Nonequilibrium Synthesis of Glycolamide (NH2COCH2OH), a Precursor to Amino Acids, on Interstellar Nanoparticles.

Complex organic molecules (COMs) are thought to form in cold interstellar environments, yet the chemical routes to key prebiotic precursors remain poorly understood. Glycine, the simplest amino acid, has not been detected in the interstellar medium so far, prompting interest in its structural isomer glycolamide, recently observed toward Sgr B2. Here, we provide the first experimental evidence that glycolamide forms efficiently at cryogenic temperatures via a barrierless carbon-carbon bond coupling between two carbon-centered carbamoyl (ĊONH2) and hydroxymethyl (ĊH2OH) radicals, generated from formamide and methanol in astrophysical ice analogues exposed to cosmic-ray proxies. This radical-radical pathway proceeds within the ices of ice-coated grains over typical dense cloud lifetimes (∼106 years), thus establishing a nonequilibrium mechanism to glycine isomers of astrobiological relevance. Once formed, glycolamide can act as a versatile precursor to amino acids and sugars thereby contributing to the molecular inventory inherited by nascent exoplanetary systems such as Fomalhaut along with Alpha Lyrae and our own.