Photomicellar Catalyzed Synthesis of Amides from Isocyanides: Optimization, Scope, and NMR Studies of Photocatalyst/Surfactant Interactions

The merging of micellar and photoredox catalysis represents a key issue to promote “in water” photochemical transformations. A photomicellar catalyzed synthesis of amides from N-methyl-N-alkyl aromatic amines and both aliphatic and aromatic isocyanides is herein presented. The mild reaction conditions enabled a wide substrate scope and a good functional groups tolerance, as further shown in the late-stage functionalization of complex bioactive scaffolds. Furthermore, solution 1D and 2D NMR experiments performed, for the first time, in the presence of paramagnetic probes enabled the study of the reaction environment at the atomic level along with the localization of the photocatalyst with respect to the micelles, thus providing experimental data to drive the identification of optimum photocatalyst/surfactant pairing

Boosting Effect of 2‑Phenylquinoline Efflux Inhibitors in Combination with Macrolides against Mycobacterium smegmatis and Mycobacterium avium

The identification of efflux inhibitors to be used as adjuvants alongside existing drug regimens could have a tremendous value in the treatment of any mycobacterial infection. Here, we investigated the ability of four 2-(4′-propoxyphenyl)­quinoline Staphylococcus aureus NorA efflux inhibitors (<b>1</b>–<b>4</b>) to reduce the efflux activity in Mycobacterium smegmatis and Mycobacterium avium strains. All four compounds were able to inhibit efflux pumps in both mycobacterial species; in particular, <i>O</i>-ethylpiperazinyl derivative <b>2</b> showed an efflux inhibitory activity comparable to that of verapamil, the most potent mycobacterial efflux inhibitor reported to date, and was able to significantly reduce the MIC values of macrolides against different <i>M. avium</i> strains. The contribution of the <i>M. avium</i> efflux pumps MAV_1406 and MAV_1695 to clarithromycin resistance was proved because they were found to be overexpressed in two <i>M. avium</i> 104 isogenic strains showing high-level clarithromycin resistance. These results indicated a correlation between increased expression of efflux pumps, increased efflux, macrolide resistance, and reduction of resistance by efflux pump inhibitors such as compound <b>2</b>. Additionally, compound <b>2</b> showed synergistic activity with clarithromycin, at a concentration below the cytotoxicity threshold, in an ex vivo experiment against <i>M. avium</i> 104-infected macrophages. In summary, the 2-(4′-propoxyphenyl)­quinoline scaffold is suitable to obtain compounds endowed with good efflux pump inhibitory activity against both <i>S. aureus</i> and nontuberculous mycobacteria

Natural Compounds Inhibit SARS-CoV‑2 nsp13 Unwinding and ATPase Enzyme Activities

SARS-CoV-2 infection is still spreading worldwide, and new antiviral therapies are an urgent need to complement the approved vaccine preparations. SARS-CoV-2 nps13 helicase is a validated drug target participating in the viral replication complex and possessing two associated activities: RNA unwinding and 5′-triphosphatase. In the search of SARS-CoV-2 direct antiviral agents, we established biochemical assays for both SARS-CoV-2 nps13-associated enzyme activities and screened both in silico and in vitro a small in-house library of natural compounds. Myricetin, quercetin, kaempferol, and flavanone were found to inhibit the SARS-CoV-2 nps13 unwinding activity at nanomolar concentrations, while licoflavone C was shown to block both SARS-CoV-2 nps13 activities at micromolar concentrations. Mode of action studies showed that all compounds are nsp13 noncompetitive inhibitors versus ATP, while computational studies suggested that they can bind both nucleotide and 5′-RNA nsp13 binding sites, with licoflavone C showing a unique pattern of interaction with nsp13 amino acid residues. Overall, we report for the first time natural flavonoids as selective inhibitors of SARS-CoV-2 nps13 helicase with low micromolar activity

2‑Phenylquinoline <i>S. aureus</i> NorA Efflux Pump Inhibitors: Evaluation of the Importance of Methoxy Group Introduction

Antimicrobial resistance (AMR) represents a hot topic in drug discovery. Besides the identification of new antibiotics, the use of nonantibiotic molecules to block resistance mechanisms is a powerful alternative. Bacterial efflux pumps exert an early step in AMR development by allowing bacteria to grow at subinhibitorial drug concentrations. Thus, efflux pump inhibitors (EPIs) offer a great opportunity to fight AMR. Given our experience in developing Staphylococcus aureus NorA EPIs, in this work, starting from the 2-phenylquinoline hit 1, we planned the introduction of methoxy groups on the basis of their presence in known NorA EPIs. Among the 35 different synthesized derivatives, compounds 3b and 7d exhibited the best NorA inhibition activity by restoring at very low concentrations ciprofloxacin MICs against resistant S. aureus strains. Interestingly, both compounds displayed EPI activities at nontoxic concentrations for human cells as well as highlighted promising results by preliminary pharmacokinetic studies

Pyridobenzothiazolones Exert Potent Anti-Dengue Activity by Hampering Multiple Functions of NS5 Polymerase

Treatment of dengue virus (DENV) and other flavivirus infections is an unmet medical need. The highly conserved flaviviral NS5 RNA-dependent RNA polymerase (RdRp) is an attractive antiviral target that interacts with NS3 and viral RNA within the replication complex assembly. Biochemical and cell-based evidence indicate that targeting cavity B may lead to dual RdRp and NS5–NS3 interaction inhibitors. By ligand-based design around 1H-pyrido­[2,1-b]­[1,3]­benzothiazol-1-one (PBTZ) 1, we identified new potent and selective DENV inhibitors that exert dual inhibition of NS5 RdRp and NS3–NS5 interaction, likely through binding cavity B. Resistance studies with compound 4 generated sequence variants in the 3′-untranslated region of RNA while further biochemical experiments demonstrated its ability to block also RNA-NS5 interaction, required for correct RNA synthesis in cells. These findings shed light on the potential mechanism of action for this class of compounds, underlying how PBTZs are very promising lead candidates for further evaluation

New Pyrazolobenzothiazine Derivatives as Hepatitis C Virus NS5B Polymerase Palm Site I Inhibitors

We have previously identified the pyrazolobenzothiazine scaffold as a promising chemotype against hepatitis C virus (HCV) NS5B polymerase, a validated and promising anti-HCV target. Herein we describe the design, synthesis, enzymatic, and cellular characterization of new pyrazolobenzothiazines as anti-HCV inhibitors. The binding site for a representative derivative was mapped to NS5B palm site I employing a mutant counterscreen assay, thus validating our previous in silico predictions. Derivative <b>2b</b> proved to be the best selective anti-HCV derivative within the new series, exhibiting a IC₅₀ of 7.9 μM against NS5B polymerase and antiviral effect (EC₅₀ = 8.1 μM; EC₉₀ = 23.3 μM) coupled with the absence of any antimetabolic effect (CC₅₀ > 224 μM; SI > 28) in a cell based HCV replicon system assay. Significantly, microscopic analysis showed that, unlike the parent compounds, derivative <b>2b</b> did not show any significant cell morphological alterations. Furthermore, since most of the pyrazolobenzothiazines tested altered cell morphology, this undesired aspect was further investigated by exploring possible perturbation of lipid metabolism during compound treatment