Crucial Role of Oxidation for the Prebiotic Peptide Elongation Promoted by Carbonyl Sulfide

Both the emergence and sustainability of dissipative chemical systems, such as protometabolisms, require a constant flow of free energy, which can, among other possibilities, be provided by chemical activating agents. Several prebiotically plausible candidates have been identified, but none are flawless or even sufficiently efficient to consider this question resolved. This study revisits and extends previous work on amino acid activation and peptide elongation promoted by carbonyl sulfide in aqueous medium which proceeds via the formation of N ‐carboxyanhydrides (NCAs). Through an approach aimed at providing new mechanistic insights, it demonstrates that oxidation of the thiocarbamate adduct is mandatory for subsequent NCA and peptide bond formation and that ferricyanide, as an oxidizing agent example, efficiently promotes the reaction even at mild pH. However, side reactions, such as urea/hydantoin formation, were confirmed to strongly limit the prebiotic scope of this N‐terminal peptide elongation route.