bluuebunny/crossref_metadata_2025 huggingface dataset:
Why not ADR? Burdened by backlogs, the system that deals with veterans' disability claims needs help
Authors: Rosenbleeth Richard M.
Published: September 2007

Citing ADR's effectiveness and civic duty, Richard M. Rosenbleeth, of Philadelphia, writes that the U.S. Department of Veterans Affairs needs to adapt programs it already uses elsewhere to deal with the backlog of injured and sick veterans' disability claims.
Angiogenin loss‐of‐function mutations in amyotrophic lateral sclerosis
Authors: Wu David , Yu Wenhao , Kishikawa Hiroko , Folkerth Rebecca D. , Iafrate A. John , Shen Yiping , Xin Winnie , Sims Katherine , Hu Guo‐fu
Published: September 2007

Objective

Heterozygous missense mutations in the coding region of angiogenin (ANG), an angiogenic ribonuclease, have been reported in amyotrophic lateral sclerosis (ALS) patients. However, the role of ANG in motor neuron physiology and the functional consequences of these mutations are unknown. We searched for new mutations and sought to define the functional consequences of these mutations.

Methods

We sequenced the coding region of ANG in an independent cohort of North American ALS patients. Identified ANG mutations were then characterized using functional assays of angiogenesis, ribonucleolysis, and nuclear translocation. We also examined expression of ANG in normal human fetal and adult spinal cords.

Results

We identified four mutations in the coding region of ANG from 298 ALS patients. Three of these mutations are present in the mature protein. Among the four mutations, P(‐4)S, S28N, and P112L are novel, and K17I has been reported previously. Functional assays show that these ANG mutations result in complete loss of function. The mutant ANG proteins are unable to induce angiogenesis because of a deficiency in ribonuclease activity, nuclear translocation, or both. As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult.

Interpretation

We provide the first evidence that ANG mutations, identified in ALS patients, are associated with functional loss of ANG activity. Moreover, strong ANG expression, in normal human fetal and adult spinal cord neurons and endothelial cells, confirms the plausibility of ANG dysfunction being relevant to the pathogenesis of ALS. Ann Neurol 2007
Organometallverbindungen von Titan und Zirconium als selektive nucleophile Reagentien für die Organische Synthese
Authors: Weidmann Beat , Seebach Dieter
Published: September 2007

Bei der Addition von carbanionoiden Organometallverbindungen (meist RLi oder RMgX) an Carbonylgruppen – einem Schlüsselschritt unzähliger Synthesen – können Komplikationen und Probleme auftreten. Abhilfe in vielen Fällen schafft die Zugabe von (RO)3TiCl, (RO)3ZrCl oder (R2N)3TiX zu den klassischen Li‐und Grignard‐Reagentien. Dabei entstehen meist stabile Organotitan‐ und Organozirconiumreagentien, die sich für hochselektive Carbonyladditionen eignen. Zum Beispiel unterscheiden sich die Geschwindigkeiten der Reaktionen von CH3Ti(OiPr)3 mit Benzaldehyd und mit Acetophenon bei Raumtemperatur um mehr als fünf Zehnerpotenzen; Reagentien RTi(OiPr)3 addieren sich glatt an Cyan‐, Nitro‐ oder Iod‐substituierte Benzaldehyde, und sie können in chlorierten Lösungsmitteln oder in Acetonitril umgesetzt werden; die Zirconiumanaloga haben eine besonders geringe Basizität und addieren sich mit hohen Ausbeuten an α‐ und β‐Tetralone oder an Substrate, die eine Nitroaldolgruppe enthalten; Einbau chiraler OR*‐Gruppen ergibt enantioselektive Reagentien (bis 90% e. e.); allylische (RO)3Ti‐Derivate reagieren völlig regioselektiv am höher substituierten C‐Atom und diastereoselektiv (bis 98% ds) auch mit Ketonen des Typs R1COR2. Neuartig sind Reaktionen wie die direkte geminale Dialkylierung (CO→CMe2) und alkylierende Aminierung [C→O→CR(NR′2)] mit Ti‐Reagentien. _ Die Modifizierung und Feineinstellung (“Zähmung”) der carbonylophilen Reaktivität muß nicht teuer erkauft werden: Ausgangsmaterialien sind die wohlfeilen und harmlosen “Zähmung”, Zirconate und zugehörigen Tetrachloride.
1‐Alkinylamine durch elektrophile Aminierung
Authors: Boche Gernot , Bernheim Michael , Nießner Manfred
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 34. DOI: 10.1002/ange.198300340
Ein neuer Zugang zu Thiocarbonyl‐Verbindungen
Authors: Schaumann Ernst , Wriede Ulrich , Rühter Gerd
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 63. DOI: 10.1002/ange.198300630
NMR‐Untersuchungen an Hefen, die auf Substraten mit “Zähmung”‐Radioaktivität kultiviert wurden
Authors: Basosi Riccardo , Rossi Claudio , Tiezzi Enzo , Valensin Gianni
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 57. DOI: 10.1002/ange.198300570
Kinetische und thermodynamische Kontrolle der Reaktion von (Ph3P)2PtO2 mit (H)‐2‐Butenal
Authors: Broadhurst Michael J. , Brown John M. , John Robert A.
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 1. DOI: 10.1002/ange.198300010
Diastereo‐ und enantioselektive Synthese von (1H,3H)‐Caronaldehydsäure‐methylester und (1H,3H)‐Chrysanthemumsäure‐methylester aus (H)‐Glycerinaldehyd‐acetonid
Authors: Mulzer Johann , Kappert Michael
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 23. DOI: 10.1002/ange.198300230
O‐Glycopeptid‐Synthese unter Verwendung von 9‐Fluorenylmethoxycarbonyl‐(Fmoc‐)geschützten Bausteinen
Authors: Schultheiß‐Reimann Petra , Kunz Horst
Published: September 2007

Das vollständige Manuskript dieser Zuschrift erscheint in: Angew. Chem. Suppl. 1983, 39. DOI: 10.1002/ange.198300390
The Renaissance of H/D Exchange
Authors: Atzrodt Jens , Derdau Volker , Fey Thorsten , Zimmermann Jochen
Published: September 2007

