Recent Advances in the Development of Sulfamoyl-Based Hepatitis B Virus Nucleocapsid Assembly Modulators.

Hepatitis B virus (HBV) is the primary contributor to severe liver ailments, encompassing conditions such as cirrhosis and hepatocellular carcinoma. Globally, 257 million people are affected by HBV annually and 887,000 deaths are attributed to it, representing a substantial health burden. Regrettably, none of the existing therapies for chronic hepatitis B (CHB) have achieved satisfactory clinical cure rates. This issue stems from the existence of covalently closed circular DNA (cccDNA), which is difficult to eliminate from the nucleus of infected hepatocytes. HBV genetic material is composed of partially double-stranded DNA that forms complexes with viral polymerase inside an icosahedral capsid composed of a dimeric core protein. The HBV core protein, consisting of 183 to 185 amino acids, plays integral roles in multiple essential functions within the HBV replication process. In this review, we describe the effects of sulfamoyl-based carboxamide capsid assembly modulators (CAMs) on capsid assembly, which can suppress HBV replication and disrupt the production of new cccDNA. We present research on classical, first-generation sulfamoyl benzocarboxamide CAMs, elucidating their structural composition and antiviral efficacy. Additionally, we explore newly identified sulfamoyl-based CAMs, including sulfamoyl bicyclic carboxamides, sulfamoyl aromatic heterocyclic carboxamides, sulfamoyl aliphatic heterocyclic carboxamides, cyclic sulfonamides, and non-carboxamide sulfomoyl-based CAMs. We believe that certain molecules derived from sulfamoyl groups have the potential to be developed into essential components of a well-suited combination therapy, ultimately yielding superior clinical efficacy outcomes in the future.

Discovery and synthesis of 1,2,4-oxadiazole derivatives as novel inhibitors of Zika, dengue, Japanese encephalitis, and classical swine fever virus infections.

Zika virus (ZIKV), an arbovirus of the Flaviviridae family, has emerged as a significant public health concern owing to its association with congenital abnormalities and severe neurological sequelae. Thus, there is an urgent need to develop effective therapeutic approaches to efficiently treat ZIKV infections. This study used phenotypic screening to identify a series of 1,2,4-oxadiazole derivatives that possess antiviral activity against ZIKV infection. Subsequently, 28 new derivatives were designed, synthesized, and evaluated for this purpose. Among these compounds, 4-(5-phenyl-1,2,4-oxadiazol-3-yl)-N-(pyridin-3-ylmethyl)aniline (5d) had potent antiviral activity against ZIKV infections. Furthermore, a structure-activity relationship analysis indicated that a benzyl substitution on the aniline nitrogen of this compound improved potency while augmenting its drug-like properties. In addition, 5d exhibited antiviral activity against various viruses of Flaviviridae family of worldwide public health importance, such as dengue, Japanese encephalitis and classical swine fever viruses, indicating its potential as a lead compound for generating 1,2,4-oxadiazole derivatives with broad-spectrum anti-flaviviral properties.

The efficacy of a 2,4-diaminoquinazoline compound as an intranasal vaccine adjuvant to protect against influenza A virus infection in vivo.

Adjuvants are substances added to vaccines to enhance antigen-specific immune responses or to protect antigens from rapid elimination. As pattern recognition receptors, Toll-like receptors 7 (TLR7) and 8 (TLR8) activate the innate immune system by sensing endosomal single-stranded RNA of RNA viruses. Here, we investigated if a 2,4-diaminoquinazoline-based TLR7/8 agonist, (S)-3-((2-amino-8-fluoroquinazolin-4-yl)amino)hexan-1-ol (named compound 31), could be used as an adjuvant to enhance the serological and mucosal immunity of an inactivated influenza A virus vaccine. The compound induced the production of proinflammatory cytokines in macrophages. In a dose-response analysis, intranasal administration of 1 µg compound 31 together with an inactivated vaccine (0.5 µg) to mice not only enhanced virus-specific IgG and IgA production but also neutralized influenza A virus with statistical significance. Notably, in a virus-challenge model, the combination of the vaccine and compound 31 alleviated viral infection-mediated loss of body weight and increased survival rates by 40% compared with vaccine only-treated mice. We suggest that compound 31 is a promising lead compound for developing mucosal vaccine adjuvants to protect against respiratory RNA viruses such as influenza viruses and potentially coronaviruses.

