Homoserine is a more reactive variant of the amino acid serine. In this variant the hydroxyl side chain contains an additional CH2 group which brings the hydroxyl group closer to its own carboxyl group allowing it to chemically react to form a five-membered ring.

Trans-Aconitic acid is normally present in normal human urine and it has been suggested that is present in larger amounts with Reye's syndrome and organic aciduria. trans-Aconitic acid is a substrate of enzyme trans-aconitate 2-methyltransferase (EC 2.1.1.144).

Diethyl oxalpropionate also known as methyloxalacetic acid diethyl ester or diethyl methyloxalacetate is a member of the class of compounds known as beta-keto acids and derivatives. These compounds are organic compounds containing an aldehyde substituted with a keto group on the C3 carbon atom.