bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Electrochemical Properties of 1,4,8,11,15,18,22,25‐Octalkylphthalocyanines Containing Four Trithiole Rings
Authors: Kimura Takeshi , Suzuki Takahiro , Takaguchi Yutaka , Yomogita Akinori , Wakahara Takatsugu , Akasaka Takeshi 
Published: December 2005

Abstract1,4,8,11,15,18,22,25‐Octalkyl‐2,3;9,10;16,17;23,24‐tetrakis(o‐xylylenedithio)phthalocyanines 4a–d (alkyl = ethyl, butyl, octyl, and dodecyl) were prepared in moderate yields by treatment of 3,6‐dialkyl‐4,5‐(o‐xylylenedithio)phthalonitriles 3a–d with lithium in n‐pentanol. Reductive removal of the four o‐xylylene groups from 4b and 4c was performed with lithium/THF/ammonia, and the octathiolate anions generated were then treated with elemental sulfur to give the new phthalocyanines 6b and 6c, respectively, each containing four trithiole rings, after partial desulfurization and ring‐contraction reactions of the corresponding phthalocyanines 5b and 5c. The structures of the phthalocyanines were determined by 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. The absorptions of the Q‐bands of 4a–d were observed at λmax ≈ 770 nm in their UV/Vis spectra, while those of 4b‐Ni, 5b, 5c, and 6c were found in a region, blue‐shifted relative to 4a–d. When the UV/Vis spectrum of 6c wasmeasured in concentrated sulfuric acid, the λmax value of its Q‐band was 887 nm (log ϵ = 4.5), which suggests that the positive charge generated on 6c strongly affects the π‐conjugation of the phthalocyanine skeleton. The ESR spectrum was observed as one broadening signal on treatment of 6c with SbCl5. The redox potentials of the phthalocyanines were determined by cyclic voltammetry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
β‐Arylthio‐α‐chloroalkyl Ethers — Novel 1,1‐Bis‐electrophiles for Geminal Alkylation
Authors: Gromov Alexey V. , Smit William A. 
Published: December 2005

AbstractA novel protocol for geminal alkylation is suggested based upon the consecutive generation of two cationoid intermediates from the easily prepared adducts of arylsulfenyl chlorides and vinyl ethers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A New Three‐Component Cascade Reaction to Yield 3‐Spirocyclopropanatedβ‐Lactams
Authors: Zanobini Alessandra , Brandi Alberto , de Meijere Armin 
Published: December 2005

AbstractA one‐pot three‐component reaction for the direct conversion of certain alkylhydroxylamine hydrochlorides 8 (alkyl = benzyl, p‐methoxybenzyl, benzhydryl, tert‐butyl), formaldehyde (9) or an alkyl glyoxylate (10) and bicyclopropylidene (2) to furnish 3‐spirocyclopropanated 2‐azetidinones 7, 11 has been developed. Microwave heating of mixtures of the three components in the presence of sodium acetate in ethanol for 15–120 min furnished the products 7, 11 in 49–78 % yield (7 examples). A new protocol for the oxidative deprotection of the 3‐spirocyclopropanated methyl 1‐(p‐methoxybenzyl)‐2‐carboxylate 11b‐Me provides the β‐lactam building block 17‐Me in 90 % yield, and the latter can be reprotected and activated with an N‐tert‐butoxycarbonyl (Boc) group in 82 % yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic‐driven microchannel flows
Authors: Chein Reiyu , Yang Yeong Chin , Lin Yushan 
Published: December 2005

AbstractIn this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic‐driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature‐dependent fluid viscosity and electroosmotic velocity.
Calibration of migration times of variable salinity samples with internal standards in capillary electrophoresis
Authors: Riaz Asif , Chung Doo Soo 
Published: December 2005

