RA-dimer B, a New Dimeric RA-series Cyclopeptide Incorporating Two Different Types of Cycloisodityrosine Units, from<i>Rubia cordifolia</i> L.
作者:Yukio Hitotsuyanagi、Takayuki Tsuchiya、Masako Ohata、Ayaka Yoshida、Haruhiko Fukaya、Hyun Sun Park、Koichi Takeya、Nobuo Kawahara
DOI:10.1002/asia.201601138
日期:2016.12.6
RA‐dimer B, a new cytotoxic RA‐series peptide, was isolated from the roots of Rubiacordifolia L. Its structure was elucidated on the basis of spectroscopic analysis to be a dimeric cyclopeptide composed of deoxybouvardin and allo‐RA‐V. Those two cyclopeptide units are connected by an ether linkage between the phenolic oxygen atom of deoxybouvardin and the ϵa carbon atom of Tyr‐6 of allo‐RA‐V. RA‐dimer B
Twobicyclichexapeptides, allo‐RA‐V (4) and neo‐RA‐V (5), and one cyclic hexapeptide, O‐seco‐RA‐V (6), were isolated from the roots of Rubiacordifolia L. Their gross structures were elucidated on the basis of spectroscopic analysis and X‐ray crystallography of compound 5. The absolute stereochemistry of compounds 4 and 5 were established by their total syntheses, and the absolute stereochemistry