furanoside

A furanoside is a cyclic hemiacetal or hemiketal derived from a furanose sugar. Furanoses are five-membered rings containing four carbon atoms and one oxygen atom. This ring structure is formed when the hydroxyl group on the aldehyde or ketone carbon of a monosaccharide reacts with a hydroxyl group on a carbon atom further down the chain, typically the fifth carbon in an aldopentose or aldohexose. The resulting cyclic structure has an anomeric carbon, which is the original carbonyl carbon, and can exist in two forms, alpha (α) and beta (β), depending on the spatial orientation of the hydroxyl group at this anomeric carbon. Furanosides are important structural components of many biologically significant molecules, including nucleotides (such as those found in RNA) and certain glycosides. The furanose ring is generally more strained than the corresponding pyranose ring, which is a six-membered ring. The specific spatial arrangement of substituents around the furanose ring influences the chemical and biological properties of the molecule.