Trichoverroid stereoisomers.

Trichoverroids, which lie along the biosynthetic path between the simple and the macrocyclic trichothecenes, have been characterized previously as sets of diastereomers that have the S-configuration at C-6' and are epimeric at C-7'. An isolate of Myrothecium verrucaria (ATCC 20540), which is the only species of Myrothecium reported to produce the macrocyclic trichothecene isororidin E (3a), produces trichoverrols (1) and trichoverrins (2) that are epimeric at C-7' but that have R-configurations at the C-6' centers. Also reported are several additional naturally occurring C6'R-series trichoverroids that have varied structural modifications, including several E,Z-isomers 7-9, 9 beta,10 beta-epoxides 11a and b, 12,13-deoxyisotrichoverrin B (10), and 8 alpha-hydroxyisotrichoverrin A (12).