Progress Toward the Syntheses of a Phosphoramidite and Triphosphate Containing a DEB-FAPy-dG Adduct
1,3-Butadiene (BD) is a known carcinogen that is abundantly found in cigarette smoke, automobile exhaust, and some industrial settings. Occupational exposure to BD leads to the blood disorders leukemia and lymphoma, while exposed animals develop cancers of the liver, lungs, mammary glands, and ovaries. Upon entering the body, BD is metabolically activated by Cytochrome 450 monooxygenases, giving rise to the reactive electrophile 1,2,3,4-diepoxybutane (DEB). This genotoxic compound alkylates guanine bases in DNA to produce a range of adducts, including N7-(2-hydroxy-3,4-epoxy-1-yl)-dG (N7-DEB-dG). These adducts are inherently unstable due to a positive charge at the N7 position of the purine heterocycle, which can cause spontaneous depurination or imidazole ring opening, forming a formamidopyrimidine (FAPy) adduct. The synthesis and structural characterization of DEB-FAPy-dG adducts has been established, however, the insertion of these adducts into synthetic DNA has not been attempted. Here we report two strategies to achieve this goal: the synthesis of a phosphoramidite and the synthesis of a triphosphate both containing the DEB-FAPy-dG adduct. The synthesis of the phosphoramidite and triphosphate will allow for insertion into an oligodeoxynucleotide using a DNA synthesizer and insertion into DNA by DNA polymerase, respectively. Incorporation of DEB-FAPy-dG into DNA by this two-pronged approach will allow for analyses of the specific mechanisms by which these non-canonical nucleobases impact DNA replication and potentially cause mutations. This knowledge will set the foundation for understanding the outcomes of FAPy lesions in cells and how those lesions can be repaired.