(+)-Negamycin (1), a natural dipeptidic antibiotic bearing a hydrazide structure, exhibits a readthrough activity toward the nonsense mutation of the dystrophin gene and restores dystrophin expression in muscles of Duchenne muscular dystrophy model mdx mice. Herein to develop more potent readthrough compounds, we performed a structure activity relationship (SAR) study of 3-epi-deoxynegamycin (2), which is also another natural readthrough compound with little antimicrobial activity, focusing on the main carbon chain length. We found that one carbon atom shorter derivative 9b shows a higher readthrough activity than 1 and 2. Further derivatization at the carboxylic acid part of 9b demonstrates that its meta-chlorobenzyl ester derivative 17e, which has a higher ClogP value, exhibits a more potent readthrough activity than 9b. Interestingly, in the cell-free protein expression system, the readthrough activity of 17e drastically decreases compared to that in the cell-based assay. These results suggest that benzyl ester-type derivatives enhance the hydrophobicity and function as prodrugs to produce active compound 9b in living cell systems.
(+)奈加霉素(1)为一种带有
肼结构的天然二肽类抗生素,对 dystrophin
基因的无义突变具有通读活性,并在杜兴氏肌肉营养不良症模型 md x 小鼠肌肉中恢复 dystrophin 的表达。为了开发更有效的通读化合物,我们对携带少量抗微
生物活性的另一种天然通读化合物 3-表脱氧奈加霉素(2)进行了结构活性关系研究,侧重于主碳链长度的研究。我们发现比(1)和(2)少一个碳原子的衍
生物 9b 拥有更高的通读活性。进一步对 9b 的
羧酸部分进行衍化发现,它的邻
氯苯甲酯衍
生物17e 具有更高的 ClogP 值,17e 的通读活性比 9b 更强。有趣的是,在细胞自由蛋白表达系统中,17e 的通读活性相比于细胞基的测定有着大幅下降。这些结果表明,苯甲
酯类衍
生物提高了疏
水性,并作为前药在活细胞体系中生成具有活性的化合物9b。