bluuebunny/crossref_metadata_2025 huggingface dataset:
Reputation‐based semantic service discovery
Authors: Shaikh Ali Ali , Majithia Shalil , Rana Omer F. , Walker David W.
Published: November 2005

An important component of Semantic Grid services is the support for dynamic service discovery. Dynamic service discovery requires the provision of rich and flexible metadata that is not supported by current registry services such as UDDI. We present a framework to facilitate reputation‐based service selection in Semantic Grids. Our framework has two key features that distinguish it from other work in this area. First, we propose a dynamic, adaptive, and highly fault‐tolerant reputation‐aware service discovery algorithm. Second, we present a service‐oriented distributed reputation assessment algorithm. In this paper, we describe the main components of our framework and report on our experience of developing the prototype. Copyright © 2005 John Wiley & Sons, Ltd.
An approach to the quantitative evaluation of Grid services
Authors: Andreozzi Sergio , Ciancarini Paolo , Montesi Danilo , Moretti Rocco
Published: November 2005

In the context of the progressive incarnation of Grid systems in terms of a Service Oriented Architecture, it is essential to improve the automatic evaluation and selection of Grid services. Current mechanisms for service evaluation lack expressiveness as regards the representation of service requesters' expectations. In this paper, we present a model for the quantitative expression of service attributes, for the association of the possible values of these attributes with the requester satisfaction and for the aggregation of a set of satisfactions in an overall score by means of different aggregation logics. The proposed approach enriches the expressiveness of the mechanisms for the evaluation of Grid services. Copyright © 2005 John Wiley & Sons, Ltd.
Supporting resource reservation and allocation for unaware applications in Grid systems
Authors: Di Stefano Antonella , Fargetta Marco , Pappalardo Giuseppe , Tramontana Emiliano
Published: November 2005

The dynamics of resource request rates in a Grid system can be wide ranging, to the point that request peaks for a single resource can be difficult to handle and end up greatly increasing the response time. Once a request has been submitted by a client, this has to cope with the potential overload arising. However, it is impractical to cure overload once it takes place by negotiating a different service or finding an equivalent resource, since the client would then bear the delay due to negotiation and re‐submission. Instead, in order to effectively exploit Grid resources, it is crucial that applications perform reservation of resources before using them. Reservation allows a management system to consider application needs in advance and take suitable action to improve resource availability. In particular, this enables additional resources to be secured beforehand in the background when appropriate to avoid a potential overload, rather than paying the involved costs when overload arises. This paper proposes a software architecture that integrates applications with Globus services to conveniently handle resource reservation and allocation. Within the architecture, the computational reflection technology transparently connects applications with components that take care of advance reservation, as they dynamically sense the applications' resource needs. This dynamic information augments static knowledge gathered offline from static program code analysis. Copyright © 2005 John Wiley & Sons, Ltd.
A component‐based middleware framework for configurable and reconfigurable Grid computing
Authors: Coulson Geoff , Grace Paul , Blair Gordon , Cai Wei , Cooper Chris , Duce David , Mathy Laurent , Yeung Wai Kit , Porter Barry , Sagar Musbah , Li Wei
Published: November 2005

Significant progress has been made in the design and development of Grid middleware which, in its present form, is founded on Web services technologies. However, we argue that present‐day Grid middleware is severely limited in supporting projected next‐generation applications which will involve pervasive and heterogeneous networked infrastructures, and advanced services such as collaborative distributed visualization. In this paper we discuss a new Grid middleware framework that features (i) support for advanced network services based on the novel concept of pluggable overlay networks, (ii) an architectural framework for constructing bespoke Grid middleware platforms in terms of ‘middleware domains’ such as extensible interaction types and resource discovery. We believe that such features will become increasingly essential with the emergence of next‐generation e‐Science applications. Copyright © 2005 John Wiley & Sons, Ltd.
Absolute Configuration of C76 from Optical Rotatory Dispersion
Authors: Polavarapu Prasad L. , He Jiangtao , Crassous Jeanne , Ruud Kenneth
Published: November 2005

The absolute configuration of C76 has been determined as (+)589‐(fC)‐C76 , for the first time, by comparing the experimental and predicted optical rotatory dispersion (ORD) patterns. The experimental ORD pattern was derived from the experimental electronic circular dichroism (ECD) spectrum using the Kramers–Kronig (KK) transform. The theoretical ORD spectra were calculated in the resonant region using linear response theory, and also using the KK transform of the theoretical ECD spectrum, at different theoretical levels, namely BHLYP/6‐31G*, B3LYP/6‐31G*, BLYP/6‐31G*, and HF/6‐31G*. Good agreement noted between experimental and predicted spectra allows for an unambiguous determination of the absolute configuration.
Radiolysis of Confined Water: Hydrogen Production at a High Dose Rate
Authors: Le Caër Sophie , Rotureau Patricia , Brunet Francine , Charpentier Thibault , Blain Guillaume , Renault Jean Philippe , Mialocq Jean‐Claude
Published: November 2005

