Importance of NMR in natural product chemistry

NMR spectroscopy is among the most powerful analytical techniques for the elucidation of chemical structure. It has the capability of providing detailed information about structure and dynamics of molecules as well as how atoms are connected to each other. NMR can identify different nuclei in a molecule and analyze large proteins and other large molecules using three dimensional (3-D) techniques. This instrument provides powerful information for the researcher to identify compounds, study the structure-function relationship of atoms or the molecules in which they are contained.

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool in structural characterization. It can be used to determine how all atoms of a particular molecule are interconnected. This is done by analyzing the chemical environment of a selected nucleus. When nuclei are placed into a magnetic field, their magnetic moment (spin) becomes aligned with the magnetic field. NMR uses a pulse of RF (radio frequency) energy to deflect the nuclei. When the energy is removed, the nuclei relax back to their original state and emit an electromagnetic pulse. A coil inside the NMR receives this RF pulse, and a computer transforms the signal into a spectral graph, which can be read by a scientist. Each nucleus relaxation translates into a peak in the NMR spectrum. Its location on the x-axis (chemical shift) and the multiplicity of the peak tells the scientist about its environment. The area of the peak corresponds to the number of nuclei experiencing the same environment