Halide glycopyranosyl

Acylated glycosyl thiocyanates are made by treatment of acylated glycopyranosyl halides with potassium thiocyanate.30 Reaction at —40° with a Grignard reagent affords alkyl or aryl 1-thioglycosides.54... 

Glycopyranosyl halides react with ethyl acetoacetate and pentan-2,4-dione under soliddiquid phase-transfer catalytic conditions, using potassium phosphate as the base, providing the C-alkylated derivatives (40-60%) ]94],... 

Reaction of glycopyranosyl halides with activated methylene groups... 

Reactions at the Anomeric Center of Acetylated Glycopyranosyl Acetates and Halides. R. U. Lemieux, Proc. Chem. Soc., 10 (1957). 

Initial studies58 had indicated that 1-glycopyranosyl nucleosides prepared by the mercuri procedure are identical with those prepared by the Hilbert-Johnson method, when similar poly-O-acylglycosyl halides are employed. The applicability of the mercuri procedure to the synthesis of 1-aldopento-furanosyl nucleosides was demonstrated by the preparation of 5 -methyl-uridine (LIV). Condensation of dithyminylmercury (LI) with tri-O-benzoyl-... 

Even at the inception of ALPH, however, there was one system already known where the pattern of reactivity apparently contradicted it. It was well known in carbohydrate chemistry that protected a-glycopyranosyl halides were less labile than their p-anomers, at least for the common sugars in the D series (Haynes and Newth, 1955). The pyranose ring in these compounds is strongly biased towards the 4CX conformation, so that the a-halides are axial and the P-halides are equatorial. The a-halides have an antiperiplanar... 

Poly-O-acetyl-glycopyranosyl Halides J0 ki(sec. ) Proportion of substitution 10 kt(l. mole sec. )... 

Dubois, E, Beau, J M, Synthesis of C-glycopyranosyl compounds by a palladium-catalyzed coupling reaction of 1-fributylstannyl-D-glucals with organic halides, Carbohydr. Res., 228, 103-120, 1992. 

Other miscellaneous 1-thio derivatives convertible to thioaldoses are glycosyl thioimidocarbonates and diglycosyl disulfides [1], Their s)uitheses are similar to the ones described above, i. e., displacement reactions of an acylated glycopyranosyl halide with a thionucleophile, an... 

Figure 4. The important interactions in glycopyranosyl halides with axial C-Cl bond, and the corresponding expression for the energy difference between axial and equatorial anomers...

N-glycosylation reactions of glycopyranosyl halides and silylated uracil or thymine in the presence of silver trifluoroacetate gives exclusively one ano-mer (in solid-solid conditions), while the fusion method lead to an anomeric mixture [Eq. (43)] [75]. 

Nakajima and coworkers also prepared 1,2-cis-glycosides, including kanosamine, kanamycin A,109 and paromamine derivatives,110 by the reaction of appropriately protected a-D-glycopyranosyl halides of aminodeoxy-D-glucoses with deoxystreptamine derivatives in the presence of silver perchlorate, silver carbonate, and Drierite in benzene or chloroform containing 10-20% of 1,4-dioxane. 

When a 1,2-trans-glycopyranosyl halide (99) is used as the starting material, the trans-glycopyranoside (93) with retention of configuration at the anomeric carbon atom or the orthoester147,148 (94) (or both) is mainly obtained. The use of mercury(II) salts, or a combination of a silver salt and iodine,26-28 often favors the formation of the 1,2-trans-glycopyranosides (93). 

As mentioned earlier, 1,2-cis-glycopyranosides are usually obtained from glycopyranosyl halides having a nonparticipating group at C-2. In model experiments, the solvolysis of glycopyranosyl halides has been studied in detail.94 140,141,149-154 In general, it is found that, in the... 

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