21-Epi-taichunamide D and (±)-versicaline A, three unusual alkaloids from the endophytic Aspergillus versicolor F210
Huaqiang Li, Qianqian Xu, Weiguang Sun, Runge Zhang, Jianping Wang, Yongji Lai, Zhengxi Hu, Yonghui Zhang
Three new alkaloids, 21-epi-taichunamide D (1) and (±)-versicalin A ((±)-6), along with four known analogues (2–5) were isolated from the endophytic Aspergillus versicolor F210, which harbored in the bulbs of Lycoris radiata. Structurally, compound 1 is the third natural indole alkaloid with a rare methylsulfonyl unit, and (±)-6 existing as two pairs of keto-enol tautomers ((+)-6a/(+)-6b and (−)-6a/(−)-6b, respectively), represent the first naturally occurring alkaloids with a rare 2,3-dihydro-1H-isoindol-1-one unit fused to a tautomeric diisopentenyl cyclohexenone unit. The absolute structures of 1 and (±)-6 were characterized by extensive analyses of spectroscopic data, comparison of the electronic circular dichroic (ECD) data, and single-crystal X-ray diffraction analysis, respectively. Compound 6 exhibited moderate cytotoxicity against HL-60 cells with an IC50 value of 5.6 μM.
Circular dichroism, Absolute configuration, Medicinal, Pharmaceutical, Natural products