Glucopyranose conformational inversion

A mathematical method has been described for determining, from independent variables that include the contribution of valence-angle deformation, the potential barrier for conformational inversion in j8-D-glucopyranose. The energy required for the conversion of a chair form to a boat form was calculated to be 13.5 kcal.mole , and the energy required for the reverse process, 6.5 kcal.mole . Ex-... 

D-(+)-galactose (15) is an example of the consecutive numbering of the carbon ring atoms in a monosaccharide (disaccharide see p. 253). Carbohydrates can exist in a cyclic and an acyclic structure. For this reason there is a special position in the structure of a monosaccharide, the carbon atom C-l and so called anomeric center. You can see that there is an equilibrium between er-anomer a-15 and / -anomer /3-15 of D-(+)-glucopyranose over the acyclic aldehyde structure 16. Both are cyclic hemi-acetals. The /Tanomer is the preferred conformation, but there are a few effects, like sterical or stereoelectronical effects (anomeric effect, inverse anomeric effect), which have influence on the a /i rate. 

N.m.r. spectroscopy at 220 MHz has shown that the Ci conformation is adopted by fully benzylated a- and jS-D-glucopyranoses inversion of the configuration at C-5 to give the corresponding L-idopyranose derivatives results in an inversion of conformation also. Two groups have shown that derivatives of methyl or benzyl (methyl 4-deoxy-L-rAreo-hex-4-enopyranosid)uronate [e.g. (447)] adopt half-chair conformations that place the anomeric methoxy-group in... 

---