bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expanding the Field of Phosphorus‐Containing Fatty Acid Derivatives: Synthesis of 1,2‐Oxaphospholene Derivatives and Alkenyl Phosphonates from α‐Keto Allenes
Authors: Fürmeier Sandra , Lau Maureen M. L. , Lie Ken Jie Marcel S. F. , Lützen Arne , Metzger Jürgen O. 
Published: December 2003

AbstractThe first successful preparation of phosphorus‐containing heterocyclic fatty acid derivatives is described. Reaction of the C18 α‐keto allene 1 and the C18 α‐keto chloroallene 2 with trimethyl phosphite gave the 1,2‐oxaphospholene derivatives 4 and 6, respectively. Hydrolysis of 4 and 6 furnished the corresponding alkenyl phosphonate 5 and alkenyl chlorophosphonate 7, respectively. α‐Chloro‐α′‐keto allene 3 gave the oxaphospholene derivative 8. The various intermediates and products were identified by a combination of spectroscopic and spectrometric techniques. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New β,β‐Bis(benzo[b]thienyl)dehydroalanine Derivatives: Synthesis and Cyclization
Authors: Abreu Ana S. , Silva Natália O. , Ferreira Paula M. T. , Queiroz Maria‐João R. P. , Venanzi Mariano 
Published: December 2003

AbstractThe methyl ester of β,β‐dibromo‐N‐(tert‐butoxycarbonyl)dehydroalanine was synthesized by treating the methyl ester of N,N‐bis(tert‐butoxycarbonyl)dehydroalanine with trifluoroacetic acid, N‐bromosuccinimide and triethylamine. This compound was then used in Suzuki cross‐coupling reactions with several (benzo[b]thienyl)boronic acids to give the corresponding β,β‐bis(benzo[b]thienyl)dehydroalanine derivatives in good to high yields (55−90 %). After several experiments, the best conditions were shown to be: (benzo[b]thienyl)boronic acid (5 equiv.), [Pd(PPh)2Cl2] (20 mol %), Na2CO3 (4 equiv.) in DME/H2O (10:1). The Suzuki cross‐coupling products were treated with Pd(OAc)2 and Cu(OAc)2 in DMF at 160 °C to give the (benzo[b]thienyl)pyrroles in moderate to good yields (25−62 %). Other attempts were carried out using only Cu(OAc)2, the thienylpyrroles being, in some cases, isolated in lower yields. Preliminary fluorescence studies show that the (benzo[b]thienyl)pyrroles can be used as biomarkers. All of these compounds are non‐proteinogenic amino acids that can have biological activity or can be used in conformational studies in order to establish structure‐activity relationships. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Catalytic Asymmetric Hydroboration: Recent Advances and Applications in Carbon−Carbon Bond‐Forming Reactions
Authors: Crudden Cathleen M. , Edwards David 
Published: December 2003

AbstractThe metal‐catalyzed hydroboration reaction provides access to functionalized organoboron derivatives that cannot be easily prepared using traditional reagents. New developments in this reaction including neoteric reaction media and novel ligands are described in this review. A key aspect of the hydroboration reaction is the ability to further derivatize the product. Thus the conversion of boronate esters into amines, esters, alcohols, carboxylic acids and amino acids is described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Adenylate Deaminase (5′‐Adenylic Acid Deaminase, AMPDA)‐Catalyzed Deamination of 5′‐Deoxy‐5′‐Substituted and 5′‐Protected Adenosines: A Comparison with the Catalytic Activity of Adenosine Deaminase (ADA)
Authors: Ciuffreda Pierangela , Loseto Angela , Alessandrini Laura , Terraneo Giancarlo , Santaniello Enzo 
Published: December 2003

AbstractThe enzyme adenylate deaminase (AMPDA) is able to catalyze the hydrolytic deamination of 5′‐substituted and 5′‐protected 5′‐deoxyadenosines, whereas limited or no activity is shown by adenosine deaminase (ADA) towards the same substrates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cerium‐Catalyzed Reaction of β‐Dicarbonyl Compounds with Styrene and Atmospheric Oxygen
Authors: Christoffers Jens , Werner Thomas , Frey Wolfgang , Baro Angelika 
Published: December 2003

AbstractThe cerium‐catalyzed C−C coupling reaction of carbo‐ and heterocyclic β‐dicarbonyl compounds 1 with styrenes 4, using oxygen (air) as the oxidant, at ambient temperature, is reported. The reaction afforded a mixture of diastereoisomeric hydroperoxides 5 which could be transformed into the unique dioxo compounds 6 by disproportionation of the peroxo function under treatment with acetyl chloride/pyridine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Sustainable Epoxidation of Electron‐Poor Olefins with Hydrogen Peroxide in Ionic Liquids and Recovery of the Products with Supercritical CO2
Authors: Bortolini Olga , Campestrini Sandro , Conte Valeria , Fantin Giancarlo , Fogagnolo Marco , Maietti Silvia 
Published: December 2003