AbstractA practical approach is presented for identifying the analyte peaks stacked by transient ITP (TITP) in samples of uncontrolled salinity. For TITP with chloride ions acting as the leading electrolyte, the effect of matrix chloride of an unknown concentration was calibrated using multiple internal standards to predict the migration times of weakly acidic anionic analytes behaving as strong electrolytes to an accuracy of over 99.9%. The calibration equations for the migration time of an analyte are given as a function of the migration times of internal standards using the mobilities of the relevant ions as parameters. The effects of matrix chloride and various separation conditions such as the temperature, plug length, ionic strength, and pH of the BGE were completely eliminated from the calibration equations. In addition, the actual mobilities, determined for a standard saline sample under the working conditions, were used, and thus, there was no need to conduct supplementary experiments to determine the absolute mobilities at infinite dilution. The internal standards were dyes, which were easily identified in an auxiliary channel monitoring the absorbance at a longer wavelength. For five standard saline matrices containing 100–300 mM NaCl at intervals of 50 mM, the mean absolute error (MAE) in migration times calibrated with two internal standards was 0.4 s (n = 5×13). For an electropherogram of a real standard reference urine sample, peaks of spiked analytes were identified with an MAE of 0.9 s (n = 13) without conductivity normalizing or desalting of the sample.
Loading capacity of carrier ampholytes – based buffers in capillary electrophoresis
Authors: Busnel Jean‐Marc , Descroix Stéphanie , Godfrin Dominique , Hennion Marie‐Claire , Peltre Gabriel 
Published: December 2005

AbstractNarrow pH cuts of carrier ampholytes (CAs), originally designed for IEF, have been used as BGEs in CE. Their physicochemical properties, rather high buffering capacity and low conductivity, allow very efficient protein separations under high electric field strength. Due to their isoelectric properties, CA BGEs are expected to present a low ionic concentration and consequently a low loading capacity. In this study, we developed a simple method that allows the estimation of the loading capacity of a UV‐absorbing BGE by CE. We first characterized in terms of loading capacity, classical ammediol‐chromate UV‐absorbing BGEs and a 10 mM histidine solution, a classical isoelectric buffer. Then, the loading capacity of four different CA‐based BGEs has been assessed. Experimental results have shown that the CA‐based buffers were presenting a rather high loading capacity, comparable to classical buffer ones and far higher than the one of the 10 mM histidine solution.
The unified equation for the evaluation of first order reactions in dynamic electrophoresis
Authors: Trapp Oliver 
Published: December 2005

AbstractThe unified equation was validated for first order reactions in dynamic CE with a data set of 31 250 elution profiles. Comparison with the results from conventional iterative computer simulation revealed that the unified equation is superior in terms of success rate and precision. The unified equation was applied to determine the cis‐trans isomerization rate constants of the angiotensin converting enzyme inhibitor captopril. The separation of the rotational cis‐trans isomeric drug has been performed in an aqueous 66 mM citric acid/Tris buffer at pH 3.0 in a 50 cm polyacrylamide‐coated fused‐silica capillary. Interconversion profiles featuring pronounced plateau formation and peak broadening were observed. Activation parameters ΔH≠ and ΔS≠ were obtained from temperature‐dependent measurements between 10 and 25°C in 2.5 K steps. From the activation parameters the isomerization barriers of captopril at 37°C under acidic conditions were calculated to be ΔG≠trans→cis = 90.6 kJ/mol and ΔG≠cis→trans = 84.6 kJ/mol. By comparison of the kinetic data with the results obtained under basic conditions (pH 9.3) a mechanism of isomerization could be proposed.
Internal Nucleophilic Termination in Acid‐Mediated Polyene Cyclizations Part 4
Authors: Snowden Roger L. , Linder Simon 
Published: December 2005

