bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enantioselective Reduction of Ketones
Authors: Itsuno Shinichi 
Published: April 2004

AbstractEnantioselective reduction of prochiral ketones is among the most important methods for preparing enantioenriched secondary alcohols, which are important starting materials for a number of enantiopure compounds, including natural products. Various methods for enantioselective reduction of ketones have been developed for producing enantioenriched alcohols. These methods involve the use of both stoichiometric reagents and catalytic reductions. Metal hydride reagents such as lithium aluminum hydride (LAH) and sodium borohydride (NaBH4) are easily modified by enantiopure compounds. For example, binaphthol‐modified aluminum hydride reagent (BINAL‐H) is a derivative of LAH in which the enantiopure diol 1,1′‐bi‐2‐naphthol and one other alcohol replace three of the hydrogens. This reagent achieves high selectivity in many ketone reductions. The other impressive area of success is the use of enantiopure alkylboranes. The β hydride of enantiopure alkylboranes is delivered selectively, often exclusively, to one face of the carbonyl group of a ketone.Despite remarkable success with stoichiometric reagents, their important drawback is that at least one equivalent of reagent is required for reduction of the ketone. Thus catalytic processes are desirable for enantioselective ketone reduction as well as for other asymmetric transformations. Hydrogenation and hydrosilylation of ketones are catalyzed by transition metal catalysts. Enantiopure ligand‐transition metal complexes can be used as asymmetric catalysts for these reactions. Recent research makes it possible to achieve high enantioselectivity, not only for the reduction of functionalized ketones in which a transition metal can coordinate to an adjacent functional group, but also for simple ketones such as acetophenone. One of the most remarkable catalytic systems described in recent years is borane reduction in the presence of an oxazaborolidine, which contains adjacent donor (nitrogen) and acceptor (boron) sites. Many biologically active compounds have been synthesized by using oxazaborolidine‐catalyzed borane reductions of ketones as the key step. Asymmetric reduction with enzymes is another important method. Some baker's yeast mediated ketone reductions have practical applicability.This chapter addresses the enantioselective reduction of ketones by various methods including chirally modified hydride reductions, oxazaborolidine catalyzed reductions, Meerwein‐Ponndorf‐Verley (MPV) reductions, hydrogenations, hydrosilylations, and enzymatic reductions.
Intermolecular Metal‐Catalyzed Carbenoid Cyclopropanations
Authors: Davies Huw M. L. , Antoulinakis Evan G. 
Published: April 2004

AbstractThe metal‐catalyzed decomposition of diazo compounds in the presence of alkenes is a well‐established reaction. Since the originalOrganic Reactionsreview on the reaction of ethyl diazoacetate with alkenes and aromatic compounds in 1970, several new developments have revolutionized this area of chemistry. Most notably, major advances have been made in catalyst design such that highly chemoselective, diastereoselective and enantioselective carbenoid transformations can now be achieved. Furthermore, it has been recognized that a wide array of carbenoid structures can be utilized in this chemistry, leading to a broad range of synthetic applications.This chapter comprises coverage of the metal‐catalyzed intermolecular cyclopropanations of diazo compounds containing at least one adjacent electron‐withdrawing group. The coverage of diazoacetate chemistry will be limited to material since 1970 because the previousOrganic Reactionsreview covers the earlier literature. The alkene component is limited to alkenes, dienes, furans, and pyrroles because these are the systems that have resulted in the greatest developments since the 1970 review. Metal‐carbenoid intermediates derived from diazo compounds undergo a variety of useful reactions, including cyclopropanation, insertion, and ylide formation. In recent years several excellent reviews have appeared on various aspects of this chemistry. Three recent reviews have focused on asymmetric intermolecular cyclopropanations. Several books and reviews on carbenoid chemistry have major sections on intermolecular cyclopropanations. Because of the historical central prominence of carbenoids derived from diazoacetates, most reviews have tended to focus on this class of carbenoids. In this chapter, a comparison is presented of the chemical differences that exist among the major classes of carbenoids that contain adjacent electron‐withdrawing groups. The extensive nature of the topic precludes coverage of related reactions such as the metal‐catalyzed decomposition of diazoalkanes, phenyldiazoalkanes, or vinyldiazoalkanes that lack adjacent electron‐withdrawing functionality. Other cyclopropanation reactions such as the Simmons‐Smith reaction, photochemical or thermal decomposition of diazo compounds in the presence of alkenes, and cyclopropanation using stoichiometric metal carbenes are not covered.
Oxidation of Phenolic Compounds with Organohypervalent Iodine Reagents
Authors: Moriarty Robert M. , Om Prakash  
Published: April 2004

