Synthesis, antiviral activity, and stability of nucleoside analogs containing tricyclic bases

Highly Chemoselective Synthesis of Purino[3,2-c]oxazoles via the Asymmetric Dearomative [3+2] Cycloaddition of Purines with Donor-Acceptor Oxiranes

A Ni(II)/bisoxazoline-catalyzed asymmetric dearomative [3+2] cycloaddition of substituted purines with donor-acceptor oxiranes was developed. This reaction, which proceeds via highly chemoselective C-C bond cleavage of the oxiranes, accesses chiral purino[3,2-c]oxazole compounds (≤99% ee after enrichment via crystallization). The electronic effects of the purine ring determine the reactivity of the substrate. The general applicability of this method was illustrated by gram-scale synthesis, the diverse transformations of the product, and the promising biological activities of selected derivatives.

Novel nucleoside analogues targeting HCV replication through an NS5A-dependent inhibition mechanism

A series of new tricyclic nucleosides were synthesized and evaluated as hepatitis C virus (HCV) replication inhibitors. Initial screening in a HCV replicon system, derived from a genotype 1b isolate, identified 9-benzylamino-3-(β-D-ribofuranosyl)-3H-imidazo[4',5':5,6]pyrido[2,3-b]pyrazine (15d) as the most potent analogue. Comparative assessment of 15d activity against HCV full-length viruses or subgenomic replicons derived from genotypes 1 to 4 revealed a specificity of the compound for genotypes 1 and 3. Surprisingly, resistance mutations selected against 15d were mapped to domains II and III of the non-structural protein 5A (NS5A), but not to the RNA-dependent RNA polymerase residing in NS5B. These results argue that compound 15d might represent a lead for the development of a novel class of NS5A inhibitors.

Base-Modified Nucleosides: Etheno Derivatives

This review presents synthesis and chemistry of nucleoside analogs, possessing an additional fused, heterocyclic ring of the "etheno" type, such as 1,N(6)-ethenoadenosine, 1,N(4)-ethenocytidine, 1,N(2)-ethenoguanosine, and other related derivatives. Formation of ethenonucleosides, in the presence of α-halocarbonyl reagents and their mechanism, stability, and degradation, reactions of substitution and transglycosylation, as well as their application in the nucleoside synthesis, have been described. Some of the discussed compounds may be applied as chemotherapeutic agents in antiviral and anticancer treatment, acting as pro-nucleosides of already known, biologically active nucleoside analogs.

Design, synthesis and antiviral evaluation of 2'-C-methyl branched guanosine pronucleotides: the discovery of IDX184, a potent liver-targeted HCV polymerase inhibitor

BACKGROUND

Ribonucleoside analogs possessing a β-methyl substituent at the 2'-position of the d-ribose moiety have been previously discovered to be potent and selective inhibitors of hepatitis C virus (HCV) replication, their triphosphates acting as alternative substrate inhibitors of the HCV RdRp NS5B. Results/methodology: In this article, the authors detail the synthesis, anti-HCV evaluation in cell-based replicon assays and structure-activity relationships of several phosphoramidate diester derivatives of 2'-C-methylguanosine (2'-MeG).

CONCLUSION

The most promising compound, namely the O-[S-(hydroxyl)pivaloyl-2-thioethyl]{abbreviated as O-[(HO)tBuSATE)]} N-benzylamine phosphoramidate diester derivative (IDX184), was selected for further in vivo studies, and was the first clinical pronucleotide evaluated for the treatment of chronic hepatitis C up to Phase II trials.

Diverse models for anti-HIV activity of purine nucleoside analogs

Background

Purine nucleoside analogs (PNAs) constitute an important group of cytotoxic drugs for the treatment of neoplastic and autoimmune diseases. In the present study, classification models have been developed for the prediction of the anti-HIV activity of purine nucleoside analogs.

Results

The topochemical version of superaugmented pendentic index-4 has been proposed and successfully utilized for the development of models. A total of 60 2D and 3D molecular descriptors (MDs) of diverse nature were selected for building the classification models using decision tree (DT), random forest (RF), support vector machine (SVM), and moving average analysis (MAA). The values of most of these descriptors for each of the analogs in the dataset were computed using the Dragon software (version 5.3). An in-house computer program was also employed to calculate additional MDs which were not included in the Dragon software. DT, RF, and SVM correctly classified the analogs into actives and inactives with an accuracy of 89 %, 83 %, and 78 %, respectively. MAA-based models predicted the anti-HIV activity of purine nucleoside analogs with a non-error rate up to 98 %. Therapeutic active spans of the suggested MAA-based models not only showed more potency but also exhibited enhanced safety as revealed by comparatively high values of selectivity index (SI). The statistical importance of the developed models was appraised via intercorrelation analysis, specificity, sensitivity, non-error rate, and Matthews correlation coefficient.

Conclusions

High predictability of the proposed models clearly indicates an immense potential for developing lead molecules for potent but safe anti-HIV purine nucleoside analogs.