Synthesis of ¹³C-enriched amino acids with ¹³C-depleted insoluble organic matter in a formose-type reaction in the early solar system

Solvent-soluble organic matter (SOM) in meteorites, which includes life’s building molecules, is suspected to originate from the cold region of the early solar system, on the basis of ¹³C enrichment in the molecules. Here, we demonstrate that the isotopic characteristics are reproducible in amino acid synthesis associated with a formose-type reaction in a heated aqueous solution. Both thermochemically driven formose-type reaction and photochemically driven formose-type reaction likely occurred in asteroids and ice-dust grains in the early solar system. Thus, the present results suggest that the formation of ¹³C-enriched SOM was not specific to the cold outer protosolar disk or the molecular cloud but occurred more widely in the early solar system.