The increasing demand for stable isotopically labeled compounds has led to an increased interest in H/D‐exchange reactions at carbon centers. Today deuterium‐labeled compounds are used as internal standards in mass spectrometry or to help elucidate mechanistic theories. Access to these deuterated compounds takes place significantly more efficiently and more cost effectively by exchange of hydrogen by deuterium in the target molecule than by classical synthesis. This Review will concentrate on the preparative application of the H/D‐exchange reaction in the preparation of deuterium‐labeled compounds. Advances over the last ten years are brought together and critically evaluated.
Kinetic study of the decompositions involved in the thermal degradation of commercial azodicarbonamide
Authors: Reyes‐Labarta J. A. , Marcilla A.
Published: September 2007

The transitions and reactions involved in the thermal treatment of several commercial azodicarbonamides (ADC) in an inert atmosphere have been studied by dynamic thermogravimetry analysis (TGA), mass spectrometry and Fourier transform infrared (FTIR) spectroscopy. A pseudo‐mechanistic model, involving several competitive and non‐competitive reactions, has been suggested and applied to the correlation of the weight loss data. The model applied is capable of accurately representing the different processes involved, and can be of great interest in the understanding and quantification of such phenomena, including the simulation of the instantaneous amount of gases evolved in a foaming process. In addition, a brief discussion on the methodology related to the mathematical modeling of TGA data is presented, taking into account the complex thermal behaviour of the ADC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of polyacrylamide cryogels produced from a high‐molecular‐weight precursor. II. The influence of the molecular weight of the polymeric precursor
Authors: Ivanov Roman V. , Lozinsky Vladimir I. , Noh Seok Kyun , Lee Yong Rok , Han Sung Soo , Lyoo Won Seok
Published: September 2007

Polyacrylamide gels and cryogels were prepared by the crosslinking reaction of polyacrylamide (a polymeric precursor) with glutaric aldehyde (a crosslinking agent) in liquid and moderately frozen aqueous media, respectively. Polymeric precursors of different viscosity‐ averagemolecular weights (0.3, 1, 3, and 9 MDa) were used. The molecular weight of the precursors, as well as the reaction temperature and concentration of the crosslinking agent, exerted a pronounced influence on the efficiency of gelation (gel fraction yield) and on the properties (swelling capability) and structural peculiarities of the resulting gels (reference samples) and cryogels. The highest efficacy was inherent in the cryotropic gelation process when the polymeric precursor had a molecular weight of about 3 MDa, whereas the implementation of polyacrylamides of lower (0.3 or 1 MDa) or higher (9 MDa) molecular weights diminished the gel formation efficiency. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Evaluating cell wall structure and composition of developing cotton fibers using Fourier transform infrared spectroscopy and thermogravimetric analysis
Authors: Abidi Noureddine , Hequet Eric , Cabrales Luis , Gannaway John , Wilkins Thea , Wells Leslie W.
Published: September 2007

Universal attenuated total reflectance Fourier transform infrared (UATR‐FTIR) spectroscopy and thermogravimetric analysis (TGA) were used to investigate the structural changes of cotton (Gossypium hirsutum L.) fibers as a function of developmental programming. The presence of noncellulosic compounds (wax, protein, hemicelluloses, pectic substances, amino acids, etc.) was evident from FTIR spectra of fibers at 10, 14, 17, and 20 dpa (day postanthesis). The vibration corresponding to the noncellulosic compounds disappeared at 36 dpa. Furthermore, independent TGA analysis supported the results obtained with FTIR, showing that the transition from primary cell wall synthesis to secondary cell wall synthesis occurs at or around 20 dpa. This study is the first to report on the use of the UATR‐FTIR and TGA to elucidate structural changes during cotton fiber development. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Functional properties of thermoformed wheat gluten/montmorillonite materials with respect to formulation and processing conditions
Authors: Angellier‐Coussy Hélène , Torres‐Giner Sergio , Morel Marie‐Hélène , Gontard Nathalie , Gastaldi Emmanuelle
Published: September 2007

Wheat gluten (WG)/montmorillonite (MMT) films were prepared by a thermomechanical process consisting of first mixing the components in a two‐blade, counter‐rotating device and second thermoforming the obtained dough. A significant loss in protein solubility due to the formation and rearrangement of disulfide bonds was observed upon mixing and thermoforming. In the range of studied glycerol contents (25–42.8 wt %), it was shown that glycerol had no significant effect on the mechanical properties or water sensitivity of WG‐based films. Increasing the thermoforming temperature from 60 to 120°C led to considerable improvements of the mechanical properties (increases in both the stress and strain at break) and a significant reduction of the water sensitivity. The introduction of MMT (up to 5 wt %) allowed the achievement of mechanical properties that were not possible by just the variation of the glycerol content and the processing temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation of a heterogeneous hollow‐fiber affinity membrane having a mercapto chelating resin and its recovery of Hg2+ cations
Authors: Wang Bing , Liu Wei , Huang Lei
Published: September 2007

A kind of heterogeneous hollow‐fiber affinity filter membrane with a high chelating capacity for Hg2+ was prepared by phase separation with blends of a mercapto chelating resin and polysulfone as the membrane materials, N,N‐dimethylacetamide as the solvent, and water as the extraction solvent. The adsorption isotherms of the hollow‐fiber affinity filter membrane for Hg2+ were determined. The heterogeneous hollow‐fiber affinity filter membrane was used for the adsorption of Hg2+ cations through the coordination of the mercapto group and Hg2+ cations, and the effects of the morphology and structure of the affinity membrane on the chelating properties were investigated. The chelating conditions, including the chelating resin grain size, pH value, concentration of the metallic ion solution, mobile phase conditions, and operating parameters, had significant effects on the chelating capacity of the hollow‐fiber affinity filter membrane. The results revealed that the greatest chelating capacity of the hollow‐fiber affinity filter membrane for Hg2+ was 1090 μg/cm2 of membrane under appropriate conditions, and the adsorption isotherms of Hg2+ could be described by the Langmuir isotherm. The dynamic chelating experiments indicated that the hollow‐fiber affinity membrane could be operated at a high feed flow rate and that large‐scale removal of Hg2+ could be realized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Lower critical solution temperature behavior of amphiphilic copolymers based on polyaspartamide derivatives
Authors: Bach Quang Vu , Moon Jong‐Rok , Lee Doo Sung , Kim Ji‐Heung
Published: September 2007

