Tetracyclic terpenoids from Dasyscyphus niveus, dasyscyphins D and E

Cultures of the ascomycete Dasyscyphus niveus have yielded two new tetracyclic dasyscyphin-type terpenoids (1 and 2), and their structures were elucidated by NMR spectroscopy and X-ray crystallography. The absolute configuration of dasyscyphin D (1) was determined by synthesis and NMR spectroscopy of diastereomeric MTPA esters. Both compounds inhibited the germination of conidia of Magnaporthe grisea at 25 microg/mL.