5-Enolpyruvylshikimate 3-Phosphate Synthase: Chemical Synthesis of the Tetrahedral Intermediate and Assignment of the Stereochemical Course of the Enzymatic Reaction
作者:Ming An、Uday Maitra、Ulf Neidlein、Paul A. Bartlett
DOI:10.1021/ja036627+
日期:2003.10.1
been accomplished. Combination of methyl dibromopyruvate with a protected shikimic acid derivative, phosphorylation, and lactonization afforded the intermediates (S)-15 and (R)-15, whose configurations were assigned by NMR. After introduction of the 3-phosphate group and deprotection, photoinitiated radical debromination of the dibromo analogues (S)-5 and (R)-5 was accomplished with tributyltin hydride
参与 5-enolpyruvylshikimate 3-磷酸合酶 (EPSPS) 催化的四面体中间体的两种非对映异构体的化学合成已经完成。二溴丙酮酸甲酯与受保护的莽草酸衍生物的组合、磷酸化和内酯化得到中间体 (S)-15 和 (R)-15,其构型由 NMR 指定。在引入 3-磷酸基团和脱保护后,在表面活性剂的存在下,在混合水性溶剂中用三丁基氢化锡完成二溴类似物 (S)-5 和 (R)-5 的光引发自由基脱溴,得到丙酮酸缩酮磷酸盐( R)-TI 和 (S)-TI,分别。这些化合物在高 pH 值下稳定,但在 pH 值 7 时分解,半衰期约为 10 分钟。(R)-TI 被证明对 EPSPS 是惰性的,而 (S)-TI 被酶转化为 5-烯醇丙酮酸莽草酸 3-磷酸、莽草酸 3-磷酸和磷酸烯醇丙酮酸的混合物。酶中间体在缩酮中心具有 S 构型的证明证实了作为反加成和顺式消除的机制。此外,似乎第二步的顺式