Applications as glycosyl donors

Glycosyl Thioimidates - Preparation and Application as Glycosyl Donors... 

The most impressive application of 2-thiopyridyl and 2-thiopyrimidinyl donors is in the area of antibiotics. Thus, Woodward et al. [481] successfully completed the total synthesis of erythromycin by using S Pyrm glycoside of D-desosamine and S Pyr-glycoside of L-cladinose as glycosyl donors to the subsequent glycosylation with erythronalide A. This methodology was also successfully used in the synthesis of oleandomycin [482,483], erythromycin A [484] and erythromycin B [485]. 

These modifications met with only limited success however, they set the basis for the future applications of orthoesters as glycosyl donors. 

The glycals are easily converted into the 1,2-dihalo-derivatives, which in principle can act as glycosyl donors. However, these derivatives have not found wide application in glycoside synthesis, mainly because of the low facial selectivity in the initial addition of the electrophilic species [143-145]. In an example of a successful application, 2-deoxy-2-bromo-a-D-glucopyranosyl bromide [146] has been shown to give predominantly the 2-deoxy-P-D-glucopyranosides in silver-triflate-promoted reactions with alcohols. 

The first application of (9-glycosyl trichloroacetimidates as glycosyl donors for the glycosylation of an acceptor attached to Merrifield resin was reported by our group in... 

This book does not deal with glycosyl fluorides. Indeed, they are mostly synthesis reagents that are used as glycosyl donors in both chemical and enzymatic syntheses of polysaccharides. Another application of glycosyl fluorides is as mechanistic probes... 

A relatively new method, this involves glycosyl phosphites as glycosyl donors (Scheme 6). Independently reported by Schmidt [18] and Wong s groups [19], this method has already found important applications in the synthesis of sialyl derivatives [19]. 

Scheme 6. The use of thioglycosides as glycosyl donors (a) and application (b) of the method in the total synthesis of O-mycinosyltylonide (28). (Nicolaou, 1982) ...

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