrogen or Sulphur in the Sugar Ring, 86,
13 Deoxy-sugars, 88,
14 Unsaturated Derivatives, 91,
15 Branched-chain Sugars, 100,
16 Aldehydo-sugars, Alduloses, Dialduloses, and Diuloses, 112,
17 Sugar Acids and Lactones, 118,
18 Inorganic Derivatives, 123,
19 Cyclitols, 125,
20 Antibiotics, 130,
21 Nucleosides, 137,
22 Oxidation and Reduction, 156,
23 N.M.R. Spectroscopy and Conformational Features of Carbohydrates, 163,
24 Other Physical Methods, 172,
25 Polarimetry, 177,
26 Separatory and Analytical Methods, 178,
27 Alditols, 181,
Part II Macromolecules,
1 Introduction, 185,
2 General Methods, 187,
3 Plant and Algal Polysaccharides, 197,
4 Microbial Polysaccharides, 228,
5 Glycoproteins, Glycopeptides, and Animal Polysaccharides, 274,
6 Enzymes, 393,
7 Glycolipids and Gangliosides, 493,
8 Chemical Synthesis and Modification of Oligosaccharides, Polysaccharides, Glycoproteins, Enzymes, and Glycolipids, 516,
Author Index, 592,

CHAPTER 1

Part I

MONO-, DI-, AND TRI-SACCHARIDES AND THEIR DERIVA TIVES

By J .S. Brimacombe R. J . Ferrier R. D. Guthrie T. D. Inch

I Introduction

The general terms of reference remain those set out in the Introduction to Volume 1 (Vol. 1, p. 3) and the arrangement of subject matter follows that of previous Reports.

It is not easy to pick out any significant trends in a year that has seen much satisfactory progress and activity on a number of fronts. As has been pointed out to us, it is unwise to generalize about the state of a subject over a period as short as a year. There have been a number of notable achievements during the year in the area of synthetic carbohydrate chemistry, particularly among the antibiotic substances, where full details of the total syntheses of gougerotin, blasticidin S, and kasugamycin have been made available (Chapter 20). The nucleosides, covered in Chapter 21, generally remain an area of intense activity and there has also been a marked increase in the number of papers dealing with the synthesis of branched-chain sugars (Chapter 15). The functionalization of branched chains has interested a number of groups. Another interesting feature to emerge this year is the influence that metal ions can exert on the reactions of carbohydrates. The way in which Angyal and his colleagues have harnessed this information to useful synthetic ends is reported in Chapters 3 and 18. Exciting developments can be anticipated in this area.

Recent advances in the applications of n.m.r. spectroscopy to the study of carbohydrate chemistry are covered in Chapter 23, where a number of useful and extensive reviews in this area are mentioned. It is also interesting to note the increasing frequency with which reference is made in Part II to n.m.r. methods. The application of X-ray crystallography in carbohydrate chemistry shows a spasmodic, but nonetheless increasing, growth and the types of structure that can now be resolved by direct methods become increasingly more complex.

The International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Biochemistry (IUB) have jointly published tentative rules dealing with the nomenclature of carbohydrates (cf. Vol. 5, p. 3).

Several books of general interest have appeared and the life and scientific works of Michael Tswett – the founder of chromatography – have been reviewed to mark the centenary of his birth.

An obituary in Volume 27 (1972) of Advances in Carbohydrate Chemistry and Biochemistry has paid tribute to Professor W. W. Zorbach (1916–1970).

The April 4 and October 5 issues of Carbohydrate Research were dedicated to Professors M. Stacey and J. E. Courtois, respectively, in honour of their sixty-fifth birthdays.

2 Free Sugars

The effects of ionizing radiation on carbohydrates have been reviewed.

An automated method has been developed for the separation of neutral monosaccharides, which is based on ion-exchange chromatography of sugar borate complexes at pH 7. Mixtures of trehalose, cellobiose, L-rhamnose, D-ribose, D-mannose, L-arabinose, D-galactose, D-xylose, and D-glucose were resolved easily. The separation of sugars on polyamide layers was shown to depend on the number of and the distance between peptide groups in the macromolecule. It is possible to compare and determine the nature of the polyamide used from the sugar Rr values.

