title: A Study about Regioisomeric Hydroquinones with Multiple Intramolecular Hydrogen Bonding.
abstract: A theoretical exploration about hydrogen bonding in a series of synthetic regioisomeric antitumor tricyclic hydroquinones is presented. The stabilization energy for the intramolecular hydrogen bond (IHB) formation in four structurally different situations were evaluated: (a) IHB between the proton of a phenolic hydroxyl group and anortho-carbonyl group (forming a six-membered ring); (b) between the oxygen atom of a phenolic hydroxyl group and the proton of an hydroxyalkyl group (seven membered ring); (c) between the proton of a phenolic hydroxyl group with the oxygen atom of the hydroxyl group of a hydroxyalkyl moiety (seven-membered ring); and (d) between the proton of a phenolic hydroxyl group and an oxygen atom directly bonded to the aromatic ring inorthoposition (five-membered ring). A conformational analysis for the rotation around the hydroxyalkyl substituent is also performed. It is observed that there is a correspondence between the conformational energies and the IHB. The strongest intramolecular hydrogen bonds are those involving a phenolic proton and a carbonyl oxygen atom, forming a six-membered ring, and the weakest are those involving a phenolic proton with the oxygen atom of the chromenone, forming five-membered rings. Additionally, the synthesis and structural assignment of two pairs of regioisomeric hydroquinones, by 2D-NMR experiments, are reported. These results can be useful in the design of biologically-active molecules.
authors.affiliation: Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación, Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, Casilla 9845, Santiago 8940577, Chile. mmartinez@utem.cl.
authors.forename: Maximiliano
authors.initials: M
authors.lastname: Martínez-Cifuentes
authors.affiliation: Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Autopista Concepción-Talcahuano 7100, Talcahuano 4300866, Chile. wcardona@unab.cl.
authors.forename: Wilson
authors.initials: W
authors.lastname: Cardona
authors.affiliation: Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santos Dumont 964, Casilla 233, Santiago 8380494, Chile. clsaitz@ciq.uchile.cl.
authors.forename: Claudio
authors.initials: C
authors.lastname: Saitz
authors.affiliation: Departamento de Química, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago 7800003, Chile. bweiss@uchile.cl.
authors.forename: Boris
authors.initials: B
authors.lastname: Weiss-López
authors.affiliation: Instituto de Química de Recursos Naturales, Universidad de Talca, Av. Lircay s/n, Casilla 747, Talca 3460000, Chile. raraya@utalca.cl.
authors.forename: Ramiro
authors.initials: R
authors.lastname: Araya-Maturana
mesh_terms: D006860:Hydrogen Bonding; D006873:Hydroquinones / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D006873:Hydroquinones
keywords: AIM; DFT; NBO; hydrogen bond; hydroquinone