erythrose

Erythrose is an aldotetrose, a four-carbon aldose sugar with the molecular formula C4H8O4. It exists in two enantiomeric forms, D-erythrose and L-erythrose, and as diastereomers classified as erythrose and threose based on the configuration at the two stereocenters (carbons 2 and 3). Each diastereomer has a pair of enantiomers (D- and L-).

In Fischer projection, the erythrose diastereomer is defined by the two stereocenters having the same configuration, which corresponds to the same side of the Fischer diagram for the C2 and C3 hydroxyl groups. D-erythrose and L-erythrose are mirror images of each other. Threose, the other tetrose diastereomer, has the hydroxyl groups on opposite sides in the Fischer projection.

Erythrose exists in linear form in solution but also forms cyclic hemiacetals. The cyclic forms are typically five-membered rings, called furanose forms, and they can appear as alpha or beta anomers depending on the stereochemistry at the anomeric carbon. Like other small sugars, erythrose is highly soluble in water and engages in the same general aldose chemistry characteristic of tetroses.

Biosynthetically, the phosphorylated derivative erythrose-4-phosphate is an important intermediate in the shikimate pathway, which is used by bacteria, fungi, and plants to synthesize aromatic compounds and amino acids. The unphosphorylated sugar eryhthrose occurs as a metabolic intermediate in various contexts and serves as a reference compound in carbohydrate chemistry and stereochemical studies.

Erythrose is mainly discussed in the context of carbohydrate chemistry and metabolism, serving as a fundamental example of a four-carbon aldose and a basis for understanding diastereomerism and ring formation in tetroses.