Ring-closing metathesis for the synthesis of side chain knotted pentapeptides inspired by vancomycin

A versatile method for the synthesis of bicyclic side chain knotted peptides inspired by vancomycin is described. The synthetic approach is based on the incorporation of a central amino acid derivative having two allylic groups-introduced by a Stille coupling-into pentapeptide 8 containing two allylated serine residues. Treatment of this bis-ring-closing metathesis precursor with 2nd generation Grubbs catalyst results in the formation of a bicyclic pentapeptide with the correct side chain to side chain connectivity pattern as observed in vancomycin: i- 2 --> i, i --> i + 2. Modelling studies using MacroModel hint at a cavity-like structure of the bicyclic pentapeptide which may bind suitable ligands.