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A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. Several species of Heliconius butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.
In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group -COCl. Their formula is usually written RCOCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.
An acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.
Dolichol refers to any of a group of long-chain mostly unsaturated organic compounds that are made up of varying numbers of isoprene units terminating in an α-saturated isoprenoid group, containing an alcohol functional group.
Glycal is a name for cyclic enol ether derivatives of sugars having a double bond between carbon atoms 1 and 2 of the ring. The term “glycal” should not be used for an unsaturated sugar that has a double bond in any position other than between carbon atoms 1 and 2.
An Endoglycosidase is an enzyme that releases oligosaccharides from glycoproteins or glycolipids. It may also cleave polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated protein and lipid molecules is more common.
Glycosyltransferases are enzymes that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur-based.
The Koenigs–Knorr reaction in organic chemistry is the substitution reaction of a glycosyl halide with an alcohol to give a glycoside. It is one of the oldest glycosylation reactions. It is named after Wilhelm Koenigs (1851–1906), a student of von Bayer and fellow student with Hermann Emil Fischer, and Edward Knorr, a student of Koenigs.
Fischer glycosidation refers to the formation of a glycoside by the reaction of an aldose or ketose with an alcohol in the presence of an acid catalyst. The reaction is named after the German chemist, Emil Fischer, winner of the Nobel Prize in chemistry, 1902, who developed this method between 1893 and 1895.
Carbohydrate chemistry is a subdiscipline of chemistry primarily concerned with the synthesis, structure, and function of carbohydrates. Due to the general structure of carbohydrates, their synthesis is often preoccupied with the selective formation of glycosidic linkages and the selective reaction of hydroxyl groups; as a result, it relies heavily on the use of protecting groups.
Nucleotide sugars are the activated forms of monosaccharides. Nucleotide sugars act as glycosyl donors in glycosylation reactions. Those reactions are catalyzed by a group of enzymes called glycosyltransferases.
A chemical glycosylation reaction involves the coupling of a glycosyl donor, to a glycosyl acceptor forming a glycoside. If both the donor and acceptor are sugars, then the product is an oligosaccharide. The reaction requires activation with a suitable activating reagent. The reactions often result in a mixture of products due to the creation of a new stereogenic centre at the anomeric position of the glycosyl donor. The formation of a glycosidic linkage allows for the synthesis of complex polysaccharides which may play important roles in biological processes and pathogenesis and therefore having synthetic analogs of these molecules allows for further studies with respect to their biological importance.
Intramolecular aglycon delivery is a synthetic strategy for the construction of glycans. This approach is generally used for the formation of difficult glycosidic linkages.
The armed/disarmed approach to glycosylation is an effective way to prevent sugar molecules from self-glycosylation when synthesizing disaccharides. This approach was first recognized when acetylated sugars only acted as glycosyl acceptors when reacted with benzylated sugars. The acetylated sugars were termed “disarmed” while the benzylated sugars were termed “armed”.
The Crich β-mannosylation in organic chemistry is a synthetic strategy which is used in carbohydrate synthesis to generate a 1,2-cis-glycosidic bond. This type of linkate is generally very difficult to make, and specific methods like the Crich β-mannosylation are used to overcome these issues.
A glycosyl donor is a carbohydrate mono- or oligosaccharide that will react with a suitable glycosyl acceptor to form a new glycosidic bond. By convention, the donor is the member of this pair that contains the resulting anomeric carbon of the new glycosidic bond. The resulting reaction is referred to as a glycosylation or chemical glycosylation.
A glycosyl acceptor is any suitable nucleophile-containing molecule that will react with a glycosyl donor to form a new glycosidic bond. By convention, the acceptor is the member of this pair which did not contain the resulting anomeric carbon of the new glycosidic bond. Since the nucleophilic atom of the acceptor is typically an oxygen atom, this can be remembered using the mnemonic of the acceptor is the alcohol. A glycosyl acceptor can be a mono- or oligosaccharide that contains an available nucleophile, such as an unprotected hydroxyl.
Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. This can include the synthesis of monosaccharide residues or structures containing more than one monosaccharide, known as oligosaccharides.
Glypiation is the addition by covalent bonding of a glycosylphosphatidylinositol (GPI) anchor and is a common post-translational modification that localizes proteins to cell membranes. This special kind of glycosylation is widely detected on surface glycoproteins in eukaryotes and some Archaea.