Synthesis and Conformation of Fluorinated β‐Peptidic Compounds

Experimental and theoretical data indicate that, for α‐fluoroamides, the FCC(O)N(H) moiety adopts an antiperiplanar conformation. In addition, a gauche conformation is favoured between the vicinal CF and CN(CO) bonds in N ‐β‐fluoroethylamides. This study details the synthesis of a series of fluorinated β‐peptides ( 1 – 8 ) designed to use these stereoelectronic effects to control the conformation of β‐peptide bonds. X‐ray crystal structures of these compounds revealed the expected conformations: with fluorine β to a nitrogen adopting a gauche conformation, and fluorine α to a CO group adopting an antiperiplanar conformation. Thus, the strategic placement of fluorine can control the conformation of a β‐peptide bond, with the possibility of directing the secondary structures of β‐peptides.