Vinyl glycosides

Vinyl glycosides are difficult to prepare by conventional vinylation procedures although it has been reported that 2,3 5,6-di-0-isopropyl-idene-D-mannofuranose with acetylene in the presence of potassium hydroxide afforded vinyl mannosides A much better transvinylation procedure was used by Fletcher and coworkers as shown in Scheme 12 to give mixed products which, after chromatographic separation, were converted to vinyl a- and p-D-glucopyranosides by treatment with sodium in liquid ammonia... 

L. Cottier, G. Remy, and G. Descotes, Photochemical synthesis of O-vinyl glycosides and their transformation into C-branched sugars, Synthesis p. 711 (1979). 

P. Rollin, V. Verez Bencomo, and P. Sinay, Use of selenium in carbohydrate chemistry Formation of vinyl-glycosides, Synthesis p. 134 (1984). 

Glycosides made from y-hydroxy ketones undergo photoelimination to give O-vinyl glycosides, which can undergo a Claisen rearrangement in certain deoxy sugars [68]. 

The Tebbe reagent (4.85) has found applications in reactions of sugars because it methyle-nates carbonyls without racemizing a chiral a-carbon. Thus, methylenation of the formyl functions of 1-0-formylglycoside 4.91 with 4.85 produced 1-0-vinyl glycosides 4.92. 

Boons G-J, Isles S. Vinyl glycosides in oligosaccharide synthesis (part 1) a new latent-active glycosylation strategy. Tetrahedron Lett. 1994 35 3593-3596. 

SCHEME 4.31 Vinyl glycosides in latent-active glycosylation. 

Bai, Y, Boons, G-J, Burton, A, Johnson, M, Haller, M, Vinyl glycosides in oligosaccharide synthesis (part 6) 3-buten-2-yl 2-azido-2-deoxy glycosides and 3-buten-2-yl 2-phthalimido-2-deoxy glycosides as novel glycosyl donors, J. Carbohydr. Chem., 19, 939-958, 2000. 

Boons, G J, Heskamp, B, Hout, F, Vinyl glycosides in ohgosaccharide synthesis a strategy for the preparation of trisaccharide hbraries based on latent-active glycosylations, Angew. Chem. Int. Ed. Engl, 35, 2845-2847, 1996. 

Isopropenyl glycosides could be activated selectively in the presence of armed NPGs, and that allowed a one-pot synthesis of trisaccharide 322 involving the successive glycosyl coupling of a vinyl glycoside jS-307, and an NPG, 321 (O Scheme 52). 

The allyl glycoside 323, can be considered a latent [177] form of a glycosyl donor which can be efficiently isomerized to the active vinyl glycoside, 324. The isomerization reaction was performed by a rhodium catalyst obtained by treating the Wilkinson s catalyst, (Ph3)P3RhCl,... 

Vinyl glycoside-based latent-active strategy for glycosyl coupling... 

Ac vinyl glycoside donor PMB allyl glycoside acceptor PMB vinyl glycoside donor... 

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