Glucopyranose conformation

Glucose binds in both the BII and Bill crystal forms in the deep cleft separating the two lobes of each subunit. Glucose appears to bind in the C-l (chair equatorial) a-D-glucopyranose conformation (73). All of the hydroxyls, except the 1-hydroxyl, are thus in an equatorial position. Protein side chains are hydrogen bonded to the 3-, 4-, and 6-hydroxyls and possibly to the 1-hydroxyl of glucose. The 2-hydroxyl appears to be pointing toward open space (73). This corresponds nicely with the observed substrate specificity. 

D-glucopyranose conformer, migration of the formate to position 3 could account for the results observed. 

Tellimagrandin I (36) Tellima grandiflora Rosa sp. Quercus sp. Fuchsia sp. Camellia japonica Geum japonicum Casuarina stricta Cornus sp. 2,3-bisgalloyl-hexahydroxydiphenic acid linked 2,3 and 4,6 o-glucopyranose conformation-1C (predominantly) 43, 102, 143... 

Isoterchebin (trapain) Cornus sp. TYapa japonica )5-l-O-galloyl 2,3-bisgalloyl dehydrohe-xahydroxydiphenic acid linked 2,3 D-glucopyranose conformation-1C 94... 

Pedunculagin (43) Quercus pedunculata Q. sessiflora (galls) s-( — )-hexahydroxydiphenic acid linked 2,3 and 4,6 D-glucopyranose conformation — c-1 32. 102)... 

Barrows S E, J W Storer, C J Cramer, A D French and D G Truhlar 1998. Factors Controlli Relative Stability of Anomers and Hydroxymethyl Conformers of Glucopyranose. Journal Computational Chemistry 19 1111-1129. 

Make a molecular model of the chair conformation of 3 D glucopyranose... 

All the ring substituents m p D glucopyranose are equatorial m the most stable chair conformation Only the anomenc hydroxyl group is axial m the a isomer all the other substituents are equatorial... 

DrawjS-L-glucopyranose in its more stable chair conformation. 

The Haworth representation implies a planar ring. However, monosaccharides assume conformations that are not planar these may be represented by Haworth conformational formulae. The nomenclature of conformations is described in 2-Carb-7. For example, (5-D-glucopyranose assumes a chair conformation ... 

Figure 5-1. Definition of chair conformation in /J-glucopyranose. Reproduced with permission from reference [66]. Copyright Elsevier 2004...

In contrast to the D-glucopyranose-D-glucofuranose equilibrium, in which the former preponderates, compound 4, because of its more favorable conformation, is thermodynamically more stable than D-glucopyranurono-6,3-lactone (9). 

Figure 9.9 Conformation of D-glucose. The pyranoses adopt a non-planar ring conformation and the chair form with the highest number of equatorial rather than axial hydroxyl groups is favoured. It should be noted that a-D-glucopyranose, in contrast to /3-D-glucopyranose, has an axial hydroxyl group.

Spherical polar coordinates are used for conformational representation of pyranose rings in the C-P system. Unlike the free pseudorotation of cyclopentane, the stable conformations of cyclohexane conformers are in deeper energy wells. Even simong the (less stable) equatorial (6 = 90 ) forms, pseudorotation is somewhat hindered. Substitutions of heteroatoms in the ring and additions of hydroxylic or other exocyclic substituents further stabilize or destabilize other conformers compared to cyclohexane. A conformational analysis of an iduronate ring has been reported based on variation of < ) and 0 (28), and a study of the glucopyranose ring... 

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