Sugar anomeric configuration

Sugar anomeric configurations were formerly derived from chiroptical properties such as the Klyne-Hudson rule. They are now determined by or 13c NMR spectroscopy. 

Note. In cyclic forms of sugars, the configuration at the anomeric chiral centre is defined in relation to the anomeric reference atom (see 2-Carb-6.2). 

The anomeric configurations of the sugar residues were determined by chromium trioxide oxidation [14], Oxidation of the fully acetylated polysaccharide and subsequent monosaccharide analysis by GLC indicated that the D-Xyl units are P-linked (oxidized more rapidly) and that die D-GlcA are a-linked (Table II). 

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. 

A large series of lactones was thus prepared, with variations in the sugar type, the anomeric configuration, mono- or disaccharides, and benzyl protected lactones. The potential of these lactones is illustrated in the... 

A new NMR method for the determination of the anomeric configuration in mono- and disaccharides has been described.18 The protocol is based on the different cross-correlated relaxation between proton chemical shift anisotropy (CSA) and dipolar relaxation for the a and (3 anomers of sugars. Only the ot-anomers show the presence of CSA (HI or Hl )-proton dipole (H1-H2 or Hl -H2 ) in the longitudinal relaxation of the anomeric protons. The method is of special interest for cases in which vicinal coupling constants between HI and H2 in both anomers a and (3 are similar and small, such as D-mannose, and the non-ambiguous description of the anomeric configuration needs additional measurements. 

Several papers describe the preparation of analogs that differ from naturally occurring sugar nucleotides in the anomeric configuration of the glycosyl residue.270,271,297,309 Furthermore, it has been possible to obtain an analog (67) of uridine 5 -(a-D-glucopyranosyl pyrophos-... 

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