title: Enantioselective Hydrolysis of Amino Acid Esters Promoted by Bis(β-cyclodextrin) Copper Complexes.
abstract: It is challenging to create artificial catalysts that approach enzymes with regard to catalytic efficiency and selectivity. The enantioselective catalysis ranks the privileged characteristic of enzymatic transformations. Here, we report two pyridine-linked bis(β-cyclodextrin) (bisCD) copper(II) complexes that enantioselectively hydrolyse chiral esters. Hydrolytic kinetic resolution of three pairs of amino acid ester enantiomers (S1-S3) at neutral pH indicated that the "back-to-back" bisCD complex CuL(1) favoured higher catalytic efficiency and more pronounced enantioselectivity than the "face-to-face" complex CuL(2). The best enantioselectivity was observed for N-Boc-phenylalanine 4-nitrophenyl ester (S2) enantiomers promoted by CuL(1), which exhibited an enantiomer selectivity of 15.7. We observed preferential hydrolysis of L-S2 by CuL(1), even in racemic S2, through chiral high-performance liquid chromatography (HPLC). We demonstrated that the enantioselective hydrolysis was related to the cooperative roles of the intramolecular flanking chiral CD cavities with the coordinated copper ion, according to the results of electrospray ionization mass spectrometry (ESI-MS), inhibition experiments, rotating-frame nuclear Overhauser effect spectroscopy (ROESY), and theoretical calculations. Although the catalytic parameters lag behind the level of enzymatic transformation, this study confirms the cooperative effect of the first and second coordination spheres of artificial catalysts in enantioselectivity and provides hints that may guide future explorations of enzyme mimics.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Shan-Shan
authors.initials: SS
authors.lastname: Xue
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhao
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Zhuo-Feng
authors.initials: ZF
authors.lastname: Ke
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Bei-Chen
authors.initials: BC
authors.lastname: Cheng
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Hua
authors.initials: H
authors.lastname: Su
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cao
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Zhen-Kun
authors.initials: ZK
authors.lastname: Cao
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
authors.forename: Zong-Wan
authors.initials: ZW
authors.lastname: Mao
mesh_terms: D000596:Amino Acids; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D004952:Esters; D047392:beta-Cyclodextrins; D003300:Copper