AbstractAn efficient procedure is described for the epoxidation of electron‐deficient olefins, in particular Vitamin K3 and analogues, with aqueous basic solutions of hydrogen peroxide in different ambient temperature ionic liquids (ILs) [bmim+][X−] {[bmim+] = 1‐butyl‐3‐methylimidazolium; [X−] = [BF4−], [CF3SO3−], [PF6−], [N(CF3SO2)2−]}. Various factors affecting epoxide yield (in the range 80−99%), reaction rate and reproducibility have been examined. The almost quantitative extraction of the epoxides from the reaction media has been obtained with supercritical CO2. The ionic liquid was then recovered and reused in subsequent cycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Mono‐N‐glycosidation of β‐Cyclodextrin − Synthesis of 6‐(β‐Cyclodextrinylamino)‐6‐deoxy‐D‐galactosides and of N‐(6‐Deoxy‐β‐cyclodextrinyl)galacto‐azepane
Authors: Bonnet Véronique , Duval Raphaël , Tran Vinh , Rabiller Claude 
Published: December 2003

AbstractAn easy route to 6‐oxogalactose and to 6‐oxogalactosides through an oxidation reaction mediated by galactose oxidase allowed the N‐glycosidation of 6‐amino‐6‐deoxy‐β‐cyclodextrin by reductive amination in the presence of NaBH3CN in DMSO. When methyl α‐D‐ and p‐nitrophenyl α‐ and β‐D‐galacto‐hexodialdo‐1,5‐pyranosides (1, 2 and 3, respectively) were used as substrates, 6‐(β‐cyclodextrinylamino)‐6‐deoxy‐D‐galactopyranosides were obtained in 25−50% yields. The same was true in the cases of 6II‐oxolactose 4 and of 6II‐oxomelibiose 5, for which the anomeric carbon was shown to be unreactive in complexation with DMSO. This reaction was also successfully applied in water with an oxidized polygalactomannan 6. The behaviour of galacto‐hexodialdo‐1,5‐pyranose 7 was different, since further intramolecular cyclisation and reduction resulted in a N‐(6‐deoxy‐β‐cyclodextrinyl)‐galacto‐azepane in good yield. Molecular modelling was also used to explain the course of this reaction. Calculations indicated that the formation of the cis D‐form of the intermediate N‐β‐CD imine of 7 was strongly preferred. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Supramolecular Complex Formation: A Study of the Interactions between β‐Cyclodextrin and Some Different Classes of Organic Compounds by ESI‐MS, Surface Tension Measurements, and UV/Vis and 1H NMR Spectroscopy
Authors: Guernelli Susanna , Laganà Maria Francesca , Mezzina Elisabetta , Ferroni Fiammetta , Siani Gabriella , Spinelli Domenico 
Published: December 2003

AbstractThe ability of several organic compounds [alcohols 1 and 2, the corresponding phosphate esters 3 and 4 and their sodium salts 5 and 6 as well as some commercial surfactants such as C14DMAO (7, zwitterionic), SDS (8, anionic) and CTABr (9, cationic)] to produce supramolecular complexes with β‐cyclodextrin has been investigated by four different techniques (ESI‐MS, surface tension measurements, UV/Vis and 1H NMR spectroscopy). The data collected have allowed information about the formation of complexes and the location of the guest in the host to be gained. Comparison of the results obtained for phosphate esters and their salts, for both saturated and unsaturated derivatives, has made it possible to evaluate the factors that affect the stability of the supramolecular complexes under the different experimental conditions used. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Hydrolysis of the Phosphonamidate Bond in Phosphono Dipeptide Analogues — the Influence of the Nature of the N‐Terminal Functional Group
Authors: Mucha Artur , Grembecka Jolanta , Cierpicki Tomasz , Kafarski Paweł 
Published: December 2003

AbstractPhosphonamidate pseudodipeptides, designed as transition state analogue inhibitors of leucine aminopeptidase, revealed unexpected instability in aqueous solutions of pH values varying from acidic up to highly basic. This reaction has been studied in some detail by means of NMR spectroscopy and it was found that the phosphonamidate stability depended strongly on the solution pH, relying on the protonation state of two crucial functional groups of the molecule — the phosphonamidate and amino moieties. Protonation of the free N‐terminal amino moiety is required for the occurrence of rapid P−N bond decomposition; N‐protected derivatives are significantly more stable. The mechanisms of the cleavage of the phosphonamidate bond have been proposed and discussed. The observed instability of unblocked P−N peptides may be the cause of the substantial limitations of their practical application as aminopeptidase inhibitors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Topochemical [2+2] Dimerization of Kinetically Stabilized 1‐Phosphaallenes in the Solid State
Authors: Ito Shigekazu , Sekiguchi Satoshi , Yoshifuji Masaaki 
Published: December 2003

