Asperversiamides, Linearly Fused Prenylated Indole Alkaloids from the Marine-Derived Fungus Aspergillus versicolor

Abstract

Asperversiamides A-H (1-8), eight linearly fused prenylated indole alkaloids featuring an unusual pyrano[3,2- f]indole unit, were isolated from the marine-derived fungus Aspergillus versicolor. The structures and absolute configurations of these compounds were elucidated by extensive spectroscopic analyses, single-crystal X-ray diffraction, electronic circular dichroism (ECD) calculations, and optical rotation (OR) calculations. The relative configuration of C-21 of iso-notoamide B was herein revised, and a new methodology for preliminarily determining if the relative configuration of the bicyclo[2.2.2]diazaoctane moiety of a spiro-bicyclo[2.2.2]diazaoctane-type indole alkaloid is syn or anti was developed. The anti-inflammatory activities of the isolated compounds were all tested, and of these compounds, 7 exhibited a potent inhibitory effect against iNOS with an IC₅₀ value of 5.39 μM.