Cytochalasans from the Endophytic Fungus Xylaria cf. curta with Resistance Reversal Activity against Fluconazole-Resistant Candida albicans

Curtachalasins C-E (1-3), which have an unprecedent bridged 6/6/6/6 ring system, were identified from the endophytic fungus Xylaria cf. curta. Residual dipolar coupling analyses associating with density functional theory calculations were utilized to determine the relative configuration of noncrystallizable compound 2. The absolute configurations of 1-3 were determined by X-ray diffraction and electronic circular dichroism calculations. Remarkably, curtachalasin C (1) showed significant resistance reversal activity against fluconazole-resistant Candida albicans.