Note: Helix or No Helix of β‐Peptides Containing β³hAla(αF) Residues?

A remote 4 J (F,H) coupling (FC( α )C(O)NH) of up to 4.2 Hz in α ‐fluoro amides with antiperiplanar arrangement of the CF and the CO bonds (dihedral angle FCCO ca. 180°) confirms that previous NMR determinations, using the XPLOR‐NIH procedure, of the secondary structures of β ‐peptides containing β 3 hAla( α F) and β 3 hAla( α F 2 ) residues were correct. In contrast, molecular‐dynamics (MD) simulations, using the GROMOS program with the 45A3 force field, led to an incorrect conclusion about the relative stability of secondary structures of these β ‐peptides. The problems encountered in NMR analyses and computations of the structures of backbone‐F‐substituted peptides are briefly discussed.