THE STRUCTURE OF A SYNTHETIC ARABINAN

1965 ◽  
Vol 43 (4) ◽  
pp. 924-927 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau

Hydrolysis of the fully methylated synthetic arabinan showed it to have a highly branched structure in which about 16% of the terminal units were furanose and 2,3-di-O-methyl-L-arabinose was the principal di-O-methyl ether. A method has been developed whereby mixtures of isomeric di- or mono-O-methyl arabinoses may be qualitatively analyzed by successive borohydride reduction, periodate oxidation, and borohydride reduction. The resulting fragments may be separated directly by vapor phase chromatography or by paper chromatography after demethylation.


1965 ◽  
Vol 43 (6) ◽  
pp. 1738-1745 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau

A synthetic L-rhamnan containing both rhamnofuranosyl and rhamnopyranosyl units has been used as a model substance in the application of vapor phase chromatography (v.p.c.) to the study of the structure of rhamnose containing polysaccharides. Groups of isomeric methylated sugars obtained from the methylated rhamnan were analyzed by converting them to methylated alditols which had widely different retention times. A Smith periodate degradation of the rhamnan gave 1,2-dihydroxypropane, 1-deoxy-D-erythritol, L-rhamnose, and 5-deoxy-L-arabinose, which were separated by paper chromatography. There were also obtained l-deoxy-3-O-(α-L-rhamnopyranosyl)-D-erythritol and the β-anomer, and 1-deoxy-2-O-(L-rhamnopyranosyl)-D-erythritol, separable by v.p.c. as their trimethylsilyl ethers. 1-Deoxy-D-erythritol was synthesized and characterized as the tri-p-nitrobenzoate. Of the terminal units in the synthetic rhamnan 35% were furanose and 2,3-di-O-methyl-L-rhamnose constituted 75% of the dimethyl fraction indicating that the principal linkage was (1 → 4).



1965 ◽  
Vol 43 (1) ◽  
pp. 30-39 ◽  
Author(s):  
C. T. Bishop ◽  
M. B. Perry ◽  
F. Blank ◽  
F. P. Cooper

A group of polysaccharides, called galactomannans I, were precipitated as their insoluble copper complexes from aqueous solutions of the crude polysaccharides obtained from each of the organisms designated in the title. The five galactomannans I were homogeneous under conditions of electrophoresis and ultracentrifugation and had high positive specific rotations. The major constituent monosaccharide was D-mannose; amounts of D-galactose ranged from nil for the polysaccharide from T. rubrum to 13% for that from T. schönleinii. Methylation and hydrolysis of the five galactomannans I yielded varying amounts of the following: 2,3,5,6-tetra-O-methyl-D-galactose (not present in the products from T. rubrum), 2,3,4,6-tetra-O-methyl-D-mannose, 2,3,4-tri-O-methyl-D-mannose, 2,4,6-tri-O-methyl-D-mannose, 3,4-di-O-methyl-D-mannose, and 3,5-di-O-methyl-D-mannose. Periodate oxidation results agreed with the methylation studies. The gross structural features of each galactomannan I appear to be the same, namely, a basic chain of 1 → 6 linked α-D-mannopyranose units for approximately every 22 of which there is a 1 → 3 linked α-D-mannopyranose residue. Branch points occur along the 1 → 6 linked chain at the C2 positions of the D-mannopyranose units and once in every 45 units at the C2 position of a 1 → 6 linked D-mannofuranose residue. The D-galactose in the polysaccharides is present exclusively as non-reducing terminal furanose units; non-reducing terminal units of D-mannopyranose are also present. The variations in the identities and relative amounts of the non-reducing terminal units were the only apparent differences in the gross structural features within this group of polysaccharides.



1971 ◽  
Vol 49 (19) ◽  
pp. 3238-3239 ◽  
Author(s):  
Jan Kovář ◽  
Hans H. Baer

Crystalline 3-deoxy-3-nitro-α-D-xylose (5) was obtained in 40% over-all yield by periodate oxidation of 3-deoxy-1,2-O-isopropylidene-3-nitro-α-D-glucofuranose (2) followed by borohydride reduction and acid hydrolysis. In addition to the intermediate 3-deoxy-1,2-O-isopropylidene-3-nitro-α-D-xylofuranose (4), a small amount of an isomer probably having the D-ribo configuration was isolated. The title compound (5) was also obtained by hydrolysis of its methyl β-pyranoside (1).



1962 ◽  
Vol 40 (2) ◽  
pp. 348-352 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau

By determining the amount of formaldehyde produced on periodate oxidation of borohydride-reduced apple- and cherry-wood xylans the degree of polymerization was shown to be 155 and 100 respectively. Acid hydrolysis of the polyols obtained by periodate oxidation and borohydride reduction gave ethylene glycol in amounts indicating that these xylans have a small degree of branching. Mild acid hydrolysis of the polyols demonstrated that in these xylans D-glucuronic acid as well as 4-O-methyl-D-glucuronic acid was present and that some of the former occupied non-terminal positions.



