Glycosides structure, determination

Tamus communis (6) and Asparagus cochinchinensis (7) and flavonol glycosides from Mercurialis annua. (14). However the entire process consumes glycosides which are often very difficult to separate and purify and may be better employed in biological evaluation experiments. So the more recent approach to glycoside structural determination is a combination of ID and 2D NMR techniques which are very sensitive and non-destructive. The non-invasive nature of NMR methods allows easy recovery of the intact material by simple removal of solvent for successive biological evaluations. 

The use of penodic acid oxidation m structure determination can be illustrated by a case m which a previously unknown methyl glycoside was obtained by the reaction of D arabmose with methanol and hydrogen chlonde The size of the nng was identified as five membered because only one mole of penodic acid was consumed per mole of glycoside and no formic acid was produced Were fhe nng six membered fwo moles of penodic acid would be required per mole of glycoside and one mole of formic acid would be produced... 

Figure 4.21 An illustration of how the configuration of glycosidic bonds determine polysaccharide structure and function. The P-1-4 linkages in cellulose favourize straight chains, optimal for structural purposes, whereas the a-1-4 linkages are favourable to bent structures, better adapted to storage in a hydrated form.

The interaction between Drosophila, yeasts and columnar cacti of the Sonoran Desert has been the subject of much recent interest (37) As a coevolved system, perhaps more is known about this interaction than any other. The chemistry of the cacti (70 spp.) has been postulated to play a significant role in the establishment of this system (38 ), but this was based upon reports of a relatively small number of relatively simple alkaloids, and a small number of terpenoid compounds. Only recently, the diversification of plant compounds has been discovered to be much greater (5). In their section on alkaloids in the above work, BajaJ and McLaughlin report the presence of some thirty-five structures. In addition, I have been able to isolate some sixty triterpenoid glycosides (structures were not determined) and more were detected but not Isolated. 

Kodama, H., T. Fujimori, and K. Kato. Structure determination of new sesquiterpene glycosides from flue-cured tobacco by two dimensional NMR. Proc 26th Symposium on the Chemistry of Natural Products, Kyoto, Japan 1983 26 1-8. 

Si, J.Y. et al.. Isolation and structure determination of flavonol glycosides from the fresh fruits of... 

Pathirana, C., Tapiolas, D.M., Jensen, P.R., Dwight, R., and Fenical, W., Structure determination of maduralide a new 24-membered ring macrolide glycoside produced by a marine bacterium (Actino-... 

To avoid the above mentioned problems which are due to side activities of commercial glycosidase preparations and the specificity of glycosidases for both, the glycon as well as the aglycon moiety, an isolation and structural determination of individual constituents in a precursor fraction should be attempted. This requires the availability of preparative separation techniques that enable a gentle isolation of reactive aroma precursors from the complex glycosidic fraction of wine. 

Figure 11.14. Glycosidic Bonds Determine Polysaccharide Structure. The P-1,4 linkages favor straight chains, which are optimal for structural purposes. The a-1,4 linkages favor bent structures, which are more suitable for storage.

The satire approach was used for the structural determination of five oleanolic acid glycosides from Calendula arvensis 32-36 (23) and 3p, 2ip, 23 trihydroxy-olean-12-en-28-oic acid bisglycoside 44... 

R76 N. P. Sahu and B. Achari, Advances in Structural Determination of Saponins and Terpenoid Glycosides , p. 315 R77 M. Liu and J. C. Lindon, Recent Advances in Editing and Selective Detection Methods for NMR Spectroscopy , p. 351... 

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