Reactions at the Anomeric Center

The endocyclic and acetal intermediates were excluded since experiments conducted in CD3OD showed that anomerization was accompanied by 98% exchange of the methoxyl group and solvent. Stereospecific formation of a glycopyranosidic product from the acetal was excluded by the fact that acidic treatment of it produced only furanosides, which were converted only slowly into pyranosides. The exocyclic intermediate was considered to be the most likely 

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The scope of the acid-catalyzed formation of C-glycosyl compounds has been greatly expanded with the finding that enol ethers and ketene acetals can be used as the carbon source in electrophilic substitution reactions at the anomeric center.126 Treatment of 198 with the trimethylsilyl enol ether derived from cyclohexanone, in the presence of stannic chloride, led to 2-(2,3,5-tri-0-benzoyl-/J-D-ribofuranosyl)cyelohexanone (206), presumably by way of the inter-... 

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

Cl-to-C2 bond, the Cl-acetoxy group of ketose acetates can be expected to participate in replacement reactions at the anomeric center. The retention of configuration obtaining in the mercaptolysis of /3-D-fructopyranose pentaacetate (CXIV) suggests that the 1,2-cyclic ion (CXV) is an intermediate in the reaction. 

Sequential elimination reactions, most of them being dehydration, involving the reaction at the anomeric center often produce various aromatic compounds [235] especially furans which have diverse use [236,237]. Explorations have been continued to open a new route to aromatics based on renewable biomass in place of fossilized material. 

G. H. Veeneman, S. H. van Leeuwen, and J. H. van Boom, Iodonium ion promoted reactions at the anomeric centers. II. An efficient thioglycoside mediated approach toward the formation of 1,2-/ran.v-linkcd glycosides and glycosidic esters, Tetrahedron Lett., 31 (1990) 1331-1334. 

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