Glucopyranosis

Glucopyranose is the ring form of glucose that is formed by intramolecular hemiacetal formation. In the pyranose form, the first is connected to the fifth carbon atom via an oxygen bridge, in the rarer furanose form, the first is connected to the fourth carbon atom via an oxygen bridge. The carbonyl oxygen of the aldehyde group thereby becomes the hydroxy group.

Pyranoses are all lactols of monosaccharides which contain a six-membered ring of five carbon and one oxygen atom and a hydroxy group on one of the carbon atoms which bind the ring-forming oxygen.