AbstractTreatment of the unsaturated bicyclic homoallylic alcohols (E)‐ and (Z)‐5 and (Z)‐ and (E)‐10 and allenic alcohol 16 with an excess of ClSO3H in 2‐nitropropane or CH2Cl2 at − 80° afforded, in moderate yields (ca. 30–70%), diastereoisomer mixtures of racemic tetracyclic ethers 12a–c (Table 1) and 17a,b (Table 2), respectively. These kinetically controlled stereospecific transformations are believed to proceed via concerted or nonconcerted pathways (see Schemes 4 and 6) and the results are fully consistent with our earlier work. Representing novel didehydro bridged analogues of known, olfactively active labdane tricyclic ethers, the organoleptic properties of 12a–c and 17a,b are briefly described, especially those of 12c which, in the context of structure–activity studies, is a racemic didehydro analogue of the known ambergris odorant Ambrox®.
Synthesis of cis‐Hedione® and Methyl Jasmonate via Cascade Baylis–Hillman Reaction and Claisen Ortho Ester Rearrangement
Authors: Chapuis Christian , Büchi George H. , Wüest Hans 
Published: December 2005

AbstractThe exocyclically unsaturated conjugated keto esters 10, obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9, were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14, prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15 (Scheme 2). The key intermediates 9 were obtained either by a four‐step sequence, including acetal protection/deprotection from enone 1, in the specific case of hydroxy ketone 9a (Scheme 1), or more directly and generally by a Baylis–Hillman reaction from cyclopent‐2‐en‐1‐one (16) and the appropriate aldehydes 17 (Scheme 2). The judicious choice of these aldehydes opens versatile modifications for the stereoselective introduction of the partially cis‐ or epimerized trans‐C(2) jasmonoid side chain, while the Baylis–Hillman reaction, catalyzed by chiral [1,1′‐binaphthalene]‐2,2′‐diols (BINOLs) 19 (Scheme 3), may be efficiently conducted in a one‐pot cascade fashion including the ortho ester Claisen rearrangement.
Amphiphilic Polymethacrylate‐ and Polystyrene‐Based Chemical Delivery Systems for Damascones
Authors: Berthier Damien , Trachsel Alain , Fehr Charles , Ouali Lahoussine , Herrmann Andreas 
Published: December 2005

AbstractAmphiphilic polystyrene‐ and polymethacrylate‐based β‐acyloxy ketones were investigated as potential delivery systems for the controlled release of damascones by retro‐1,4‐addition in applications of functional perfumery. A series of random copolymers being composed of the hydrophobic damascone‐release unit and a second hydrophilic monomer were obtained by radical polymerization in organic solution by using 2,2′‐azobis[2‐methylpropanenitrile] (AIBN) as the radical source (Schemes 2 and 3). A first evaluation of the polymer conjugates in acidic or alkaline buffered aqueous solution, and in the presence of a surfactant, showed that polymethacrylates and polystyrenes having a carboxylic acid function as hydrophilic group are particularly interesting for the targeted applications (Table 2). The release of δ‐damascone (1) from polymers with poly(methacrylic acid) and poly(vinylbenzoic acid) comonomers in different stoichiometric ratios was thus followed over several days at pH 4, 7, and 9 by comparison of fluorescence probing, solvent extraction, and particle‐size measurements (Tables 3 and 4). In acidic media, the polymers were found to be stable, and almost no δ‐damascone (1) was released. In neutral or alkaline solution, where the carboxylic acid functions are deprotonated, the concentration of 1 increased over time. In the case of the polymethacrylates, the fluorescence probing experiments showed an increasing hydrophilicity of the polymer backbone with increasing fragrance release, whereas in the case of the polystyrene support, the hydrophilicity of the environment remained constant. These results suggest that the nature of the polymer backbone may have a stronger influence on the fragrance release than the ratio of hydrophilic and hydrophobic monomers in the polymer chain.
Synthesis and Optical Resolution of the Floral Odorant (±)‐2,3‐Dihydro‐2,5‐dimethyl‐1H‐indene‐2‐methanol, and Preparation of Analogues
Authors: Vial Christian , Bernardinelli Gérald , Schneider Philippe , Aizenberg Michael , Winter Béat 
Published: December 2005

