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4,5-Dicyanoimidazole and 2-aminothiazole are azoles that have previously been implicated in prebiotic nucleotide synthesis. The former compound is a byproduct of adenine synthesis, and the latter compound has been shown to be capable of separating C2 and C3 sugars via crystallization as their aminals. We now report that the elusive intermediate cyanoacetylene can be captured by 4,5-dicyanoimidazole and accumulated as the crystalline compound N-cyanovinyl-4,5-dicyanoimidazole, thus providing a solution to the problem of concentration of atmospherically formed cyanoacetylene. Importantly, this intermediate is a competent cyanoacetylene surrogate, reacting with ribo-aminooxazoline in formamide to give ribo-anhydrocytidine ─ an intermediate in the divergent synthesis of purine and pyrimidine nucleotides. We also report a prebiotically plausible synthesis of 2-aminothiazole and examine the mechanism of its formation. The utilization of each of these azoles enhances the prebiotic synthesis of ribonucleotides, while their syntheses comport with the cyanosulfidic scenario we have previously described.

All four cellular subsystems can be provided under compatible prebiotic conditions., The centrality of the Krebs cycle in metabolism has long been interpreted as evidence of its antiquity, and consequently, questions regarding its provenance, and whether it initially functioned as a cycle or not, have received much attention. The present report shows that prebiotic oxidation of α-hydroxy carboxylates can be achieved by UV photolysis of a simple geochemical species (HS−), which leads to α-oxo carboxylates that feature in the Krebs cycle and glyoxylate shunt. Further reaction of these products leads to almost all intermediates of the Krebs cycle proper, succinate semialdehyde bypass, and glyoxylate shunt. Fumarate, the missing Krebs cycle component, and the required α-hydroxy carboxylates can be provided by a highly related hydrogen cyanide chemistry, which also provides precursors for amino acids, nucleotides, and phospholipids.

When considering life’s aetiology, the first questions that must be addressed are “how?” and “where?” were ostensibly complex molecules, considered necessary for life’s beginning, constructed from simpler, more abundant feedstock molecules on primitive Earth. Previously, we have used multiple clues from the prebiotic synthetic requirements of (proto)biomolecules to pinpoint a set of closely related geochemical scenarios that are suggestive of flow and semi-batch chemistries. We now wish to report a multistep, uninterrupted synthesis of a key heterocycle (2-aminooxazole) en route to activated nucleotides starting from highly plausible, prebiotic feedstock molecules under conditions which mimic this scenario. Further consideration of the scenario has uncovered additional pertinent and novel aspects of prebiotic chemistry, which greatly enhance the efficiency and plausibility of the synthesis., There is still much debate on early Earth geochemical conditions affecting the chemistry of simple synthons that originated life. Here, the authors report an uninterrupted multistep synthetic route to 2-aminooxazole by means of flow chemistry equipment, mimicking a plausible early Earth (geo)chemical scenario.