Synthesis of a Nucleoside Phosphoramidite of DEB-FAPy-dG Adducts of 1,3-Butadiene
1,3-butadiene (BD) is a human carcinogen that is abundantly found in cigarette smoke, automobile exhaust, and some industrial settings. Exposure to BD leads to the blood disorders leukemia and lymphoma, along with 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 formamidopyrimidine (FAPy) adducts. The synthesis and structural characterization of DEB-FAPy-dG adducts has been established, however, the synthesis of a phosphoramidite containing these adducts and their subsequent insertion into an oligonucleotide has not been reported. Here we report the first synthesis and characterization of a phosphoramidite containing DEB-FAPy-dG adducts. An efficient synthetic scheme of a nucleoside phosphoramidite of DEB-FAPy-dG was established, which opens the door for the incorporation of the DEB-FAPy-dG adducts into an oligonucleotide. Incorporation will allow for future analyses of the specific mechanisms by which these non-canonical nucleobases impact DNA replication and cause mutations. This knowledge will set the foundation for understanding the outcomes of FAPy lesions in cells and how those lesions can be repaired.