New antitumor bicyclic hexapeptides, RA-VI and -VIII from Rubia cordifolia; Conformation-activity relationship II

Article abstract of DOI:10.1016/S0040-4020(01)96155-1

The structures of new antitumor bicyclic hexapeptides, RA-VI and -VIII from Rubia cordifolia were elucidated by the spectroscopic and chemical methods. A combination of two-dimentional NMR techniques and NOE relationships showed that the amino acids const