Iduronic acid

Iduronic acid
	File:IduronicAcid-chair.png
	File:IduronicAcid.png
Names
	IUPAC name (2S,3R,4R,5S)-2,3,4,5- tetrahydroxy-6-oxohexanoic acid
	Other names L-Iduronic acid, D-ido-Hexuronic acid, IdoA
Identifiers
CAS Number	3402-98-0;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:28481;
KEGG	C06472;
MeSH	Iduronic+acid
PubChem CID	18845;
	SMILES C(=O)C(C(C(C(C(=O)O)O)O)O)O or [H]C(=O)[C@]([H])(O)[C@@]([H])(O) [C@]([H])(O)[C@@]([H])(O)C(O)=O;
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). Infobox 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 ^{2S₀ 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]

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

References

^ Ferro, D. R. Provasoli, A. (1990). "Conformer populations of L-iduronic acid residues in glycosaminoglycan sequences". Carbohydr. Res. 195: 157–167. doi:10.1016/0008-6215(90)84164-P. PMID 2331699.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[1] Ferro, D. R. Provasoli, A. (1990). "Conformer populations of L-iduronic acid residues in glycosaminoglycan sequences". Carbohydr. Res. 195: 157–167. doi:10.1016/0008-6215(90)84164-P. PMID 2331699.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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