Novel copolymers consisting of poly(N‐isopropylaminoethyl‐co‐6‐hydroxyhexyl aspartamide) and poly (N‐isopropylaminoethyl‐co‐hexyl aspartamide) were prepared from polysuccinimide, which was the thermal polycondensation product of L‐aspartic acid, via a ring‐opening reaction with 6‐amino‐L‐hexanol (AH) or hexylamine (HA) and N‐isopropylethylenediamine at different ratios. The copolymers, containing 75–90 mol % of AH and 35–45 mol % of HA, produced thermoresponsive polymers through their lower critical solution temperatures (LCSTs) in aqueous solution. We could control the LCST could be controlled by modifying the hydrophobic–hydrophilic balance by changing the content of AH or HA. The pH dependencies of the LCST were opposite in these two different copolymer systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Determining the context of text using augmented latent semantic indexing
Authors: Rishel Tom , Perkins Louise A. , Yenduri Sumanth , Zand Farnaz
Published: September 2007

Latent semantic analysis has been used for several years to improve the performance of document library searches. We show that latent semantic analysis, augmented with a Part–of–Speech Tagger, may be an effective algorithm for classifying a textual document as well. Using Brille's Part–of–Speech Tagger, we truncate the singular value decomposition used in latent semantic analysis to reduce the size of the word–frequency matrix. This method is then tested on a toy problem, and has shown to increase search accuracy. We then relate these results to natural language processing and show that latent semantic analysis can be combined with context free grammars to infer semantic meaning from natural language. English is the natural language currently being used.
Developments and constraints in fermentative hydrogen production
Authors: Bartacek Jan , Zabranska Jana , Lens Piet N. L.
Published: September 2007

Fermentative hydrogen production is a novel aspect of anaerobic digestion. The main advantage of hydrogen is that it is a clean and renewable energy source/carrier with high specific heat of combustion and no contribution to the Greenhouse effect, and can be used in many industrial applications. This review discusses fermentative hydrogen production from various points of view. First, the theoretical principles of the biological processes taking place in hydrogen production, as well as the organisms responsible for this process, are described. Second, practical aspects of fermentative hydrogen production are overviewed. Suitable conditions for the hydrogen‐producers (pH and temperature), suitable substrates for hydrogen production and applicable reactor designs are discussed. Finally, the challenges faced by fermentative hydrogen production are discussed. Current research directions are listed together with the most important problems currently constraining full‐scale application. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd
Mung bean lipoxygenase in the production of a C6‐aldehyde. Natural green‐note flavor generation via biotransformation
Authors: Chow Yvonne , Liew Tze Huey , Keh Hui Hui , Ko Amy , Puah Sze Min , Nguyen Thi Bich Van , Zaman Nurulhida Binte Gul , Wu Jinchuan , Talukder Md Mahabubur Rahman , Choi Won Jae
Published: September 2007

Mung bean was investigated as a novel source of lipoxygenase in the natural production of the green‐note aroma compound hexanal. Lipoxygenase extracted from mung bean catalyzed the oxidative reaction of linoleic acid, after which the intermediate hydroperoxide compound was split via green bell pepper hydroperoxide lyase to produce hexanal. In comparison to soybean lipoxygenase, mung bean lipoxygenase was found to be a good substitute as it produced 15.4 mM (76% yield) hexanal while soybean gave 60% yield. The mung bean pH profile comprised a wide peak (optimum pH 6.5) representing lipoxygenase‐2 and lipoxygenase‐3 isozymes, whereas two narrower peaks representing lipoxygenase‐1 and lipoxygenase‐2/3 isozymes were observed for soybean (optimum pH 10). Extraction at pH 4.5 was preferred, at which specific lipoxygenase activity was also the highest.
The chakragati mouse: A mouse model for rapid in vivo screening of antipsychotic drug candidates
Authors: Dawe Gavin S. , Ratty Anil K.
Published: September 2007

The chakragati (ckr) mouse is a serendipitously discovered insertional transgenic mutant that exhibits circling and hyperactivity. Studies of social behavior, sensorimotor gating and ventricular anatomy suggest that the ckr mouse models aspects of schizophrenia. The underlying genetic and neurodevelopmental mechanisms remain to be elucidated but appear to result in a hemispheric asymmetry in striatal D2‐like dopamine receptors. The circling is inhibited by administration of antipsychotic drugs and so lends itself to in vivo prospective screening for novel molecules with antipsychotic‐like activity. Using the ckr mouse we have applied an in vivo first approach to screening for antipsychotic drug candidates. This offers the advantage of early indication of central nervous system bioavailability and potential toxicological concerns. Additionally, in vivo first screening in the ckr mouse is not biased by any particular neurotransmitter hypothesis of the disease, and so has the potential to identify compounds modifying the behavioral output by novel mechanisms of interaction with the underlying brain circuitry. Thus, in contrast to the classical strategy of hypothesis‐driven in vitro screening for drugs fitting a “receptor model” of the disease, the ckr mouse screen has greater potential to identify lead molecules for a new generation antipsychotics with novel mechanisms of action.
Comprehensive design of rotating shafts and a software for designing and selecting of rolling‐contact bearings
Authors: Taskesen Ahmet , Mendi Faruk , Kulekci Mustafa Kemal , Basak Hudayim
Published: September 2007

In this study a computer program was developed using Visual Basic and Visual LISP programming languages to comprehensively analyze the strength, deformation, vibration, manufacturing, and drawing of a rotating circular stepped shaft. These shafts have a variety of power transmitting mechanical elements (components), such as pairs of gears, and pulleys that are modeled in 3D. In addition, force and moment analyses of these elements running on the shafts were examined. Notch sensitivity and stress concentration factors given graphically were formulated using the finite difference method. Vibration analysis was also included to the software. Furthermore, to select the best rolling‐contact bearings, an expert system requiring the knowledge‐based technique was employed. The user is given the choice of shaft material and other parameters. After saving the data regarding calculated and designed shaft, these data are transferred to the graphical environment for detail drawing and CNC code generation of the shaft. A program, which is called shaft and gear design program, has been developed for this process. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 214–225, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20152
Effective page refresh policy
Authors: Gao Kai
Published: September 2007

