Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
J Am Chem Soc. 2023 Jul 26;145(29):16176-16185. doi: 10.1021/jacs.3c04870. Epub 2023 Jul 11.
In nature and synthetic chemistry, stereoselective [2 + 1] cyclopropanation is the most prevalent strategy for the synthesis of chiral cyclopropanes, a class of key pharmacophores in pharmaceuticals and bioactive natural products. One of the most extensively studied reactions in the organic chemist's arsenal, stereoselective [2 + 1] cyclopropanation, largely relies on the use of stereodefined olefins, which can require elaborate laboratory synthesis or tedious separation to ensure high stereoselectivity. Here, we report engineered hemoproteins derived from a bacterial cytochrome P450 that catalyze the synthesis of chiral 1,2,3-polysubstituted cyclopropanes, regardless of the stereopurity of the olefin substrates used. Cytochrome P450 variant P411-INC-5185 exclusively converts ()-enol acetates to enantio- and diastereoenriched cyclopropanes and in the model reaction delivers a leftover ()-enol acetate with 98% stereopurity, using whole cells. P411-INC-5185 was further engineered with a single mutation to enable the biotransformation of ()-enol acetates to α-branched ketones with high levels of enantioselectivity while simultaneously catalyzing the cyclopropanation of ()-enol acetates with excellent activities and selectivities. We conducted docking studies and molecular dynamics simulations to understand how active-site residues distinguish between the substrate isomers and enable the enzyme to perform these distinct transformations with such high selectivities. Computational studies suggest the observed enantio- and diastereoselectivities are achieved through a stepwise pathway. These biotransformations streamline the synthesis of chiral 1,2,3-polysubstituted cyclopropanes from readily available mixtures of (/)-olefins, adding a new dimension to classical cyclopropanation methods.
在自然和合成化学中，立体选择性 [2 + 1] 环丙烷化是合成手性环丙烷的最常见策略，手性环丙烷是药物和生物活性天然产物中一类关键药效团。立体选择性 [2 + 1] 环丙烷化是有机化学家武器库中研究最广泛的反应之一，主要依赖于使用立体定义明确的烯烃，这可能需要精心的实验室合成或繁琐的分离来确保高立体选择性。在这里，我们报告了源自细菌细胞色素 P450 的工程化血红素蛋白，它们可以催化手性 1,2,3-多取代环丙烷的合成，而与所用烯烃底物的立体纯度无关。细胞色素 P450 变体 P411-INC-5185 专一地将 ()-烯醇乙酸酯转化为对映体和非对映体丰富的环丙烷，并且在模型反应中使用全细胞以 98%的立体纯度留下剩余的 ()-烯醇乙酸酯。P411-INC-5185 进一步通过单点突变进行工程改造，从而能够在手性选择性高的情况下将 ()-烯醇乙酸酯生物转化为α-支链酮，同时以优异的活性和选择性催化 ()-烯醇乙酸酯的环丙烷化。我们进行了对接研究和分子动力学模拟，以了解活性位点残基如何区分底物异构体并使酶以如此高的选择性执行这些不同的转化。计算研究表明，观察到的对映体和非对映体选择性是通过逐步途径实现的。这些生物转化从易得的 (/)-烯烃混合物中简化了手性 1,2,3-多取代环丙烷的合成，为经典的环丙烷化方法增添了新的维度。
