What does furanose mean?
A furanose is a five-membered ring form of a simple sugar, created when a monosaccharide folds back on itself so that a hydroxyl group attacks the carbonyl carbon, forming a closed loop containing four carbons and one oxygen atom. The name derives not from any actual furan content but from the resemblance of this ring to the five-membered compound furan. Many sugars — including fructose, ribose, and deoxyribose — readily adopt furanose forms, and these rings are central to biochemistry: the ribofuranose and deoxyribofuranose sugars form the backbone of RNA and DNA respectively. In solution, furanose and six-membered pyranose forms interconvert, so a sugar sample is typically an equilibrium mixture of both. The term belongs to carbohydrate chemistry and biochemistry, where it is usually used as part of a compound name such as 'fructofuranose'. Its counterpart, the six-membered pyranose, is generally more stable and often predominates for hexoses like glucose.
nounA five-membered cyclic form of a sugar (monosaccharide) produced when the molecule reacts intramolecularly to form a ring resembling furan in shape; contrasted with the six-membered pyranose form.
- A five-membered ring form of a monosaccharide formed by intramolecular hemiacetal or hemiketal formation.
"In aqueous solution, fructose exists as an equilibrium mixture of furanose and pyranose forms."
"Glucose can adopt either a pyranose or a furanose conformation in solution."
"Fructose-2,6-bisphosphate contains a fructofuranose ring at its core."
Standard English plural; typically pluralized only in technical discussion of multiple ring forms.
"Both furanoses equilibrate slowly with their open-chain forms."
The name 'furanose' doesn't mean sugar contains furan — chemists just noticed its five-membered ring looks like one and borrowed the name.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of furanose
The word combines 'furan', the name of the five-membered oxygen heterocycle derived from Latin 'furfur' (bran), with the suffix '-ose' used for sugars. It arose in late nineteenth-century organic chemistry, when Emil Fischer and contemporaries were working out the ring structures of sugars and adopted the furan analogy to describe the five-membered ring form. Related terms include 'furfural' (a furan aldehyde from bran husks) and 'furanoside', a glycoside whose sugar portion takes the furanose ring.
Related word forms
How furanose is actually used
Strictly a term of carbohydrate chemistry and biochemistry; rarely encountered outside scientific writing. In speech it is usually prefixed by the sugar's name (e.g., 'fructofuranose', 'ribofuranose').
Easily confused with furanose
A pyranose is the corresponding six-membered sugar ring, whereas a furanose is the five-membered ring form.
Furan is the aromatic oxygen-containing heterocycle after which the furanose ring is named, but it is not itself a sugar.