bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dutch Resolution Variant of the Classical Resolution of Racemates by Formation of Diastereomeric Salts: Family Behaviour in Nucleation Inhibition
Authors: Dalmolen Jan , Tiemersma‐Wegman Theodora D. , Nieuwenhuijzen José W. , van der Sluis Marcel , van Echten Erik , Vries Ton R. , Kaptein Bernard , Broxterman Quirinius B. , Kellogg Richard M. 
Published: July 2005

AbstractThe resolution of racemates through their diastereomeric salts can be positively affected by the addition of small amounts of suitable nucleation inhibitors. This discovery is a logical extension of “Dutch Resolution”, in which equimolar amounts of resolving agents that are members of the same family (i.e., structurally related) are used. We conducted a systematic search for nucleation inhibitors of the resolving agent 1‐phenylethylamine. A wide range of amines that bear possible family resemblances to 1‐phenylethylamine was investigated. It was found that (R)‐1‐phenylbutylamine is a good inhibitor of (R)‐1‐phenylethylamine. Results of turbidity measurements showed that, for the model case of mandelic acid resolution, the chief effect of this inhibitor was to widen the metastable zone for the more soluble diastereomer. This observation is in accordance with previous experience. Further scouting for possible family members revealed a wide variation in the effectiveness of inhibitors, dependent on their structure. By far the most effective inhibitors are bifunctional 1‐phenylethylamine and/or 1‐phenylbutylamine analogues. The effect of racemic inhibitors was found to approach that of enantiomerically pure inhibitors of the same absolute configuration of the 1‐phenylethylamine used for resolution. The most effective inhibitors were tested for the resolution of a structural variety of racemates, and were shown to be broadly applicable.
Novel Enantioselective Receptors for N‐Protected Glutamate and Aspartate
Authors: Ragusa Andrea , Rossi Sara , Hayes Joseph M. , Stein Matthias , Kilburn Jeremy D. 
Published: July 2005

AbstractA series of chiral bisthiourea macrocycles 1–4 have been prepared and their binding properties with various dicarboxylate salts have been examined by using NMR titration and isothermal calorimetry experiments. Macrocycle 1, in particular, favours the 1:1 binding of N‐protected L‐glutamate and aspartate, but favours 1:2 binding of the corresponding D‐amino acids in polar solvents (dimethyl sulfoxide and acetonitrile). The macrocycles, however, do not bind carboxylates at all in the less competitive solvent chloroform. The binding properties of these macrocyles are sensitive to small structural changes as demonstrated by the altered binding properties of macrocycles 2–4 compared with 1.
Dipyrrolyldiketone Difluoroboron Complexes: Novel Anion Sensors With C‐H⋅⋅⋅X− Interactions
Authors: Maeda Hiromitsu , Kusunose Yukio 
Published: July 2005

Abstract1,3‐Dipyrrolyl‐1,3‐propanediones, synthesized from pyrroles and malonyl chloride, form BF2 complexes, which represent a new class of naked‐eye sensors for halide and oxoanions. The association mode for the interactions of both the pyrrolyl NH and bridging CH protons with anions was confirmed by 1H NMR chemical shifts in CD2Cl2 and supported by theoretical studies. The binding constants (Ka) were estimated as 8.1×104, 2.0×103, 3.3×102, 1.3×104, and 80 m−1 for F−, Cl−, Br−, H2PO4−, and HSO4− by UV/Vis absorption spectral changes in CH2Cl2. Augmentation of Ka compared with dipyrrolylquinoxaline for H2PO4− is much larger than those for other anions. Contrary to other anions, F− quenches the emission almost completely, which was detected by the fluorescence spectrum as well as the naked‐eye. In the case of the chloride anion complex, the formation of Cl−‐bridged 1D networks, in which anion is associated with two BF2 complexes, is observed in the solid state.
Identification of Two Isomers from an Organic Mixture by Double‐Stimulated‐Echo NMR and Construction of the DOSY Spectra by the Regularized Resolvent Transform Method
Authors: Thureau Pierre , Thévand André , Ancian Bernard , Escavabaja Philippe , Armstrong Geoffrey S. , Mandelshtam Vladimir A. 
Published: July 2005

AbstractDOSY‐NMR experiments were used to characterize two structural isomers that have different shapes, but identical mass fragmentation patterns, from an organic mixture. It is shown that the spherical molecule diffuses faster than the ellipsoidal one. This distinct behaviour is tentatively explained in terms of microfriction effects from the solvent. Finally, to increase the resolution and efficiency of the 2D DOSY map construction, the data were treated with the regularized resolvent transform method. This method provides good separation for mildly overlapped peaks and requires fewer points than other classical DOSY processing methods.
Fluoroalkylation of Porphyrins: A Facile Synthesis of Trifluoromethylated Porphyrins by a Palladium‐Catalyzed Cross‐Coupling Reaction
Authors: Liu Chao , Chen Qing‐Yun 
Published: July 2005

