Georatusin, a Specific Antiparasitic Polyketide-Peptide Hybrid from the Fungus Geomyces auratus.

Georatusin (1), featuring a highly reduced, methylated polyketide moiety fused to a tryptophan by an amide and ester bond forming a 13-membered ring, was produced by the soil fungus Geomyces auratus. An HMQC-COSY spectrum was measured to build up the connectivities despite the overlapping proton signals. DQF-COSY, HETLOC, J-HMBC, and ROESY were implemented to determine the relative configuration of the flexible moiety. Georatusin (1) shows specific antiparasitic activities against Leishmania donovani and Plasmodium falciparum without obvious cytotoxicity. The biosynthesis of 1 was also proposed.