l-Iduronic acid (IUPAC abbr.: 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.

l-Iduronic acid

α-l-idopyranuronic acid
Names
IUPAC name l-idopyranuronic acid
Other names l-Iduronic acid, d-ido-Hexuronic acid, IdoA
Identifiers
CAS Number	3402-98-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28481 N
ChemSpider	10051462 Y
KEGG	C06472 N
MeSH	Iduronic+acid
PubChem CID	11877134
UNII	F5HD8XQ3DP Y
InChI InChI=1S/C6H10O7/c7-1-2(8)4(5(10)11)13-6(12)3(1)9/h1-4,6-9,12H,(H,10,11)/p-1/t1-,2-,3+,4+,6+/m0/s1 Y Key: AEMOLEFTQBMNLQ-VCSGLWQLSA-M Y InChI=1/C6H10O7/c7-1-2(8)4(5(10)11)13-6(12)3(1)9/h1-4,6-9,12H,(H,10,11)/p-1/t1-,2-,3+,4+,6+/m0/s1 Key: AEMOLEFTQBMNLQ-QQSWGHAIBB
SMILES [O-]C(=O)[C@@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O
Properties
Chemical formula	C6H10O7
Molar mass	194.139 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

IdoA is a pyranose sugar. Most pyranoses 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 ²S₀ skew-boat conformation.^{[citation needed]}

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

In 2000, LK Hallak described the importance of this sugar in respiratory syncytial virus (RSV) infection. Dermatan sulfate and heparan sulfate were the only GAGs containing IdoA, and they were the only ones that inhibited RSV infection in cell culture.^[1]

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.^[2]

• 
  IdoA(2S)¹C₄ conformation
• 
  IdoA(2S)²S₀ conformation