High Fidelity Enzyme-Free Primer Extension with an Ethynylpyridone Thymidine Analog

A ProTide of AZT Shows Activity Against Human Papillomaviruses

Infection by human papillomaviruses (HPV) can cause warts and tumors. So far, no small molecule antiviral has been approved for the treatment of infections with this DNA virus, although preclinical studies show activity for nucleosidic compounds, such as 9-(2-phosphonylmethoxy)ethylguanine (PMEG) or cidofovir. This prompted us to test new prodrug versions of the nucleoside analog 3'-azido-2',3'-dideoxythymidine (AZT), known to be active against reverse transcriptases and approved for the treatment of HIV. Here we report the synthesis of an ethylbutyl alaninyl ester phosphosphoramidate prodrug of AZT, dubbed AZAEB, and its activity against HPV, a target not known to be sensitive to AZT. A methyl ester derivative was found to be inactive against this and three other DNA viruses, while the phosphoramidate prodrug AZAEB showed a modest inhibitory effect against HPV types 6, 11, 18 and 31. Our results open up new avenues of study for the treatment of diseases caused by members of the papillomaviridae family.

Caging of a Strongly Pairing Fluorescent Thymidine Analog with Soft Nucleophiles

Controlling the pairing strength of nucleobases in DNA through reactions with compounds found inside the cell is a formidable challenge. Here we report how a thiazolyl substituent turns a strongly pairing ethynylpyridone C-nucleoside into a reactive residue in oligonucleotides. The thiazolyl-bearing pyridone reacts with soft nucleophiles, such as glutathione, but not with hard nucleophiles like hydroxide or carbonate. The addition products pair much more weakly with adenine in a complementary strand than the starting material, and also change their fluorescence. This makes oligonucleotides containing the new deoxynucleoside interesting for controlled release. Due to its reactivity toward N, P, S, and Se-nucleophiles, and the visual signal accompanying chemical conversion, the fluorescent nucleotide reported here may also have applications in chemical biology, sensing and diagnostics.