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  • 1
    Electronic Resource
    Electronic Resource
    Hydrierung prochiraler Olefine mit Rhodium-Komplexen von optisch aktiven Amidinen (1980)
    Springer
    Monatshefte für Chemie 111 (1980), S. 275-287 
    Details
    ISSN: 1434-4475
    Keywords: Catalytic asymmetric hydrogenation ; Optical induction ; Rh/amidine complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract [RhCl(C8H14)2]2 together with the optically active amidines C6H5C(=NR)NHCH(CH3) (C6H5) I–V or their Li derivatives after activation with molecular hydrogen gives catalysts which at room temperature and 1.1 bar H2-pressure hydrogenate the prochiral substrates (Z)-α[N-acetylamino]-cinnamic acid, itaconic acid, α-methylcinnamic acid, α-methylcinnamic aldehyde, and α-methylcinnamic alcohol as well as cyclohexene, benzene and toluene. Good hydrogenation activity of the new catalysts is in contrast to low optical induction which only in the hydrogenation of α-methylcinnamic alcohol with 1.5 to 2% leads to values different from zero.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938734
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of optically active michael adducts via chiral enamines (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 1161-1167 
    Details
    ISSN: 1434-4475
    Keywords: Michael Addition ; Enamines ; 1,3-Dicarbonyl compounds ; Optical induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Chirale Enamine, durchSchiffbasenkondensation aus 1,3-Dicarbonylverbindungen und (R)-(+)-1-Phenylethylamin erhalten, gehen mit α,β-ungesättigten Carbonylverbindungen diastereoselektiveMichaelreaktionen ein. Nach hydrolytischer Abspaltung des chiralen Hilfsstoffs (R)-(+)-1-Phenylethylamin werden dieMichaeladdukte in 59–95% optischer Ausbeute isoliert.
    Notes: Abstract Chiral enamines, obtained bySchiff base condensation from 1,3-dicarbonyl compounds and (R)-(+)-1-phenylethylamine, were found to undergo diastereoselectiveMichael reactions with α,β-unsaturated carbonyl compounds. After removal of the chiral auxiliary (R)-(+)-1-phenylethylamine by hydrolysis, theMichael adducts were isolated in 59–95% optical yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809268
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  • 3
    Electronic Resource
    Electronic Resource
    Enantioselektive Cyclopropanierung von 1,1-Diphenylethylen und Diazoessigester mit Kupfer-Katalysatoren (1984)
    Springer
    Monatshefte für Chemie 115 (1984), S. 1237-1254 
    Details
    ISSN: 1434-4475
    Keywords: Catalytic enantioselective cyclopropanation ; Copper (II) catalysts ; Optical induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Copper(II) compounds catalyze the reaction of 1,1-diphenylethylene with diazoacetic acid ethylester. The main product is 2,2-diphenylcyclopropane carboxylic acid ethylester. The formation of the carbene dimerization products fumaric and maleic acid diethylester can be suppressed by the continuous addition of diazoacetic acid ester to 1,1-diphenylethylene. 37 optically active ligands, partly new, were combined with copper(II)-acetate to givein-situ-catalysts. In five cases isolated copper complexes were used as catalysts. The best optical inductions in the formation of 2,2-diphenylcyclopro-pane carboxylic acid ethylester with up to 65.6% ee were achieved withSchiff base ligands, which derive from salicylaldehyde and amino alcohols, obtained from amino acid esters and phenylGrignard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809355
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  • 4
    Electronic Resource
    Electronic Resource
    Asymmetric Catalysis, 105Part 104: Ref.. Stereoselective Hydrogenation of Folic Acid with Immobilized Optically Active Rhodium(I)/Diphosphane Catalysts (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
    Details
    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300109
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  • 5
    Electronic Resource
    Electronic Resource
    Asymmetrische Katalyse, 67. Diastereoselektive Hydrierung der Folsäure mit optisch aktiven Rhodium(I)-Diphosphan-Komplexen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2085-2093 
    Details
    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Immobilized enantioselective rhodium(I)-diphosphane catalysts ; Folic acid ; (6S,S)-Folinic acid ; 5,6,7,8-Tetrahydrofolic acid ; N-5-(menthyloxycarbonyl)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric Catalysis, 67[1]. - Diastereoselective Hydrogenation of Folic Acid with Optically Active Rhodium(I)-Diphosphane ComplexesWith immobilized rhodium(I)-diphosphane catalysts supported on silica gel, the C = N bonds of the pyrazine ring of folic acid (1) are reduced with hydrogen in aqueous solution to give 5,6,7,8-tetrahydrofolic acid. A mixture of the two diastereomers 2a and 3a is obtained with (6S)- and (6R)-configuration, respectively, at the newly formed asymmetric center in the pterine system and (S)-configuration in the L-glutamic acid moiety. The unstable hydrogenation products are derivatized with (-)-menthyl chloroformate. An improved HPLC procedure for the analysis of the products has been developed. By using optically active chelate phosphanes as cocatalysts together with [Rh(cod)Cl]2, a diastereomeric excess of up to 24% of the natural isomer 2a with (6S,S)-configuration is attained in the heterogeneous hydrogenation of folic acid.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250917
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