Phaseocyclopentenones A and B, Phytotoxic Penta- and Tetrasubstituted Cyclopentenones Produced by , the Causal Agent of Charcoal Rot of Soybean in Argentina.

Two new penta- and tetrasubstituted cyclopentenones, named phaseocyclopentenones A and B ( and ), together with guignardone A (), were isolated from cultures. The phytopathogenic fungus was isolated from infected soybean tissues showing charcoal rot symptoms in Argentina. Charcoal rot is a devastating disease considering that soybean is one of the main legumes cultivated in the world. Phaseocyclopentenones A and B were characterized by 1D and 2D H and C NMR spectroscopic and HRESIMS spectrometric data and chemical methods as 4-benzoyl-3,4,5-trihydroxy-2-phenylcyclopent-2-enone and 3,5-dihydroxy-2,4-diphenylcyclopent-2-enone, respectively. The relative configuration of phaseocyclopentenones A and B was assigned by H and NOESY NMR methods, while their absolute configurations were assigned by electronic circular dichroism methods. When assayed on a nonhost plant ( L.) by the leaf puncture assay, phaseocyclopentenones A and B and guignardone A showed phytotoxic activity, while only and were toxic when tested on cuttings of the same plant. No phytotoxicity or antifungal activity was detected for the three compounds on the host plant soybean ( L.) and against some of its fungal pathogens, namely, and , also isolated from infected soybean plants in Argentina.