87603-17-6Relevant articles and documents
Peptide Conformations. 27. cyclo-. Synthesis and Conformation in the Crystal and in Solution
Kessler, Horst,Bermel, Wolfgang,Krack, Gerhard,Bats, Jan Willem,Fuess, Hartmut,Hull, William E.
, p. 3164 - 3181 (2007/10/02)
270, 300, and 500 MHz 1H and 67.89 MHz 13C NMR spectra of cyclo (1) (Bzl = N-Benzyl) were analyzed with the aid of two-dimensional techniques.A 300 MHz spin echo correlated 1H NMR spectrum (SECSY) yielded the information about coupling pattern.Small long range couplings, which are important for signal assignments, were detected by a special modification of the Jeener spectroscopy.This spectrum is compared with the conventional Jeener spectrum.Carbon- and proton-connectivities result from a 2D-1H-13C shift correlation.Coupling constants and chemical shift values in the proline rings were obtained by iterative simulation both seven-spin systems.The interpretation of the NMR parameters yields a rapid equilibrium between two boat conformations; one of them is strongly preferred (80percent).This conformation was also found in the X-ray crystal structure.
