Threitol

Threitol is the chiral four-carbon sugar alcohol with the molecular formula C4H10O4. It is primarily used as an intermediate in the chemical synthesis of other compounds. It exists in the enantiomorphic forms D-threitol and L-threitol, the reduced forms of D- and L-threose. It is the diastereomer of erythritol, which is used as a sugar substitute.

In living organisms, threitol is found in the edible fungus Armillaria mellea. It serves as a cryoprotectant (antifreeze agent) in the Alaskan beetle Upis ceramboides.