bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of the dielectric properties of nematic liquid crystals at 10 kHz to 40 GHz and application to a variable delay line
Authors: Kamei Toshihisa , Utsumi Yozo , Moritake Hiroshi , Toda Kohji , Suzuki Hirosuke
Published: July 2003

In support of the application of liquid crystals to adaptive devices such as variable delay lines in the microwave and millimeter band, the complex permittivities and response times of five different nematic liquid crystals after voltage application were measured. We measured both the real part $\varepsilon'_{//}$ of the relative permittivity, when the long axis of the liquid crystal molecule is parallel to the high‐frequency electric field, and the relative permittivity $\varepsilon'_{\bot}$ when it is perpendicular to the high‐frequency electric field. The values $\tan\delta_{//}$ and $\tan\delta_{\bot}$ were measured. In the range from 10 kHz to 13 MHz, the capacitance and conductance of a liquid crystal cell sandwiched between ITO glass plates processed by rubbing were directly measured. For 100 MHz to 40 GHz, we propose the new cutback method, in which two coaxial tubes with different lengths are filled with the liquid crystal and the dielectric properties are measured on the basis of their respective group delay and transmission loss. Dielectric relaxation is verified in the low frequency range. In particular, in the range from 3 to 40 GHz, dielectric properties are shown for a continuous change of frequency. It is found that $\varepsilon'_{//}$ and $\varepsilon'_{\bot}$ are kept almost constant regardless of the frequency, taking values of approximately 3 and 2.5, respectively. $\Delta\varepsilon'$, which is the difference between the permittivities in two orientations, exhibits a large variation, from 0.4 to 0.8, depending on the material, which provides crucial data for selecting the optimal material. The response time was measured by placing the liquid crystal cell between two polarizers with the polarizing directions set parallel. The light from a He‐Ne laser (632.8 nm) is directed onto the liquid crystal cell, and the transmitted light is detected by a photodiode. Assuming that the liquid crystal is used in an adaptive device, the speed of operation is investigated. Based on the measurement results for two different nematic liquid crystals, the design of a variable delay line for 20, 30, and 40 GHz is considered, and a principle of liquid crystal material selection is presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 49–60, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10130
Proposal and switching characteristics evaluation for waveguide‐prism‐deflector type micro optical switches (WPD‐MOS)
Authors: Ninomiya Minoru , Arai Yukihiko , Yoshimura Tetsuzo , Kurokawa Hiroaki , Asama Kunihiko
Published: July 2003

To handle the drastic increase in communication capacity, the need for large‐scale, high‐speed switching systems is expected. As a solution, we proposed a 3‐Dimensional Micro Optical Switching System (3D‐MOSS) that arranges many thin‐film micro optical switches in multiple layers and connects them with Optical Z‐Connections. This implementation requires a micro optical switch having fast, stable operation. In this paper, we propose a waveguide‐prism‐deflector type micro optical switch (WPD‐MOS) as a candidate 3D‐MOSS thin‐film micro optical switch and analyze its operation. This optical switch forms a prism electrode in a slab waveguide having the electro‐optical effect. The application of voltage produces a dynamic waveguide prism and deflects the optical beam. A feature is the insensitivity of the processing precision to strong temperature fluctuations. An evaluation by the Beam Propagation Method (BPM) demonstrated the ability to implement 2 × 2 micro optical switches having a length of 390 µm, crosstalk ≤ − 12 dB, and insertion losses ≤ 0.96 dB at the drive voltage of 110 V. We also studied a 3 × 3 WPD‐MOS. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 38–48, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10132
On polarization of the Poynting flux
Authors: Tokumaru Shinobu
Published: July 2003

The trajectories of the tips of the electric field vector and the magnetic field vector in real time are explained by the concept of polarization structures. In this paper, the elliptic locus drawn by the tip of the Poynting vector in real time is treated as the ≪polarization≫ structure. From the shape of this polarization, electromagnetic fields can be classified as: $\def\circle#1{{\ooalign{\hfil\raise.07ex\hbox{#1}\hfil\crcr\mathhexbox20D}}} \circle{1}$ characteristic fields (parallel‐polarization similarity fields), $\def\circle#1{{\ooalign{\hfil\raise.07ex\hbox{#1}\hfil\crcr\mathhexbox20D}}} \circle{2}$ plane wave fields (orthogonal‐polarization similarity field), $\def\circle#1{{\ooalign{\hfil\raise.07ex\hbox{#1}\hfil\crcr\mathhexbox20D}}} \circle{3}$ half‐linear polarization fields (either the electric field or the magnetic field is linearly polarized), and $\def\circle#1{{\ooalign{\hfil\raise.07ex\hbox{#1}\hfil\crcr\mathhexbox20D}}} \circle{4}$ other general electric fields. It can be shown that information on the electric and magnetic fields of the primary quantities can be obtained from secondary quantities related to the power of the electromagnetic field. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 28–37, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10139
Periodic‐structure‐type electromagnetic wave absorber analysis by the Non‐Standard FDTD method using complex formulation
Authors: Ohtani Tadao , Kashiwa Tatsuya
Published: July 2003

In this paper, in order to analyze a periodic‐structure electromagnetic wave absorber by the Non‐Standard FDTD (NS‐FDTD) method, an NS‐FDTD method using complex formulation is proposed. In order to clarify the characteristics of this method, the numerical dispersion equation and the stability condition are newly derived. It is found that the proposed NS‐FDTD method using complex formulation is much more accurate and stable than the conventional FDTD method. The present method is also applied to the analysis of a fin ferrite electromagnetic wave absorber with a periodic structure. It is demonstrated that the proposed NS‐FDTD method using complex formulation is an effective method of analysis with higher accuracy than the conventional FDTD method. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 20–27, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10145
Waveguide bandpass filter and FDTD analysis
Authors: Harada Shinnya , Iida Yukio
Published: July 2003