Development of Potent Immune Modulators Targeting Stimulator of Interferon Genes Receptor.

Stimulator of interferon genes (STING) is an endoplasmic reticulum-membrane protein that plays important roles in cancer immunotherapy by activating innate immune responses. We designed and synthesized STING modulators and characterized compounds 4a and 4c that share a crucial amidobenzimidazole moiety. In vitro STING binding and cell-based activity assays demonstrated the potency and efficacy of the compounds that function as direct STING agonists by stimulating STING downstream signaling and promoting type I interferon immune responses. In vitro metabolic studies and the pharmacokinetic properties of the compounds led us to investigate their anticancer activity in an in vivo syngeneic model. Intravenous injection of compounds 4a and 4c significantly decreased tumor volume in a CT26 murine colorectal carcinoma model, and the immunological memory-derived cancer inhibition was observed in 4c-treated mouse models. The present results suggest the therapeutic potential of the compounds for cancer immunotherapy via STING-mediated immune activation.

Sulfamoylbenzamide-based Capsid Assembly Modulators for Selective Inhibition of Hepatitis B Viral Replication.

As the spread of infections caused by hepatitis B virus (HBV) threatens public health worldwide, investigations from multiple perspectives and of various mechanisms of action are urgently required to increase the HBV cure rate. Targeting the encapsidation of the nuclear capsid protein (core protein, HBc) has emerged as an attractive strategy for inhibiting the viral assembly process; however, a drug targeting this mechanism has not yet been approved. We synthesized novel sulfamoylbenzamides (SBAs) as capsid assembly modulators of HBV and found that the effects and safety profiles of compounds 3 and 8 have potential therapeutic applicability against HBV. The formation of tubular particles was time-dependent in the presence of 3, indicating a new mode of protein assembly by SBA compounds. Our findings provide a new entity for developing safe and efficient treatments for HBV infection.

C-H Methylation of Iminoamido Heterocycles with Sulfur Ylides*.

The direct methylation of N-heterocycles is an important transformation for the advancement of pharmaceuticals, agrochemicals, functional materials, and other chemical entities. Herein, the unprecedented C(sp2 )-H methylation of iminoamido heterocycles as nucleoside base analogues is described. Notably, trimethylsulfoxonium salt was employed as a methylating agent under aqueous conditions. A wide substrate scope and excellent level of functional-group tolerance were attained. Moreover, this method can be readily applied to the site-selective methylation of azauracil nucleosides. The feasibility of gram-scale reactions and various transformations of the products highlight the synthetic potential of the developed method. Combined deuterium-labeling experiments aided the elucidation of a plausible reaction mechanism.

Discovery of a New Sulfonamide Hepatitis B Capsid Assembly Modulator.

Hepatitis B virus (HBV) remains a major health concern with 260 million people having been infected globally, and approximately 680,000 deaths have occurred annually from cirrhosis and liver cancer. The modulation of HBV capsid assembly has emerged as a promising therapeutic approach for curing chronic HBV infection. Small-molecule capsid assembly modulators (CAMs) can broadly be classified as heteroaryldihydropyrimidines and sulfamoylbenzamides (SBAs). SBAs are capsid activators that inhibit viral replication by achieving capsid assembly before polymerase encapsulation. Herein, we report a novel series of HBV CAMs based on NVR 3-778, a potent CAM belonging to the SBA class. The lead compound (KR-26556) exhibited improved pharmacological activity and was examined through molecular docking studies.

Visible-Light-Mediated Photoredox-Catalyzed Regio- and Stereoselective Chlorosulfonylation of Alkynes.

Herein, a one-step chlorosulfonylation of alkynes via a photocatalytic redox process is described. A variety of commercially available sulfonyl chlorides can be applied for the generation of sulfonyl radical species under visible-light irradiation. Regio- and stereoselective addition of the sulfonyl radical and chloride leads to the efficient formation of ( E)-selective ß-chlorovinyl sulfones from a broad range of terminal and internal alkynes. The reported method represents an operationally simple and mild way to furnish vinyl sulfones.

