bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new technique for pet slice orientation and MRI‐PET coregistration
Authors: Grabowski T. J. , Damasio H. , Frank R. , Hichwa R. D. , Boles Ponto L. L. , Watkins G. L. 
Published: December 2004

AbstractWe report and validate a technique for magnetic resonace imaging (MRI) positron emission tomography (PET) coregistration and the optimization of PET slice orientation that enhances and complements existing techniques. The technique depends on an external fiducial system and on software that models the relationship of the PET gantry with respect to a three‐dimensional (3D) MR reconstruction of each subject's brain anatomy. The technique offers the possibility of using individual neuroanatomical information to plan PET activation studies. Estimated 3D errors average 3 mm in [15O]H2O PET activation studies. In‐plane interinjection movement averages less than 1 mm. The resulting MRI‐PET coregistration provides a basis for bringing neuroanatomical information to bear on a number of issues critical for the interpretation of functional imaging studies. © 1995 Wiley‐Liss, Inc.
Neuroanatomical analysis of functional brain images: Validation with retinotopic mapping
Authors: Grabowski T. J. , Damasio H. , Frank R. J. , Brown C. K. , Boles Ponto L. L. , Watkins G. L. , Hichwa R. D. 
Published: December 2004

AbstractThe analysis of functional brain images generated by positron emission tomography (PET) has depended on averaging individual images in a common stereotactic space to improve the signal‐to‐noise ratio in activation maps. Although the precise relationship of stereotactic coordinates to sulcul and gyral anatomy is obscured, these techniques have productively enabled exploratory, pixel‐based analysis of PET images. Coregistered three‐dimensional magnetic resonance (MR) datasets, not widely available at the time PET techniques were pioneered, now make it possible to develop complementary hypothesis‐led analysis techniques that respect individual anatomy and, therefore, allow conclusions in terms of sulcal and gyral anatomy. We report the development of such a technique, involving construction of a local standard space within anatomically‐defined boundaries. We validate the technique with a retinotopic mapping paradigm. In the analysis based on this standard space, regions of activation from the contributing subjects superimpose better than they do when Talairach's transformation is used. This approach also allows conclusions to be drawn specifically about striate cortex, whereas analysis of stereotactically transformed data does not distinguish V1 and V2. This approach is likely to be particularly useful for studying brain‐damaged subjects, to whom a universal stereotactic space cannot be applied. © 1995 Wiley‐Liss, Inc.
Localization of semantic processing using functional magnetic resonance imaging
Authors: Shaywitz Bennett A. , Pugh Kenneth R. , Todd Constable R. , Shaywitz Sally E. , Bronen Richard A. , Fulbright Robert K. , Shankweiler Donald P. , Katz Leonard , Fletcher Jack M. , Skudlarski Pawel , Gore John C. 
Published: December 2004

AbstractThe relationship between the functional components of language and the anatomic foci of their neural systems represents a central issue in cognitive neuroscience. Conflicting results from a number of laboratories using positron emission tomography (PET) imaging techniques have led to a significant controversy over the specific neuroanatomic sites engaged by semantic processing. We report here results of an experiment designed to address this controversy, that is, whether semantic processing activates temporal and/or frontal brain regions. In this experiment we used cognitive tasks that emphasized either semantic or phonological information processing but that were similar on both memory search and responce generation components, together with functional magnetic resonance imaging, to examine the neuroanatomic loci of lexical‐semantic as opposed to phonological processing. We studied nine right‐handed men performing two silent generation tasks: rhyme, and semantic category. The former focuses on word form (phonological information) while the latter focuses on word meaning (semantic information). By “phonological” we mean the process of apprehending the sound structures of language. By “semantic” we mean information about the word's contextually specified meanings. Semantic processing makes demands on, and activates widespread areas within, brain including the inferior frontal regions bilaterally and the left posterior temporal region. Phonological processing engages a more restricted neuroanatomic assembly involving primarily anterior left temporal lobe sites. © 1995 Wiley‐Liss, Inc.
Identification of early visual evoked potential generators by retinotopic and topographic analyses
Authors: Clark Vincent P. , Fan Silu , Hillyard Steven A. 
Published: December 2004

