Nucleotide-Bearing Benzylidene-Tetrahydroxanthylium Near-IR Fluorophore for Sensing DNA Replication, Secondary Structures and Interactions.

Thymidine triphosphate bearing benzylidene-tetrahydroxanthylium near-IR fluorophore linked to the 5-methyl group via triazole was synthesized through the CuAAC reaction and was used for polymerase synthesis of labelled DNA probes. The fluorophore lights up upon incorporation to DNA (up to 348-times) presumably due to interactions in major groove and the fluorescence further increases in the single-stranded oligonucleotide. The labelled dsDNA senses binding of small molecules and proteins by a strong decrease of fluorescence. The nucleotide was used as a light-up building block in real-time PCR for detection of SARS-CoV-2 virus.

Antiviral Activity of 7-Substituted 7-Deazapurine Ribonucleosides, Monophosphate Prodrugs, and Triphoshates against Emerging RNA Viruses.

A series of 7-deazaadenine ribonucleosides bearing alkyl, alkenyl, alkynyl, aryl, or hetaryl groups at position 7 as well as their 5'-O-triphosphates and two types of monophosphate prodrugs (phosphoramidates and S-acylthioethanol esters) were prepared and tested for antiviral activity against selected RNA viruses (Dengue, Zika, tick-borne encephalitis, West Nile, and SARS-CoV-2). The modified triphosphates inhibited the viral RNA-dependent RNA polymerases at micromolar concentrations through the incorporation of the modified nucleotide and stopping a further extension of the RNA chain. 7-Deazaadenosine nucleosides bearing ethynyl or small hetaryl groups at position 7 showed (sub)micromolar antiviral activities but significant cytotoxicity, whereas the nucleosides bearing bulkier heterocycles were still active but less toxic. Unexpectedly, the monophosphate prodrugs were similarly or less active than the corresponding nucleosides in the in vitro antiviral assays, although the bis(S-acylthioethanol) prodrug 14h was transported to the Huh7 cells and efficiently released the nucleoside monophosphate.