Diketopiperazine

The Diketopiperazines (DKP) are a class of cyclic organic compounds that result from peptide bonds between two amino acids. They are combinations of ketones and the compound piperazine. A diketopiperazine was the first peptide to have its complete, three-dimensional structure figured out, in work undertaken at Caltech by Robert Corey in the 1930s. Corey studied the cyclic anhydride of the dipeptide glycylglycine.

Some diketopiperazines are considered carcinogenic.