The production of molecular hydrogen in the radiolysis of dried or hydrated nanoporous controlled‐pore glasses (CPG) has been carefully studied using 10 MeV electron irraditation at high dose rate. In all cases, the H2 yield increases when the pore size decreases. Moreover, the yields measured in dried materials are two orders of magnitude smaller than those obtained in hydrated glasses. This proves that the part of the H2 coming from the surface of the material is negligible in the hydrated case. Thus, the measured yields correspond to those of nanoconfined water. Moreover, these yields are not modified by the presence of potassium bromide, which is a hydroxyl radical scavenger. This experimental observation shows that the back reaction between H2 and HO. does not take place in such confined environments. These porous materials have been characterized before and after irradiation by means of Fourier‐transform infrared (FT‐IR) spectroscopy, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) techniques, which helps to understand the elementary processes taking place in this type of environment, especially the protective effect of water on the surface in the case of hydrated glasses.
Cover Picture: Scanning Tunneling Microscopy and Spectroscopy of Donor–Acceptor–Donor Triads at the Liquid/Solid Interface (ChemPhysChem 11/2005)
Authors: Uji‐i Hiroshi , Miura Atsushi , Schenning Albert , Meijer E. W. , Chen Zhijian , Würthner Frank , De Schryver Frans C. , Van der Auweraer Mark , De Feyter Steven
Published: November 2005

The cover picture shows a submolecularly resolved scanning tunneling microscopy current image and scanning tunneling spectroscopy curves of a mixture of two physisorbed donor (oligo‐p‐phenylenevinylene)–acceptor (perylene diimide)–donor (oligo‐p‐phenylenevinylene) triads at the liquid–solid interface. By means of bias‐dependent imaging and scanning tunneling spectroscopy, it is not only possible to distinguish both triads, which differ in the nature of the substituents in the bay area of the central perylene diimide acceptor, but also to identify the donor and acceptor moieties within a given triad. Find out more in the Article by Uji‐i et al. on page 2389.
Sex differences in juvenile rhesus macaque (Macaca mulatta) agonistic screams: Life history differences and effects of prenatal androgens
Authors: Tomaszycki Michelle L. , Gouzoules Harold , Wallen Kim
Published: November 2005

This study investigated sex differences in juvenile rhesus macaque (Macaca mulatta) vocal behavior during agonistic contexts, and the effects of prenatal androgens on these differences. A total of 59 subjects (5–8 per treatment group) received exogenous androgen (testosterone enanthate), an anti‐androgen (flutamide) or vehicle injections (DMSO) for 30 or 35 days during the second (early) or third (late) trimester of pregnancy. An additional 19 unmanipulated controls were included in the analysis. Screams by juvenile males and females between the ages of 1 and 3 years were compared to the screams of adult female exemplars using a discriminant function analysis. Juvenile females produced more adult‐female like screams than did juvenile males. Females exposed to androgen treatment late in gestation produced a more masculine pattern of screams. Flutamide treatment in males either early or late in gestation did not significantly affect scream production. Flutamide treatments in females late in gestation, however, masculinized scream production. Androgen treatments administered late in gestation hyper‐masculinized male scream production. No sex differences in the contextual usage of screams emerged. These findings suggest that both life history differences and the early hormone environment contribute to sex differences in juvenile rhesus macaque vocal production. © 2005 Wiley Periodicals, Inc.Dev Psychobiol47: 318–327, 2005.
Characterization of two new zebrafish members of the hedgehog family: Atypical expression of a zebrafish indian hedgehog gene in skeletal elements of both endochondral and dermal origins
Authors: Avaron F. , Hoffman L. , Guay D. , Akimenko M.A.
Published: November 2005

We have characterized two new members of the Hedgehog (Hh) family in zebrafish, ihha and dhh, encoding for orthologues of the tetrapod Indian Hedgehog (Ihh) and Desert Hedgehog (Dhh) genes, respectively. Comparison of ihha and Type X collagen (col10a1) expression during skeletal development show that ihha transcripts are located in hypertrophic chondrocytes of cartilaginous elements of the craniofacial and fin endoskeleton. Surprisingly, col10a1 expression was also detected in cells forming intramembranous bones of the head and in flat cells surrounding cartilaginous structures. The expression of col10a1 in both endochondral and intramembranous bones reflects an atypical composition of the extracellular matrix of the zebrafish craniofacial skeleton. In addition, during fin ray regeneration, both ihha and col10a1 are detected in scleroblasts, osteoblast‐like cells secreting the matrix of the dermal bone fin ray. The presence of cartilage markers suggests that the dermal fin ray possesses an intermediate phenotype between cartilage and bone. Developmental Dynamics 235:478–489, 2006. © 2005 Wiley‐Liss, Inc.
Hot hearts in the Sonoran desert: The 11th Weinstein cardiovascular development conference in Tucson
Authors: Hardy Katharine M. , Mjaatvedt Corey H. , Antin Parker B.
Published: November 2005

The 11th Annual Weinstein Cardiovascular Development Conference was held May 19–22, 2005 at the Westward Look Resort and Conference Center in Tucson, Arizona. The Westward Look was the site of the 6th Weinstein Meeting in 1999, and this year, 330 basic research scientists and research clinicians returned to Tucson for 3 days of meetings, Mariachis, and margaritas. The meeting was hosted by the cardiovascular research group at the University of Arizona and offered flavors of the desert southwest that included record temperatures, the Skopopelli conference logo modified from the Kokopelli of Native American mythology (Fig. 1), and liberal use of a cattle prod to encourage speaker timeliness. Developmental Dynamics 235:170–175, 2006. © 2005 Wiley‐Liss, Inc.
Expression of chondrogenic potential of mouse trunk neural crest cells by FGF2 treatment
Authors: Ido Atsushi , Ito Kazuo
Published: November 2005

