bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes
Authors: Kanibolotsky Alexander L. , Forgie John C. , McEntee Greg J. , Talpur M. Munsif A. , Skabara Peter J. , Westgate Thomas D. J. , McDouall Joseph J. W. , Auinger Michael , Coles Simon J. , Hursthouse Michael B. 
Published: September 2009

AbstractThe synthesis of two [4]‐dendralene compounds incorporating thiophene‐(p‐nitrophenyl) donor–acceptor units is presented. The dendralenes adopt two different conformers in solution and solid state and the transformation between the structures can be controlled by light and heat. The electron‐donating components of the dendralenes are represented by bromothienyl (in 13) and ethylenedioxythiophene(EDOT)‐thienyl (in 15) end‐groups. The most facile transformation involves the isomerisation of donor–acceptor conjugated systems (a conformers) into structures in which only the thiophenes are conjugated (b conformers), and this process is driven by ambient light. The structures of the two conformers of compound 13 are confirmed by single‐crystal X‐ray diffraction studies and the structural changes in both compounds have been monitored by 1H NMR spectroscopy and absorption studies. The transformations were found to be first‐order processes with rate constants of k=0.0027 s−1 and k=0.00022 s−1 for 13 and 15, respectively. Density functional theory calculations at the B3LYP/6‐31G* level give credence to the proposed mechanism for the a→b conversion, which involves photoinduced intramolecular charge transfer (ICT) as the key step. The EDOT derivative (15) can be polymerised by electrochemical oxidation and a combination of cyclic voltammetry and UV/Vis spectroelectrochemical experiments indicate that the a conformer can be trapped and stabilised in the solid state.
An Organocatalytic Asymmetric Tandem Reaction for the Construction of Bicyclic Skeletons
Authors: Cao Chun‐Li , Zhou You‐Yun , Zhou Jian , Sun Xiu‐Li , Tang Yong , Li Yu‐Xue , Li Guang‐Yu , Sun Jie 
Published: September 2009

AbstractCyclic ketones react with (E)‐2‐nitroallylic acetates in the presence of catalytic pyrrolidine‐thiourea, which affords bicyclic skeletons with four or five stereocenters in one single reaction with up to 98 % eein moderate to high yields. The cooperative effects of both enamine and the Brønsted acid are found to be crucial for the high reactivity and enantioselectivity of this cascade reaction, which is demonstrated by both theoretical calculation and experimental data.
Homoleptic Organoderivatives of High‐Valent Nickel(III)
Authors: Alonso Pablo J. , Arauzo Ana B. , García‐Monforte María Angeles , Martín Antonio , Menjón Babil , Rillo Conrado , Tomás Milagros 
Published: September 2009

AbstractHomoleptic perhalophenyl derivatives of divalent nickel complexes with the general formula [NBu4]2[NiII(C6X5)4] [X=F (1), Cl (2)] have been prepared by low‐temperature treatment of the halo‐complex precursor [NBu4]2[NiBr4] with the corresponding organolithium reagent LiC6X5. Compounds 1 and 2 are electrochemically related by reversible one‐electron exchange processes with the corresponding organometallate(III) compounds [NBu4][NiIII(C6X5)4] [X=F (3), Cl (4)]. The potentials of the [NiIII(C6X5)4]−/[NiII(C6X5)4]2− couples are +0.07 and −0.11 V for X=F or Cl, respectively. Compounds 3 and 4 have also been prepared and isolated in good yield by chemical oxidation of 1 or 2 with bromine or the amminium salt [N(C6H4Br‐4)3][SbCl6]. The [NiIII(C6X5)4]− species have SP‐4 structures in the salts 3 and 4, as established by single‐crystal X‐ray diffraction methods. The [NiII(C6F5)4]2− ion in the parent compound 1 has also been found to exhibit a rather similar SP‐4 structure. According to their SP‐4 geometry, the NiIII compounds (d7) behave as S=1/2 systems both at microscopic (EPR) and macroscopic levels (ac and dc magnetization measurements). The spin Hamiltonian parameters obtained from the analysis of the magnetic behavior of 3 and 4 within the framework of ligand field theory show that the unpaired electron is centered mainly on the metal atom, with >97 % estimated d contribution. Thermal decomposition of 3 and 4 proceeds with formation of the corresponding C6X5C6X5 coupling compounds.
Modification of Supramolecular Binding Motifs Induced By Substrate Registry: Formation of Self‐Assembled Macrocycles and Chain‐Like Patterns
Authors: Fendt Leslie‐Anne , Stöhr Meike , Wintjes Nikolai , Enache Mihaela , Jung Thomas A. , Diederich François 
Published: September 2009

