Synthesis and Biological Evaluation of Umifenovir Analogues as Anti‐SARS‐CoV‐2 Agents

Abstract

The unprecedented novel coronavirus disease 2019 (COVID‐19) pandemic is a threat to global health and the economy. Since the outbreak of COVID‐19, great effort has been made to reposition existing drugs to shorten development timelines, in addition to vaccine development and drug discovery campaigns. Umifenovir is a broad‐spectrum antiviral agent used to treat influenza in China and Russia and is currently undergoing clinical trials for the treatment of COVID‐19. In this article, the synthesis of umifenovir analogues and their biological evaluation are reported. The inhibitory activities of analogues against the binding of the spike glycoprotein (S‐protein) of the novel severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) to the ACE2 receptor, which is a possible mode of action for umifenovir to inhibit viral infection, were investigated.

Synthesis and Cell‐Based Evaluation of Umifenovir Analogues as Anti‐SARS‐CoV‐2 Agents

“…It was also noted that the aminomethyl moieties at the 4‐position of the indole, which were also present in the structure of 1 , did not affect the antiviral activity. From another perspective, the 4‐position of the indole can accommodate hydrophilic substituents for managing the physicochemical properties of the compound, such as its solubility, as precipitation was observed at higher concentrations (>20 μM) for some analogues in our previous report [23] …”

“…From another perspective, the 4-position of the indole can accommodate hydrophilic substituents for managing the physicochemical properties of the compound, such as its solubility, as precipitation was observed at higher concentrations (> 20 μM) for some analogues in our previous report. [23] Scheme 1. Synthesis of umifenovir analogues with replacement of the substituents at the 2-and 4-positions of the indole.…”

“…The synthesis of the umifenovir analogues was performed according to a previously reported synthetic scheme ( Scheme 1). [23] The phenolic hydroxyl group of the commercially available ethyl‐5‐hydroxy‐2‐methylindole‐3‐carboxylate ( 21 ) was protected with an acetyl group using acetic anhydride to obtain acetyl indole 22 in 92 % yield. Then, N ‐methylation of 22 provided tetrasubstituted indole 23 in 93 % yield, which was followed by bromination of the C2 methyl and C6 using N ‐bromosuccinimide and benzoyl peroxide to provide bis‐bromoindole 24 in 78 % yield.…”

“…Purification by silica gel column chromatography (hexane/EtOAc = 3 : 2) afforded 22 as a white solid (1.09 g, 4.18 mmol, 92 %); R f 0.31 (hexane/EtOAc = 3 : 2); 1 H NMR (500 MHz, CDCl 3 ) δ 8.30 (1H, brs, NH), 7.77 (1H, d, J = 2.2 Hz, H4), 7.25 (1H, d, J = 8.6 Hz, H7), 6.91 (1H, dd, J = 8.6, 2.2 Hz, H6), 4.38 (2H, q, J = 7.2 Hz, CO 2 CH 2 CH 3 ), 2.73 (3H, s, C 1 CH 3 ), 2.33 (3H, s, CO 2 CH 3 ), 1.43 (3H, t, J = 7.2 Hz, CO 2 CH 2 CH 3 ). (23) [28] Compound 22 (1.20 g, 4.60 mmol, 1.0 equiv) was dissolved in DMF (15 mL). To this solution, methyl iodide (0.890 mL, 13.8 mmol, 3.0 equiv) was added, and the resulting mixture was cooled on ice.…”

“…Despite the fact that 1 has been studied as a treatment for COVID‐19, there has been no reported systematic structure‐activity relationship (SAR) study of the compound to date. We previously reported the synthesis of novel umifenovir analogues and their biological evaluation with a focus on their inhibitory activity against the binding of the S‐protein of SARS‐CoV‐2 and the angiotensin‐converting enzyme 2 (ACE2) receptor, which is a possible mode of action of 1 for inhibiting viral infection; however, no strong inhibitory activity was observed from these analogues [23] . Thus, the detailed molecular mode of action of 1 remains unclear, and studies using other assay systems are needed to elucidate the biological activity of umifenovir analogues.…”