AbstractVarious trifluoromethylated porphyrins can be conveniently synthesized in high yields by the reaction of brominated porphyrins with FSO2CF2COOMe/CuI in the presence of catalytic amounts of Pd2(dba)3·CHCl3/AsPh3. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis of Aliphatic [carbonyl‐11C]Esters Using [11C]Carbon Monoxide
Authors: Itsenko Oleksiy , Kihlberg Tor , Långström Bengt 
Published: July 2005

AbstractAliphatic esters were labelled with a short‐lived radionuclide, 11C with t½ = 20.3 min, at the carbonyl position using [11C]carbon monoxide via rapid (6 min) photoinduced radical‐mediated carbonylation reactions. The esters were prepared from primary, secondary, and tertiary alkyl iodides, and various alcohols, including tert‐butyl alcohol and phenol. The use of strong bases was necessary to achieve good radiochemical yields in short reaction times. Isolated decay‐corrected radiochemical yields were in the range of 40–68 %. For example, methyl hydrogen dodecanoate was labelled at the ester carbonyl in 61 % isolated decay‐corrected radiochemical yield with a specific radioactivity of 158 GBq/μmol within approximately 25 min of the production of [11C]carbon monoxide. Two (13C)substituted esters were synthesised using this method to verify the labelling position. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Differential expression of proteoglycans at central and peripheral nodes of Ranvier
Authors: Melendez‐Vasquez Carmen , Carey David J. , Zanazzi George , Reizes Ofer , Maurel Patrice , Salzer James L. 
Published: July 2005

AbstractThe nodes of Ranvier are regularly spaced gaps between myelin sheaths that are markedly enriched in voltage‐gated sodium channels and associated proteins. Myelinating glia play a key role in promoting node formation, although the requisite glial signals remain poorly understood. In this study, we have examined the expression of glial proteoglycans in the peripheral and central nodes. We report that the heparan sulfate proteoglycan, syndecan‐3, becomes highly enriched with PNS node formation; its ligand, collagen V, is also concentrated at the PNS nodes and at lower levels along the abaxonal membrane. The V1 isoform of versican, a chondroitin sulfate proteoglycan, is also present in the nodal gap. By contrast, CNS nodes are enriched in versican isoform V2, but not syndecan‐3. We have examined the molecular composition of the PNS nodes in syndecan‐3 knockout mice. Nodal components are normally expressed in mice deficient in syndecan‐3, suggesting that it has a nonessential role in the organization of nodes in the adult. These results indicate that the molecular composition and extracellular environment of the PNS and CNS nodes of Ranvier are significantly distinct. © 2005 Wiley‐Liss, Inc.
Simplified intersubject averaging on the cortical surface using SUMA
Authors: Argall Brenna D. , Saad Ziad S. , Beauchamp Michael S. 
Published: July 2005

AbstractTask and group comparisons in functional magnetic resonance imaging (fMRI) studies are often accomplished through the creation of intersubject average activation maps. Compared with traditional volume‐based intersubject averages, averages made using computational models of the cortical surface have the potential to increase statistical power because they reduce intersubject variability in cortical folding patterns. We describe a two‐step method for creating intersubject surface averages. In the first step cortical surface models are created for each subject and the locations of the anterior and posterior commissures (AC and PC) are aligned. In the second step each surface is standardized to contain the same number of nodes with identical indexing. An anatomical average from 28 subjects created using the AC–PC technique showed greater sulcal and gyral definition than the corresponding volume‐based average. When applied to an fMRI dataset, the AC–PC method produced greater maximum, median, and mean t‐statistics in the average activation map than did the volume average and gave a better approximation to the theoretical‐ideal average calculated from individual subjects. The AC–PC method produced average activation maps equivalent to those produced with surface‐averaging methods that use high‐dimensional morphing. In comparison with morphing methods, the AC–PC technique does not require selection of a template brain and does not introduce deformations of sulcal and gyral patterns, allowing for group analysis within the original folded topology of each individual subject. The tools for performing AC–PC surface averaging are implemented and freely available in the SUMA software package. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Hypothesis testing in distributed source models for EEG and MEG data
Authors: Waldorp Lourens J. , Huizenga Hilde M. , Grasman Raoul P.P.P. , Böcker Koen B.E. , Molenaar Peter C.M. 
Published: July 2005

