Development of a New Structural Class of Broadly Acting HCV Non-Nucleoside Inhibitors Leading to the Discovery of MK-8876

Rh(III)-Catalyzed Chemoselective [4 + 2] Annulations for the Synthesis of [1,3]Oxazinoindolones: A Combined Experimental and Computational Study

The interaction of N-alkoxy-1H-indole-1-carboxamides with transition metals leads to indole-fused heterocyclic scaffolds through directing group leaving/migration, [3 + 2], N-C2 [4 + 1], and [4 + 2] annulations. However, the corresponding O-C2 [4 + 2] annulation reactions have never been reported. Herein, we report the chemoselective annulation of N-alkoxy-1H-indole-1-carboxamides catalyzed by Rh(III), affording [1,3]oxazinoindolones through a hitherto unknown reaction pathway. This unprecedented C2 oxygen cyclization, rather than the known C2 nitrogen cyclization to form oxazinoindolones via five key steps, has been explained using density functional theory.

Distinct Characteristic Binding Modes of Benzofuran Core Inhibitors to Diverse Genotypes of Hepatitis C Virus NS5B Polymerase: A Molecular Simulation Study

The benzofuran core inhibitors HCV-796, BMS-929075, MK-8876, compound 2, and compound 9B exhibit good pan-genotypic activity against various genotypes of NS5B polymerase. To elucidate their mechanism of action, multiple molecular simulation methods were used to investigate the complex systems of these inhibitors binding to GT1a, 1b, 2a, and 2b NS5B polymerases. The calculation results indicated that these five inhibitors can not only interact with the residues in the palm II subdomain of NS5B polymerase, but also with the residues in the palm I subdomain or the palm I/III overlap region. Interestingly, the binding of inhibitors with longer substituents at the C5 position (BMS-929075, MK-8876, compound 2, and compound 9B) to the GT1a and 2b NS5B polymerases exhibits different binding patterns compared to the binding to the GT1b and 2a NS5B polymerases. The interactions between the para-fluorophenyl groups at the C2 positions of the inhibitors and the residues at the binding pockets, together with the interactions between the substituents at the C5 positions and the residues at the reverse β-fold (residues 441-456), play a key role in recognition and the induction of the binding. The relevant studies could provide valuable information for further research and development of novel anti-HCV benzofuran core pan-genotypic inhibitors.

[RhCp*Cl2]2-Catalyzed Indole Functionalization: Synthesis of Bioinspired Indole-Fused Polycycles

Polycyclic fused indoles are ubiquitous in natural products and pharmaceuticals due to their immense structural diversity and biological inference, making them suitable for charting broader chemical space. Indole-based polycycles continue to be fascinating as well as challenging targets for synthetic fabrication because of their characteristic structural frameworks possessing biologically intriguing compounds of both natural and synthetic origin. As a result, an assortment of new chemical processes and catalytic routes has been established to provide unified access to these skeletons in a very efficient and selective manner. Transition-metal-catalyzed processes, in particular from rhodium(III), are widely used in synthetic endeavors to increase molecular complexity efficiently. In recent years, this has resulted in significant progress in reaching molecular scaffolds with enormous biological activity based on core indole skeletons. Additionally, Rh(III)-catalyzed direct C-H functionalization and benzannulation protocols of indole moieties were one of the most alluring synthetic techniques to generate indole-fused polycyclic molecules efficiently. This review sheds light on recent developments toward synthesizing fused indoles by cascade annulation methods using Rh(III)-[RhCp*Cl2]2-catalyzed pathways, which align with the comprehensive and sophisticated developments in the field of Rh(III)-catalyzed indole functionalization. Here, we looked at a few intriguing cascade-based synthetic designs catalyzed by Rh(III) that produced elaborate frameworks inspired by indole bioactivity. The review also strongly emphasizes mechanistic insights for reaching 1-2, 2-3, and 3-4-fused indole systems, focusing on Rh(III)-catalyzed routes. With an emphasis on synthetic efficiency and product diversity, synthetic methods of chosen polycyclic carbocycles and heterocycles with at least three fused, bridged, or spiro cages are reviewed. The newly created synthesis concepts or toolkits for accessing diazepine, indol-ones, carbazoles, and benzo-indoles, as well as illustrative privileged synthetic techniques, are included in the featured collection.

