1,3-Butadiene(BD) is a ubiquitous environmental mutagen and a known human carcinogen. BD can be bio-activated by cytochrome P450 monooxygenases to form mutagenic epoxide metabolites including the strongly genotoxic diepoxide, 2,3,4-diepoxybutane (DEB). DEB alkylates DNA at the N7-position of guanine to give N⁷-alkylated-dG adducts i.e N⁷-(2-hydroxy-3,4-epoxy-1-yl)-(N7-DEB-dG) adducts, which undergo 5-membered imidazole ring open to give corresponding N⁶-[2-deoxy-D-erythro-pentofuranosyl]-2,6-diamino-3,4-dihydro-4-oxo-5-N-1-(oxiran-2-yl)propan-1-ol-formamidopyrimidine (DEB-FAPy-dG) adduct. By analogy with other FAPy adducts, DEB-FAPy-dG is anticipated to interfere with DNA replication by blocking DNA synthesis and inducing mispairing and polymerase errors. Herein, we describe the synthesis and structural elucidation of chemically modified nucleoside phosphoramidite containing DEB-FAPy-dG, as well as solid phase synthesis of DNA strands containing this non-canonical nucleobase. A muti-step synthetic strategy starting with dG was applied to obtain DEB-FAPy-dG and the corresponding phosphoramidite. The chemically modified nucleoside derivative was incorporated into DNA oligomers by solid synthesis to obtain DNA strands containing site-specific DEB-FAPy-dG. The structures of newly synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, mass, and LC-MS analysis. A convenient and efficient synthetic strategy of DEB-FAPy-dG containing DNA was established, allowing for future analyses of the specific mechanisms by which these non-canonical nucleobases cause mutations during DNA replication. This knowledge will set the foundation for understanding the consequences of FAPy lesions in cells and how those lesions can be repaired.

Christine Lorentz

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