New insight into the stereochemistry of botryosphaeridione from a Phoma endophyte

A dihydronaphthalene-2,6-dione derivative, isolated from Phoma sp. LN-16, an endophytic fungus associated with Melia azedarach, was identified by spectroscopic data as a previously reported compound, botryosphaeridione (1). The relative configuration was reassigned by quantum chemical analysis of experimental 13C NMR and NOESY data. The first unequivocal assignment of its absolute configuration was made by using circular dichroism spectra and computational model B3LYP/aug-cc-pVDZ as (−)-(5R,6S)-1, and was also established by means of X-ray diffraction. Also, this is the first time that a trinor-eremophilane sesquiterpene is described for Phoma genus.