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  • 1
    Electronic Resource
    Electronic Resource
    Function of methylcobalamin: coenzyme M methyltransferase isoenzyme II in Methanosarcina barkeri (1993)
    Springer
    Archives of microbiology 159 (1993), S. 530-536 
    Details
    ISSN: 1432-072X
    Keywords: Archaea ; Methanogens ; Trimethylamine metabolism ; Methyltransferases ; Methyl ; coenzyme M ; Methylcobalamin ; Corrinoids ; Vitamin B12
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanosarcina barkeri was recently shown to contain two cytoplasmic isoenzymes of methylcobalamin: coenzyme M methyltransferase (methyltransferase 2). Isoenzyme I predominated in methanol-grown cells and isoenzyme II in acetate-grown cells. It was therefore suggested that isoenzyme I functions in methanogenesis from methanol and isoenzyme II in methanogenesis from acetate. We report here that cells of M. barkeri grown on trimethylamine, H2/CO2, or acetate contain mainly isoenzyme II. These cells were found to have in common that they can catalyze the formation of methane from trimethylamine and H2, whereas only acetate-grown cells can mediate the formation of methane from acetate. Methanol-grown cells, which contained only low concentrations of isoenzyme II, were unable to mediate the formation of methane from both trimethylamine and acetate. These and other results suggest that isoenzyme II (i) is employed for methane formation from trimethylamine rather than from acetate, (ii) is constitutively expressed rather than trimethylamine-induced, and (iii) is repressed by methanol. The constitutive expression of isoenzyme II in acetate-grown M. barkeri can explain its presence in these cells. The N-terminal amino acid sequences of isoenzyme I and isoenzyme II were analyzed and found to be only 55% similar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249031
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  • 2
    Electronic Resource
    Electronic Resource
    Total synthesis of brevetoxin A (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 392 (1998), S. 264-269 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Brevetoxin A is the most potent neurotoxin secreted by Gymnodinium breve Davis, a marine organism often associated with harmful algal blooms known as ‘red tides’. The compound, whose mechanism of action involves binding to and opening of sodium channels, is sufficiently toxic to ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/32623
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  • 3
    Electronic Resource
    Electronic Resource
    Addition von enantiomerenreinen Aminen an aktivierte Olefine, 1. Mitt. Über die Addition an ω;-Nitrostyrol (1998)
    Springer
    Monatshefte für Chemie 129 (1998), S. 1025-1033 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Activated olefins; Stereoelectronic effects; Stereoselectively ; Michael addition; Mechanism.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Bei der Michael-Addition von S-Phenylethylamin und L-Alaninisopropylester an ω-Nitrostyrol sind die nach der b,pl,H-Regel als BB-Produkte zu bezeichnenden Diastereomere erwartungsgemäß thermodynamisch stabiler als die AB-Isomere. Eine höhere Bildungsgeschwindigkeit für die AB-Produkte, wie sie z.B. bei der Addition von Thiolen auftritt, wurde nicht beobachtet.