AbstractHypothesis testing in distributed source models for the electro‐ or magnetoencephalogram is generally performed for each voxel separately. Derived from the analysis of functional magnetic resonance imaging data, such a statistical parametric map (SPM) ignores the spatial smoothing in hypothesis testing with distributed source models. For example, when intending to test a single voxel, actually an entire region of voxels is tested simultaneously. Because there are more parameters than observations, typically constraints are employed to arrive at a solution which spatially smooths the solution. If ignored, it can be concluded from the hypothesis test that there is activity at some location where there is none. In addition, an SPM on distributed source models gives the illusion of very high resolution. As an alternative, a multivariate approach is suggested in which a region of interest is tested that is spatially smooth. In simulations with MEG and EEG it is shown that clear hypothesis testing in distributed source models is possible, provided that there is high correspondence between what is intended to be tested and what is actually tested. The approach is also illustrated by an application to data from an experiment measuring visual evoked fields when presenting checkerboard patterns. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Resting anterior cingulate activity and abnormal responses to errors in subjects with elevated depressive symptoms: A 128‐channel EEG study
Authors: Pizzagalli Diego A. , Peccoralo Lauren A. , Davidson Richard J. , Cohen Jonathan D. 
Published: July 2005

AbstractDepression has been associated with dysfunctional executive functions and abnormal activity within the anterior cingulate cortex (ACC), a region critically involved in action regulation. Prior research invites the possibility that executive deficits in depression may arise from abnormal responses to negative feedback or errors, but the underlying neural substrates remain unknown. We hypothesized that abnormal reactions to error would be associated with dysfunctional rostral ACC activity, a region previously implicated in error detection and evaluation of the emotional significance of events. To test this hypothesis, subjects with low and high Beck Depression Inventory (BDI) scores performed an Eriksen Flanker task. To assess whether tonic activity within the rostral ACC predicted post‐error adjustments, 128‐channel resting EEG data were collected before the task and analyzed with low‐resolution electromagnetic tomography (LORETA) using a region‐of‐interest approach. High BDI subjects were uniquely characterized by significantly lower accuracy after incorrect than correct trials. Mirroring the behavioral findings, high BDI subjects had significantly reduced pretask gamma (36.5–44 Hz) current density within the affective (rostral; BA24, BA25, BA32) but not cognitive (dorsal; BA24′, BA32′) ACC subdivision. For low, but not high, BDI subjects pretask gamma within the affective ACC subdivision predicted post‐error adjustments even after controlling for activity within the cognitive ACC subdivision. Abnormal responses to errors may thus arise due to lower activity within regions subserving affective and/or motivational responses to salient cues. Because rostral ACC regions have been implicated in treatment response in depression, our findings provide initial insight into putative mechanisms fostering treatment response. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Word and nonword repetition in bilingual subjects: A PET study
Authors: Klein Denise , Watkins Kate E. , Zatorre Robert J. , Milner Brenda 
Published: July 2005

AbstractLearning a specific skill during childhood may partly determine the functional organization of the adult brain. This hypothesis led us to study brain activation patterns using positron emission tomography (PET), in which we compared word and nonword repetition in 10 right‐handed native English‐speakers (L1) who were proficient in their second language, French (L2), which was learned after the age of 5 years. Regional cerebral blood flow (rCBF) was measured by the H215O intravenous bolus method with intersubject averaging and coregistration of magnetic resonance and PET images. A comparison of CBF changes when repeating words in L2 with those seen when repeating words in (L1) demonstrated that the pattern of CBF was similar across the two conditions, with several significant CBF differences in the vicinity of the left insular cortex, ventral premotor region, and in the striatum. We hypothesize that these regions are activated when subjects are required to repeat known words, showing increased activity when there are increased articulatory demands imposed by speaking L2. Comparisons of nonword repetition in L1 and L2 revealed increased activity for L2 in the left ventral premotor region and in the cerebellum; rCBF increases were also observed in these regions in both L1 and L2 with increased number of syllables and increased articulatory complexity, suggesting a role for these regions in the complex motor control needed for the production of novel sequences. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Activation of the left planum temporale in pitch processing is shaped by language experience
Authors: Xu Yisheng , Gandour Jackson , Talavage Thomas , Wong Donald , Dzemidzic Mario , Tong Yunxia , Li Xiaojian , Lowe Mark 
Published: July 2005