AbstractThe title compound (±)‐1, a recently discovered, valuable, floral‐type odorant, has been synthesized by a straightforward procedure (Scheme 1). To determine the properties of the enantiomers of 1, their separation by preparative HPLC and the determination of their absolute configuration by X‐ray crystallography were carried out (Figure). Furthermore, the analogues 2–6 were synthesized, either from differently methylated 2‐methylindan‐1‐ones (Schemes 2 and 3) or, in the case of the 2,4,6‐trimethylated homologue 6, by a completely different synthetic approach (Scheme 4). An evaluation of (+)‐(S)‐1, (−)‐(R)‐1, and (±)‐1 showed only minor differences in terms of odor (Table).
Synthesis and Odor Properties of Substituted Indane‐2‐carboxaldehydes. Discovery of a New Floral (Muguet) Fragrance Alcohol
Authors: Winter Béat , Gallo‐Flückiger Sandrine 
Published: December 2005

AbstractEight substituted indane‐2‐carboxaldehydes (= 2,3‐dihydro‐1H‐indene‐2‐carboxaldehydes), related to conformationally constrained analogues of floral‐type odorants, were synthesized in order to examine the effect of modifying the lipophilic part of the odorants (Schemes 1 and 2). None of the modified compounds showed better olfactive properties than the original ones (Tables 1 and 2), but an intermediate alcohol, 29, revealed itself as a valuable new member in the family of floral muguet (lily‐of‐the‐valley)‐type odorants.
Aldols by Michael Addition: Application of the retro‐Michael Addition to the Slow Release of Enones
Authors: Fehr Charles , Galindo José 
Published: December 2005

AbstractThe reversibility of Michael additions was exploited to create Michael adduct profragrances of several enones. Some of them proved to exhibit interesting properties. The synthesis of aldols (3‐hydroxy ketones) by Michael addition also opens a ready access to 1,3‐diketones.
Intercalating Nucleic Acids with Insertion of 5‐[(Pyren‐1‐yl)methylidene]hydantoin‐Substituted Butane‐1,2‐diol
Authors: Aly Youssef Lotfy , Wamberg Michael , Pedersen Erik B. 
Published: December 2005

AbstractIsopropylidene‐protected (S)‐4‐O‐(methylsulfonyl)butane‐1,2,4‐triol was used for alkylation of 5‐[(pyren‐3‐yl)methylidene]hydantoin to give the N3‐monoalkylated product 4 in 29% yield together with a dialkylated product 5 in 12% yield. After deprotection, compound 4 was transformed into a dimethoxytrityl (DMT)‐protected phosphoramidite building block 9 for standard DNA synthesis. When inserted as a bulge in the triplex‐forming oligomer, compound 6 stabilizes a DNA triplex, whereas the corresponding DNA/DNA and DNA/RNA duplexes are slightly destabilized. For the triplex, fluorescence enhancement was observed at 500 nm.
7‐Oxanorbornane and Norbornane Mimics of a Distorted β‐D‐Mannopyranoside: Synthesis and Evaluation as β‐Mannosidase Inhibitors
Authors: Buser Stephan , Vasella Andrea 
Published: December 2005