AbstractThe self‐assembly properties of two ZnII porphyrin isomers on Cu(111) are studied at different coverage by means of scanning tunneling microscopy (STM). Both isomers are substituted in their meso‐positions by two voluminous 3,5‐di(tert‐butyl)phenyl and two rod‐like 4′‐cyanobiphenyl groups, respectively. In the trans‐isomer, the two 4′‐cyanobiphenyl groups are opposite to each other, whereas they are located at right angle in the cis‐isomer. For coverage up to one monolayer, the cis‐substituted porphyrins self‐assemble to form oligomeric macrocycles held together by antiparallel CN⋅⋅⋅CN dipolar interactions and CN⋅⋅⋅H‐C(sp2) hydrogen bonding. Cyclic trimers and tetramers occur most frequently but everything from cyclic dimers to hexamers can be observed. Upon annealing of the samples at temperatures >150 °C, dimeric macrocyclic structures are observed, in which the two porphyrins are bridged by Cu atoms, originating from the surface, under formation of two CN⋅⋅⋅Cu⋅⋅⋅NC coordination bonds. The trans‐isomer builds up linear chains on Cu(111) at low coverage, whereas for higher coverage the molecules assemble in a periodic, densely packed structure. Both cis‐ and trans‐bis(4′‐cyanobiphenyl)‐substituted ZnII porphyrins behave very differently on Cu(111) compared to similar porphyrins in literature on less reactive surfaces such as Au(111) and Ag(111). On the latter surfaces, there is no signal visible between molecular orientation and the crystal directions of the substrate, whereas on Cu(111), very strong adsorbate–substrate interactions have a dominating influence on all observed structures. This strong porphyrin–substrate interaction enables a much broader variety of structures, including also less favorable intermolecular bonding motifs and geometries.
Red‐ and Green‐Emitting Iridium(III) Complexes for a Dual Barometric and Temperature‐Sensitive Paint
Authors: Fischer Lorenz H. , Stich Matthias I. J. , Wolfbeis Otto S. , Tian Nan , Holder Elisabeth , Schäferling Michael 
Published: September 2009

AbstractA new dual luminescent sensitive paint for barometric pressure and temperature (T) is presented. The green‐emitting iridium(III) complex [Ir(ppy)2(carbac)] (ppy=2‐phenylpyridine; carbac=1‐(9H‐carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐dione) was applied as a novel probe for T along with the red‐emitting complex [Ir(btpy)3], (btpy=2‐(benzo[b]thiophene‐2‐yl)pyridine) which functions as a barometric (in fact oxygen‐sensitive) probe. Both iridium complexes were dissolved in different polymer materials to achieve optimal responses. The probe [Ir(ppy)2(carbac)] was dispersed in gas‐blocking poly(acrylonitrile) microparticles in order to suppress any quenching of its luminescence by oxygen. The barometric probe [Ir(btpy)3], in turn, was incorporated in a cellulose acetate butyrate film which exhibits good permeability for oxygen. The effects of temperature on the response of the oxygen probe can be corrected by simultaneous optical determination of T, as the poly(acrylonitrile) microparticles containing the temperature indicator are incorporated into the film. The phosphorescent signals of the probes for T and barometric pressure, respectively, can be separated by optical filters due to the ≈75 nm difference in their emission maxima. The dual sensor is applicable to luminescence lifetime imaging of T and barometric pressure. It is the first luminescent dual sensor material for barometric pressure/T based exclusively on the use of IrIII complexes in combination with luminescence lifetime imaging.
Designed Topology and Site‐Selective Metal Composition in Tetranuclear [MM′⋅⋅⋅M′M] Linear Complexes
Authors: Barrios Leoní A. , Aguilà David , Roubeau Olivier , Gamez Patrick , Ribas‐Ariño Jordi , Teat Simon J. , Aromí Guillem 
Published: September 2009

