Convenient and general synthesis of C-3 substituted het(aryl)indole C-nucleoside analogues from sugar alkynes

The synthesis of C-3 substituted het(aryl)indole C-nucleoside analogues bearing structurally diverse sugar moieties has been achieved by Sonogashira coupling of terminal sugar alkynes and het(aryl) iodides followed by heteroannulation of the corresponding sugar/het(aryl) alkynes with substituted 2-iodoanilines. This method is simple and general, and is suitable for structurally diverse sugars and various het(aryl) iodides. The terminal sugar alkynes include furanosides, pyranosides, and acyclic sugars with sensitive groups and bulky substituents. The het(aryl) iodides involve iodobenzene, iodothiophene, iodobenzothiophene, and iodobenzofuran. 31 examples have been given and the corresponding 2-het(aryl)indole C-nucleoside analogues are obtained in moderate to excellent yields.

Quadrol-Pd(II) complexes: phosphine-free precatalysts for the room-temperature Suzuki-Miyaura synthesis of nucleoside analogues in aqueous media

Commercially available Quadrol, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (THPEN), has been used for the first time as N^N- donor neutral hydrophilic ligand in the synthesis and characterization of new water soluble palladium (II) complexes...

The Valproic Acid Derivative Valpromide Inhibits Pseudorabies Virus Infection in Swine Epithelial and Mouse Neuroblastoma Cell Lines

Pseudorabies virus (PRV) infection of swine can produce Aujeszky’s disease, which causes neurological, respiratory, and reproductive symptoms, leading to significant economic losses in the swine industry. Although humans are not the natural hosts of PRV, cases of human encephalitis and endophthalmitis caused by PRV infection have been reported between animals and workers. Currently, a lack of specific treatments and the emergence of new PRV strains against which existing vaccines do not protect makes the search for effective antiviral drugs essential. As an alternative to traditional nucleoside analogues such as acyclovir (ACV), we studied the antiviral effect of valpromide (VPD), a compound derived from valproic acid, against PRV infection in the PK15 swine cell line and the neuroblastoma cell line Neuro-2a. First, the cytotoxicity of ACV and VPD in cells was compared, demonstrating that neither compound was cytotoxic at a specific concentration range after 24 h exposure. Furthermore, the lack of direct virucidal effect of VPD outside of an infected cell environment was demonstrated. Finally, VPD was shown to have an antiviral effect on the viral production of two strains of pseudorabies virus (wild type NIA-3 and recombinant PRV-XGF) at the concentrations ranging from 0.5 to 1.5 mM, suggesting that VPD could be a suitable alternative to nucleoside analogues as an antiherpetic drug against Aujeszky’s disease.

Design and Synthesis of Antiviral Iminoribitol C-Nucleosides

<p>Infections caused by RNA viruses, such as Ebola and Zika, continue to exist worldwide as significant public health problems. In response to the urgent need for safer and more efficacious treatment options to treat infections caused by RNA viruses, the pharmaceutical and biotechnology industries have devoted significant efforts over the last two decades to discovering and developing new antiviral agents. One such antiviral, Sofosbuvir®, was approved by the US Federal Drug Administration (FDA) in 2014 and has revolutionized the treatment of Hepatitis-C. Sofosbuvir® was the second largest selling drug in the world in 2016 and in just twenty-one months Gilead reported sales worth $26.6 billion USD.The strategy of using nucleoside analogues to inhibit viral RNA dependent RNA polymerase(RdRp)has been pursued since the 1970s, and exemplified bythe discovery and development of ribavirin. The natural substrates of RNA polymerases are nucleoside triphosphates and often the efficacy of nucleoside analogues as antivirals are dependent on their ability to be converted by the host or virus to mono-, di-, and ultimately tri-phosphate analogues which block the active site of RNA polymerase as an analogue of the substrate causing chain termination. Recently Biocryst Pharmaceuticals (Biocryst) described the anti-viral properties of Immucillin-A (Galidesivir), an iminoribitol based nucleoside analogue, which was found to have broad spectrum antiviral activity especially against RNA viruses including Ebola. Researchers at the Ferrier Research Institute (Ferrier) have synthesizedan analogue of Immucillin-A, 8-aza-Immucillin-A (AIA) which shows comparable activityto Immucillin-A, in anti-viral screens against Ebola, and this antiviral activity forms part of a US patent application. The Ferrier is keen to further exemplify this compound class through the synthesis of analogues of both Immucillin-A and AIA as well as improve the overall synthesis of the lead compound AIA.Included as part of this study is the synthesis of pro-drugs of these iminoribitol based nucleoside analogues. Prodrugs are metabolized inside the body and are often converted to the corresponding pharmacologically active form. In general, prodrug strategies have improved the bioavailability and efficacy of many drugs. In particular, prodrugs strategies involving nucleoside analogue antivirals, which target RNA polymerase, have been particularly effective as they ensure conversion to the monophosphate in vivo. Conversion to the 5’-monophosphate form of a nucleoside analogue is the rate limiting step to the inhibition of the RNA polymerase –prior to its conversion to the triphosphateanalogue. The prodrug is effectively a protected monophosphate, and is then readily converted to monophosphate by the host and then onto the di-and tri-phosphate by kinases in both the host and virus. ProTide prodrugs, such as Sofosbuvir® provide a verified strategy for improving anti-viral activity and hence our desire to synthesize pro-drugs of all our iminoribitol based nucleoside analogues. This research thesis also involved repeating the known synthesis of the Immucillins, in particular, Immucillin-H (Forodesine), which requires in excess of 20 linear synthetic steps to make. The linear synthetic route to Immucillin-H was used instead of the more convenient convergent method developed by the Ferrier as several key synthetic intermediates in this progress were utilized in the attempted synthesis of some of the planned nucleoside analogues of AIA. As part of this work the candidate learned aspects of scaling up chemical reactions andthe critical analysis of both reaction hazards and reagent compatibilities at scale. Where possible and given the number of synthetic steps involved the candidate was also interested in improving the yields of the building blocks involved in the synthesis of the Immucillins with limited success.</p>