AbstractThe oxidation of phenols is a key biochemical process in oxidative phosphorylation, and it is also important in numerous biosynthetic pathways. Controlled oxidative transformations of substituted phenols are found in many synthetic organic sequences. Accordingly, a large number of oxidizing agents for phenols have been developed. Useful reagents include Fremy's salt (KSO3)2NO,and a wide variety of other redox metal‐based oxidants such as Pb(IV), Mn(III), Tl(III), Cu(II), and Fe(III). Recently, organohypervalent iodine reagents have emerged as particularly useful agents for oxidizing phenols. In the area of natural product synthesis, organohypervalent iodine reagents have been used extensively to effect oxidative intramolecular bicyclization and spirocyclization. The focus of this chapter is on synthetic applications. The chapter also covers formation and applications of phenolic iodonium ylides.The processes that occur during the oxidation of phenols with organohypervalent iodine reagents can be divided into two categories. The first category involves ligand exchange of the phenolic proton with the hypervalent iodine reagent to generate the O‐I(III) intermediate, which is subsequently transformed to various products, depending upon the reaction conditions.These transformations include oxidation of phenols to quinones and related compounds, formation of spirocyclic and oxygen heterocyclic compounds via oxidative intramolecular participation reactions, and intramolecular carbon‐carbon bond formation via phenolic oxidative coupling. All of these reactions are driven by the reduction of iodine(III) [or iodine(V)] to iodine(I) (iodobenzene).A second class of reactions that is discussed in this chapter includes formation of stable iodonium salts and ylides, which are important intermediates in organic synthesis. These reactions occur via carbon‐I(III) bond formation without loss of iodobenzene.
Effect of imidization conditions on the morphology of polyimide
Authors: Huang Jiann‐Wen , Kang Chiun‐Chia 
Published: April 2004

AbstractA poly(amic acid) derived from pyromellitic dianhydride and oxydianiline was imidized under different conditions. The sample imidized in solution (PI‐1) showed the X‐ray diffraction pattern of a crystalline material, whereas that of the sample imidized in the solid state was essentially amorphous. Both samples were further characterized by 13C‐NMR spectroscopy, IR spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The orders of polyimide in both the crystalline and amorphous states are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1065–1070, 2004
Conductivity of layer and matrix polyaniline–silver–copper composites by plasma
Authors: Cruz G. J. , Palacios J. C. , Olayo M. G. , Morales J. , Olayo R. 
Published: April 2004

AbstractThis work presents a study on the formation of polymer–metal composites by means of plasma, combining silver and copper alloys with semiconducting polymer films. The objective is to improve the electric conductivity of polyanilines by forming layer and matrix composites. In this way, it is possible to increase the superficial and/or volumetric conductivity of the polymers. Electronic variables as the electronic density and energy along the reactor and their influence on the chemical composition, deposition rate, and the morphology of plasma polymer–metal composites are taken into consideration in the course of this study, as the shower of the most energetic particles in the plasma can produce multiple bonds between the metals and the polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1031–1036, 2004
Laser dye diffusion in polymer solutions studied by spectrophotometry
Authors: Marigoudar Prabhugouda , Lagare Mahaveer T. , Mallikarjuna Nadagouda N. , Aminabhavi Tejraj M. 
Published: April 2004

AbstractA mathematical approach based on the combined application of Fick's law of diffusion and the Beer–Lambert law was used to measure the diffusion coefficient of dyes viz., coumarin 515 [3‐(1‐methylbenzimidazol‐2‐yl)‐7‐diethylaminocoumarin], POPOP [1,4‐bis (5‐phenyloxazolyl‐2‐yl) benzene], and exalite 416 {1,1,1′,1′‐tetraethyl‐5,5′‐diparaanisyl‐[2,3:5,6] diindanobenzene} in solutions of polystyrene and poly(methyl methacrylate) in 1,4‐dioxane. Diffusion data agreed well with the published results obtained using other techniques. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1157–1165, 2004
Electros: Development of an educational software for simulations in electrostatic
Authors: Martínez‐Jiménez P. , Casado E. 
Published: April 2004

