Aspersteroids A–C, Three Rearranged Ergostane-type Steroids from <i>Aspergillus ustus</i> NRRL 275
Lin Liu, Fangfang Duan, Ying Gao, Xiaogang Peng, Jinling Chang, Juan Chen, Hanli Ruan
Abstract
Aspersteroid A (1), a highly rearranged 1(10 → 6)-abeo-18,22-cyclosterol, together with two new 18,22-cyclosterols (2 and 3), was isolated from the culture extract of Aspergillus ustus NRRL 275. Their structures were determined by spectroscopic analysis, X-ray diffraction, modified Mosher’s method, and Rh2(OCOCF3)4-induced electronic circular dichroism experiments. Compound 1 represents a new carbon skeleton with an uncommon 6/6/6/5/5 ring system, which is presumably biosynthesized from A-ring scission, double 1,2-shifts, and C-18/C-22 cyclization. Compound 1 exhibited potent immunosuppressive and antimicrobial activities.
Topics & Concepts
ChemistryStereochemistryRing (chemistry)Circular dichroismOrganic chemistrySteroid Chemistry and BiochemistryNatural product bioactivities and synthesisPhytochemistry and Bioactive Compounds