Anomeric configuration, glycosyl

Other inverting glucosidases which conform to the pattern of direct hydrolysis of glycosyl fluorides having the correct anomeric configuration, and transglycosylation with inversion if the anomeric configuration is opposite to that of the natural substrates are trehalase from rabbit renal cortex and from the yeast Candida tropicalis, and ) -D-xylosidase from Bacillus pu-milis. ... 

The lack of glycosyl transfer reaction is the class of pectinolytic hydrolases is in agreement with the observed inversion of the anomeric configuration of the newly formed reducing ends of the products. All three polygalacturonases studied here utilize the single displacement mechanism of hydrolysis. 

C-Glycosylation was also effected in the T>-arabino series, by treatment of 2,3,5-tri-O-benzyl-a-D-arabinofuranosyl chloride127 (168) with diethyl sodiomalonate. The anomeric diethyl 2-d-arabinofuranosylmalonates were isolated as the acetates (169 and 170), and their anomeric configurations were determined by per-... 

Glycosyl halides, a very important group of carbohydrate derivatives, are commonly prepared14 from per-O-acylated sugars by reaction with hydrogen halides or halides of aluminum or titanium. The selection of the method depends mainly on the anomeric configuration of the substrate, the kind of its O-acyl groups, and the stability of the product to be prepared. 

Scheme 3 Synthesis of P-D-mannosides and P-L-rhammnosides by glycosylation via locked anomeric configuration.

Treatment of the acylated glycosyl halide (bromide or chloride) of the opposite anomeric configuration with silver fluoride in acetonitrile was the method initially developed40 for the synthesis of the less stable anomers, as exemplified by the synthesis of peracylated /S-D-glucopyranosyl fluoride40 from the corresponding a-bromide. It has... 

Glycosyl acceptor Reaction conditions Anomeric configuration (or.fi) Yield (%) Reference... 

Trichloroacetiiiiidate Glycosyl acceptor Reaction conditions Yield (%) Anomeric configuration (a /0 Reference... 

Fig. 6.—Chemical structure of the lipid A backbone of Neisseria meningitidis M986 LPS having polar substituents. The nonglycosylic and glycosylic phosphate groups are substituted by Etn-P to a similar degree (85 vs 80%, w/w). The anomeric configuration of the phosphate has been assigned tentatively as a. R1 = 12 0(3-OH), R2 = 14-O[12 0(3-OH)] (73).

Hodosi, G. Kovac, P., Glycosylation via locked anomeric configuration stereospecific synthesis of oligosaccharides containing the beta-D-mannopyranosyl and beta-L-rhamnopyranosyl linkage. Carbohydr. Res. 1998, 308, 63-75. 

---