Two unique cytochalasans, curtachalasins A (1) and B (2), were purified from the endophytic fungus Xylaria curta E10 harbored in the plant Solanum tuberosum. Their structures were determined by extensive spectroscopic methods, X-ray crystallographic analysis, and electronic circular dichroism calculations. These two compounds feature an unprecedented pyrolidine/perhydroanthracene (5/6/6/6 tetracyclic skeleton) fused ring system.