Enantioselective Synthesis of a Chiral Coordination Polymer with Circularly Polarized Visible Laser

Circular dichroism is known to be the feature of a chiral agent which has inspired scientist to study the interesting phenomena of circularly polarized light (CPL) modulated molecular chirality. Although several organic molecules or assemblies have been found to be CPL‐responsive, the influence of CPL on the assembly of chiral coordination compounds remains unknown. Herein, a chiral coordination polymer, which is constructed from achiral agents, was used to study the CPL‐induced enantioselective synthesis. By irradiation with either left‐handed or right‐handed CPL during the reaction and crystallization, enantiomeric excesses of the crystalline product were obtained. Left‐handed CPL resulted in crystals with a left‐handed helical structure, and right‐handed CPL led to crystals with a right‐handed helical structure. It is exciting that the absolute asymmetric synthesis of a chiral coordination polymer could be enantioselective when using CPL, and provides a strategy for the control of the chirality of chiral coordination polymers.     

Spectroscopic studies on the inclusion interaction of p-sulfonatocalix[6]arene with vitamin B6

The formation of the inclusion complex of p-sulfonatocalix[6]arene (SCX6) with different forms of vitamin B₆ (VB₆) was studied by using fluorescence spectroscopy. VB₆ can exist in one of three forms (the acidic form, neutral zwitterionic form and basic form) depending on pH. The fluorescence intensities of acidic and basic forms of VB₆ remarkably decreased in presence of SCX6. SCX6 preferred to form 1:1 inclusion complexes with acidic and basic forms of VB₆ but hardly form inclusion complex with neutral zwitterionic form. According to the nonlinear curve fitting method, the inclusion constant (K) for the formation of inclusion complexes of acidic and basic forms of VB₆ with SCX6 were evaluated to be 1.4?×?10⁴ and 9?×?10³ L/mol, respectively. The binding affinity of SCX6 towards acidic form is attributed to hydrogen bonds and hydrophobic interaction, furthermore, additional electrostatic interaction also plays a crucial role. The possible inclusion mode was given by ¹H NMR technique.     

Synthesis and antitumor and antibacterial evaluation of fluoroquinolone derivatives(Ⅲ):Mono- and bis-Schiff-bases

To further explore an efficient modified route for the shift from an antibacterial fluoroquinolone to an antitumor one,mono-Schiff bases 6a-6h related to ciprofloxacin C3 carbonylhydrazone and bis-Schiff bases 4a-4h corresponding to C3/C7 carbonylhydrazone/hydrazone attached on a skeleton of ciprofloquinolone were designed and synthesized,and their in vitro antitumor activity against CHO,HL60,L1210 cells and antibacterial activity against Staphylococcus aureus and Escherichia coli were also reported.     

Matched/Mismatched Interactions in Chiral Brønsted Acid-Catalyzed Glycosylation Reactions with 2-Deoxy-Sugar Trichloroacetimidate Donors

The stereochemical outcome of glycosylation reactions of 2-deoxy-sugar trichloroacetimidates promoted by chiral Brønsted acids is shown to be dependent on both the chirality of the catalyst and the configuration of the leaving group. High levels of selectivity (1:16 α:β) can be obtained with (S)-catalysts and an α-trichloroacetimidate donor. Conversely, (R)-catalysts require longer reaction times and provide the product in much lower selectivity (6.6:1 α:β). These observations demonstrate that stereochemical “match” and “mismatch” between donor and acceptor are important factors in chiral Brønsted acid-promoted glycosylations.     

Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.