Enantioselective interactions of aminonitrile dimers

Enantioenrichment of amino acids is essential during the early chemical evolution leading to the origin of life. However, the detailed molecular mechanisms remain unsolved. Dimerization of enantiomers is the first molecular process in the nucleation of deposition and crystallization, which are both essential for enantioenrichment. Here, we report the enantioselective interactions of dimers of chiral intermediates, i.e., aminonitriles, in both gas and water environments based on density functional theory (DFT) and more accurate coupled-cluster (CC) calculations. We show that all the aminonitriles stabilize the homochiral dimer preferentially to the heterochiral dimer in the gas phase, while this trend was not observed in water. The energies of the enantioselective interactions in aminonitriles are substantially lower compared to those in amino acids, especially isovaline. These results suggest that prebiotic enhancements of enantiomeric excess are more likely to occur in amino acids than in the aminonitrile intermediates.