Fourteen new polyketides with a trans-fused decalin ring system, libertalides A–N (3–16), together with two known analogues, aspermytin A and its acetate (1, 2), were isolated from the fermentation extract of a coral-derived Libertasomyces sp. fungus. Their relative configurations were elucidated on the basis of detailed spectroscopic analysis, and the absolute configurations were determined by TDDFT-ECD and optical rotation (OR) calculations. The OR of 1 and 2 were found to have opposite signs in CH₃CN and CHCl₃, which was in agreement with the OR calculations producing alternating signs for the optical rotation depending on the applied conditions. Because the signs of the OR for 1 and 2 showed high solvent dependence, they may not be used alone to correlate the absolute configurations. Compound 16 displayed structural novelty characterized by an α-enol ether bridge conjugated with an aldehyde group. In in vitro immunomodulatory screening, compounds 1, 4, and 10 significantly induced the proliferation of CD3⁺ T cells, while compounds 2, 7, 11, and 14 significantly increased the CD4⁺/CD8⁺ ratio at 3 μM. A preliminary structure–activity analysis revealed a crucial role of Δ⁷ and a terminal OH group in the regulation of CD3⁺ T cell proliferation. This is the first report of immunoregulatory activity for metabolites of this kind.

中文翻译：

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从软珊瑚中分离出的类Phoma真菌的免疫调节性聚酮化合物。

用十四新聚酮化合物的反式-融合萘烷环系统，libertalides A-N（3 - 16），加上两个已知类似物，aspermytin A及其乙酸酯（1，2），购自的珊瑚得到的发酵提取物中分离Libertasomyces sp。菌。在详细的光谱分析的基础上阐明了它们的相对构型，并通过TDDFT-ECD和旋光度（OR）计算确定了绝对构型。发现1和2的OR在CH ₃ CN和CHCl _3中具有相反的符号，这与OR计算相符，这取决于所应用的条件会为旋光产生交替的符号。因为1和2的OR符号显示出高度的溶剂依赖性，所以可能不能单独使用它们来关联绝对构型。化合物16表现出结构新颖性，其特征在于与醛基共轭的α-烯醇醚桥。在体外免疫调节筛选，化合物1，4，及10显著诱导CD3的增殖⁺ T细胞，而化合物2，7，11，和14在3μM时显着增加了CD4 ⁺ / CD8 ⁺比率。初步结构-活性分析揭示Δ的至关重要的作用⁷在CD3的调节和末端OH基团⁺ T细胞增殖。这是此类代谢产物免疫调节活性的首次报道。