Ricci Andreina, Di Rienzo Brunella, Pepi Federico, Troiani Anna, Garzoli Stefania, Giacomello Pierluigi
Department of Mathematics and Physics, Second University of Naples, via Vivaldi, 43-81100, Caserta, Italy.
J Mass Spectrom. 2015 Jan;50(1):228-34. doi: 10.1002/jms.3525.
Understanding on a molecular level the acid-catalysed decomposition of the sugar monomers from hemicellulose and cellulose (e.g. glucose, xylose), the main constituent of lignocellulosic biomass is very important to increase selectivity and reaction yields in solution, key steps for the development of a sustainable renewable industry. In this work we reported a gas-phase study performed by electrospray triple quadrupole mass spectrometry on the dehydration mechanism of D-glucose. In the gas phase, reactant ions corresponding to protonated D-glucose were obtained in the ESI source and were allowed to undergo collisionally activated decomposition (CAD) into the quadrupole collision cell. The CAD mass spectrum of protonated D-glucose is characterized by the presence of ionic dehydrated daughter ion (ionic intermediates and products), which were structurally characterized by their fragmentation patterns. In the gas phase D-glucose dehydration does not lead to the formation of protonated 5-hydroxymethyl-2-furaldehyde, but to a mixed population of m/z 127 isomeric ions. To elucidate the D-glucose dehydration mechanism, 3-O-methyl-D-glucose was also submitted to the mass spectrometric study; the results suggest that the C3 hydroxyl group plays a key role in the reaction mechanism. Furthermore, protonated levulinic acid was found to be formed from the monodehydrated D-glucose ionic intermediate, an alternative pathway other than the known route consisting of 5-hydroxymethyl-2-furaldehyde double hydration.
从分子层面理解半纤维素和纤维素（如葡萄糖、木糖）中糖单体的酸催化分解，对于提高木质纤维素生物质的主要成分在溶液中的选择性和反应产率非常重要，这是可持续可再生工业发展的关键步骤。在这项工作中，我们报道了通过电喷雾三重四极杆质谱对D -葡萄糖脱水机理进行的气相研究。在气相中，在电喷雾电离（ESI）源中获得了与质子化D -葡萄糖对应的反应物离子，并使其在四极杆碰撞池中进行碰撞活化分解（CAD）。质子化D -葡萄糖的CAD质谱以离子脱水子离子（离子中间体和产物）的存在为特征，通过它们的碎裂模式对其结构进行了表征。在气相中，D -葡萄糖脱水不会导致质子化5 -羟甲基 - 2 -糠醛的形成，而是形成了m/z 127异构离子的混合群体。为了阐明D -葡萄糖的脱水机理，还对3 - O -甲基 - D -葡萄糖进行了质谱研究；结果表明C3羟基在反应机理中起关键作用。此外，发现质子化乙酰丙酸是由单脱水D -葡萄糖离子中间体形成的，这是一条不同于已知的由5 -羟甲基 - 2 -糠醛双水合组成的途径的替代途径。
