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Ortho esters sugar

From these results, it follows that the predominance of these pathways over that of the ortho-ester route to afford nitrogenated sugars... [Pg.101]

Ortho-esters at position 1,2- of sugars are more easily prepared than the corresponding acetals as an exchange of both functional groups is possible, 1,2-O-alkylidene derivatives can be prepared by the reaction of these ortho-esters with the appropriate carbonyl reagent in strictly anhydrous conditons and in the presence of an acid [87]. [Pg.12]

A. F. Bochkov and Ya. V. Voznyi, Sugar ortho esters. Part 8. Synthesis of 4-O-methyl-D-glucuronic acid derivatives, Carbohydr. Res., 32 (1974) 1-8. [Pg.192]

Ohtake, H, Ichiba, N, Ikegami, S, A highly stereoselectiye construction of (3-glycosyl linkages by reductiye cleayage of cyclic sugar ortho esters, J. Org. Chem., 65, 8171-8179, 2000. [Pg.198]

Ohtake, H, Li, X L, Shiro, M, Ikegami, S, A highly efficient and shortcut synthesis of cychtol derivatives via spiro sugar ortho esters. Tetrahedron, 56, 7109-7122, 2000. [Pg.394]

The di-O-tosylates (prepared by action of tosyl chloride in pyridine) are reduced with zinc (Nal/Zn route e Tipson-Cohen reaction) [13]. Cyclic ortho-esters (prepared by reaction of the diol with ethyl orthoformate) are transformed into olefins by simple heating in the presence of acids (Eastwood reaction, route b) [14]. Cyclic thiocarbonates (obtained by reaction of a diol with thiophosgene or (V,(V -thiocarbonyl-di-imidazole) are reduced to olefin with trimethyl phosphite (Corey-Winter method, route c) [15]. Finally, reduction of vicinal di-xanthates with tri- -butyltin hydride according to the Barton procedure [16] affords olefins via a reductive elimination process route a). The Corey-Winter, Garegg, and Tipson-Cohen methods are most commonly applied for deoxygenation of sugar diols. [Pg.346]

When milder conditions are required for the cyclisation, perhaps because of the presence of a sugar residue, an ortho ester (often activated with acetic... [Pg.481]

Table 8.4 Reduction of sugar ortho esters with LiAIHi/AICIs... Table 8.4 Reduction of sugar ortho esters with LiAIHi/AICIs...
Ortho esters have found occasional use as carboxyl blocking groups in some syntheses [73, 74, 75, 76, 96] particularly where it is necessary to prevent reaction at a carboxyl group with a Grignard reagent at a subsequent stage in a synthesis. An example of an application of this type is in the preparation of (57) in studies allied to the synthesis of the antibiotic mycomycin (33) [96]. An alternative use is illustrated by the synthesis of the amino-sugar muramic acid (58) [74]. [Pg.200]


See other pages where Ortho esters sugar is mentioned: [Pg.97]    [Pg.142]    [Pg.144]    [Pg.144]    [Pg.159]    [Pg.236]    [Pg.124]    [Pg.19]    [Pg.485]    [Pg.133]    [Pg.95]    [Pg.48]    [Pg.125]    [Pg.351]    [Pg.1059]    [Pg.485]    [Pg.249]    [Pg.97]    [Pg.142]    [Pg.144]    [Pg.210]    [Pg.202]    [Pg.159]    [Pg.125]    [Pg.135]    [Pg.111]    [Pg.236]    [Pg.253]    [Pg.253]    [Pg.132]    [Pg.368]    [Pg.19]    [Pg.46]    [Pg.591]    [Pg.343]   


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Ortho esters

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