In regard to the FDTD analysis of a waveguide bandpass filter, a method of processing time series FDTD data for the Fourier transform is discussed in conjunction with boundary processing near conductor corners, and a new method of processing the FDTD data is proposed. When this method is used, the total computation time for all FDTD processing is reduced by more than 60%. By a calculation for the iris‐coupled waveguide bandpass filter, it is confirmed that the new grid arrangement method is as accurate as the corner correction method and is more accurate than the conventional grid arrangement method. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 12–19, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10147
Multitone curve‐fitting algorithms for communication application ADC testing
Authors: Motoki Yoshito , Sugawara Hidetake , Kobayashi Haruo , Komuro Takanori , Sakayori Hiroshi
Published: July 2003

This paper describes multitone curve‐fitting algorithms for accurate determination of intermodulation distortion products in the multitone testing of ADCs used in communication applications and the like. Accuracy of our curve‐fitting algorithms for coherent sampling (input frequencies known) and incoherent sampling (input frequencies unknown) was validated by numerical simulations. We found that—especially for incoherent sampling—these algorithms provide better accuracy than conventional (single‐tone) curve‐fitting algorithms. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(8): 1–11, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10148
Bis(oxazoline)titanium Complexes as Chiral Catalysts for Enantioselective Hydrosilylation of Ketones − A Combined Experimental and Theoretical Investigation
Authors: Bandini Marco , Bernardi Fernando , Bottoni Andrea , Cozzi Pier Giorgio , Miscione Gian Pietro , Umani‐Ronchi Achille
Published: July 2003

A combined experimental and theoretical investigation has been carried out on a new catalytic system, based on bis(oxazoline) (BOX) complexes of titanium. These catalytic species are able to reduce aromatic ketones with good enantiomeric excesses and satisfactory yields. The experimental and the computational (DFT) evidence has provided useful information on the nature of the active catalytic species and on the mechanism of the reaction. The most likely reaction path involves a TiIV catalytic species. This result agrees with experimentally obtained evidence that seems to rule out the presence of TiIII species. The analysis of the structure of the transition state corresponding to the reduction process (the addition of the hydride to the carbonyl system), provides an interesting insight on the enantioselectivity that characterizes this reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Biosynthesis of Defensive Compounds from Beetles and Ants
Authors: Laurent Pascal , Braekman Jean‐Claude , Daloze Désiré , Pasteels Jacques
Published: July 2003

Many beetle and ant species owe their protection against predators to the presence of defensive compounds in their hemolymph or in specialized exocrine glands. A growing number of studies devoted to the elucidation of the biosynthetic pathways used by the insects to produce these compounds have been reported in recent years. An overview of these studies is presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of New Thiophene‐Substituted 3,3‐Diphenyl‐3H‐naphtho[2,1‐b]pyrans by Cross‐Coupling Reactions, Precursors of Photomodulated Materials
Authors: Frigoli Michel , Moustrou Corinne , Samat André , Guglielmetti Robert
Published: July 2003

3,3‐Diphenyl‐3H‐naphtho[2,1‐b]pyrans linked to one, two, or three thiophene nuclei in different positions of the naphthalene moiety (5, 6, 8, and 9) by a covalent bond have been prepared in good yields. A Suzuki cross‐coupling reaction was used with two possible strategies: chromenization before the coupling with oligothiophenes or chromenization after the coupling, the main intermediates being the diphenyl propargylic alcohol, the functionalized naphthol derivatives, and the thiophenic boronates. The overall yields for obtaining such photochromic compounds are generally quite satisfying. For the 7‐position, the coupling reaction has been realized using a Grignard reaction between a tetralone derivative and a thiophenic bromo magnesium intermediate. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Palladium‐Catalyzed Annulation of Aryl‐1,2‐diols and Propargylic Carbonates. Theoretical Study of the Observed Regioselectivities
Authors: Labrosse Jean‐Robert , Lhoste Paul , Delbecq Françoise , Sinou Denis
Published: July 2003

Methyl 1‐methylprop‐2‐ynyl carbonate reacts with 3‐ and 4‐substituted benzene‐1,2‐diols to give 2,3‐dihydro‐3‐methyl‐2‐methylidene‐1,4‐benzodioxines, as a mixture of regioisomers in the case of methoxy‐substituted diphenol, and a single regioisomer for the nitro‐ and the formyl‐substituted diphenols. The oxyanion which attacks first corresponds to the less acidic hydroxy function, and the attack of the second oxyanion on the η3‐allylpalladium intermediate is directed toward the more substituted carbon atom. In order to explain the regioselectivity of the cyclization, a theoretical study based on density functional theory (DFT) has been performed. The first step implies an equilibrium between the two oxyanions. The regioselectivity of the second step is due to a subtle balance between the nature of the phosphane, the bulkiness, and the electronic properties of the substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of Ring Size seco‐Analogs of the Antitumor Antibiotic CC‐1065 by Two Consecutive Transition Metal‐Initiated Transformations
Authors: Tietze Lutz F. , Looft Jan , Feuerstein Tim
Published: July 2003

Novel seco‐analogs of CC‐1065 1 were synthesized from comercially available nitroaniline by reduction, bromination, bisulfonation and bisallylation followed by reaction with tert‐butyllithium, zirconocene and iodine. The obtained quinoline 6 was then transformed into 17 and 18, which, upon treatment with Pd0, led to 21 and 22, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New Functional Hexahelicenes − Synthesis, Chiroptical Properties, X‐ray Crystal Structures, and Comparative Data Bank Analysis of Hexahelicenes
Authors: Wachsmann Claudia , Weber Edwin , Czugler Mátyás , Seichter Wilhelm
Published: July 2003

