Studies On Synthesis And Higly Enantioselective Recognition Of (S)-BINAM-based Fluorescence Sensor

Investigations on highly sensitive and selective enantioselective recognition of chiral organic molecules have received increasing attention in recent years. In particular, numerous efforts have devoted to the design of novel chiral fluorescence sensors with unique electrical and optical properties that are capable of detecting chiral molecule enantioselectivity in a both real-time and reversible fashion due to its importance for understanding the interactions of biological molecules, developing useful separation processes, designing of asymmetric catalysis systems and screening high-throughput chiral catalyst. Moreover, chiral fluorescence sensors can not only greatly facilitate rapid determination of enantiometric composition of chiral compounds with high sensitivity and waste reduction, but also easily achieve high-throughput screening (HTS) determination. The chirality of2,2’-binaphthyldiamine (BINAM) is derived from the restricted rotation of the two naphthalene rings. The rigid structure and C2symmetry of the chiral binaphthyl molecules can play an important role in inherently chiral induction. In this paper, we designed a novel fluorescence polymer sensor incorporating (S)-BINAM-based Schiff base moieties in the polymer main chain backbone. The resulting polymer sensor can form in situ1:1Zn(II)-containing chiral polymer complex which can serve as a fluorescence sensor for highly enantioselective recognition of N-Boc-protected alanine.First chapter, we carefully checked recent research work on fluorescence sensors and described the sensor structure feature, highly selective recognition behavior towards metal ions and chiral molecule enantiomers.Second chapter, we designed and synthesized a chiral conjugated polymer P-l incorporating (S)-BINAM moieties in the main chain by a six-step reaction starting from hydroquinone product. The corresponding chiral polymer P-2could be obtained by the reduction reaction of P-1with NaBH4. Both P-l and P-2were characterized by NMR, MS, IR, CD, TGA and so on.Third chapter, we studied the fluorescence properties of chiral (S)-BINAM-based polymer. The chiral polymer P-l can act as the "turn-on" fluorescent sensor only for Zn"+. We further investigated the fluorescence response behaviors of chiral polymer P-l sensor towards Boc-D-Ala and Boc-L-Ala by using (S)-BINAM-based chiral polymer and in situ generated1:2Zn(II)-containing polymer complex. No obvious fluorescence response changes and enantioselectivities can be observed by adding Boc-D-Ala and Boc-L-Ala. Interstingly, the in situ generated1:1Zn(II)-containing polymer complex used as the fluorescence sensor can exhibit the remarkable fluorescence enhancement response and high enantioselectivite recognition towards N-Boc-L-protected alanine. More importantly, the chiral polymer complex sensor solution can appear bright blue fluorescence color change upon addition of (L)-N-Boc-protected alanine under a commercially available UV lamp, which can be clearly observed by the naked eye for direct visual discrimination in a lower concentration. This work can be applied for detection of chiral molecule enantiomers by a simple, rapid and sensitive method.