bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Cyclotrimerisation of Enantiopure vic‐Bromo(trimethylstannyl)bicycloalkenes Derived from (+)‐Camphor, (+)‐Fenchocamphorone and (−)‐Epicamphor: Effect of the Bridgehead Methyl Group on the syn/anti Product Ratios
Authors: Fabris Fabrizio , Zambrini Laura , Rosso Enrico , De Lucchi Ottorino 
Published: July 2004

AbstractThe influence of the bridgehead methyl group on syn/anti diastereoselectivity in the cyclotrimerisation of polycyclic alkenes was investigated. To this end, three different enantiopure vic‐bromo(trimethylstannyl)‐substituted bicyclic olefins were prepared and used as probes. The effects of different copper(II) or ‐(I) salts were studied, and most dimeric intermediates were independently synthesised and characterised. Some indications of the mechanism of cyclotrimerisation were furnished by experiments aimed at determining the relative rates of dimerisation. The results gave useful indications of how to achieve highly effective syn‐cyclotrimerisation reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Self‐Assembly of Octaaminoamido Derivatives of Resorcin[4]arene in Water − A “Cell‐Like” Submicron‐Scale Hydrogel Structure
Authors: Kazakova Ella K. , Morozova Julia E. , Prosvirkin Alexander V. , Pich Andrij Z. , Gubanov Eduard P. , Muslinkin Abdurakhim A. , Habicher Wolf D. , Konovalov Alexander I. 
Published: July 2004

AbstractWe have prepared four new octaaminoamide resorcin[4]arenes having hydrocarbon chains of different lengths (1, 2: R = CH3; 3, 4: R = C11H23) and different terminal groups (1, 3: NH2; 2, 4: NMe2). The surface tension and self‐assembly of aqueous solutions of 2−4 were studied and their critical micelle concentrations (CMC) were determined. At the water/air interface, compound 2 forms a multilayer structure, whereas compound 3 forms a bilayer and compound 4 a monolayer structure. In addition, we found that compound 3 has a second CMC (CMC2). A dynamic light scattering study indicated that, at a concentration of 0.1 wt% (i.e., > CMC2), 3 forms nanodimensional aggregates; increasing the concentration up to 1.2 wt% results in the formation of strong transparent gels. For hydrogels having 5 wt% of 3, SEM images demonstrated the formation of submicron‐scale “cell‐like” aggregates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A Cyclic Vicinal Bis(tetraketone) and Structural Investigations of Formoins
Authors: Peter Matthias , Gleiter Rolf , Rominger Frank , Oeser Thomas 
Published: July 2004

AbstractInvestigations of simple formoins such as 2,5‐bis(1,1‐dimethyl‐2‐phenylethyl)‐2,4‐dihydroxyfuran‐3(2H)‐one (17), benzoylformoin (18), p‐toluoylformoin (19), pivaloylformoin (20), and the 2,4‐dihydroxy‐2,5‐bis(heterocycl‐2‐yl)furan‐3‐ones 21−23 (heterocycle = furan, thiophene, selenophene) by NMR spectroscopy in DMSO showed the dihydroxyfuranone skeleton and not an enediol structure. The formoin 17 was oxidized to the corresponding tetraketone 10. The intermolecular double benzoin condensation of 1,4‐bis(2,2dimethyl‐3,4‐dioxobutyl)benzene (27) affords, in low yield, the bis(formoin) 29, and this could be oxidized to provide 2,2,2′,2′,7,7,7′,7′‐octamethyl[8.8]paracyclophan‐3,3′,4,4′5,5′6,6′‐octaone (9). The molecular structures of 17 and 29, the monohydrate of 10 (30), and also the dihydrate of 9 (31) are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Stereoselective Synthesis of Enantiomerically Pure Piperidine Derivatives by N‐Galactosylation of Pyridones
Authors: Klegraf Ellen , Follmann Markus , Schollmeyer Dieter , Kunz Horst 
Published: July 2004