AbstractThe thermolysis of two bulky 1‐phosphaallenes in the solid state afforded diphosphanylidenecyclobutane or 2,4‐dimethylene‐1,3‐diphosphacyclobutane. The regioselectivity of the [2+2] dimerization depends largely on the crystal structure of the 1‐phosphaallenes, and the reaction path seems to be affected by the presence of bulky 2,4,6‐tri‐tert‐butylphenyl (Mes*) group. This topochemical reaction was also controlled by the substituents at the 3‐position of the 1‐phosphaallene skeleton. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Developing Molecular Diversity in the Construction of a Family of Bicyclic Isoxazolines Scaffolds: Control of Regio‐and Diastereoselectivities
Authors: Giorgi Gianluca , Lampariello L. Raffaella , Minetto Giacomo , Paoli M. Laura , Riello Vincenzo , Rodriquez Manuela , Sega Alessandro 
Published: December 2003

AbstractA completely regioselective approach to bicyclic isoxazolines has been found starting from 4‐cyclopentene‐1,3‐dione or 2‐cyclopentenones. 1,3‐Dipolar cycloaddition with nitrile oxides gave different semirigid bicyclic scaffolds with at least four points of elaboration for molecular diversity. From these intermediates, two families of regioisomer isoxazolines can be prepared with complete control of their relative stereochemistry. Further elaboration of functional groups was demonstrated in order to exploit a successive parallel preparation of arrays of compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Model Studies Towards Stephaoxocanes: Construction of the 2‐Oxa‐4‐aza‐ phenalene Core of Stephaoxocanidine and Eletefine
Authors: Bianchi Darío A. , Cipulli Marcos A. , Kaufman Teodoro S. 
Published: December 2003

AbstractThe construction of the polysubstituted 1H,3H‐2‐oxa‐4‐azaphenalene 4 by means of consecutive oxa‐Pictet−Spengler and Jackson cyclizations is reported. This compound contains the ABC ring system of the novel isoquinoline alkaloids stephaoxocanidine and eletefine, found in Stephania cepharantha and Cissampelos glaberrima. Both these species are Menispermaceæ used in folk medicine in the Far East and Brazil. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003
Simultaneous Generation of Anionic and Neutral Palladium(II) Complexes from η3‐Allylpalladium Chloride Dimer and Fluorinated β‐enaminones
Authors: Bouquillon Sandrine , Bouillon Jean‐Philippe , Thomas Louis , Plantier‐Royon Richard , Chanteau Frédéric , Tinant Bernard , Hénin Françoise , Portella Charles , Muzart Jacques 
Published: December 2003

AbstractReactions between η3‐allylpalladium chloride dimer, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) and 1‐amino‐2‐fluoro‐1‐perfluoroethyl‐3‐phenylprop‐1‐en‐3‐one or 1,12‐diamino2,11‐difluoro‐1,12‐bis(perfluorobutyl)dodeca‐1,11‐diene3,10‐dione simultaneously provided two types of PdII complexes. One is an anionic η3‐allylpalladium complex with protonated DBU as counterion while the other is a neutral η3‐allyl(β‐ketoiminato)palladium complex. A mechanism involving the amidine function of DBU in the formation of the two complexes is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Transition‐Metal‐Free Sonogashira‐Type Coupling Reactions in Water
Authors: Appukkuttan Prasad , Dehaen Wim , Van der Eycken Erik 
Published: December 2003

AbstractMicrowave‐assisted transition‐metal‐free Sonogashira‐type coupling reactions are described. The reactions are run in water as the sole solvent, without the need for copper(I) or any transition‐metal−phosphane complex. The scope of the methodology was tested by reaction of a wide variety of aryl halides and heteroaryl halides. The reaction was also investigated under conventional heating conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Mechanism of the Kulinkovich Cyclopropanol Synthesis: Transfer‐Epititanation of the Alkene in Generating the Key Titanacyclopropane Intermediate
Authors: Eisch John J. , Adeosun Adetenu A. , Gitua John N. 
Published: December 2003

