Some problems in the structural elucidation of fungal metabolites

In the structural elucidation of natural products, problems may arise owing to extensive signal overlap and line broadening in the NMR spectra as well as unexpected chemical reactions. This is illustrated in the analysis of some novel compounds isolated from fruit bodies of toadstools and slime moulds, including infractopicrin, lascivol, retipolide A, arcyroxepin A and rubroflavin. In some cases, the problems could be solved by spectroscopic techniques such as two-dimensional INADEQUATE experiments, nuclear Overhauser enhancement measurements or X-ray structural analysis; in other cases, chemical transformations were necessary to resolve the structure.