Glucopyranosidic ring

C-5 position are less important in both the fly (31) and gerbil. (4) The failure of the a-D-glucopyrano-sides, turanose, palatinose, maltose, maltitol and trehalose to stimulate as well as sucrose or methyl a-Q-glucopyranoside could be attributable to steric hinderance involving the substituents at position C-l of the glucopyranoside ring. 

It has been shown that reaction with cuprammonium is greatly influenced by the position of a substituent group on the glucopyranoside ring.28-29 This is illustrated for monosaccharides of known structure... 

The H and 13C signal assignments of glucopyranoside ring C are derived from the HH COSY and CH COSY diagram ... 

As shown above, in starch the glucopyranoside ring is present in the a-form, while in cellulose the repeating units exist in the P-form. Because of this difference in structures, the enzymes that catalyze the acetal hydrolysis reactions in the biodegradation reactions of each of these two polysaccharides are different for each and are not interchangeable. 

Rg. 1.2. Schematic view of the glucopyranoside ring with the atom numbering and native CyD sizes and the average orientation of the most important atoms and OH groups. 

Reeves RE (1949) Cuprammonium-glycoside complexes. HI. The eonfonnation of the D-glucopyranoside ring in solution. J Am Chem Soe 71 215... 

P2j Z = 2 D, = 1.24 R = 0.05 for 2,421 intensities. This molecule is a cardenolide / -D-glucopyranoside. The pyranoside conformation is 4C4, with Q = 58 pm, 0 = 6°. The terminal lactone ring is planar. The conformation was compared with that of digitoxigenin by means of molecular-mechanics calculations. 

In order to extend this approach to pyran rings, the methyl a- and (I-d-glucopyranosides were tested. Two ways were selected for generating accessible ketones. 

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