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  • Articles  (4)
  • keto esters  (2)
  • Chemistry  (1)
  • Fungal isolate  (1)
  • Aircraft Propulsion and Power
  • 2000-2004  (4)
  • 1
    ISSN: 1573-3904
    Keywords: dipeptide analogues ; epimerization ; imidazolide-derived dipeptides ; keto esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary β-Keto esters derived from dipeptides are prepared by application of common methodologies employed for the synthesis of amino acid-derived β-keto esters; however, epimerization of the C-terminal residue occurred to different extents depending on the method. In imidazolide activated dipeptides, this epimerization is due to the CDI activation step and to the configurational instability of the intermediate imidazolides in different reaction media. Regarding yield and diastereomeric purity, the method of choice proved to be the reaction of dipeptide-derived imidazolide with the potassium salt of malonic half esters in the presence of MgCl2.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-3904
    Keywords: dipeptide analogues ; epimerization ; imidazolide-derived dipeptides ; keto esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract β-Keto esters derived from dipeptides areprepared by application of common methodologiesemployed for the synthesis of amino acid-derivedβ-keto esters; however, epimerization of theC-terminal residue occurred to different extentsdepending on the method. In imidazolide activateddipeptides, this epimerization is due to the CDIactivation step and to the configurational instabilityof the intermediate imidazolides in different reactionmedia. Regarding yield and diastereomeric purity, themethod of choice proved to be the reaction ofdipeptide-derived imidazolide with the potassium saltof malonic half esters in the presence of MgCl2.
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  • 3
    ISSN: 1432-1890
    Keywords: Keywords Arbuscular-mycorrhiza ; Infectivity ; Fungal isolate ; Salt stress ; Symbiotic efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The purpose of this study was to compare the effect of salinity on the symbiotic efficiencies and mycelial infectivity of two arbuscular mycorrhizal fungi (AMF), one isolated from saline soils (Glomus sp.) and the other (Glomus deserticola) from nonsaline soils (belonging to the Estación Experimental del Zaidín collection). Lettuce plants inoculated with either of these two fungi or maintained as uninoculated controls were grown in soil with three salt concentrations (0.25, 0.50 or 0.75 g NaCl kg–1 dry soil). Both AMF protected host plants against salinity. However, when the results of shoot dry weight and nutrient contents were expressed relative to the total length of mycorrhiza formed, it was found that both AMF differed in their symbiotic efficiencies. These differences were more evident at the two highest salt levels. Glomus sp.-colonized plants grew less and accumulated less N and P, whereas they formed a higher amount of mycorrhiza. The mechanism by which Glomus sp. protected plants from the detrimental effects of salt was based on the stimulation of root development, while the effects of G. deserticola were based on improved plant nutrition. The increase in salinity of soil decreased the hyphal growth and/or viability of Glomus sp. to a higher extent than those of G. deserticola since the mycelial network generated by G. deserticola was more infective than that of Glomus sp.
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  • 4
    ISSN: 1434-193X
    Keywords: Cycloadditions ; Carbenes ; Nitrones ; Nitrilimines ; Pyrazolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of tert-butylalkynyl chromium Fischer carbene complex 1 with nitrones 2 affords β-enamino-ketoaldehydes 4 by the light-promoted rearrangement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carbene complexes 19 with nitrilimines 10 yields enantiomerically pure Δ2-pyrazolines with high regio- and diastereoselectivity.
    Additional Material: 3 Ill.
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