Design, synthesis, and antiviral evaluation of 2-deoxy-D-ribosides of substituted benzimidazoles as potential agents for human cytomegalovirus infections

Introduction of pseudo-base benzimidazole derivatives into nucleosides via base exchange by a nucleoside metabolic enzyme

In alternate organic synthesis, biocatalysis using enzymes provides a more stereoselective and cost-effective approach. Synthesis of unnatural nucleosides by nucleoside base exchange reactions using nucleoside-metabolizing enzymes has previously shown that the 5-position recognition of pyrimidine bases on nucleoside substrates is loose and can be used to introduce functional molecules into pyrimidine nucleosides. Here we explored the incorporation of purine pseudo bases into nucleosides by the base exchange reaction of pyrimidine nucleoside phosphorylase (PyNP), demonstrating that an imidazole five-membered ring is an essential structure for the reaction. In the case of benzimidazole, the base exchange proceeded to give the deoxyribose form in 96 % yield, and the ribose form in 23 % yield. The reaction also proceeded with 1H-imidazo[4,5-b]phenazine, a benzimidazole analogue with an additional ring, although the yield of nucleoside was only 31 %. Docking simulations between 1H and imidazo[4,5-b]phenazine nucleoside and the active site of PyNP (PDB 1BRW) supported our observation that 1H-imidazo[4,5-b]phenazine can be used as a substrate by PyNP. Thus, the enzymatic substitution reaction using PyNP can be used to incorporate many purine pseudo bases and benzimidazole derivatives with various functional groups into nucleoside structures, which have potential utility as diagnostic or therapeutic agents.

Targeting the terminase: An important step forward in the treatment and prophylaxis of human cytomegalovirus infections

A key step in the replication of human cytomegalovirus (HCMV) in the host cell is the generation and packaging of unit-length genomes into preformed capsids. Enzymes required for this process are so-called terminases, first described for double-stranded DNA bacteriophages. The HCMV terminase consists of the two subunits, the ATPase pUL56 and the nuclease pUL89, and a potential third component pUL51. The terminase subunits are essential for virus replication and are highly conserved throughout the Herpesviridae family. Together with the portal protein pUL104 they form a powerful biological nanomotor. It has been shown for tailed dsDNA bacteriophages that DNA translocation into preformed capsid needs an extraordinary amount of energy. The HCMV terminase subunit pUL56 provides the required ATP hydrolyzing activity. The necessary nuclease activity to cleave the concatemers into unit-length genomes is mediated by the terminase subunit pUL89. Whether this cleavage is mediated by site-specific duplex nicking has not been demonstrated, however, it is required for packaging. Binding to the portal is a prerequisite for DNA translocation. To date, it is a common view that during translocation the terminase moves along some domains of the DNA by a binding and release mechanism. These critical structures have proven to be outstanding targets for drugs to treat HCMV infections because corresponding structures do not exist in mammalian cells. Herein we examine the HCMV terminase as a target for drugs and review several inhibitors discovered by both lead-directed medicinal chemistry and by target-specific design. In addition to producing clinically active compounds the research also has furthered the understanding of the role and function of the terminase itself.

Anti-Adenoviral Activity of 2-(3-Chlorotetrahydrofuran-2-yl)-4-Tosyl-5-(Perfluoropropyl)-1,2,3-Triazole

Background and objectives: A considerable increase in the levels of adenoviral diseases among both adults and children necessitate the development of effective methods for its prevention and treatment. The synthesis of the new fluorinated 1,2,3-triazoles, and the study of the mechanisms of their action, are promising for the development of efficient antiviral drugs of our time. Materials and Methods: Antiviral activity and cell cytotoxic effect of 2-(3-chlorotetrahydrofuran-2-yl)-4-tosyl-5-(perfluoropropyl)-1,2,3-triazole (G29) were determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The influence of the compound on the infectivity of human adenovirus type 5 (HAdV-5) was carried out via the cytomorphology method. The influence of the compound on the cell cycle under a condition of adenovirus infection was studied using flow cytometric analysis of propidium iodide-stained cells. Results: It was found that G29 suppressed HAdV-5 reproduction by 50% in concentrations of 37 μg/mL. Furthermore, the compound reduced the titer of virus obtained de novo, and inhibited HAdV-5 inclusion bodies formation by 84–90%. The use of fluorinated compounds under the conditions of adenovirus infection decreased the number of apoptotic cells by 11% and the number of cells in S phase by 21–42% compared to the profile of infected cells. Conclusions: The fluorinated compound G29 showed moderate activity against HAdV-5 based on several mechanisms. It led to the normalization of the life cycle of cells infected with adenovirus to the level of non-infected cells and caused the obstruction of HAdV-5 reproduction, inducing the formation of non-infectious virus progeny.

Design, synthesis, and antiviral evaluation of some polyhalogenated indole C-nucleosides

2,5, 6-Trichloro-1-(beta-D-ribofuranosyl)benzimidazole (TCRB), 2-bromo-5, 6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (BDCRB) and 2-benzylthio-5,6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (BTDCRB) are benzimidazole nucleosides that exhibit strong and selective anti-HCMV activity. Polyhalogenated indole C-nucleosides were prepared as 1-deaza analogs of the benzimidazole nucleosides TCRB and BDCRB. A mild Knoevenagel coupling reaction between an indol-2-thione and a ribofuranose derivative was developed for the synthesis of 2-benzylthio-5, 6-dichloro-3-(beta-D-ribofuranosyl)indole (12). 3-(beta-D-ribofuranosyl)-2,5,6-trichloroindole (16) was prepared from 12 in 4 steps. A Lewis acid-mediated glycosylation method was then developed to prepare the targeted 2-haloindole C-nucleoside 16 stereoselectively in four steps from the corresponding 2-haloindole aglycons. Only 12 was active against HCMV but it also was somewhat cytotoxic.

