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A general route to several styryl-lactone frameworks is presented. Starting from a known enol ether, stereoselective epoxidation and methanolysis yields a series of three distinct hydroxyacetals, each further functionalized by etherification with an allylic vinylsilane fragment. A highly efficient Lewis acid-promoted intramolecular annulation at the tethered oxocarbenium allows direct entry to cis-fused bicyclic ether cores. Further manipulation delivers a variety of additional styryl-lactone motifs and analogs; for example, simple allylic oxidation yields 3-deoxyisoaltholactone, in just five steps overall.

Dengue is the most important mosquito-transmitted viral disease and a major global health concern. Over the last decade, dengue virus (DENV) drug discovery and development has intensified, however, this has not resulted in approved DENV-specific antiviral treatments yet. DENV and hepatitis C virus (HCV) belong to the same Flaviviridae family and, in contrast to DENV, antiviral treatments for HCV have been licensed. Therefore, applying the knowledge gained on anti-HCV drugs may foster the discovery and development of dengue antiviral drugs. Here, we screened a library of compounds with established anti-HCV activity in a DENV-2 sub-genomic replicon inhibition assay and selected compounds with single-digit micromolar activity. These compounds were advanced into a hit-to-lead medicinal chemistry program resulting in lead compound JNJ-1A, which inhibited the DENV-2 sub-genomic replicon at 0.7 μM, in the absence of cytotoxicity. In addition, JNJ-1A showed equipotent antiviral activity against DENV serotypes 1, 2, and 4. In vitro resistance selection experiments with JNJ-1A induced mutation T108I in non-structural protein 4B (NS4B), pointing towards a mechanism of action linked to this protein. Collectively, we described the discovery and characterization of a novel DENV inhibitor potentially targeting NS4B.

The novel styryl lactone analog (±)-3-deoxyisoaltholactone was synthesized in 5 steps from dihydrofuran. An intramolecular vinylsilane–oxocarbenium condensation thus afforded the central cis-fused bicyclic ether array in near quantitative yield as a single stereoisomer.

HCV NS5B polymerase, an essential and virus-specific enzyme, is an important target for drug discovery. Using structure-based design, we optimized a 1,5-benzodiazepine NS5B polymerase inhibitor chemotype into a new sulfone-containing scaffold. The design yielded potent inhibitor (S)-4c (K(D) = 0.79 nM), which has approximately 20-fold greater affinity for NS5B than its carbonyl analogue (R)-2c.

Optimization through parallel synthesis of a novel series of hepatitis C virus (HCV) NS5B polymerase inhibitors led to the identification of ( R )-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(6-methylpyridine-2-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[ b,e ][1,4]diazepin-1-one 11zc and ( R )-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(2,5-dimethyloxazol-4-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[ b,e ][1,4]diazepin-1-one 11zk as potent (replicon EC 50 = 400 nM and 270 nM, respectively) and selective (CC 50 > 20 μM) inhibitors of HCV replication. These data warrant further lead-optimization efforts.

We have developed a duplex real-time RT-PCR assay for profiling antiviral inhibitors of four dengue virus (DENV) serotypes. In this assay, the primers and the probe for amplifying DENV were designed in the conserved regions of the genome after aligned more than 300 nucleotide sequences of four dengue serotypes deposited in the GeneBank. To discriminate the antiviral activity from the cytotoxicity of compounds, a housekeeping gene of the Vero cells, β-actin, was used to design the primers and the probe for the second set of PCR as an internal control, which is used to normalize the RNA levels of dengue-specific PCR due to the cellular toxicity of test compounds. For compound profiling, the duplex PCR is performed using LightCycler(®) in a single tube to simultaneously amplify both the dengue target gene and the Vero cell housekeeping gene from the compound-treated Vero cell lysates. This assay was validated against a panel of reference compounds. The results show that the universal primers and probe in this duplex RT-PCR assay can efficiently amplify all four dengue serotypes and that the PCR efficiency for both the dengue target gene and the Vero cells β-actin gene is 100%.

