Two New Ergosterol Derivatives from the Basidiomycete Cortinarius glaucopus

Two new sterols 1 and 2 and ␣ve known ones 3 – 7 were isolated for the ␣rst time from the fruiting bodies of Cortinarius glaucopus. Their structures were established by 1- and 2D-NMR spectra and HR-FABS-MS. The relative con␣guration of 1 was ␣rmly determined by comparison of the observed 1H–1H couplings and NOESY correlations, with those predicted for the computed geometries of the conformers. Calculations were performed by means of DFT with the B3LYP functional at 6-31 + G(d,p) level of theory, in CHCl3 as the solvent. The structures of the new ergosterol derivatives, called glaucoposterol A (1) and B (2), were thus established as (3S,5R,7R,10R,13R,17R, 20S,22R,23R,24R)-5,6-epoxy-3,7,23-trihydroxystrophast-8-en-14-one and (22E,3S,5S,9S,10R,13R,17R,20R,24R)-3,5-dihy- droxyergosta-6,8(14),22-trien-15-one, respectively. Moreover, the con␣guration of known strophasterol C (3) was determined as (3S,5R,6S,7R,10R,13R,17R,20S,22S,24R). Glaucoposterol A (1) and strophasterol C (3) represent the second ␣nding in nature of steroids with the rare strophastane skeleton.