Synthesis of 5′-substituted fluoro-neplanocin A analogues: importance of a hydrogen bonding donor at 5′-position for the inhibitory activity of S-adenosylhomocysteine hydrolase

Enhancing the Antiviral Efficacy of RNA-Dependent RNA Polymerase Inhibition by Combination with Modulators of Pyrimidine Metabolism

Genome-wide analysis of the mode of action of GSK983, a potent antiviral agent, led to the identification of dihydroorotate dehydrogenase as its target along with the discovery that genetic knockdown of pyrimidine salvage sensitized cells to GSK983. Because GSK983 is an ineffective antiviral in the presence of physiological uridine concentrations, we explored combining GSK983 with pyrimidine salvage inhibitors. We synthesized and evaluated analogs of cyclopentenyl uracil (CPU), an inhibitor of uridine salvage. We found that CPU was converted into its triphosphate in cells. When combined with GSK983, CPU resulted in large drops in cellular UTP and CTP pools. Consequently, CPU-GSK983 suppressed dengue virus replication in the presence of physiological concentrations of uridine. In addition, the CPU-GSK983 combination markedly enhanced the effect of RNA-dependent RNA polymerase (RdRp) inhibition on viral infection. Our findings highlight a new host-targeting strategy for potentiating the antiviral activity of RdRp inhibitors.

Synthesis of 3'-halo-5'-norcarbocyclic nucleoside phosphonates as potent anti-HIV agents

The synthesis and the antiviral evaluation of 3'-halo (iodo and fluoro) 5'-norcarbocyclic nucleoside phosphonates is described. No antiviral activity was observed against Zika virus, Dengue virus 2, HSV-1, HSV-2 and Chikungunya virus. In contrast, some of the synthesized compounds are potent inhibitors of the replication of HIV-1, comparatively to (R)-PMPA, with no concomitant cytotoxicity.

Leishmania donovani Aurora kinase: A promising therapeutic target against visceral leishmaniasis

BACKGROUND

Aurora kinases are key mitotic kinases executing multiple aspects of eukaryotic cell-division. The apicomplexan homologs being essential for survival, suggest that the Leishmania homolog, annotated LdAIRK, may be equally important.

METHODS

Bioinformatics, stage-specific immunofluorescence microscopy, immunoblotting, RT-PCR, molecular docking, in-vitro kinase assay, anti-leishmanial activity assays, flow cytometry, fluorescence microscopy.

RESULTS

Ldairk expression is seen to vary as the cell-cycle progresses from G1 through S and finally G2M and cytokinesis. Kinetic studies demonstrate their enzymatic activity exhibiting a Km and Vmax of 6.12μM and 82.9pmoles·min(-1)mg(-1) respectively against ATP using recombinant Leishmania donovani H3, its physiological substrate. Due to the failure of LdAIRK-/+ knock-out parasites to survive, we adopted a chemical knock-down approach. Based on the conservation of key active site residues, three mammalian Aurora kinase inhibitors were investigated to evaluate their potential as inhibitors of LdAIRK activity. Interestingly, the cell-cycle progressed unhindered, despite treatment with GSK-1070916 or Barasertib, inhibitors with greater potencies for the ATP-binding pocket compared to Hesperadin, which at nanomolar concentrations, severely compromised viability at IC50s 105.9 and 36.4nM for promastigotes and amastigotes, respectively. Cell-cycle and morphological studies implicated their role in both mitosis and cytokinesis.

CONCLUSION

We identified an Aurora kinase homolog in L. donovani implicated in cell-cycle progression, whose inhibition led to aberrant changes in cell-cycle progression and reduced viability.

GENERAL SIGNIFICANCE

Human homologs being actively pursued drug targets and the observations with LdAIRK in both promastigotes and amastigotes suggest their potential as therapeutic-targets. Importantly, our results encourage the exploration of other proteins identified herein as potential novel drug targets.

Regio- and stereoselective synthesis of 2′-β-substituted-fluoroneplanocin A analogues as potential anticancer agents

Regio- and stereoselective synthesis of a series of 2′-β-substituted-6′-fluoro-cyclopentenyl-pyrimidines and -purines 8 and 9 as potential anticancer agents is described.

Synthesis of the natural enantiomer of neplanocin B

(-)-Neplanocin B, the natural isomer of a component of the neplanocin family was diasteroselectively synthesized from 2,3-O-isopropylidene-D-1,4-ribonolactone. However, when evaluated against several DNA and RNA viruses in cell culture experiments, it did not show any antiviral activity.

Stereospecific synthesis of (-)-neplanocin F

The stereospecific synthesis of (-)-neplanocin F was achieved in 15 steps from 2,3-O-isopropylidene-D-1,4-ribonolactone. The synthetic methodology can give an access through appropriate modifications to new series of carbanucleosides.

Design, synthesis, and molecular modeling studies of 5'-deoxy-5'-ureidoadenosine: 5'-ureido group as multiple hydrogen bonding donor in the active site of S-adenosylhomocysteine hydrolase

5'-Deoxy-5'-ureidoadenosine was designed and synthesized as a potent inhibitor of S-adenosylhomocysteine hydrolase (SAH), in which 5'-ureido group acted as multiple hydrogen bonding donor in binding with active site residues of SAH in the molecular modeling study.

Synthesis of 4/5-Deoxy-4/5-nucleobase Derivatives of 3-O-Methyl-D-chiro-inositol as Potential Antiviral Agents

Using D-pinitol (= 3-O-methyl-D-chiro-inositol) as starting material, a concise synthesis of 4/5-deoxy-4/5-nucleobase derivatives 11-19 has been achieved. The key intermediate 9 was obtained in good yield via an epoxidation from mono-methanesulfonate of D-pinitol. The process of opening of the epoxide ring in 9 by nucleobases appeared to be regioselective in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). All the synthesized carbocyclic nucleosides were assayed against several viruses and tumors such as HIV-1, HSV-1, and HSV-2, and lung and bladder cancer. However, only compounds 14b, 14a, 16a, 16b, and 19 showed mild inhibitory effect against human lung cancer cell lines (PG) with IC50 values ranging from 50 to 100 microM, and the other compounds did not exhibit any significant antiviral activity or cytotoxicity even at concentrations up to 200 microM.