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Coexistence of Hydrogen‐Bonded Loop and Extended Tetrapeptide Conformations
Author(s) -
Cervetto Valentina,
Pfister Rolf,
Kolano Christoph,
Bregy Harald,
Heimgartner Heinz,
Helbing Jan
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700396
Subject(s) - thioamide , tetrapeptide , chemistry , hydrogen bond , amide , loop (graph theory) , infrared spectroscopy , crystallography , infrared , intramolecular force , acetonitrile , resonance (particle physics) , hydrogen , stereochemistry , nuclear magnetic resonance spectroscopy , deuterium , group (periodic table) , molecule , organic chemistry , peptide , physics , atomic physics , biochemistry , mathematics , combinatorics , optics
The conformations of a protected tetrathiopeptide have been analysed by isotope labelling and two‐dimensional infrared spectroscopy (2D‐IR). It has been found that Boc‐Ala‐Gly(S)‐Ala‐Aib‐OMe in acetonitrile, as well as its oxopeptide analogue, can adopt a hydrogen‐bonded loop conformation in coexistence with less restricted structures. The two types of conformations interconvert too quickly to be resolved on the nuclear magnetic resonance (NMR) timescale, but give rise to different cross peaks in two‐dimensional infrared spectra. The hydrogen bond between the Boc terminal group and the amide proton of Aib can be broken by photoisomerisation of the thioamide bond.