Paecilins F–P, new dimeric chromanones isolated from the endophytic fungus Xylaria curta E10, and structural revision of paecilin A

A total of eleven new dimeric chromanones, paecilins F-P (2–12), were isolated from the endophytic fungus Xylaria curta E10, along with four known analogs (1, 13–15). Their structures and absolute configurations were determined by extensive experimental spectroscopic methods, single-crystal X-ray diffraction, and equivalent circulating density (ECD) calculations. In addition, the structure of paecilin A, which was reported to be a symmetric C8-C8′ dimeric pattern, was revised by analysis of the nuclear magnetic resonance (NMR) data, and single-crystal X-ray diffraction. Compound 1 showed antifungal activity against the human pathogenic fungus Candida albicans with a minimum inhibitory concentration of 16 μg/mL, and Compounds 8 and 10 showed antibacterial activity against the gram-negative bacterium Escherichia coli with the same minimum inhibitory concentration of 16 μg/mL.