Pestalotiopsins A and B:  New Caryophyllenes from an Endophytic Fungus of Taxus brevifolia

Two new caryophyllene sesquiterpenes have been isolated from Pestalotiopsis sp., an endophytic fungus associated with the bark and leaves of Taxus brevifolia. Pestalotiopsin A (1) has a novel oxatricyclic ring system while pestalotiopsin B (3) exists as two slowly equilibrating atropisomers (6:5 ratio of ββ:βα) in chloroform solution at room temperature. Structures of 1 and 3 were determined by spectroscopic analyses and single-crystal X-ray diffraction.