Structures of Cordypyridones A−D, Antimalarial N-Hydroxy- and N-Methoxy-2-pyridones from the Insect Pathogenic Fungus Cordyceps nipponica

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Abstract
Bioassay-guided fractionation of the extracts from the insect pathogenic fungus Cordyceps nipponica BCC 1389 led to the isolation of N-hydroxy- and N-methoxy-2-pyridones, cordypyridones A−D (1−4). Structures of these compounds, including absolute configuration, were determined by spectroscopic methods, chemical conversions and single-crystal X-ray diffraction analyses. Codypyridones A and B, atropisomers of each other, exhibited potent in vitro antimalarial activity with IC50 values of 0.066 and 0.037 μg/mL, respectively, while their cytotoxicity was much weaker.