PREPARATION OF HIGH POLYMERS FROM 1,6-ANHYDRO-2,3,4-TRI-0-SUBSTITUTED BETA-D-GLUCOPYRANOSE
PREPARATION OF HIGH POLYMERS FROM 1,6-ANHYDRO-2,3,4-TRI-0-SUBSTITUTED BETA-D-GLUCOPYRANOSE
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DOI：
10.1021/jo01345a035
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发表时间：
1966-01-01
影响因子：
3.6
通讯作者：
SCHUERCH, C
中科院分区：
文献类型：
--
作者：
RUCKEL, ER;SCHUERCH, C
三种1, 6-脱水-2, 3, 4-三-O-取代/3-n-吡喃葡萄糖单体（甲基、乙基和苄基）在路易斯酸催化剂下成功进行了阳离子聚合，并产生了聚合度高达300的高度有规立构聚合物。所有聚合均使用高纯度单体和高真空技术进行。最佳反应条件包括避免链转移的低温和相对高浓度的五氟化磷作为催化剂。最佳催化剂浓度随单体的不同而变化。假定可聚合单体具有三烷基氧鎓离子机理。聚合物的多分散性似乎反映了可变的引发速率和增长速率。后者可能是由抗衡离子的差异引起的。五氟化磷不能聚合1, 6-脱水-2, 3, 4-三-0-乙酰基-/3-D-吡喃葡萄糖。相反，形成了稳定的催化剂单体络合物，该络合物在高催化剂浓度下从溶液中沉淀出来。 1, 6-脱水-2, 3, 4-三-0-三氟乙酰基和2, 3, 4-三-O-三甲基甲硅烷基单体未能显现出在所有成功聚合期间观察到的黄绿色，并且这被认为是反应性氧鎓离子的特征。因此，单体聚合失败似乎是在某些情况下不可聚合的官能团与路易斯酸竞争的结果，而在其他情况下是空间或电子效应。在过去的4或5年中，人们致力于化学合成具有确定组成的特定多糖。 1, 2 对这个问题的兴趣不仅来自合成的挑战，而且还来自这些聚合物在医学中的使用以及作为研究涉及大分子的生理过程的模型物质。 1 23 4右旋糖酐是与当前工作最密切相关的多糖，作为血浆替代品具有众所周知的价值，并且最近被发现可以降低血液中的高胆固醇水平。
Cationic polymerization of three 1, 6-anhydro-2, 3, 4-tri-O-substituted/3-n-gIucopyranose monomers(methyl, ethyl, and benzyl) was successful with Lewis acid catalysts and resulted in highly stereoregular polymers with degrees of polymerization as high as 300. All polymerizations were performed using high purity monomers and high vacuum technique. Optimum conditions of reaction included low temperature to avoid chain transfer and relatively high concentrations of phosphorus pentafluoride as catalyst. The optimum catalyst concen-tration varied with monomer. A trialkyl oxonium ion mechanism is postulated for the polymerizable monomers. The polydispersity of the polymers appears to reflectboth variable initiation and propagation rates. The latter may be caused by differences in counter ion. Phosphorus pentafluoride failed to polymerize 1, 6-anhydro-2, 3, 4-tri-0-acetyl-/3-D-glucopyranose. Instead, a stable catalystAnonomer complex formed which precipitated from solution at high catalyst concentration. l, 6-Anhydro-2, 3, 4-tri-0-trifluoroacetyl and 2, 3, 4-tri-O-trimethylsilyl monomers failed to develop the yellow-green color observed during all successful polymerizations and which is believed to be characteristic of the reactive oxonium ions. Failure for a monomer to polymerize appears, therefore, to be the result of competition for the Lewis acid by nonpolymerizable functional groups in some cases, and in others steric or electronic effects.During thepast 4 or 5 years much effort has been directed toward the chemical synthesis of specific poly-saccharides having a definite composition. 1, 2 Interest in the problem has been generated notonly by the challenge of the synthesis, but also by the use of these polymers in medicine and as model substances for the study of physiological processes involving macromole-cules. 1 23 4Dextrans, the polysaccharides to which the present work is most closely related, have a well-known value as blood plasma substitutes and very recently have been found to reduce high cholesterol levels in the blood.