nglycosides

N-glycosides are glycosides in which the glycosidic bond connects the anomeric carbon of a sugar to a nitrogen atom of the aglycone. This contrasts with O-glycosides, where the linkage is to an oxygen atom, and with C-glycosides, where the sugar carbon bonds directly to the aglycone.

In biology, the best-known N-glycosides are nucleosides. Here, ribose or deoxyribose is linked to a nucleobase through an N-glycosidic bond. In purines, the sugar attaches at the N9 position; in pyrimidines, the attachment is at N1. The typical configuration for the sugar in nucleosides is beta. N-glycosides are essential building blocks of RNA and DNA, and they serve as substrates and regulators in various metabolic pathways.

N-glycosides also occur beyond nucleosides, including natural products and medicinal compounds where a sugar is bonded to a nitrogen atom of an amine or heterocycle. Examples include certain alkaloid glycosides and nucleoside analog drugs, which exploit the N-glycosidic linkage to mimic natural nucleosides in biological systems.

Chemical properties and reactivity: the N-glycosidic bond can be hydrolyzed to yield the sugar and the nitrogen-containing aglycone. Enzymes called nucleosidases catalyze such hydrolysis in biological contexts, while acid hydrolysis also cleaves the bond. This bond is central to the metabolism and pharmacology of nucleosides and nucleoside-like therapeutics, whose activity often depends on subsequent phosphorylation to their triphosphate forms.

See also: glycosides, nucleosides, glycosyltransferases.