text: The starting reactants for these reactions are hydrogen cyanide (HCN) as well as HCN derivatives and acetylene. Both of these are hypothesized to be present on the early Earth. The conditions this reaction occurs in are a relatively moderate temperature of 35 degrees C and in anoxic or oxygen free conditions. The early Earth was anoxic before the great oxidation event, making these conditions plausible. In the laboratory synthesis, a neutral phosphate buffer was used to maintain a stable, neutral pH. hydrogen sulfide (H2S) is used as a reductant in these reactions. The reactions are driven forward by ultraviolet radiation and catalyzed by Cu(I)-Cu(II) photoredox cycling. Some compounds in the system perform multiple roles. For example, phosphate serves as a buffer to maintain a neutral pH, acts as a catalyst in the synthesis of 2-aminooxazole and urea and serves as a reagent in the formation of glycerol-3-phosphate and ribonucleotides.  The mechanisms involved in these reactions include reductive homologation processes to build larger, more complex molecules from the simple starting materials. The products of this reaction include the precursors of many amino acids, the precursors of lipids, and ribonucleotides. It is worth noting that most of the prebiotic monomers are not synthesized in their entirety by these reactions, only their precursors. The amino acid precursors would then be produced by Strecker synthesis reactions. Cyanosulfidic metabolism also does produce the precursors of both purines and pyrimidines ribonucleotides simultaneously. Many of the compounds produced also include intermediates in one-carbon metabolism.