AFLAVAZOLE - A NEW ANTIINSECTAN CARBAZOLE METABOLITE FROM THE SCLEROTIA OF ASPERGILLUS-FLAVUS

Extracts of the sclerotia of the common mold Aspergillus flavus deter feeding by the fungivorous insect Carpophilus hemipterus.1,2 Our initial studies of this phenomenon led to the isolation and structure determination of four aflavinine derivatives (1–4) (Chart I) responsible for most of the antifeedant activity. One additional major antiinsectan indole metabolite was present in the chloroform extract of A. flavus sclerotia,3 but its spectral data were significantly different from those of 1–4. Recently, studies of another Aspergillus sp. (A. tubin-gensis) have led us to isolate representatives of a new class of biologically active indole diterpene-derived metabolites containing a carbazole moiety (e.g., 5).4 Examination of the spectral data for the remaining A. flavus metabolite and comparison with the data for 5 have permitted us to assign the structure of this new compound as 6. This metabolite, which we have named aflavazole, appears to be ubiquitous in sclerotial extracts of various strains of A. flavus and A. parasiticus and incorporates another previously unreported carbazole-containing ring system. Details of the isolation, structure elucidation, and biological activity of 6 are reported here. © 1990, American Chemical Society. All rights reserved.