There is a significant difference between the developmental patterns of cranial and trunk neural crest cells in the amniote. Thus, whereas cranial neural crest cells generate bone and cartilage, trunk neural crest cells do not contribute to skeletal derivatives. We examined whether mouse trunk neural crest cells can undergo chondrogenesis to analyze how the difference between the developmental patterns of cranial and trunk neural crest cells arises. Our present data demonstrate that mouse trunk neural crest cells have chondrogenic potential and that fibroblast growth factor (FGF) 2 is an inducing factor for their chondrogenesis in vitro. FGF2 altered the expression patterns of Hox9 genes and Id2, a cranial neural crest cell marker. These results suggest that environmental cues may play essential roles in generating the difference between developmental patterns of cranial and trunk neural crest cells. Developmental Dynamics 235:361–367, 2006. © 2005 Wiley‐Liss, Inc.
Expression and functional analysis of Tgif during mouse midline development
Authors: Jin Jiu‐Zhen , Gu Shi , McKinney Patrick , Ding Jixiang
Published: November 2005

The Tgif gene encodes a homeodomain protein that functions as a transforming growth factor beta (TGF‐β) repressor by binding to Smad2. Mutations in the TGIF gene are associated with human holoprosencephaly, a common birth defect caused by the failure of anterior ventral midline formation. However, Smad2‐mediated TGF‐β signaling in the axial mesendoderm has been demonstrated to be essential for ventral midline formation, and loss of a Smad2 antagonist should in principle promote rather than inhibit ventral midline formation. This suggests a more complex mechanism for the function of TGIF in controlling ventral midline formation. To explore the role of TGIF in ventral forebrain formation and patterning, we investigated Tgif expression and function during mouse development by in situ hybridization and gene targeting. We found that Tgif is highly expressed in the anterior neural plate, consistent with the proposed neural differentiation model in which TGF‐β suppression is required for normal neural differentiation. This result suggests a possible role for Tgif in anterior neural differentiation and patterning. However, targeted disruption of the Tgif gene during mouse development does not cause any detectable defects in development and growth. Both histological examination and gene expression analysis showed that Tgif−/− embryos have a normal ventral specification in the central nervous system, including the forebrain region. One interpretation of these results is that the loss of TGIF function is compensated by other TGF‐β antagonists such as c‐Ski and SnoN during vertebrate anterior neural development. Developmental Dynamics 235:547–553, 2006. © 2005 Wiley‐Liss, Inc.
Construction method and analysis of radiation characteristics of an ultralarge array antenna for microwave power transmission
Authors: Sugawara Akira , Takano Tadashi , Hanayama Eiji , Kami Yoshio
Published: November 2005

When an ultralarge antenna for microwave power transmission is constructed, a promising realization method can be an array of subarray units made of small antennas or an array of aperture antennas. In this case, there are discontinuities of electromagnetic fields between the units or elements so that grating lobes may be generated. In this paper, a method is presented for construction of an array antenna with a diameter on the order of 1 km made of element apertures with a diameter on the order of 10 m. The radiation characteristics are discussed by an analysis. By using the element aperture gap, electric field distribution over each element aperture, and excitation intensity profile over the entire array as the parameters, variations of the radiation characteristics are studied. As a result, it is found effective as a method of suppression of the grating lobe to use the following approaches: (1) the electric field distribution of the element aperture and the aperture dimensions are appropriately selected, (2) the array antenna should have the most densely filled configuration with uniform distribution or $\cos^{2}$ distribution over each element aperture but with a Gaussian distribution over the entire array. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 59–68, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20245
A study of adaptive modulation technique in OFDM
Authors: Usui Tsutomu , Ishizu Fumio , Murakami Keishi
Published: November 2005

This paper presents the results of a study of the OFDM adaptive modulation technique. The adaptive modulation technique, which selects the modulation scheme according to the transmission conditions, is effective in improving system throughput. Then, it is important to study evaluation function under various propagation conditions. In this paper, we propose an adaptive modulation technique using the instantaneous DUR (desired signal to undesired signal ratio) per packet as the performance measure of the transmission path, in which the intersymbol interference (ISI) and intercarrier interference (ICI) power of delayed waves exceeding the guard interval are used under the assumption of convolution coding and soft‐decision Viterbi decoding. A DUR estimation method is also proposed. The effectiveness of the approach is confirmed by numerical simulation. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 36–45, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20254
An electrically invisible dipole loaded with a variable reactor and its applications for a reconfigurable antenna
Authors: Iigusa Kyouichi , Ohira Takashi , Komiyama Bokuji
Published: November 2005

This paper shows that the integral of the current flowing on a parasitic dipole can be made to vanish by supplying a reactance with an appropriate value. When a reactor is placed at the center of a half‐wave dipole with a thickness of 0.02 wavelength, the reactance value making the integral of the current vanish is about +450 Ω. The state in which the integral of the current is zero is not affected by other elements and minimizes the electrical influence on other elements. Hence, this state is considered electrically invisible. A reconfigurable (structurally variable) ESPAR antenna is proposed in which a variable reactance is placed on a parasitic dipole and the combination is adequately made electrically invisible. A method of calculation is proposed in which the admittance of the array configuration without a specific dipole element is obtained from the admittance in the presence of such an element by making it electrically invisible. Further, by this calculation method, the behavior of the admittance of an array with symmetrically placed elements is obtained. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 21–35, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20262
Performance evaluation of minimum S/N loss pulse compression filter with zero range sidelobe applied to phase‐coded waveforms
Authors: Shinonaga Mitsuyoshi , Yajima Shinichi , Nishimoto Shinkichi
Published: November 2005

A new pulse compression filter design technique to realize theoretical minimum S/N loss with zero range sidelobe was indicated in our previous paper. In succession, we have verified in this paper the performance of this pulse compression filter applied to discrete phase‐coded waveforms modulated by Barker code or P4 code via numerical simulations. As a result, we have concluded that the filter derived by our proposed formula surely realizes zero range sidelobe even in the case of oversampling in one code chip, the compressed pulse width is almost the same as the code chip length, and the degradation caused by the Doppler effect is inevitable but equivalent to traditional pulse compression filters. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 10–20, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20263
Heat denaturation, a simple method to improve the immunotherapeutic potential of allergens
Authors: Johansen Pål , Senti Gabriela , Martínez Gómez Julia Maria , Wüthrich Brunello , Bot Adrian , Kündig Thomas M.
Published: November 2005