AbstractThis is an introduction to the main design features of a computer‐aided educational package addressed to students of the first years of sciences and engineering. The package includes interrelated tutorials, computer simulation, and self‐evaluators, in which graphical output, hypertext, and animations are widely used. The package is devoted to the study of electrostatic fields and potentials produced by charged dielectrics arbitrarily located by the user in three‐dimensional space. It provides instant numerical evaluation and a graphical display of the electric field and potentials of the charge distribution created by the user, and permits its investigation with probe charges. The software presented in this paper has all the features we consider important for any educational software of physical phenomena simulation: an integrative character, self‐evaluation tests, personalized and active learning process, adaptability to teacher's aims, versatility as a teaching tool, multimedia resources, and simplicity. All these features will be explained in the following sections. © 2004 Wiley Periodicals, Inc. Comput Appl Eng Educ 12: 65–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.10050
The Influence of Fluorinated Molecules (Semiochemicals and Enzyme Substrate Analogues) on the Insect Communication System
Authors: Pesenti Cristina , Viani Fiorenza 
Published: April 2004

AbstractCan the introduction of fluorine atoms affect the bioactivity of natural semiochemicals? Can fluorine contribute in the creation of specific enzyme inhibitors to interrupt or disrupt the insect communication system? The first step for the bioactivity of a molecule is interaction with the biological sensor. Hydrogen and fluorine are almost bioisosteric and the receptor site of the enzyme can still recognize and accept the fluoro analogue of its natural substrate. However, the peculiar electronegativity of the fluorine atom can affect the binding, absorption, and transport of the molecule. The differences in the molecule's electronic properties can lead to differences in the chemical interactions between the receptor and the fluorinated substrate. Fluorine introduction can modify the metabolic stability and pathway of the semiochemicals in many different ways. Fluorinated analogues can show synergism, inhibition, or hyperagonism effects on insect behaviors, that is, the activity of the nonfluorinated parent compounds can be mimicked, lost, or increased. In any case, the fluorinated molecules can interact with the bioreceptors in a new and disrupting way. The semiochemicals are olfactory substances: fluorine can affect their volatility or smell. Production of semiochemicals from exogenous substances, perception at antennal receptors, and processing of biological responses are the main steps of communication among insects. In the production step, the fluorinated molecules can interact with enzymes that catalyze the biosynthesis of the natural pheromones. In the perception step, fluorinated semiochemicals can interact with the olfactory receptor cells; this often leads to totally unpredictable behaviors. Fluorinated molecules have been developed as probes to elucidate the complex chemorecognition processes of insects. Many of these molecules have been tested to find highly effective behavior‐modifying chemicals. New analogues have been synthesized to investigate the metabolic pathway of a pheromone molecule and many of them are promising disrupting agents. Despite such titanic research efforts, the results have often been random, rational trends in the induced behaviors have sometimes been impossible to find, and practical applications of the fluorinated semiochemicals are still uncertain.
Chlamydia trachomatis and invasive cervical cancer: A pooled analysis of the IARC multicentric case‐control study
Authors: Smith Jennifer S. , Bosetti Cristina , Muñoz Nubia , Herrero Rolando , Bosch F. Xavier , Eluf‐Neto José , Meijer Chris J.L.M. , van den Brule Adriaan J.C. , Franceschi Silvia , Peeling Rosanna W. 
Published: April 2004

