Developments around the bioactive diketopiperazines: a patent review

Introduction: 2,5-Diketopiperazines (DKPs) are cyclic dipeptides from two amino acids with or without further structural modifications in DKP nucleus. These DKPs demonstrated attractive bioactive diversity and potential in drug discovery. Areas covered: This review summarized those bioactive DKPs in patents, and provided the analysis of the structure types (N-substitution, secondary cyclization, isopentenylation, S-substitution, dehydrogenation, and dimerization) and bioactivities including anti-tumor, neuroprotective, immune and metabolic regulatory, oxytocin inhibitory and anti-inflammatory effects, antibiotic activity, PAF inhibition, inhibition of plasminogen activator and T-cell mediated immunity, and insecticidal activity, etc. Expert opinion: Though DKPs did not show very complicated chemical structures, their rigid structure, chiral nature and varied side chains led to their various medicinal applications.