The idose is one of the monosaccharide classified into aldohexose.

It is an epimer in 5th place of the glucose.

The idose hardly exists in the natural world.

But the iduronic acid that is uronic acids of the idose is contained in the skin and blood, and composes the heparan sulphate and the dermatan sulphate.

The isomerization is caused in solution, and it becomes a compound with the ring-shaped structure (mutarotation).

It is α-pyranose form that the existence ratio is the highest when the idose reaches the condition of equilibrium.