AbstractStereoselective desymmetrization of 4‐pyridone has been achieved through selective N‐galactosylation, activation of the N‐(galactosyl)pyridone by O‐silylation and immediate addition of Grignard compounds. Chiral piperidine derivatives, e.g. (S)‐(+)‐coniine and (5S,9S)‐(+)‐indolozidine 167B, were synthesised in enantiomerically pure form using these highly regio‐ and stereoselective reactions. After N‐galactosylation of 2‐pyridone and O‐silylation of the N‐galactosyl‐2‐pyridone, addition of a Grignard compound proceeded with high 1,4‐regioselectivity and complete diastereoselectivity, to furnish 4‐substituted 5,6‐dehydro‐2‐piperidones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
pH Effects on Ethanolysis of Some Arenediazonium Ions: Evidence for Homolytic Dediazoniation Proceeding through Formation of Transient Diazo Ethers
Authors: Pazo‐Llorente Roman , Bravo‐Diaz Carlos , Gonzalez‐Romero Elisa 
Published: July 2004

AbstractThe effects of pH on the observed rate constants (kobsd.) and on the solvolytic dediazoniation product distributions of ethanolysis of 2‐, 3‐, and 4‐methylbenzenediazonium ions (2MBD, 3MBD, and 4MBD, respectively) were determined by a combination of spectrophotometric (UV/Vis) and chromatographic (HPLC) techniques. The variation of both kobsd. and product yields with pH follow S‐shaped curves with inflection points at pH ≈︁ 3.6, depending on solvent composition. With increasing pH, kobsd. values increase by factors of up to about 4 (2MBD), about 3 (3MBD), and about 50 (4MBD) with respect to the kobsd. values at low pH. HPLC analyses of the reaction mixtures show that only heterolytic products are obtained at low pH, indicating that solvolytic dediazoniation takes place through an ionic mechanism, but an increase in pH favors homolytic dediazoniation, with quantitative conversion into the reduction product toluene being obtained at pH ⩾ 6 (4MBD), indicating that a turnover from the heterolytic to the homolytic mechanisms is taking place under experimental conditions under which insignificant amounts of EtO− or OH− should be present in solution. The obtained S‐shaped profiles suggest that the initiation process of the homolytic pathway is the result of the formation of a highly unstable transient diazo ether complex and not by direct electron transfer from the solvent (EtOH) to the arenediazonium ions as is currently believed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Short Synthesis of New 23‐Vinyl Steroid Derivatives from Sapogenins by the Action of 9‐BBN on Vinylogous Esters
Authors: Sandoval‐Ramírez Jesús , Meza‐Reyes Socorro , del Rio Rosa E. , Vazques Fabiola Reyes‐ , Santillán Rosa Luisa , Achab Said , Bohé Luis 
Published: July 2004

AbstractSome new 16β‐acetoxy‐22,26‐epoxy‐23‐vinylcholest‐22‐ene steroid derivatives have been synthesized from sapogenins via a two‐step sequence involving the reduction of a vinylogous ester moiety by 9‐BBN, a reaction with few precedents and for which a coherent mechanistic interpretation has not been given before now. Some mechanistic insight into this reaction was gained from NMR spectroscopic evidence. A plausible general mechanistic interpretation of the action of 9‐BBN on vinylogous esters is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
An Original Approach to the Synthesis of Phosphorus‐Carbon Heterocycles − The 3‐Oxo‐2,3‐dihydro‐1,3‐oxaphospholes
Authors: Virieux David , Ciptadi Ciptadi , Bekro Yves‐Alain , Cristau Henri‐Jean 
Published: July 2004

AbstractThe synthesis of new highly functionalized phosphorus heterocycles, the 3‐oxo‐2,3‐dihydro‐1,3‐oxaphospholes, was achieved by a cyclization reaction involving malonic enolates as 1,3‐O,C‐dinucleophiles and phosphorus compounds, such as (chloromethyl)phosphinic chlorides or alkyl (chloromethyl)phosphonochloridates, as 1,2‐dielectrophiles. Owing to the structural restriction that results from the cyclic structure, the 1H NMR spectra reveal extreme values of 2JP,H coupling constants that are sensitive to the HCPO dihedral angle. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Iodinated Indole Alkaloids From Plakortis simplex − New Plakohypaphorines and an Evaluation of Their Antihistamine Activity
Authors: Borrelli Francesca , Campagnuolo Claudio , Capasso Raffaele , Fattorusso Ernesto , Taglialatela‐Scafati Orazio 
Published: July 2004

