Tricycloalternarene Derivatives from the Endophytic Fungus Guignardia Bidwellii PSU-G11

Four new tricycloalternarene derivatives, guignarenones A–D (1–4), along with known (6S,9R)-vomifoliol were isolated from the endophytic fungus Guignardia bidwellii PSU-G11. Their structures were determined on the basis of spectroscopic data. The absolute configurations in 1 were assigned using a combination of the modified Mosher's method and NOEDIFF data. Compound 1 displayed mild cytotoxic activity against oral cavity cancer and African green monkey kidney fibroblast (Vero) cell lines.