Cordycicadins A-D, Antifeedant Polyketides from the Entomopathogenic Fungus Cordyceps cicadae JXCH1.

Cordycicadins A-D ( 1 - 4 ) are four novel polyketides that were isolated from the liquid fermentation of the insect-pathogenic fungus Cordyceps cicadae JXCH1. The structures were determined by a combination of spectroscopic analysis, single-crystal X-ray diffraction, and computational methods. Compounds 1 , 3 , and 4 harbor an unusual exocyclic enol ether bridge that connects the separated ring systems. Hypothetical biosynthetic pathways for 1 - 4 were proposed. Cordycicadins A ( 1 ) and B ( 2 ) showed antifeedant activity against silkworm larvae ( Bombyx mori ) with EC 50 values of 65.4 and 57.0 μg/cm 2 , respectively.