Amino acid based natural deep eutectic solvents: An efficient catalyst and solvent for N-acetyl-D-glucosamine conversion into organonitrogen chemicals

Organonitrogen chemicals are widely used and in great demand in the food, pharmaceutical and chemical industries. Hence, it is important to develop green and efficient synthesis paths to organonitrogen chemicals for their use as new resources. Herein, we propose the preparation of organonitrogen chemicals from chitin biomass monomer N-acetyl-D-glucosamine (GlcNAc) promoted by natural deep eutectic solvents (NADESs). The selective generation of 3-acetamido-5-(1′,2′-dihydroxyethyl) furan (Chromogen III) and 3-acetamido-5-acetylfuran (3A5AF) from GlcNAc was achieved by the design of NADESs components. GlcNAc reacts in binary NADES proline-glycerol (Pro-Gly) to generate 26 % of Chromogen III and 39 % of 3A5AF in ternary NADES proline-glycerol-lactic acid (Pro-Gly-LA). In addition, the intermolecular hydrogen bonds in NADESs were confirmed through ¹H diffusion-ordered spectroscopy (DOSY) NMR technology. And the results of ¹³C NMR chemical shift titration indicated interaction between NADESs and the C3 and C6 position of GlcNAc. Based on the NMR experiments a mechanism is proposed.