Small molecule NS5B RdRp non-nucleoside inhibitors for the treatment of HCV infection: A medicinal chemistry perspective

Hepatitis C virus (HCV) infection has become a global health problem with enormous risks. Nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase (RdRp) is a component of HCV, which can promote the formation of the viral RNA replication complex and is also an essential part of the replication complex itself. It plays a vital role in the synthesis of the positive and negative strands of HCV RNA. Therefore, the development of small-molecule inhibitors targeting NS5B RdRp is of great value for treating HCV infection-related diseases. Compared with NS5B RdRp nucleoside inhibitors, non-nucleoside inhibitors have more flexible structures, simpler mechanisms of action, and more predictable efficacy and safety of drugs in humans. Technological advances over the past decade have led to remarkable achievements in developing NS5B RdRp inhibitors. This review will summarize the non-nucleoside inhibitors targeting NS5B RdRp developed in the past decade and describe their structure optimization process and structure-activity relationship.

Recent advancement in small molecules as HCV inhibitors

Hepatitis C virus (HCV) has caused a considerable threat to human health. To date, no treatments are without side effects. The proteins and RNA associated with HCV have specific functions during the viral life cycle. The vulnerabilities to virus are associated with those proteins or RNA. Thus, targeting these proteins and RNA is an efficient strategy to develop anti-HCV therapeutics. The treatment for HCV-infected patients has been greatly improved after the approval of direct-acting antivirals (DAAs). However, the cost of DAAs is unusually high, which adds to the economic burden on patients with chronic liver diseases. So far, many efforts have been devoted to the development of small molecules as novel HCV inhibitors. Investigations on the inhibitory activities of these small molecules have involved the target identification and the mechanism of action. In this mini-review, these small molecules divided into four kinds were elaborated, which focused on their targets and structural features. Furthermore, we raised the current challenges and promising prospects. This mini-review may facilitate the development of small molecules with improved activities targeting HCV based on the chemical scaffolds of HCV inhibitors.

Synthesis of Indole-Fused Six-, Seven-, or Eight-Membered N,O-Heterocycles via Rhodium-Catalyzed NH-Indole-Directed C-H Acetoxylation/Hydrolysis/Annulation

We report herein the facile synthesis of indole-fused six-, seven-, or eight-membered N,O-heterocycles through rhodium-catalyzed C-H acetoxylation/hydrolysis/annulation. The notable features of this method include C-H acetoxylation using NH-indole as the intrinsic directing group, high functional group compatibility, and construction of indole-fused medium-sized rings.

Rh(III)-Catalyzed Chemodivergent Annulations between Indoles and Iodonium Carbenes: A Rapid Access to Tricyclic and Tetracyclic N-Heterocylces

Herein, we report an acid-controlled highly tunable selectivity of Rh(III)-catalyzed [4 + 2] and [3 + 3] annulations of N-carboxamide indoles with iodonium ylides lead to form synthetically important tricyclic and tetracyclic N-heterocycles. Here, iodonium ylide serves as a carbene precursor. The protocol proceeds under operationally simple conditions and provides novel tricyclic and tetracyclic scaffolds such as 3,4-dihydroindolo[1,2-c]quinazoline-1,6(2H,5H)-dione and 1H-[1,3]oxazino[3,4-a]indol-1-one derivatives with a broad range of functional group tolerance and moderate to excellent yields. Furthermore, the protocol synthetic utility was extended for various chemical transformations and was easily scaled up to a large-scale level.