AbstractThis study investigated the cortical sources of the early (50‐250 ms) components of the pattern‐onset visual evoked potential (VEP). VEPs were recorded in response to a small circular checkerboard stimulus that was flashed over a range of visual field positions. Temporally and spatially overlapping VEP components were distinguished by differences in retinotopic sensitivity and scalp topography, and by inverse dipole modeling. The C1 component (50‐80 ms) was found to change its polarity and topography systematically as a function of stimulus position in a manner consistent with the retinotopic organization of the striate cortex. The P1 component (comprised of the P75 and P100 subcomponents) had a time course that overlapped the C1 but could be distinguished from the C1 by its differing topography and reduced sensitivity to stimulus position. The P1 generators were localized to the lateral extrastriate cortex. Inverse dipole models were consistent with these striate and extrastriate source locations for the C1 and P1, respectively. The N1 component (120‐180 ms) was found to originate from several spatially distinct generators that differed in their retinotopic organization. © 1995 Wiley‐Liss, Inc.
Etudes sur les matières végétales volatiles XXIV. Composition de l'huile essentielle et du résinoïde de livèche (Levisticum officinale Koch)
Authors: Naves Y. R. 
Published: December 2004

AbstractL'essence de raciune de livèche contient une forte proportion (environ 70%) de dérivés du phtalide parmi lesquels ont été décelés des n‐butylidène‐phtalides, le n‐butyl‐phtalide, l'anhydride sédanonique. La présence de n‐butyl‐dihydro‐phtalides ou de n‐butyl‐tétrahydro‐phtalides est vraisemblable.
Notice sur les variations de potentiel de l'électrode d'ozone et de l'électrode d'oxygène sous l'influence des radiations ultra‐violettes
Authors: Briner E. , Yalda A. 
Published: December 2004

AbstractL'action des radiations ultra‐violettes diminue d'une manière marquée le potentiel de l'électrode d'ozone et accroît faiblement le potentiel de l'électrode d'oxygène.
Über die Cholin‐esterase des Gehirns und der Erythrocyten. zugleich 3. Mitteilung über die Beeinflussung von Fermentreaktionen durch Chemotherapeutica und Pharmaka
Authors: Zeller Ernst Albert , Bissegger Alfred 
Published: December 2004

Abstract1. Die Serum‐ChE des Menschen wird durch Percain, Irgamid und Isopropyl‐antipyrin stark, die ChE von menschlichem Gehirn und Erythrocyten werden nur schwach gehemmt. Morphin hemmt alle drei ChE ungefähr gleich stark, Coffein nur die Serum‐ChE.
Metal Complexes with Macrocyclic Ligands. X. On the metal complexation kinetics of two N4‐macrocycles containing a pyridine ring
Authors: Schultz‐Grunow Philipp , Kaden Thomas A. 
Published: December 2004

AbstractThe complexation kinetics of the two macrocycles 1 and 2 with Co2+, Ni2+, Cu2+ and Zn2+ have been measured by pH‐stat techniques. The rates are first order in metal and ligand concentration and depend upon the pH. This results from the different reactivities of the various protonated species of the macrocyclic tetraamines. The resolved rate constants are given in Table 2.In comparison with other 14‐membered cyclic aliphatic tetraazasystems 1 and 2 react more slowly with metal ions. This might be a consequence of the more rigid structure induced by the pyridine ring.
Inhaltsstoffe des Osmanthus‐Absolues. 4. Mitteilung: Megastigma‐5, 7 (E), 9‐trien‐4‐on und Megastigma‐5, 8 (E)‐dien‐4‐on
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

Constituents of Osmanthus Absolute, 4th Communication. Megastigma‐5, 7 (E), 9‐triene‐4‐one and Megastigma‐5, 8 (E)‐diene‐4‐oneIn continuation of our communications on constituents of Osmanthus absolute, we now report on the occurrence of the two title compounds 1 and 2a in this natural substrate (0.01‐0.02% each). Their structures were confirmed by synthesis starting from β‐ionone via the common intermediate 4‐oxo‐β‐ionol (9). Some further minor components bearing corresponding structural features are tabulated in view of possible biogenetic pathways leading to 1 or 2a, respectively.In order to clarify the olfactory behaviour, we also synthesized some analogous derivatives in the irone series, these substances being not yet found in nature.
Competing Fragmentation, Substitution and Elimination in the Solvolysis of Alkylated 3‐Chloropropanols and their Ethers. Fragmentation reactions no. 28
Authors: Fischer Walter , Grob Cyril A. 
Published: December 2004

