Zur Kenntnis der Sulfite und Sulfithydrate des Eisens und Nickels Röntgenographische,thermoanalytische, IR- und Raman-spektroskopische Untersuchungen

In den Systemen FeSO₃? H₂O und NiSO₃? H₂O konnten folgende Hydrate erhalten werden: α-FeSO₃ · 3H₂O, γ-FeSO₃ · 3H₂O, FeSO₃ · 2,5 H₂O, FeSO₃ · 2 H₂O, NiSO₃ · 6 H₂O, NiSO₃ · 3 H₂O, NiSO₃ · 2,5 H₂O und NiSO₃ · 2 H₂O. Die Gitterdaten der folgenden Hydrate wurden anhand von Einkristallmessungen bestimmt: γ-FeSO₃ · 3 H₂O: a = 965,9(1), b = 557,1(1), c = 944,7(1) pm, Z = 4, FeSO₃ · 2 H₂O (P2₁/n): a = 645,6(1), b = 863,1(1), c = 761,2(1) pm, β = 99,84(1)°, Z = 4, NiSO₃ · 3 H₂O: a = 945,0(1), b = 547,2(1), c = 932,5(1) pm, Z = 4, NiSO₃ · 2,5 H₂O (P4₁2₁2): a = b = 935,3(1), c = 1016,6(1) pm, Z = 8, NiSO₃ · 2 H₂O (P2₁/n): a = 631,4(1), b = 851,0(1), c = 744,7(1) pm, β = 98,91(1)°, Z = 4. Die IR- und Raman-Spektren sowie das Ergebnis thermoanalytischer Messungen (DTA, DTG, Röntgenheizaufnahmen) werden mitgeteilt. Die bei Sulfiten und Sulfithydraten zweiwertiger Metalle bisher beobachteten Strukturtypen werden diskutiert. Sulfites and Sulfite Hydrates of Iron and Nickel. X-ray, Thermoanalytical, I.R., and Raman Data In the systems FeSO₃? H₂O and NiSO₃? H₂O the following hydrates have been found: α-FeSO₃ · 3H₂O, γ-FeSO₃ · 3H₂O, FeSO₃ · 2,5 H₂O, FeSO₃ · 2 H₂O, NiSO₃ · 6 H₂O, NiSO₃ · 3 H₂O, NiSO₃ · 2,5 H₂O and NiSO₃ · 2 H₂O. The following crystal data have been determined by single crystal measurements: γ-FeSO₃ · 3 H₂O: a = 965,9(1), b = 557,1(1), c = 944,7(1) pm, Z = 4, FeSO₃ · 2 H₂O (P2₁/n): a = 645,6(1), b = 863,1(1), c = 761,2(1) pm, β = 99,84(1)°, Z = 4, NiSO₃ · 3 H₂O: a = 945,0(1), b = 547,2(1), c = 932,5(1) pm, Z = 4, NiSO₃ · 2,5 H₂O (P4₁2₁2): a = b = 935,3(1), c = 1016,6(1) pm, Z = 8, NiSO₃ · 2 H₂O (P2₁/n): a = 631,4(1), b = 851,0(1), c = 744,7(1) pm, β = 98,91(1)°, Z = 4. IR, Raman, and thermoanalytical (DTA, DTG, high temperature X-ray) data are presented. The structure types found for sulfites and sulfite hydrates of bivalent metals are discussed.     

Kinetic isotope effect in proton exchange processes between methanol and water in inert solvents

The kinetic isotope effect in proton exchange between methanol and water in CCl₄ solution was studied by¹H and²H NMR and kinetic IR spectroscopy. The exchange rate increases in the series CD₃OH+H₂O3OD+H₂O3OD+D₂O. It has been concluded that the limiting step of the reaction involves the formation of an H-bonded cyclic intermediate.

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¹H ²H - CCl₄. , CD₃OH+H₂O3OD+H₂O3OD+D₂O. , - -.

     

Application of a capillary gas chromatographic-selected-ion recording mass spectrometric technique to the analysis of diethylstilbestrol and its phosphorylated precursors in plasma and tissues

A method for the analysis of diethylstilbestrol (DES) which is suitable for pharmacokinetic studies has been developed using capillary gas chromatographic (GC) separation and detection with selected-ion mass spectrometry (MS). This technique has been applied to a variety of samples including human plasma samples and extracts of animal tissues including prostate and liver. To investigate the pharmacokinetics of stilphostrol (diethylstilbestrol diphosphate) we have modified the GC-MS method in two ways. One modification involves a dual assay for DES; the first a direct assay, and the second after hydrolysis of a sample with alkaline phosphatase. The difference in these values is the amount of phosphorylated DES present. The other modification separates stilphostrol and DES using a reversed-phase, ion-paired high-performance liquid chromatographic method followed by alkaline phosphatase hydrolysis followed by the GC-MS method. The details of these three methods are described and some representative data are shown.     

Clorobiocin biosynthesis in Streptomyces: identification of the halogenase and generation of structural analogs

Clorobiocin (clo) and novobiocin (nov) are potent inhibitors of bacterial DNA gyrase. The two substances differ in the substitution pattern at C-8' of the aminocoumarin ring, carrying a chlorine atom or a methyl group, respectively. By gene inactivation, clo-hal was identified as the gene of the halogenase responsible for the introduction of the chlorine atom of clorobiocin. Inactivation of cloZ did not affect clorobiocin formation, showing that this ORF is not essential for clorobiocin biosynthesis. Expression of the methyltransferase gene novO in the clo-hal(-) mutant led to the very efficient formation of a hybrid antibiotic containing a methyl group instead of a chlorine atom at C-8'. Comparison of the antibacterial activity of clorobiocin analogs with -Cl, -H, or -CH(3) at C-8' showed that chlorine leads to 8-fold higher activity than hydrogen and to 2-fold higher activity than a methyl group.     

Asymmetric induction in mixed [2 + 2] photoadditions employing a chiral auxiliary in the alkene component

Asymmetric induction was achieved in the photoaddition of 3-methyl-2-cyclohexenone to optically active enoates 1a–c and the absolute configuration of the major adduct was determined.     

Structural constraints from proton-mediated rare-spin correlation spectroscopy in rotating solids

A novel solid-state NMR concept is introduced that allows for the detection of through-space proton-proton contacts in high spectral resolution. The proposed method not only can be utilized to infer sequential assignments and backbone or side chain conformation in solid-phase polypeptides, but it also provides information about the three-dimensional arrangement of the molecule of interest. As a result, the molecular structure can be studied without additional restrictions regarding sample labeling or magic angle spinning rates.     

Molecular solutes in nematic liquid crystals: Orientational order and electric field gradients

The difference between liquid-crystal and gas-phase values for the nuclear quadrupole coupling constant in D₂ and HD is used to obtain the mean electric field gradient in various liquid crystals. Order parameters for small molecules dissolved in liquid crystals are calculated assuming that the orientational order arises from the interaction of the molecular quadrupole moment with the average field gradient. The results obtained are in good agreement with experimental values for hydrogen and several other solutes.