AbstractTo determine whether Chlamydia trachomatis infection is consistently associated with an increased risk of invasive cervical carcinoma (ICC) after accounting for the strong effect of human papillomavirus (HPV) infection, a case‐control study of 1,238 cases of ICC and 1,100 control women from 7 countries was carried out (hospital‐based studies in Thailand, the Philippines, Morocco, Peru, Brazil and population‐based studies in Colombia and Spain, all coordinated by the International Agency for Research on Cancer, Lyon, France). C. trachomatis serum antibody detection was made by means of a microfluorescence assay. Among HPV DNA‐positive cases and controls, the risk of squamous cell ICC was elevated in C. trachomatis seropositive women (OR = 1.8; 95% CI = 1.2–2.7) after adjustment for age, center, oral contraceptive use, history of Pap smears, number of full‐term pregnancies and herpes simplex virus 2 seropositivity. The effect of C. trachomatis seropositivity on squamous cell ICC risk increased with increasing C. trachomatis antibody titers and was higher in women under 55 years of age. C. trachomatis antibodies were not associated with adeno‐ or adenosquamous cell carcinoma (OR = 1.0; 95% CI = 0.53–1.9) in HPV DNA‐positive women. An association of C. trachomatis with squamous cell ICC was found among all cases and control women with or without adjustment for HPV. © 2004 Wiley‐Liss, Inc.
Temporal Variations in Fine Sand Assemblages in the North Aegean Sea (Eastern Mediterranean)
Authors: Kourelea Evdokia , Vafidis Dimitrios , Chintiroglou Chariton‐Charles , Trontsios Georgios , Chicharo Louis 
Published: April 2004

AbstractTwo sites were selected in the North Aegean Sea for the study of shallow fine sand assemblages, which are poorly known in the Eastern Mediterranean. The biomonitoring of these sites can provide useful information on the impact of human activities on the macrofaunal and meiofaunal composition of these assemblages. In order to examine this impact, sampling took place in five different periods between 2000 and 2001. The qualitative and quantitative compositions of the communities at the two sites showed certain differences, mostly between the sites and the year of sampling rather than between sampling periods, which would be the expected outcome. The communities seem to be affected by a combination of the human activities with the particular hydrodynamics of the studied sites.
Reproductive toxic effect of bisphenol A dimethacrylate in mice
Authors: Darmani Homa , Al‐Hiyasat Ahmad S. 
Published: April 2004

AbstractThe current study evaluated the effect of bisphenol A dimethacrylate (Bis‐DMA) on mouse fertility. Adult male and female mice were exposed to intragastric Bis‐DMA (0, 5, 25, and 100 μg/kg) daily for 28 days and then mated with sexually mature untreated mice and after mating fertility was assessed. Females mated by males that had been exposed to Bis‐DMA had significant reductions in pregnancy rates and significant increases in the total number of resorptions out of the total number of implantations. Bis‐DMA exposed males had significant reductions in body weights and relative testes weights and significant increases in seminal vesicle and preputial gland weights. Testicular and epididymal sperm counts as well as the efficiency of sperm production were also significantly reduced in these groups. Female mice exposed to Bis‐DMA showed significant reductions in pregnancy rates, number of implantation sites, number of viable fetuses, and total number of resorptions out of the total number of implantations. Significant reductions in the body weights were observed at all doses, and significant increases were found in the relative weights of the ovaries and the uterus. The results suggest that Bis‐DMA has adverse effects on the fertility and reproductive systems of male and female mice. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 637–643, 2004
Surface modification of titanium implant by microarc oxidation and hydrothermal treatment
Authors: Huang Ping , Zhang Yong , Xu Kewei , Han Yong 
Published: April 2004

AbstractSurface modification of titanium implant is processed by microarc oxidation and hydrothermal treatment. A porous surface with a biologically active bone‐like apatite layer was formed. The apatite layer consists of very fine crystals and high crystallinity and is integrated with the titanium alloy substrate with a graded structure without a distinct interface. Such a bioactive layer is expected not only to enhance the bony ingrowth into the porous structure, but also to improve the interlocking between implant and bone. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 187–190, 2004
Prenatal sonographic diagnosis of acrania associated with amniotic bands
Authors: Chen Chih‐Ping , Chang Tung‐Yao , Lin Yi‐Hui , Wang Wayseen 
Published: April 2004

