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
1C
4 or
4C
1. L-iduronate is different and adopts more than one solution conformation, with an equilibrium existing between three low-energy conformers. These are the
1C
4 and
4C
1 chair forms and an additional
2S
0 skew-boat
conformation.