AbstractThe unstrained 3‐chloroalcohols 1a, 2a and 3a do not undergo solvolytic fragmentation in neutral and weakly acidic 80% ethanol, only substitution and elimination products being formed by the limiting SN1‐E1 mechanisms. This also applies to the corresponding ethers 1b and 3b. Addition of sodium hydroxide causes the observed rate constants for the 3‐chloroalcohols to rise steeply by factors of at least 103 to 105. These level off at higher base concentrations due to an opposing ionic strength effect. Whereas 3a fragments quantitatively in the presence of base, 1a and 2a fragment in competition with elimination to the Δ3‐olefins 9a and 10, respectively. 2a also yields 2% of the oxetane 6b.These results support a concerted base‐induced fragmentation mechanism which competes with intramolecular base‐induced elimination (Ei) in the case of the acyclic chloroalcohols 1a and 2a. The formation of small amounts of the oxetane 6b from 2a is attributed to intramolecular nucleophilic substitution at the tertiary carbon atom.
Investigation of the Head‐Space of Roasted Meat II. Synthesis of substituted 2, 4, 5‐trithia‐hexanes
Authors: Dubs Paul , Stüssi Rita 
Published: December 2004

AbstractSubstituted 2, 4, 5‐trithiahexanes 1, a class of substances recently found in roasted meat, have been synthesized via two different routes.
Clark‐ähnlicher Wasserstoffdetektor
Authors: Grüniger Hans‐Rudolf , Sulzberger Barbara , Calzaferri Gion 
Published: December 2004

Clark‐like Hydrogen DetectorA quantitative hydrogen detector, similar to the Clark oxygen electrode, has been proposed by Green et al. [1] in 1967. Such a detector gives a signal which is directly proportional to the hydrogen partial pressure without consuming any hydrogen itself. We have taken up the proposal of Green et al., and have realized a very sensitive and under many circumstances also a selective detector, which is easy to handle and which can be used in gaseous phase as well as in aqueous solution. Sensitivity of 0.1 Torr or even better can be achieved. The main differences to the Clark electrode are that a platinized platinum electrode has to be used instead of a blank platinum electrode and that a more positive potential has to be applied. We give a detailed description of the construction and the handling of the Clark‐like hydrogen detector.
Totalsynthese von (+)‐D‐Homo‐19‐nortestosteron
Authors: Gutzwiller Jürg , Labler Ludvik , Meier Werner , Fürst Andor , Eder Ulrich , Sauer Gerhard , Wiechert Rudolf 
Published: December 2004

Total Synthesis of (+)‐D‐Homo‐19‐nortestosteroneA novel total synthesis of (+)‐D‐homo‐19‐nortestosterone (2) is described starting from (4a S, 5S)‐5‐(t‐butoxy)‐4a‐methyl‐4, 4a, 5, 6, 7, 7‐hexahydro‐3 H‐naphthalen‐2‐one (3) as a chiral building block for the rings C and D. The key step involves combining of the derived reactive one‐carbon atom adducts 5 and 6 with the β‐keto ester 16, a synthon for the rings A and B, to give the Δ9‐4, 5‐secosteroid 21. 21 was readily transformed to the title compound 2 by hydrogenation and subsequent ring closure. Hydrogenation of the derived 3, 5‐dione 22 followed by base‐catalyzed cyclization gave the 17a‐t‐butoxy compound 27 and the 9β, 10α‐D‐homosteroid 29 as by‐product.
Synthesis and properties of chiral macrotricyclic ligands. Complexation and transport of chiral molecular cations and anions
Authors: Lehn Jean‐Marie , Simon Jacques , Moradpour Alexandre 
Published: December 2004

AbstractThe optically active macrotricyclic cryptands1and2, containing the binaphthyl group as chiral unit, have been synthesized. These compounds contain lateral cavities which may serve as anchoring sites for polar groups of the substrates and a central, chiral cavity large enough for including more or les completely the bulk of a molecular ion. Their complexation properties towards molecular ions give evidence for the occurrence of two types of processes: (a) direct complexation of primary ammonium cations, like phenylethyl ammonium chloride, occurs with either1or2; (b) cascade binding, involving first complexation of an alkali cation followed by pairing with a molecular anion, takes place with2. Process (b) may be considered as ametallo‐receptormodel system where binding of an anionic substrate is dependent on initial binding of a cation. In both cases (a) and (b) weak resolution of chiral racemic substrates has been observed by extraction and transport (through a bulk liquid membrane) experiments. This indicates that in the complex the bulk of the substrate should be located close to the chiral unit and therefore more or less in the central cavity. In the case of cryptand2, the resolution achieved for the (±)‐mandelate anion is markedly affected by the nature of the complexed cation.
Synthese von 1, 3, 4‐Oxadiazolen und 4, 5‐Dihydro‐1, 2, 4‐triazinen aus 3‐Dimethylamino‐2, 2‐dimethyl‐2 H‐azirin und Carbohydraziden
Authors: Link Helmut 
Published: December 2004

