Conformational Preferences and Self-Template Macrocyclization of Squaramide-Based Foldable Modules.

Show simple item record Rotger Pons, María del Carmen Piña Capó, María de las Nieves Frontera Beccaria, Antonio Martorell Crespí, Gabriel Ballester Balaguer, Pablo José Deyà Serra, Pere Maria Costa Torres, Antonio 2018-10-09T10:45:27Z
dc.description.abstract [eng] Secondary squaramides have considerable potential as hydrogen bond donors and acceptors. In CHCl3 both, anti- and syn-squaramide rotamers are observed by NMR. The energetic barrier for anti/syn mutual interconversion determined by complete band shape analysis is 63 kJ mol-1. As in proline derivatives, a low rotational barrier is crucial for the design of foldable modules. In this paper, folding based on the low rotational barrier of squaramides is driven by donor atoms (N or O) located in the ç position of an alkyl chain of a secondary squaramide. We demonstrate that the resulting minimal module exists as a folded conformer through the formation of a nine-membered ring stabilized by intramolecular hydrogen bonding. Molecular mechanics calculations and NMR studies support the existence of these folded conformers. The intramolecularly hydrogen bonded conformers are clearly visible even in CHCl3-EtOH mixtures. Folding occurs even in pure ethanol. As an indirect test, we studied the effectiveness of macrocyclization reactions in pure ethanol that require an effective templating effect to take place. The high yields obtained support the dominant role of a folded conformer even in this solvent.
dc.format application/pdf
dc.relation.isformatof Versió postprint del document publicat a:
dc.relation.ispartof Journal of Organic Chemistry, 2004, vol. 69, num. 7, p. 2302-2308
dc.rights (c) American Chemical Society , 2004
dc.subject.classification 54 - Química
dc.subject.other 54 - Chemistry. Crystallography. Mineralogy
dc.title Conformational Preferences and Self-Template Macrocyclization of Squaramide-Based Foldable Modules.
dc.type info:eu-repo/semantics/article
dc.type info:eu-repo/semantics/acceptedVersion 2018-10-09T10:45:27Z info:eu-repo/date/embargoEnd/2075-01-01
dc.embargo 2075-01-01
dc.rights.accessRights info:eu-repo/semantics/embargoedAccess

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