Cyclo(Asp-Gly) is a cyclic dipeptide (diketopiperazine, DKP) composed of aspartic acid and glycine. It is a specific structural isomer of the cyclic dipeptide family, characterized by its diketopiperazine ring formed by the condensation of the amino and carboxyl groups of the two amino acids. This compound is primarily of interest in pharmaceutical research and quality control. It is known to be a potential degradation product or impurity of certain peptide-based drugs and bioactive peptides. As such, it is often used as a reference standard or impurity standard in analytical chemistry for method development, validation, and quality assessment of pharmaceutical products to ensure their safety and efficacy. The diketopiperazine structure is also found in various natural products and can exhibit biological activities, though for Cyclo(Asp-Gly), its primary defined application remains within the realm of pharmaceutical analysis as a well-characterized chemical entity for comparative studies.