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Structure elucidation of a new isoflavone by exclusive use of 1 H NMR measurements
Author(s) -
Ortega Alfredo R.,
Toscano Rubén A.,
HernándezBarragán Angelina,
AlvarezCisneros Celina,
JosephNathan Pedro
Publication year - 2015
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4278
Subject(s) - chemistry , triclinic crystal system , orthorhombic crystal system , crystallography , crystal structure , solid state , solid state nuclear magnetic resonance , diffraction , single crystal , stereochemistry , nuclear magnetic resonance , physics , optics
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.