Preface

Proton Nuclear Magnetic Resonance (1H NMR) is a science to study the relationship between the energy level transitions of hydrogen nuclei in organic compounds under the action of magnetic field and the chemical environment in molecules. The NMR data of organic compounds mainly include the chemical shift (resonance frequency), the number of hydrogen atoms, the peak shape (peak splitting), and the coupling constant of hydrogen functional groups, which are closely related to the structure of organic compounds. In the process of conducting structural identification of organic compounds, we deeply feel that although we have understood the basic principle of nuclearmagnetic resonance phenomenonand the basic theory of chemical shift, peak integral area, spin coupling and spin splitting, coupling constant and so on, if there is no perceptual knowledge about nuclear magnetic resonance of various hydrogen functional groups in organic compounds, it is not enough to help us to analyze the structure of organic compounds skillfully. In addition, in the short 30 years from 1990s to now, with the theory and technology of NMR and computer science becomingmore and more mature, the research on the structure of organic compounds has tended to be micro, fast, and accurate, which greatly shortens the research period of natural organic compounds. On the basis of the development and wide application of separation and purification technology of natural organic compounds represented by conventional chromatography and preparative liquid chromatography, a large number of natural organic compounds with relatively complex structures have been identified, and the NMR signals of these compounds have been fully assigned, thus accumulating a large number of spectral data of natural organic compounds. These data are very important for researchers engaged in the research of organic chemistry (including natural organic chemistry), because they not only help to simplify the structural identification of known compounds obtained in organic chemistry research, but also can be used as an important reference in the structural identification of new similar compounds and even novel compounds. Natural organic chemistry is a basic subject to study the organic composition, structure, and change law of natural biological resources. It has been playing an important role in the research of organic chemistry, pharmaceutical chemistry, biochemistry, botany, and other disciplines, as well as the development of pharmaceutical industry and pesticide industry. For example, through the application of various natural organic compounds separation and purification methods and modern organic structure identification methods, tens of thousands of plant secondary metabolites have been identified in the field of phytochemistry, which not only greatly enriched the structure and types of organic compounds, but also proved that many components have significant physiological activities, or play an important role in the process of plant life. But, the chemical composition ofmanynatural plant resources has not been fully elucidated, and the novel structure still attracts the majority of phytochemical