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Note: Helix or No Helix of β ‐Peptides Containing β 3 hAla( α F) Residues?
Author(s) -
Jaun Bernhard,
Seebach Dieter,
Mathad Raveendra I.
Publication year - 2011
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201100023
Subject(s) - chemistry , dihedral angle , force field (fiction) , helix (gastropod) , alkane stereochemistry , stereochemistry , amide , crystallography , computational chemistry , crystal structure , organic chemistry , molecule , hydrogen bond , artificial intelligence , snail , computer science , biology , ecology
A remote 4 J (F,H) coupling (FC( α )C(O)NH) of up to 4.2 Hz in α ‐fluoro amides with antiperiplanar arrangement of the CF and the CO bonds (dihedral angle FCCO 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.