Design and Synthesis of Antiviral Iminoribitol C-Nucleosides

<p>Infections caused by RNA viruses, such as Ebola and Zika, continue to exist worldwide as significant public health problems. In response to the urgent need for safer and more efficacious treatment options to treat infections caused by RNA viruses, the pharmaceutical and biotechnology industries have devoted significant efforts over the last two decades to discovering and developing new antiviral agents. One such antiviral, Sofosbuvir®, was approved by the US Federal Drug Administration (FDA) in 2014 and has revolutionized the treatment of Hepatitis-C. Sofosbuvir® was the second largest selling drug in the world in 2016 and in just twenty-one months Gilead reported sales worth $26.6 billion USD.The strategy of using nucleoside analogues to inhibit viral RNA dependent RNA polymerase(RdRp)has been pursued since the 1970s, and exemplified bythe discovery and development of ribavirin. The natural substrates of RNA polymerases are nucleoside triphosphates and often the efficacy of nucleoside analogues as antivirals are dependent on their ability to be converted by the host or virus to mono-, di-, and ultimately tri-phosphate analogues which block the active site of RNA polymerase as an analogue of the substrate causing chain termination. Recently Biocryst Pharmaceuticals (Biocryst) described the anti-viral properties of Immucillin-A (Galidesivir), an iminoribitol based nucleoside analogue, which was found to have broad spectrum antiviral activity especially against RNA viruses including Ebola. Researchers at the Ferrier Research Institute (Ferrier) have synthesizedan analogue of Immucillin-A, 8-aza-Immucillin-A (AIA) which shows comparable activityto Immucillin-A, in anti-viral screens against Ebola, and this antiviral activity forms part of a US patent application. The Ferrier is keen to further exemplify this compound class through the synthesis of analogues of both Immucillin-A and AIA as well as improve the overall synthesis of the lead compound AIA.Included as part of this study is the synthesis of pro-drugs of these iminoribitol based nucleoside analogues. Prodrugs are metabolized inside the body and are often converted to the corresponding pharmacologically active form. In general, prodrug strategies have improved the bioavailability and efficacy of many drugs. In particular, prodrugs strategies involving nucleoside analogue antivirals, which target RNA polymerase, have been particularly effective as they ensure conversion to the monophosphate in vivo. Conversion to the 5’-monophosphate form of a nucleoside analogue is the rate limiting step to the inhibition of the RNA polymerase –prior to its conversion to the triphosphateanalogue. The prodrug is effectively a protected monophosphate, and is then readily converted to monophosphate by the host and then onto the di-and tri-phosphate by kinases in both the host and virus. ProTide prodrugs, such as Sofosbuvir® provide a verified strategy for improving anti-viral activity and hence our desire to synthesize pro-drugs of all our iminoribitol based nucleoside analogues. This research thesis also involved repeating the known synthesis of the Immucillins, in particular, Immucillin-H (Forodesine), which requires in excess of 20 linear synthetic steps to make. The linear synthetic route to Immucillin-H was used instead of the more convenient convergent method developed by the Ferrier as several key synthetic intermediates in this progress were utilized in the attempted synthesis of some of the planned nucleoside analogues of AIA. As part of this work the candidate learned aspects of scaling up chemical reactions andthe critical analysis of both reaction hazards and reagent compatibilities at scale. Where possible and given the number of synthetic steps involved the candidate was also interested in improving the yields of the building blocks involved in the synthesis of the Immucillins with limited success.</p>

Targeting Metabolic Vulnerabilities in Primary Effusion Lymphoma Using the Novel Nucleoside Analog 6-Eti