AbstractThree new iodinated tryptophan derivatives, plakohypaphorines D−F (4−6), have been isolated from the Caribbean sponge Plakortis simplex. Their structures have been determined by applying spectroscopic methods and microwave‐assisted selective dehalogenation. Compound 5 is the first naturally occurring triiodinated indole, while compound 6 is a unique metabolite because it possesses both chlorine and iodine atoms on the indole nucleus. We have evaluated the antihistamine activity of the whole series of plakohypaphorines A−F, but only the diiodinated analogues proved to be active: they display a specific antagonism of the noncompetitive type. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Synthesis and Reactivity of Group 4 Zwitterionic Complexes of the Type Mt+CH2AlCl3−: One‐Component Stereoselective Polymerization and Oligomerization Catalysts for Olefins and Acetylenes
Authors: Eisch John J. , Otieno Peter O. 
Published: July 2004

AbstractA reinvestigation of the interaction of TiCl4 with 2 equiv. of Me3Al in toluene between −78 °C and 25 °C over 24 h has now established that the ultimate black product obtained is an associated zwitterion of the type [Ti+−CH2−AlCl3−]n, supported by multinuclear NMR spectroscopy and mass spectrometric and gasometric analyses of the gases evolved (CH4, H2) upon its protolysis. Chemical reactions of the zwitterion have corroborated specific aspects of its proposed structure: 1) its methylene character, by its transformation of benzophenone into 1,1‐diphenylethylene; 2) its divalent titanium content, by the substantial reductive dimerization of benzophenone to tetraphenylethylene, and 3) its Lewis acidic Ti center, by its catalytic isomerization of trans‐stilbene oxide to 1,1‐diphenylacetaldehyde. Similar individual reactions of ZrCl4 or HfCl4 with Me3Al have led to the analogous zwitterions [Zr+−CH2−AlCl3−]n and [Hf+−CH2−AlCl3−]n, respectively. These zwitterions of Ti, Zr and Hf have been proven to be capable of the cyclotrimerization and/or polymerization of acetylenes with varying facility, as evidenced by their catalytic action on 1‐hexyne, phenylacetylene, di‐n‐butylacetylene, and diphenylacetylene. Furthermore, all three zwitterions were able to polymerize ethylene, without any added cocatalyst, with an activity following the order Zr > Ti > Hf. The Ti and Zr zwitterions effected the stereoselective polymerization of propylene to yield 50% of isotactic polymer, and all three catalysts induced the polymerization of 1‐hexene to yield 85% (Zr, Hf) or 100% (Ti) of isotactic polymer. These oligomerizations and stereoselective polymerizations of acetylenes and olefins can be rationalized through a model for the active site resembling a three‐membered metallacyclopropa(e)nium ion intermediate formed from the attack of the Group 4 metal zwitterion on the unsaturated hydrocarbon. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
C‐Glycosidic UDP‐GlcNAc Analogues as Inhibitors of UDP‐GlcNAc 2‐Epimerase
Authors: Stolz Florian , Blume Astrid , Hinderlich Stephan , Reutter Werner , Schmidt Richard R. 
Published: July 2004

AbstractThe first step in the biosynthesis of neuraminic acid, the “epimerisation” of UDP‐GlcNAc to ManNAc, is catalyzed by UDP‐GlcNAc 2‐epimerase. In this paper we report the synthesis of the C‐glycosidic UDP‐GlcNAc analogues 1−5 as substrate‐based inhibitors of this enzyme. The focus is on the optimal distance and geometry of the connection between the sugar and the UDP‐moiety, which are both important for recognition by UDP‐GlcNAc 2‐epimerase. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Enantiocontrolled Synthesis of 3‐Pyrrolines from α‐Amino Allenes
Authors: Horváth Attila , Benner Jessica , Bäckvall Jan‐E. 
Published: July 2004

