• Title/Summary/Keyword: Chiral ligand

Search Result 51, Processing Time 0.028 seconds

Optical Resolution of Dansyl Amino Acids with Addition of Benzyl-L-Hydroxyproline Copper(II) Chelate by High Performance Liquid Chromatography

  • Sun Haing Lee;Tae Sub Oh;Sang Hyun Bak
    • Bulletin of the Korean Chemical Society
    • /
    • v.10 no.6
    • /
    • pp.491-495
    • /
    • 1989

  • Resolution of enantiomers of DNS-amino acids has been achieved by a reversed phase liquid chromatography with an addition of a copper(Ⅱ) complex of N-benzyl-L-hydroxyproline to the mobile phase. N-Benzyl-L-hydroxyproline was prepared and used as a chiral ligand of copper(Ⅱ) chelate for the optical resolution. The pH and the concentration of copper(Ⅱ) chelate, organic solvent, and buffer agent in the mobile phase all affect the optical resolutions of dansyl amino acids. The elution orders between D and L-DNS-amino acids were different depending on the structure of the side chain of the amino acids. The retention mechanism for the chiral separation of the dansyl amino acids can be illustrated by the equilibrium of ligand exchange and by hydrophobic interaction with $C_{18}$ stationary phase. The chiral separation can be illustrated with cis and trans effect of the ligand exchange reaction.

  • https://doi.org/10.5012/bkcs.1989.10.6.491 인용 PDF

Chiral Mesoporous Silica for Asymmetric Metal-free Catalysis: Enhancement of Chirality thorough Confinement Space by Plug Effect

  • Jeong, Eun-Yeong;Im, Cheong-Rae;Park, Sang-Eon
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2011.08a
    • /
    • pp.199-199
    • /
    • 2011

  • The addition of a carbanion to ${\yen}{\acute{a}}{\yen}{\hat{a}}$-unsaturated carbonyl compounds is of importance in the C-C bond formation reactions for modern pharmaceuticals and organic synthesis. Recently, heterogeneous asymmetric catalysis became more attractive area of research because of the easy recovery and separation of the catalyst from the reaction system. Most of synthetic methods for heterogeneous catalysts were grafting or immobilization of homogeneous catalyst onto the solid supports. Trans-1,2-Diaminocyclohexane(DACH) and L-proline ligands have been enormously used as chiral ligands in several catalytic transformation under homogenous conditions. Our group prepared l-proline functionalized mesoporous silica was synthesized under acidic condition using a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template (EO20PO70EO20, Pluronic P-123, BASF). Furthermore, we successfully directly synthesized trans-1,2 diaminocyclohexane functionalized mesoporous silica by using microwave method. The direct functionalization of chiral ligand into the framework of mesoporous materials is expected to be useful for the heterogeneous asymmetric catalysis. So, we adopt the direct synthesis of chiral ligand functionalized mesoporous silica by using thermal and microwave irradiation. Then, chiral ligand functionalized mesoporous silicas were applied to enantioselective asymmetric catalytic reactions.

  • PDF

Synthesis and Crystal Structure of Cobalt(III) Complex with Chiral Pentadentate Bis-Amide Ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dione$(S,S-prodienH_2)$

  • 이배욱;오창언;도명기
    • Bulletin of the Korean Chemical Society
    • /
    • v.19 no.4
    • /
    • pp.457-462
    • /
    • 1998

  • A chiral pentadentate bis-amide ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dio ne$(S,S-prodienH_2)$ has been synthesized from the reaction of bis(2-aminoethyl)amine(dien) and S-proline, and the structure of $[Co(S,S-prodien)H_2O]ClO_4$ has be en determined by single crystal X-ray diffraction. The geometrical structure of the Co(III) complex has been an αβ -form, where the dien moiety of ligand chelates to a facial in metal center, and the aqua ligand coordinates a cis site to the secondary nitrogen of dien. The Co-N(1), Co-N(3) distances of two amide moiety in S,S-prodien are shorter than the other Co-N(2), Co-N(4), and Co-N(5) distances because of the increased basicity of nitrogen in amide. The complex crystallizes in the monoclinic space group $P2_1$(#4), with a=7.838(1), b=12.675(1), c=9.710(1) Å, β=100.39(1) and z=2. Refinement gives the final R and $R_w$ values of 0.045 and 0.057, respectively for 2130 observed reflections. Based upon the CD and X-ray data, it is identified that the absolute configuration of the αβ -$[Co(S,S-prodien)H_2O]ClO_4$ has a Λ-form.

  • https://doi.org/10.5012/bkcs.1998.19.4.457 인용 PDF