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

Abstract

A total of eleven new dimeric chromanones, paecilins F-P (<b>2</b>-<b>12</b>), were isolated from the endophytic fungus <i>Xylaria curta</i> E10, along with four known analogs (<b>1</b>, <b>13</b>-<b>15</b>). 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 <b>1</b> showed antifungal activity against the human pathogenic fungus <i>Candida albicans</i> with a minimum inhibitory concentration of 16 μg/mL, and Compounds <b>8</b> and <b>10</b> showed antibacterial activity against the gram-negative bacterium <i>Escherichia coli</i> with the same minimum inhibitory concentration of 16 μg/mL.