New antitumor bicyclic hexapeptides, RA-XI, -XII, -XIII and -XIV from Rubia cordifolia.

New antitumor bicyclic hexapeptides, RA-XI, -XII, -XIII and -XIV from Rubia cordifolia. Two antitumour bicyclic hexapeptides from Rubia cordifolia Structures of cytotoxic bicyclic hexapeptides, RA-XIX, -XX, -XXI, and -XXII, from Rubia cordifolia L. New Cytotoxic Bicyclic Hexapeptides, RA-XXIII and RA-XXIV, from Rubia cordifolia L. A novel bicyclic hexapeptide, RA-XVIII, from Rubia cordifolia: Structure, semi-synthesis, and cytotoxicity A novel bicyclic hexapeptide, RA-XVIII, from Rubia cordifolia: Structure, semi-synthesis, and cytotoxicity Studies on antitumor cyclic hexapeptides RA obtained from Rubiae Radix, Rubiaceae. VI Minor antitumor constituents. Isolation, structural elucidation, and synthesis of RA-XVII, a novel bicyclic hexapeptide from Rubia cordifolia, and the effect of side chain at residue 1 upon the conformation and cytotoxic activity Isolation and antitumor activity of cyclic hexapeptides isolated from Rubiae radix. RA-dimer A, a novel dimeric antitumor bicyclic hexapeptide from Rubia cordifolia L.