Zhou Yanli, Zhang Chunhong, Qiu Yuan, Liu Lijia, Yang Taotao, Dong Hongxing, Satoh Toshifumi, Okamoto Yoshio
Polymer Materials Research Center, Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China.
Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Molecules. 2016 Nov 21;21(11):1583. doi: 10.3390/molecules21111583.
A phenylacetylene containing the l-valine ethyl ester pendant (PAA-Val) was synthesized and polymerized by an organorhodium catalyst (Rh(nbd)BPh₄) to produce the corresponding one-handed helical -poly(phenylacetylene) (PPAA-Val). PPAA-Val showed a unique temperature-triggered switchable helix-sense in chloroform, while it was not observed in highly polar solvents, such as ,'-dimethylformamide (DMF). By heating the solution of PPAA-Val in chloroform, the sign of the CD absorption became reversed, but recovered after cooling the solution to room temperature. Even after six cycles of the heating-cooling treatment, the helix sense of the PPAA-Val's backbone was still switchable without loss of the CD intensity. The PPAA-Val was then coated on silica gel particles to produce novel chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). These novel PPAA-Val based CSPs showed a high chiral recognition ability for racemic mandelonitrile ( = 2.18) and racemic -,'-diphenylcyclohexane-1,2-dicarboxamide ( = 2.60). Additionally, the one-handed helical -polyene backbone of PPAA-Val was irreversibly destroyed to afford PPAA-Val-H by heating in dimethyl sulfoxide (DMSO) accompanied by the complete disappearance of the Cotton effect. Although PPAA-Val-H had the same l-valine ethyl ester pendants as its -isomer PPAA-Val, it showed no chiral recognition. It was concluded that the one-handed helical -polyene backbone of PPAA-Val plays an important role in the chiral recognition ability.
合成了一种含有L-缬氨酸乙酯侧基的苯乙炔（PAA-Val），并通过有机铑催化剂（Rh(nbd)BPh₄）进行聚合反应，生成相应的单手螺旋聚（苯乙炔）（PPAA-Val）。PPAA-Val在氯仿中表现出独特的温度触发可切换螺旋方向，而在高极性溶剂（如N,N'-二甲基甲酰胺（DMF））中未观察到这种现象。通过加热PPAA-Val在氯仿中的溶液，圆二色吸收的符号会反转，但将溶液冷却至室温后又会恢复。即使经过六次加热-冷却处理循环，PPAA-Val主链的螺旋方向仍然可以切换，且圆二色强度不会损失。然后将PPAA-Val涂覆在硅胶颗粒上，制备用于高效液相色谱（HPLC）的新型手性固定相（CSP）。这些基于新型PPAA-Val的CSP对外消旋扁桃腈（α = 2.18）和外消旋N,N'-二苯基环己烷-1,2-二甲酰胺（α = 2.60）表现出高的手性识别能力。此外，通过在二甲基亚砜（DMSO）中加热，PPAA-Val的单手螺旋多烯主链被不可逆地破坏，得到PPAA-Val-H，同时科顿效应完全消失。尽管PPAA-Val-H与其对映异构体PPAA-Val具有相同的L-缬氨酸乙酯侧基，但它没有表现出手性识别能力。得出的结论是，PPAA-Val的单手螺旋多烯主链在手性识别能力中起重要作用。
