(137e) Sustainable Condensations On the Early Earth: Prebiotic Peptide Coupling in Formamide

The transition from a chemical inventory of diverse monomers to functional biopolymers is an important topic in understanding the emergence of life on Earth. Chemical evolution can also yield valuable clues for Green Chemistry.  Alternative solvents (solvents other than water) have been proposed as a means of accessing the condensation reactions necessary for monomer coupling by both concentrating reactants and providing a dehydrated environment.  Formamide,prebiotically abundant, has been proposed as an alternative solvent and was used to investigate amino acid condensations using glycine and β-alanine.  Three conditions (open, closed, and cycling) were studied to understand the impact of being exposed to different environments on the early Earth.  The cycling system was found to best promote oligomer formation, but with low conversions 1-2% dimer.  Formylation is a competing side reaction that occurs in formamide, blocking the N-terminus of the amino acid and preventing condensation, especially to diketopiperazines. Estimated thermodynamic and kinetic parameters can be used to model the formation of larger oligomers and show the importance of free amino acid equilibrium in producing longer oligomers.