19] Proton magnetic resonance spectroscopy of antibiotics

Abstract

Publisher Summary Proton magnetic resonance spectroscopy (PMR) of antibiotics is a specific application of the general nuclear magnetic resonance (NMR) technique. The greatest utility of this relatively new form of spectroscopy is in the area of molecular structure determination, where it complements some of the more traditional methods but displaces some others. The principle is simple, but the instrumentation is complicated and expensive. The technique is still undergoing rapid development, mostly to increase its sensitivity. Its applicability varies with the size and nature of the unknown antibiotic. If the resulting spectra are difficult to analyze they can usually be manipulated to make them simpler, and several additional procedures are available when the interpretation is stalled. The PMR method uses hydrogens as a probe for the molecular structure. It gives information on the environment around the hydrogens (i.e., what functional groups they are in), it tells which hydrogens are nearby each other (how the groups are connected), and it gives angular information (stereochemistry) on hydrogens which are vicinal, vinylic, or allylic. From this, the rest of the structure can often be filled in.