Prebiotic Chemistry of Nucleobases and Nucleotides

The origin of biological nucleic acids and its building blocks is still an open question, for which have been proposed several routes and geochemical scenarios. For the origin of RNA, two general approaches are under study and debate: its prebiotic formation by chemical routes from simple precursors in the right geochemical conditions, or its origin as an evolutionary product resulting from a complex chemical space of pre-RNA molecules and supramolecular assemblies, with a key role of non-biological nucleobases and nucleotides. In both cases, for the origin of its building nucleobases and its nucleosides/nucleotides, recent studies have highlighted the importance of urea in the process. Urea is a versatile molecule that could have formed in a prebiotic environment based on “warm little ponds” of viscous eutectic solutions – environments which favor the formation of nucleobases, nucleosides, and as a promoter of the incorporation of phosphate in early organophosphates and nucleotides. We will summarize in this chapter the main prebiotic routes and processes for the origin of nucleobases and nucleotides, in which urea could have played a central role, including some historical notes that could help to contextualize what are we thinking now in the origin of nucleic acids building blocks, and how did we get there.