Asperemestrins A–D, Emestrin Hybrid Polymers with Bridged Skeletons from the Endophytic Fungus <i>Aspergillus nidulans</i>
Qin Li, Aimin Fu, Mengsha Wei, Yang Xiao, Jie Yin, Jianzheng Huang, Xiao‐Nian Li, Qingyi Tong, Chunmei Chen, Hucheng Zhu, Yonghui Zhang
Abstract
Four emestrin hybrid polymers, asperemestrins A–D (1–4, respectively), were isolated from the fungus Aspergillus nidulans. Asperemestrins A–C are the first examples of emestrin–sterigmatocystin heterodimers bearing a 7/5/6/6/5/5/6/6/6 nonacyclic system with a 2,5-diazabicyclo[2.2.2]octane-3,6-dione core, while asperemestrin D features an unprecedented 2,15-dithia-17,19-diazabicyclo[14.2.2]icosa-4,8-diene-12,18,20-trione core skeleton. Their structures were determined by extensive spectroscopic data, electronic circular dichroism calculations, and single-crystal X-ray diffraction. Asperemestrin B showed moderate cytotoxicity against cancer cell lines, including SU-DHL-2, HEPG2, and HL-60.