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

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.