Multi-step parallel synthesis enabled optimization of benzofuran derivatives as pan-genotypic non-nucleoside inhibitors of HCV NS5B

In a lead optimization effort towards NS5B NNI inhibitors, two multi-step parallel libraries were designed and successfully synthesized. Through this effort we discovered compound 9B, which achieved rigorous and delicate balance of inhibition across the common genotypes and mutants with <10 nM potency. In addition, the bicyclic compounds 9B exhibited improved FASSIF solubility over the tetracyclic compound MK-8876. This strategic approach demonstrated that, even within limited reaction scope, multi-step parallel libraries could provide access to more complex chemical space. This expedient access facilitates diverse, purpose-driven optimization of SAR and physicochemical properties.

A review on HCV inhibitors: Significance of non-structural polyproteins

Hepatitis C virus (HCV) mortality and morbidity is a world health misery with an approximate 130–150 million chronically HCV tainted and suffering individuals and it initiate critical liver malfunction like cirrhosis, hepatocellular carcinoma or liver HCV cancer. HCV NS5B protein one of the best studied therapeutic target for the identification of new drug candidates to be added to the combination or multiple combination medication recently approved. During the past few years, NS5B has thus been an important object of attractive medicinal chemistry endeavors, which induced to the surfacing of betrothal preclinical drug molecules. In this scenario, the current review set limit to discuss research published on NS5B and few other therapeutic functional inhibitors concentrating on hit investigation, hit to lead optimization, ADME parameters evaluation, and the SAR data which was out for each compound type and similarity taken into consideration. The discussion outlined in this specific review will surly helpful and vital tool for those medicinal chemists investigators working with HCV research programs mainly pointing on NS5B and set broad spectrum identification of creative anti HCV compounds. This mini review also tells each and every individual compound ability related how much they are active against NS5B and few other targets.

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Hepatitis C infection causes severe liver cirrhosis and carcinoma.

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The new acute HCV infections are raising every year and mortality rate become serious concern.

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The plausible list of anti-HCV drugs and clinical agents were listed in this review.

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The divergent medicinal scaffolds as anti-HCV agents were presented as per their targets.

Design and evaluation of novel tetracyclic benzofurans as palm site allosteric inhibitors of HCV NS5B polymerase

Hepatitis C virus (HCV) NS5B polymerase is a prime target for the development of direct-acting antiviral drugs for the treatment of chronic HCV infection. Several novel and potent HCV NS5B non-nucleoside inhibitors with unique tetracyclic bezonfuran-based structures were prepared and evaluated. Similar to clinical developmental compound MK-8876, N-linked (compounds 1 and 2) and C-linked (compounds 3 and 4) tetracyclic structures maintained broad spectrum anti-replicon potency profiles and demonstrated moderate to excellent oral bioavailability and pharmacokinetic parameters across the three preclinical animal species. To better understand the importance of tetracyclic structures related to pan genotypic potency profiles especially against clinically relevant GT1a variants, the teracycles with different ring size were prepared and in vitro evaluations suggested compounds with six number ring have better overall potency profiles.

Polymerase assays for lead discovery: An overall review of methodologies and approaches

Polymerases represent an attractive molecular target for antibacterial drug development, antiviral intervention and cancer therapy. Over the past decade, academic groups and scientists from pharmaceutical industry have developed a large plethora of different functional assays to monitor the enzymatic reaction catalyzed by polymerases. These assays were used to enable high-throughput screening (HTS) for lead discovery purposes, as well as hit-to-lead (H2L) drug profiling activities. In both cases the choice of the assay technology is critical and to the best of our knowledge, there is no review available to help scientists to choose the most suitable assay. This review summarizes the most common functional assays developed to monitor the enzymatic activity of polymerases and discusses the advantages and disadvantages of each assay. Assays are presented and evaluated in term of cost, ease of use, high-throughput screening compatibility and liability towards delivering false positives and false negatives.