glucofuranosa

Glucofuranose is the five-membered ring form (furanose) of the monosaccharide D-glucose. In this form, the sugar cyclizes by reaction of the aldehyde group at carbon 1 with the hydroxyl group on carbon 4, producing a cyclic hemiacetal in which the ring consists of four carbons and one oxygen, a tetrahydrofuran ring. There are two anomeric configurations, alpha-D-glucofuranose and beta-D-glucofuranose, distinguished by the orientation of the substituent at the anomeric carbon.

Occurrence and distribution: In aqueous solution, glucopyranose, the six-membered ring form, is the dominant form of glucose. Glucofuranose constitutes only a small fraction of the equilibrium mixture, and its proportion is influenced by temperature, pH, solvent, and sample history. The open-chain form of glucose can interconvert with both ring sizes through ring-opening and re-closure.

Interconversion and chemistry: The ring forms interconvert with the open-chain aldehyde form, allowing transition between five- and six-membered rings. Within a given ring size, mutarotation describes the interconversion between alpha- and beta-anomers. Ring-size changes involve additional opening and re-closing steps.

Significance: Glucofuranose is mainly of interest in carbohydrate chemistry as a reference point for conformational analysis and synthetic studies. It can appear in certain glycosidic derivatives and specialized oligosaccharides or protected glucose systems studied in the laboratory, but it is not a major component of natural polysaccharides. See also glucopyranose, furanose, and mutarotation.