Herbarulide, a ketodivinyllactone steroid with an unprecedented homo-6-oxaergostane skeleton from the endophytic fungus Pleospora herbarum

The novel ketodivinyllactonic steroid, herbarulide (1), deviating from the brassinosteroids in the position of the oxygen, was isolated from the endop hytic fungus Pleospora herbarum. The structure was determined by extensive NMR studies, including particularly HMQC and HMBC experiments.