Product Distribution Control for Glucosamine Condensation: Nuclear Magnetic Resonance (NMR) Investigation Substantiated by Density Functional Calculations
2017
Selective conversion of glucosamine (GlcNH2) to deoxyfructosazine (DOF) and fructosazine (FZ) with additives was investigated. Significantly enhanced yield of DOF can be improved to 40.2% with B(OH)3 as the additive. Chemical shift titration (via one-dimensional nuclear magnetic resonance (1D 1H and 13C NMR)) and two-dimensional nuclear magnetic resonance (2D NMR) including 1H–13C HSQC and 1H–1H COSY are used to investigate intermolecular interactions between B(OH)3 and GlcNH2. Diffusion-ordered NMR spectroscopy (DOSY) was further employed to identify intermediate species. Mechanistic investigation by NMR combined with electron spray ionization–mass spectroscopy (ESI-MS) discloses that a mixed 1:1 boron complex was identified as the major species, shedding light on the promotional effects of B(OH)3, which is substantiated by density functional theory (DFT). Boron coordination effects make ring-opening and subsequent dehydration reaction thermodynamically and kinetically more favorable. Dehydration of dihy...
Keywords:
- Dehydration reaction
- Heteronuclear single quantum coherence spectroscopy
- Fluorine-19 NMR
- Nuclear magnetic resonance spectroscopy
- Carbon-13 NMR
- Nuclear magnetic resonance spectroscopy of nucleic acids
- Two-dimensional nuclear magnetic resonance spectroscopy
- Nuclear magnetic resonance
- Chemistry
- Density functional theory
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