formation of the 3-keto group and Δ7 double bond. The synthesized isomers were isolated and tested for their activity as DAF-12 ligands by AlphaScreen assays. Results showed a significant loss of potency and efficacy for all the four stereoisomers when compared to the parent endogenous ligand. Computational analysis has evidenced the configurational and conformational arrangement of both the carboxylic
                                    由
胆汁酸猪去氧胆酸制备 Δ7-
DAfachronic 酸的四种环丙基立体异构体,并用作
化学工具,以利用羧基尾和 C25-甲基的方向和空间分布对 
DAF-12 结合的重要性受体。合成路线基于 (a) Walden 反转和立体选择性 PtO 2-氢化将L形5β-
胆甾醇支架转化为平面5α-
甾醇中间体;(b) 通过 Wittig 和
环丙烷化反应对侧链进行双碳同系化;(c) 3-酮基和Δ7双键的形成。分离合成的异构体并通过 AlphaScreen 分析测试它们作为 
DAF-12 
配体的活性。结果显示,与母体内源性
配体相比,所有四种立体异构体的效力和功效均显着丧失。计算分析已经证明,
DAfachronic 酸的羧基和 C25-甲基基团的构型和构象排列是 
DAF-12 结合和活化的关键结构决定因素。