Polymer Research Institution, Sichuan University, Chengdu, Sichuan, China.
Carbohydr Res. 2011 Sep 27;346(13):1973-7. doi: 10.1016/j.carres.2011.06.012. Epub 2011 Jun 16.
The synthesis of branched polysaccharides using naturally occurring materials has been reported since 1975, but applications of branched polysaccharides are relatively limited because of the long and complex modification processes. In this work, a practical and efficient procedure is presented that in one step levoglucosan can be grafted to galactomannan (at 115°C for 15h) with monochloroacetic acid as catalyst. The structural characteristics of the resulting substances were investigated by NMR spectroscopy. The MS (molar degree of substitution) of glucose was shown to gradually increase with the increase of the ratio of levoglucosan to galactomannan, and the maximal MS is 0.6. Levoglucosan units are mostly grafted to the C6-OH of the galactosyl residues in galactomannan, and the maximal percentage of the substituted C6-OH of galactosyl residues is 42.2%. The resulting levoglucosan tended to graft to the branching glucosyl residues of copolymers with an increase in MS, and the average length of the branching glucose is 3.6 when MS is 0.6.
自 1975 年以来，已有使用天然材料合成支化多糖的报道，但由于修饰过程漫长而复杂，支化多糖的应用相对有限。在这项工作中，提出了一种实用且高效的方法，可在一步中将左旋葡聚糖接枝到半乳甘露聚糖上（在 115°C 下反应 15 小时），以一氯乙酸作为催化剂。通过 NMR 光谱研究了所得物质的结构特征。结果表明，葡萄糖的 MS（摩尔取代度）随左旋葡聚糖与半乳甘露聚糖比例的增加而逐渐增加，最大 MS 为 0.6。左旋葡聚糖单元主要接枝到半乳甘露聚糖的半乳糖基残基的 C6-OH 上，半乳糖基残基中取代的 C6-OH 的最大百分比为 42.2%。随着 MS 的增加，接枝到共聚物分支葡萄糖基的左旋葡聚糖趋于增加，当 MS 为 0.6 时，分支葡萄糖的平均长度为 3.6。
