Conversion of N-Acetylglucosamine to Protected Amino Acid over Ru/C Catalyst

Abstract

Chitin is the most abundant marine biomass, containing nitrogen atoms in its monomer units, N-acetylglucosamine (NAG). Thus, NAG is a potential feedstock for the production of renewable organonitrogen chemicals. Here, we report a synthetic pathway of a widely used standard amino acid in a protected form, acetylglycine (AcGly), from NAG via two steps: conversion of NAG to N-acetylmonoethanolamine (AMEA) and its transformation to AcGly. In the first step, a Ru/C catalyst converts NAG to AMEA in an NaHCO3 aqueous solution under H2 pressure through a retro-aldol reaction and hydrogenation reaction. Model reactions and density functional theory calculations for this reaction have revealed that resonance stabilization of the acetamido group of NAG avoids its isomerization proceeding to side reactions, which is different from glucose regardless of their similar structures. For the second step of the synthesis of AcGly from AMEA under O2 pressure, the same combination of Ru/C and NaHCO3 is applicable. A mechanistic study has shown that the oxidation reaction is not due to autoxidation but by catalysis of Ru/C. Characterization of the Ru catalyst has revealed that the Ru species is present as small hydrous RuO2 clusters with hydroxo, aqua, μ-hydroxo, and μ-oxo ligands in the presence of O2. This species may work as a catalyst for the oxidation of AMEA.

Towards Shell Biorefinery: Advances in Chemical‐Catalytic Conversion of Chitin Biomass to Organonitrogen Chemicals

“…As discussed earlier, NMEA can be produced from NAG via retro-aldol and hydrogenation reactions. [19] Techikawara et al [28] proposed a strategy to produce acetylglycine (glycine in a protected form) from NAG via two steps, as shown in Scheme 8a. Although the structure of NAG is similar to that of glucose, the isomerization of NAG to imine form is much more difficult than that of glucose owing to resonance stabilization of the acetamido group in NAG, which has been evidenced by model reactions and density functional theory calculations, as shown in Scheme 8b.…”

Food Industrial Production of Monosaccharides Using Microbial, Enzymatic, and Chemical Methods

“…However, it is difficult to obtain GlcNAc inexpensively using this method, and the amino group of the molecule is largely enhanced under acid conditions, needing precise control of the reaction. A method in which chitinase and a reverse osmosis membrane were combined was developed for efficient production of GlcNAc [5]. Recently, Zhang et al presented an efficient and integrated affinity adsorption-enzymatic reaction to produce GlcNAc from crude chitin powder [6].…”

Cycloamination strategies for renewable N-heterocycles

“…The employed nitrogen sources can be derived from ammonia, amines/amides pre-prepared by C-N coupling reactions (e.g., reductive amination, aminolysis, and amidation), [32][33][34][35][36] or natural N-reservoirs (e.g., chitin, proteins) for producing amines and derivatives (e.g., glucosamine, N-acetyl-D-glucosamine, amino acids). [37][38][39][40][41] Beginning from the accessible bio-based functional molecules, N-heterocycles can be constructed by C-N and/or C-C bond formation typically via three dominant synthetic routes including intramolecular cyclization, cycloaddition (e.g., aza-Diels-Alder), and multicomponent condensation reactions (Fig. 2).…”