Seven new hexahelicenes (3−7, 9, 10) containing different functional group substituents have been synthesized and, in three cases (4, 8, 10), optically resolved. Optical rotations were measured and CD spectra are reported. X‐ray crystal structures of the helicenes 1, 3, 4, 8, and 9 have been determined, of which 4 represents a 1:1 clathrate with acetone. These show a concerted interplay of C−H···O, C−H···π, and π···π supramolecular interactions in the packings, mostly yielding stacks of molecules (1, 3, 4, 8). Statistical analysis of the molecular dimensions in these and related crystal structures was carried out in order to identify potential parameters relevant to macroscopic phenomena, including optical rotation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stereoselective Synthesis of (−)‐Deacetylanisomycin
Authors: Merino Pedro , Franco Santiago , Lafuente Diego , Merchan Francisco , Revuelta Julia , Tejero Tomas
Published: July 2003

A stereoselective synthesis of (−)‐deacetylanisomycin has been achieved from a nitrone derived from L‐threose in 6 steps and 53.7% overall yield. The key step of the synthesis is the nucleophilic addition of a Grignard derivative with complete diastereofacial selectivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Highly Enantioselective Allylation of Arylaldehydes Catalyzed by a Silver(I)‐Chiral Binaphthylthiophosphoramide
Authors: Wang Chun‐Jiang , Shi Min
Published: July 2003

Chiral diphenylthiophosphoramideL2prepared from diphenylthiophosphinic chloride and (R)‐(+)‐N‐ethyl‐1,1′‐binaphthyl‐2,2′‐diamine2was used as a catalytic chiral ligand in the silver(I)‐catalyzed enantioselective allylation reaction of arylaldehydes with allyltributyltin to furnish highee(up to 98%) of the homoallylic alcohols. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Highly Selective Negishi Cross‐Coupling Reaction of a Zinc‐Metallated Ferrocenyl p‐Tolyl Sulfoxide: New Chiral Ferrocene‐Based Quinone Ligands
Authors: Cotton Hanna K. , Huerta Fernando F. , Bäckvall Jan‐E.
Published: July 2003

A highly selective Negishi coupling of zinc‐metallated ferrocenyl p‐tolyl sulfoxide with aryl bromides was developed. With Pd(PPh3)4 as catalyst, a well‐matched system in terms of reactivity of organometallic compound, aryl bromide, and catalyst, was obtained. The scope of the reaction was studied by the use of aryl bromides 7a−g, which afforded high yields of coupling products. The reaction conditions for the preparation of ferrocenyl p‐tolyl sulfoxide, according to the Andersen method, were optimised to give a yield of 80% and an enantiomeric excess of 98%. Target compound 1b was obtained by deprotection of acetate‐protected hydroquinone 8f, employing sodium borohydride in dimethoxyethane, in a yield of 87%. Target compounds 2b and 3b decomposed during workup. The possibility of internal electron transfer, between the ferrocene moiety and the hydroquinone moiety, may account for this instability. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Tetraphenylethene‐Derived Columnar Liquid Crystals and Their Oxidative Photocyclization
Authors: Schultz Andreas , Laschat Sabine , Diele Siegmar , Nimtz Manfred
Published: July 2003

The synthesis of novel tetraphenylethenes 9a−f, 13, and 18a,b bearing ether, biphenyl, and 4‐cyanobiphenyl moieties via a McMurry reaction and Suzuki coupling as key steps is described. Mesogenic properties of these compounds were studied by differential scanning calorimetry (DSC), optical polarizing microscopy, and X‐ray diffraction. Ether‐substituted derivatives 9a,b with chain lengths C8 or C9 were non‐mesogenic. Compounds 9c−f with longer alkyl chains displayed hexagonal columnar mesophases. Whereas cyanobiphenyl derivative 13 was non‐mesogenic, the corresponding biphenyl systems 18a,b with decyloxy and dodecyloxy chains, respectively, formed hexagonal columnar mesophases. Oxidative photocyclization of compounds 1f, 9c, 13, and 18a were investigated. Upon irradiation in the presence of iodine tetraphenylethenes 1f, 9c gave the corresponding phenanthrenes 22a,b. The mesomorphic properties of 22a,b were strongly dependent on the substituent. Whereas ether 22a displayed only isotropic melting, a hexagonal columnar mesophase was found for ester 22b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
[2+2+2] Cocyclotrimerization with Ferrocenylalkynes
Authors: Dufková Lenka , Císařová Ivana , Štepnička Petr , Kotora Martin
Published: July 2003

Cocyclotrimerization of ferrocenylalkynes FcC≡CR (R = H and CH2OH) with α,ψ‐diynes X(CH2C≡CH)2, where X = O, C(CO2Et), C(CN)(CO2Et), C(COMe)2, and C(COMe)(CO2Et), to give functionalised ferrocenylarenes was attempted in the presence of various catalytic systems: [RhCl(PPh3)3], [CoBr(PPh3)3], [NiBr2(dppe)]/Zn, [{Ir(cod)Cl}2]/dppe and [CpCo(cod)]/PPh3 [Cp = η5‐cyclopentadienyl, cod = η4‐cycloocta‐1,5‐diene, and dppe = 1,2‐bis(diphenylphosphanyl)ethane]. The results indicate that Wilkinson’s catalyst effects the cocyclotrimerization to afford the respective ferrocenylarenes in good yields and under mild conditions regardless of the nature of the functional groups. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
endo/exo Preferences for Double Bonds in Three‐Membered Rings Including Phosphorus Compounds
Authors: Goumans T. P. M. , Ehlers Andreas W. , Lammertsma Koop , Würthwein Ernst‐Ulrich
Published: July 2003

