Fusidane-Type Antibiotics from the Marine-Derived Fungus Simplicillium sp. SCSIO 41513

Simplifusidic acids A–K (1–11), 11 new fusidane-type nortriterpenoids, were isolated from the marine-derived fungus Simplicillium sp. SCSIO 41513. Compound 1 possessed an unprecedented fusidane triterpene skeleton with a 6/6/7/5/5 polycyclic system. Their structures were elucidated by spectroscopic methods, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra, comparison of experimental ECD spectra, and single-crystal X-ray diffraction analysis. Compound 9 showed strong antibacterial activity toward Staphylococcus aureus with an MIC value of 0.078 μg/mL. Their structure–bioactivity relationship was also discussed.从海洋来源真菌简瓶霉属（Simplicillium sp.）菌株SCSIO 41513中分离得到11个新的夫西烷型降三萜类化合物简夫萨酸A-K（1~11）。化合物1具有前所未有的夫西烷型三萜骨架，其包含6/6/7/5/5多环体系。通过波谱学方法解析了所有化合物的结构，并通过电子圆二色谱（Electronic Circular Dichroism，ECD）的量子化学计算、实验ECD光谱比对以及单晶X射线衍射分析，进一步确定了它们的绝对构型。化合物9对金黄色葡萄球菌（Staphylococcus aureus）展现出强效抗菌活性，最低抑菌浓度（Minimum Inhibitory Concentration，MIC）值为0.078 μg/mL。本研究还探讨了该类化合物的构效关系。