多杀菌素A生物合成中的动态复杂[6+4]和[4+2]环加成反应。
Dynamically Complex [6+4] and [4+2] Cycloadditions in the Biosynthesis of Spinosyn A.
作者信息
Patel Ashay, Chen Zhuo, Yang Zhongyue, Gutiérrez Osvaldo, Liu Hung-wen, Houk K N, Singleton Daniel A
机构信息
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States.
Department of Chemistry, Texas A & M University , College Station, Texas 77843-3255, United States.
出版信息
J Am Chem Soc. 2016 Mar 23;138(11):3631-4. doi: 10.1021/jacs.6b00017. Epub 2016 Mar 9.
SpnF, an enzyme involved in the biosynthesis of spinosyn A, catalyzes a transannular Diels-Alder reaction. Quantum mechanical computations and dynamic simulations now show that this cycloaddition is not well described as either a concerted or stepwise process, and dynamical effects influence the identity and timing of bond formation. The transition state for the reaction is ambimodal and leads directly to both the observed Diels-Alder and an unobserved [6+4] cycloadduct. The potential energy surface bifurcates and the cycloadditions occur by dynamically stepwise modes featuring an "entropic intermediate". A rapid Cope rearrangement converts the [6+4] adduct into the observed [4+2] adduct. Control of nonstatistical dynamical effects may serve as another way by which enzymes control reactions.
SpnF是一种参与多杀菌素A生物合成的酶，催化分子内环Diels-Alder反应。量子力学计算和动力学模拟表明，这种环加成反应既不能很好地描述为协同过程，也不能很好地描述为分步过程，动力学效应会影响键形成的特性和时机。该反应的过渡态是双峰的，直接导致观察到的Diels-Alder环加成产物和未观察到的[6+4]环加成产物。势能面发生分支，环加成反应通过具有“熵中间体”的动态分步模式发生。快速的Cope重排将[6+4]加合物转化为观察到的[4+2]加合物。控制非统计动力学效应可能是酶控制反应的另一种方式。
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