Novel tacrine-pyridinium hybrid reactivators of organophosphorus-inhibited acetylcholinesterase: Synthesis, molecular docking, and in vitro reactivation study.

First-line medical treatment against nerve agents consists of co-administration of anticholinergic agents and oxime reactivators, which reactivate inhibited AChE. Pralidoxime, a commonly used oxime reactivator, is effective against some nerve agents but not against others; thus, new oxime reactivators are needed. Novel tacrine-pyridinium hybrid reactivators in which 4-pyridinealdoxime derivatives are connected to tacrine moieties by linear carbon chains of different lengths (C2-C7) were prepared (Scheme 1, 5a-f). Their binding affinities to electric eel AChE were tested because oximes can inhibit free AChE, and the highest AChE activity (95%, 92%, and 90%) was observed at 1 µM concentrations of the oximes (5a, 5b, and 5c, respectively). Based on their inhibitory affinities towards free AChE, 1 µM concentrations of the oxime derivatives (5) were used to examine reactivation of paraoxon-inhibited AChE. Reactivation ability increased as the carbon linker chains lengthened (n = 2-5), and 5c and 5d showed remarkable reactivation ability (41%) compared to that of 2-PAM (16%) and HI-6 (4%) against paraoxon-inhibited electric eel AChE at 1 µM concentrations. Molecular docking simulation showed that the most stable binding free energy was observed in 5c at 73.79 kcal⋅mol-1, and the binding mode of 5c is acceptable for the oxygen atom of oximate to attack the phosphorus atom of paraoxon and reactivate paraoxon-inhibited eel AChE model structure.

Reductive C2-Alkylation of Pyridine and Quinoline N-Oxides Using Wittig Reagents.

The ability to alkylate pyridines and quinolines is important for their further development as pharmaceuticals and agrochemicals, and for other purposes. Herein we describe the unprecedented reductive alkylation of pyridine and quinoline N-oxides using Wittig reagents. A wide range of pyridine and quinoline N-oxides were converted into C2-alkylated pyridines and quinolines with excellent site selectivity and functional-group compatibility. Sequential C-H functionalization reactions of pyridine and quinoline N-oxides highlight the utility of the developed method. Detailed labeling experiments were performed to elucidate the mechanism of this process.

3-Aryl-1,2,4-oxadiazole Derivatives Active Against Human Rhinovirus.

The human rhinovirus (hRV) is the causative agent of the common cold that often aggravates respiratory complications in patients with asthma or chronic obstructive pulmonary disease. The high rate of mutations and variety of serotypes are limiting the development of anti-hRV drugs, which emphasizes the need for the discovery of novel lead compounds. Previously, we identified antiviral compound 1 that we used here as the starting material for developing a novel compound series with high efficacy against hRV-A and -B. Improved metabolic stability was achieved by substituting an ester moiety with a 1,2,4-oxadiazole group. Specifically, compound 3k exhibited a high efficacy against hRV-B14, hRV-A21, and hRV-A71, with EC50 values of 66.0, 22.0, and 3.7 nM, respectively, and a relevant hepatic stability (59.6 and 40.7% compound remaining after 30 min in rat and human liver microsomes, respectively). An in vivo study demonstrated that 3k possessed a desirable pharmacokinetic profile with low systemic clearance (0.158 L·h-1·kg-1) and modest oral bioavailability (27.8%). Hence, 3k appears to be an interesting candidate for the development of antiviral lead compounds.

Photoredox-Catalyzed Trifluoromethylative Intramolecular Cyclization: Synthesis of CF3-Containing Heterocyclic Compounds.

A general photoredox-catalyzed intramolecular cyclization was developed for the synthesis of trifluoromethylated heterocyclic compounds. The reaction proceeded smoothly under mild photocatalytic conditions with high functional group tolerance, allowing the preparation of oxygen-, sulfur-, or nitrogen-containing heterocycles of different sizes. The broad substrate scope demonstrated the complexity-building potential of the strategy.