AbstractThe ligand 1,3‐bis[3‐oxo‐3‐(2‐hydroxyphenyl)propionyl]benzene (H4L), designed to align transition metals into tetranuclear linear molecules, reacts with MII salts (M=Ni, Co, Cu) to yield complexes with the expected [MM⋅⋅⋅MM] topology. The novel complexes [Co4L2(py)6] (2; py=pyridine) and [Na(py)2][Cu4L2(py)4](ClO4) (3) have been crystallographically characterised. The metal sites in complexes 2 and 3, together with previously characterised [Ni4L2(py)6] (1), favour different coordination geometries. These have been exploited for the deliberate synthesis of the heterometallic complex [Cu2Ni2L2(py)6] (4). Complexes 1, 2, 3 and 4 exhibit antiferromagnetic interactions between pairs of metals within each cluster, leading to S=0 spin ground states, except for the latter cluster, which features two quasi‐independent S=1/2 moieties within the molecule. Complex 4 gathers the structural and physical conditions, thus allowing it to be considered as prototype of a two‐qbit quantum gate.
Axially Chiral Facial Amphiphiles with a Dihydronaphthopentaphene Structure as Molecular Tweezers for SWNTs
Authors: Marquis Renaud , Kulikiewicz Krystyna , Lebedkin Sergei , Kappes Manfred M. , Mioskowski Charles , Meunier Stéphane , Wagner Alain 
Published: September 2009

AbstractSyntheses of chiral 6,15‐dihydronaphtho[2,3‐c]pentaphene derivatives of opposite configurations are reported. Starting from anthracene, the strategy involves two key steps: a Diels–Alder reaction on a prochiral dianthraquinone, and an enantiomeric resolution using (−)‐menthol. The final molecules exhibit very strong optical activity, as shown by their circular dichroism spectra, and are examples of chiral facial amphiphiles. Their adsorption at the surface of single‐walled carbon nanotubes (SWNTs) has also been studied, and has been found to occur preferentially on 0.8–1.0 nm diameter nanotubes among the population of a high‐pressure CO conversion (HiPco) SWNT sample (0.8–1.2 nm). The synthesised facial amphiphiles act as nano‐tweezers for the diameter‐selective solubilisation of SWNTs in water. The expected optical activities of the SWNT samples solubilised by each of the chiral amphiphiles have been studied by circular dichroism spectroscopy, but the results are not yet conclusive.
Total Synthesis of the Bicyclic Depsipeptide HDAC Inhibitors Spiruchostatins A and B, 5′′‐epi‐Spiruchostatin B, FK228 (FR901228) and Preliminary Evaluation of Their Biological Activity
Authors: Narita Koichi , Kikuchi Takuya , Watanabe Kazuhiro , Takizawa Toshiya , Oguchi Takamasa , Kudo Kyosuke , Matsuhara Keisuke , Abe Hideki , Yamori Takao , Yoshida Minoru , Katoh Tadashi 
Published: September 2009

