Synthesis And Antiviral Evaluation Of Novel Nucleoside Analogues

Nucleoside analogues have been clinically used for viral infection or cancer in recent 50 years.Nearly 60%of antiviral drugs approved by FDA are nucleoside drugs,and more nucleoside analogues are undergoing clinical studies.However,most nucleoside analogues are polar molecules with low oral bioavailability,high toxicity and easy to acquire drug resistance.Therefore,there is an urgent need to develop new antiviral nucleosides with high potency,selectivity and drug-like properties.Based on the structure of natural nucleosides,nucleoside analogues can be obtained by chemically modifying the sugar,nucleobase,and/or the phosphate moiety of their natural countparts.3’-Fluoro-substituted purine ribonucleoside analogues have been reported to possess broad spectrum antiviral activity,while their pyrimidine nucleoside analogues showed weak antiviral activity.Therefore,to further improve the antiviral activity and selectivity of 3’-fluoro-substituted pyrimidine ribonucleoside analogues,1’-cyano group was introduced and two series of 3’-fluoro-substituted pyrimidine ribonucleoside analogues with D and L configurations were synthesized.In addition,ProTide technology was applied to the target compounds in order to increase their lipophilicity and oral bioavailability.All prepared compounds were evaluated for their antiviral activity against a penel of viruses,including DNA viruses(HCM,VZV)and RNA viruses(SARS-CoV-2,HCoV-229E,Ⅳ).The results showed that the 1’-cyano-3’-fluoropyrimidine ribonucleoside analogues had no inhibitory activity against all tested viruses.The reasons forinactivity may be as follows:3’-fluorine modification is not a good modification for pyrimidine ribonucleoside analogues;Simultaneous modification of the 1’ and 3’ position of the sugar ring results in conformational changes of the targeted compounds,which affects its binding to the target.EIDD-1931,β-D-N4-hydroxycytidine,can inhibit the activity of a variety of RNA viruses,such as coronavirus,influenza virus,venezuelan equine encephalitis virus andnorovirus.To increase the lipophilicity and improve oral bioavailability of EIDD-1931,a series of its lipid prodrugs were synthesized.Besides,3’-fluorine substitutedEIDD-1931 derivative 31 was synthesized and evaluated for its in vitro antiviral activity against different SARS-CoV-2 variants.The results showed that the 3’-fluorine substituted EIDD-1931 derivative 31 did not show any SARS-CoV-2 inhibitory activity,indicating that the 3’-fluorine modification was not tolerated for pyrimidine ribonucleoside analogues.The lipid prodrugs of EIDD-1931(25-28)showed potent anti-SARS-CoV-2 activity,which was more potent than the positive control drugs remdesivir and molnupiravir.Therefore,the lipid prodrugs of EIDD-1931 are promising drug candidates for further study.