Ophiosphaerellins A–I, Polyketide-Derived Compounds from the Endolichenic Fungus Ophiosphaerella korrae

Ophiosphaerellins
A–I (1–9), the first example
of bicyclo[4.1.0]­heptenones, as well as their
biosynthetic relatives ophiosphaerekorrins A–B (10–11) were isolated from the endolichenic fungus Ophiosphaerella korrae. Biosynthetically, they were
derived from the polyketide pathway, and their absolute configurations
were determined on the basis of the combination analysis of spectral
data, circular dichroism calculations, and single-crystal X-ray diffraction
measurement. Preliminary test with thin-layer chromatography bioautography
found that this type of compounds showed moderate acetylcholinesterase
(AChE) inhibitory effects.