Isolation and Synthesis

L-Rhamnose has been identified as the sugar component in a new microbial metabolite of phosphoramidon. Fructose, sorbose, glucose, sucrose, inositol, and mannitol were among the products identified by g.l.c. of silylated derivatives of cocoa-bean extracts from many sources.

Most of the arabinose obtained by acid treatment of soil has the L-configuration, indicating that it probably originates in plants.

Methanolysis has been assessed as a procedure for releasing free sugars, acetamidohexoses, and uronic acids from sugar-containing natural products. Monosaccharides were found to be stable for 24 h in 2M-methanolic hydrogen chloride at 100 °C, but underwent decomposition under these conditions in 4M-methanolic hydrogen chloride. Glycopeptides and oligosaccharides released their carbohydrates within 3 h in 1M-methanolic hydrogen chloride at 85 °C. Various factors relating to analytical determination of the released sugars were discussed.

Total syntheses of DL-erythrose and DL-threose, dihydroxyacetone and DL-erythrulose, DL-glyceraldehyde, 14 and 2-deoxy-DL-, L-, and D-erythro-pentoses have been reported. The effects of monosaccharides and lead oxide as catalysts on carbohydrate-forming condensations of formaldehyde have been studied.

Cyclic carbonates such as (1) and (2), which were formed by telomerization of vinylene carbonate with polyhalogenomethanes, have been converted by treatment with acid into derivatives of DL-lyxose (3) and DL -xylose (4).

D-Talose has been obtained, in 90% yield, by hydroxylation of D-galactal with hydrogen peroxide in the presence of sodium molybdate. Deamination of 2-amino-2-deoxy-o-mannopyranose with sodium nitrite in aqueous acetic acid at 0 °C afforded D-glucose in 72% yield.

Acetolysis of methyl D-riboside derivatives afforded mixtures of D-ribose and D-arabinose acetates in a ratio of 4 : 1. Similar acetolysis of methyl D-lyxoside derivatives afforded mixtures of acetylated D-lyxose and D-xylose in a ratio of 5 : 2. Epimerization of D-glucose, D-xylose, and D -arabinose derivatives did not occur.

The enzymic synthesis of lactose labelled with 14C in the D-galactose residue and with 3H in the D-glucose residue has been described. ‘2-Deoxy -D-[1-14C]ribose’ has been synthesized by standard procedures.

A large-scale preparation of D-allose has been described. The key steps involving an oxidation-reduction sequence on 1,2:5,6-di-O-isopropylidene -α-D-glucofuranose were investigated in detail. The oxidant of choice was ruthenium dioxide-potassium periodate, while sodium borohydride, lithium aluminium hydride, and sodium bis-(2-methoxyethoxy)aluminium hydride all gave essentially pure D-allo-isomer in the reduction stage.

L-Psicose has been prepared by selective tosylation of methyl 1,3-O -benzylidene-α-L-sorbopyranoside (5) to give (6), which was then oxidized and reduced at C-4, desulphonylated with lithium aluminium hydride, and acid hydrolysed. A new synthesis of D-tagatose has been developed (see Chapter 13).

D- Glycero-L-galacto-and D-glycero-L-ido-heptoses have been synthesized from D-xylose as illustrated in Scheme 1. D-Glycero -D-allo-heptose has also been prepared.

Following an earlier report (Vol. 5, p. 156) on the preparation of 2-O -methyl-D-arabinose by degradation of 3-O-methyl-D-glucose with silver carbonate on Celite, it has now been shown that tetroses can be similarly prepared from readily available pentoses. L-Threose has been prepared, in 40% yield, as its isopropylidene derivative following oxidation of L-sorbose with silver carbonate on Celite.

L-(4S)[4-2H]Threose has been synthesized stereospecifically as illustrated in Scheme 2.

Acetolysis of 1,2:5,6-di-O-isopropylidene-α-D-allofuranose with acetic acid, acetic anhydride, and sulphuric acid occurred with partial inversion of configuration at C-2 and provided a means of obtaining D-altrose (D -altrose : D-allose ratio 1.4 : 1) following deacetylation of the products. The method was essentially confirmed as a small-scale procedure, since a chromatographic separation of the sugars was necessary. It had been shown previously that certain aldoses undergo epimerization under these conditions, but that D-allose only gives a trace of D-altrose. Presumably, the reaction is a further example of an epimerization in a vicinal, cyclic trihydroxy-system in which the steric relation is cis, trans.

