Characterization of the Fusarium toxin equisetin: The use of phenylboronates in structure assignment

Article abstract of DOI:10.1021/ja00203a025

Fusarium equiseti has repeatedly been identified in environments where several genetically unrelated individuals each developed leukemia. The screens on cultures of this fungus revealed interesting biological activities and turned up equisetin, a previously identified yet uncharacterized metabolite. The molecule has now been shown to contain two domains, a bicyclic hydrocarbon and an N-methyltetramic acid, connected by a bridging carbonyl. The steric requirements of the two bridging carbon-carbon bonds dictated much of the physical and chemical behavior of the toxin. A phenylboronic ester derivative proved to be essential in defining the enol form of the tetramic acid and in making possible the assignment of the scalar and dipolar spin exchange interactions in the complete characterization of the molecule.