Maydisens,\nSesterterpenoids with Anti-MDR Activity\nfrom <i>Bipolaris maydis</i>

Fourteen\npreviously undescribed sesterterpenoids (<b>1</b>–<b>14</b>) were isolated from <i>Bipolaris maydis</i>.\nTheir structures with absolute configurations were elucidated by\nNMR, HRESIMS, DP4+ calculations, ECD calculations, single-crystal\nX-ray diffraction analyses, and the modified Mosher’s method.\nCompounds <b>1</b>–<b>5</b> possess an uncommon\n5/11 bicyclic ring system identified from <i>B. maydis</i> for the first time. Compounds <b>6</b>–<b>14</b> have a 5/8/5 tricyclic ring system, and these compounds both possess\ncarbonyl groups in ring A. Compound <b>10</b> showed significant\nreversal of paclitaxel resistance in cancer cells.