Mutarotation and Epimerization

The mutarotation of sugars has been reviewed (in Polish).

Both the α- and β-furanose forms have been identified in aqueous solutions of L-arabinose. The equilibrium composition in water at 25 °C is α-pyranose 57%, β-pyranose 30.5%, α-furanose 8%, and β-furanose 4.5%. The rate constants for the approach to equilibrium appeared to be the same for all components in the tautomerization of β-L-arabinopyranose in water. Thus, the complex mutarotation of β-L-arabinopyranose remains unexplained.

Catalysis of the mutarotation of β-D-mannopyranose by Cu2+, Co2+, Fe2+, Zn2+, and Mn2+ ions has been studied. Evidence for metal complexes was adduced and it was suggested that the complexes mutarotate faster than the free sugar.

Ribose, arabinose, xylose, and lyxose were epimerized on heating in aqueous molybdic acid solution at 90 °C for 6 h to give an equilibrium mixture containing the aldoses, erythrose, threose, and anhydropentoses. Transitory molybdate complexes with the C-1 and C-3, or with the C-2 and C-4, hydroxy-groups underwent epimerization at C-2 and C-3, respectively. Arabinose and xylose with trans-related] C-2 and C-3 hydroxy -groups were formed preferentially. D-Glucose and D-mannose were epimerized by catalytic amounts of aqueous molybdic acid to a 3 : 1 mixture of the two sugars. A mechanism involving inversion of configuration of the carbanion formed by loss of a proton from a 1,3 -molybdate complex with the pyranose ring was proposed.

L-Glucose has been prepared by epimerization of either L-mannose or its phenylhydrazone in a reaction promoted by molybdate ion.

The specific reaction rate for inversion of sucrose in aqueous hydrochloric acid was determined with a reproducibility of 5% by a complexo-metric method designed to eliminate mutarotational lag.

A full report has appeared on a study of the mutarotation of 2,3,4,6 -tetra-O-methyl-D-glucose, catalysed by reversed micelles in non-polar solvents. Following n.m.r. spectroscopic studies, it was suggested that strong interaction occurs between the sugar and the hydrophilic groups of the micellar surfactants (e.g. dodecylammonium propionate). Catalytic factors of several hundreds were observed and the relevance of these findings to enzyme studies was discussed.

The proportions of anomeric furanoses and pyranoses present at equilibrium in deuterium oxide solutions of all the aldopentoses and aldohexoses have been determined. A valuable, detailed discussion of each of the aldohexoses marks a very significant point of sophistication in the development of sugar chemistry.

5-Hydroxypentan-2-one (7) and 6-hydroxyhexan-2-one (8) were shown to be acyclic in water, but there was only a slight preference for this form in organic solvents. Increases in temperature and solvent polarity favoured the acyclic forms of these compounds, which are models for 2-ketoses.

Replacement of the C-3 hydroxy-group of L-idose by a fluorine atom had no effect on the mutarotational equilibrium. The use of 19F n.m.r. spectroscopy in the study of this equilibrium is described in Chapter 23. 5-Thio-α-D-glucopyranose mutarotated more rapidly than α-D-gluco-pyranose 44 (see Chapter 12).

Physical Measurements

A very simple kinetic model for the homogeneous oxidation of D-glucose and D-fructose in aqueous alkaline solution has been developed. It involves the influence of the type and concentration of the hexose, the hydroxide ion concentration, the oxygen concentration in the liquid phase, and the temperature on the rate of formation of the acidic reaction products. In furthering this work, the kinetic model was extended to cover the distribution of products. The kinetics and mechanism of cupricion oxidation of D-glucose in alkaline solution have been studied.

The decomposition of D-glucose and D-xylose in dilute sulphuric acid solution at 160–200 °C has been studied kinetically.

The electronic charge distributions in mono-, di-, and poly-saccharides have been calculated following the LCAO–MO method of Del Re, and a theoretical study of the vibrational spectra of α-D-glucose has been made by normal-co-ordinate analysis. The positional vibrational frequencies were compared with those observed in the i.r. and Raman spectra of α-D-glucose both as a crystalline solid and in aqueous solution. The overall agreement between the observed and calculated spectra was considered to be satisfactory.

