(+)- and (−)-Preuisolactone A: A Pair of Caged Norsesquiterpenoidal Enantiomers with a Tricyclo[4.4.0^1,6.0^2,8]decane Carbon Skeleton from the Endophytic Fungus <i>Preussia isomera</i>

Abstract

A pair of enantiomeric norsesquiterpenoids, (+)- and (−)-preuisolactone A (1) [(+)-1 and (−)-1)] featuring an unprecedented tricyclo[4.4.01,6.02,8]decane carbon scaffold were isolated from Preussia isomera. Their structures were determined by spectroscopic and computed methods and X-ray crystallography. Compounds (+)-1 and (−)-1 are two rare naturally occurring sesquiterpenoidal enantiomers. A plausible biosynthetic pathway for 1 is proposed. Additionally, (±)-1 exhibited remarkable antibacterial activity against Micrococcus luteus with an MIC value of 10.2 μM.