Web pages are created or updated randomly. As for a search engine, keeping up with the evolving Web is necessary. But previous studies have shown the crawler's refresh ability is limited because it is not easy to detect the change instantly, especially when the resources are limited. This article concerns modeling on an effective Web page refresh policy and finding the refresh interval with minimum total waiting time. The major concern is how to model the change and which part should be updated more often. Toward this goal, the Poisson process is used to model the process. Further, the relevance is also used to adjust the process, and the probability on some sites is higher than others so these sites will be given more opportunities to be updated. It is essential when the bandwidth is not wide enough or the resource is limited. The experimental results validate the feasibility of the approach. On the basis of the above works, an educational search engine has been developed. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 240–247, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20155
Differences in Substrate Specificity of C(5)‐Substituted or C(5)‐Unsubstituted Pyrimidine Nucleotides by DNA Polymerases from Thermophilic Bacteria, Archaea, and Phages
Authors: Sawai Hiroaki , Nagashima Junichi , Kuwahara Msayasu , Kitagata Rina , Tamura Takehiro , Matsui Ikuo
Published: September 2007

The pyrimidine bases of RNA are uracil (U) and cytosine (C), while thymine (T) and C are used for DNA. The C(5) position of C and U is unsubstituted, whereas the C(5) of T is substituted with a Me group. Miller et al. hypothesized that various C(5)‐substituted uracil derivatives were formed during chemical evolution, and that C(5)‐substituted U derivatives may have played important roles in the transition from an ‘RNA world’ to a ‘DNA‐RNA‐protein world’. Hyperthermophilic bacteria and archaea are considered to be primitive organisms that are evolutionarily close to the universal ancestor of all life on earth. Thus, we examined the substrate specificity of several C(5)‐substituted or C(5)‐unsubstituted dUTP and dCTP analogs for several DNA polymerases from hyperthermophilic bacteria, hyperthermophilic archaea, and viruses during PCR or primer extension reaction. The substrate specificity of the C(5)‐substituted or C(5)‐unsubstituted pyrimidine nucleotides varied greatly depending on the type of DNA polymerase. The significance of this difference in substrate specificity in terms of the origin and evolution of the DNA replication system is discussed briefly.
ipso‐Substitution: A General Biochemical and Biodegradation Mechanism to Cleaveα‐Quaternary Alkylphenols and Bisphenol A
Authors: Gabriel Frédéric L. P. , Cyris Maike , Giger Walter , Kohler Hans‐Peter E.
Published: September 2007

Sphingobium xenophagumBayram is capable of metabolizing 4‐alkoxyphenols and endocrine disruptiveα‐quaternary 4‐nonylphenols by anipso‐substitution mechanism that involves ring hydroxylation at the site of the substituent. Here, we show that Bayram'sipso‐hydroxylating activity was able to transform also bisphenol A (=dimethyl‐4,4′‐methylenediphenol; BPA) and 4‐isopropylphenol. We identified six metabolites when resting cells of strain Bayram were incubated with BPA. They were unambiguously characterized by HPLC‐UV, HPLC/MS, and HPLC/MS/MS as hydroquinone, 2‐(4‐hydroxyphenyl)isopropanol, 4‐isopropenylphenol, 4‐isopropylphenol, 4‐hydroxy‐4‐isopropenylcyclohexa‐2,5‐dien‐1‐one, and 4‐hydroxy‐4‐isopropylcyclohexa‐2,5‐dien‐1‐one. In experiments with 4‐isopropylphenol as a substrate, 4‐hydroxy‐4‐isopropylcyclohexa‐2,5‐dien‐1‐one, one of the metabolites from BPA, accumulated to a high degree. We could rationalize the formation of all metabolites by invokingipso‐hydroxylation andipso‐substitution mechanisms. On closer view, also classical bacterial metabolism of BPA can be well rationalized by anipso‐substitution mechanism, albeit withipso‐attack of an internal alkyl radical instead of an activated oxygen species. This highlights the important role ofipso‐substitution as a versatile degradative principle utilized by diverse organisms to degradeα‐quaternary 4‐nonylphenols, 4‐alkoxyphenols, and BPA.
Chemical and Biogeophysical Impact of Four‐Dimensional (4D) Seismic Exploration in Sub‐Saharan Africa, and Restoration of Dysfunctionalized Mangrove Forests in the Prospect Areas
Authors: Osuji Leo C. , Ayolagha G. , Obute G. C. , Ohabuike H. C.
Published: September 2007

Four‐dimensional (4D) seismic exploration, an improved geophysical technique for hydrocarbon‐data acquisition, was applied for the first time in the Nembe Creek prospect area of Nigeria. The affected soils were slightly alkalinein situwhen wet (pH 7.2), but extremely acidic when dry (pH 3.0). The organic carbon content (4.6–26.8%) and other physicochemical properties of soils and water (N, P, and heavy‐metal contents,etc.) were higher than the baseline values obtained in 2001 before seismic profiling. Most values also exceeded the baseline compliance standards of theDepartment of Petroleum Resources(DPR), theWorld Health Organization(WHO), and theFederal Environmental Protection Agency(FEPA). Rehabilitation of the affected areas was achieved by stabilizing the mangrove floor by liming and appropriate application of nutrients, followed by replanting the cut seismic lines over a distance of 1,372 km with different mangrove species, including juvenileRhizophora racemosa, R. mangle, andAvicenniaspecies, which were transferred from nursery points. Quicker post‐operational intervention is recommended for future 4D surveys, because the time lag between the end of seismic activity and post‐impact investigation is critical in determining the relationship between activity and impact: the longer the intervening period, the more mooted the interaction.
Diastereoselective Synthesis of Aminobacteriohopanetetrol, a Biomarker for Methanotrophic Bacteria: Confirmation of the Absolute Configuration
Authors: Pan Weidong , Zhang Yongmin , Liang Guangyi , Rohmer Michel , Sinaÿ Pierre , Vincent Stéphane P.
Published: September 2007

A short and convenient strategy was developed for the first stereoselective chemical synthesis of aminobacteriohopanetetrol (=(1R,2R,3S,4S)‐5‐amino‐1‐[(22R)‐hopan‐30‐yl]pentane‐1,2,3,4‐tetrol; 1), a typical biomarker for methanotrophic bacteria. Comparison of the NMR spectra of the synthetic and natural (peracetylated) product enabled us to unambiguously corroborate the absolute configuration of the functionalized pentyl side chain of 1.
Ionic Liquids for the Production of Insecticidal and Microbicidal Extracts of the Fungus Cantharellus cibarius
Authors: Cieniecka‐Rosłonkiewicz Anna , Sas Agnieszka , Przybysz Elżbieta , Morytz Bolesław , Syguda Anna , Pernak Juliusz
Published: September 2007

Different ionic liquids were used as solvents for the effective extraction of the active metabolites of the fruit bodies of C. cibarius. The type of ionic liquid was found to play a significant role in this process. We found that the protic ionic liquid 1‐[(nonyloxy)methyl]‐1H‐imidazol‐3‐ium salicylate (6) is a most‐efficient extracting agent, being superior to classical solvents such as AcOEt or hexane. The obtained extracts generally revealed high insecticidal activities against both house fly and cockroach, with similar potencies as the standard pesticides bromfenvinphos or alphacypermethrin, as well as significant activities against bacteria, yeast, and moulds. Notably, the cidal activities against plant‐pathogenic bacteria were stronger than against human bacterial strains.
Zu Struktur und dynamischem Verhalten zweier Bis[lithio(trimethylsilyl)amino]silane
Authors: Veith Michael , Zimmer Michael , Kosse Peer
Published: September 2007

Structures and Dynamical Behaviour of two Bis[lithio(trimethylsilyl)amino]silanes

Herrn Prof. Reinhard Schmutzler zum 60. Geburtstag gewidmet.

