Mucha A, Kunert A, Grembecka J, Pawełczak M, Kafarski P
Department of Bioorganic Chemistry, Faculty of Chemistry, Wrocław University of Technology, Wybrzeze Wyspiańskiego 27, 50-370 Wrocław, Poland.
Eur J Med Chem. 2006 Jun;41(6):768-72. doi: 10.1016/j.ejmech.2006.03.023. Epub 2006 May 11.
Fully deprotected phosphonamidate dipeptides, predicted as effective inhibitors of cytosolic leucine aminopeptidase, showed unexpected instability in water solution at pH below 12. Their hydrolysis rate was strictly correlated with basicity of the N-terminal amino group. To improve this feature a phosphonamidate analogue containing less basic, aromatic 2-aminophenylphosphonate residue in P1 position of the inhibitor was designed. The target compound was synthesised starting from diethyl 2-nitrophosphonate in several step procedure. The decrease in basicity of the terminal amino moiety of the modified analogue in fact resulted in satisfactory improvement of hydrolytic stability of the P-N bond. The developed phosphonamidate was proved to be fully resistant to hydrolysis above pH 7. Surprisingly, tested in enzymatic assays towards leucine aminopeptidase (optimum pH 8.5), it did not exhibit inhibition activity up to milimolar concentration. The explanation could be that diminishing the basic character of the terminal amino group may result in a change of its affinity towards the zinc ions.
完全脱保护的氨基磷酸二肽被预测为胞质亮氨酸氨肽酶的有效抑制剂，但在pH值低于12的水溶液中表现出意外的不稳定性。它们的水解速率与N端氨基的碱性严格相关。为改善这一特性，设计了一种在抑制剂P1位置含有碱性较弱的芳香族2-氨基苯膦酸残基的氨基磷酸类似物。目标化合物从二乙基2-硝基膦酸酯开始，通过几步反应合成。事实上，修饰类似物末端氨基部分碱性的降低导致了P-N键水解稳定性的令人满意的提高。所开发的氨基磷酸酯在pH值高于7时被证明完全抗水解。令人惊讶的是，在针对亮氨酸氨肽酶（最适pH 8.5）的酶促试验中进行测试时，它在毫摩尔浓度下都没有表现出抑制活性。原因可能是末端氨基碱性的减弱可能导致其对锌离子亲和力的改变。