Although nucleoside analogues have been used effectively in the clinic for the treatment of a wide range of hematological malignancies, lack of response to currently available nucleoside analogues and drug resistance limit their utility. A rare but highly aggressive cancer is primary effusion lymphoma (PEL). Through high throughput screening, we have discovered a novel nucleoside analog, called 6-ethylthioinosine (6-ETI) as a potent and selective inhibitor of PEL, with little activity in other lymphomas tested. PEL is a rare B-cell non-Hodgkin's lymphoma characterized by lymphomatous effusions in body cavities. It is associated with Kaposi's sarcoma herpesvirus (KSHV/HHV-8) infection and occurs mainly in immunocompromised patients. PEL is known to frequently be resistant to conventional chemotherapy (CHOP and EPOCH) resulting in poor prognosis and a rather incurable disease. Our studies demonstrated that 6-ETI is a pro-drug activated by adenosine kinase (ADK), an enzyme that is overexpressed in PEL cell lines and primary PEL specimens, as well as other plasma cell malignancies, including plasmablastic lymphoma (PBL) and multiple myeloma (MM). The latter is also responsive to 6-ETI in vitro and in mouse models. 6-ETI induces S phase arrest and inhibits DNA synthesis. RNA sequencing of in vitro generated PEL resistant clones and CRISPR knock out of ADK (ADK KO), respectively, indicated that mutations or loss of expression of ADK renders cells resistant to treatment. This data demonstrates that ADK expression can be used as a predictive biomarker of response to 6-ETI, which can help identify which patients are more likely to respond to this treatment. We investigated which pathways are differentially regulated in sensitive and resistant cells to better delineate the mechanism of action of 6-ETI and to design effective combinatorial regimens and prevent resistance. We found that drug sensitivity was associated with AMPK activation and inhibition of PI3K/mTOR/p70S6K signaling. Little is known about the function of ADK in plasma cell neoplasms. Knock-out of this protein in PEL, or use of ADK chemical inhibitors, do not affect their viability. Thus, we used ADK KO cell lines to examine the role of ADK in these tumors and to determine if cells undergo adaptations that may contribute to 6-ETI resistance and represent potential vulnerabilities to combat it. We performed metabolic and transcriptomic profiling of wild type (WT) (6-ETI sensitive) and ADK KO (6-ETI resistant) cells to achieve a comprehensive assessment of all the metabolic perturbations and gene expression changes induced by knocking out ADK. We also treated these cells with 6-ETI to examine the effects in sensitive and resistant cells. This integrated analysis revealed that 6-ETI depletes sensitive PEL cells of their nucleotide pools accompanied by the downregulation of several genes in purine and pyrimidine biosynthesis pathways. We found that adenine supplementation rescues sensitive PEL cells from 6-ETI induced cytotoxicity, reverses p70S6K inhibition and restores DNA synthesis suggesting that purine metabolism is a critical mediator of 6-ETI induced cytotoxicity. Using seahorse bioenergetic assay, we show that ADK KO resistant cells have impaired mitochondrial respiration indicating that ADK plays a critical role in mitochondrial bioenergetics. Metabolic profiling of these ADK KO resistant cells showed that these cells have elevated levels of de novo pyrimidine metabolic intermediates. Metabolic flux through de novo pyrimidine is controlled by the rate limiting enzyme CAD. The activity of CAD is regulated by ribosomal protein S6 Kinase 1(S6K1) by phosphorylation at its (Ser1859) site. Using western blotting, we observed a striking increase of phosphorylation of CAD at its S6K1 site (Ser1859) in ADK KO cells compared to WT cells. This is the first to date study that characterizes the role of ADK in lymphomas. Our data indicates that ADK KO cells have undergone metabolic reprogramming to upregulate de novo pyrimidine biosynthesis and p70S6K signaling. Moreover, we found that 6-ETI synergizes with the pan PI3K inhibitor BKM120 highlighting nucleotide metabolism and PI3K/mTOR signaling as key therapeutic vulnerabilities targeted by this novel nucleoside analog. Disclosures No relevant conflicts of interest to declare.

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

Sugar-modified nucleosides have gained considerable attention in the scientific community, either for use as molecular probes or as therapeutic agents. When the methylene group of the ribose ring is replaced with a sulfur atom at the 3’-position, these compounds have proved to be structurally potent nucleoside analogues, and the best example is BCH-189. The majority of methods traditionally involves the chemical modification of nucleoside structures. It requires the creation of artificial sugars, which is accompanied by coupling nucleobases via N-glycosylation. However, over the last three decades, efforts were made for the synthesis of 1,3-oxathiolane nucleosides by selective N-glycosylation of carbohydrate precursors at C-1, and this approach has emerged as a strong alternative that allows simple modification. This review aims to provide a comprehensive overview on the reported methods in the literature to access 1,3-oxathiolane nucleosides. The first focus of this review is the construction of the 1,3-oxathiolane ring from different starting materials. The second focus involves the coupling of the 1,3-oxathiolane ring with different nucleobases in a way that only one isomer is produced in a stereoselective manner via N-glycosylation. An emphasis has been placed on the C–N-glycosidic bond constructed during the formation of the nucleoside analogue. The third focus is on the separation of enantiomers of 1,3-oxathiolane nucleosides via resolution methods. The chemical as well as enzymatic procedures are reviewed and segregated in this review for effective synthesis of 1,3-oxathiolane nucleoside analogues.