Allergen‐specific immunotherapy (SIT) leads to a long‐term amelioration of IgE‐ and Th2‐mediated allergic diseases. However, SIT efficiency is low, with years of treatment along with frequent allergic side effects. The goal of this study was to reduce the side effects by destroying IgE‐binding epitopes, i.e. by heat‐denaturation, while preserving the therapeutic effect. Mice were immunised with bee venom, birch pollen, grass pollen or cat hair allergens, or with ovalbumin. Heat‐denatured allergens bound less IgE but enhanced Th1‐dependent IgG2a production as measured by ELISA. The strong IgG2a antibody responses also prevented allergic anaphylaxis in mice, as measured by body temperature drop after a challenge with a high allergen dose. We found that optimal heat‐denaturation of allergens left a small proportion in the native conformation to sufficiently stimulate B cells, while non‐B cell‐mediated effects were probably amplified. The enhanced immunogenicity of heat‐denatured allergens is likely explained by enhanced antigen presentation to T cells due to the particulate nature of heat‐denatured proteins. This enables Th1 skewing of the immune response with strong production of IgG2a in mice. Therefore, heat‐denaturation represents probably the simplest way to enhance the efficiency of SIT while reducing its side effects.
Mechanism of Isomerization of Ni(cyclam) in Aqueous Solutions
Authors: Maimon Eric , Zilbermann Israel , Cohen Haim , Kost Daniel , van Eldik Rudi , Meyerstein Dan
Published: November 2005

Nickel complexes of cyclam and cyclam derivatives isomerize in aqueous solutions via two different mechanisms: i. deprotonation of one of the coordinated amino groups followed by inversion and ii. cleavage of the Ni–N bond followed by inversion. While the first mechanism is relevant for the di‐ and tri‐valent nickel complexes, the second one occurs for the mono‐valent complexes, and for complexes with tertiary amines as ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Catechol Oxidation with Dinuclear Copper Complexes of Aliphatic Tripodal Amino Alcohols
Authors: Jocher Christoph , Pape Tania , Seidel Wolfram W. , Gamez Patrick , Reedijk Jan , Hahn F. Ekkehardt
Published: November 2005

A set of unsymmetrical tripodal (aminoalkyl)bis(hydoxyalkyl)amine ligands H4‐2 to H4‐6 with either ethyl or propyl ligand arms has been prepared and characterized. These ligands react with copper hydroxide and ammonium hexafluorophosphate, copper(II) bromide or tris(triphenylphosphane)copper(I) bromide to give di‐ and polynuclear complexes. The dinuclear copper complexes 9a–f catalyze the oxidation of 3,5‐di‐tert‐butylcatechol (DTBC). The coordination geometry at the copper center is influenced by the length of the side arms resulting in a different reactivity of complexes 9a–f in the DTBC oxidation. Alternative preparation procedures lead in selected cases to the formation of coordination polymers 10a and 10b. The reversible formation of the poly(dinuclear) cations in 10a illustrates that the apical alcohol groups are labile. The solid‐state structures are neither necessarily identical with solution structure nor do they represent the catalytically active species. Electronic spectra, however, agree with a dinuclear structures in solution as indicated by the characteristics of the oxygen–copper‐CT. The observation of comparable catalytic activities for complexes 9a–9d renders the bridging coordination of the catechol by both copper ions of a dinuclear complex moiety unlikely. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Reactions of Furylruthenium Complexes with Oxygen and Trimethylsilyl Azide
Authors: Chang Ku‐Hsien , Sung Hui‐Ling , Lin Ying‐Chih
Published: November 2005

The reaction of the (α‐alkoxyfuryl)ruthenium complexes 4 with oxygen opens the five‐membered furyl ring to give the addition product [Ru]O2CCR=CHCO2CH3, (5, [Ru] = Cp(PPh3)2Ru). Further reactions of 5 with CH3I and with organic acid gave CH3O2CCR=CHCO2CH3, (6), and HO2CCR=CHCO2CH3, (7), respectively. The reaction of 4 with TMSN3 [TMS = (CH3)3Si] gives the ruthenium azide [Ru]–N3 and α‐alkoxyfuran, which is readily hydrolyzed to lactone in acidic medium. Treatment of the cyclopropenylruthenium complex 11b containing a methyl crotonate group with TMSN3 affords the five‐membered‐ring triazole and [Ru]–CN. In this reaction cleavage of the C=C double bond of the three‐membered ring could be caused by consecutive additions of TMSN3 to olefinic carbon atoms of intermediates formed during the reaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Theoretical Study of the Effects of Phosphane Substituents on the Bonding Properties of Acetylene with Ni(PR3)2 (R = H, CH3, F, CF3, C6H5)
Authors: Piacenza Manuel , Rakow Julia , Hyla‐Kryspin Isabella , Grimme Stefan
Published: November 2005

