Enantioselective interactions of aminonitrile dimers

Abstract

Enantioenrichment of amino acids is essential during the early chemical evolution leading toward 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 essential for the enantioenrichment. Here, we report the enantioselective interactions of dimers of chiral intermediates, i.e., aminonitriles, both in the gas and water environments based on density functional theory (DFT) and more accurate CCSD(T) calculations. We show that all the aminonitriles stabilize the homochiral dimer compared to the heterochiral dimer in the gas phase, while such a common feature was not obtained in water. The energies of 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 favorable in amino acids than in the aminonitrile intermediates.