title: NMR spectroscopic method for the assignment of 3,5-dioxygenated aromatic rings in natural products.
abstract: In recent years, certain "new" naturally occurring compounds (1-28) with 3,5-dioxygenated aromatic rings have been reported. A comparison of the NMR data of these compounds with the data of four model compounds (A-D) indicated that the structures of these "new" compounds were erroneous. The reason for the incorrect elucidation of the structures of 1-28 was attributed to "deceptively simple" (1)H NMR spectra, which displayed two broad singlets with integrations of 1:2 for H-2 and H-5, H-6, respectively. To expose the misleading results from the spectra, serial (1)H NMR experiments on compounds A-D were performed using various deuterated solvents and temperatures. The results revealed separated proton signals for the ABX system in certain deuterated solvents. Additionally, the characteristic differences between 3,4- and 3,5-dioxygenated aromatic rings in their (13)C NMR spectra are summarized based on our experiment and data reported. This approach is useful for analyzing the patterns of dioxygenated aromatic rings in natural products, especially when "deceptively simple" (1)H NMR spectra are displayed.
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Fu
authors.initials: F
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: An
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Zi-Ming
authors.initials: ZM
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Jian-Shuang
authors.initials: JS
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Pei-Cheng
authors.initials: PC
authors.lastname: Zhang
mesh_terms: D001688:Biological Products / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry; D017705:Lignans / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D011522:Protons; D012997:Solvents; D013696:Temperature
chemical_list: D001688:Biological Products; D005419:Flavonoids; D017705:Lignans; D011084:Polycyclic Aromatic Hydrocarbons; D011522:Protons; D012997:Solvents