Synthesis and antiviral properties of arabino and ribonucleosides of 1,3-dideazaadenine, 4-nitro-1,3-dideazapurine and diketopiperazine

Different arabinosides and ribosides, viz. Ara-DDA or 9(1-beta-D-arabinofuranosyl) 1,3-dideazaadenine (6), Ara-NDDP or 9(1-beta-D-arabinofuranosyl) 4-nitro-1,3-dideazapurine (7), Ara-DKP or 1(1-beta-D-arabinofuranosyl) diketopiperazine (8), Ribo-DDA or 9(1-beta-D-ribofuranosyl) 1,3-dideazaadenine (9) and Ribo-NDDP or 9(1-beta-D-ribofuranosyl) 4-nitro-1,3-dideazapurine (10) have been synthesized as probable antiviral agents. The arabinosides have been synthesized using the catalyst TDA-1 that causes stereospecific formation of beta-nucleosides while a one-pot synthesis procedure was adopted for the synthesis of the ribonucleosides where beta-anomers were obtained in higher yields. All the five nucleoside analogs have been screened for antiviral property against HIV-1 (IIIB), HSV-1 and 2, parainfluenza-3, reovirus-1 and many others. It was observed that arabinosides had greater inhibitory action than ribosides. The compound 7 or Ara-NDDP has shown maximum inhibition of HIV-1 replication than the rest of the molecules with an IC50 of 79.4 microg/mL.

Synthesis and antiviral evaluation of benzimidazoles, quinoxalines and indoles from dehydroabietic acid

Several heterocycles, such as benzimidazoles, quinoxalines and indoles incorporated into a hydrophenanthrene and naphthalene skeleton, were synthesised from two useful ortho-bromonitro precursors derived from dehydroabietic acid: methyl 12-bromo-13-nitro-deisopropyldehydroabietate and methyl 12-bromo-13,14-dinitro-deisopropyldehydroabietate. The new heterocycles were evaluated for their activity in vitro against several RNA and DNA viruses.

Polyhalogenobenzimidazoles: synthesis and their inhibitory activity against casein kinases

A series of novel polyhalogenated benzimidazoles have been prepared by exhaustive bromination of a variety of 2-substituted benzimidazoles. The efficacy of both new compounds and a number of their previously described cognates as inhibitors of casein kinases CK1, CK2 and G-CK was investigated. The type of N-1 alkyl substituent as well as introduction of a polyfluoroalkyl moiety at position 2 did not markedly influence the inhibitory efficacy toward CK2 of the respective 4,5,6,7-tetrabromobenzimidazole derivatives which conversely were almost ineffective toward CK1 and G-CK. However, 4,5,6,7-tetrabromobenzimidazoles substituted at position 2 with either chlorine, bromine or sulfur atom, while manifesting a still considerable inhibitory activity against CK2 (IC(50) in the 0.49-0.93 microM range) proved to be potentially powerful inhibitors also against CK1 (IC(50) in the 18.4-2.2 microM range).

Potent and selective inhibition of human cytomegalovirus replication by 1263W94, a benzimidazole L-riboside with a unique mode of action

Benzimidazole nucleosides have been shown to be potent inhibitors of human cytomegalovirus (HCMV) replication in vitro. As part of the exploration of structure-activity relationships within this series, we synthesized the 2-isopropylamino derivative (3322W93) of 1H-beta-D-ribofuranoside-2-bromo-5,6-dichlorobenzimidazole (BDCRB) and the biologically unnatural L-sugars corresponding to both compounds. One of the L derivatives, 1H-beta-L-ribofuranoside-2-isopropylamino-5,6-dichlorobenzimidazole (1263W94), showed significant antiviral potency in vitro against both laboratory HCMV strains and clinical HCMV isolates, including those resistant to ganciclovir (GCV), foscarnet, and BDCRB. 1263W94 inhibited viral replication in a dose-dependent manner, with a mean 50% inhibitory concentration (IC(50)) of 0.12 +/- 0.01 microM compared to a mean IC(50) for GCV of 0.53 +/- 0.04 microM, as measured by a multicycle DNA hybridization assay. In a single replication cycle, 1263W94 treatment reduced viral DNA synthesis, as well as overall virus yield. HCMV mutants resistant to 1263W94 were isolated, establishing that the target of 1263W94 was a viral gene product. The resistance mutation was mapped to the UL97 open reading frame. The pUL97 protein kinase was strongly inhibited by 1263W94, with 50% inhibition occurring at 3 nM. Although HCMV DNA synthesis was inhibited by 1263W94, the inhibition was not mediated by the inhibition of viral DNA polymerase. The parent benzimidazole D-riboside BDCRB inhibits viral DNA maturation and processing, whereas 1263W94 does not. The mechanism of the antiviral effect of L-riboside 1263W94 is thus distinct from those of GCV and of BDCRB. In summary, 1263W94 inhibits viral replication by a novel mechanism that is not yet completely understood.