Sialyl glycosides

II. Regio- and a-Stereoselective Sialyl Glycoside Syntheses Using Thioglycosides of Sialic Acids in Acetonitrile 359... 

Since 1965, a number of attempts for obtaining sialyl glycosides have been achieved [15,16], mainly by the classic Koenigs-Knorr method using Al-acetylneuraminyl halides 2 as glycosyl donors. However, the yield and stereoselectivity of the glycosides with sugar... 

In the following section, our recent development of the regio- and a-stereoselective sialyl glycoside syntheses using thioglycosides of sialic acids in acetonitrile is described. 

II. REGIO- AND a-STEREOSELECTIVE SIALYL GLYCOSIDE SYNTHESES USING THIOGLYCOSIDES OF SIALIC ACIDS IN ACETONITRILE... 

Figure 2 An efficient regio- and a-stereoselective synthesis of mono-sialyl glycosides. (SE = —CH2CH2SiMe3.)...

Therefore, it seems most plausible that the stereospecific generation of the p-aceto-nitrilium ion (d) of Neu5Ac from the oxocarbenium ion (c) holds the key of the re-preponderant formation of sialyl glycosides in acetonitrile. Thus, the reactive nucleophiles, such as OH-6 of 17 have a chance to attack on other intermediates (a) (c) before the complete... 

Figure 3 An efficient regio and a-stereoselective synthesis of oligo-sialyl glycosides.

Special cases (e.g., sialyl glycosides and oligosaccharides glycosides of macro-lide aglycones)... 

Sialic acids are involved in a number of biological processes including cell-to-cell, cell-to-microorganism, -toxin, and -antibody binding. Their importance in these processes, especially those with relevance to human disease states, has led to interest in the synthesis of both natural and modified sialic acids. This review examines the most recent methods used for the synthesis and modification of sialic acids and for the preparation of sialyl glycosides as biological probes of sialic acid-recognising proteins. 

Sialyl glycosides with a carbon linkage have also been prepared. Reaction of peracetylated 2- -chloro-2-deoxy-Neu5AclMe (55) with allyl(tri-7J-butyl) stannane, utilising radical coupling conditions, gave an epimeric mixture of the... 

This versatile method, designed for the regio- and a-stereoseiective sialyl glycoside synthesis, has been further developed to the oligosialyl glycoside synthesis. 

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