Enantioselective chromatography studies

Hamende, M. (2005) Case study in production-scale mulhcolumn continuous chromatography, in Preparative Enantioselective Chromatography, 1st edn (ed. G. Cox), Wiley-Blackwell, Hoboken NJ, p. 253. 

In order to achieve a true comparison between both catalytic systems, colloidal and molecular, which display very different reaction rates, a series of experiments were carried out with the homogeneous molecular system, decreasing the catalyst concentration in the studied allylic alkylation reaction. The reaction evolution is monitored taking samples at different reaction times and analysing each of them by NMR spectroscopy (to determine the conversion) and HPLC chromatography with chiral column (to determine the enantioselectivity of I and II). For molecular catalyst systems, the Pd/substrate ratio was varied between 1/100 and 1/10,000. For the latter ratio, the initial reaction rate was found comparable to that of the colloidal system (Figure 2a), but interestingly the conversion of the substrate is quasi complete after ca. 100 h in... 

S. Allenmark, A. Ohlsson, Enantioselectivity of Lipase-Catalyzed Hydrolysis of Some 2-Chloroethyl 2-Arylpropanoates Studied by Chiral Reversed-Phase Liquid Chromatography , Chirality 1992, 4, 98-102. 

Despite the long recognition of chirality in POPs, it has only been fairly recently that studies of chiral POPs have been possible, after the introduction of analytical technology for stereoisomer separation by enantioselective gas chromatography (GC), high performance liquid... 

Skopp, S. Oehme, M. Drenth, H., Study of the enantioselective elintination of four toxaphene congeners in rat after intravenous administration by high resolution gas chromatography negative ion mass spectrometry Chemosphere 2002, 46, 1083-1090. 

Karlsson, A. et al. Enantioselective Ion-Pair Chromatography of Phenolic 2-Dipropylam-inotetrahn Derivatives on Achiral Stationary Phases an Experimental and Theoretical Study of Chiral Discrimination. Acta Chem. Scand. 1993,47,469-481. 

The potency of enantioselective gas chromatography became apparent in the pharmacokinetic studies of flecainide [3] and two of its chiral metabolites as carried out by Fischer et al. (40). Trace amounts of these compounds in plasma samples were screened for enantiomeric discrimination. 

Lipkowitz, K.B.,Theoretical studies in molecular recognition enantioselectivity in chiral chromatography, /. Comput. Chem.l9S9, 10(5), 718-732. 

There are many other useful analytical methods. Chromatographic methods such as gas chromatography (GC) and high-performance liquid chromatography (HPLC) are used daily for identification and estimation of the purity of a synthetic product. Chiroptical methods, such as circular dichroism (CD) spectroscopy, are also important especially in studying the relationships between absolute configuration and bioactivity of biofunctional molecules. In later chapters I will give some examples of application of CD spectroscopy in enantioselective synthesis. 

The development of stable enantioselective stationary phases for gas chromatography (based mostly on modified cyclodextrins) has permitted the detailed study of the enantiomeric compositions of terpenoids and a host of other... 

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