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  • 1
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Components of the Green Deathcap Toadstool, Amanita phalloides, XLIV1). - Configuration of the Hydroxylated Isoleucines from AmatoxinsThe absolute configuration of the γ-hydroxyisoleucine occurring in γ-amanitin has been established by X-ray structure analysis of its lactone hydrobromide as (2S,3R,RS)-2-amino-3-methyl-4-hydroxyvaleric acid (6). This structure, which is different from the 4R-configuration 2 formerly assumed2), is consistent with Hudson′s lactone rule, 1H-NMR spectroscopy (nuclear Overhauser effect), and PFT 13C-NMR analysis. Since the corresponding γ,δ-dihydroxyisoleucine of α-and β-amanitin has been converted into 6 without touching the C-4 atom, this amino acid must now be formulated as (2S,3R,4R)-2-amino-3-methyl-4-5-dihydroxyvaleric acid (8).
    Notes: Durch Röntgenstrukturanalyse seines γ-Lacton-hydrobromids wurde die absolute Konfiguration jenes γ-Hydroxyisoleucins, das im γ-Amanitin vorkommt, als (2S,3R,4S)-2-Amino-3-methyl-4-hydroxyvaleriansäure (6) bestimmt. Diese im Gegensatz zu früher2) als 4R-2 formulierte Konfiguration ist vereinbar mit der Hudsonschen Lactonregel, dem 1H-NMR-spektrum (Nuclear-Overhauser-Effect) und der PFT-13C-NMR-Analyse. Da schon früher das entsprechende γ,δ-Dihydroxyisoleucin des α-und β-Amanitins ohne Berührung von C-4 in 6 übergeführt werden konnte, muß jetzt auch die Strukturformel dieser Aminosäure zu (2S,3R,4R)-2-Amino-3-methyl-1-4,5-dihydroxyvaleriansäure (8) abgewandelt werden.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1973 (1973), S. 560-565 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of α-Amino-γ-hydroxy Acids by PhotochlorinationThe hydrochlorides of γ-lactones (2a-g) of the following amino acids are obtained by photochlorination and subsequent hydrolysis as mixtures of racemates or diastereomers in about 25% yield: DL-α-aminobutyric acid (1a), L-valine (1b), DL-pseudoleucine (1c), DL-norvaline (1d), L-isoleucine (1e), D-allo-isoleucine (1f), and L-leucine (1g). From a mixture of four lactone hydrochlorides obtained from DL-norleucine (1h) under the same conditions, a δ-lactone (2h) was isolated.
    Notes: Durch Photochlorierung in starker Salzsäure und anschließende Hydrolyse werden die γ-Lacton-hydrochloride 2a-g der folgenden α-Aminosäuren z. T. als Racemate oder Diastereomeren-Gemische in ca. 25 proz. Ausbeute erhalten: DL-α-Aminobuttersäure (1a), L-Valin (1b), DL-Pseudoleucin (1c), DL-Norvalin (1d), L-Isoleucin (1e), D-allo-Isoleucin (1f) und L-Leucin (1g). DL-Norleucin (1h) geht unter analogen Bedingungen in ein Gemisch von 4 Lactonen über, aus dem das δ-Lacton 2h isoliert wurde.
    Additional Material: 1 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 33-39 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Facile Racemization of N-Acylated α-Amino-γ-lactonesThe lactones of L-γ-hydroxyamino acids are essential components of all toxins of the green death-cap mushroom, Amanita phalloides. N-Acylated derivatives (2a-g), as α-amino-γ-lactones (type 1), racemize at the α-C atom even under weakly basic conditions on opening the lactone ring and forming the corresponding carboxylate anions (Table 1). Also N-alkoxycarbonyl derivatives racemize under the same conditions, however, N-protected derivatives without a carbonyl group at the amino nitrogen (e. g. trityl, tosyl, etc.) do not. As an explanation for this behaviour, the formation of an intermediate azlactone (1,3-oxazolin-5-one), favoured by the juxtaposition of the acyl and lactone carbonyl groups, is assumed.
    Notes: Lactone von L-γ-Hydroxyaminosäuren sind wesentliche Bausteine sämtlicher Toxine des grünen Knollenblätterpilzes (Amanita phalloides). Als N-acylierte Derivate (2a-g) racemisieren diese α-Amino-γ-lactone vom Typ 1 am α-C-Atom bereits unter schwach basischen Bedingungen bei der Lactonringöffnung und Bildung der Carboxylatanionen (Tab. 1). Entsprechendes gilt für die N-Alkoxycarbonylabkömmlinge, nicht dagegen für N-geschützte Derivate ohne Carbonylgruppe am Aminostickstoff (z. B. Trityl, Tosyl u. a.). Als Erklärung für dieses Verhalten wird die durch Nachbarstellung der Acyl- und Lactoncarbonylgruppen begünstigte intermediäre Bildung eines Azlactons (1,3-Oxazolin-5-ons) angenommen.
    Additional Material: 1 Tab.
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