Chemoenzymatic cascade catalysis has emerged as a revolutionary tool for streamlining traditional retrosynthetic disconnections, creating new possibilities for the asymmetric synthesis of valuable chiral compounds. Here we construct a one-pot concurrent chemoenzymatic cascade by integrating organobismuth-catalyzed aldol condensation with ene-reductase (ER)-catalyzed enantioselective reduction, enabling the formal asymmetric α-benzylation of cyclic ketones. To achieve this, we develop a pair of enantiocomplementary ERs capable of reducing α-arylidene cyclic ketones, lactams, and lactones. Our engineered mutants exhibit significantly higher activity, up to 37-fold, and broader substrate specificity compared to the parent enzyme. The key to success is due to the well-tuned hydride attack distance/angle and, more importantly, to the synergistic proton-delivery triade of Tyr28-Tyr69-Tyr169. Molecular docking and density functional theory (DFT) studies provide important insights into the bioreduction mechanisms. Furthermore, we demonstrate the synthetic utility of the best mutants in the asymmetric synthesis of several key chiral synthons.

化学酶级联催化已成为简化传统逆合成断开的革命性工具，为有价值的手性化合物的不对称合成创造了新的可能性。在这里，我们通过整合有机铋催化的羟醛缩合与烯还原酶（ER）催化的对映选择性还原来构建一锅并发化学酶级联，从而实现环酮的正式不对称α-苄基化。为了实现这一目标，我们开发了一对能够还原 α-亚芳基环酮、内酰胺和内酯的对映互补 ER。与亲本酶相比，我们的工程突变体表现出显着更高的活性（高达 37 倍）和更广泛的底物特异性。成功的关键在于精心调整的氢化物攻击距离/角度，更重要的是，Tyr28-Tyr69-Tyr169 的协同质子传递三联体。分子对接和密度泛函理论（DFT）研究为生物还原机制提供了重要的见解。此外，我们证明了最佳突变体在几个关键手性合成子的不对称合成中的合成效用。