Protuboxepin C and protuboxepin D from the sponge-derived fungus <i>Aspergillus</i> sp SCSIO XWS02F40

<p>Two new diketopiperazine alkaloids, named protuboxepin C <b>(1)</b> and protuboxepin D <b>(2)</b>, which contain D-Phe residue and oxepin ring, were isolated from EtOAc extract of sponge-derived fungus <i>Aspergillus</i> sp SCSIO XWS02F40. Their structures were elucidated by 1D, 2D NMR and HRESIMS dates, and their absolute configurations were confirmed by single crystal X-ray diffraction experiments and CD analyses. The <i>in vitro</i> cytotoxicity of these two new compounds was further evaluated using A549 and Hela cell lines.