Isomaltose 3-, octaacetate

The octaacetates of /3-isomaltose, /8-maltose, /3-nigerose, and a-koji-biose were obtained in 80, 55.8, 67, and 64% yields, respectively, by reaction of 50b with the appropriately protected D-glucopyranose derivatives in the presence of silver perchlorate and s-collidine, followed by hydrogenolysis and acetylation. /3-Isomaltose octaacetate was also obtained in 79.4% yield by the reaction of 50b with 1,2,3,4-... 

B. Lindberg, Action of strong acids on acetylated glycosides. V. Synthesis of (S-isomaltose octaacetate, Acta Chem. Scand., 3 (1949) 1355-1357. 

Structure. The methylation studies of Georg and Pictet 64) established their preparation to be a 6-0-D-glucopyranosyl-D-glucose (55). (See Synthesis). Although it follows from the nonidentity of isomaltose with gentiobiose that the former must be an a-D-glucoside, the complete proof of structure of isomaltose came only after the preparation of crystalline, well-defined derivatives. Thus, Wolfrom, Georges, and Miller (55) demonstrated the probable identity of their crystalline isomaltose octaacetate (from a 1 6... 

Definite proof that the interchain linkage is 6 —> 1-a-D has been obtained by Wolfrom and coworkers,91 who have isolated crystalline /3-isomaltose [6-0-(/3-D-glucopyranosyl)-D-glucose] octaacetate (in 1 % yield) from the mild acetolysis of waxy maize starch and have presented evidence that... 

Wolfrom and coworkers85-88 prepared /S-isomaltose (40) and /3-gentio-biose octaacetates (6) in 55 and 6% yields, respectively, by the reaction of 3,4,6-tri-0-acetyl-2-0-nitro-/3-D-glucopyranosyl chloride (39)... 

In his attempts to obtain isomaltose in crystalline form, Dr. Thompson was uniformly unsuccessful, but his persistence bears witness to his patience and indefatigability. He kept samples of the disaccharide, carefully prepared by Zempl6n deacetylation of the crystalline octaacetate, for over ten years under all manner of different conditions, in a variety of solvents, and at temperatures varying from that of a warm oven to that of a deepfreeze cabinet. One sample he kept under magnetic stirring for two years, and, every few weeks, he would evaporate the solvent and replace it with a different one. All attempts were of no avail, but patience of this kind rewarded him in many other endeavors. 

Preparation. Isomaltose has been obtained as the crystalline i3-octaacetate in 5% yield from partial acid hydrolyzates of a bacterial dextran (0) from Taka-amylase hydrolyzates of amylopectin (50) as the crystalline a- and /S-octaacetates and the octa-p-nitrobenzoate from the acid hydrolyzates of glycogen (51) and from hydrol (52). It has recently been prepared in 50% yield from enzymic hydrolyzates of the dextran from Leuconostoc mesenteroides by a separation procedure employing charcoal-column elution (55). 

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