Syntheses of amino nitrones. Potential intramolecular traps for radical intermediates in monoamine oxidase-catalyzed reactions
作者:Boyu Zhong、Xingliang Lu、Richard B. Silverman
DOI:10.1016/s0968-0896(98)80016-3
日期:1998.12
an amine radical cation and an alpha-radical during enzyme catalysis, there is no direct, i.e. EPR, evidence for these species as they are formed. Amino nitrones have been designed which, upon radical formation would produce an intermediate that is a resonance structure of the corresponding nitroxyl radical, which should be observable by EPR spectroscopy. Syntheses of seven different amino nitrones
单胺氧化酶(MAO)是一种黄素依赖性酶,可催化多种胺神经递质和有毒胺的氧化脱氨作用。尽管已经有一些研究支持在酶催化过程中胺基自由基阳离子和α-自由基的中介作用,但尚无直接的证据(即EPR)证明这些物种的形成。已经设计了氨基硝酮,其在形成自由基时会产生中间体,该中间体是相应的硝酰基自由基的共振结构,这可以通过EPR光谱法观察到。尝试合成七个不同的氨基硝酮,三个无环和四个环状类似物。被保护的氨基硝酮是稳定的,但是所有三个无环氨基硝酮都是不稳定的。一种环状类似物非常稳定(39),一种仅在有机溶剂(40)中稳定,一种仅在pH 6.5以下的水性介质中稳定(41),另一种(42)在室温下仅短时间稳定,分解为稳定的自由基。这些类似物均未产生MAO催化的自由基,但41是较差的底物(Km = 0.2mM; k(cat)= 0.034 min-1),39是混合抑制剂(Ki = 26.5 mM)。尽管该方法似乎