Depending on the substituent and the heteroelements of an unsaturated three‐membered ring system of the methylenecyclopropane/1‐methylcyclopropene type, the double bond may be preferentially exo‐ or endocyclic. This preference may be considered as a combination of substituent and ring‐strain effects. The substituent effect is a composite one, encompassing both exocyclic olefinic strain and tautomeric preference. The preference for exocyclic unsaturation increases in the order =CH2 < =NH < =PH < =O for the considered substituents. The higher the ring‐strain, the higher the propensity for exocyclic unsaturation. The low‐strain 2H‐phosphirenes favor endocyclic unsaturation, except for the 3‐OH‐substituted species where the strong C=O double bond is the determining factor. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Preparation and Characterization of Sulfonyl‐Azafulleroid and Sulfonylaziridino‐Fullerene Derivatives
Authors: Ulmer Lars , Mattay Jochen
Published: July 2003

Thermolysis of several sulfonyl azides in the presence of C60 leads either to aza[60]fulleroids or to mixtures of aza[60]fulleroids and corresponding aziridino‐fullerenes, depending on the substituent at the sulfonyl group. In all cases, 1,2‐closed aziridino‐fullerenes can be obtained from azafulleroids by irradiation. Addition of sulfonyl azides to C70 only yields azafulleroids with Cs‐symmetry. Cyclic‐voltammetric measurements revealed that there is no significant change of electrochemical properties compared to C60 and C70. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Flexible Synthesis of Indoline, Indolizidine, and Pyrrolizidine Derivatives
Authors: Bytschkov Igor , Siebeneicher Holger , Doye Sven
Published: July 2003

New and flexible procedures for the synthesis of indoline, indolizidine, and pyrrolizidine derivatives are described. By these new procedures, the target compounds can be synthesized with high diversity from three building blocks (ortho‐bromo‐ or ortho‐chloro‐iodobenzenes, terminal alkynes, and primary amines). The synthetic strategies presented include Sonogashira couplings, Cp2TiMe2‐catalyzed hydroaminations of alkynes, and Pd‐catalyzed aminations of aryl halides as key steps. Since many of the employed starting materials are commercially available or easily accessible, a huge number of indoline, indolizidine, and pyrrolizidine derivatives is theoretically obtainable by the standard reaction sequences developed. Since the experimental procedures are simple and mostly catalytic, applications of the described methods for automated synthesis are also imaginable. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
First Synthesis of (8‐2H3)‐(all‐rac)‐δ‐Tocopherol
Authors: Mazzini Francesco , Alpi Emanuele , Salvadori Piero , Netscher Thomas
Published: July 2003

Trideuterated tocopherols were needed to be used as internal standards for our study about simultaneous quantitative determination of tocopherols in foodstuffs by mass spectrometry. Whilst procedures for trideuterated α‐tocopherol have been recently optimized, no method is reported as regards δ‐tocopherol. Different synthetic approaches are discussed, as well as the first procedure for the synthesis of (8‐2H3)‐(all‐rac)‐δ‐tocopherol. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Flexible Route Towards Five‐Membered Ring Imino Sugars and Their Novel 2‐Deoxy‐2‐fluoro Analogues
Authors: Ayad Tahar , Génisson Yves , Broussy Sylvain , Baltas Michel , Gorrichon Liliane
Published: July 2003

A flexible route towards five‐membered ring imino sugars starting from a chiral α,β‐epoxy aldehyde has been developed. The approach relies on the use of the versatile epoxyamine intermediate 4, from which regiocontrolled epoxide opening affords diastereoselective access to trisubstituted pyrrolidines. Described here is the nucleophilic attack at C‐2 of the pivotal epoxypyrrolidine 10, leading to the biologically relevant imino sugars 1,4‐dideoxy‐1,4‐imino‐D‐arabinitol (2) and 1,4‐dideoxy‐1,4‐imino‐L‐galactitol (3) as well as their novel 2‐deoxy‐2‐fluoro analogues, after oxidative manipulation of the vinyl moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Aminoglycoside‐Derived Cationic Lipids for Gene Transfection: Synthesis of Kanamycin A Derivatives
Authors: Sainlos Matthieu , Belmont Philippe , Vigneron Jean‐Pierre , Lehn Pierre , Lehn Jean‐Marie
Published: July 2003

Cationic lipids are currently actively investigated as an alternative approach to recombinant viruses for gene transfer studies and gene therapy applications. Basically, they rely on the formation of lipid/DNA aggregates via electrostatic interactions between their cationic headgroup and the negatively charged DNA. The development of new amphiphilic structures should allow to shed light on their still poorly understood structure/activity relationship and thereby help to design improved vectors. It appears that aminoglycosides, which are natural polyamines known to bind to nucleic acids, provide a favourable scaffold for the synthesis of a variety of cationic lipids because of their structural features and multifunctional nature. The synthesis and full characterization of a series of lipophilic derivatives of the aminoglycoside antibiotic kanamycin A, mainly kanamycin−cholesterol conjugates, are reported herein. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Preparation of New Sulfonated Triarylphosphanes: Control of the Selectivity by Structural Assistance
Authors: Gulyás Henrik , Szöllősy Áron , Szabó Pál , Halmos Pál , Bakos József
Published: July 2003