AbstractAn investigation of the Kulinkovich cyclopropanol synthesis, the interaction of esters with 2:1 or 3:1 mixtures of alkyl Grignard reagents and Ti(OiPr)4 at low temperatures, has been conducted, in order to ascertain which reactive intermediates are involved and how they are interconverted. Because of the nature of the ultimate product, one of the most obvious intermediates is the 1,1‐diisopropoxy‐1‐titanacyclopropane stemming from the epititanation of the alkene set free from the alkyl Grignard reagent employed. A search for the formation of such a titanocycle by warming an ethereal solution of either Et2Ti(OiPr)2 or iPr2Ti(OiPr)2 between −78 °C and +25 °C was attempted by chemical trapping with either an ester or nitrile. In this manner it was shown that such a titanocycle was formed in the case of Et2Ti(OiPr)2 but not with iPr2Ti(OiPr)2. As to the role of two other potential intermediates, Ti(OiPr)2 and R2Ti(OiPr)2, it was demonstrated that preformed Ti(OiPr)2 in the presence of ethylene and an ester does not form the corresponding cyclopropanol. Thus, under the reaction conditions Ti(OiPr)2 cannot perform the direct epimetallation necessary to produce the requisite titanacyclopropane. On the other hand, either iPr2Ti(OiPr)2 or Et2Ti(OiPr)2 can achieve the transfer‐epititanation of ethylene at low temperatures and hence with methyl benzoate yield 1‐phenyl‐1‐cyclopropanol. In contrast, neither iPr2Ti(OiPr)2 nor Et2Ti(OiPr)2 can at low temperatures transfer‐epititanate propylene. This difference in alkene reactivity can be ascribed to steric factors operating in the proposed octahedral transition state for transfer‐epimetallation. Finally, by introducing free ethylene into such Kulinkovich reaction mixtures, either by ethylene gas itself or a third equivalent of EtMgX, the isolated yields of cyclopropanols were more than doubled over those obtained with a 1:2 ratio of Ti(OiPr)4/EtMgX. From this observation one can conclude that free ethylene catalytically initiates the Kulinkovich reaction by coordinating with Et2Ti(OiPr)2 and undergoes transfer‐epititanation to produce the requisite titanacyclopropane and thereby liberates ethylene, which perpetuates the reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
DNA end sequestration by DNA‐dependent protein kinase and end joining of sterically constrained substrates in whole‐cell extracts
Authors: Lee Jae Wan , Inamdar Kedar V. , Hannah Michele F. , Lees‐Miller Susan P. , Povirk Lawrence F. 
Published: December 2003

AbstractExtracts of Xenopus eggs and of cultured human and hamster cells have the capacity to join nonhomologous DNA ends, and all do so with similar specificity. To examine the formation of repair complexes on DNA under conditions of end joining, end‐labeled fragments were incubated with the various extracts and then subjected to DNase‐I footprinting. Human and Xenopus extracts produced footprints virtually identical to that of purified DNA‐dependent protein kinase holoenzyme (Ku plus DNA‐PKcs), with protection of the terminal 28 bp. Extracts of hamster cells were more variable, but usually produced a 16‐bp footprint, similar to that of Ku alone. In all cases a 28‐bp holoenzyme‐like footprint was associated with wortmannin‐sensitive end joining, minimal 3′‐5′ exonucleolytic resection, and a predominance of accurate end‐joining products. To determine whether the short segments of DNA occupied by Ku and DNA‐PK were sufficient to support end joining, Y‐shaped substrates were constructed in which only one arm was available for end joining. A Y substrate with a 31‐bp arm bearing a partially cohesive 3′ overhang was accurately joined by a Xenopus egg extract, whereas a substrate with a 21‐bp arm was not. Surprisingly, a human cell extract did not join the Y substrates at all. The results suggest that differences in wortmannin sensitivity and in the distribution of in vitro end‐joining products may be attributable to the variations in the levels of DNA‐PKcs in the extracts. In addition, end joining in human extracts appears to involve interactions with significantly longer segments of DNA than the ∼28 bp occupied by DNA‐PK. Environ. Mol. Mutagen. 42:279–287, 2003. © 2003 Wiley‐Liss, Inc.
Genetic toxicity of methamphetamine in vitro and in human abusers
Authors: Li Jih‐Heng , Hu Heng‐Cheng , Chen Wei‐Bang , Lin Shih‐Ku 
Published: December 2003

