Isokotanins A-C: new bicoumarins from the sclerotia of Aspergillus alliaceus

Three new bicoumarin metabolites, isokotanins A 1], B 2], and C 3], were isolated from the sclerotia of Aspergillus alliaceus. Isokotanin A is a regioisomer of the known bicoumarin kotanin 4]. The structures and spectral assignments for 1-3 were determined on the basis of selective INEPT, HMQC, and NOESY nmr data, as well as by chemical interconversions. Isokotanins B and C show activity against the corn earworm Helicoverpa zea and the dried fruit bettle Carpophilus hemipterus. The known compounds kotanin 4], desmethylkotanin 5], nominine, and paspaline were also isolated from extracts of A. alliaceus sclerotia.