AbstractThe bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins A and B, 5′′‐epi‐spiruchostatin B and FK228 were efficiently synthesized in a convergent and unified manner. The synthetic method involved the following crucial steps: i) a Julia–Kocienski olefination of a 1,3‐propanediol‐derived sulfone and a L‐ or D‐malic acid‐derived aldehyde to access the most synthetically challenging unit, (3S or 3R,4E)‐3‐hydroxy‐7‐mercaptohept‐4‐enoic acid, present in a D‐alanine‐ or D‐valine‐containing segment; ii) a condensation of a D‐valine‐D‐cysteine‐ or D‐allo‐isoleucine‐D‐cysteine‐containing segment with a D‐alanine‐ or D‐valine‐containing segment to directly assemble the corresponding seco‐acids; and iii) a macrocyclization of a seco‐acid using the Shiina method or the Mitsunobu method to construct the requisite 15‐ or 16‐membered macrolactone. The present synthesis has established the C5′′ stereochemistry of spiruchostatin B. In addition, HDAC inhibitory assay and the cell‐growth inhibition analysis of the synthesized depsipeptides determined the order of their potency and revealed some novel aspects of structure–activity relationships. It was also found that unnatural 5′′‐epi‐spiruchostatin B shows extremely high selectivity (ca. 1600‐fold) for class I HDAC1 (IC50=2.4 nM) over class II HDAC6 (IC50=3900 nM) with potent cell‐growth‐inhibitory activity at nanomolar levels of IC50 values.
Supramolecular Architectures by Fullerene‐Bridged Bis(permethyl‐β‐cyclodextrin)s with Porphyrins
Authors: Zhang Ying‐Ming , Chen Yong , Yang Yang , Liu Peng , Liu Yu 
Published: September 2009

AbstractThe Hirsch–Bingel reaction of bis{4‐methyl[1,2,3]triazolyl}malonic ester‐bridged bis(permethyl‐β‐cyclodextrin) 1 with C60 has led to the formation of a new fullerene‐bridged bis(permethyl‐β‐cyclodextrin) 2, which has been comprehensively characterized by NMR spectroscopy, MALDI‐MS, and elemental analysis. Taking advantage of the high affinity between 2 and 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrin (3) or [5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphinato]zinc(II) (4), linear supramolecular architectures with a width of about 2 nm and a length ranging from hundreds of nanometers to micron dimension were conveniently constructed and fully investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Significantly, the photoinduced electron‐transfer (PET) process between porphyrin and C60 moieties takes place within the 2⋅3 and 2⋅4 supramolecular architectures under light irradiation, leading to the highly efficient quenching of the porphyrin fluorescence. The PET process and the charge‐separated state were investigated by means of fluorescence spectroscopy, fluorescence decay, cyclic voltammetry, and nanosecond transient absorption measurements.
Efficient Synthesis of Cryptophycin‐52 and Novel para‐Alkoxymethyl Unit A Analogues
Authors: Eißler Stefan , Bogner Tobias , Nahrwold Markus , Sewald Norbert 
Published: September 2009

AbstractCryptophycins are a family of highly cytotoxic, cyclic depsipeptides. They display antitumour activity that is largely maintained for multi‐drug‐resistant tumour cells. Cryptophycins are composed of four building blocks (units A–D) that correspond to the respective amino and hydroxy acids. A new synthetic route to unit A allows the selective generation of all four stereogenic centres in a short, efficient and reliable synthesis and contributes to an easier and faster synthesis of cryptophycins. The first two stereogenic centres are introduced by a catalytic asymmetric dihydroxylation, whereas the remaining two stereogenic centres are introduced with substrate control of diastereoselectivity. The stereogenic diol function also serves as the epoxide precursor. The approach was used to synthesise the native unit A building block as well as three para‐alkoxymethyl analogues from which cryptophycin‐52 and three analogous cryptophycins were prepared. Macrocyclisation of the seco‐depsipeptides was based on ring‐closing metathesis.
Estimation in capture–recapture models when covariates are subject to measurement errors and missing data
Authors: Xi Liqun , Watson Ray , Wang Ji‐Ping , Yip Paul S. F. 
Published: September 2009