A synthetic approach for the selective preparation of tri‐, di‐, and monosulfonated triarylphosphanes is presented. PPhnAr3−n parent phosphanes (1a−8a) having aryl rings (Ar) activated by simple electron donating groups (CH3, CH3O) were prepared by the standard Grignard method. The activated rings could be sulfonated selectively under mild conditions and with short reaction times (0.8−3 h). Using a very simple workup procedure, the corresponding tri‐, di‐, and monosulfonated phosphanes (1b−8b) were isolated in outstanding yields (88−99%) and found to contain negligible amount of phosphane oxides (0−4%). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Organocatalysts Promote Enantioselective 1,3‐Dipolar Cycloadditions of Nitrones with 1‐Cycloalkene‐1‐carboxaldehydes
Authors: Karlsson Staffan , Högberg Hans‐Erik
Published: July 2003

In the presence of enantiopure organocatalysts, 1‐cycloalkene‐1‐carboxaldehydes and various nitrones furnished fused isoxazolidines. Thus, some chiral pyrrolidinium salts catalyzed the formation of such cycloadducts in high diastereo‐ and enantioselectivity (up to 92% ee). The predominant diastereomer, the exo one, was mostly obtained in excellent diastereoselectivity (> 99:1 dr). Furthermore, after recrystallization of one of the cycloadducts, this was obtained enantiomerically pure (> 99% ee). The absolute configuration of one of the cycloadducts was determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Mycobacterium tuberculosis Thymidine Monophosphate Kinase Inhibitors: Biological Evaluation and Conformational Analysis of 2′‐ and 3′‐Modified Thymidine Analogues
Authors: Van Rompaey Philippe , Nauwelaerts Koen , Vanheusden Veerle , Rozenski Jef , Munier‐Lehmann Hélène , Herdewijn Piet , Van Calenbergh Serge
Published: July 2003

Mycobacterium tuberculosis thymidine monophosphate kinase (TMPKmt) has recently been introduced as a potential target for the structure‐based design of anti‐tuberculosis drugs. Based on the TMPKmt X‐ray structure and previous S.A.R. studies, we synthesised the nucleoside analogues 3a−b, 6a−b, 7a−b, and 8a−b, modified in 2′‐ and 3′‐position of the ribofuranose ring moiety. To our surprise, these analogues showed only moderate binding affinity (i.e. Ki between 118 and 1260 μM). This prompted us to investigate the conformational features of these nucleosides. We concluded that compounds of this series, especially 8a−b, are strongly biased towards the “Northern” furanose ring conformation, whereas X‐ray crystallography reveals a preference of TMPKmt for the opposite “Southern” conformers. This paper covers the synthesis, biological evaluation and conformational features (i.e. preferred ring puckering) of the 2′‐ and 3′‐modified dT analogues. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cathodic Cyclisation of N‐(Oxoalkyl)pyridinium Salts − Formation of Tricyclic Indolizidine and Quinolizidine Derivatives in Aqueous Medium
Authors: Heimann Jens , Schäfer Hans J. , Fröhlich Roland , Wibbeling Birgit
Published: July 2003

The cathodic cyclisation of N‐(oxoalkyl)pyridinium salts, derived from 4‐methylpyridine and cyclic ketones, afforded functionalised tricyclic indolizidine and quinolizidine derivatives in high yields. Through systematic variation of the ring size of the ketone and the cyclised ring, a series of four cyclopenta‐/cyclohexa[a]indolizidines and ‐quinolizidines was obtained. The cyclisation was also applied to the synthesis of a cyclohexa[b]quinolizidine derivative, which represents a substructure of the cevanine alkaloids. There is no obvious alternative route as short as this cathodic cyclisation to such indolizidines and quinolizidines. A detailed mechanism of the cyclisation is proposed. In the key step, a hydroxyalkyl radical generated by reduction of the protonated ketone adds reversibly to the pyridinium ring. Semiempirical calculations indicate that only diastereomers resulting from the thermodynamically more stable cyclised intermediates are obtained. From these data and the ΔΔfH# value for the transition states of the cyclisation, thermodynamic rather than kinetic control seems to be more likely. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
On the Way to Glycoprocessing Inhibitors − Synthesis of an Imidazolo‐Nectrisine‐Phosphono Acid Derivative: A Potential Glycosyltranferase Inhibitor
Authors: Tschamber Théophile , Gessier François , Neuburger Markus , Gurcha Sudagar S. , Besra Gurdyal S. , Streith Jacques
Published: July 2003

Assuming the transition state of glycosyltransferase inhibitors to be similar to those encountered with potent glycosidase inhibitors − i.e. a flattened conformation with a positively charged anomeric centre − we worked out a synthesis of the D‐arabino‐configured phosphonic acid target molecule 2 derived from an imidazolo‐sugar. The key synthetic intermediate is the linear imidazolo L‐xylo compound 10 which could be obtained, either from L‐threo precursor 6 by a coupling reaction with imidazole derivative 5, or from L‐sorbose. A multi‐step and site specific iodination of 10 gave the mono‐iodo‐L‐xylo derivative 14 which was cyclised to the D‐arabino‐configured bicyclic azasugar 15. Phosphorylation of the Grignard derivative of the latter, followed by mono‐esterification with citronellol along with some protection‐deprotection steps led to target molecule 2. The potential inhibitor 2 is supposed to be protonated at its most basic N atom by a carboxylic acid residue in the arabinosyl‐transferase active site. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Regioselective Enamine Formation from Oxonia‐Boranuida‐Betaines and Their Application in Asymmetric Michael Reactions
Authors: Christoffers Jens , Kreidler Burkard , Unger Sven , Frey Wolfgang
Published: July 2003

