Isocoumarindole A, a Chlorinated Isocoumarin and Indole Alkaloid Hybrid Metabolite from an Endolichenic Fungus <i>Aspergillus</i> sp.

Isocoumarindole A (1), a novel polyketide synthetase–nonribosomal peptide synthetase (PKS–NRPS) hybrid metabolite, was isolated from the endolichenic fungus Aspergillus sp. CPCC 400810. The structure of isocoumarindole A (1) was featured by an unprecedented skeleton containing chlorinated isocoumarin and indole diketopiperazine alkaloid moieties linked by a carbon–carbon bond, which was determined by a combination of spectroscopic analyses, Marfey’s method, and calculations of NMR chemical shifts, ECD spectra, and optical rotation values. Isocoumarindole A showed significant cytotoxicity and mild antifungal activities