AbstractFor capture–recapture models when covariates are subject to measurement errors and missing data, a set of estimating equations is constructed to estimate population size and relevant parameters. These estimating equations can be solved by an algorithm similar to the EM algorithm. The proposed method is also applicable to the situation when covariates with no measurement errors have missing data. Simulation studies are used to assess the performance of the proposed estimator. The estimator is also applied to a capture–recapture experiment on the bird speciesPrinia flaviventrisin Hong Kong. The Canadian Journal of Statistics 37: 645–658; 2009 © 2009 Statistical Society of Canada
Distribution of prolactin‐responsive neurons in the mouse forebrain
Authors: Brown Rosemary S.E. , Kokay Ilona C. , Herbison Allan E. , Grattan David R. 
Published: September 2009

AbstractProlactin has numerous biological actions in the brain, and transgenic mice are increasingly being used to investigate these actions. The present study aimed to provide a detailed mapping of the prolactin‐responsive neurons in the female mouse forebrain by describing the distribution of prolactin receptor mRNA by in situ hybridization, and measuring prolactin‐induced phosphorylation of signal transducer and activation of transcription 5 (pSTAT5) by immunohistochemistry. For in situ hybridization, a probe designed to detect both long and short receptor isoforms showed mRNA expression in a heterogeneous manner within the forebrain. Strong expression was observed in the rostral hypothalamus, particularly in periventricular regions, as well as in the arcuate and ventromedial nuclei of the mediobasal hypothalamus. There was also significant expression in some nonhypothalamic regions, notably high expression in the choroid plexus, and lower levels of expression in the medial amygdala, bed nucleus of the stria terminalis, and lateral septum. Prolactin‐induced pSTAT5, detected by immunohistochemistry, provided a functional index of prolactin receptor activation in neurons. Prolactin‐induced pSTAT5 was only observed in areas containing prolactin receptor mRNA, and was particularly prominent in the rostral and mediobasal hypothalamus. Most other areas that contained prolactin receptor mRNA also showed positive signal for prolactin‐induced pSTAT5. The major exceptions were paraventricular nucleus and median preoptic nucleus, in which prolactin receptor mRNA was observed, but no induction of pSTAT5 by prolactin. The data provide key neuroanatomical information facilitating the use of the mouse model for furthering our understanding of prolactin actions in the brain. J. Comp. Neurol. 518:92–102, 2010. © 2009 Wiley‐Liss, Inc.
Differential localization of γ‐aminobutyric acid type a and glycine receptor subunits and gephyrin in the human pons, medulla oblongata and uppermost cervical segment of the spinal cord: An immunohistochemical study
Authors: Waldvogel H.J. , Baer K. , Eady E. , Allen K.L. , Gilbert R.T. , Mohler H. , Rees M.I. , Nicholson L.F.B. , Faull R.L.M. 
Published: September 2009

AbstractGephyrin is a multifunctional protein responsible for the clustering of glycine receptors (GlyR) and γ‐aminobutyric acid type A receptors (GABAAR). GlyR and GABAAR are heteropentameric chloride ion channels that facilitate fast‐response, inhibitory neurotransmission in the mammalian brain and spinal cord. We investigated the immunohistochemical distribution of gephyrin and the major GABAAR and GlyR subunits in the human light microscopically in the rostral and caudal one‐thirds of the pons, in the middle and caudal one‐thirds of the medulla oblongata, and in the first cervical segment of the spinal cord. The results demonstrate a widespread pattern of immunoreactivity for GlyR and GABAAR subunits throughout these regions, including the spinal trigeminal nucleus, abducens nucleus, facial nucleus, pontine reticular formation, dorsal motor nucleus of the vagus nerve, hypoglossal nucleus, lateral cuneate nucleus, and nucleus of the solitary tract. The GABAAR α1and GlyR α1and β subunits show high levels of immunoreactivity in these nuclei. The GABAAR subunits α2, α3, β2,3, and γ2present weaker levels of immunoreactivity. Exceptions are intense levels of GABAAR α2subunit immunoreactivity in the inferior olivary complex and high levels of GABAAR α3subunit immunoreactivity in the locus coeruleus and raphe nuclei. Gephyrin immunoreactivity is highest in the first segment of the cervical spinal cord and hypoglossal nucleus. Our results suggest that a variety of different inhibitory receptor subtypes is responsible for inhibitory functions in the human brainstem and cervical spinal cord and that gephyrin functions as a clustering molecule for major subtypes of these inhibitory neurotransmitter receptors. J. Comp. Neurol. 518:305–328, 2010. © 2009 Wiley‐Liss, Inc.
Selective long‐term reorganization of the corticospinal projection from the supplementary motor cortex following recovery from lateral motor cortex injury
Authors: McNeal David W. , Darling Warren G. , Ge Jizhi , Stilwell‐Morecraft Kimberly S. , Solon Kathryn M. , Hynes Stephanie M. , Pizzimenti Marc A. , Rotella Diane L. , Tyler Vanadurongvan  , Morecraft Robert J. 
Published: September 2009