β‐Diketonato borate betaines 2 are readily accessible by the reaction of β‐dicarbonyl compounds 1 with BF3·OEt2. Reaction of borates 2 with L‐valine diethylamide (3a) gives almost exclusively the exocyclic enamines 4 as the kinetic products. In contrast, direct, acid catalyzed conversion of β‐diketones 1 with the chiral auxiliary 3a yield the endocyclic enamines 5 as the thermodynamic products. Both enamines 4 and 5 give products with quaternary stereocenters in high selectivity in copper‐catalyzed asymmetric Michael reactions with methyl vinyl ketone (8). But interestingly, exo‐ and endocyclic enamines are complementary with respect to stereochemistry of the subsequent Michael reactions since they give stereocenters with opposite configurations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
α‐Amino Acid Derivatives by Enantioselective Decarboxylation
Authors: Brunner Henri , Baur Markus A.
Published: July 2003

The methodology of enantioselective decarboxylation was applied to 2‐aminomalonic acid derivatives in order to obtain enantio‐enriched amino acid derivatives. Full conversion was achieved stirring racemic N‐acetylated 2‐aminomalonic hemiesters in THF at 70 °C with 10 mol % of a chiral base for 24 h. The catalyst may be recycled. Whereas the commercially available cinchona alkaloids gave poor results, benzamide and benzenesulfonamide derivatives of 9‐amino(9‐deoxy)epicinchonine turned out to be effective catalysts. The best result was obtained with 2‐N‐acetylamino‐2‐ethoxycarbonyl‐3‐phenylpropionic acid as the starting material and N‐(9‐deoxyepicinchonine‐9‐yl)‐4‐methoxybenzamide as the chiral base to give ethyl N‐acetyl‐L‐phenylalaninate in 70% ee. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
An Expeditious, Non‐Iterative, and Asymmetric Synthesis of 3,5,7,9,11,13,15‐Heptahydroxypentadecanals
Authors: Gerber‐Lemaire Sandrine , Vogel Pierre
Published: July 2003

Ozonolysis of (1R,1′R,6R,6′R)‐3,3′‐methylenebis{6‐[(benzyloxy)methoxy]cyclohept‐3‐en‐1‐ol} followed by the diastereoselective reduction of the resulting β‐hydroxy ketone intermediates gives a rapid route to long‐chain polyketides bearing unsymmetrical functions at their terminal positions. These can easily be converted into enantiomerically pure long‐chain 1,3‐polyol fragments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Novel Estrones by Oxidation of the Benzylic Positions of the Estrane Skeleton with tert‐Butyl Hydroperoxide and Cobalt Acetate
Authors: Modica Emilia , Bombieri Gabriella , Colombo Diego , Marchini Nicoletta , Ronchetti Fiamma , Scala Antonio , Toma Lucio
Published: July 2003

Four new estrone derivatives were isolated after treatment of estrone 3‐methyl ether (3‐methoxyestra‐1,3,5(10)‐trien‐17‐one (3) with tert‐butyl hydroperoxide and cobalt acetate. Three of the four steroidal compounds − the 9α‐(tert‐butylperoxy)‐6‐one 4, the 9α‐hydroxy‐6‐one 5, and the 9β‐hydroxy‐6‐one 7 − originated from oxidation at the 6‐ and 9‐positions. In contrast, oxidation of 3 to a 9β‐(tert‐butylperoxy) compound afforded the 8‐hydroxy‐9‐cyclodecanone derivative 6 through a molecular rearrangement involving the cleavage of the 8−9 bond. The structures of the compounds were secured by spectroscopic evidence including COSY, HSQC, and NOESY experiments combined with X‐ray crystallographic analysis and molecular modeling studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New Aspects in the Stereoselective Ethynylation of β‐C‐Glycoside Aldehydes. Application to the Synthesis of an Ambruticin Fragment
Authors: Michelet Véronique , Adiey Kouacou , Tanier Suzelle , Dujardin Gilles , Genêt Jean‐Pierre
Published: July 2003

Stereoselective ethynylation of functionalized β‐C‐glycosyl aldehydes has been achieved with various organometallic alkynes. The diastereoselectivity is highly dependent on the organometallic alkyne and on the functionalization on the C‐6 position of the glycoside. The stereoselective reaction conducted with ester‐functionalized aldehyde, followed by Mitsunobu reaction and two Pd‐catalyzed regio‐ stereo‐ and enantioselective alkylations afforded the “western” part of ambruticin. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
(−)‐Frontalin: Synthesis using the Catalytic Enantioselective Addition of Dimethylzinc to a Ketone
Authors: Yus Miguel , Ramón Diego J. , Prieto Oscar
Published: July 2003

The first enantioselective synthesis of (−)‐frontalin involving an enantioselective nucleophilic 1,2‐addition of dimethylzinc to a functionalized α,β‐unsaturated ketone, in the presence of titanium tetraisopropoxide and a substoichiometric amount of the chiral ligand 1,2‐trans‐bis(hydroxycamphorsulfonamido)cyclohexane (HOCSAC, 2) as the key step, is described. The enantiomeric excess is as high as 89%. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Biosynthesis of Defensive Compounds from Beetles and Ants (Eur. J. Org. Chem. 15/2003)
Authors: Laurent Pascal , Braekman Jean‐Claude , Daloze Désiré , Pasteels Jacques
Published: July 2003

