1. Structure of a Dimeric BINOL-Imine-Zn(II) Complex and Its Role in Enantioselective Fluorescent Recognition
Kai Guo, Ping Wang, Wanli Tan, Yan Li, Xiaowei Gao, Qin Wang, Lin Pu Inorg Chem. 2020 Dec 21;59(24):17992-17998. doi: 10.1021/acs.inorgchem.0c02330. Epub 2020 Nov 2.
A pyridine containing BINOL-based aldehyde (S)- or (R)-4 is found to show highly enantioselective fluorescent response toward phenylglycinol in the presence of Zn2+. A chirality matched dimeric BINOL-imine-Zn(II) complex is isolated from the reaction of (S)-4 with l-phenylglycinol and Zn2+ whose structure is established by X-ray analysis. Comparison of the structure of this SS-complex with a molecular modeling structure of the chirality mismatched SR-complex generated from the reaction of (S)-4 with d-phenylglycinol has provided important insight into the origin of the observed highly enantioselective fluorescent response. It is found that the solvent-accessible surface area of the chirality-matched SS-complex is much smaller than that of the chirality mismatched SR-complex, which gives the more tightly packed and structurally rigid SS-complex with greatly enhanced fluorescence.
2. Novel Chiral Thiourea Derived from Hydroquinine and l-Phenylglycinol: An Effective Catalyst for Enantio- and Diastereoselective Aza-Henry Reaction
Jingdong Wang, Yuxin Liu, Zhonglin Wei, Jungang Cao, Dapeng Liang, Yingjie Lin, Hai-Feng Duan ACS Omega. 2021 Feb 18;6(8):5812-5824. doi: 10.1021/acsomega.0c06233. eCollection 2021 Mar 2.
A series of chiral thiourea bearing multiple H-bond donors derived from hydroquinine has been reported. The aza-Henry reaction of isatin-derived ketimines and long-chain nitroalkanes catalyzed by these chiral thioureas can achieve high enantioselectivity (78-99% ee) and excellent diastereoselectivity (up to 99:1). This work is the first report on long-chain nitroalkanes as substrates with excellent diastereoselectivity in metal-free catalytic systems.
3. Influence of Helical Structure on Chiral Recognition of Poly(phenylacetylene)s Bearing Phenylcarbamate Residues of L-Phenylglycinol and Amide Linage as Pendants
Chunhong Zhang, Rui Ma, Hailun Wang, Ryosuke Sakai, Toshifumi Satoh, Toyoji Kakuchi, Lijia Liu, Yoshio Okamoto Chirality. 2015 Aug;27(8):500-6. doi: 10.1002/chir.22453. Epub 2015 May 14.
Four poly(phenylacetylene)s (PPA-1~4) bearing phenylcarbamate residues of L-phenylglycinol and amide linkage as pendants were prepared to be used as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC), and the influences of coating solvents, dimethylformamide (DMF) and tetrahydrofuran (THF), which were used for coating the polymers on silica gel, on the helical structure of the polymers and their chiral recognition abilities were investigated. The structure analysis of PPA-1~4 by (1) H nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), optical rotation, and circular dichroism (CD) spectra indicated that the polymers possess the cis-transoidal structure with dynamic helical conformation. The polymers in THF seem to have shorter conjugated helical main chains along with a tighter twist conformation than those in DMF. The chiral recognition abilities of PPA-1~4 with the different helical structures induced by the coating solvents were evaluated as the CSPs in HPLC. The helical structures of PPA-1~4 induced with THF are preferable for chiral recognition for some racemates compared to those induced with DMF, and higher chiral recognition abilities of PPA-1~ were achieved using THF.