    Notes: Summary.  In the Michael addition reaction of S-phenylethylamine and L-alanine-isopropylester to ω-nitrostyrene, the diasteromers which are to be named as BB-products according to the b, pl, H-rule are as expected thermodynamically more stable than the AB-products. A higher reaction rate for the formation of the AB products, as it was found e.g. for the addition reaction of thioles, could not be observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010113
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  • 4
    Electronic Resource
    Electronic Resource
    Pheromone, 2. Mitt. Ein Verfahren zur Herstellung von Ketonen und Spiroketalen durch Entschwefelung von Thienylethern (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 185-194 
    Details
    ISSN: 1434-4475
    Keywords: Desulfurization ; Hydrogenation ; Ketones ; Pheromones ; Spiroketals ; Thiphene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Starting from substituted methoxythiophenes1 ketones and spiroketals can be synthesized in one step by desulfurization with partial hydrogenation. The bark beetle pheromone chalcogran2 a and the wasp anti aggression pheromone2 b were prepared by this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809364
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  • 5
    Electronic Resource
    Electronic Resource
    Aminoalkohole, 1. Mitt.: Ein Verfahren zur Synthese enantiomerenreiner 1,2-Aminoalkohole miterythro-Konfiguration (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 283-290 
    Details
    ISSN: 1434-4475
    Keywords: 1,2-Amino-alcohols ; Enantiomerically pure ; erythro-Configuration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of both enantiomers of norephedrine and norisoephedrine is described to present a method for the preparation of enantiomerically pure branched 1,2-aminoalcohols. In a one pot reaction enantiomerically pure cyanohydrins bearing an acetal protective group are subjected to Grignard-reaction followed by addition of lithium aluminum hydride. After deprotection the target compounds are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810829
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  • 6
    Electronic Resource
    Electronic Resource
    [1,2]-Wittig Rearrangement of Acetals III [1]. New 1,2-Alkoxyalcohols, 1,2-Alkoxyaminesand 1,2-Dialkoxy Compounds as Chiral Ligands for Organomagnesium and Organolithium Compounds and forLithium Aluminum Hydride (2000)
    Springer
    Monatshefte für Chemie 131 (2000), S. 867-877 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Acetals; [1 ; 2]-Wittig rearrangement; Ligands ; chiral; Carbonyl addition ; stereoselective.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  Eight O-substituted 1,2-diols and one O,N-substituted 1,2-aminoalcohol derived from 2-alkoxyoctahydro-7,8,8-trimethyl-4,7-methanobenzofurans via a [1,2]-Witting rearrangement and subsequent substitution were synthesized and tested as additives for the enantioselective addition of butyllithium and butylmagnesium chloride to benzaldehyde and for the reduction of acetophenone with lithium aluminum hydride. The selectivity of the reactions was determined by GC of the obtained 1-phenyl-1-pentanol and 1-phenylethanol on a chiral phase. Best results with regard to selectivity (52% ee and 94% ee, resp.) were achieved in the formation of 1-phenyl-1-pentanol by addition of the substituted 1,2-aminoalcohol to the organometallic reagent and in the reduction of acetophenone using an α-alkoxyalcohol (62%ee).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007060070064
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  • 7
    Electronic Resource
    Electronic Resource
    Pheromone, 1. Mitt.: (+)-cis-Disparlure: Synthese und Feldtests (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 101-110 
    Details
    ISSN: 1434-4475
    Keywords: (+)-cis-Disparlure ; Enantioselective synthesis ; Field tests ; Mating disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A synthesis of (+)-cis-disparlure is described starting from racemic 2-hydroxy-dodecannitrile (2), which is transformed into the O-protected enantiomerically pure cyanohydrine4. Grignardreaction followed by reduction with BH3 · (CH3)2S yields the correspondingthreo-configurated secondary alcohol10. After tosylation and cleavage of theMBE-protective-group (+)-cis-disparlure (14) is obtained by treatment with KOH. Mating disruption field tests exhibited a significantly increased effectiveness of (+)-cis-disparlure as compared to the racemic product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00815171
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  • 8
    Electronic Resource
    Electronic Resource
    Acetals as Chiral Ligands for Organomagnesium and Organolithium Compounds (1998)
    Springer
    Monatshefte für Chemie 129 (1998), S. 953-959 
    Details
    ISSN: 1434-4475
    Keywords: keywords.  Acetals; Ligands ; chiral; Carbonyl addition ; stereoselective.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Fünf 2-Alkoxyoctahydro-7,8,8-trimethyl-4,7-methanobenzofurane wurden als Additive für die enantioselektive Addition von Butyllithium bzw. Butylmagnesiumbromid an Benzaldehyd getestet. Die Selektivität der Reaktion wurde mittels GC, HPLC und Messung der optischen Aktivität des erhaltenen 1-Phenyl-1-pentanols bestimmt. Die Stabilität der Liganden unter den gegebenen Reaktionsbedingungen wurde untersucht. Die Addition von Octahydro-7,8,8-trimethyl-2-(2-(phenylmethoxy)ethoxy)-4,7-methanobenzofuran an Butylmagnesiumbromid lieferte nach der Reaktion mit Benzaldehyd (R)-1-Phenyl-1-pentanol mit 47%ee.
