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  • 1
    Electronic Resource
    Electronic Resource
    Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Über die Natur der Isolierungsartefakte von F430, ein Beitrag zur Chemie von F430 und zur konformationellen Stereochemie der Ligandperipherie von hydroporphinoiden Nickel(II)-Komplexen (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1338-1358 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Factor F430 from Methanogenic Bacteria: On the Nature of the Isolation Artefacts of F430, a Contribution to the Chemistry of F430 and the Conformational Stereochemistry of the Ligand Periphery of Hydroporphinoid Nickel(II) ComplexesFactor F430 (1), a coenzyme from methanogenic bacteria, when heated in aqueous solution isomerizes to 12,13-di-epi-F430 (5) via 13-epi-F430 (3). The equilibrium mixture of the three F430 isomers in aqueous phosphate buffer solution (pH 7, 100°) contains 88 % of 5, 8 % of 3, and 4 % of 1 (Scheme 1). The structural assignment for the F430 isomers rests on FAB-MS-, UV/VIS-, 1H- and 13C-NMR spectra of their pentamethyl esters. Chemical proof for the double epimerization at the two chiral centers of F430's ring C was provided by ozonolytic degradation of the di-epimer to give a ring-C-derived succinimide derivative that was shown to be the enantiomer of the one previously obtained by ozonolysis of F430M (see Scheme 2). The two F430 ring-C epimers 3 and 5 are the isolation artefacts described in the earlier F430 literature. F430 is susceptible to autoxidation in air and the product, that absorbs at 560 nm, was shown to be the 12,13-didehydro derivative 8 of F430 by spectroscopic characterization of its pentamethyl ester 9. The dehydrogenation product 8 can be diastereoselectively reduced with Zn in AcOH to give natural F430 as the main product rather than the thermodynamically more stable F430-di-epimer (Scheme 3). In the double epimerization of F430, the two ring-C side chains change from a trans-quasi-diaxial arrangement to the (locally) enantiomorphic position in which the same side chains are again in a trans-quasi-diaxial arrangement. This equilibrium paradox as well as the kinetic diastereoselectivity of the reduction of 12,13-didehydro-F430 (8) are rationalized to be consequences of the general phenomenon documented earlier (see the preceding paper) according to which hydroporphinoid Ni(II) complexes all show a characteristic conformational ruffling of their ligand system due to the tendency of the (small) Ni(II) ion to contract the size of the ligand's central coordination hole (see Fig. 5 and 6).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680527
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  • 2
    Electronic Resource
    Electronic Resource
    Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des porphinoiden Ligandsystems (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 828-865 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Factor F430 from Methanogenic Bacteria: Structure of the Porphninoid Ligand SystemA structure is proposed for F430M, a non-cristalline methanolysis product of isolates of the nickel-containing, porphinoid factor F430 from Methanobacterium thermoautotrophicum.Crucial to the structure determination are five incorporation experiments with M. thermoautotrophicum (strain Marburg) in which the specifically mono-13C-labeled biosynthetic precursors (2-13C), (3-13C), (4-13C)-, (5-13C) ALA (ALA = δ-amino-levulinic acid) and L-(methyl-13C)methionine were incorporated into F430 with high efficiency. The 13C-NMR,-spectra of the specifically labeled F430M samples derived therefrom, together with the UV./VIS. spectral data of F430M, contain all the information necessary for the deduction of the constitution of the F430M chromophore, assuming the established pattern of porphinoid biosynthesis to be operative in F430 biosynthesis. 1H-NMR. spectroscopy and, in particular, 1H-NMR.-NOE-difference spectroscopy corroborates and completes the constitutional assignments and, furthermore, makes possible an almost complete derivation of the molecule's relative configuration. Schemes 3 and 4 summarize the results of 1H-NMR. spectroscopy, presenting them within the context of the proposed structure for F430M. The assignment of absolute configuration implied in the formula is given preference because of F430M's very close structural and (assumed) biosynthetic relationship to sirohydrochlorin and vitamin B12 (with respect to ring C, the assignment is based on degradative evidence).According to the proposed structure, the nickel complex F430M possesses an uroporphinoid (Type III) ligand skeleton with an additional carbocyclic ring and a chromophore system not previously encountered among natural porphinoids. It can be considered to be a (tetrahydro) derivative of the corphin system, combining structural elements of both porphyrins and corrins.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650320
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    Paper (German National Licenses)
    Fulltext
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