Cyclodextrin as Macrocyclic Monomer. Synthesis of Polysaccharide by Its Ring-Opening Polymerization

1.α-、β-和γ- o -过甲基化环糊精（mecd）作为大环单体，通过阳离子开环聚合得到线性聚葡萄糖。这三种mecd的相对反应活性不同寻常：环应变较小的单体具有较高的反应活性，其反应活性按α、β和γ的顺序递增。这是由于CD的独特形状；2 .传播端必须进入CD腔内以打开CD环，因此具有较大环尺寸的单体更适合聚合。在适当的聚合条件下，γ-MeCD聚合产生的葡聚糖分子量分布具有较大的间隔（=1633，MW）。官能化引发剂与活化剂的结合，在一定程度上进行MeCD的聚合，得到端官能化葡聚糖。MeCD和THF可共聚生成相应的杂化聚合物。在葡萄糖单元的C6羟基上选择性修饰的mecd也是可聚合的。成功制备了C2单改性mecd，并进行了聚合反应。

1.α-,β-,and γ-O-permethylated cyclodextrins (MeCDs) were found to act as macrocyclic monomers and undergo cationic ring-opening polymerization giving linear polyglucopyranose.2.The relative reactivity of these three MeCDs is unusual : the monomer having the smaller ring-strain has the higher reactivity, which increases in an order of α,β,and γ. This is due to the unique shape of CD ; the propagating end has to go into the CD cavity to open the CD ring, so that the monomer having the larger ring size is preferable for the polymerization.3.The polymerization of γ-MeCD under appropriate conditions produces a unique glucan having large intervals (=1633,MW of γ-MeCD) in the molecular weight distribution.4.The combination of a functionalized initiator with an activator conducts the polymerization of MeCD to give the end-fuctionalized glucan to some extent.5.MeCD and THF are copolymerizable to yield the corresponding hybrid polymer.6.MeCDs selectively modified at the C6 hydroxy groups of the glucose units are also polymerizable.7.The C2 mono-modified MeCDs are successfully prepared and subjected to the polymerization.