Semisynthesis of an Analogue of Antitumor Bicyclic Hexapeptide RA-VII by Fixing the Ala-2/Tyr-3 Bond to <i>Cis</i> by Incorporating a Triazole <i>cis</i>-Amide Bond Surrogate

Abstract

We prepared an analogue of an antitumor bicyclic hexapeptide RA-VII whose amide configuration between residues 2 and 3 was fixed to cis by incorporating a triazole cis-amide bond surrogate. This analogue was shown, by NMR studies, to take almost the same conformation as that of the minor conformer of RA-VII. It showed no cytotoxic activity.