Progress in the study of some important natural bioactive cyclopeptides

Natural cyclopeptides are hot spots in chemical and pharmaceutical fields because of the wide spreading bio-resources, complex molecular structures and various bioactivities.  Bio-producers of cyclopeptides distribute over almost every kingdom from bacteria to plants and animals.  Many cyclopeptides contain non-coded amino acids and non-pepditic bonds.  Most exciting characteristic of cyclopeptides is a range of interesting bioactivities such as antibiotics gramicidin-S (2), vancomycin (3) and daptomycin (4), immunosuppressive cyclosporin-A (1) and astin-C (8), and anti-tumor aplidine (5), RA-V (6) and RA-VII (7).  Compounds 1−4 are being used in clinics; compounds 5-8 are in the stages of clinical trial or as a candidate for drug research.  In this review, the progress in chemical and bioactive studies on these important natural bioactive cyclopeptides 1−8 are introduced, mainly including discovery, bioactivity, mechanism, QSAR and synthesis.