RNA Oligomerisation without Added Catalyst from 2′,3′-Cyclic Nucleotides by Drying at Air-Water Interfaces**

For the emergence of life, the abiotic synthesis of RNA from its monomers is a central step. We found that in alkaline, drying conditions in bulk and at heated air-water interfaces, 2′,3′-cyclic nucleotides oligomerised without additional catalyst, forming up to 10-mers within a day. The oligomerisation proceeded at a pH range of 7–12, at temperatures between 40–80 °C and was marginally enhanced by K⁺ ions. Among the canonical ribonucleotides, cGMP oligomerised most efficiently. Quantification was performed using HPLC coupled to ESI-TOF by fitting the isotope distribution to the mass spectra. Our study suggests a oligomerisation mechanism where cGMP aids the incorporation of the relatively unreactive nucleotides C, A and U. The 2′,3′-cyclic ribonucleotides are byproducts of prebiotic phosphorylation, nucleotide syntheses and RNA hydrolysis, indicating direct recycling pathways. The simple reaction condition offers a plausible entry point for RNA to the evolution of life on early Earth.