Mechanism of the dehydration of N-acetyl-d-glucosamine into N-containing platform molecule 3-acetamido-5-acetylfuran: NMR study

Abstract

This study proposed that the preparation of 3-acetamido-5-acetylfuran (3A5AF), a versatile platform molecule, from N-acetyl-d-glucosamine (GlcNAc) catalyzed by boric acid (B(OH)3) and 1-allyl-3-methylimidazolium chloride ([AMim]Cl). Herein, the mechanism was investigated by primary nuclear magnetic resonance (NMR) technology. The catalytic interactions between [AMim]Cl/B(OH)3 and GlcNAc were investigated by 1H, 13C &35Cl chemical shift titration. In addition, 13C1-labelled GlcNAc and various NMR techniques were exploited to characterize the reaction at the molecular level and detect the reaction intermediates. The results revealed that the chloride ion and the boron complex of GlcNAc with B(OH)3 probably play crucial roles and are responsible for a synergic catalytic effect in the process. The intermediates, 2-acetamido-2,3-dideoxy-d-erythro-hex-2-enofuranose (Chromogen I) and 3-acetamido-5-(1′,2′-dihydroxyethyl)furan (Chromogen III), were recognized by NMR and further confirmed with the aid of ESI-mass spectroscopy. On the basis of these studies a reaction pathway could be proposed.