The bond‐formation processes between the d10 metal fragments Ni(PR3)2 (R = H, CH3, F, CF3, Ph) and acetylene have been studied by density functional theory with the BP86 functional and large TZV(2df,2pd) basis sets. The Ni–acetylene bonds have been analyzed in terms of distortion and intrinsic interaction energies within the Dewar–Chatt–Duncanson model of bonding. The intrinsic interaction energies have been corrected for basis set superposition error (BSSE). Linear relationships have been found between the intrinsic interaction energies and the distances of the Ni–C and C≡C bonds as well as with the acetylene–nickel π‐backbonding. No linear relationship with respect to the total interaction energies was found. Despite using large basis sets, BSSE still contaminates the interaction energies by 5–10 %. For the PR3 ligands, the BSSE‐corrected intrinsic interaction energies of acetylene bonding increase in the order P(CF3)3 < PF3 < PPh3 < PH3 < P(CH3)3 from 58.9 to 77.9 kcal mol–1, while the total interaction energies range from 32.9 to 42.4 kcal mol–1 in the order PPh3 < P(CF3)3 < P(CH3)3 < PH3 < PF3. These results reveal that the total influence of PH3 and PPh3 on the thermodynamics of the acetylene bonding is different and therefore in this sense PH3 is not a good model of PPh3 in theoretical calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Reactivity of the Inversely Polarized Arsaalkenes R–As=C(NMe2)2 {R = [(η5‐C5Me5)(CO)2Fe], tBuC(O), 4‐Et–C6H4C(O)} towards Phosphavinylidene Complexes [η5‐(C5H5)(CO)2M=P=C(SiMe3)2] (M = Mo, W)
Authors: Weber Lothar , Bayer Philipp , Uthmann Stefan , Braun Thomas , Stammler Hans‐Georg , Neumann Beate
Published: November 2005

The reaction of the phosphavinylidene complexes [Cp(CO)2M=P=C(SiMe3)2] [Cp = C5H5, M = Mo (2), W (3)] with the ferrioaarsaalkene [Cp*(CO)2Fe–As=C(NMe2)2] (1a) (Cp* = C5Me5) afforded the novel η3‐2‐phospha‐1‐arsaallyl complexes [η3‐{[Fe]–As–P–C(SiMe3)2}M(CO)2Cp] {M = Mo, [Fe] = [Cp*(CO)2Fe] (4a);W (5a)}. Similarly, treatment of equimolar amounts of 3 with arsaalkene tBu–C(O)–As=C(NMe2)2 (1b) gave rise to the formation of [η3‐{tBuC(O)–As–P–C(SiMe3)2}W(CO)2Cp] (5b) by an arsinidene transfer process. In contrast to this, the more reactive arsaalkene 4‐Et–C6H4C(O)–As=C(NMe2)2 (1c) and complex 3 underwent reaction to give the cyclic phosphenium complex [Cp(CO)2W=P–O–Ca(4‐Et–C6H4)=As–Cb(SiMe3)2(P–Cb)] (6). The novel compounds 4a, 5a, 5b, and 6 were characterized by elemental analyses and by means of spectroscopy (IR, 1H, 13C, 31P NMR). Moreover, the molecular structures of 4a, 5b, and 6 were elucidated by X‐ray diffraction analyses.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Enantiopure Ruthenocenes Cp*Ru(1,2‐C5H3R1R2) with a Planar Chiral Cyclopentadienyl Ligand and a Pentamethylcyclopentadienyl Spectator Ligand
Authors: Herberich Gerhard E. , Englert Ulli , Wirth Tobias
Published: November 2005

Kreutzberger’s synthesis was used to produce 6‐(morpholino)fulvene (7a) from 1,3,5‐triazine, cyclopentadiene and morpholine (94 %). Likewise with (S)‐2‐(methoxymethyl)pyrrolidine (HSMP) the 6‐[(S)‐2‐(methoxymethyl)pyrrolidino] analogue 7b was obtained (62 %). Hydride addition from NaBHEt3 in toluene afforded the cyclopentadienides Na[C5H4CH2–N(C2H4)2O] (8a) (83 %) and Na(C5H4CH2–SMP) (8b) (90 %). Cp*Ru(C5H4CH2–SMP) (5) was synthesized from [Cp*RuCl]4 and 8b (84 % yield). The related methyleneiminium salt [Cp*Ru(C5H4CH=SMP)]PF6 (9) was made from [Cp*Ru(MeCN)3]PF6 and 7b and could be transformed into 5 by hydride addition from LiAlH4 in THF. Diastereoselective lithiation of 5 with LisBu in Et2O/cyclohexane and subsequent quenching with electrophiles E–X gave enantiomerically pure (de > 98 %), 1,2‐disubstituted complexes Cp*Ru(E–C5H3CH2–SMP) 10a–i with E = F, Cl, Br, I, Me, CD3, SiMe3, PPh2, Au(PPh3) as oils. The chiral auxiliary was removed from 10a, b, and f by quaternization with MeI and subsequent reductive cleavage with LiAlH4 in THF to afford the exclusively planar chiral complexes Cp*Ru(1‐E‐2‐MeC5H3) 14a (E = F), 14b (E = Cl), and 14f (E = CD3). The complexes 14a,b,f no longer possess central chirality. The crystal structure of 12, a LiI adduct of 10f, gave the absolute configuration via internal reference to the (S)‐stereochemistry of the SMP group. The absolute configuration of the planar chiral complex 14b was determined from the anomalous X‐ray dispersion of the crystals of 14b.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Spectroscopic Comparison of Dinuclear Ti+ and Ti2+ μ‐η1:η1 Dinitrogen Complexes with Cp*/Pentafulvene and Amine/Amide Ligation: Moderate versus Strong Activation of N2
Authors: Studt Felix , Lehnert Nicolai , Wiesler Beatrix E. , Scherer Axel , Beckhaus Rüdiger , Tuczek Felix
Published: November 2005

