A Shared Prebiotic Formation of Neopterins and Guanine Nucleosides from Pyrimidine Bases

The prebiotic origins of biopolymers and metabolic co‐factors are key questions in Origins of Life studies. In a simple warm‐little‐pond model, using a drying phase to produce a urea‐enriched solution, we present a prebiotic synthetic path for the simultaneous formation of neopterins and tetrahydroneopterins, along with purine nucleosides. We show that, in the presence of ribose and in a formylating environment consisting of urea, ammonium formate, and water (UAFW), the formation of neopterins from pyrimidine precursors is robust, while the simultaneous formation of guanosine requires a significantly higher ribose concentration. Furthermore, these reactions provide a tetrahydropterin–pterin redox pair. This model suggests a prebiotic link in the origin of purine nucleosides and pterin cofactors that provides a possible deep prebiotic temporal connection for the emergence of nucleic acids and metabolic cofactors.