Isolation,Structure Determination,and Synthesis of Allo‐RA‐V and Neo‐RA‐V,RA‐Series Bicyclic Peptides from Rubia cordifolia L. |
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Authors: | Dr. Yukio Hitotsuyanagi Masumi Odagiri Saori Kato Jun‐ichi Kusano Tomoyo Hasuda Haruhiko Fukaya Prof. Dr. Koichi Takeya |
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Affiliation: | School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432‐1 Horinouchi, Hachioji, Tokyo 192‐0392 (Japan), Fax: (+81)?42‐677‐1436 |
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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. |
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Keywords: | configuration determination cytotoxicity peptides structure elucidation total synthesis |
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