 Glycoside

In its classical oxygen-linked sense, a glycoside is a mixed acetal derived from a cyclic monosaccharide, with the anomeric hydroxy group replaced by an $\mathrm{OR}$ group. The substituent attaches at the anomeric carbon through a glycosidic bond. The partner recovered after removing the sugar residue is commonly called the aglycone.^[ref]

Methyl α-D-glucopyranoside is the nomenclature document's simple example. Comparing it with cyclic glucose, replace the anomeric $\mathrm{OH}$ by $\mathrm{OC}{\mathrm{H}}_3$. As an original atom-counting check, the net addition is $\mathrm{C}{\mathrm{H}}_2$, giving ${\mathrm{C}}_7{\mathrm{H}}_{14}{\mathrm{O}}_6$ from the free glucose formula ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$. This is structural bookkeeping, not a proposed one-step laboratory procedure.

Both the ring form and the anomer belong to the identity: specifying α-D-glucopyranoside conveys more information than merely saying that a molecule contains glucose. The acetal at that centre also differs from the free hemiacetal of the parent sugar.

The attachment atom matters to naming. IUPAC discusses oxygen-, sulfur-, nitrogen- and carbon-linked derivatives separately and discourages some broad biochemical uses of the word glycoside. A structural description should therefore state the actual connection rather than treating every sugar-containing molecule as the same class.^[ref]