Untersuchungen zur Bindungsspezifit?t viraler und bakterieller Sialidasen. Eine neuartige Anwendung der 1H-NMR-Spektroskopie

Ohne Zusammenfassung

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Investigations on the binding specificity of viral and bacterial sialidases. A novel application of ¹H-NMR-spectroscopy

     

Synthesis of a new class of keto-linked bis heterocycles

A new class of keto-linked bis heterocycles have been prepared by 1,3-dipolar cycloaddition of tosyl methyl isocyanide, nitrile imines and nitrile oxides to unsymmetrical bischalcones.     

1,3-Dipolar cycloaddition reactions of vinylcephalosporins with diazoalkanes

The vinylcephalosporin ( 1 ) undergoes a regio- and stereoselective 1, 3 -dipolar cycloaddition with diazomethane to give novel cephalosporins, a 3 -pyrazolinocephem ( 4 ) and a double adduct ( 5 ). The vinylcephalosporin sulphoxide ( 2 ) gives only the pyrazolinocephem ( 7 ). In the reaction with diphenyldiazomethane upon heating the initially formed pyrazolines decompose and cyclopropylcephalosporin ( 9 ) formation takes place. The determination of the structures and stereochemistry of these compounds is also described.     

Reactivity of ketene dithiolates toward alkyl bromides

The reactivity of barbituric/thiobarbituric ketene dithiolates with bromoacetic ester and phenacyl bromide is studied. J. Heterocyclic Chem., (2011).     

Synthesis of a New Class of Arylsulfonylethylsulfonylmethyloxazolines and Thiazolines

A new class of arylsulfonylethylsulfonylmethyl oxazolines and thiazolines were prepared using multistep, one‐pot methodologies exploiting lanthanide alkoxides and under microwave irradiation. The microwave method provides an excellent approach in a single step with high yields.     

Solvent effects on the rate of reaction of Cl2˙− and SO4˙− radicals with unsaturated alcohols

Rate constants have been measured in several aqueous/organic solvent mixtures for the addition reaction of Cl₂^˙? radicals with 2-propen-1-o1 and 2-buten-1-o1 as a function of temperature and with 2, 3-dimethyl-2-butene at room temperature. The rate constants were in the range of 10⁶–10⁹ L mol^?1 s^?1, the activation energies were relatively low (1–10 kJ mol^?1), and the pre-exponential factors varied over the range log A = 7.9 to 9.4. The rate constants (k) decreased (by up to a factor of 30) upon increasing the fraction of organic solvent and log k correlated linearly with the dielectric constant for a given water/organic solvent system, but the lines for the different solvent systems had different slopes. A better correlation of log k was found with a combination of the solvatochromic factor, E_T(30), and the hydrogen-bond donor acidity factor, α. This suggests that the rate of reaction is influenced by the solvent polarity and also by specific solvation of the ionic reactant and product. Solvent effect on the reaction of SO₄^˙? with 2-propen-1-o1 was studied for comparison. © 1993 John Wiley & Sons, Inc.