Solvent extraction of sodium picrate with 15-crown-5 into carbon tetrachloride. The determination of the dimer-formation constant of a crown ether-univalent metal salt 1∶1∶1 complex

The theory is derived to determine the dimer-formation constant,K ₂, of a crown ethermetal salt 111 complex in organic solvents of low dielectric constant by solvent extraction. The theoretical predictions are verified experimentally by extraction of sodium picrate (NaA) with 15-crown-5 (15C5) into carbon tetrachloride. All the experiments were conducted at 25°C. The logK ₂ value of the Na(15C5)A complex in carbon tetrachloride has been determined to be 4.05±0.11. Moreover, the partition constant of the complex is calculated.     

Pre-concentration of traces of tin by coprecipitation with yttrium hydroxide for electrothermal atomisation atomic absorption spectrometry

Summary Trace amounts of tin were concentrated by coprecipitation and determined by electrothermal atomisation atomic absorption spectrometry. Yttrium hydroxide coprecipitated quantitatively 0.1–3 g of tin from 50–500 ml of sample solution at pH 9.5–11.2. The atomic absorbance of tin increased about twice by using an impregnated graphite tube with yttrium. The impregnated graphite tube, furthermore, improved the reproducibility of the measurement of tin. A linear calibration graph was obtained in the range of 0.004–0.12 g/ml of tin. Twenty-three foreign ions did not interfere seriously. The method was applicable to the determination of tin in zinc metal.     

Highly Selective Separation of Rhodopsin from Bovine Rod Outer Segment Membranes Using Combination of Divalent Cation and Alkyl(thio)glucoside

The micellization process of bovine rod outer segment (ROS) membranes is investigated utilizing a series of neutral detergents. It is found that when alkyl(thio)glucosides with an appropriate hydrophilic–lipophilic balance (e.g. octylthioglucoside) are used in combination with a divalent cation, rhodopsin is selectively extracted from ROS membranes at a specific detergent-to-membrane ratio. This allows remarkable purification of rhodopsin by a single-step solubilization, because the residual membranes are heavily aggregated in the presence of divalent cation and are therefore easily sedimented by low-speed centrifugation. The absorption spectrum of the supernatant reproducibly exhibits an A₂₈₀/A₅₀₀ value of 1.6, an excellent value that could rarely be obtained by chromatographic purification. The degree of purification also depends on the type of divalent cation included in the solubilization solution; specific binding of IIB-series cations (Zn²⁺ and Cd²⁺) to ROS membranes is suggested to play an important role in the solubilization process. The present result represents a unique example of selective solubilization of a specific membrane protein from highly aggregated membranes.     

Cascade Rearrangement of 5-Cyclopentylidenecyclooctanones

Acid-catalyzed rearrangement of 5-cyclopentylidenecyclooctanone derivatives 9a-c was examined to obtain polyspiropolyquinanes 11a-c, considered to have a unique helical structure, through cascade rearrangement pathways consisting of continuous transannular cyclization followed by successive 1,2-alkyl shifts. The substrates were prepared easily by use of the Wittig or McMurry reaction. Reaction of the 5-cyclopentylidenecyclooctanone (9a) with acid gave the expected dispirotriquinane ketone 11a in high yield. The precise mechanism was elucidated by a deuterium-labeling experiment. In the case of the ketone 9b, having another spiroannulated cyclopentane ring attached on 9a, the trispirotetraquiane 11b was not obtained but the bis-propellane-type tetrahydrofuran 25 was produced exclusively. The 5-(5'-cyclopentylidenecyclooctylidene)cyclooctanone (9c) afforded the polycyclic compounds 27-31, depending on the acid used, instead of the desired tetraspiropentaquinane 11c. The structures of the products were determined by NMR spectral data including 2D (13)C INADEQUATE spectra and X-ray crystallographic analyses. The unexpected rearrangement pathways are also discussed.     

Massenspektroskopische Untersuchung von substituierten Steroidsapogeninen

Zusammenfassung Der Einfluß von Substituenten in Ring D und F auf das Fragmentierungsverhalten von Spirostan-Derivaten wird diskutiert.

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Mass spectrometric investigation of substituted steroid sapogenins

The influence of substitutents in ring D and F on the fragmentation behavior of spirostane derivatives is discussed.

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Mit 10 Abbildungen     

Quadrupole moment of41Sc by use of new nuclear quadrupole resonance detection

Quadrupole effects in -NMR spectra of⁴¹Sc(I =7/2^–,T _1/2=0.596 s) implanted in a TiO₂ single crystal were detected by use of a modified -NMR technique. Using the field gradient in the crystal determined by the pulsed-Fourier-transformed NMR of⁴⁵Sc in TiO₂, the quadrupole moment of⁴¹Sc has been determined as |Q(⁴¹Sc; 7/2^–)|=166±8 mb.     

Isolation of lignan glucosides and neolignan sulfate from the leaves of Glochidion zeylanicum (Gaertn) A. Juss

Six lignan and neolignan derivatives (1-6) were isolated from the n-BuOH-soluble fraction of a MeOH extract of the leaves of Glochidion zeylanicum. On the basis of spectral data, their structures were elucidated to be (+)-isolarisiresinol 3a-O-beta-glucopyranoside (1), dihydrodehydrodiconiferyl alcohol 4-, 9- and 9'-O-beta-D-glucopyranosides (2-4, respectively), (+)-isolarisiresinol 2a-O-beta-D-glucopyranoside (5), and dihydrodehydrodiconiferyl alcohol 9-O-sulfate (6), and 5 and 6 were new compounds.