Pseudapenes A−C, Sesquiterpenoids from the Marine-Derived Fungus Pseudallescheria apiosperma F52-1

Abstract Three sesquiterpenoids pseudapenes A−C ( 1 − 3 ) were isolated from the marine-derived fungus Pseudallescheria apiosperma F52-1. Pseudapene A ( 1 ) has an unprecedented 2-methyl-5-methylene-3-(2-methylbut-2-ene)-dicyclo(3, 3, 0)-octane carbon skeleton and pseudapenes B ( 2 ) and C ( 3 ) possess an unique 2-methyl-4-methylene-2-(2-methylpent-2-ene)-dicyclo(3, 2, 0)-heptane chemical scaffold. Their structures were determined by use of MS and NMR spectroscopic data, and ECD, optical rotation and 13 C NMR calculations.