title: Solution forms of an antitumor cyclic hexapeptide, RA-VII in dimethyl sulfoxide-d6 from nuclear magnetic resonance studies.
abstract: Using high-resolution proton nuclear magnetic resonance (1H-NMR) and carbon-13 nuclear magnetic resonance (13C-NMR) experiments, we have assigned three discernible configurational isomers observed in dimethyl sulfoxide-d6 (DMSO-d6) for an antitumor cyclic hexapeptide, RA-VII isolated from Rubia cordifolia. The largest isomer, amounting to 64%, has been assigned as conformer A with only a cis configuration between Tyr-5 and Tyr-6. The second configurational isomer, accounting for 32%, has adopted cis configurations between both Tyr-5 and Tyr-6 and between Ala-2 and Tyr-3. The third isomer, amounting to 4%, was determined to have cis configurations for all of the three N-methyl amide bonds.
authors.affiliation: Department of Pharmacognosy, Tokyo College of Pharmacy, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Itokawa
authors.forename: H
authors.initials: H
authors.lastname: Morita
authors.forename: K
authors.initials: K
authors.lastname: Takeya
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry*; D003903:Deuterium; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D010456:Peptides, Cyclic; D012996:Solutions; D003903:Deuterium; C043548:RA VII; D004121:Dimethyl Sulfoxide