Isolation, Structure Determination, and Synthesis of Allo-RA-V and Neo-RA-V, RA-Series Bicyclic Peptides from Rubia cordifolia L.

✍ Scribed by Dr. Yukio Hitotsuyanagi; Masumi Odagiri; Saori Kato; Jun-ichi Kusano; Tomoyo Hasuda; Haruhiko Fukaya; Prof. Dr. Koichi Takeya

• Book ID: 101839195
• Publisher: John Wiley and Sons
• Year: 2012
• Tongue: English
• Weight: 466 KB
• Volume: 18
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.201103185

✦ Synopsis

Abstract

Two bicyclic hexapeptides, allo‐RA‐V (4) and neo‐RA‐V (5), and one cyclic hexapeptide, __O‐__seco‐RA‐V (6), were isolated from the roots of Rubia cordifolia 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 of compound 6 by chemical correlation with deoxybouvardin (3). Comparison of the 3D structures of highly active RA‐VII (1) with less‐active compounds 4 and 5 suggests that the orientation of the Tyr‐5 and/or Tyr‐6 phenyl rings plays a significant role in their biological activity. The isolation of peptides 4–6, along with compound 3, and the comparison of their structures seem to indicate that peptide 6 may be the common precursor to bicyclic peptides 3–5 in the plant.