Dfructofuranose

D-fructofuranose is the five-membered ring form (furanose) of the monosaccharide D-fructose, a ketohexose. It arises from intramolecular cyclization of the ketone at carbon 2 with the hydroxyl group on carbon 5, forming a hemiketal that closes to a cyclic ether. The resulting ring contains four carbon atoms and one oxygen, with the anomeric carbon located at C2.

In aqueous solution, D-fructofuranose exists mainly as two anomers, alpha and beta, which interconvert through mutarotation. The furanose form is a common cyclic form of fructose, though a smaller fraction of the pyranose (six-membered) form can also be present. The beta anomer of the furanose form is typically a major constituent among the furanose isomers in many contexts.

D-fructofuranose is a key structural motif in several carbohydrates, most notably as the fructose moiety of sucrose, where it is linked as beta-D-fructofuranose. In metabolism, fructose is phosphorylated by fructokinase to fructose-1-phosphate and then enters glycolysis after further metabolism. The furanose form influences the way fructose is recognized by enzymes and transporters, and thus affects both its biochemical reactivity and nutritional properties.

---