The two dinuclear, end‐on dinitrogen‐bridged titanium complexes with cp*/pentafulvene ligation, [{(η5‐C5Me5)Ti(η6‐C5H4CR2)}2(μ‐η1:η1‐N2)], R = p‐tolyl (1) and >CR2 = adamantylidene (2), are compared to an analogous titanium dinitrogen complex with a mixed amine/amide/chloride ligand set, [{(Me3Si)2NTiCl(TMEDA)}2(μ‐η1:η1‐N2)] (3; TMEDA = tetramethylethylenediamine). The N–N stretching vibrations of complexes 1 and 2 are observed at 1749 and 1755 cm–1, respectively, indicative of a moderate activation of the dinitrogen ligand. In contrast, the N–N stretch of 3 is located at 1284 cm–1, reflecting a much more highly activated N2 ligand. These findings are in qualitative agreement with N–N bond lengths that have been observed experimentally. DFT calculations reveal that the major difference in the electronic structures of 1, 2, and 3 is the fact that only one of the N2 π* orbitals is (doubly) occupied in the case of 1 and 2, whereas both π* orbitals are (doubly) occupied in the case of 3. The reason for this finding is that in 1 and 2 two of the three electrons of each Ti+ are involved in back‐bonding interactions with the terminal fulvene ligands, whereas no such interactions exist between the Ti2+ centers of 3 and its terminal set of donor ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Reaction of the Heteronuclear Cluster [Cp*IrRu3(μ‐H)2(CO)10] with Alkynes: Stereoselective Binding
Authors: Srinivasan Padmamalini , Leong Weng Kee
Published: November 2005

The reaction of the heteronuclear cluster [Cp*IrRu3(μ‐H)2(CO)10] (1) with the symmetrical alkynes RCCR (R = Ph, Et) afforded the butterfly clusters [Cp*IrRu3(CO)9(RCCR)] (2) and the trinuclear clusters [Cp*IrRu2(CO)7(RCCR)] (3) and [Ru3(CO)8(C4R4)] (4). The clusters 2 and 3 have the alkyne aligned parallel to an Ru–Ir bond. The reaction of 1 with unsymmetrical alkynes also afforded stereoselective binding of the alkyne such that the bulkier substituent was pointing away from the Cp*Ir moiety; with PhCCH, however, all three stereoisomers were obtained. With the bis‐silylated alkynes (R = SiMe3, SiEt3), loss of one trialkylsilyl group occurred to give [Cp*IrRu3(CO)9(HCCR)] and [Ru3(CO)9(μ‐H)(CCR)] (5). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Water‐Soluble Arene Ruthenium Complexes Containing a trans‐1,2‐Diaminocyclohexane Ligand as Enantioselective Transfer Hydrogenation Catalysts in Aqueous Solution (Eur. J. Inorg. Chem. 22/2005)
Authors: Canivet Jérôme , Labat Gael , Stoeckli‐Evans Helen , Süss‐Fink Georg
Published: November 2005

The cover picture shows the postulated catalytic cycle for the pH‐dependent, enantioselective transfer hydrogenation of acetophenone to give phenylethanol in water, using formate as hydrogen donor and (arene)ruthenium(trans‐diaminocyclohexane) as chiral catalyst. This work illustrates the increasing interest for water‐soluble enantioselective catalysts operating in aqueous solution. Details are discussed in the article by G. Süss‐Fink et al. on p. 4493 ff.
The Application of [γ‐(Silyloxy)allylidene]ditin to the Efficient Synthesis of the Chromophore of the Neocarzinostatin Dihydroxycyclopentene‐Based Dienediyne Core
Authors: Madec David , Férézou Jean‐Pierre
Published: November 2005

1‐(tert‐Butyldimethylsilyl)oxy‐3,3‐bis(tributylstannyl)propene (5), a versatile gem‐dimetallic allylic synthon accessible through various synthetic routes, has been condensed with (trimethylsilyl)propiolaldehyde to give the fully functionalised acyclic vinyltin compound 9h, which is a precursor of the complex dihydroxycyclopentene sub‐unit of neocarzinostatin chromophore (NCS) 1. Subsequent transformation into the geminal (E)‐α‐chloro‐(Z)‐α‐iodovinylic intermediate 20, followed by a palladium‐catalysed carbometallation/cyclisation reaction including in situ trapping with either (tributylstannyl)acetylene or the more functionalised 3,3‐diethoxy‐1‐(tributylstannyl)prop‐1‐yne delivered the corresponding alkyne‐substituted 4‐chloro‐1,2‐bis(silyloxy)cyclopent‐3‐enes 21 or 22, respectively. Chlorocyclopentene 21 was subsequently easily transformed into the target dienediyne adduct 23 by Sonogashira condensation with trimethylsilylacetylene. This diastereoselective process is efficient with only six steps and an overall 26 % yield from the allylic ditin precursor 5. More than just an NCS building block, the final acyclic dihydroxycyclopentene‐based dienediyne is also a seco analogue of the NCS chromophore. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Association of Fluorous “Phase‐Vanishing” Method with Visible‐Light Activation in Benzylic Bromination by Bromine
Authors: Podgoršek Ajda , Stavber Stojan , Zupan Marko , Iskra Jernej
Published: November 2005

In this study the “phase‐vanishing” method for diffusion‐controlled addition of a reagent (Br2) to a reaction phase via a fluorous membrane (C8F18) is combined with an additional mode of activation (visible‐light) to achieve the benzyl bromination of various alkyl‐substituted aromatic compounds in a concentrated solution. Benzyl bromination of p‐tert‐butyltoluene proceeded in various solvents including hexane and methanol, while the reaction of the neat substrate showed a similar selectivity as in carbon tetrachloride. The effect of the substituent on the para position of toluene on the course of bromination revealed three processes: benzyl bromination with H, Me, tBu and CO2Et substituents, aromatic bromination with OMe and NHAc substituents and the reaction of the 4‐acetyl derivative at the substituent to form an α‐bromo ketone.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Sequence‐Selective Peptide Recognition with Designed Modules
Authors: Wehner Mark , Janssen Dominic , Schäfer Gerhard , Schrader Thomas
Published: November 2005

