Acyl glycosides glycosyl halides

A treatment of the many types of replacement reaction which have received study by carbohydrate chemists would of necessity be superficial and thus defeat the present purpose. Instead, an attempt will be made to gather all information which sheds light on the mechanisms of a few types of reaction. The reactions of 0-acyl derivatives of sugars, glycosides, and glycosyl halides were chosen because of the central role these substances play in carbohydrate chemistry. 

In an extension of this method, Koenigs and Knorr subsequently reported that reaction between acylated glycosyl halides (bromides, chlorides, or iodides) with alcohols, in the presence of silver promoters (oxide or carbonate) furnished 1,2-trans alkyl glycosides. 

Scheme 16.9 Preparation of O-glycosides of 2-amino-2-deoxysugars. (A) Use of N-acyl-protected donors 27 results in 1,2-trans glycosylation due to neighboring group participation. (B) 1,2-cis glycosylation products 32 from ji-glycosyl halides or (C) by in situ anom-...

The aryl glycosides (62) have been obtained using arylmagneslum bromides with acylated pentofuranosyl halides.Intramolecular reaction of substituted-benzylated glycosyl acetates in presence of... 

---