The nonstructural protein 5 (NS5) of dengue virus (DENV) plays a central role in the virus replication. It functions as a methyltransferase and an RNA-dependent RNA polymerase. As such, it is a promising target for antiviral drug development. To develop a high-throughput biochemical assay for screening compound libraries, we expressed and purified the polymerase domain of the dengue NS5 protein in bacterial cells. The polymerase activity is measured using a scintillation proximity assay. This homogeneous and high--throughput assay enables screening of compound libraries for identifying polymerase inhibitors against DENV. In this chapter we describe the methods to express and purify the dengue NS5 polymerase from E. coli and a validated high-throughput enzymatic assay for screening inhibitors of NS5 polymerase.

Dengue, a mosquito-borne virus of the Flaviviridae family, is reemerging as one of the most important human pathogens in tropical and subtropical regions of the world. It is estimated that 2.5 billion people live in areas at risk for transmission of dengue virus (DENV). Furthermore, it causes significant morbidity and mortality with 50-100 million infections per year. Currently, there are no vaccines commercially available and no effective antiviral drugs for treatment of DENV infections. In this chapter, we describe a plaque reduction assay and a cell-based high-throughput antiviral assay for identifying inhibitors against DENV. The latter is a homogeneous high-throughput assay that has been fully validated according to the Food and Drug Administration (FDA) guidelines for assay validation and can be used for screening compound libraries.

Dengue, a mosquito-borne virus of the Flaviviridae family, is reemerging as one of the most important human pathogens in tropical and subtropical regions of the world. It is estimated that 2.5 billion people live in areas at risk for transmission of dengue virus (DENV). Furthermore, it causes significant morbidity and mortality with 50-100 million infections per year. Currently, there are no vaccines commercially available and no effective antiviral drugs for treatment of DENV infections. In this chapter, we describe a plaque reduction assay and a cell-based high-throughput antiviral assay for identifying inhibitors against DENV. The latter is a homogeneous high-throughput assay that has been fully validated according to the Food and Drug Administration (FDA) guidelines for assay validation and can be used for screening compound libraries.

The nonstructural protein 5 (NS5) of dengue virus (DENV) plays a central role in the virus replication. It functions as a methyltransferase and an RNA-dependent RNA polymerase. As such, it is a promising target for antiviral drug development. To develop a high-throughput biochemical assay for screening compound libraries, we expressed and purified the polymerase domain of the dengue NS5 protein in bacterial cells. The polymerase activity is measured using a scintillation proximity assay. This homogeneous and high--throughput assay enables screening of compound libraries for identifying polymerase inhibitors against DENV. In this chapter we describe the methods to express and purify the dengue NS5 polymerase from E. coli and a validated high-throughput enzymatic assay for screening inhibitors of NS5 polymerase.

We have developed a duplex real-time RT-PCR assay for profiling antiviral inhibitors of four dengue virus (DENV) serotypes. In this assay, the primers and the probe for amplifying DENV were designed in the conserved regions of the genome after aligned more than 300 nucleotide sequences of four dengue serotypes deposited in the GeneBank. To discriminate the antiviral activity from the cytotoxicity of compounds, a housekeeping gene of the Vero cells, β-actin, was used to design the primers and the probe for the second set of PCR as an internal control, which is used to normalize the RNA levels of dengue-specific PCR due to the cellular toxicity of test compounds. For compound profiling, the duplex PCR is performed using LightCycler(®) in a single tube to simultaneously amplify both the dengue target gene and the Vero cell housekeeping gene from the compound-treated Vero cell lysates. This assay was validated against a panel of reference compounds. The results show that the universal primers and probe in this duplex RT-PCR assay can efficiently amplify all four dengue serotypes and that the PCR efficiency for both the dengue target gene and the Vero cells β-actin gene is 100%.

Lewis acid-mediated intramolecular attack of vinylsilanes at tethered oxonium precursors 1 results in a rapid assembly of the cis-fused bicyclic ether species 3, with complete regio- and stereospecific control, and in some cases near-quantitative yield. Continued investigation suggests a general approach to a variety of such ether frameworks.