A Highly Efficient Type I β-Turn Mimetic Simulating an Asx-Pro-Turn-Like Structure

Asx-Pro-turns have been identified with high frequency in protein structures nucleating type I beta-turns. By bridging the amino acid side chain in position i with a nitrogen substituent in position i+2 by ring-closing olefin metathesis (RCM), peptide mimetics of type 1 could be developed. NMR based conformational investigations indicated a stable intramolecular H-bond constraining a U-turn conformation that was predicted to simulate a type I beta-turn.