AbstractImplicit, abstract knowledge acquired through language experience can alter cortical processing of complex auditory signals. To isolate prelexical processing of linguistic tones (i.e., pitch variations that convey part of word meaning), a novel design was used in which hybrid stimuli were created by superimposing Thai tones onto Chinese syllables (tonal chimeras) and Chinese tones onto the same syllables (Chinese words). Native speakers of tone languages (Chinese, Thai) underwent fMRI scans as they judged tones from both stimulus sets. In a comparison of native vs. non‐native tones, overlapping activity was identified in the left planum temporale (PT). In this area a double dissociation between language experience and neural representation of pitch occurred such that stronger activity was elicited in response to native as compared to non‐native tones. This finding suggests that cortical processing of pitch information can be shaped by language experience and, moreover, that lateralized PT activation can be driven by top‐down cognitive processing. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Water and the Huisgen Cycloaddition Reaction: A Focus on Polar Contributions to the Transition State in the Reactions of Dicyano(phthalazinium)methanide with Substituted Styrenes and Benzylidene Acetones
Authors: Butler Richard N. , Coyne Anthony G. , Cunningham William J. , Moloney Eamon M. , Burke Luke A. 
Published: July 2005

AbstractSynthetic and kinetic studies on the 1,3‐dipolar cycloaddition reactions of dicyano(phthalazin‐2‐ium‐2‐yl)methanide (1) with some substituted styrenes and ‘benzylidene acetones’ in MeCN and H2O containing 10 mol‐% of MeCN are reported. The kinetic data were supported by theoretical calculations. The major products from styrenes were exo‐2‐aryl‐1,2,3,10b‐tetrahydropyrrolo[2,1‐a]phthalazine‐3,3‐dicarbonitriles 3, and, from ‘benzylidene acetones’, 1‐endo,2‐exo‐2‐acetyl‐1‐aryl‐1,2,3,10b‐tetrahydropyrrolo[2,1‐a]phthalazine‐3,3‐dicarbonitriles 7. There was no indication that the cycloadditon transition states were more polar in the aqueous environment than in MeCN.
Novel Sulfonamide Derivatives as Inhibitors of Histone Deacetylase
Authors: Finn Paul W. , Bandara Morwena , Butcher Chris , Finn Angela , Hollinshead Ruth , Khan Nagma , Law Norman , Murthy Sreenivasa , Romero Rosario , Watkins Clare , Andrianov Victor , Bokaldere Rasma M. , Dikovska Klara , Gailite Vija , Loza Einars , Piskunova Irina , Starchenkov Igor , Vorona Maxim , Kalvinsh Ivars 
Published: July 2005

AbstractInhibition of the enzyme histone deacetylase (HDAC) is emerging as a novel approach to the treatment of cancer. A series of novel sulfonamide derivatives were synthesized and evaluated for their ability to inhibit human HDAC. Compounds were identified which are potent enzyme inhibitors, with IC50 values in the low nanomolar range against enzyme obtained from HeLa cell extracts, and with antiproliferative effects in cell culture. Extensive characterization of the structure–activity relationships of this series identified key requirements for activity. These include the direction of the sulfonamide bond and substitution patterns on the central phenyl ring. The alkyl spacer between the aromatic head group and the sulfonamide functionality also influenced the HDAC inhibitory activity. One of these compounds, m11.1, also designated PXD101, has entered clinical trials for solid tumors and haematological malignancies.
Stereoselective Cyclopropanation of 2‐[(S)‐(4‐Methylphenyl)sulfinyl]cyclopent‐2‐en‐1‐one with Sulfur Ylides and α‐Halo Carbanions. Preliminary Communication
Authors: Mikołajczyk Marian , Midura Wanda H. , Michedkina Elena , Filipczak Agnieszka D. , Wieczorek Michał W. 
Published: July 2005

AbstractThe cyclopropanation of the title compound (S)‐2 with various sulfur ylides has been examined. The reaction with methylenesulfonium ylides gave the corresponding cyclopropanes 4 with low diastereoselectivity. The formation of the second product 5 arising from the subsequent methylenation of the CO group was also observed. A clean cyclopropanation of (S)‐2 took place with ethyl (dimethylsulfanylidene)acetate affording the cyclopropanes 6, with high π‐facial selectivity, but low endo/exo ratio. A high endo/exo selectivity, but low π‐facial selectivity was observed in the reaction of (S)‐2 with (2‐ethoxy‐2‐oxoethyl)(diphenyl)sulfonium tetrafluoroborate. The use of α‐bromoacetate carbanion as the cyclopropanation reagent resulted in the formation of 6 with very high facial and endo/exo‐selectivity. In a proposed explanation of the stereochemical outcome of the cyclopropanations investigated, the ground‐state conformation of the sulfoxide 2 and the transition‐state structure of the initial addition step were taken into account.
A Novel Coupling 1,3‐Dipolar Cycloaddition Sequence as a Three‐Component Approach to Highly Fluorescent Indolizines
Authors: Rotaru Alexandru V. , Druta Ioan D. , Oeser Thomas , Müller Thomas J. J. 
Published: July 2005

