A diketopiperazine (DKP), also known as a dioxopiperazine or piperazinedione, is a class of organic molecules in which the two nitrogen atoms of a piperazine 6-membered ring are part of amide linkages. There are three regioisomers possible, differing in the locations of the two carbonyl groups around the ring. While these isomers share a piperazine core, optimal strategies for their synthesis differ. The 2,3-diketopiperazines may be viewed as the oxamide obtained from ethylenediamine. 2,5-diketopiperazines are cyclodipeptides obtained via condensation of two α-amino acids. 2,6-diketopiperazines may be viewed as cyclised imide derivatives derived from Iminodiacetic acids.
As a result of the structural similarities of DKPs to peptides,. their appearance in biologically active natural products has inspired medicinal chemists to use DKPs to circumvent the poor physical and metabolic properties of peptides in the course of drug discovery.
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