AbstractThe racemic 7‐oxanorbornanyl and norbornanyl aminoalcohols 3, 4, 42, 45, and 46 were synthesized and tested as snail β‐mannosidase inhibitors. The amino tetraol 3 was obtained from the known sulfonyl acrylate 9 and furan 10. Esterification provided 11 that underwent an intramolecular Diels–Alder reaction to the 7‐oxanorbornene 12. Reduction of 12 to 13, desulfonylation, isopropylidenation, and cis‐dihydroxylation gave 16. A second isopropylidenation to 17, followed by debenzylation and a Mitsunobu–Gabriel reaction provided 19 that was deprotected via 20 to 3. Diels–Alder cycloaddition of furfuryl acetate and maleic anhydride to 21, followed by alcoholysis of the anhydride, cis‐dihydroxylation, isopropylidenation, and Barton decarboxylation gave the ester 25. Deacetylation to 26 and a Mitsunobu–Gabriel reaction led to 27 that was transformed into the N‐Boc analogue 29, reduced to the alcohol 30, and deprotected to 4. The 1‐aminonorbornane 5 was obtained from Thiele's Acid 31. Diels–Alder cycloaddition of the cyclopentadiene obtained by thermolysis of the diester 32, methanolysis of the resulting anhydride 33, dihydroxylation, isopropylidenation, Barton decarboxylation, and Curtius degradation led to the benzyl carbamate 39 that was reduced to the alcohol 40, transformed into the N‐Boc carbamate 41, and deprotected to 5. The alcohol 40 was also transformed into the benzylamine 42, aniline 45, and hydroxylamine 46. Snail β‐mannosidase was hardly inhibited by 3, 4, 42, 45, and 46. Only the amino triol 5 proved a stronger inhibitor. The inhibition by 5 depends on the pH value (at pH 3.5: Ki = 1900 μM; at pH 4.5: Ki = 340 μm; at pH 5.5: Ki = 110 μm). The results illustrate the strong dependence of the inhibition by bicyclic mimics upon the precise geometry and orientation of the amino group as determined by the scaffold. It is in keeping with the hypothesis that the reactive conformation imposed by snail β‐mannosidase is close to a 1,4B/1S3.
Aminoreduktone – Untersuchungen an Verbindungen mit dem C‐Gerüst des Dimedons und mit sekundären Aminen als Bausteinen
Authors: Schank Kurt , Glock Rebecca , Lick Carlo 
Published: December 2005

AbstractAminoreductones – Investigations on Species Containing the Carbon Arrangement of Dimedone and Secondary Amines as Building Blocks
The ozonation of 3‐(sec‐amino)‐5,5‐dimethylcyclohex‐2‐en‐1‐ones 4 was compared with the corresponding acyloxylations by diacylperoxides 5, making accessible 3‐(sec‐amino)‐reductones 9. Both types of oxygenation also led to higher‐oxygenated six‐ring carbocyclic products (7, 8, 17), ozonation being a minor reaction path, in addition to CC cleavage. The corresponding 2‐(sec‐amino)reductones 34 were generated via aminolysis of the iodonium intermediate 44 (Scheme 13), and their reductive behavior against t‐BuOCl and 3‐chloroperbenzoic acid (MCPBA) as oxidizing agents was compared. Attempts to generate the corresponding reductone 5,5‐dimethyl‐2,3‐dimorpholin‐4‐ylcyclohex‐2‐en‐1‐one (45) were unsuccessful (Scheme 13). Instead, the corresponding iodonium intermediate 44 suffered a Favorskii‐like regioselective ring contraction during aminolysis, followed by autoxidation. These unexpected reactions were confirmed by separate experiments.
Synthesis of Nonsymmetrically N,N′‐Diaryl‐Substituted 4,4′‐Bipyridinium Salts with Redox‐Tunable and Titanium Dioxide (TiO2)‐Anchoring Properties
Authors: Bongard Dirk , Möller Martin , Rao S. Nagaraja , Corr David , Walder Lorenz 
Published: December 2005

AbstractA general method for the synthesis of so far unknown nonsymmetrically substituted N‐aryl‐N′‐aryl′‐4,4′‐bipyridinium salts is presented (Scheme 1). The common intermediate in all procedures is N‐(2,4‐dinitrophenyl)‐4,4′‐bipyridinium hexafluorophosphate (1 ⋅ $\rm{\rm PF_6^ -}$). For the synthesis of nonsymmetric arylviologens, 1 ⋅ $\rm{\rm PF_6^ -}$ was arenamine‐exchanged by the Zincke reaction, and then activated at the second bipyridine N‐atom with 2,4‐dinitrophenyl 4‐methylbenzenesulfonate. The detailed preparation of the six N‐aryl‐N′‐aryl′‐viologens 21–26 is discussed (Scheme 2). The generality of the procedure is further exemplified by the synthesis of two nonsymmetrically substituted N‐aryl‐N′‐benzyl‐ (see 11 and 12), and seven N‐aryl‐N′‐alkyl‐4,4′‐bipyridinium salts (see 28–34) including substituents with metal oxide anchoring and redox tuning properties. The need for these compounds and their usage as electrochromic materials, in dendrimer synthesis, in molecular electronics, and in tunable‐redox mediators is briefly discussed. The latter adjustable property is demonstrated by the reduction potential measured by cyclic voltammetry on selected compounds (Table).
Synthesis and Properties of Oligonucleotides Containing 2,4‐Dihydroxycyclohexyl Nucleosides
Authors: Bardiot Dorothée , Rosemeyer Helmut , Lescrinier Eveline , Rozenski Jef , Van Aerschot Arthur , Herdewijn Piet 
Published: December 2005

