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Structural and conformational study of macrocyclic polyethers by NMR spectroscopy and molecular modeling
Author(s) -
Philippon A.,
Laguerre M.,
Petraud M.,
Pianet I.
Publication year - 1997
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199711)35:10<691::aid-omr155>3.0.co;2-6
Subject(s) - conformational isomerism , chemistry , nuclear magnetic resonance spectroscopy , spectroscopy , molecule , stereochemistry , organic chemistry , physics , quantum mechanics
Two macrocyclic polyether isomers were obtained by radical cyclization of ( E )‐8‐iodo‐3,6‐dioxaoctyl‐3‐ethoxycarbonylpropenoate and separated by liquid–solid chromatography over silica gel. They were characterized, for the first time, by two‐dimensional NMR; notably, the HMBC experiment gave access to the assignment of the two isomers through coupling via the carbonyl oxygen belonging to the macroheterocycle. The determination of the 3 J HH coupling, associated with Monte Carlo simulation, gave information on the conformational space of these two isomers and showed that 85 conformers for one isomer and 29 conformers for the other were in equilibrium in the solution mixture. These results are discussed with regard to the complexing properties of these macrocyclic polyethers. © 1997 John Wiley & Sons, Ltd.