Mammalian alkaloids: Synthesis and O-methylation of (S)- and (R)-3′-hydroxycoclaurine and their N-methylated analogues with S-adenosyl-L-[methyl-14C]methionine in presence of mammalian catechol O-methyltransferase

O-Methylation of the optically active 3′-hydroxycoclaurines 3a and 3b and of the N-methylated analogs 5a,b with S-adenosyl-L -[methyl-¹⁴C]methionine in presence of mammalian COMT was investigated in vitro. The N-unsubstituted (1S)- and (1R )-isomers 3a and 3b , respectively, afforded almost equal amounts of the corresponding N-norreticuline 4 and N-nororientaline 19 , besides two unknown by-products (see Fig. and Table 1). The N-methylated (1S)-isoquinoline 5a , on the other hand, afforded largely (S)-orientaline ((S)- 19 ), while an almost equal mixture of (R)-reticuline ( 6b ) and (R)-orientaline ((R)- 19 ) was obtained from the (1R)-enantiomer 5b . The isoquinolines 3a,b and 5a,b were prepared by a Bischler-Napieralski cyclization yielding O-benzyl-protected isoquinoline 10 (Scheme 1). The optical resolution of 10 was accomplished with 2′-bromotartranilic acid. The N-methylated isoquinolines were prepared by N-formylation of 10a,b and reduction of the formamides 13a,b with diborane (→ 14a,b ). Deblocking of the benzyl-ether moieties of 10a,b and 14a,b was accomplished by catalytic hydrogenation in presence of HCl, affording directly 3a,b ·HCl and 5a,b ·HCl, respectively.     

Controlled growth of rutile TiO2 by atomic layer deposition on oxidized ruthenium

Crystalline rutile TiO₂ films were grown by atomic layer deposition on oxidized Ru electrodes using a titanium methoxide as the metal precursor and O₃ as the oxidant. A protective layer of ～0.3 nm TiO₂ grown with H₂O as the oxidant was first deposited in order to avoid etching of the Ru bottom electrode by the O₃ used for the growth of the TiO₂ (bulk) layer. Electrical evaluation of the capacitor stacks with TiO₂ as dielectric, RuO₂/Ru and Pt as the bottom and top electrodes respectively, resulted in superior characteristics of the rutile phase as compared to the anatase. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Exact and Numerical Solution of the Fractional Sturm–Liouville Problem with Neumann Boundary Conditions

In this paper, we study the fractional Sturm–Liouville problem with homogeneous Neumann boundary conditions. We transform the differential problem to an equivalent integral one on a suitable function space. Next, we discretize the integral fractional Sturm–Liouville problem and discuss the orthogonality of eigenvectors. Finally, we present the numerical results for the considered problem obtained by utilizing the midpoint rectangular rule.     

Implementation of a graphical user interface for the virtual multifrequency spectrometer: The VMS‐Draw tool

This article presents the setup and implementation of a graphical user interface (VMS‐Draw) for a virtual multifrequency spectrometer. Special attention is paid to ease of use, generality and robustness for a panel of spectroscopic techniques and quantum mechanical approaches. Depending on the kind of data to be analyzed, VMS‐Draw produces different types of graphical representations, including two‐dimensional or three‐dimesional (3D) plots, bar charts, or heat maps. Among other integrated features, one may quote the convolution of stick spectra to obtain realistic line‐shapes. It is also possible to analyze and visualize, together with the structure, the molecular orbitals and/or the vibrational motions of molecular systems thanks to 3D interactive tools. On these grounds, VMS‐Draw could represent a useful additional tool for spectroscopic studies integrating measurements and computer simulations. © 2014 Wiley Periodicals, Inc.     

A new semiconducting quaternary mixed halogenide: pentathallium dimercury pentabromide tetraiodide,Tl5Hg2Br5I4

A novel quaternary mixed halogenide, Tl₅Hg₂Br₅I₄, was synthesized by fusion of thallium bromide and mercury iodide in a 5:2 molar ratio. The crystal structure of Tl₅Hg₂Br₅I₄ represents a new series of composite structures described by the general formula nTlBr*mTl₂[HgBr₂I₂]; in this case, n = 4 and m = 8. Electronic structure calculations indicate that the title compound is a semiconductor.     

Liquid chromatography–mass spectrometry method for the analysis of 1,4‐dimethylpyridinium in rat plasma – application to pharmacokinetic studies

A sensitive and specific liquid chromatography electrospray ionization–mass spectrometry method for determination of 1,4‐dimethylpyridinium (1,4‐DMP) in rat plasma has been developed and validated. Chromatography was performed on an Aquasil C₁₈ analytical column (4.6 × 150 mm, 5 µm, Thermo Scientific, Rockford, IL, USA) with isocratic elution using a mobile phase containing acetonitrile and water with an addition of 0.1% of formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization was used for ion production. The limit of detection in the single ion monitoring mode was found to be 10 ng/mL. The limit of quantification was 50 ng/mL. The precision and accuracy for both within‐day and between‐day determination of 1,4‐dimethylpyridinium was 2.4–7.56 and 90.93–111.48%. The results of this analytical method validation allow pharmacokinetic studies to be carried out in rats. The method was used for the pilot study of the pharmacokinetic behavior of 1,4‐DMP in rats after intravenous administration. Copyright © 2012 John Wiley & Sons, Ltd.