title: Structure elucidation of a new isoflavone by exclusive use of ¹H NMR measurements.
abstract: The leaves of Piscidia carthagenensis provided new 7,2',5'-trimethoxy-3',4'-methylenedioxyisoflavone (1), admixed with known 6,7-dimethoxy-3',4'-methylenedioxyisoflavone (2), and 5,4'-dihydroxy-7,2',5'-trimethoxyisoflavone (3), which were separated by extensive fractional solubillization. Selective irradiation of the H-5 "singlet" of 2 allowed distinction of the two methoxy group signals, whose chemical shift difference is only 0.004 ppm (1.2 Hz at 300 MHz). The (1)H and (13)C NMR data of 3 were assigned with the aid of HETCOR and gHMBC measurements. Although 1 looked inhomogeneous in the solid state, its solution structure followed from (1)H NMR measurements, where it looked homogeneous. To clarify the solid state aspect and confirm the structure of 1, two types of crystals were mechanically separated and subjected to single crystal X-ray diffraction measurements. This study revealed polymorphism because of the concomitant presence of orthorhombic and triclinic crystals, but showed no atropisomerism. The structure of 3 was also verified by X-ray diffraction crystallography.
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico.
authors.forename: Alfredo R
authors.initials: AR
authors.lastname: Ortega
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico.
authors.forename: Rubén A
authors.initials: RA
authors.lastname: Toscano
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México, Mexico.
authors.forename: Angelina
authors.initials: A
authors.lastname: Hernández-Barragán
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México, Mexico.
authors.forename: Celina
authors.initials: C
authors.lastname: Alvarez-Cisneros
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México, Mexico.
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
mesh_terms: D006859:Hydrogen; D007529:Isoflavones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D014961:X-Ray Diffraction
chemical_list: D007529:Isoflavones; D006859:Hydrogen