AbstractBrain injury affecting the frontal motor cortex or its descending axons often causes contralateral upper extremity paresis. Although recovery is variable, the underlying mechanisms supporting favorable motor recovery remain unclear. Because the medial wall of the cerebral hemisphere is often spared following brain injury and recent functional neuroimaging studies in patients indicate a potential role for this brain region in the recovery process, we investigated the long‐term effects of isolated lateral frontal motor cortical injury on the corticospinal projection (CSP) from intact, ipsilesional supplementary motor cortex (M2). After injury to the arm region of the primary motor (M1) and lateral premotor (LPMC) cortices, upper extremity recovery is accompanied by terminal axon plasticity in the contralateral CSP but not the ipsilateral CSP from M2. Furthermore, significant contralateral plasticity occurs only in lamina VII and dorsally within lamina IX. Thus, selective intraspinal sprouting transpires in regions containing interneurons, flexor‐related motor neurons, and motor neurons supplying intrinsic hand muscles, which all play important roles in mediating reaching and digit movements. After recovery, subsequent injury of M2 leads to reemergence of hand motor deficits. Considering the importance of the CSP in humans and the common occurrence of lateral frontal cortex injury, these findings suggest that spared supplementary motor cortex may serve as an important therapeutic target that should be considered when designing acute and long‐term postinjury patient intervention strategies aimed to enhance the motor recovery process following lateral cortical trauma. J. Comp. Neurol. 518:586–621, 2010. © 2009 Wiley‐Liss, Inc.
Melanocortin‐4 receptor expression in a vago‐vagal circuitry involved in postprandial functions
Authors: Gautron Laurent , Lee Charlotte , Funahashi Hisayuki , Friedman Jeffrey , Lee Syann , Elmquist Joel 
Published: September 2009

AbstractVagal afferents regulate energy balance by providing a link between the brain and postprandial signals originating from the gut. In the current study, we investigated melanocortin‐4 receptor (MC4R) expression in the nodose ganglion, where the cell bodies of vagal sensory afferents reside. By using a line of mice expressing green fluorescent protein (GFP) under the control of the MC4R promoter, we found GFP expression in approximately one‐third of nodose ganglion neurons. By using immunohistochemistry combined with in situ hybridization, we also demonstrated that ∼20% of GFP‐positive neurons coexpressed cholecystokinin receptor A. In addition, we found that the GFP is transported to peripheral tissues by both vagal sensory afferents and motor efferents, which allowed us to assess the sites innervated by MC4R‐GFP neurons. GFP‐positive efferents that co‐expressed choline acetyltransferase specifically terminated in the hepatic artery and the myenteric plexus of the stomach and duodenum. In contrast, GFP‐positive afferents that did not express cholinergic or sympathetic markers terminated in the submucosal plexus and mucosa of the duodenum. Retrograde tracing experiments confirmed the innervation of the duodenum by GFP‐positive neurons located in the nodose ganglion. Our findings support the hypothesis that MC4R signaling in vagal afferents may modulate the activity of fibers sensitive to satiety signals such as cholecystokinin, and that MC4R signaling in vagal efferents may contribute to the control of the liver and gastrointestinal tract. J. Comp. Neurol. 518:6–24, 2010. © 2009 Wiley‐Liss, Inc.