AbstractIndolizines 4 and biindolizines 6 can be synthesized in moderate yields in a consecutive one‐pot three‐component process by a coupling/1,3‐dipolar cycloaddition sequence of a (hetero)arenecarbonyl chloride 1, a terminal alkyne 2, and a suitable 1‐(2‐oxoethyl) pyridinium bromide 3 or 5, respectively (Schemes 1 and 2). After the Sonogashira coupling, a [2+3] cycloaddition of the in situ formed pyridinium ylide, an allyl‐type 1,3‐dipole, furnishes a cycloadduct that is instantaneously oxidatively aromatized to give the highly fluorescent indolizine derivatives that were unambiguously characterized by an X‐ray‐structure analysis of compound 4d (Fig. 1). Additionally, fluorescence studies with pyridinyl‐substituted representatives reveal not only that indolizines and biindolizines are highly interesting fluorescence dyes but that their fluorescence color can also be reversibly switched upon altering the pH of the medium.
1,3‐Dipolar Cycloaddition Reactions of Organic Azides with Morpholinobuta‐1,3‐dienes and with an α‐Ethynyl‐enamine
Authors: Brunner Martina , Maas Gerhard , Klärner Frank‐Gerrit 
Published: July 2005

AbstractThe cycloaddition of organic azides with some conjugated enamines of the 2‐amino‐1,3‐diene, 1‐amino‐1,3‐diene, and 2‐aminobut‐1‐en‐3‐yne type is investigated. The 2‐morpholinobuta‐1,3‐diene 1 undergoes regioselective [3+2] cycloaddition with several electrophilic azides RN3 2 (a, R=4‐nitrophenyl; b, R=ethoxycarbonyl; c, R=tosyl; d, R=phenyl) to form 5‐alkenyl‐4,5‐dihydro‐5‐morpholino‐1H‐1,2,3‐triazoles 3 which are transformed into 1,5‐disubstituted 1H‐triazoles 4a,d or α,β‐unsaturated carboximidamide 5 (Scheme 1). The cycloaddition reaction of 4‐[(1E,3Z)‐3‐morpholino‐4‐phenylbuta‐1,3‐dienyl]morpholine (7) with azide 2a occurs at the less‐substituted enamine function and yields the 4‐(1‐morpholino‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 8 (Scheme 2). The 1,3‐dipolar cycloaddition reaction of azides 2a–d with 4‐(1‐methylene‐3‐phenylprop‐2‐ynyl)morpholine (9) is accelerated at high pressure (ca. 7–10 kbar) and gives 1,5‐disubstituted dihydro‐1H‐triazoles 10a,b and 1‐phenyl‐5‐(phenylethynyl)‐1H‐1,2,3‐triazole (11d) in significantly improved yields (Schemes 3 and 4). The formation of 11d is also facilitated in the presence of an equimolar quantity of tBuOH. The three‐component reaction between enamine 9, phenyl azide, and phenol affords the 5‐(2‐phenoxy‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 14d.
Palladium‐Catalyzed Amination of 3,5‐Dihalopyridines – a Convenient Route to New Polyazamacrocycles
Authors: Averin Alexei D. , Ulanovskaya Olesya A. , Fedotenko Ilya A. , Borisenko Anatolii A. , Serebryakova Marina V. , Beletskaya Irina P. 
Published: July 2005

AbstractPd‐Catalyzed amination of 3,5‐dibromo‐ and 3,5‐dichloropyridine (1a and 1b, resp.) with linear polyamines 2 leads to the formation of a new family of pyridine‐containing macrocycles 3 with an ‘exo’‐oriented pyridine N‐atom (Schemes 1 and 2). The dependence of the macrocycle yield on the nature of the halogen atom, the length of the polyamine chain and C/N atom ratio, and the composition of the catalytic system is studied. The synthesis of mono‐ and bis(5‐halopyridin‐3‐yl)‐substituted polyamines 4, 5, 8, 9, and of 3,5‐bis(polyamino)‐substituted pyridines 6 is described (Schemes 3 and 4), and the use of these compounds as intermediates on the way to the macrocycles 7, 16, and 18 with larger cavity (‘cyclodimers’ and ‘cyclotrimers’) is demonstrated (Schemes 5–10).