Dynamically coated capillaries improve the identification power of capillary zone electrophoresis for basic drugs in toxicological analysis

In systematic toxicological analysis (STA), analytical methods should have a high identification power. This can be suitably expressed by parameters such as mean list length (MLL) or discriminating power (DP). The reproducibility of a method has a great impact on its identification power, and should be as high as possible. In this study, two separation methods based on capillary zone electrophoresis (CZE) were evaluated towards STA applications. Besides a normal phosphate buffer, the commercially available buffer CElixir was used, which is a double-layer dynamic coating system. The coating stabilizes the endoosmotic flow, is independent of the pH, and is claimed to be more reproducible and faster at low pH than with normal buffers. A test set of 73 basic pharmaceutical compounds was analyzed by the two CZE methods. The total analysis time, including rinsing steps, was 8 min when the coating was used and 18 min without the coating. Effective mobilities were calculated and the reproducibilities were a factor of 2 better when the coating was used (between-days SD 0.020 and 0.040 m2/V s with and without the coating, respectively). MLL and DP were calculated for the two CZE methods and for combinations with standardized liquid and gas chromatography systems. CZE with CElixir coating clearly has a high potential for STA applications, as it was shown to have a higher identification power and shorter analysis times than normal CZE.     

Temperature Dependence of the Crystal Structure and EPR Spectrum of Bis(1,3,5-Trihydroxycyclohexane)copper(II) Tosylate. A Unified Interpretation Using a Model of Dynamic Vibronic Coupling

The crystal structure of bis(1,3,5-trihydroxycyclohexane)copper(II) tosylate is reported at temperatures of 293, 233, 188, 163, and 93 K, as are the structures of the Zn(II) and Ni(II) analogues at room temperature for comparison. The isomorphous compounds are triclinic, space group P&onemacr;, with one formula unit in the unit cell. The unit cell parameters of the Cu compound at 293 K are a = 6.456(5) ?, b = 9.505(3) ?, c = 12.544(3) ?, alpha = 76.57(2) degrees, beta = 87.48(4) degrees, gamma = 76.65(4) degrees. The centrosymmetric ZnO(6) and NiO(6) octahedra are tetragonally compressed with a slight orthorhombic distortion. The Cu(2+) polyhedra exhibit similar geometries, but with considerably larger deviations from a regular octahedron. Two of the three independent Cu-O bond lengths and two of the g-values change significantly as a function of temperature. A model of dynamic vibronic coupling is presented which explains both the EPR and structural data. Vibronic wave functions associated with a Jahn-Teller potential energy surface modified by an orthorhombic lattice "strain" are given. The temperature dependence of the structures is calculated from the nuclear parts and that of the g-values from the electronic parts of the wave functions. The temperature dependence of the structures and g-values is also interpreted using a simpler model involving an equilibrium between two forms of the complex which differ solely in their orientation in the crystal lattice, and the results of the two approaches are compared.     

Characteristics of vellosimine reductase,a specific enzyme involved in the biosynthesis of the rauwolfia alkaloid sarpagine

A plant enzyme - vellosimine reductase - has been isolated from $\text{Rauwolfia}$ cell suspension cultures. This new enzyme has been-purified (110-fold) and characterized. The reductase is a specific enzyme of the sarpagine pathway catalyzing the NADPH dependent conversion of vellosimine into 10-deoxysarpagine. The latter alkaloid is the immediate biogenetic precursor of sarpagine as shown by its high $\text{in}$$\text{vivo}$ incorporation rate (86%) into sarpagine.     

Stereoselektive totalsynthese von (±)-torreyol

Enones of formulae Ia-d undergo cyclization to give stereoselectively the enol esters IIa-d, respectively, IIa-d are suitable synthones for some sesquiterpene syntheses .— In this paper the synthesis of torreyol (1) is described by an all step stereocontrolled reaction sequence: cyclization educt 10 (Ic) was prepared by alkylation of 8 with 5 and enol ether cleavage of 9. The reaction sequence 11a (IIc)→14a 15 → 18 (ester hydrolysis, formation of the tert. alcohol, degradation of the isopropenyl group) followed by oxidation resulted in the formation of ketone 19 whose relative configuration was determined by the 2D J-resolved 400 MHz ¹H NMR spectrum. After methylation at C-8 (22→23) the tosylhydrazone 25 underwent Bamford-Stevens reaction to yield (±)-1.     

Synthetische Juvenilhormone 2. Mitteilung. p-Substituierte 2-Methyl-3-phenyl-propen(1)-carbonsäurederivate

In the second communication the synthesis of para-substituted 2-methyl-3-phenylpropen(1)-carboxylic acid derivatives is described: Phenylacetone compounds are formed by decarboxylation of a glycidicester; these react according to the Wadsworth-Emmons (Wittig-Horner)-reaction with the corresponding phosphonates to the title compounds. NMR. data show the formation of the steric isomers of 3-Phenyl-2-methyl-propen-1- and 3-Phenyl-2-methylpropen-2-carboxylic acid derivatives.     

Application of the isoselective relationship to diels-alder reactions

Diels-Alder reactions with “normal” and “reverse” electron demand” obey common isoselective relationships (Figure I).     

Asymptotic normality of double-indexed linear permutation statistics

The paper provides sufficient conditions for the asymptotic normality of statistics of the form a _ijb_RiRj, wherea _ijandb _ijare real numbers andR _iis a random permutation.