Fungal metabolites. Part 45: The sesquiterpenes of Collybia maculata and Collybia peronata

The sesquiterpenes of Collybia maculata and C. peronata (Basidiomycetes) have been reinvestigated. In addition to collybolide, isocollybolide and deoxycollybolidol, five new structurally related sesquiterpene lactones have been isolated. The structures have been established by spectroscopic methods. Stereochemical assignments required a detailed conformational investigation, which has been carried out at the AM1 level for all compounds, and at the B3LYP level for some of them. This led to the inversion of the previously proposed C-7 configuration of deoxycollybolidol. The absolute configuration of collybolides could tentatively be inferred from CD studies.