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Bifunctional Catalysis by Natural Cinchona Alkaloids:A Mechanism Explained

机译：天然金鸡纳生物碱的双功能催化作用：机理解释

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摘要

The use of bifunctional chiral catalysts, which are able to simultaneously bind and activate two reacting partners, currently represents an efficient and reliable strategy for the stereoselective preparation of valuable chiral compounds. Cinchona alkaloids such as quinine and quinidine, simple organic molecules generously provided by Nature, were the first compounds to be proposed to operate through a cooperative catalysis. To date, a full mechanistic characterization of the dual catalysis mode of cinchona alkaloids has proven a challenging objective, due to the transient, non-covalent nature of the involved catalyst–substrate interactions. Here, we propose a mechanistic rationale on how natural cinchona alkaloids act as efficient bifunctional catalysts by using a broad range of computational methods, including classical molecular dynamics, a mixed quantum mechanical/molecular mechanics (QM/MM) approach, and correlated ab-initio calculations. We also unravel the origin of enantio- and diastereoselectivity, which is due to a specific network of hydrogen bonds that stabilize the transition state of the rate-determining step. The results are validated by experimental evidence.
机译：目前，能够同时结合并激活两个反应伙伴的双功能手性催化剂的使用代表了一种有效和可靠的策略，用于立体选择性地制备有价值的手性化合物。金鸡纳生物碱（例如奎宁和奎尼丁）是自然界慷慨提供的简单有机分子，是第一个被提议通过协同催化作用的化合物。迄今为止，由于所涉及的催化剂-底物相互作用的瞬时，非共价性质，金鸡纳生物碱双重催化模式的完整机理表征已证明是一个具有挑战性的目标。在这里，我们提出了一种机械原理，通过使用包括经典分子动力学，混合量子力学/分子力学（QM / MM）方法以及相关的从头算在内的多种计算方法，天然金鸡纳生物碱如何充当有效的双功能催化剂。计算。我们还揭示了对映选择性和非对映选择性的起源，这是由于特定的氢键网络稳定了速率确定步骤的过渡状态。实验结果验证了结果。

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