A Sugar acid or acidic sugar is a monosaccharide with a carboxyl group at one end or both ends of its chain.^[1]

Main classes of sugar acids include:

• Aldonic acids, in which the aldehyde group (−CHO) located at the initial end (position 1) of an aldose is oxidized.
• Ulosonic acids, in which the −CH₂(OH) group at the initial end of a 2-ketose is oxidized creating an α-ketoacid.
• Uronic acids, in which the −CH₂(OH) group at the terminal end of an aldose or ketose is oxidized.
• Aldaric acids, in which both ends (−CHO and −CH₂(OH)) of an aldose are oxidized.

Aldonic acid

An ulosonic acid; specifically, 3-Deoxy-D-manno-oct-2-ulosonic acid

Uronic acid

Aldaric acid

Examples

Examples of sugar acids include:

• Aldonic acids
  • Glyceric acid (3C)
  • Xylonic acid (5C)
  • Gluconic acid (6C)
  • Ascorbic acid^[2] (6C, unsaturated lactone)
• Ulosonic acids
  • Neuraminic acid (5-amino-3,5-dideoxy-D-glycero-D-galacto-non-2-ulosonic acid)
  • Ketodeoxyoctulosonic acid (KDO or 3-deoxy-D-manno-oct-2-ulosonic acid)
• Uronic acids
  • Glucuronic acid (6C)
  • Galacturonic acid (6C)
  • Iduronic acid (6C)
• Aldaric acids
  • Tartaric acid (4C)
  • meso-Galactaric acid (Mucic acid) (6C)
  • D-Glucaric acid (Saccharic acid) (6C)

Ascorbic acid (Vitamin C)

The β-D form of glucuronic acid