Multicomponent Oxidative Trifluoromethylation of Alkynes with Photoredox Catalysis: Synthesis of α-Trifluoromethyl Ketones.

The direct oxidative addition of CF3 and H2O to alkynes was achieved with photoredox catalysis to obtain α-trifluoromethyl ketones via rapid enol-keto tautomerization. The reaction exhibits high functional group tolerance and regioselectivity. Heterocycles of various sizes containing CF3 were synthesized from the α-CF3-substituted diketones obtained through the protocol, thereby demonstrating the versatile applicability of the method. Mechanistic studies of the reaction with isotopes provided insight into the reaction pathway.

A Novel Series of Highly Potent Small Molecule Inhibitors of Rhinovirus Replication.

Human rhinoviruses (hRVs) are the main causative pathogen for common colds and are associated with the exacerbation of asthma. The wide variety in hRV serotypes has complicated the development of rhinovirus replication inhibitors. In the current investigation, we developed a novel series of benzothiophene derivatives and their analogues (6-8) that potently inhibit the replication of both hRV-A and hRV-B strains. Compound 6g inhibited the replication of hRV-B14, A21, and A71, with respective EC50 values of 0.083, 0.078, and 0.015 µM. The results of a time-of-addition study against hRV-B14 and hRV-A16 and resistant mutation analysis on hRV-B14 implied that 6g acts at the early stage of the viral replication process, interacting with viral capsid protein. A molecular docking study suggested that 6g has a capsid-binding mode similar to that of pleconaril. Finally, derivatives of 6 also displayed significant inhibition against poliovirus 3 (PV3) replication, implying their potential inhibitory activities against other enterovirus species.

Synthesis and Anti-inflammatory Evaluation of 2-Aminobenzaldehydes via Ir(III)-Catalyzed C-H Amidation of Aldimines with Acyl Azides.

The aldimine-directed C-H amidation of various arenes with N-acyl azides as amidation surrogates under cationic iridium(III) catalysis is described. This transformation efficiently provides a range of 2-aminobenzaldehyde derivatives with excellent site selectivity and functional group compatibility. The resulting 2-aminobenzaldehyde framework provides facile access to a range of biologically interesting heterocycles. In addition, all synthetic compounds were screened for anti-inflammatory activity against interleukin-1ß (IL-1ß) and tumor necrosis factor alpha (TNF-α) with lipopolysaccharide (LPS)-induced RAW264.7 cells. Generally, a range of ortho-amidated benzaldehydes displayed promising inhibitory activity against IL-1ß and TNF-α compared to dexamethasone as a positive control. Notably, compounds (3ae and 4ac) were found to exhibit potent anti-inflammatory activity stronger than that of dexamethasone.

Stereoselective Photoredox-Catalyzed Chlorotrifluoromethylation of Alkynes: Synthesis of Tetrasubstituted Alkenes.

A new photoredox-catalyzed chlorotrifluoromethylation reaction of internal arylalkynes under mild conditions using visible light has been developed. The reactions proceed with high levels of regio- and stereoselectivity and utilize commercially available CF3SO2Cl as both the CF3 and Cl source. In the mechanistic pathway for this process, generation of the CF3 radical and chloride ion occurs by Ir(ppy)3-photocatalyzed reductive decomposition of CF3SO2Cl. The synthetically important trifluoromethyl-substituted vinyl chlorides produced in this process can be readily transformed to 1,1-bis-arylalkenes by using Suzuki coupling.

Antiviral activity of KR-23502 targeting nuclear export of influenza B virus ribonucleoproteins.

