title: Effect of methoxyl groups on the NMR spectra: configuration and conformation of natural and synthetic indanic and tetralinic structures.
abstract: Here, we studied the influence of the methoxyl groups attached at C-7 and C-2' of natural and synthetic 1-arylindanes on the chemical shift of the signal of bibenzylic hydrogen and carbon atoms and J1,2coupling constants. This influence was also analysed in natural 1-aryltetralins and related compounds that possess methoxyl and/or hydroxyl groups bound at C-8 and C-2'. The methoxyl groups attached at C-7 in indanes or at C-8 in tetralins produce a deshielding signal at H-1 and shield at C-1 and a strong decrease in the value of J1,2due to the pseudoequatorial location adopted by the aryl group bound at C-1, avoiding an 'A1,3strain'. Furthermore, compounds with hydroxyl or methoxyl groups in C-2', in the absence of substituents of C-7 or C-8, present a strong deshielding signal at H-1, strong shield of the C-1 signal and a decrease in the value of J1,2. This is attributed to the stereoelectronic effects of the methoxyl or hydroxyl groups, which we have called 'Asarone effect'. NOESY experiments were conducted to confirm the configuration and conformation of some of the compounds included in this work. This study shows that both effects, A1,3strain and Asarone effect, must be taken into account when the structure of natural indanes and tetralins is analysed by using1H-NMR and13C-NMR spectra. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Av. Constituci, 6700, Argentina.|Cátedra de Química Orgánica II, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113, Ciudad de Buenos Aires, Argentina.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Lantaño
authors.affiliation: Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Av. Constituci, 6700, Argentina.
authors.forename: José M
authors.initials: JM
authors.lastname: Aguirre
authors.affiliation: Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Av. Constituci, 6700, Argentina.
authors.forename: Eleonora V
authors.initials: EV
authors.lastname: Drago
authors.affiliation: Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Av. Constituci, 6700, Argentina.
authors.forename: Diego J
authors.initials: DJ
authors.lastname: de la Faba
authors.affiliation: Cátedra de Química Orgánica II, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113, Ciudad de Buenos Aires, Argentina.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Pomilio
authors.affiliation: Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Av. Constituci, 6700, Argentina.
authors.forename: Jorge D
authors.initials: JD
authors.lastname: Mufato
keywords: 13C-NMR; 1H-NMR; indans; tetralins