Copper-Mediated Trimerization of Diazopeptides Generates Peptide Derivatives of Cis - and Trans -Aconitic Acid That Adopt Folded Structures

: The reaction of two diazopeptides with CuI in MeCN produces peptide derivatives of [E] and [Z]-aconitic acid via a trimerization reaction. Best yields of the trimeric products occur when 0.5 equiv of CuI is used. The conformations of the peptide derivatives of [E] and [Z]-aconitic acid were probed using computational and NMR methods. Both the isomers adopt a conformation having two intramolecular hydrogen bonds, where two of the peptide chains are parallel to each other, while the other is perpendicular.