Komaba Institute for Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Institute for Catalysis, Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.
Angew Chem Int Ed Engl. 2023 Jan 16;62(3):e202214229. doi: 10.1002/anie.202214229. Epub 2022 Nov 23.
Oligosaccharides possess fascinating functions that are applicable in a variety of fields, such as agriculture. However, the selective synthesis of oligosaccharides, especially chitin-oligosaccharides, has remained a challenge. Chitin-oligosaccharides activate the plant immune system, enabling crops to withstand pathogens without harmful agrichemicals. Here, we demonstrate the conversion of chitin to chitin-oligosaccharides using a carbon catalyst with weak acid sites and mechanical milling. The catalyst produces chitin-oligosaccharides with up to 94 % selectivity in good yields. Monte-Carlo simulations indicate that our system preferentially hydrolyzes larger chitin molecules over oligomers, thus providing the desired high selectivity. This unique kinetics is in contrast to the fact that typical catalytic systems rapidly hydrolyze oligomers to monomers. Unlike other materials carbons more strongly adsorb large polysaccharides than small oligomers, which is suitable for the selective synthesis of small oligosaccharides.
寡糖具有令人着迷的功能，适用于农业等多个领域。然而，寡糖的选择性合成，特别是壳聚糖寡糖的合成，一直是一个挑战。壳聚糖寡糖激活植物免疫系统，使作物能够抵御病原体而无需使用有害的农用化学品。在这里，我们使用具有弱酸位的碳催化剂和机械研磨将壳聚糖转化为壳聚糖寡糖。该催化剂以良好的收率产生高达 94%选择性的壳聚糖寡糖。蒙特卡罗模拟表明，我们的系统优先水解较大的壳聚糖分子而不是低聚物，从而提供所需的高选择性。这种独特的动力学与典型的催化体系快速将低聚物水解成单体的事实形成对比。与其他材料不同，碳对大的多糖的吸附作用强于小的寡糖，这有利于小寡糖的选择性合成。
