Glucose dimethyl acetal

Anhydro-trimethyl-D- Methyl 3,6-anhydro-/9-r>-glucose dimethyl acetal (R=Me) galactopyranoside... 

The words acetal and thioacetal are written after the name of the parent sugar as in D-glucose dimethyl acetal 4.33 and D-glucose dimethyl dithioacetal 434. 

In addition, aldc%do-D-glucose dimethyl acetal is hydrolyzed by dilute mineral acids at 40°. 

The 2,3 5,6- and 3,4 5,6-di-0-isopropylidene derivatives of D-glucose dimethyl acetal were obtained when D-glucose was treated at room temperature first with acidified methanol and then with 2,2-dimethoxypropane (or acetone). ... 

At the same time, in this laboratory, we detected the dimethyl acetals of D-xylose and D-glucose by chromatographic resolutions of the products of methanolsis of labelled free sugcirs, and we have, likewise, concluded that they are not primary products but are formed either concurrently with the furanosides or, more probably, from them 8). Fig. 3 illustrates the variations of the main components of the reaction of D-xylose as determined by radiochemical counting of the chromato-graphically resolved components (the pyranosides were vmresolved under the conditions used), and in Fig. 4 the concentration of the acetal is... 

Each sugar can yield two glucosides (oc and /3), since the carbon to which the methoxyl group becomes attached is in that way rendered asymmetric. It is assumed that each sugar first forms a dimethyl-acetal, which loses alcohol to yield the glucoside. In the following preparation it is the y.-glucose which preponderates in the product. 

Cytidin- -dimethylester XII/2, 272 Cytidin-5 - -morpholid XII/2, 402 Cytidin- -propylester XII/2, 272 -decylamid-dichlorid XII/2, 385 -decylamid-diphenylester XII/2, 435 -decylester XII/2, 179 E2, 500, 561 -decylester-dichlorid XII/2, 213f. Desoxy-adenosin-5 - XII/2, 207 Desoxy-cytidin-3 - XII/2, 180 Desoxy-cytidin-5 - -morpholid XII/2, 402 2-Desoxy-3,4-di-0-benzoyl-D-ribose-dimethyl-acetal-5- -diphenylester XII/2, 194 -6-(desoxy-D-gluconsaureester) XII/2, 209 2-Desoxy-D-glucose-6- XII/2, 194... 

The most typical acetals are those in which the carbonyl group belongs to a nonsugar component (Fig. 2-16), although the dimethyl acetal of glucose represents another type. Some examples of acetals are given in Fig. 2-1 7. 

The relative reactivity toward sodium of the hydroxyl groups at the various carbon atoms of a sugar has been exploited in order to prepare selected derivatives. By the addition of one molar equivalent of sodium to 4,5-0-isopropylidene-D-fucose dimethyl acetal in ethyl ether, followed by benzyl chloride, Schmidt and Wernicke were able to isolate a 42 % yield of 2-0-benzyl-4,5-0-isopropylidene-D-fucose dimethyl acetal. Freudenberg and Noe reacted molar equivalents of 1,2-0-isopropylidene-a-D-glucofuranose and sodium in boiUng dioxane. Subsequent reaction with benzyl chloride, and acetylation, gave a 29 % yield of crystalline 5,6-di-0-acetyl-3-0-benzyl-1,2-0-isopropylidene-a-D-glucose. 

The Behavior of the Dimethyl Acetals of Glucose and Galactose Under Hydrolytic and Glycoside-forming Conditions, M. L. Wolfrom and S. W. Waisbrot, J. Amer. Chem. Soc., 61, 1408-1411 (1939). 

Fig. 11 Side products in the sucrose-to-lactate (green) convta ion in MeOH and their raigin blue retro-aldol of glucose (see Sect. 7) red methanolysis of sucrose ot acetalizatirai of glucose black dehydration of sugars to HMF, furan ethers and humins. MMHB methyl methoxy-2-hydroxybutanoate, MVG methyl vinyl glycolate, MHB methyl-2-hydroxybutanoate, GADMA glycolaldehyde dimethyl acetal. HG = hydrogenation...

Anhydro-L-mannose dimethyl acetal derivative (l6) has been synthesized from the D-glucose derived 2,5-anhydro-3,6-dl-0-tosyl-L-Idose dimethyl acetal (17) (Scheme 5) and converted to C-nucleo-sides. 

A cooled soln. of / -D-glucose pentaacetate in methylene chloride treated 10 min. at 0° with 1-2 moles SnCl4, then 1-2 moles N,N-dimethylformamide dimethyl acetal added, and stirred 2-3 hrs. -> methyl 2,3,4,6-tetra-0-acetyl-/ -D-gluco-pyranoside. Y 83%. F. e., also with 0-alkyllactims, s. S. Hanessian and J. Banoub, Tetrah. Let. 1976, 657 di- and pseudodi-saccharides s. ibid. 1976, 661. 

Nucleophilic participation by the hydroxyl group has been noted in acid-catalyzed studies of systems other than carboxyl groups. In dilute aqueous acid solution, methyl furanosides [e.g., (248)] were formed by ring closure during hydrolysis of the acetal bonds of the acyclic dimethyl acetals of glucose (247) and galactose.It was estimated that the rates of these cyclizations were faster than the expected unassisted rates of hydrolysis. 

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