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 EC50 values of 65.4 and 57.0 μg/cm2, respectively.