Dglucopyranose

D-glucopyranose is the six-membered ring form (pyranose) of the monosaccharide D-glucose. It arises when the aldehyde group at C1 reacts intramolecularly with the hydroxyl at C5, producing a cyclic hemiacetal and a six-membered ring that contains one oxygen atom. In solution, D-glucopyranose exists mainly as two anomers, alpha and beta, which differ at the anomeric carbon (C1) in the orientation of the hydroxyl group.

The D designation refers to the configuration at the chiral center farthest from the carbonyl group and is preserved in the cyclic forms. The molecular formula is C6H12O6. In Haworth representation, alpha-D-glucopyranose has the anomeric hydroxyl below the ring plane, while beta-D-glucopyranose has it above. In aqueous solution, the alpha and beta forms interconvert through mutarotation, and the equilibrium favors the beta form under many conditions (though exact ratios depend on temperature and solvent).

D-glucopyranose is a fundamental building block of carbohydrates. It forms glycosidic bonds in polysaccharides such as starch and glycogen when in the alpha-pyranose form, and in cellulose when linked as beta-D-glucopyranose units. It also serves as a key metabolic substrate, circulating in the bloodstream as glucose and being transported by glucose transporters. Minor amounts of the furanose ring can occur, but the pyranose form dominates under physiological conditions.