Synthesis of Trifluoromethyl‐α,β‐unsaturated Lactones and Pyrazolinones and Discovery of Influenza Virus Polymerase Inhibitors

Abstract

To explore the potential biological activities of trifluoromethyl heterocycles, we recently developed a synthetic approach to access a series of α-trifluoromethyl-α,β-unsaturated lactones and trifluoromethyl pyrazolinones. The compounds were tested for their antimicrobial activity, and we found that some compounds had anti-influenza viral activity. The β-aryl-α-trifluoromethyl α,β-unsaturated lactone derivatives 5 g (5-(4-chlorophenyl)-5-methyl-4-phenyl-3-(trifluoromethyl)furan-2-one), 7 b (4-(4-methoxyphenyl)-3-(trifluoromethyl)spiro[furan-5,1'-indane]-2-one), and the trifluoromethyl pyrazolinone 12 c (1-(6-methoxy-2-naphthyl)-2-(trifluoromethyl)-5,6,7,8-tetrahydropyrazolo[1,2-a]pyridazin-3-one) were found to possess promising inhibitory activity against influenza virus type A, strain A/WSN/33 (H1N1). These three hit compounds were successfully optimized, and we identified that the most potent compound 5 h (5-(4-chlorophenyl)-4-(6-methoxy-2-naphthyl)-5-methyl-3-(trifluoromethyl)furan-2-one) showed inhibitory activity against various types of influenza A and B viruses in the low-micromolar range without showing cytotoxicity. Moreover, 5 h was more effective against the clinical isolate A/California/7/2009 (H1N1pdm) strain than the influenza viral polymerase inhibitor, favipiravir (T-705). We also delineated the structure-activity relationship and obtained mechanistic insight into inhibition of the viral polymerase.

Lead Optimization of Influenza Virus RNA Polymerase Inhibitors Targeting PA–PB1 Interaction

“…To explore the inhibitory effects of compounds 89, 100, and 118 against RdRp activity, we performed a transcription assay (Figure 3). 46 293T cells were co-transfected with plasmids expressing RdRp and a viral genome expressing plasmid (pPolI/NP(0)GFP(0)) encoding fluorescent protein (green fluorescent protein, GFP), as a reporter. The viral genome RNA encoding GFP gene is transcribed from pPolI/ NP(0)GFP(0) by cellular RNA polymerase I (polI) and then GFP gene is transcribed by viral RdRp.…”

“…These cells were maintained at 37 °C in an atmosphere of 5% CO 2 . Influenza viruses A/WSN/33 (H1N1), A/Puerto Rico/8/34 (H1N1), A/Virginia/ATCC2/2009 (H1N1), A/Aichi/2/68 (H3N2), and B/Lee/40 were prepared as described . Allantoic fluid from embryonated eggs of A/California/7/2009 (H1N1) was obtained from Dr. Hiroshi Kido (Tokushima University).…”

Challenges Based on Antiplasmodial and Antiviral Activities of 7‐Chloro‐4‐aminoquinoline Derivatives

“…The anti-influenza virus activities of the compounds were evaluated by CV staining as described previously with some modifications. [42,47] To evaluate anti-influenza virus activity, MDCK cells were seeded into 96-well plates at a density of 3.0 × 10 4 cells/well in 100 μL of MEM containing 5 % FBS and then incubated overnight. The cells were washed with MEM vitamin solution, 100 μL of each serially diluted compound were added, and then cells were infected with 100 μL of virus solution in MEM vitamin solution at a concentration equivalent to the median tissue culture infectious dose for A/WSN/ 33.…”

A Quinolinone Compound Inhibiting the Oligomerization of Nucleoprotein of Influenza A Virus Prevents the Selection of Escape Mutants

“…The viral transcription assay was performed as previously described [27]. Briefly, 293T cells were seeded into 24-well plates at a density of 2 × 10 5 cells/well and incubated overnight.…”