1958 ◽  
Vol 36 (5) ◽  
pp. 755-762 ◽  
Author(s):  
G. A. Adams

A water-soluble polysaccharide isolated from white spruce wood contained D-galactose, L-arabinose, and D-xylose in a molar ratio of 21:3:1. Hydrolysis of the fully methylated polysaccharide yielded 2,3,5-tri-O-methyl-L-arabinose (12 moles); 2,3,4,6-tetra-O-methyl-D-galactose (29 moles); 2,3,4-tri-O-methyl-D-galactose (34 moles); 2,6-di-O-methyl-D-galactose (0.5 moles); 2,4-di-O-methyl-D-galactose (45 moles); 2,3-di-O-methyl-D-xylose (5 moles); and monomethyl xylose (1 mole). When oxidized by periodate the polysaccharide consumed 1.18 moles of oxidant, and yielded 0.56 moles of formic acid per mole of anhydro-D-galactose. The D-xylose was attributed to the presence of a xylan mixed with the arabogalactan in the original polysaccharide preparation. The methylation and periodate oxidation data showed that the arabogalactan possessed a highly branched structure with the anhydro-D-galactose units being joined by 1 → 3 and 1 → 6 glycosidic bonds. All of the L-arabinose was present in the furanoside form as non-reducing terminal units.



1953 ◽  
Vol 31 (9) ◽  
pp. 814-820 ◽  
Author(s):  
R. U. Lemieux ◽  
H. F. Bauer

Periodate oxidation of any one mono-O-methylglucopyranose and alkaline hydrolysis of the product yields a substance which can be positively distinguished by paper chromatography from the products formed under the same conditions from the other mono-O-methylglucopyranoses. Thus, the components of a mixture of the mono-O-methylglucopyranoses can be readily identified. The method appears useful for the identification of di-O-methylglucoses. Reduction with sodium borohydride prior to periodate oxidation renders the method useful for the identification of tri-O-methylglucoses. The potential value of the method, which can be used on a microscale, is illustrated by an application to the characterization of the O-methylglucoses derived from a water-soluble O-methyl-cellulose



1962 ◽  
Vol 40 (12) ◽  
pp. 2204-2213 ◽  
Author(s):  
A. Misaki ◽  
S. Kirkwood ◽  
J. V. Scaletti ◽  
F. Smith

The extracellular polysaccharide isolated from cultures of Xanthomonas oryzae is composed of D-glucose (5 molecular proportions), D-glucuronic acid (2 molecular proportions), and D-mannose (5 molecular proportions). Acid hydrolysis of this polysaccharide, which contains 0.3% combined pyruvic acid, yields 2-O-β-D-glucopyranosyluronic acid D-mannose, which has been characterized as its crystalline fully methylated β-glycoside. Hydrolysis of the methylated polysaccharide gives 2,3,4,6-tetra-O-methyl-D-mannose (3 molecular proportions), 2,3,4-tri-O-methyl-D-glucuronic acid (1 molecular proportion), 2,3,6-tri-O-methyl-D-glucose (4 molecular proportions), 3,4,6-tri-O-methyl-D-mannose (2 molecular proportions), 2,6-di-O-methyl-D-glucose (3 molecular proportions), 2,3-di-O-methyl-D-glucose (1 molecular proportion). The polyalcohol derived from the polysaccharide by periodate oxidation followed by sodium borohydride reduction gives upon acid hydrolysis glycerol (2 molecular proportions), erythritol (1 molecular proportion), and D-glucose (1 molecular proportion). The general structural significance of these findings is discussed.





1969 ◽  
Vol 47 (21) ◽  
pp. 3931-3934 ◽  
Author(s):  
Walter Sowa

L-Glucurone (2) was readily prepared on a small scale by treatment of D-glycero-D-gulo-heptono-lactone (1) with a molar equivalent of periodic acid; thin–layer chromatography was used for its isolation. On a larger scale pure crystalline L-glucurone was obtained in over 80% yield from 3,5;6,7-di-O-isopropylidene-D-glycero-D-gulo-heptonolactone (4) in two steps consisting of concomitant hydrolysis and oxidation of 4 with periodic acid followed by treatment of the intermediate oxidation product with trifluoroacetic acid. L-Glucose was prepared from L-glucurone by borohydride reduction and hydrolysis of the 1,2-O-isopropylidene derivative. Since 1 was derived from D-glucose, the result of this series of reactions was the conversion of D-glucose into its enantiomer L-glucose.



1966 ◽  
Vol 44 (11) ◽  
pp. 1275-1282 ◽  
Author(s):  
V. Zitko ◽  
C. T. Bishop

Fractions of sunflower pectic acid containing 89.8%, 94.2%, and 91.4% of D-galacturonic acid were carboxyl reduced as their methyl or ethylene glycol esters by potassium borohydride. Critical assessment of the effects of three different solvents (water, 80% aqueous dimethyl sulfoxide, and 80% aqueous methanol) on the efficiency of reduction showed that the latter solvent was best. The reductions caused a decrease in the degree of polymerization from 270 to 21. Measurement of the rates of hydrolysis of partially reduced pectic acids containing 90%, 41.6%, 19.9%, 11.0%, and 0.65% of D-galacturonic acid showed that the rate of hydrolysis was directly related to the proportion of galacturonosidic linkages present. Methylation and hydrolysis of the carboxyl-reduced pectic acid fractions yielded 2,3,4,6-tetra-O-methyl-D-galactose and 2,3,6-tri-O-methyl-D-galactose in an approximate molar ratio of 1:20. Results of the periodate oxidation of the carboxyl-reduced pectic acid supported the conclusion inferred from the methylation results that the pectic acid was a linear polymer of 1 → 4 linked α-D-galacturonic acid units.



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