title: Stereospecific (5) JHortho,OMe couplings in methoxyindoles, methoxycoumarins, and methoxyflavones.
abstract: Long-range coupling constants (5) JHortho,OMe were measured in series of methoxyindoles, methoxycoumarins, and methoxyflavones by the modified J doubling in the frequency domain method. The COSY and NOESY spectra revealed the coupling of the -OMe group with a specific proton at the ortho position and its preferred conformation. Homonuclear (1) H-(1) H couplings were confirmed by irradiation of the -OMe signal. Density functional theory calculations of (5) JHortho,OMe using the modified aug-cc-pVTZ basis set evidenced that the Fermi contact term shows good agreement with the experimental J values. Accurate chemical shift and coupling constant values followed after iterative quantum mechanical spectral analysis using the PERCH software.
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico.
authors.forename: Celina
authors.initials: C
authors.lastname: Alvarez-Cisneros
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Muñoz
authors.forename: Oscar R
authors.initials: OR
authors.lastname: Suárez-Castillo
authors.forename: Nury
authors.initials: N
authors.lastname: Pérez-Hernández
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.forename: Martha S
authors.initials: MS
authors.lastname: Morales-Ríos
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
keywords: PERCH spin-spin simulation; long-range coupling constants; methoxycoumarins; methoxyflavones; methoxyindoles