Design, synthesis and anticancer activity of β-carboline based pseudo-natural products by inhibiting AKT/mTOR signaling pathway.

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and remains the leading cause of cancer deaths. Much progress has been made to treat NSCLC, however, only limited patients can benefit from current treatments. Thus, more efforts are needed to pursue novel molecular modalities for NSCLC treatment. It was demonstrated that pseudo-natural products (PNP) are a critical source for antitumor drug discovery. Herein, we describe a CH activation protocol for the expedient construction of a focused library utilizing the PNP rational design strategy. This protocol features a rhodium-catalyzed CH activation/ [4+2] annulation reaction between N-OAc-indole-2-carboxamide and alkynyl quinols, enabling facile access to diverse quinol substituted β-carboline derivatives (31 examples). The anticancer activities were assessed in vitro against NSCLC cell line A549, yielding a potent antiproliferative β-carboline derivative (8r) with an IC value of 0.8 ± 0.1 µM. Further investigation revealed that this compound could decrease the expression of Caspase 3, and increase the expression of autophagic protein Cyclin B1, thus markedly inducing autophagy and apoptosis. Mechanistic study suggested that 8r could be a potent anti-NSCLC agent through the AKT/mTOR signaling pathway in A549 cells. Moreover, the anticancer activities were also assessed against three other cancer cell lines, and 8r exhibits a broader inhibitory effect on cell proliferation in all cancer cell lines tested. These results indicated that carboline-based PNPs show great potential to induce cell autophagy and apoptosis, which serve as good leads for further drug discovery.