NMR‐spectroscopic studies on solutions as well as X‐ray structural investigations of the solids reveal that both Me2Si[N(Li)SiMe3]2 (1) and(Me3Si)2N‐SiH[Me3SiN(Li)]2 (2) are dimeric molecular compounds in both phases. Moreover, in spite of their different reactivity and constitution, the Li, N, and Si atoms of both dimers from similar “basketshaped” molecular cages in the solid state. 1H‐, 6/7Li‐, and 13C‐NMR spectra in toluene show temperature dependence which is ascribed to intramolecular bond fluctuations within the molecular cages causing an equilibration of the two enantiomers of both compounds which cocrystallize in the solid state. The different activation energies for the motions of 1 and 2 which are deduced by inspection of the spectra, can be explained by participation of the hydride hydrogen in the intramolecular process in 2.
Synthese und Antitumoraktivität neuer Porphyrin‐Platin(II)‐Komplexe mit an den Porphyrin‐Seitenketten gebundenem cytostatischen Platin‐Rest
Authors: Brunner Henri , Maiterth Friedrich , Treittinger Barbara
Published: September 2007

Synthesis and Antitumor Activity of New Porphyrin‐Platinum(II) Complexes with the Cytostatic Platinum Fragment Attached to the Porphyrin Side Chains

Fifteen ligands of the porphyrin type, all derived from natural porphyrins, and their platinum(II) complexes, in which the Pt fragment is attached to the porphyrin side chains, were synthesized and characterized. Two different kinds of ligands were prepared: eight compounds with propionic acid substituents in the positions 6 and 7 of the porphyrin skeleton and seven ligands with 3‐aminopropyl side chains in the same positions. The ligands were transformed into eight diammine(dicarboxylato)platinum(II) complexes and into seven diaminedichloroplatinum(II) complexes. One of the water‐insoluble dichloroplatinum(II) compounds was converted into a water‐soluble complex by replacement of the chloride ligands by the lactate anion. The antitumor activity of the complexes was tested in vitro towards the MDA‐MB 231 mammary carcinoma cell line, and in vivo towards the P 388 leukemia of the mouse, the hormone‐independent MXT mammary carcinoma of the mouse and the Sarcoma 180 of the mouse. The best results in antitumor activity were obtained with diammine(dicarboxylato)platinum(II) complexes.
[(SeCl)2][FeCl4]: Synthesis, Quantumchemical Calculations, Vibrational Data and Single‐Crystal X‐ray Structure
Authors: Broschag Matthias , Klapätke Thomas M. , Schulz Axel , White Peter S.
Published: September 2007

The tetrachloroferrate salt of the [(SeCl)2N]+ cation, [(SeCl)2N][FeCl4] (1), has been prepared and structurally characterized. The [(SeCl)2N]+ cation exists in a C2v “u”‐ shaped geometry with the following structural parameters: d(Se‐Cl) = 2.16 Å, d(SeN) = 1.70 Å,· (ClSeN) = 108° and· (SeNSe) = 147°. The harmonic vibrational frequencies for two isomers (“u” and “s” isomer) have been computed by ab initio methods and are compared with the experimental IR and Raman spectra.
Donor‐Acceptor Spiro‐Compounds — Syntheses, Structures, and Electronic Properties
Authors: Gleiter Rolf , Hoffmann Herbert , Irngartinger Hermann , Nixdorf Matthias
Published: September 2007

The six donor‐acceptor spiro compounds spiro[1,3‐dioxolane‐2,2′‐indan]‐1′,3′‐dione (8), spiro[indan‐2,2′‐[1,3]oxathiolane]‐1,3‐dione (9), spiro[1,3‐dithiolane‐2,2′‐indan]‐1′,3′‐dione (10), spiro[1,3‐benzodioxole‐2,2′‐indan]‐1′,3′‐dione (11), 5‐methylspiro[1,3‐benzodithiole‐2,2′‐indan]‐1′,3′‐dione (12), and spiro[indan‐2,2′‐naphtho[2,3‐d]‐1,3‐dioxole]‐1,3‐dione (13) have been prepared. Their He (I) photoelectron spectra and their UV/Vis spectra have been investigated. A comparison between the first PE bands of the spiro compounds and the corresponding fragments indicates only a very weak interaction between both parts. The UV/Vis spectra of11‐13show a moderate long‐wavelength shift of the first band as compared to 1,3‐indandione. This band is assigned to a transition from the HOMO(π), localized at the donor fragment, to the LUMO(π*) of the acceptor moiety (charge transfer). X‐ray investigations of8‐10and13show no interaction between the two perpendicularly arranged moieties.
Stereoselective Synthesis of Exocyclic Allylsilanes by Intramolecular Reductive Heck Cyclisation of Propargylsilanes
Authors: Tietze Lutz F. , Schimpf Ralph
Published: September 2007

The stereoselective palladium‐catalysed synthesis of the heterocycles 13‐15 with a (Z)‐exocyclic allylsilane moiety is described. Alkylation of the secondary amides 5a, 5b, 9a, and 9b and the phenol 11 containing an iodoaryl moiety with the propargyl iodide 6 leads to the propargylsilanes 7a, 7b, 10a, 10b, and 12, which are allowed to react with a catalyst system of Pd(OAc)2/PPh3/NPr4Br and sodium formate as a hydride source. The (Z) configuration of the cyclisation products is confirmed by NOESY spectra and a single‐crystal X‐ray structure of 13b.
Inter‐ and Intramolecular Hetero Diels‐Alder Reactions, 49[1] Kinetics and Selectivity of the Intramolecular Hetero Diels‐Alder Reaction of 1‐Oxa‐1,3‐butadienes using a Benzylidenebarbituric Acid Derivative Effect of Pressure, Temperature, and Solvent
Authors: Buback Michael , Gerke Kerstin , Ott Christian , Tietze Lutz F.
Published: September 2007

