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  • 13C MAS NMR  (1)
  • Acenaphthylene  (1)
  • Amino acids  (1)
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  • 1
    ISSN: 1573-5079
    Keywords: 13C MAS NMR ; EPR ; FTIR ; spheroidene ; stable isotope labelling ; ubiquinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this minireview the information at the atomic level that has been obtained by studying photosynthetic reaction centers with site-directed isotope labelling is discussed. The required isotopically labelled RCs are prepared using isotopically labelled amino acids and cofactors that have been prepared via organic total synthetic chemistry. In some cases the results of isotopically labelled RCs that are prepared via other methods are also discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1907-1914 
    ISSN: 1434-193X
    Keywords: Reductive alkylation ; Acenaphthylene ; Carbanions ; Polycycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dianion of acenaphthylene can be converted into the 5-hydroanion by protonation with one equivalent of methanol. Subsequent reaction with electrophiles such as allyl bromide and propargyl bromide occurs selectively at position 1, resulting in the formation of the novel 1-allylacenaphthene and 1-propargylacenaphthene. In addition to what was observed in the case of methyl iodide, the hitherto unknown 1,1-dialkylated acenaphthene derivatives are formed as minor products; probably the lower reactivity of the unsaturated bromides is responsible for this side reaction. From the products of the reactions with 3,3-dimethylallyl bromide and (bromomethyl)cyclopropane the mechanism was found to be SN2. Reaction of the hydroanion with benzyl bromide takes place at position 1 as well as at position 2a. The reactivity of carbon 2a towards the soft electrophile benzyl bromide is attributed to the high HOMO coefficient at this position.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-193X
    Keywords: Amino acids ; Isotopic labelling ; Ethyl benzoate ; Benzonitrile ; Sodium phenylpyruvate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic route to stable-isotope-substituted L-phenylalanine is presented, which allows the introduction of 13C, 15N, and deuterium labels at any position or combination of positions. For labelling of the aromatic ring, a synthetic route to ethyl benzoate (or benzonitrile) has been developed, based on the electrocyclic ring-closure of a 1,6-disubstituted hexatriene system, with in situ aromatization by elimination of one (amino) substituent. Several important (highly isotopically enriched) synthons have been prepared, namely benzonitrile, benzaldehyde, ethyl benzoate, and ethyl diphenyloxyacetate. Labelled L-phenylalanines have been synthesized from both aromatic precursors by initial conversion into sodium phenylpyruvate and subsequent transformation of this intermediate into the L-α-amino acid by an enzymatic reductive amination reaction. In this manner, highly enriched phenylalanines are obtained on the 10-gram scale and with high enantiomeric purities (≥ 99% ee). The method has been validated by the synthesis of [1′-13C]-L-Phe and [2-D]-L-Phe. In addition, two methods are described for the introduction of isotopes into L-tyrosine starting from the isotopically enriched precursors benzonitrile and ethyl benzoate.
    Type of Medium: Electronic Resource
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