Furanose

As furanoses refers lactols containing a five-membered ring of four carbon and one oxygen atom, as well as at one of the oxygen bridge the adjacent carbon atom is a hydroxy group. The ring is formed in certain monosaccharides by intramolecular hemiacetal between the carbonyl group and a hydroxyl group with the formation of a five-membered ring with an oxygen atom and four carbon atoms as ring members. All monosaccharides having at least four carbon atoms is an equilibrium in aqueous solution from open-chain and cyclic form, wherein the annular shape is stable. These rings of five atoms are called furanose, rings with six atoms as pyranoses. Higher molecular weight carbohydrates ( di-, oligo-and polysaccharides) are made up of circular monomers.

The name is derived from the heterocyclic furan molecule, but in the ring system containing two double bonds, so - unlike the furanoses - is an aromatic.

Nomenclature of furanoses

The atoms of the five-membered ring ( tetrahydrofuran ) are numbered in such a way that the anomeric carbon atom (original carbon atom of the carbonyl group of the aldose or ketose ) 1 is always assigned the position. The position of the hydroxyl groups is then obtained from the locants of the carbon atom to which it is bound in the acyclic form. Other conventions are described in the scientific literature.