AbstractCyclohexyl nucleosides with an adenine and uracil base have been synthesized from 2‐azidocyclohexane‐1,5‐diol. The obtained racemic nucleosides were resolved using (R)‐O‐methylmandelic acid. Short oligonucleotides were synthesized using phorphoramidite chemistry. However, these oligonucleotides do not show self‐hybridization, and duplexes are less stable than those of ribopyranosyl‐(4′ → 2′)‐oligonucleotides.
Acetogenins from the Leaves of Rollinia laurifolia
Authors: Pimenta Lucia P. S. , Nascimento Francisco C. , Boaventura Maria Amélia D. 
Published: December 2005

AbstractFrom the EtOH extract of the leaves of Rollinia laurifolia Schl. (Annonaceae), a novel acetogenin, rolifolin (= 3‐(9‐{(2R*,5S*)‐5‐[(1S*,4S*)‐1,4‐dihydroxy‐4‐{(2S*,5R*)‐5‐[(1S*)‐1‐hydroxyundecyl]tetrahydrofuran‐2‐yl}butyl]tetrahydrofuran‐2‐yl}‐2,3‐dihydroxynonyl)‐5‐methylfuran‐2(5H)‐one; 1) was isolated, together with the known acetogenin annonin‐I (2). Also, from the corresponding hexane extract, a mixture of rolilaurin (3, a novel compound), uvariamicin‐I (4), and uvariamicin‐II (5) was obtained. The structures of compounds 1–5 were elucidated by NMR and MS analysis, and relative configurations were established. Compounds 2 and 5 have never been obtained before from Rollinia.
Synthesis of a Fusion‐Isomeric Cellobionoimidazole and Its Evaluation against the syn‐Protonating Glycosidase Cel7A
Authors: Mohal Narinder , Bernet Bruno , Vasella Andrea 
Published: December 2005

AbstractThe fusion‐isomeric cellobinoimidazole 2, a potential inhibitor of the syn‐protonating β‐glycosidase Cel7A, was synthesised by Koenigs–Knorr glycosylation of the α‐D‐arabinopyranoside 32, followed by selective hydrolysis. Glycosylation of 32 with acetobromoglucose 6 proceeded with poor diastereoselectivity, giving the desired 1,3‐linked β‐d‐disaccharide 35 as minor product, besides the major 1,3‐linked α‐d‐disaccharide 36. Hg2+‐Promoted glycosylation of 32 led predominantly to the 1,2‐ortho ester 33. Sequential removal of the silyl, acetyl, and allyl groups of 35 led to a 45 : 55 equilibrium mixture 2 and the manno‐configured isomer 39. Similarly, deprotection of 36 gave a mixture of the maltonoimidazole 42 and the manno‐configured isomer 43. According to a known protocol, the glycosyl acceptor 32 was synthesised in eleven steps and an overall yield of 8–13% from D‐lyxose. The silylated arabinopyranosyl moiety of the α‐d‐glucosides 13–19, 33, 34, and 36 adopts a 4C1 conformation, while the arabinopyranosyl moiety of the β‐d‐glucosides 17 and 35 exists as a 1 : 3 mixture of 4C1 and 1C4 conformers, as a result of the combined preferred axial orientation of bulky vicinal substituents and the anomeric effect. MM3* Modelling evidences a preferred 4C1 conformation of 35 and 36, and stronger steric interactions between the pyranosyl moieties of 35. The equilibrium mixture 2/39 proved a poor inhibitor of Cel7A with an IC50 value of ca. 4 mM.