The spiro compound 5,6-dimethyl-3H,3'H-spiro(benzofuran-2,1'-isobenzofuran)-3,3'-dione (KR-23502) has antiviral activity against influenza A and more potently B viruses. The aim of this study is to elucidate its mechanism of action. Subcellular localization and time-course expression of influenza B viral proteins, nucleoprotein (NP) and matrix protein 1 (M1), showed that KR-23502 reduced their amounts within 5 h post-infection. Early steps of virus life cycle, including virus entry, nuclear localization of NP and viral RNA-dependent RNA replication, were not affected by KR-23502. Instead it interrupted a later event corresponding to nuclear export of NP and M1 proteins. Delivery of viral ribonucleoprotein (vRNP)-M1 complex has been known to be mediated by the viral nuclear export protein (NEP) through interaction with cellular chromosomal maintenance 1 (CRM1) protein. In this study, we experimentally demonstrated that the compound targets the nuclear export of vRNP. Moreover, a single mutation (aspartate to glycine) at amino acid position 54 in M1 [M1(D54G)] was detected after 18 passages in the presence of KR-23502 with a 2-fold increase in 50% effective concentration indicating that this compound has a relatively high genetic barrier to resistance. Interestingly, it was observed that proteasome-mediated degradation of M1(D54G) was attenuated by KR-23502. In conclusion, we suggest that KR-23502 shows its anti-influenza activity by downregulating NEP/CRM1-mediated nuclear export of influenza vRNP and M1. KR-23502 provides a core chemical skeleton for further structure-based design of novel antivirals against influenza viruses.

Synthesis and anti-influenza virus activity of 4-oxo- or thioxo-4,5-dihydrofuro[3,4-c]pyridin-3(1H)-ones.

A target-free approach was applied to discover anti-influenza viral compounds, where influenza infected Madin-Darby canine kidney cells were treated 7500 different small organic chemicals individually and reduction of virus-induced cytopathic effect was measured. One of the hit compounds was (Z)-1-((5-fluoro-1H-indol-3-yl)methylene)-6-methyl-4-thioxo-4,5-dihydrofuro[3,4-c]pyridin-3(1H)-one (15a) with half-maximal effective concentrations of 17.4-21.1µM against influenza A/H1N1, A/H3N2 and B viruses without any cellular toxicity at 900µM. To investigate the structure-activity relationships, two dozens of the hit analogs were synthesized. Among them, 15g, 15j, 15q, 15s, 15t and 15x had anti-influenza viral activity comparable or superior to that of the initial hit. The anti-influenza viral compounds efficiently suppressed not only viral protein level of the infected cells but also production of viral progeny in the culture supernatants in a dose-dependent manner. Based on a mode-of-action study, they did not affect virus entry or RNA replication. Instead, they suppressed viral neuraminidase activity. This study is the first to demonstrate that dihydrofuropyridinones could serve as lead compounds for the discovery of alternative influenza virus inhibitors.

Vicinal difunctionalization of alkenes: chlorotrifluoromethylation with CF3SO2Cl by photoredox catalysis.

Photoredox-catalyzed vicinal chlorotrifluoromethylation of alkene is described. In the presence of Ru(Phen)3Cl2, CF3SO2Cl was used as a source for the CF3 radical and chloride ion under visible light irradiation. Various terminal and internal alkenes were transformed to their vicinal chlorotrifluoromethylated derivatives. Biologically active compounds were applied under the condition to obtain desired products, suggesting that the method could be feasible for late-stage modification in drug discovery.

Efficient synthesis of 3H,3'H-spiro[benzofuran-2,1'-isobenzofuran]-3,3'-dione as novel skeletons specifically for influenza virus type B inhibition.

An efficient and novel two step synthetic procedure to prepare various substituted 3H,3'H-spiro[benzofuran-2,1'-isobenzofuran]-3,3'-diones A, was established from very simple and easily available starting materials. The developed method is a robust and general approach for the synthesis of these structures. The prepared compounds were tested against influenza virus type A viz., A/Taiwan/1/86 (H1N1), A/Hong Kong/8/68 (H3N2) and type B viz., B/Panama/45/90, B/Taiwan/2/62, B/Lee/40, B/Brisbane/60/2008. Among 31 compounds tested, some of them showed good activity (selective index values >10) against these influenza viruses preferentially for type B. The most active compound 3b showed activity in 3.0-16.1 µM range with a selectivity index value between 30 and 166 against these type B viruses, in which it was comparable to the antiviral agent favipiravir. Also, 3b is found to be inactive against other enveloped viruses (viz., HIV and HSV) showing its specificity for influenza viruses.