Enantiomeric synthesis of carbocyclic d-4′-C-methylribonucleosides as potential antiviral agents

Synthesis of 4'-Substituted Carbocyclic Uracil Derivatives and Their Monophosphate Prodrugs as Potential Antiviral Agents

Over the past decades, both 4'-modified nucleoside and carbocyclic nucleoside analogs have been under the spotlight as several compounds from either family showed anti-HIV, HCV, RSV or SARS-CoV-2 activity. Herein, we designed compounds combining these two features and report the synthesis of a series of novel 4'-substituted carbocyclic uracil derivatives along with their corresponding monophosphate prodrugs. These compounds were successfully prepared in 19 to 22 steps from the commercially available (-)-Vince lactam and were evaluated against a panel of RNA viruses including SARS-CoV-2, influenza A/B viruses and norovirus.

Synthesis and Antiviral Evaluation of Carbocyclic Nucleoside Analogs of Nucleoside Reverse Transcriptase Translocation Inhibitor MK-8591 (4'-Ethynyl-2-fluoro-2'-deoxyadenosine)

MK-8591 (4'-ethynyl-2-fluoro-2'-deoxyadenosine) is a novel nucleoside analog that displays a differentiated mechanism of action as a nucleoside reverse transcriptase translocation inhibitor (NRTTI) compared to approved NRTIs. Herein, we describe our recent efforts to explore the impact of structural changes to the properties of MK-8591 through the synthesis and antiviral evaluation of carbocyclic derivatives. Synthesized analogs were evaluated for their antiviral activity, and the corresponding triphosphates were synthesized and evaluated in a biochemical assay. 4'-Ethynyl-G derivative (±)-29 displayed a promising IC₅₀ of 33 nM in a hPBMC cell-based antiviral assay, and its triphosphate (TP), (±)-29-TP, displayed an IC₅₀ of 324 nM in a biochemical RT-polymerase assay. Improved TP anabolite delivery resulting in improved in vitro potency was achieved by preparing the corresponding phosphoramidate prodrug of single enantiomer 29b, with 6-ethoxy G derivative 34b displaying a significantly improved IC₅₀ of 3.0 nM, paving the way for new directions for this novel class of nucleoside analogs.

Pyrimidine Nucleotides Containing a (S)-Methanocarba Ring as P2Y6 Receptor Agonists

Both agonists and antagonists of the UDP-activated P2Y₆ receptor (P2Y₆R) have been proposed for therapeutic use, in conditions such as cancer, inflammation, neurodegeneration and diabetes. Uracil nucleotides containing a South-bicyclo[3.1.0]hexane ((S)-methanocarba) ring system in place of the ribose ring were synthesized and shown to be potent P2Y₆R agonists in a calcium mobilization assay. The (S)-methanocarba modification was compatible with either a 5-iodo or 4-methoxyimino group on the pyrimidine, but not with a α,β-methylene 5´-diphosphate. (S)-Methanocarba dinucleotide potency was compatible with a N⁴-methoxy modification on the proximal nucleoside that is assumed to bind at the P2Y₆R similarly to UDP; (N)-methanocarba was preferred on the distal nucleoside moiety. This suggests that the distal dinucleotide P2Y₆R binding site prefers a ribose-like group that can attain a (N) conformation, rather than (S). Dinucleotide binding was modeled by homology modeling, docking and molecular dynamics simulations, which suggested the same ribose conformational preferences found empirically.

A review of methods to synthesise 4′-substituted nucleosides

Modified nucleosides have received a great deal of attention from the scientific community, either for use as therapeutic agents, diagnostic tools, or as molecular probes.