AbstractMethamphetamine (METH) is a widely abused psychomotor stimulant. Although numerous studies have examined METH‐induced neurotoxicity, its ability to produce genotoxic effects has not been evaluated. In this article, we report on the genotoxicity of METH in vitro and in human METH abusers. METH induced his+ revertants in Salmonella typhimurium strains TA98 and TA100, and increased the frequency of hprt mutants, micronuclei, and sister chromatid exchange (SCE) in cultured Chinese hamster ovary K1 (CHO‐K1) cells. These METH‐induced genotoxic effects were eliminated if METH exposure was conducted in the presence of rat liver S9, indicating that the genotoxicity was caused by METH, and not by metabolites of METH. In addition, reactive oxygen species (ROS) scavengers inhibited the METH‐induced micronuclei in CHO‐K1 cells. Further investigation with 76 human long‐term METH abusers and 98 unexposed controls demonstrated that total METH exposure correlated with micronucleus and SCE frequencies in cultured lymphocytes. The results of this study indicate that METH is a genotoxic agent and that ROS may play a role in METH‐induced genotoxicity. Environ. Mol. Mutagen. 42:233–242, 2003. © 2003 Wiley‐Liss, Inc.
Increased transcriptional activity of the CYP3A4*1B promoter variant
Authors: Amirimani B. , Ning B. , Deitz A.C. , Weber B.L. , Kadlubar F.F. , Rebbeck T.R. 
Published: December 2003

AbstractNumerous single nucleotide polymorphisms (SNPs) have been identified in the human genome, yet the functional significance of most is unknown. CYP3A4 is a key enzyme in the metabolism of numerous compounds. An A→G substitution 290 bp upstream of the CYP3A4 transcription start site (CYP3A4*1B) has been associated with cancer phenotypes, but its phenotypic effects are unclear. To investigate the functional significance of CYP3A4*1B, we generated two luciferase reporter constructs: 1‐kb (denoted L, long) and 0.5‐kb (denoted S, short) promoter fragments containing either the variant (VL,VS) or the wild‐type (WL, WS) sequences. We evaluated the effect of the variant sequence in the HepG2 and MCF‐7 cell lines, and in primary human hepatocytes from three donors. Reporter constructs with the variant sequence had 1.2‐ to 1.9‐fold higher luciferase activity than constructs with wild‐type sequence in the cell lines (P < 0.0001) and hepatocytes (P = 0.021, P = 0.027, P = 0.061). The ratio of transcriptional activity for VS:WS was similar to the VL:WL ratio in HepG2 cells, but the VS:WS ratio was consistently less than the VL:WL ratio in MCF‐7 cells. This suggests that CYP3A4 expression is higher from the variant promoter and that a repressor sequence may exist in the longer constructs. Electrophoretic mobility shift assays demonstrated specific binding of a component of HepG2 nuclear extract to both wild‐type and variant promoters with consistently higher binding affinities to the wild‐type sequence. This suggests the existence of a transcriptional repressor responsible for the lower CYP3A4*1A activity. Therefore, the phenotypic effects of the variant CYP3A4*1B may be associated with enhanced CYP3A4 expression due to reduced binding of a transcriptional repressor. Environ. Mol. Mutagen. 42:299–305, 2003. © 2003 Wiley‐Liss, Inc.
Neural correlates of segmental and tonal information in speech perception
Authors: Gandour Jack , Xu Yisheng , Wong Donald , Dzemidzic Mario , Lowe Mark , Li Xiaojian , Tong Yunxia 
Published: December 2003

AbstractThe Chinese language provides an optimal window for investigating both segmental and suprasegmental units. The aim of this cross‐linguistic fMRI study is to elucidate neural mechanisms involved in extraction of Chinese consonants, rhymes, and tones from syllable pairs that are distinguished by only one phonetic feature (minimal) vs. those that are distinguished by two or more phonetic features (non‐minimal). Triplets of Chinese monosyllables were constructed for three tasks comparing consonants, rhymes, and tones. Each triplet consisted of two target syllables with an intervening distracter. Ten Chinese and English subjects were asked to selectively attend to targeted sub‐syllabic components and make same‐different judgments. Direct between‐group comparisons in both minimal and non‐minimal pairs reveal increased activation for the Chinese group in predominantly left‐sided frontal, parietal, and temporal regions. Within‐group comparisons of non‐minimal and minimal pairs show that frontal and parietal activity varies for each sub‐syllabic component. In the frontal lobe, the Chinese group shows bilateral activation of the anterior middle frontal gyrus (MFG) for rhymes and tones only. Within‐group comparisons of consonants, rhymes, and tones show that rhymes induce greater activation in the left posterior MFG for the Chinese group when compared to consonants and tones in non‐minimal pairs. These findings collectively support the notion of a widely distributed cortical network underlying different aspects of phonological processing. This neural network is sensitive to the phonological structure of a listener's native language. Hum. Brain Mapping 20:185–200, 2003. © 2003 Wiley‐Liss, Inc.