The intramolecular hetero Diels‐Alder reaction of the benzy‐lidenebarbituric acid derivative 1 to give the ortho and meta products 2 and 3 is studied under high pressure up to 6 kbar in various solvents. The kinetics is measured by on‐line FT‐IR spectroscopy up to 3 kbar. The cycloaddition shows a pressure‐dependent increase in regioselectivity in favour of the ortho adduct 2. The activation volumes, ΔV, are determined to be ‐(33.1· 1.2) and ‐(34.2· 1.5) cm3· mol−1 for the reactions in dichloromethane and tetrahydrofuran at 100°C, respectively. For the cycloaddition in toluene and acetonitrile the activation volumes are found to be ‐(13.4· 1.5) and ‐(17.0· 4.1) cm3· mol−1, respectively. Contrary to the large solvent effect on the activation volume, only a minor effect on the activation volume differences, ΔΔV, is observed. Measurement of the molar volumes of 1 and the cycloadducts 2 and 3 show a strong solvent dependency.
Photoresponsive Piperazine Macrocycles
Authors: Huuskonen Juhani , Schulz Jürgen , Kolehmainen Erkki , Rissanen Kari
Published: September 2007

The photoresponsive macrocyclic phanes 3, 7a, 7b, 10 were prepared. The (E) and (Z) isomers of 7b could be separated from each other by column chromatography. The X‐ray structure of the 31‐membered cycle (E)‐7b and the 54‐membered cycle (E,E)‐10 shows a tendency toward self‐assembly to a dimeric structure (7b) and a tubular structure (10) in the crystalline state. Additionally, both structures demonstrate inclusion of solvent molecules into the cavity (diameter 5 Å, 7b) and tube (diameter 11 Å, 10) respectively. A variable‐temperature 1H‐NMR study of 7b showed that the piperazine ring inversion is restricted at lower temperatures.
Enantioselektive Katalysen, 90[1]. Optisch aktive Stickstoffliganden mit Dendrimer‐Struktur
Authors: Brunner Henri , Altmann Stefan
Published: September 2007

Enantioselective Catalysis, 90[1]. ‐ Optically Active Nitrogen Ligands with Dendrimeric Structure

2‐Pyridinecarboxaldehyde (1) reacts with (1S,2S)‐2‐amino‐1‐phenyl‐1,3‐propanediol (2) to afford a mixture of the Schiff base 3 and the oxazolidines 3a/3a′, 3b/3b′, which was reduced with NaBH4 to yield the optically active 2‐pyridinylmethylamino alcohol 4. Similarly, 8 was synthesized from 2,6‐pyridinedicarboxaldehyde (7). By acylation of the hydroxy and amino groups, compound 4 was expanded to the corresponding ester amides 5 and 6. Boc and cbz protection of the amino group of 2 produced 10 and 19, respectively. The hydroxy groups of 10 were esterified with 4‐(chloromethyl)‐benzoyl chloride (11) and 3,5‐bis(chloromethyl)benzoyl chloride (12) to give 13 and 14. Compound 19 was converted to the diester 21 by treatment with 3,5‐dimethylbenzoyl chloride (20). Substitution of the chloro substituent in 13 and 14 by (1R,2S)‐ephedrine and (1S,2S)‐2‐(benzylamino)‐1‐phenyl‐1,3‐propanediol, respectively, lead to the tertiary amines 15a‐17a. After removal of the N‐protection, the primary amino groups of 17b‐22 were treated with the aldehydes 1, 7, 27, and 35 to give the corresponding aldimine chelate ligands 23‐26, 28‐34, and 36. Starting with L‐N‐boc‐aspartic acid (37) the tripeptide 39 was formed with two equivalents of L‐aspartic acid dimethyl ester hydrochloride (38). After removal of the boc group followed by condensation with salicylaldehyde, imine 40 was generated. (S)‐2‐amino‐1,1,4,4‐tetraphenyl‐1,4‐butanediol (41), derived from L‐aspartic acid, was treated with the aldehydes 27 and 35. The resulting products 42 and 43 in solution formed mixtures of the diastereomeric oxazolidines 42a and 43a as well as the oxazinanes 42b and 43b. The ligands have been tested in the CuI‐catalyzed cyclopropanation of styrene with ethyl diazoacetate.
Swern Oxidation of Alkenyl‐Substituted 2‐(tert‐Butyldimethylsiloxy)‐1‐(hydroxymethyl)cyclopropanes: A Novel and Flexibel Route to Functionalized 2,5‐Dihydrooxepines
Authors: Hofmann Bernhard , Reißig Hans‐Ulrich
Published: September 2007

Swern oxidation of 2‐alkenyl‐substituted 2‐siloxy‐1‐(hydroxymethyl)cyclopropanes 7 and 11 ‐ 16 provided 2,5‐dihydrooxepines 8 and 17‐21, respectively. The corresponding cyclopropanecarboxaldehydes are highly plausible intermediates in this transformation, which give the seven‐membered heterocycles by a concerted [3,3]‐sigmatropic rearrangement. Some of the 2,5‐dihydrooxepines easily undergo ring contraction to 2‐vinyl‐2,3‐dihydrofurans. Direct formation of these furan derivatives was observed when (hydroxymethyl)‐ cyclopropanes 25‐28 were oxidized. In these cases a step‐wise rearrangement of the 2‐siloxycyclopropanecarboxalde‐hydes involving 1,3‐zwitterions as intermediates is proposed. Our results are compared with the few literature examples and reveal interesting substituent effects. Thus, the donor‐acceptor substitution shifts the equilibrium between the 2‐vinylcyclopropanecarboxaldehydes and the 2,5‐dihydrooxepines to the side of the seven‐membered heterocycles. Further mechanistic details are discussed.
A Steroid‐Substituted Group‐4 Bent Metallocene System: Synthesis, Structural Features and Its Use in Catalytic Propene Polymerization
Authors: Erker Gerhard , Mollenkopf Christoph , Grehl Matthias , Schönecker Bruno
Published: September 2007

