Abstract
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.