苄醚型树枝化碳水化合物的合成与液晶性

Benzyl ether type of dendronized carbohydrates:Synthesis and liquid crystallinity

选取3种不同结构的苄醚型树枝状分子为分枝,以N-乙酰氨基葡萄糖为内核,合成出一类树枝化碳水化物;利用DSC、热台偏光显微镜、XRD和CD/UV光谱等手段研究该类化合物的液晶性,并命名为树状碳水化合物液晶.研究表明,连接有楔形树枝状单元的化合物形成手性柱状六方相或者向列相,连接有锥形树枝状单元的化合物未能如预期形成立方相,而仍然形成手性柱状六方相.超分子手性很可能源于树枝状单元与糖内核的协同自组装,使得树状分子沿着柱轴螺旋式堆砌;而糖环内核则对超分子柱的手性起调控作用,从而避免了外消旋的发生.该类化合物为研究碳水化合物诱导手性超分子聚集体提供了新的思路.

Most of traditional carbohydrate liquid crystals are composed of sugar moiety substituted by n-alkyl chains. There are still quite limited categories in this liquid crystal library. In this study, dendronized carbohydrate liquid crystals were synthesized with N-acetylglucosamine as 6ore unit, and wedge or taper shaped benzyl ether type dendrons as branches. Liquid erystallinity of dendronized carbohydrates was studied by POM, DSC, XRD, CD/UV spectroscopy. Molecules contain wedge shaped dendrons can self-organize into chiral columnar hexagonal phase or achiral nematic phase, while molecules contain taper shaped dendrons still self-organize into chiral columnar hexagonal phase, not however cubic phase as suspected. Supramolecular chirality is most probably derived from a helical arrangement of dendrimers around the cylinder axis, driven by a collaborative self-assembly of carbohydrate core and dendron branches, and the chiral carbohydrate center plays the primary role of selecting the handedness of the helix so as not to be racemization. This novel dendronized carbohydrate liquid crystal may provide inspiration in the study of chiral supramolecular aggregates induced by carbohydrates.