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The reaction often favors formation of the α-glycosidic bond as shown due to the anomeric effect. A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside.
The formation of a glycosidic linkage results in the formation of a new stereogenic centre and therefore a mixture of products may be expected to result. The linkage formed may either be axial or equatorial (α or β with respect to glucose). To better understand this, the mechanism of a glycosylation reaction must be considered.
Glycosylation also plays a role in cell-to-cell adhesion (a mechanism employed by cells of the immune system) via sugar-binding proteins called lectins, which recognize specific carbohydrate moieties. [2] Glycosylation is an important parameter in the optimization of many glycoprotein-based drugs such as monoclonal antibodies. [6]
Moreover, the mechanism of glycosidic bond forming reaction (3→2) was examined thoroughly by the determination of kinetic isotopic effects (KIEs) and NMR spectroscopy. Consequently, the magnitude of KIEs indicated that the displacement of the triflate from 3 proceeded with the development of significant oxacarbenium ion character at the ...
The glycosidic bond is formed from a glycosyl donor and a glycosyl acceptor. There are four types of glycosidic linkages: 1, 2-trans-α, 1, 2-trans-beta, 1, 2-cis-α, and 1, 2-cis-beta linkages. 1, 2-trans glycosidic linkages can be easily achieved by using 2-O-acylated glycosyl donors (neighboring group participation).
In formal terms, a glycoside is any molecule in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. Glycosides can be linked by an O- (an O-glycoside ), N- (a glycosylamine ), S-(a thioglycoside ), or C- (a C-glycoside ) glycosidic bond.
Glycosynthase are derived from glycosidase enzymes, which catalyze the hydrolysis of glycosidic bonds. [2] They were traditionally formed from retaining glycosidase by mutating the active site nucleophilic amino acid (usually an aspartate or glutamate ) to a small non-nucleophilic amino acid (usually alanine or glycine ).
O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine (Ser) or threonine (Thr) residues in a protein. O-glycosylation is a post-translational modification that occurs after the protein has been synthesised.