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  • 1
    ISSN: 0899-0042
    Keywords: enantiomers ; HPLC ; DNS-animo acids ; fluorescence quenching ; ligand-exchange mechanism ; adsorption ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copper(II) complexes of two new diastereomeric ligands, N2-(R)- and N2-(S)-2′-hydroxypropyl-(S)-phenylalaninamide [(R, S)-1 and (S, S)-1], have been used as additives to the eluent in high-performance liquid chromatography (HPLC) reversed phase for the chiral separation of DNS-amino acids. The aim was that of comparing the separation process obtained by the chiral eluent with that obtained by an analogous bonded stationary phase containing (S)-phenylalaninamide, previously studied [CSP-(S)-Phe-NH2]. The affinity of the ternary complexes for the C18 column was determined by adsorption experiments in HPLC. It was shown that the two systems (chiral eluent, chiral stationary phase) work according to different mechanisms. Ternary complex formation in solution was studied by fluorescence spectroscopy. It was shown that chiral separation with the Cu(II) complexes added to the eluent was determined by the relative affinities of the ternary complexes for the column-stationary phase rather than by their stabilities in solution. With CSP-(S)-Phe-NH2 the separation is accounted for by the relative stabilities of the ternary complexes, which depends mainly on the “allowed” geometry of the complex and on the steric repulsion of the amino acid side chain with the spacer. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. i 
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0899-0042
    Keywords: chiral discrimination ; chiral stationary phase ; alkyl aryl sulfoxides ; quantitative structure-enantioselective retention relationships ; comparative molecular field analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction mechanism of a variety of racemic alkyl aryl sulfoxides with a π-acid HPLC stationary phase containing N,N′-(3,5-dinitrobenzoyl)-trans-1,2-diaminocyclohexane chiral selector was investigated by means of quantum-chemical calculations (MNDO), partial least squares (PLS) analysis, and 3D comparative molecular field analysis (CoMFA). Quantitative structure-enantioselective retention relationships (QSERR), were derived which have yielded significant insights into physicochemical properties primarily responsible for chiral recognition. The increase in retention (k′) is favored especially by the analyte π-basic character, accounted for by the sum of the electrophilic superdelocalizabilities of all aromatic carbon atoms (SPhHOMO), and to minor extent by the H-bond basicity of the sulfoxide oxygen and the hydrophilicity of solutes. In contrast, the separation factor (α) varied mainly with the steric properties of the substituents and with polar and electrostatic properties of the sulfoxide group. A 3D-QSERR analysis using CoMFA methodology has provided a more complete description of factors responsible for chiral recognition and has proven to be a useful tool to examine differences in noncovalent fields (both the electrostatic and the steric) mostly associated with variations of enantioselectivity. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0935-6304
    Keywords: SFC ; μ-HPLC ; Chiral microhore and microcapillary columns ; Enantioseleclive chromatography ; Multicolumns enamtioselective chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New results obtained with microbore or microcapillary columns packed with DACH-DNB CSP (spherical silica, 5 μm) using conventional LC eluents or supercritical fluids are reported. Examples of direct chromatographic separations of complex mixtures of stereo-isomers on: a) long, packed microbore or microcapillary columns and b) several columns coupled in series are shown; in the latter case, a home-made calculation procedure (Simulation for Multi-Column Chromatography-SMCC) was used to quickly select the optimal conditions (kind of stationary phases and relative columns length).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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