<Tr> <Td> </Td> <Td> </Td> </Tr> <P> 2, 5 - Diketopiperazine, also known as piperazine - 2, 5 - dione and as the cyclodipeptide cyclo (Gly - Gly), is an organic compound and the smallest cyclic dipeptide that consists of a six - membered ring containing two amide linkages where the two nitrogen atoms and the two carbonyls are at opposite positions in the ring . It was first synthesized by Curtius and Gloebel in 1888 and was the first compound containing a peptide bond to be studied by X-ray crystallography in 1938 . It occurs in cocoa and bread and has a metallic and bitter taste . </P> <P> 2, 5 - Diketopiperazines (2, 5 - DKPs) which include mono - and disubstituted 2, 5 - diketopiperazines, their annulated, spiro - annulated and bridged derivatives are amongst the most ubiquitous peptide derivatives found in nature . They are found in fermentation broths and yeast cultures and this subunit is often found alone or embedded in larger more complex architectures in a variety of natural products isolated from fungi, bacteria, plants, and mammals, and their core structure occurs in several drugs . In addition, they are often produced as degradation products of polypeptides, especially in processed food and beverages, and have been identified in the contents of comets . </P> <P> There is a widespread occurrence of the 2, 5 - diketopiperazine core in biologically active natural products . The most structurally diverse 2, 5 - diketopiperazine natural products are based on tryptophan and proline modified by heterocyclisation and isoprenyl addition . These range from the hepatoxic brevianamide F (cyclo (L - Trp - L - Pro)) to the annulated tremorogenic verruculogen and the spiro - annulated spirotryprostatin B which represent a promising class of antimitotic arrest agents, to the structurally complex (+) - stephacidin A, a bridged 2, 5 - diketopiperazine that possess a unique bicyclo (2.2. 2) diazaoctane core ring system and is active against the human colon HCT - 116 cell line . </P>

Microwave assisted synthesis of piperazine 2 5 dione