A concept for the rational design of sequence‐selective peptide receptors has been extended: in addition to recognition modules for polar, aromatic and basic amino acids, the series has now been completed with new receptor units for apolar and acidic amino acids. The underlying strategy uses the intermolecular β‐sheet stabilization of a dipeptide as a prerequisite to bind its N‐terminal amino acid side chain through a strategically placed recognition tip at the end of a U‐turn protruding from the receptor moiety. Thus, a diaminopyrazole has been covalently attached to Kemp’s triacid by way of a cyclic imide, while a meta‐substituted aniline was coupled as an amide to the pendant third carboxylate arm, bringing the two aromatic units into a sub‐van der Waals distance in a tight conformational lock. NMR titrations, Karplus analyses and Monte‐Carlo simulations demonstrate the effective sequence‐selective recognition of alanine‐containing dipeptides. No example of such a rationally designed set of peptide receptors had existed previously. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Substituted Imidazolo[1,2‐a]piperidinoses and Their Evaluation as Glycosidase Inhibitors
Authors: Dubost Estelle , Le Nouën Didier , Streith Jacques , Tarnus Céline , Tschamber Théophile
Published: November 2005

The synthesis of substituted imidazolo[1,2‐a]‐L‐arabino‐piperidinoses is reported. The substituents are methyl, phenylmethyl, phenylethyl, cyclohexylethyl, pyridinylethyl, piperidinylethyl, phenylpropyl and hydroxymethyl. All substituents are connected to the imidazole moiety. Examination of the inhibitory properties of the newly synthesised compounds against a β‐glucosidase (from almonds) and a β‐galactosidase (from Escherichia coli) lead to the conclusion that the substitution of the C‐2 position on the imidazole moiety with cyclohexylethyl or phenylethyl gives the best results (Ki = 2 and 4 nM, respectively, against a β‐galactosidase) as compared with the non‐substituted azasugar. The synthesis of the imidazolo[1,2‐a]‐D‐xylo‐piperidinose substituted with phenylethyl is also reported, as well as its inhibitory potency against the β‐xylosidase from Aspergillus niger.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Synthesis and Structure of Linear and Dendritic Thiourea‐Linked Glycooligomers
Authors: Jiménez Blanco José L. , Bootello Purificación , Ortiz Mellet Carmen , García Fernández José M.
Published: November 2005

An efficient strategy to produce unnatural glycooligomers containing thiourea intersaccharide bridges has been developed. The presence of the thiourea groups in these oligomers should promote the association with polyphosphates, including nucleic acids, due to the hydrogen‐bonding capabilities of the thioureas. Moreover, glycooligomers built from thiourea groups should form complex secondary and tertiary structures due to the interplay of hydrogen bonding and rotational restriction at the bonds adjacent to thiocarbonyl groups. Herein, the preparation and conformational properties of both linear and dendritic architectures are described. This synthetic method relies on the coupling of peracetylated azidoglycosyl isothiocyanates and fully unprotected amine‐functionalised growing oligomers. Deacetylation of the hemiacetylated thiourea adduct and reduction of the azido groups allow entry into a new coupling cycle. The procedure is quite general, should be easily extended to molecular diversity‐oriented and solid‐phase approaches and will allow the investigation of intermolecular interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Preparation of 2‐Amino‐4H‐chromene Derivatives from Coumarins in Basic Media
Authors: Curini Massimo , Rosati Ornelio , Marcotullio Maria Carla , Montanari Francesca , Campagna Valerio , Pace Vittorio , Cravotto Giancarlo
Published: November 2005

The reaction of coumarin with cyanoacetate derivatives in the presence of a nucleophilic base (alkoxides or piperidine) follows an interesting pathway that involves both a coumarin skeletal rearrangement and a Michael addition, via a coumaric acid derivative, to afford a substituted 4H‐chromene skeleton. The particular behavior of this process influences the performance and the type of compounds that can be obtained. We demonstrate that the use of an excess of cyanoacetate affords the 4H‐chromene derivative in high yield. An explanation of the mechanism involved in this process is proposed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Bridged Azabicycles from Pyridines and Pyrrole by a Diallylboration – Ring Closing Metathesis Sequence
Authors: Kuznetsov Nikolai Yu. , Khrustalev Viktor N. , Godovikov Ivan A. , Bubnov Yuri N.
Published: November 2005

A straightforward method for the preparation of bridged azabicycles by a diallylboration–ring closing metathesis (RCM) sequence was elaborated. The precursors for the metathesis reaction were prepared by reductive trans‐diallylation of aromatic heterocycles such as pyridines, isoquinoline and pyrrole with triallylborane and an alcohol. Heating of the trans isomers with one equivalent of triallylborane allowed the corresponding cis isomers – or (in the case of pyrrole) a mixture of cis and trans isomers – to be obtained. Boc protection of the amine function gave the precursor for the RCM reaction with axial orientations of allylic groups. The chemical yields of this stage are very good and the amounts of Grubbs’ catalyst required for the reaction do not exceed 2.5 mol‐% (first generation cat.) or 3.7 mol‐% (second generation cat.). Azabicyclo[4.2.1]nonene, obtained from pyrrole, is a key structural motif of the toxin pinnamine. The structures of cis‐1,3‐diallyl‐1,2,3,4‐tetrahydroisoquinoline and azabicyclo[4.3.1]decadiene were studied by single‐crystal X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Silylated Vinyloxiranes – Recent Advances and Synthetic Applications
Authors: Marion Frédéric , Calvet Sandrine , Marié Jean‐Charles , Courillon Christine , Malacria Max
Published: November 2005

