Three new metabolites, vibralactones D-F (1-3) were isolated from cultures of the basidiomycete Boreostereum vibrans. The relative configuration of I was established on the basis of X-ray diffraction analysis, while the absolute configurations of 1-3 were assigned using a modified Mosher's method. Compound I showed weak inhibitory activities against isozymes of 11 beta-hydroxysteroid dehydrogenases (HSD) with IC50 values of 85.7 mu M (human HSD1), 295.2 mu M (mouse HSD1), and 87.1 mu M (human HSD2).