AbstractCyclization of α‐amino allenes in the presence of N‐bromosuccinimide afforded pyrrolines in good yields. The products were obtained with high enantiomeric excesses when optically active allenes were used as substrates. The synthesis of a 2,5‐dehydroprolinol derivative is also presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Highly Functionalised Cyclobutanols by Samarium(II) Iodide Induced Radical Cyclisations of Carbohydrate‐Derived Unsaturated Ketones
Authors: Williams D. Bradley G. , Blann Kevin 
Published: July 2004

AbstractCertain carbohydrates have been found to be excellent precursors for the samarium diiodide‐mediated 4‐exo‐trig cyclisation reaction of their keto‐olefin derivatives, which were readily prepared in a few easy steps. The cyclisation was found to be stereoselective, affording cis products, the diastereoselective excesses of which were influenced by the nature of the protecting group employed at C5−O of the furanose sugar. The major chiral cyclobutane product of the cyclisation step was converted into an advanced intermediate for the synthesis of a nucleoside anti‐viral analogue. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The First Enantioselective Halo Aldol Reaction of Ethyl Propiolate and Aldehydes
Authors: Chen Dianjun , Timmons Cody , Liu Junying , Headley Allan , Li Guigen 
Published: July 2004

AbstractThe first enantioselective halo aldol reaction of ethyl propiolate with aldehydes has been established by using Jacobsen’s chiral cyclohexylsalen ligand. The reaction was conducted at −20 °C in dichloromethane with Et2AlI as the source of halogen and Lewis acid promoter. Excellent geometric selectivity (only the Z isomer) has been achieved for all 14 examples examined. The reaction works well with aromatic aldehydes; it also works with aliphatic aldehydes and α,β‐unsaturated aldehydes, albeit with diminished yields and ee. This method provides the first enantioselective synthesis of β‐iodo Morita−Baylis−Hillman (MBH) esters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
TMSCl‐Mediated Catalytic Carbocupration of Alkynoates: An Unprecedented and Remarkable Effect of Catalyst Loading on Highly Selective Stereochemical Induction via a TMS‐Allenoate Intermediate
Authors: Jennings Michael P. , Sawant Kailas B. 
Published: July 2004

AbstractThe TMSCl‐mediated catalytic carbocupration of alkynoates has been investigated. It has been shown that catalyst loadings as low as 30 mol% readily allow for high yields and diastereoselectivities for a series of Grignard reagents. In addition, an unprecedented and remarkable effect of catalyst loading on stereochemical induction has been observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Allylsilanes in Organic Synthesis − Recent Developments (Eur. J. Org. Chem. 15/2004)
Authors: Chabaud Laurent , James Philippe , Landais Yannick 
Published: July 2004

AbstractThe cover picture shows the “Dune of Pyla”, the highest sand dune in Europe (105 m high, 2.7 km long and 500 m wide). It is situated 70 km away from Bordeaux, where part of the research described in the Microreview by Landais et al. on p. 3173 ff. was performed. The dune is composed of 60 million m3 of sand (silicates). Silicon is the second most abundant element inside the earth crust [O2 (46%), Si (28%), Al (8%)] and is essentially present in nature as its oxidized form (SiO2). Synthetic organosilicon compounds, and more particularly allylsilanes, are very common and useful organometallic intermediates for organic synthesis. Such synthons are of economical importance due to the abundance of silicon, and are of environmental concern due to the low toxicity of organosilicon by‐products.
Genetic and Epigenetic screening for gene alterations of the chromatin‐remodeling factor, SMARCA4/BRG1, in lung tumors
Authors: Medina Pedro P. , Carretero Julian , Fraga Mario F. , Esteller Manel , Sidransky David , Sanchez‐Cespedes Montserrat 
Published: July 2004

