336. The structure of Acacia pycnantha gum

Aspinall, G. O.; Hirst, E. L.; Nicolson, A.

doi:10.1039/jr9590001697

Cited by 21 publications

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“…There is similar evidence for the existence of 2-0-substituted L-arabinofuranose residues in the arabinose-containing side chains of other Acacia gums (3,4), mesquite gum (5), lemon gum (6), and of Agave arlzericana gum (7) as well as in the arabinogalactan from gum tragacanth (8). We report now the isolation and characterization from A. nilotica gum of a new crystalline arabinobiose, 2-0-P-L-arabinofuranosyl-L-arabinose, in addition to 3-0-P-L-arabinopyranosyl-L-arabinose, which has been characterized from other Acacia gums (2,9).…”

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confidence: 53%

Isolation of two arabinobioses from Acacia nilotica gum

Chalk¹,

Stoddart²,

Szarek³

et al. 1968

Can. J. Chem.

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A new, crystalline arabinobiose, 2-0-p-L-arabinofuranosyl-L-arabinose has been isolated from A. nilotica gum. Another arabinobiose, 3-0-!3-L-arabinopyranosyl-L-arabinose, found previously in other Acacia gums, was also present.Canadian Journal of Chemistry, 46, 231 1 (1968) Previous investigations (1) on the structural features of Acacia nilotica gum have shown it to contain galactose, arabinose, rhamnose, and four aldobiouronic acids, 6-0and 4-0-(4-0-methyl-a-D-glucopyranosyluronic acid)-D-galactose. More recently, a structural investigation of Acacia arabica gum (2) led to the isolation and characterization of 3,5-di-0-methyl-L-arabinose from the 0-methyl derivative of the gum. There is similar evidence for the existence of 2-0-substituted L-arabinofuranose residues in the arabinose-containing side chains of other Acacia gums (3, 4), mesquite gum (5), lemon gum (6), and of Agave arlzericana gum (7) as well as in the arabinogalactan from gum tragacanth (8). We report now the isolation and characterization from A. nilotica gum of a new crystalline arabinobiose, 2-0-P-L-arabinofuranosyl-L-arabinose, in addition to 3-0-P-L-arabinopyranosyl-L-arabinose, which has been characterized from other Acacia gums (2, 9).The purified sample of A. nilotica gum, which was treated with 1,1,2-trichloro-l,2,2-trifluoroethane (Genetron) (10) to remove most of the proteinaceous material, gave one peak on freeboundary electrophoresis in borate and veronal buffers. Autohydrolysis of the acid form of the gum resulted in the release of rhamnose, arabinose, a trace of galactose, and the two arabinobioses mentioned above. The first was characterized as the crystalline hemihydrate of 2-0-P-Larabinofuranosyl-L-arabinose. The facile acid hydrolysis of the disaccharide indicated the presence of a furanosyl linkage, and a negative colorimetric test with triphenyltetrazolium chloride reagent (11) suggested that the reducing arabinose residue was 2-0-substituted. These indications were confirmed by the isolation and characterization of 3,4-and 3,5-di-as well as 2,3,5-tri-0-methyl-L-arabinose from the hydrolyzate of the methylated disaccharide. In accordance with the structure proposed for the derived glycitol, periodate oxidation yielded 0.94 mole/ mole of formic acid and 0.97 mole/mole of formaldehyde, and consumed 3.06 mole/mole of periodate. The values for the specific optical rotations of the disaccharide (+ 148") and of the reduced disaccharide (+69") suggest that the configuration of the 1+2-linkage is P. Further evidence for this assignment follows from the fact that the synthetically prepared a isomer has [a], -8.5". Although an attempted condensation of 2,3,5-tri-0-benzoyl-a-L-arabinofuranosyl bromide (12) with 1 ,3,5-tri-0-benzoyl-P-Larabinofuranose (12) was unsuccessful, the former compound did condense with benzyl 3,4-0-isopropylidene-P-L-arabinopyranoside (1 3) in anhydrous benzene in the presence of silver oxide, iodine, and a drying agent to give benzyl 2-0-(2,3,5-tri-0-benzoyl-a-L-arabinofuranosy1)-3,4-0-isopropylidene-P-L-ar...

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supporting

confidence: 53%

Isolation of two arabinobioses from Acacia nilotica gum

Chalk¹,

Stoddart²,

Szarek³

et al. 1968

Can. J. Chem.

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“…Methylation analyses have shown that L-Ara units may occur other than as single substituents on D-xylosyl residues in the chain (6,7,28,448) partial hydrolysis and methylation studies and, in one instance, by the isolation of 100 after selective oxidation of the primary alcohol groups in L-Ara/residues present in the xylan from rye flour (454). Enzymatic hydrol ysis of xylans from various sources have yielded, inter alia, the trisaccharides 101 (455) and 102 (456) and tetrasaccharides 103 (456) and 104 (457).…”

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confidence: 98%