bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractCationic 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

AbstractA 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

AbstractIn 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

AbstractMycobacterium 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

AbstractThe 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

AbstractAssuming 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

Abstractβ‐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

AbstractThe 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

AbstractOzonolysis 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

AbstractFour 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

AbstractStereoselective 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

AbstractThe 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

AbstractThe 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

AbstractVoltammetric 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractEpinephrine (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

AbstractThe 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

AbstractAn 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).