A study of the fluorescence of ‘sweet sensitive’ protein and its sugar complexes has shown that sucrose gives a different fluorescence pattern to that of D-glucose. It was suggested that mono- and di-saccharides interact with the protein at different sites.

Ethylenediamine forms hydrogen-bonded complexes with D-glucose, D-mannose, D-galactose, 2-amino-2-deoxy-D-glucose, and maltose (see Scheme 3). The formation of complexes was established from physicochemical studies such as paper chromatography, pH titration, and u.v. spectroscopy. The spectral properties confirmed a 1 : 1 complex in each case and, where possible, the hydroxy-group at C-1 is the presumed site of amine bonding.

Aldopentoses exhibited a very weak c.d. absorption band at 290 run in aqueous solution. The wavelength of this band is characteristic of the n [right arrow] π* transition of a carbonyl group, and the band was attributed to the presence of the aldehydo-form of the pentose in solution. The 290 nm band was not observed with aqueous solutions of D-glucose and sucrose.

A study has been made of the low-pressure ultrafiltration of solutions of sucrose and raffinose using anisotropic membranes.

X-Ray structures of hydrated complexes of lactose, D-galactose, and myo-inositol with calcium bromide have been determined.

E.s.r. spectroscopy has been used to investigate the γ-radiolysis of pentoses and hexoses; the results indicated that C — H bond cleavage occurs at positions –4 of the sugar molecule.

Reactions

The mechanism of the cyanohydrin reaction of D-arabinose has been investigated and the sequence of reactions depicted in Scheme 4 was proposed.

Standard procedures for the preparation of 1 : 1 adducts of D-glucose and maltose with the hydroxides of barium, calcium, and strontium have been established. It was suggested that the adducts may be useful in the isolation of oligosaccharides from industrial wastes. Similar 1 : 1 adducts were formed with cellobiose, lactose, maltitol, maltose, melibiose, sucrose, andαα-trehalose. One metal atom was associated with every two D-glucose (or related) residues in the adducts formed with amylose and amylopectin.

D-Fructose was converted into 2-(hydroxyacetyl)furan, in low yield, on treatment with mineral acids at elevated temperatures. D-Glucose also gave a low yield of the furan derivative, presumably by a similar reaction mechanism following its conversion into D-fructose by way of the 1,2- enediol. Experiments with D-[2-3H]glucose and in tritiated, acidified water have shown that intramolecular transfer of the proton from C-2 in D-glucose to C-1 in D-fructose occurred.

The mechanism of conversion of various carbohydrates (including D-xylose, D-glucuronic acid, and L-ascorbic acid) into 2-furaldehyde has been studied by measuring tritium incorporation from 3H2O. The 2-furaldehyde from D-xylose contained no tritium, whereas that from L-ascorbic acid contained 60% of the radiochemical activity of the solvent at the aldehyde group.

Treatment of D-glucose in dilute sulphuric acid at 100 °C for 2 h afforded less than 1% of D-fructose and D-arabinose; other sugars were studied under similar conditions.

On heating at 96 °C in aqueous solution at pH 3.5 or 4.5, D-glucuronic acid afforded compounds (9)–(20) and 3-acetyl-1-oxocyclohexane-2,3,6 -triol. Under these conditions, D-galacturonic acid gave similar compounds, but in lower yields. D-Xylose afforded (9), (11), (12), (14), (18), and (19), and D-arabinose afforded the same products apart from (12). It was considered likely that many of the compounds isolated from the treatment of pentoses and uronic acids under these slightly acidic conditions are intermediates in colour formation during heating and ageing of cellulosic material containing xylans and other polysaccharides possessing uronic acids and pentoses as structural units.

Syntheses of acetoxydihydromaltol acetate (21) and dihydromaltol (22) have been described. These compounds were required to establish the structures of some pyrolysis products from amine-hexose systems and for studies of the non-enzymic browning of sugars.

D-Erythrose and n-threose were both transformed into D-glycero-tetrulose (23) in boiling pyridine. Evidence was presented to show that only the 1,2-enediol, but not the 2,3-enediol, was formed during the rearrangement.

(Continues…)Excerpted from Carbohydrate Chemistry Volume 6 by J. S. Brimacombe. Copyright © 1973 The Chemical Society. Excerpted by permission of The Chemical Society.
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