Functional Synthetic Models of Cu-dependent Monooxygenases

项目总结： 在这个研究项目中，我们开发了人工合成的无机铜配合物，以了解 依赖铜的单加氧酶的结构和功能方面。这些金属酶含有 1或2个铜离子在其活性中心，它们通过 瞬变CuN/O2物种的形成。我们对研究单核细胞的反应性特别感兴趣。 被认为是强C-H羟化反应中活性氧化剂的铜/氧中间体 微粒甲烷单加氧酶(PMMOS)和裂解多糖等酶的键 单加氧酶(LPMO)。关于活性铜/氧物种身份的许多问题仍然存在 未回答，包括：i)铜的氧化态(CuI与CuII对CuIII)；ii)O2的还原/质子化状态 (O2−，(H)O22−，(H)O2−)和与这些铜/氧物种相关的pKa和氧化还原电位；III)机理 通过它，铜/氧中间体进行C-H羟化反应(例如，O-O裂解机理在之前或之后 C-H氧化？；在底物羟化之前生成高价铜氧物种？)在这项研究中 建议，我们使用两种不同的方法来解决这个问题： 1)我们利用含有C-H底物共价连接到其结构上的配体支架(L)(底物- 配体)，使我们能够产生和表征Lcu/O2物种，并评估它们对 分子内C-H羟基化。底物-配体的修饰将使我们能够：i)评估 Cu/O2物种氧化sp3 C-H键和sp2 C-H键；ii)控制化合物的立体电子性质 通过使用不同的配体给体(即N_2，N_3，N_4)来生成铜配合物，这将导致 单核和双核Lcu/O2物种，并分析它们对分子内C-H的反应性 羟化作用，包括反应中间产物的表征、动力学和计算；iii)利用 开发合成方案以促进具有挑战性的有机化合物的方法(铜定向羟基化) 不对称C-H羟基化和一锅法合成1，3-恶嗪等转化反应。 2)我们合成了含有氧化还原活性配体的单核铜配合物，其氢键可调，可以稳定 铜-羟基和铜-氧基核。这些不同寻常的铜络合物能够通过 金属和/或配体支架的氧化。这些高价CuO(H)核的特征是 光谱方法及其执行生物悬浮分子间2E−C-H羟基化的能力将是 使用Bordwell方程(即具有较高氧化还原电位和较高pKa的物种)进行了系统研究 应该能够氧化更强的C-H键)，动力学实验和反应产物的分析 衍生于羟基化(例如，有机产物(S)和最终铜配合物的氧化/质子化状态)。 总体而言，这些研究将有助于更广泛地理解铜离子参与的生物化学作用。 氧还原和生物相关的氧化作用。

Project Summary: In this research project, we develop synthetic inorganic copper complexes to understand the fundamental aspects of structure and function in Cu-dependent monooxygenase enzymes. These metalloenzymes contain 1 or 2 Cu ions in their active center and they couple the reduction of O2 with the oxidation of substrates via formation of transient Cun/O2 species. We are particularly interested in studying the reactivity of mononuclear Cu/O2 intermediates since they have been proposed as active oxidants in the hydroxylation of strong C-H bonds in enzymes such as particulate methane monooxygenases (pMMOs) and lytic polysaccharide monooxygenases (LPMOs). Many questions concerning the identity of the active Cu/O2 species remain unanswered, including: i) oxidation state of Cu (CuI vs. CuII vs. CuIII); ii) reduction/protonation state of O2 (O2−,(H)O22−, (H)O2−) and the pKa and redox potentials associated with these Cu/O2 species; iii) mechanism by which the Cu/O2 intermediates carry out C-H hydroxylations (e.g. O-O cleavage mechanism before or after C-H oxidation?; generation of high-valent Cu-oxyl species before substrate hydroxylation?). In this research proposal, we tackle this problem using two different approaches: 1) We utilize ligand scaffolds (L) that contain C-H substrates covalently attached to their structure (substrate- ligands) that permit us to generate and characterize LCu/O2 species and evaluate their reactivity towards intramolecular C-H hydroxylation. Substrate-ligand modifications will permit us to: i) evaluate the ability of the Cu/O2 species to oxidize sp3 C-H bonds and sp2 C-H bonds; ii) control the stereo-electronic properties of the Cu complexes by the use of different ligand donors (i.e. N2, N3, N4) that will lead to the generation of mononuclear and dinuclear LCu/O2 species, and analyze their reactivity towards intramolecular C-H hydroxylation including characterization of reaction intermediates, kinetics and computations; iii) utilize this approach (Cu-directed hydroxylations) to develop synthetic protocols to promote challenging organic transformations such as enantioselective C-H hydroxylations and one-pot synthesis of 1,3-oxazines. 2) We synthesize mononuclear Cu complexes bearing redox-active ligands with tunable H-bonds that stabilize Cu-hydroxo and Cu-oxyl cores. These unusual Cu complexes are able to reach multiple oxidation states via oxidation of the metal and/or ligand scaffold. These high-valent CuO(H) cores will be characterized by various spectroscopic methods and their ability to perform biorelevant intermolecular 2e− C-H hydroxylations will be examined systematically using the Bordwell equation (i.e. species with higher redox potential and higher pKa should be capable of oxidizing stronger C-H bonds), kinetic experiments and analysis of the reactions products derived from hydroxylation (e.g. organic product(s) and oxidation/protonation state of the final Cu complexes). Overall, these studies will contribute to a broader understanding of the biochemical role of Cu ions involved in O2 reduction and biologically relevant oxidations.