Uronic acid

A uronic acid is a monosaccharide derivative in which the terminal primary alcohol group opposite the potential aldehyde group has become a carboxyl group. The reference numbering of the original aldose is retained: carbon 1 remains the potential aldehyde carbon, rather than becoming the number assigned to the new carboxyl group.^[ref]

For glucose, the relevant terminal group is at carbon 6. Replacing its $\mathrm{C}{\mathrm{H}}_2\mathrm{OH}$ reference group by $\mathrm{COOH}$ gives glucuronic acid, while preserving the arrangement at the intervening stereocenters. This distinguishes the position of a modification from the mere presence of a carboxyl group. Glucuronic acid supplies one of the two alternating sugar residues in hyaluronic acid, connecting the chemical classification with a biological polysaccharide.