The cover picture shows the ladybird Coccinella septempunctata (Coccinellidae) which, when molested, emits hemolymph droplets at its joints. This mechanism, known as reflex bleeding, constitutes an efficient protection against predators due to the presence of bitter‐tasting alkaloids (e.g. coccinelline). Autogenous production of coccinelline through a fatty acid biosynthetic pathway has been proved. Details on the biosynthetic capabilities of beetles and ants to produce defense compounds are discussed in the microreview by J.‐C. Braekman, D. Daloze et al. on p. 2733 ff.
Novel, Sensitive Voltammetric Methods for Titanium Determination Using Chromotropic Acid and Azo‐Compounds as Complexing Agents
Authors: Gawrys Marcin , Golimowski Jerzy
Published: July 2003

Voltammetric behavior of titanium(IV) complexes with chromotropic acid, its azo‐derivatives: 2‐(4‐sulfophenylazo)‐1,8‐dihydroxy‐3,6‐naphthalenedisulfonic acid (SPANDS), chromotrope 2B, sulfonazo III and other azo‐compounds: calmagite, tropeoline O and kalces was investigated at a hanging mercury drop electrode. These complexes strongly adsorb onto the electrode, thus can be determined by an adsorptive stripping voltammetry (optimal pH about 6). At pH about 3 reduction current enhancement for Ti‐kalces complex was observed in the presence of chlorate ions. It is a rare example of a catalytic process with azo‐compound as a complexing agent. Signal for Fe‐calmagite complex reduction was also observed. Influence of foreign ions and the optimal conditions for titanium determination are described in detail. Additionally, a connection between obtained results and a structure of titanium complexes is discussed.
Detection Mechanism of Metallized Carbon Epoxy Oxidase Enzyme Based Sensors
Authors: Khurana Manpreet K. , Winlove C. Peter , O'Hare Danny
Published: July 2003

The coenzyme FAD has been identified to play an important role in the detection mechanism of oxidase enzyme based biosensors. Incorporating FAD into the carbon composite improved sensitivity to H2O2 consequently increasing sensitivity to the respective analyte. The amount of active enzyme also increased thus enhancing the overall performance of the sensors. Polycarboxybetaine (PCB) has been used as a biocompatible membrane coating. The PCB coated sensors gave reproducible calibrations in protein solutions, which has been shown to be a valid protocol for testing biocompatibility. The importance of reporting selectivity in a manner which indicates the “fitness of purpose” of biosensors has been discussed.
Novel Gadolinium PVC‐Based Membrane Sensor Based on Omeprazole as an Antibiotic
Authors: Ganjali Mohammad Reza , Tahami Maryam , Shamsipur Mojtaba , Poursaberi Tahereh , Haghgoo Soheila , Hosseini Morteza
Published: July 2003

A novel gadolinium ion‐selective electrode based on the antibiotic omeprazole as membrane carrier was prepared. The electrode has a linear dynamic range between 1.0×10−1 and 1.0×10−5 M, with a Nernstian slope of 19.3 ± 0.3 mV decade−1 and a detection limit of 5.0×10−6 M. The potentiometric response is independent of the pH of the solution in the pH range 4.0–10.0. The electrode possesses the advantages of short conditioning time, fast response time and especially, very good selectivity over a large number of other cations. The electrode can be used for at least 2 months without any considerable divergence in potentials. It was used as an indicator electrode in potentiometric titration of Gd(III) ions with EDTA.
Electrochemical Investigations Give Some Insights into the Coordination Chemistry of New Stable Iridium(+1), Iridium(0), and Iridium(−1) Complexes
Authors: Mlakar Marina , Boulmaâz Souad , Schönberg Hartmut , Grützmacher Hansjörg
Published: July 2003

The redox chemistry of the stable tetracoordinated 16 valence electron d8‐[Ir+I(troppPh)2]+(PF6)− and pentacoordinated 18 valence d8‐[Ir+I(troppPh)2Cl] complexes was investigated by cyclic voltammetry (troppPh=dibenzotropylidenyl phosphine). The experiments were performed using a platinum microelectrode varying scan rates (100 mV/s–10 V/s) and temperatures (− 40 to 20 °C) in tetrahydrofuran, THF, or acetonitrile, ACN, as solvents. In THF, the overall two‐electron reduction of the 16 valence electron d8‐[Ir+I(troppPh)2]+(PF6)− proceeds in two well separated slow heterogeneous electron transfer steps according to: d8‐[Ir+I (troppPh)2]++e−→d9‐[Ir0(troppPh)2]+e−→d10‐[Ir−I(troppPh)2]−, [ks1=2.2×10−3 cm/s for d8‐Ir+I/d9‐Ir0 and ks2=2.0×10−3 cm/s for d9‐Ir0/d10‐Ir−I]. In ACN, the two redox waves merge into one “two‐electron” wave [ks1,2=7.76×10−4 cm/s for d8‐Ir+I/d9‐Ir0 and d9‐Ir0/d10‐Ir−I] most likely because the neutral [Ir0(troppPh)2] complex is destabilized. At low temperatures (ca. − 40 °C) and at high scan rates (ca. 10 V/s), the two‐electon redox process is kinetically resolved. In equilibrium with the tetracoordianted complex [Ir+I(troppPh)2]+ are the pentacoordinated 18 valence [Ir+I(troppPh)2L]+ complexes (L=THF, ACN, Cl−) and their electrochemical behavior was also investigated. They are irreversibly reduced at rather high negative potentials (− 1.8 to − 2.4 V) according to an ECE mechanism 1) [Ir+I(troppPh)2(L)]+e−→[Ir0(troppPh)2(L)]; 2) [Ir0(troppPh)2(L)]→[Ir(troppPh)2]+L, iii) [Ir0(troppPh)2]+e−→[Ir−I(troppPh)2]−. Since all electroactive species were isolated and structurally characterized, our measurements allow for the first time a detailed insight into some fundamental aspects of the coordination chemistry of iridium complexes in unusually low formal oxidation states.
Voltammetric Determination of Epinephrine with a 3‐Mercaptopropionic Acid Self‐Assembled Monolayer Modified Gold Electrode
Authors: Zeng Baizhao , Yang Yuxia , Zhao Faqiong
Published: July 2003