AbstractWe describe the prenatal sonographic findings in 2 cases of amniotic band sequence‐related acrania. In the first case, sonography demonstrated acrania, asymmetric facial clefts, and digital fusion on the hands and feet. In the second case, sonography demonstrated acrania and amniotic bands adhering to the brain, face, and body. This report highlights the importance of a careful search for amniotic bands and a detailed survey of the fetus' face, digits, and body in the sonographic evaluation of fetal acrania. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:256–260, 2004; Published online in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/jcu.20021
Young adult survivors of childhood acute lymphoblastic leukemia: Spontaneous GH secretion in relation to CNS radiation
Authors: Jarfelt M. , Bjarnason R. , Lannering B. 
Published: April 2004

AbstractBackgroundYoung adults who are long‐term survivors of acute lymphoblastic leukaemia (ALL) in early childhood usually do well and do not have to go to regular medical checkups. Many of these survivors did receive prophylactic cranial radiotherapy during their oncological treatment. The effect of cranial irradiation on the hypothalamus is considered to be progressive. Therefore, late effects, such as reduced growth hormone (GH) secretion, may remain undetected until adulthood.ProcedureRecords from all patients treated for ALL before the onset of puberty in the region of West Sweden, between 1 January 1973 and 31 December 1985 were included, provided they were in first remission with a minimum follow‐up time of 15 years, and a minimum age of 20. These criteria were met by 47 young adults aged 20–32 years, of whom 35 agreed to participate. We studied spontaneous GH secretion over 24 hr, IGF‐I and IGFBP‐3, final height and BMI. The patients had been treated according to three consecutive Swedish childhood leukaemia group protocols. The median follow‐up time was 20 years, and 19 of the patients had been treated with cranial irradiation (CRT+), 16 had not (CRT−).ResultsCRT+ patients had significantly lower maximal peaks of GH than CRT− patients. Fifty percent of the CRT+ patients had a GHmax below the cut‐off level (3.3 μg/l), for GH treatment. CRT− patients all had GHmax levels considered within the normal range. Final height of all the patients, except one CRT+ women, was in the range of expected midparental height, the median loss in final height in the CRT+ patients was 0.8 standard deviation (SD). No patient in this study was obese by definition (BMI <30 kg/m2). IGF‐I and IGFBP‐3 concentrations did not correlate to variations in spontaneous GH secretion in these patients.ConclusionsIn spite of the little effect on final height, we found impaired spontaneous GH secretion in 79% of young adults 20–32 years of age, and GH deficiency (GHD) in 47% after low‐dose cranial irradiation in early childhood. The consequences of this low‐GH secretion need to be investigated. Pediatr Blood Cancer 2004;42:582–588. © 2004 Wiley‐Liss, Inc.
Flow modeling and simulation for vacuum assisted resin transfer molding process with the equivalent permeability method
Authors: Chen Renliang , Dong Chensong , Liang Zhiyong , Zhang Chuck , Wang Ben 
Published: April 2004

AbstractVacuum assisted resin transfer molding (VARTM) offers numerous advantages over traditional resin transfer molding, such as lower tooling costs, shorter mold filling time and better scalability for large structures. In the VARTM process, complete filling of the mold with adequate wet‐out of the fibrous preform has a critical impact on the process efficiency and product quality. Simulation is a powerful tool for understanding the resin flow in the VARTM process. However, conventional three‐dimensional Control Volume/Finite Element Method (CV/FEM) based simulation models often require extensive computations, and their application to process modeling of large part fabrication is limited. This paper introduces a new approach to model the flow in the VARTM process based on the concept of equivalent permeability to significantly reduce computation time for VARTM flow simulation of large parts. The equivalent permeability model of high permeable medium (HPM) proposed in the study can significantly increase convergence efficiency of simulation by properly adjusting the aspect ratio of HPM elements. The equivalent permeability model of flow channel can simplify the computational model of the CV/FEM simulation for VARTM processes. This new modeling technique was validated by the results from conventional 3D computational methods and experiments. The model was further validated with a case study of an automobile hood component fabrication. The flow simulation results of the equivalent permeability models were in agreement with those from experiments. The results indicate that the computational time required by this new approach was greatly reduced compared to that by the conventional 3D CV/FEM simulation model, while maintaining the accuracy, of filling time and flow pattern. This approach makes the flow simulation of large VARTM parts with 3D CV/FEM method computationally feasible and may help broaden the application base of the process simulation. Polym. Compos. 25:146–164, 2004. © 2004 Society of Plastics Engineers.