    Notes: Summary.  Five 2-alkoxyoctahydro-7,8,8-trimethyl-4,7-methanobenzofurans were tested as additives for the enantioselective addition of butyllithium and butylmagnesium bromide to benzaldehyde. The selectivity of the reaction was determined by GC, HPLC, and by measurement of the optical rotation of the obtained 1-phenyl-1-pentanol, and the stability of the ligands under the given reaction conditions was investigated. Upon reaction with benzaldehyde, the addition of octahydro-7,8,8-trimethyl-2-(2-(phenylmethoxy)ethoxy)-4,7-methanobenzofuran to butylmagnesium bromide yielded (R)-1-phenyl-1-pentanol with 47%ee.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013503
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  • 9
    Electronic Resource
    Electronic Resource
    Aminoalcohols V [1]: A Methodfor the Synthesis of EnantiomericallyPure Ring-Chlorinated Epinephrinesand Norepinephrines (1999)
    Springer
    Monatshefte für Chemie 130 (1999), S. 451-470 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Chloroepinephrine; Chloronorepinephrine; Enantiomeric purity; Hydrogenation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Die Herstellung von enantiomerenreinem 5- und 6-Chlorepinephrin-hydrochlorid bzw. von 6-Chlornorepinephrin-hydrochlorid wird beschrieben. Ausgehend von chlorsubstituierten mit O-Benzyl geschützten Dihydroxybenzaldehydcyanhydrinen, die mit einer enantiomerenreinen acetalischen Schutzgruppe (MBE) am Cyanhydrinsauerstoff derivatisiert sind, erhält man nach LAH-Reduktion und, falls notwendig, N-Schützung und Methylierung die O- und N-geschützen Chlorepinephrine bzw. Chlornorepinephrine. Nach Spaltung des MBE-Acetals und hydrogenolytischer Entfernung der Benzyl- bzw. Benzyloxycarbonylgruppe werden die Zielverbindungen in guter chemischer Ausbeute mit Enantiomerenreinheiten über 96%ee erhalten, wenn bestimmte Reaktionsparameter während der Hydrierung präzise eingehalten werden.
    Notes: Summary.  The synthesis of enantiomerically pure 5- and 6-chloroepinephrine hydrochloride, resp., as well as 6-chloronorepinephrine hydrochloride is described starting from ring chlorinated O-benzylated dihydroxybenzaldehyde cyanohydrins, which are O-protected using an enantiomerically pure acetal-type protecting group (MBE). After lithium aluminum hydride reduction, followed – if necessary – by N-protection and methylation, removal of the chiral auxiliar and deprotection by hydrogenation furnished the target compounds with enantiomeric purities above 96%ee in high chemical yield, if well defined reaction conditions during the hydrogenation process were closely observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010225
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  • 10
    Electronic Resource
    Electronic Resource
    Addition von enantiomerenreinen Aminen an aktivierte Olefine, 2. Mitt. Über die Addition an (E)-4-Oxo-4-phenyl-2-butensäure-ethylester (1999)
    Springer
    Monatshefte für Chemie 130 (1999), S. 769-782 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Activated olefins; Stereoelectronic effects; Stereoselectivity; Michael addition.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary.  The addition of (S)-phenethylamine to ethyl (E)-4-oxo-4-phenyl-2-butenoate shows no kinetic selectivity, whereas – according to the b,pl,H-rule – the AB- and BB-product are kinetically preferred in the addition of (S)-alanine-isopropylester and -benzylester, respectively. In the reaction of benzyl (S)-alaninate, contrary to the other and earlier examined examples no thermodynamic preference for the BB-product over the AB-product was observed.
    Notes: Zusammenfassung.  Die Addition von (S)-Phenethylamin an (E)-4-Oxo-4-phenyl-2-butensäureethylester verläuft ohne kinetische Selektivität. Addiert man hingegen (S)-Alaninisopropylester beziehungsweise benzylester, ist das nach der b,pl,H-Regel als AB- beziehungsweise BB-Produkt zu bezeichnende Diastereomere kinetisch bevorzugt. Bei der Addition von (S)-Alaninbenzylester ist im Unterschied zu den anderen und früher untersuchten Beispielen das BB-Produkt gegenüber dem AB-Produkt thermodynamisch nicht bevorzugt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010259
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