Dimericbiscognienyne A: A Meroterpenoid Dimer from Biscogniauxia sp with New Skeleton and Its Activity

Dimericbiscognienyne A (1) an unusual diisoprenyl-cyclohexene-type-meroterpenoid dimer, was isolated froth Biscogniauxia sp together with three new monomeric diisoprenyl-cyclohexene-type meroterpenoids (2-4) and one new isoprenyl-benzoic acid-type meroterpenoid (5). All structures were determined by extensive NMR spectroscopic methods quantum chemical calculations, chemical derivatization, and X-ray crystallography. The formation of 1 is related-to a unique intermolecular redox coupling Diels-Alder adduct reaction. Their cytotoxicities and short-term memory enhancement activities against Alzheimer's disease were assessed.