Chromones Featuring a [6,6]-Spiroketal Moiety Produced by Coculture of the Endophytic Fungi and .

Under the guidance of HPLC-DAD analysis, ten new chromones featuring a rare [6,6]-spiroketal moiety, namely chaetovirexylariones A-J (-), together with two known congeners (-), were isolated from coculture of the endophytic fungi and , from the rhizome of the medicinal plant Roxb. Their structures were elucidated via a combination of NMR and HRESIMS data, and the absolute configurations of - were determined by the chemical conversion and single-crystal X-ray diffraction (Cu Kα) experiments, as well as the comparison of the experimental and calculated electronic circular dichroism (ECD) data. Compound is the first report as a racemate of this type of natural product. Compound represents the first example of a [6,6]-spiroketal chromone bearing a 5-amino-3-methyl-2-pentenoic acid fragment. Compound demonstrated a reduction in PTX resistance of SW620/AD300 by a factor of 45, and had the potential to be an effective P-gp inhibitor and an antitumor chemotherapy sensitizer.