AbstractThe SMARCA4/BRG1 gene product is a component of the SWI‐SNF chromatin‐remodeling complex and regulates gene expression by disrupting histone‐DNA contacts in an ATP‐dependent manner. Inactivating mutations of the SMARCA4 gene, on chromosome arm 19p, are present in several human cancer cell lines, including cell lines derived from lung cancers. Interestingly, loss of heterozygosity (LOH) at 19p and absence of the SMARCA4 protein have been reported in lung tumors. To evaluate further the possible contribution of SMARCA4 gene inactivation to lung carcinogenesis, we performed a complete analysis of the SMARCA4 gene to search for (a) point mutations in all 35 coding exons, including an existing splicing variant and the intron–exon boundaries, and (b) abrogation of gene expression through promoter hypermethylation by using the methylation‐specific polymerase chain reaction (MSP) assay. We selected genomic DNA from 20 lung primary tumors with LOH on 19p for the screening of point mutations and 10 lung cancer cell lines and 52 lung primary tumors for the MSP analysis. Through our mutational screening, we identified an in‐frame and germ‐line insertion of 24 bp in exon 4 whose biological relevance is unknown. This variant was not detected in the germ line of the 62 additional individuals analyzed, indicating it is not a common polymorphism. Moreover, two missense alterations were identified in the tumors of 2 patients, a somatic Gly1160Arg mutation and a Ser1176Cys mutation. Neither was present in the germ line of the 51 additional lung cancer individuals tested. Because these mutations lead to substitution of highly conserved amino acids, they may affect the ATPase function of the protein. Finally, no promoter hypermethylation was observed in any lung primary tumor or cancer cell line, indicating that this is not a major mechanism for SMARCA4 inactivation during lung carcinogenesis. In conclusion, our data revealed that somatic point mutations of the SMARCA4 gene are present in a small subset of lung tumors, although mutations affecting the ATPase domain may be a hot‐spot for SMARCA4 gene inactivation. We cannot rule out that other mechanisms, such as complete or partial deletions of the SMARCA4 gene, are contributing to the loss of the SMARCA4 protein in lung cancer. © 2004 Wiley‐Liss, Inc.
Mutational activation of the MAP3K8 protooncogene in lung cancer
Authors: Clark Adam Michael , Reynolds Steven H. , Anderson Marshall , Wiest Jonathan S. 
Published: July 2004

AbstractThe MAP3K8 protooncogene (Cot/Tpl‐2) activates the MAP kinase, SAP kinase, and NF‐κB signaling pathways. MAP3K8 mutations occur in the rat homologue, but activating mutations have yet to be identified in primary human tumors. We have identified MAP3K8 as a transforming gene from a human lung adenocarcinoma and characterized a 3′ end mutation in the cDNA. In addition, we confirmed that the mutation occurs in the original lung tumor, and we screened a series of lung cancer cell lines to determine whether the MAP3K8 mutation is a common occurrence in lung tumorigenesis. The oncogene was isolated and identified with the NIH3T3 nude mouse tumorigenicity assay and cDNA library screening. The gene was analyzed by polymerase chain reaction (PCR), single‐strand conformational polymorphism (SSCP), and 3′RACE for mutations. The mutation was localized to MAP3K8 exon 8 and confirmed in the primary tumor DNA. Both wild‐type and mutant MAP3K8 cDNAs transformed NIH3T3 cells, but the transforming activity of the mutant was much greater than that of the wild type. PCR‐SSCP screening of cell line cDNAs identified one silent polymorphism in cell line SK‐LU‐1. Although we were unable to find additional activating mutations, these data support a role for MAP3K8 activity in cellular transformation, but suggest that mutational activation of the gene is a rare event in lung cancer. © 2004 Wiley‐Liss, Inc.
Analysis of somatic APC mutations in rare extracolonic tumors of patients with familial adenomatous polyposis coli
Authors: Bläker Hendrik , Sutter Christian , Kadmon Martina , Otto Herwart F. , von Knebel‐Doeberitz Magnus , Gebert Johannes , Helmke Burkhard M. 
Published: July 2004

