Ras‐related protein RalA is a member of the Ras small GTPases superfamily. Its activation plays an important role in regulating tumor initiation, invasion, migration, and metastasis. In this study, we designed a new type of RalA inhibitor containing a dihydro‐α‐carboline scaffold. The structurally new dihydro‐α‐carboline derivatives could be efficiently synthesized in good yields through a newly developed three‐component [3+2+1] cyclization reaction. Evaluation of the biological activity showed that some of the dihydro‐α‐carboline derivatives can inhibit RalA/B and proliferative activities of NSCLC cell lines. The 4‐(pyridin‐3‐yl)‐dihydro‐α‐carboline compound (3 o) was found to be the most potent derivative, with IC₅₀ values of 0.43±0.03, 0.64±0.07, 0.93±0.10, and 1.54±0.15 μM against A549, H1299, H460, and H1975 cells, respectively. Mechanism investigation suggested that 3 o inhibits the RalA/B activation of A549, down‐regulates Bcl‐2, stimulates cytochrome c and PARP cleavage, and induces cell apoptosis. A molecular docking study revealed that 3 o can form stable hydrogen bonds with residues of RalA. Moreover, amide‐π and alkyl‐π interactions also contributed to the affinity between 3 o and RalA.

中文翻译：

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含有二氢-α-咔啉支架的 RalA 抑制剂的设计和有效合成

Ras 相关蛋白 RalA 是 Ras 小 GTPases 超家族的成员。它的激活在调节肿瘤的发生、侵袭、迁移和转移中起重要作用。在这项研究中，我们设计了一种含有二氢-α-咔啉支架的新型 RalA 抑制剂。通过新开发的三组分 [3+2+1] 环化反应，可以以良好的收率有效地合成结构新的二氢-α-咔啉衍生物。生物活性评估表明，一些二氢-α-咔啉衍生物可以抑制非小细胞肺癌细胞系的 RalA/B 和增殖活性。4-(pyridin-3-yl)-二氢-α-咔啉化合物 ( 3 o ) 被发现是最有效的衍生物，IC ₅₀对 A549、H1299、H460 和 H1975 细胞的值分别为 0.43±0.03、0.64±0.07、0.93±0.10 和 1.54±0.15 μM。机制研究表明，3 o抑制 A549 的 RalA/B 活化，下调 Bcl-2，刺激细胞色素c和 PARP 裂解，并诱导细胞凋亡。分子对接研究表明3 o可以与 RalA 的残基形成稳定的氢键。此外，酰胺-π 和烷基-π 相互作用也有助于3 o和 RalA之间的亲和力。