Skeletal Isomerization of Ergosterol-5,8-Peroxide Leading to the Discovery of Unprecedented Ergostanes and Collective Syntheses of 5,6-Epoxysterols and (+)-Sarocladione.

Skeletal isomerization of ergosterol peroxide, a primary oxidation product of ergosterol, was investigated under thermal and iron(II)-mediated conditions. Thermal isomerization resulted in not only the isolation of the predicted 7-hydroxy-5,6-epoxides but also the discovery of the unprecedented 7/9/5-ring-fused ergostane for the first time. The iron(II)-mediated isomerization proceeded at ambient temperature, resulting in the formation of the expected 5,6-epoxysterols and a ring-opened bicyclic diketone.