Stereochemistry of the Roridins. Diastereomers of Roridin E

A careful investigation of cultures of Myrothecium verrucaria has shown that this fungus produces all four roridin E isomers (3a−d), diastereomeric at the C-6‘ and C-13‘ centers. The stereochemistries at these centers were established by a combination of X-ray crystallographic analysis, NMR spectroscopy, and chemical transformations. NMR data from these and other macrocyclic trichothecenes allows for the assignment of configurations at the C-6‘ and C-13‘ centers for most of these compounds, the exceptions being those congeners having a C-4‘ ketone group in the macrolide ring.