AbstractPatients with familial adenomatous polyposis coli (FAP) carry heterozygous mutations of the APC gene. At a young age, these patients develop multiple colorectal adenomas that consistently display a second somatic mutation in the remaining APC wild‐type allele. Inactivation of APC leads to impaired degradation of β‐catenin, thereby promoting continuous cell‐cycle progression. The role of APC inactivation in rare extracolonic tumors of FAP patients has not been characterized sufficiently. Among tissue specimen from 174 patients with known APC germ‐line mutations, we identified 8 tumors infrequently seen in FAP. To investigate the pathogenic role of APC pathway deregulation in these lesions, they were analyzed for second‐hit somatic mutations in the mutational cluster region of the APC gene. Immunohistochemistry was performed to compare the expression pattern of β‐catenin to the mutational status of the APC gene. Exon 3 of the β‐catenin gene (CTNNB1) was analyzed for activating mutations to investigate alternative mechanisms of elevated β‐catenin concentration. Although CTNNB1 mutations were not observed, second somatic APC mutations were found in 4 of the 8 tumors: a uterine adenocarcinoma, a hepatocellular adenoma, an adrenocortical adenoma, and an epidermal cyst. These tumors showed an elevated concentration of β‐catenin. No APC mutations were seen in focal nodular hyperplasia of the liver, angiofibrolipoma, and seborrheic wart. This is the first study reporting second somatic APC mutations in FAP‐associated uterine adenocarcinoma and epidermal cysts. Furthermore, our data strengthen a role for impaired APC function in the pathogenesis of adrenal and hepatic neoplasms in FAP patients. © 2004 Wiley‐Liss, Inc.
Divergent patterns of telomere maintenance mechanisms among human sarcomas: Sharply contrasting prevalence of the alternative lengthening of telomeres mechanism in Ewing's sarcomas and osteosarcomas
Authors: Ulaner Gary A. , Hoffman Andrew R. , Otero Jesse , Huang Hsuan‐Ying , Zhao Zhiquan , Mazumdar Madhu , Gorlick Richard , Meyers Paul , Healey John H. , Ladanyi Marc 
Published: July 2004

AbstractTwo types of telomere maintenance mechanisms (TMMs) have been described in human tumors: telomerase activation and alternative lengthening of telomeres (ALT). Although the vast majority of epithelial tumors rely on telomerase activation, many mesenchymal tumors rely on ALT for telomere maintenance, but within this tumor group, the TMMs used by translocation‐associated sarcomas have not been systematically studied. We studied telomere lengths and telomerase expression and activity in 30 uncultured tumor samples and in 10 cell lines of Ewing's sarcoma, a prototypical translocation‐associated sarcoma, and compared the data to an identical analysis of 60 osteosarcomas, the most common type of sarcoma lacking a specific translocation. Telomerase activity was demonstrated in 21 Ewing's sarcoma tumor samples (70%) and in 9 of 10 Ewing's sarcoma cell lines. Evidence of ALT, indicated by the presence of long and heterogeneous telomeres, was observed only in the cell line without telomerase activity and in none of the 30 Ewing's sarcoma tumor samples. The 9 Ewing's sarcoma patients whose tumors lacked detectable telomerase activity did not differ significantly from the remaining patients in age, stage, EWSR1–FLI1 fusion type, prevalence of TP53 point mutations, or overall survival. The low prevalence of ALT in Ewing's sarcoma contrasted sharply with our data on TMMs in 60 osteosarcomas, which showed ALT in 38 of 60 cases (P < 0.0001). The present study, together with emerging published data on other sarcoma types, suggests that a predominance of telomerase activation in the absence of ALT may characterize sarcomas with specific chromosomal translocations (such as Ewing's sarcoma), whereas a high prevalence of ALT appears typical of sarcomas with nonspecific complex karyotypes (such as osteosarcoma). © 2004 Wiley‐Liss, Inc.