3‐Methoxyestra‐1,3,5(10)‐trien‐16‐one (6) was converted to the corresponding fulvene (7). Methyllithium was added and the resulting (16α‐methylestratrienyl)cyclopentadiene 8 separated by chromatography. Deprotonation gave the (16α‐methylestratrienyl‐C5H4)Li reagent 9 that was added to 0.5 molar equivalents of ZrCl4(THF)2 to yield bis[‐(3‐methoxy‐16α‐methylestra‐1,3,5(10)‐trien‐16ß‐yl)cyclopentadienyl]‐zirconium dichloride (10, 45%). Complex 10 was activated by treatment with an excess of methylalumoxane. The resulting homogeneous Ziegler‐type catalyst was employed for stereo‐selective propene polymerization. In the temperature range of ‐50 to ‐10°C partly isotactic polypropylene was obtained. A detailed analysis has revealed that stereocontrol is effected by a combination of enantiomorphic site and chain‐end control. Compounds 7 and 10 were characterized by X‐ray diffraction.
Synthese von Ara‐Tubercidin und seiner 5′‐Phosphate über Phasentransfer‐Glycosylierung von 4‐Amino‐2‐methylthio‐7H‐pyrrolo[2,3‐d]pyrimidin
Authors: Seela Frank , Tran‐Thi Quynh‐Hoa , Winkeler Heinz‐Dieter
Published: September 2007

Phasentransfer‐Glycosylierung von 4‐Amino‐2‐methylthio‐7H‐pyrrolo[2,3‐d]pyrimidin (3a) mit 2,3,5‐Tri‐O‐benzyl‐1‐brom‐D‐arabinofuranose führt in 83% Ausbeute zu den anomeren Nucleosid‐Derivaten 4a/5a, die chromatographisch getrennt werden und deren Anomerenverhältnis (β:α) mit 4.9:1 gefunden wird. Raney‐Nickel entfernt die Methylthioreste und nach hydrierender Abspaltung der Benzylschutzgruppen erhält man 4‐Amino‐7‐(β‐D‐arabinofuranosyl)pyrrolo[2,3‐d]pyrimidin (1a) und sein α‐Anomeres (6). Aus dem β‐Anomeren 1a (Ara‐Tubercidin) wird mit POCL3 das 5′‐Monophosphat 1b erhalten, das im Gegensatz zu Ara Ara‐AMP (2b) von AMP‐Desaminase nicht desaminiert wird. 1b wird durch Kondensation mit Mono[trioctylammonium]orthophosphat bzw. Di[tributylammonium]pyrophosphat und 1,1′‐Carbonyldiimidazol in das 5′‐Diphosphat 1c und das 5′‐Triphosphat 1d übergeführt.
Nucleosid‐Synthesen, XXIV1) Nucleoside von 3,6‐Dihydro‐2H‐1,2,6‐thiadiazin‐1,1‐dioxiden
Authors: Su Tsann Long , Bennua Bärbel , Vorbrüggen Helmut , Lindner Hans Jörg
Published: September 2007

Die Synthese von neuartigen Nucleosiden von 3,6‐Dihydro‐2H‐1,2,6‐thiadiazin‐1,1‐dioxiden wird beschrieben. Anhand der Röntgenstrukturanalyse der Verbindung 16 wird die Stereochemie dieses neuen Nucleosid ‐Typs diskutiert.
Nucleoside syntheses, XXV1) A new simplified nucleoside synthesis
Authors: Vorbrüggen Helmut , Bennua Bärbel
Published: September 2007

The several steps of the Friedel‐Crafts catalyzed silyl‐Hilbert‐Johnson nucleoside synthesis ‐ silylation of the heterocyclic base, silylation of the perfluorosulfonic acids or its salts (if SnCl4 is not used as catalyst) and finally the nucleoside synthesis itself ‐ can be combined to a simple one‐step/one‐pot reaction which generally affords nucleosides in high yields.
Photosensibilisierte Addition von Citraconsäureanhydrid an 3,3‐Dimethyl‐1‐butin
Authors: Mayer Wolfram , Wendisch Detlef , Born Liborius , Hartmann Willy
Published: September 2007

Die photosensibilisierte Addition von Citraconsäureanhydrid (CA) and 3,3‐Dimethyl‐1‐butin in Aceton führt zu den isomeren Cyclobutenen 1 und 2 sowie zum 6,6‐Dimethyl‐2‐cis, 4‐trans‐heptadien‐2,3‐dicarbonsäure‐anhydrid. (3) Unter den Reaktionsbedingungen photodimerisiert 3 zum thermolabilen Divinylcyclobutan‐Derivat 5, dessen Konstitution aus der Röntgenstrukturanalyse folgt. Für die Bildung der Produkte 1–3 wird ein Reaktionsverlauf mit intermediären Alkyl‐Vinyl‐1,4‐Diradikalen diskutiert. Gemeinsame Zwischenstufe für 2 und 3 ist danach das Diradikal 7. Der Mechanismus der intramolekularen Disproportionierung von 7 wird durch Isotopenmarkierung ([3‐D]CA) aufgeklärt.
Synthese und Ligandeneigenschaften von 2‐Methyl‐1‐trimethyl‐silyl‐ und 2‐Methyl‐Δ3‐1,2‐azaborolin
Authors: Schulze Joachim , Boese Roland , Schmid Günter
Published: September 2007

2‐Methyl‐1‐trimethylsilyl‐Δ3‐1,2‐azaborolin (1), dargestellt aus LiCHCHCH2‐N[Si(CH3)3]Li und CH3BBr2 kann durch Abspaltung der Trimethylsilylgruppe mittels etherischer HCl in 2‐Methyl‐Δ3‐1,2‐azaborolin (2) übergeführt werden. 2 dimerisiert bei Raumtemperatur über N→B‐Koordination zu 2a. 1 und 2 reagieren mit Fe(CO)5 zu den Azaborolinylkomplexen Di‐μ‐carbonyl‐bis[carbonyl](2‐methyl‐1‐trimethylsilyl‐η‐1,2‐azaborolinyl) eisen (FeFe) (3) bzw. Di‐μ‐carbonyl‐bis[carbonyl(2‐methyl‐1‐trimethylsilyl‐Δ‐1,2‐azaborolinyl)eisen](FeFe) (4). Die IR‐, 1H‐NMR‐, 11B‐NMR‐ und Massenspektren der Verbindungen werden diskutiert.
Tricarbonyleisen‐Komplexe mit zwei funktionellen Arsenliganden
Authors: Börner Mechael , Vahrenkamp Heinrich
Published: September 2007

