The main protease (M^pro, 3CL^pro) of SARS-CoV-2 is an attractive target in coronaviruses because of its crucial involvement in viral replication and transcription. Here, we report on the design, synthesis, and structure–activity relationships of novel small-molecule thioesters as SARS-CoV-2 M^pro inhibitors. Compounds 3w and 3x exhibited excellent SARS-CoV-2 M^pro inhibition with k_inac/K_i of 58,700 M^–1 s^–1 (K_i = 0.0141 μM) and 27,200 M^–1 s^–1 (K_i = 0.0332 μM), respectively. In Calu-3 and Vero76 cells, compounds 3h, 3i, 3l, 3r, 3v, 3w, and 3x displayed antiviral activity in the nanomolar range without host cell toxicity. Co-crystallization of 3w and 3af with SARS-CoV-2 M^pro was accomplished, and the X-ray structures showed covalent binding with the catalytic Cys145 residue of the protease. The potent SARS-CoV-2 Mpro inhibitors also inhibited the M^pro of other beta-coronaviruses, including SARS-CoV-1 and MERS-CoV, indicating that they might be useful to treat a broader range of coronaviral infections.

中文翻译：

---

小分子硫酯作为 SARS-CoV-2 主要蛋白酶抑制剂：酶抑制、构效关系、抗病毒活性和 X 射线结构测定

SARS-CoV-2 的主要蛋白酶（M ^pro、 3CL ^pro）是冠状病毒中一个有吸引力的靶点，因为它在病毒复制和转录中发挥着至关重要的作用。^{在这里，我们报告了作为 SARS-CoV-2 M前}抑制剂的新型小分子硫酯的设计、合成和构效关系。化合物3w和3x表现出优异的 SARS-CoV-2 M ^pro抑制作用，k _inac / K _i分别为 58,700 M ^–1 s ^–1 ( K _i = 0.0141 μM) 和 27,200 M ^–1 s ^–1 ( K _i = 0.0332 μM) ， 分别。在 Calu-3 和 Vero76 细胞中，化合物3h、3i 、 3l、3r、3v、3w和3x显示纳摩尔范围内的抗病毒活性，且没有宿主细胞毒性。完成了3w和3af与 SARS-CoV-2 M ^pro的共结晶，X 射线结构显示与蛋白酶的催化 Cys145 残基共价结合。有效的 SARS-CoV-2 Mpro 抑制剂还可以抑制其他 β 冠状病毒（包括 SARS-CoV-1 和 MERS-CoV）的M ^{pro ，这表明它们可能可用于治疗更广泛的冠状病毒感染。}