Study of CH/π Interactions in the Molecular Recognition between Acetyl Galactopyranoside and 6-substituted 2-Methoxypyridines and 2(1H)-Pyridones

Fabian Cuetara-Guadarrama, Karla Ramírez-Gualito, Gabriel Cuevas

Abstract


A series of 6-substituted 2-methoxypyridine and 2(1H)-pyridones was designed and synthesized for its evaluation in the molecular recognition of acetyl 2,3,4,6-tetra-O-methyl-b-D-galactopyranoside substrate. 1H-NMR titration (affinity constant Ka determination) and chemical shift perturbation experiments were performed to evaluate the capacity of these receptors to form CH/π interactions with the substrate. The addition of 2-methoxypyridines to the substrate effected up-field shift for the H3, H4 and H5 proton signals and down-field shift for the H2 proton signal of galactopyranoside substrate. The determined affinity constant Ka values for the association between 2(1H)-pyridones and galactopyranoside showed that molecular recognition was weak. These results have demonstrated the existence of weak CH/π interactions and have reflected their weak intermolecular nature. Finally DFT calculations were performed to illustrate the geometry of the molecular recognition between 2(1H)-pyridones and galactopyranoside.

Keywords


CH/p interactions; supramolecular chemistry; glycosides; non-covalent interactions; molecular recognition

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Copyright (c) 2017 Fabian Cuetara-Guadarrama, Karla Ramírez-Gualito, Gabriel Cuevas

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Journal of the Mexican Chemical Society (J. Mex. Chem. Soc.) Vol 61, No 3 (2017). Quarterly publication (July-September). Edited and distributed by Sociedad Química de México, A.C. Barranca del Muerto 26, Col. Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico City. Phone: +5255 56626837; +5255 56626823 Contact: soquimex@sqm.org.mx http://www.sqm.org.mx Editor-in-Chief: Ignacio González-Martínez. Indexed Journal. Certificate of reserved rights granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 04-2005-052710530600-102. Certificate of lawful title and content: Under procedure. ISSN-e granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): Under Procedure. ISSN granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 1870-249X. Postal registration of printed matter deposited by editors or agents granted by SEPOMEX: IM09-0312 Copyright © Sociedad Química de México, A.C. Total or partial reproduction is prohibited without written permission of the right holder. The Figures/schemes quality and the general contents of this publication are full responsibility of the authors. Updated October 26th, 2017 by Adriana Vázquez (editorial assistant, e-mail: editor.jmcs@gmail.com), J. Mex. Chem. Soc., Sociedad Química de México, A.C.