Structures of cordypyridones A-D, antimalarial N-hydroxy- and N-methoxy-2-pyridones from the insect pathogenic fungus Cordyceps nipponica

Bioassay-guided fractionation of the extracts from the insect pathogenic fu ngus Cordyceps nipponica BCC 1389 led to the isolation of N-hydroxy- and N- methoxy-2-pyridones, cordypyridones A-D (1-4). Structures of these compound s, including absolute configuration, were determined by spectroscopic metho ds, chemical conversions and single-crystal X-ray diffraction analyses. Cod ypyridones A and B, atropisomers of each other, exhibited potent in vitro a ntimalarial activity with IC50 values of 0.066 and 0.037 mug/mL, respective ly, while their cytotoxicity was much weaker.