Zur Bildung der reaktiven Komplexe (CO)3Fe(AsMe2X)2 (1) mit X = NMe2 (1a) und SiMe3 (1b) eignete sich amd besten die Bestrahlung der Verbindungen (CO)4FeAsMe2X in Gegenwart des entsprechenden Liganden. 1a und HCl ergaben den instabilen Komplex 1c mit X = Cl; aus 1b und CH3OH, Me2PCI bzw. Me2AsCl entstanden die reaktiven Vertreter 1d (X = H), 1e (X = PMe2) bzw. 1f (X = AsMe2). Mehrkernkomplexsynthesen waren nicht von 1c,e und f aus möglich, doch über 1f konnten zwei Organometall‐Kakodyl‐Sechsringe 5 und über 1d ein kettenförmiger Dreikernkomplex 4a erhalten werden. Beim Versuch der Synthese von 1c, aus (Benzylidenaceton)tricarbonyleisen (6) und Me2AsCl wurden statt dessen zwei neue arsenverbrückte Carbonyleisen‐Zweikernkomplexe (7) gebildet. 6 reagierte mit Organometall‐dimetylarseninden in erster Stufe zu arsenverbrückten Zweikernkomplexen (9, 10 bzw. 11) mit und ohne Metall‐Metall‐Bindung. Daraus konnten in zweiter Stufe kettenförmige arsenverbrückte Dreikernkomplexe 4 bzw. 12 entstehen.
Arsiniden‐Komplexe: Synthesen, Substitutionsreaktionen, Spektren und Strukturen von X As[(CO)5Cr]2 und XAs[η5‐C5H5(CO)2Mn]2 (X = Aryl, Halogen, RE mit E = O, S, Se)
Authors: Seyerl Jochim Von , Sigwarth Beate , Schmid Hans‐Georg , Mohr Gerhard , Frank Albin , Marsili Mario , Huttner Gottfried
Published: September 2007

Die Chlorfunktion im Arsiniden‐Komplex ClAs[(CO)5Cr]2 (1a) kann durch Umsetzung mit Nucleophilen wie Halogenid‐Ionen, Alkoholen oder S‐ und Se‐Homologen gegen andere Halogene sowie RO‐, RS‐ und RSe‐Gruppen ausgetauscht werden. Substitution durch C6H6 gelingt mit BiPh3 als Phenylierungsmittel, Chlor‐Brom‐Austausch erfolgt bei der Reaktion von 1a mit BBr3. ClAs[η5‐C5H5(CO)2Mn]2 (2a) reagiert ähnlich. Für die Synthese von Phenylarsiniden‐Komplexen stehen neben der Halogensubstitution eine Reihe weiterer Synthesewege zur Verfügung. Die Elektronenspektren der intensiv farbigen Arsiniden‐Komplexe werden unter Berücksichtigung der Elektronenspektren von Phosphiniden‐ und Stibiniden‐Komplexen diskutiert. ‐ Die Strukturchemie von Arsiniden‐komplexen, die trigonal‐planar koordiniertes Arsen(+ 1) enthalten, wird anhand von röntgenstrukturanalytischen Ergebnissen an 1a und 2a sowie PhAs[(CO)5Cr]2 (1d) und PhAs[η5‐C5H5(CO)2Mn]2 (2c) besprochen.
Reaktionen des Chlorarsiniden‐Komplexes ClAs[Cr(CO)5]2 mit zweizähnigen Chelatliganden
Authors: Seyerl Jachim Von , Sigwarth Beate , Huttner Gottfried
Published: September 2007

Der Chlorarsiniden‐Komplex ClAs[Cr(CO)5]2 (1) reagiert mit OH‐funktionellen Chelatliganden HO B wie 2,4‐Pentandion, 1,3‐Diphenyl‐1,3‐Diphenyl‐1,3‐propandion, Tropolon oder 8‐Hydroxychinolin unter Chlor‐Substitution und Bildung stabiler Arsen (+1)‐Chelatkomplexe B OAs[Cr(CO)5]2 (2a–d). Eine Röntgenstrukturanalyse des Acetylacton‐Derivates 2a belegt die Konstitution der Chelatkomplexe.
Eigenschaften und Struktur von μ‐Tetrathioquadratatobis[methyldiphenylphosphan)gold(I)]
Authors: Jones Peter G. , Sheldrick George M. , Fügner Armin , Götzfried Franz , Beck Wolfgang
Published: September 2007

Die Struktur der Titelverbindung Ph2MePAuC4S4AuPMePh2(1), die aus Ph2MePAuCl und dem Anion der Tetrathioquadratsäure zugänglich ist, wurde bestimmt (monoklin, Raumgruppe C2/c, Z = 4). Tetrathioquadratat tritt als Brücke zwischen den Goldatomen auf; die beiden Chelatringe der Adjuvans‐Arthritis der Ratte.
Cyclische Doppel‐Ylide und ihre korrespondierenden Diphosphonium‐triple‐ylid‐Anionen: Synthese, Struktur und komplexchemisches Verhalten
Authors: Schmidbaur Hubert , Costa Thomas , Milewski‐Mahrla Beatrix
Published: September 2007

Aus Bis(dimethylphosphino)‐ und (diphenylphoshino)methan (1a, b) und 1,2‐bis(brommethyl)benzol werden die cyclischen Diquartärsalze 2a, b erhalten, über die mit Ylidbasen oder KH die ylidischen Halbsalze 4a, b und die Doppel‐Ylide 3a, b zugänglich sind. Diese Ylide besitzen nach spektroskopischen Daten nicht die Carbodiphosphoranstruktur, sondern sind unsymmetrische, konjugierte Doppel‐Ylide mit fluktuierendem Charakter. Die Hydrolyse führt zum offenkettigen ylidischen Phosphanoxid 5, die BH3‐Addition zum Monoaddukt 6. Mit Zn(CH3)2 werden aber zweikernige 1:1‐Komplexe gebildet (7a, b). die sich von der Carbodiphosphoran‐Form ableiten. ‐ Die Reaktion von 3b mit LiR, NaNH2, KH und metallischem Barium (in flüssigem Ammoniak) liefert die (Erd) Alkalisalze des zugehörigen Diphosphonium‐triple‐ylid‐Anions (8–8). Mit Cd(CH3)2 entsteht aus 3b unter Methanentwicklung der Cadmiumkomplex 12, dessen Kristallstruktur röntgenographisch bestimmt wurde.