Iduronic acid

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Iduronic acid
IUPAC name (2S,3R,4R,5S)-2,3,4,5- tetrahydroxy-6-oxohexanoic acid
Other names L-Iduronic acid, D-ido-Hexuronic acid, IdoA
CAS number 3402-98-0
PubChem 18845
KEGG C06472
MeSH Iduronic+acid
ChEBI 28481

[H]C(=O)[C@]([H])(O)[C@@]([H])(O) [C@]([H])(O)[C@@]([H])(O)C(O)=O

Molecular formula C6H10O7
Molar mass 194.139 g/mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

L-Iduronic acid (IdoA) is the major uronic acid component of the glycosaminoglycans (GAGs) dermatan sulfate and heparin. It is also present in heparan sulfate although here in a minor amount relative to its carbon-5 epimer glucuronic acid.

IdoA is a hexapyranose sugar. Most hexapyranoses are stable in one of two chair conformations 1C4 or 4C1. L-iduronate is different and adopts more than one solution conformation, with an equilibrium existing between three low energy conformers. These are the 1C4 and 4C1 chair forms and an additional 2</sub>S0 skew-boat conformation.

IdoA may be modified by the addition of a O-sulfate group at carbon position 2 to form 2-O-sulfo-L-iduronic acid (IdoA2S).

When internally positioned within an oligosaccharide the 1C4 and 2S0 conformations (shown below for IdoA2S) predominate.

Proton NMR spectroscopy can be used to track changes in the balance of this equilibrium.[1]


  1. Ferro, D. R. Provasoli, A. (1990). "Conformer populations of L-iduronic acid residues in glycosaminoglycan sequences". Carbohydr. Res. 195: 157–167.