Pestalotiopsins A and B:  New Caryophyllenes from an Endophytic Fungus of <i>Taxus brevifolia</i>

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.