Herbarone, a rearranged heptaketide derivative from the sea hare associated fungus Torula herbarum

Abstract

Herbarone (1), a novel heptaketide with a tetrahydro-5,9-methanobenzo[8]annulen-10(5H)-one skeleton, together with the new ent-astropaquinones B (2) and C (3) and four known pyranonaphthoquinones (4-7), was isolated from the sea hare associated fungus Torula herbarum. The structures of the new compounds were elucidated by detailed spectroscopic analysis, and the absolute configurations were determined by solution TDDFT/ECD calculations. Absolute configurations of the known compounds were studied by ECD measurements and calculations. The isolation of heptaketide 1 suggests that an intramolecular aldol reaction takes place to form the tricyclic scaffold.