Epinephrine (EP) could exhibit an anodic peak at a bare gold electrode, but it was very insensitive. However, when the bare gold electrode was modified with 3‐mercaptopropionic acid (3MPA) self‐assembled monolayer (3MPA SAM), the peaks of EP became more reversible and sensitive due to the accumulation and mediate efficiency of 3MPA SAM. Conditions such as solution pH, concentration of supporting electrolyte and accumulation time were optimized. Under the selected conditions (i.e., 0.02 M pH 6.8 sodium phosphate buffer, accumulation time: 2 min under open‐ circuit.), the height of the anodic peak at about 0.18 V (vs. SCE) was linear to EP concentration in the range of 2×10−7 −1×10−6 M and 1×10−6−5×10−4 M with correlation coefficient of 0.995 and 0.999, respectively. When the 3MPA/Au was further modified with cysteamine, the interference of H2O2 and BrO3− was eliminated. But the resulting electrode still suffered from the interference of ascorbic acid. This method was used to determine the content of EP in adrenaline hydrochloride injections, and the recovery was in the range of 97.0% to 105.1%.
Voltammetric Study of Methylene Blue at Thiol SAMs‐Modified Gold Electrodes
Authors: Zhao Faqiong , Zeng Baizhao , Pang Daiwen
Published: July 2003

The voltammetric behavior of methylene blue (MB) at thiol self‐assembled monolayers modified gold electrodes (SAMs/Au) has been investigated. MB exhibited a redox peak at about −0.35 V (vs.SCE) in alkaline solution at bare gold electrodes. When the gold electrodes were modified with thiol SAMs, the peak grew due to the accumulation of MB at SAMs. With the solution pH rising, more MB was accumulated, hence the peak height increased, which differed from that at bare gold electrodes. The electrode process at SAMs/Au featured the characteristics of adsorption and/or electrode reaction controlled. The enhancing action of glutathione monolayer (GSH SAM), 3‐mercaptopropionic acid monolayer (3MPA SAM) and other thiol SAMs was compared. Among these, GSH SAM made the MB peak increase more. At GSH SAM/Au, the peak height varied linearly with MB concentration over the range of 2 μM to 400 μM. So this can be developed for the determination of MB and studies concerned. The accumulation behavior caused by GSH SAM and native fish sperm dsDNA was compared. The interaction between DNA and MB was also discussed under this condition.
Trace ion analysis of seawater by capillary electrophoresis: Determination of iodide using transient isotachophoretic preconcentration
Authors: Hirokawa Takeshi , Ichihara Teppei , Ito Kazuaki , Timerbaev Andrei R.
Published: July 2003

An improved transient isotachophoresis (tITP) procedure for the preconcentration of iodide from highly saline matrices was developed with the objective to quantify iodide in seawater by capillary electrophoresis (CE). The procedure takes advantage of introducing cetyltrimethylammonium chloride into the high‐sodium chloride background electrolyte, which due to a specific interaction with iodide amended placement of the analyte at a large distance from the matrix chloride (the latter performed the role of a leading anion). Computer simulation showed that 2‐(N‐morpholino)ethanesulfonate could be adopted as a suitable terminating ion to enable isotachophoretic focusing at the beginning of the CE run. Under optimized tITP conditions, the sensitivity response of iodide was improved by a factor of 140 over normal CE mode. This allowed for direct UV detection of as low as 0.6 μg/L iodide and made feasible CE analysis of undiluted surface seawater samples where iodide was found at a 30 μg/L level. The applicability of the proposed tITP‐CE method could apparently be extended to the determination of other trace seawater anions (e.g., iodate).
Two‐dimensional molecular profiling of mantle cell lymphoma
Authors: Antonucci Francesca , Chilosi Marco , Parolini Claudia , Hamdan Mahmoud , Astner Hubert , Righetti Pier Giorgio
Published: July 2003

The present research establishes standard two‐dimensional (2‐D) maps for control, reactive lymph node and non‐Hodgkin's lymphoma (mantle cell lymphoma, MCL). Medium sensitivity, mass spectrometry compatible colloidal Coomassie has revealed a total of ca. 750 spots in each of the maps. Comparison of 2‐D maps by statistical packages, such as the PDQuest, established up‐ and downregulation of a total of ca. 145 spots, with positive variations of up to 10‐folds and negative variations of up to 13‐folds in both MCL biopsies' protein extracts. Qualitative and quantitative variations in the two lymphoma samples are consistent. More than 20 proteins have been so far identified by matrix assisted laser desorption/ionisation‐time of flight (MALDI‐TOF)‐mass spectrometry, with an additional five spots, which gave very good spectra but could not be matched to any of the presently available databases. Some of the spots, such as the 78 kDa glucose‐regulated protein precursor and the glutathione S‐transferase P, appear to be in common with other tumors, such as lung adenocarcinoma. Others may simply reflect overall changes in cellular metabolism and growth rate that occur during malignancy and thus might turn out to be in common with any cell population receiving any kind of stress. Some (notably T‐cell leukemia/lymphoma protein 1A, TCL1, found to be 10‐fold overexpressed) appear to be specific of the non‐Hodgkin's lymphoma here studied. Western blot and immunohistochemical analyses were applied to obtain further information about stathmin (Op18) and TCL1, respectively.