Penifulvins B-E and a silphinene analogue: sesquiterpenoids from a fungicolous isolate of Penicillium griseofulvum

Penifulvins B-E (2-5), four new sesquiterpenoids with a dioxa[5.5.5.6]fenestrane ring system, have been isolated from cultures of an isolate of Penicillium griseofulvum (NRRL 35584), together with a new silphinene derivative, 12-hydroxysilphinene-15-oic acid (6). Penifulvins B-E (2-5) are oxidized analogues of penifulvin A (1) and were identified by analysis of NMR and MS data. 12-Hydroxysilphinen-15-oic acid (6) is biogenetically similar, and penifulvins A-E are presumed to be derived from a silphinene precursor. The structures of 2-6, including absolute configuration, were assigned by analysis of NMR data and application of chemical methods.