Stereoselective preparation of α‐silylated α‐quaternary unsaturated aldehydes 2 from variously substituted silylated vinyloxiranes is achieved with the aid of palladium(0) catalysis under smooth experimental conditions. One example of a versatile application of this rearrangement reaction, in the case of the tert‐butyldimethyl(3‐vinyloxiran‐2‐yl)silane derivative 1a, has resulted in one‐pot diastereoselective syntheses of the highly functionalized polysubstituted δ‐lactones 33–39, the reactivity of which has been studied.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Conformational Restriction of the Calix[6]arene Macrocycle by the Ritter Reaction
Authors: Vatsouro Ivan M. , Shokova Elvira A. , Shestakova Alla K. , Chertkov Vyacheslav A. , Kovalev Vladimir V.
Published: November 2005

Herein we report on the development of a novel and efficient approach to the restriction of the conformational mobility of calix[6]arenes. The method involves the addition of tertiary alcohols to calix[6]arenes with one, three and six cyanomethoxy groups attached to the lower rim under modified Ritter reaction conditions. Alkylation of monocyanomethoxy‐p‐tert‐butylcalix[6]arene (1) and 37,39,41‐trimethoxy‐38,40,42‐tricyanomethoxy‐p‐tert‐butylcalix[6]arene (2) with 3‐R‐1‐adamantanols (R = H, CH2COOH) in trifluoroacetic acid afforded the corresponding mono‐ and triamides with cone‐like conformations. The partial alkylation of hexanitrile derivatives showed unexpected regioselectivity. Addition of 1‐adamantanol or tert‐butyl alcohol to hexacyanomethoxy‐p‐X‐calix[6]arenes 3a–c (X = tert‐butyl, 1‐adamantyl, 3‐methoxycarbonylmethyl‐1‐adamantyl) gave 37,40‐dinitrile‐38,39,41,42‐tetraamides as the major products. These tetraamides are conformationally restricted in solution over a wide range of temperatures and adopt a flattened 1,2,3‐alternate conformation, as shown by 2D and variable‐temperature NMR experiments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
3‐Substituted Cyclopenta[c]pyrans: Synthesis and Electrophilic Substitutions
Authors: Güllük Eduard , Bogdan Elena , Christl Manfred
Published: November 2005

The literature procedure for the preparation of the parent cyclopenta[c]pyran (1) was shown to provide only a low yield on mechanistic grounds. Intended as an alternative starting material for the synthesis of 1, the cyclopenta[c]pyran‐3‐ones 10 were prepared. However, their conversion into 1 could be achieved at best in 1 % yield. Derivatives of 1 with an oxygen functionality in the 3‐position were obtained by deprotonation, silylation and benzoylation of 10b, giving rise to the lithium enolate 15, the ketene acetals 16–18 and the ketene hemiacetal ester 19, respectively. The olefination of 10b with substituted methylenetriphenylphosphoranes furnished cyclopenta[c]pyran‐3‐ylacetonitrile (21) and methyl cyclopenta[c]pyran‐3‐ylacetate (22) in modest yields. These compounds as well as the primary alcohol 23, which resulted from 22 on reduction with LiAlH4, underwent an electrophilic aromatic substitution reaction with trifluoroacetic anhydride to form the 7‐(trifluoroacetyl)cyclopenta[c]pyrans 24–27. In the case of the acetonitrile 27, a second and a third trifluoroacetyl group were readily introduced, giving rise to the highly resonance‐stabilised anions 28 and 29, the latter exhibiting a strong green fluorescence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Substituent Effects in Tandem Ring‐Closing Metathesis Reactions of Dienynes
Authors: Boyer François‐Didier , Hanna Issam
Published: November 2005

Several dienynes bearing different substituents have been synthesized and subjected to a ring‐closing metathesis (RCM) reaction using ruthenium carbene complexes. Dienynes containing a pre‐existing ring and a quaternary center attached to the alkyne give the expected tandem metathesis products in high yields. For these substrates, a high selectivity for different ring sizes was achieved by modifying the reactivity of one alkene. In one case, an unusual non‐metathetic activity of the second‐generation Grubbs catalyst was observed and the cycloisomerization product was obtained as the major product. In the absence of favorable factors, especially when the starting substrates contain hindered alkenes, a long tether chain and/or an ester group on the alkyne part, the tandem process is slowed down or completely impeded. In these cases, dienynes behave like simple enynes and afford initial metathesis products whose further reactions give dimeric compounds.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Dendritic Branches with Peripheral Fullerene Subunits
Authors: Hahn Uwe , Hosomizu Kohei , Imahori Hiroshi , Nierengarten Jean‐François
Published: November 2005

Highly soluble dendritic branches with two, four, eight or 16 methanofullerene subunits at their peripheries and carboxylic acid functions at their focal points have been prepared by a convergent approach. Starting from a methanofullerene derivative possessing a tert‐butyl ester function, the successive dendrimer generations were obtained by repetition of a reaction sequence involving cleavage of the tert‐butyl ester moiety under acidic conditions, followed by a DCC‐mediated esterification reaction with an A2B building block possessing two benzylic alcohol functions and a tert‐butyl ester group. This repetitive synthetic sequence is very efficient and allowed the dendritic growth up to the fifth‐generation derivative, containing 16 peripheral fullerene subunits. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)