Disaccharides description

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. 

Give an adequately descriptive name of the disaccharide, and draw its Haworth projection formula. 

The names of simple sugars and sugar derivatives can all be abbreviated. This also allows an abbreviated description of the component sugars present in disaccharides, for example. 

Given the Lewis diagrams of two monosaccharides and a description of the bond linking the molecules, draw the Lewis diagram of the resulting disaccharide. 

Identify the disaccharide that fits each of the following descriptions ... 

Monosaccharides, di- and oligosaccharides, and polysaccharides have cumulative conformational descriptors. Because polysaccharides contain as subunits the monomers and dimers, the information on the subunits is usually of interest in the description of the larger molecules as well. However, once the issue of the ring conformation can be regarded as settled, the variables of primary interest for a disaccharide become the torsion angles about the bonds that form the interresidue linkages. 

Disaccharide conformations are determined by their free energies, rather that just their mechanical potential energies, and as in the cases of trehalose and neocarrabiose, the solvent can affect the free energy surface governing conformational equilibrium. A more useful description of disaccharide energetics would be a Ramachandran conformational potential of mean force (pmf) which included not only entropic effects but also the influence of the solvent. 

The glass transition temperatures, fusion temperatures and the heats of fusion of a number of pentoses, hexoses, alditols, and disaccharides have been determined by differential scanning calorimetry. In the course of an investigation aiming at a rigorous description of the thermal events... 

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