Mechanistic studies of La3+- and Zn2+-catalyzed methanolysis of aryl phosphate and phosphorothioate triesters. Development of artificial phosphotriesterase systems
作者:Tony Liu、Alexei A. Neverov、Josephine S. W. Tsang、R. Stan Brown
DOI:10.1039/b502569a
日期:——
The methanolyses of a series of O,O-diethyl O-aryl phosphates (2,5) and O,O-diethyl S-aryl phosphorothioates (6) promoted by methoxide and two metal ion systems, (La3+)2(-OCH3)2 and 4:Zn2+:-OCH3 (4 = 1,5,9-triazacyclododecane) has been studied in methanol at 25 degrees C. Bronsted plots of the logk2 values vs. pKa for the phenol leaving groups give beta(lg) values of -0.70, -1.43 and -1.12 for the
甲醇和两个金属离子系统(La3 +)2(-OCH3)促进的一系列O,O-二乙基O-芳基磷酸酯(2,5)和O,O-二乙基S-芳基硫代磷酸酯(6)的甲醇分解2和4:在25°C的甲醇中研究了Zn2 +:-OCH3(4 = 1,5,9-三氮杂环十二烷)。苯酚离去基团的logk2值与pKa的布朗斯特图给出了β(lg)的值对于分别由甲醇盐,La3 +和Zn2 +系统促进的硫代磷酸酯的甲醇分解,-0.70,-1.43和-1.12,对磷酸酯的甲醇分解为-0.63,-0.87和-0.74。根据常见机理分析了金属催化反应的动力学数据,其中在限速过渡态中P-XAr键被广泛裂解。讨论了这些发现与磷酸三酯酶的作用机理的相关性。