Dextrans acetolysis

Matsuda and coworkers studied first the acetolysis of isomaltose [a-D-(l—>6)] and nigerose [d-(W3)] the former was completely broken down, but the latter was not degraded. Use of the same conditions on several dextrans permitted them to isolate nigerose, proving the presence of (1— 3)-links, as well as kojiobiose [a-D-(l— 2)]. 

Fujimoto and coworkers determined that the order of stabilities to acid hydrolysis of D-glucopyranosidic linkages is reversed under the conditions of acetolysis this may be due to steric factors affecting the acetylium ion. In consequence, acetolytic, degradative procedures have enabled secondary-linked disaccharide fragments to be obtained from a large number of native dextrans. The o-D-linked disaccharides obtained by acetolysis and deacetylation of a cross-section of dextrans are listed in Table II. The results may be seen to complement data from periodate... 

Similar branched or linear segments (or both see structure 14) are also present in Leuconostoc mesenteroides NRRL B-1307 dextran/" as nigerotriose (15) and the branched trisaccharide O-a-n-glucopyranosyl (l->6)-0-[a-D-glucopyranosyl-(l- 3)]-D-glucose (16) were obtained following acetolysis of the dextran. 

On acetolysis and deacetylation, Leuconostoc mesenteroides NRRL B-1299S dextran gave, amongst other oligosaccharides, trisaccharide 9... 

The isomeric trisaccharides 7, 8, and 9 have, in addition, been obtained by acetolysis and deacetylation of L. mesenteroides NRRL B-1397 dextran,and provide evidence that some branches are composed of 2-0-a-isomaltosyl (or larger) groups, as shown in structure 21. 

Five tetrasaccharides have been isolated from the acetolysis products of the insoluble dextran elaborated by Leuconostoc mesenteroides NRRL B-1299. Structural identification of the oligomers demonstrated that the (1 -> 3>-Hnl ed a-D-glucosyl residues occur in sequences, thus supporting the theory that there is a relationship between lower solubility and sequences of (1 - 3)-linked residues in the dextrans. A number of dextrans have been hydrolysed by an exu-isomaltohydrolase (EC 3.2.1.94) from Arthrobacter globiformis to produce, in addition to isomaltose, one or two pentasaccharides in which an a-i>glucosyl residue is substituted at 0-2,0-3, or 0-4 by an isomaltosyl unit. ... 

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