New Deep Eutectic Solvents Based on Urea and Amino Acids in Efficient Syntheses of N-Carbamoylamino Acids

It is shown that the mixture of urea with certain ratios of KOH (in contrast to NaOH, LiOH, and other alkalis), forms liquid eutectic mixtures similar to deep eutectic solvents (DES), which rapidly react with L-amino acids, yielding chiral N-carbamoylamino acids with high yields. At the same time, amino acid esters and aromatic amines do not enter into this reaction. DFT methods were used to confirm the proposed mechanism of carbamoylation of amino acids in discovered conditions. Molecular dynamics and DFT methods were used to investigate the structure of the obtained DES and explain why only KOH, but not other alkalis, forms liquid eutectic mixtures with urea.