Introduction:
Cellular glycoconjugates play an important role in biological recognition processes including cell-to-cell and cell-to-pathogen interactions and many others. Understanding the 3D structure of natural glycoconjugates is important for the assessment of molecular mechanisms of these processes. Monosaccharide units, being basic constituting blocks of longer carbohydrate chains, thus define their conformation and spatial shape which may, in turn, have crucial influence on their biological functions. Hence the great interest to the conformational analysis of carbohydrates that has been constantly evolving during the previous decades. Originally, the primary goal of such analysis was to clarify conformational behavior of the joint fragment between two monosaccharide rings – the glycosidic linkage. Within this approach, the conformation of the most commonly met six-membered monosaccharide rings (hexapyranosides) was assumed to be a rigid chair or sometimes a completely inverted rigid chair. For their five-membered ring isomers (hexafuranosides), a range of conformers was regarded as available. This communication presents a review of our own data obtained in course of investigation of pyranoside and furanoside conformations by means of modern quantum chemistry methods. Particularly, it is shown that hexapyranosides are not always as rigid as they have been generally thought to be: our studies demonstrate drastic conformational changes occurring in pyranosides bearing a large number of charged substituents, though the previously suggested complete inversion never seems to take place¹. For furanosides, it is shown that significant attention must be paid to the choice of a particular computational method for the correct prediction of their conformational preferences².

Conflicts of Interest:
The authors declare that they have no conflict of interest in the publication of this article. The authors have no conflicts of interest to report in this work. Abstract was not submitted elsewhere and published here firstly

Funding:
The study was funded by the Russian Scientific Foundation (grant No. 19-73-30017-P).