Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 80126 Naples, Italy.
Department of Physics "Ettore Pancini", University of Naples Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 80126 Naples, Italy.
J Inorg Biochem. 2023 Sep;246:112298. doi: 10.1016/j.jinorgbio.2023.112298. Epub 2023 Jun 21.
Over the last decades, much effort has been devoted to the construction of protein and peptide-based metalloporphyrin catalysts capable of promoting difficult transformations with high selectivity. In this context, mechanistic studies are fundamental to elucidate all the factors that contribute to catalytic performances and product selectivity. In our previous work, we selected the synthetic peptide-porphyrin conjugate MnMC6a as a proficient catalyst for indole oxidation, promoting the formation of a 3-oxindole derivative with unprecedented selectivity. In this work, we have evaluated the role of the metal ion in affecting reaction outcome, by replacing manganese with iron in the MC6a scaffold. Even though product selectivity is not altered upon metal substitution, FeMC6*a shows a lower substrate conversion and prolonged reaction times with respect to its manganese analogue. Experimental and theoretical studies have enabled us to delineate the reaction free energy profiles for both catalysts, indicating different thermodynamic limiting steps, depending on the nature of the metal ion.
在过去的几十年中，人们投入了大量的精力来构建基于蛋白质和肽的金属卟啉催化剂，以实现高选择性地促进困难转化。在这种情况下，对反应机理的研究对于阐明所有有助于催化性能和产物选择性的因素至关重要。在我们之前的工作中，我们选择了合成的肽-卟啉缀合物 MnMC6a 作为吲哚氧化的有效催化剂，促进了具有前所未有的选择性的 3-氧吲哚衍生物的形成。在这项工作中，我们通过在 MC6a 支架中用铁取代锰来评估金属离子在影响反应结果中的作用。尽管金属取代后产物选择性没有改变，但 FeMC6*a 的底物转化率较低，反应时间也比其锰类似物长。实验和理论研究使我们能够描绘出两种催化剂的反应自由能曲线，表明根据金属离子的性质，存在不同的热力学限制步骤。