Synthesis of 1,3,4‐Oxadiazoles and 4,5‐Dihydro‐l,2,4‐triazines from 3‐Dimethylamino‐2,2‐dimethyl‐2 Hazirine and Carbohydrazides3‐Dimethylamino‐2, 2‐dimethyl‐2 H‐azirine (1) reacts with aromatic carbohydrazides to give 2‐(1‐amino‐1‐methylethyl)‐5‐aryl‐1, 3, 4‐oxadiazoles (7, 10, 11). With ethyl carbazate the azirine 1 forms the aminoester 15, which is easily cyclized to the 4, 5‐dihydro‐1, 2, 4‐triazin‐3 (2H)‐one 16. From the reaction of 1 with oxamohydrazide (17) and oxalodihydrazide 19 the 4, 5‐dihydro‐1, 2, 4‐triazin‐3‐carboxamide 18 and the symmetric compound 20, respectively, have been isolated. Reactions supporting the structures of the new compounds are described.
«Push‐Pull»‐Acetylene als Hilfsmittel zur Synthese von Amiden
Authors: Neuenschwander Markus , Lienhard Ulrich , Fahrni Hans‐Peter , Hurni Beat 
Published: December 2004

Amide Synthesis by Means of ‘Push‐Pull’‐Acetylenes‘Push‐Pull’‐acetylenes react easily with carbon acids, Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one‐pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, ‘push‐pull’‐acetylenes could be excellent reagents for peptide synthesis.
«Push‐Pull»‐Acetylene als Hilfsmittel zur Synthese von Peptiden
Authors: Neuenschwander Markus , Fahrni Hans‐Peter , Lienhard Ulrich 
Published: December 2004

Peptide synthesis by Means of ‘Push‐Pull’‐Acetylenes‘Push‐pull’‐acetylenes 1 are excellent reagents for peptide synthesis: Addition of ‘push‐pull’‐acetylenes to solutions of N‐protected amino acids (or vice versa) gives enol esters 5, which react selectively with the amino function of a second amino acid. In this way serine, tyrosine, 4‐hydroxyproline, cysteine as well as histidine are linked to form dipeptide esters without protection of the second functional group (OH, SH or NH). The amount of racemization is very low. Similarly tri‐ as well as tetrapeptides are available. The versatility of the reaction is discussed.
Über die Synthese von 1‐Aryl‐und 1‐Alkyl‐2, 3‐dimethyl‐chinoxalinium‐perchloraten. 2. Mitteilung. Synthese und 1H‐NMR.‐Spektren von 2,3‐Dimethyl‐1‐phenyl‐6‐X‐chinoxalinium‐perchloraten
Authors: Schelz Dieter 
Published: December 2004

On the Synthesis of 1‐Aryl‐ and‐1‐Alkyl‐2, 3‐dimethyl‐quinoxalinium Perchlorates. 2nd Communication1. Mitt.: [1].

. Synthesis and
1
H‐NMR.
Spectra of 2, 3‐Dimethyl‐1‐phenyl‐6‐X‐quinoxlinium Perchlorates
The synthesis of the title compounds (5) which have been useful as precursors for a lot of conventional and new‐type dyes [2‐8] has yet been limited to examples with XH [2] [3] [11] [15] and with electron‐donating [4] [12] or at best slightly electron‐accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron‐accepting substituents: N‐monosubstituted o‐phenylendiamines 4, were condensed with 2, 3‐butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products ‐ mostly substituted at position 6 of the quinoxalinium ring ‐ are chracterized by 1H‐NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6. Correlations of chemical shifts with Hammett's σp [18] are given by equations (1)‐(5).
Allylic Reactions of Benzocyclopropenes. Discrimination of halogen substituents in 1, 1‐Dihalogenobenzocyclopropenes
Authors: Müller Paul , Etienne Robert , Pfyffer Jean , Pineda Nelson , Schipoff Michel 
Published: December 2004

AbstractReaction of 1, 1‐dichloro‐2, 5‐diphenylbenzocyclopropene (10a) with 1 equiv. of silver fluoride yields 1‐chloro‐1‐fluoro‐2, 5‐diphenylbenzocyclopropene (10c). Both 10a and 10c react with excess silver fluoride to give the difluoro compound 10b. Both 10b and 10c are also prepared via cyclo‐additions of 1, 2‐dichloro‐3, 3‐difluorocyclopropene (14) or 1, 2, 3‐flurocyclopropene (13) with diphenylbutadiene and subsequent aromatization with base. Similarly. 1‐chloro‐1‐fluorobenzocyclopropene (16) is accessible from butadiene and 13.
Studies on Radical Cations I. Molecular and electronic structure of [3]radialene cation produced by γ‐irradiation in condensed phase
Authors: Bally Thomas , Haselbach Edwin , Lanyiova Zuzana , Baertschi Peter 
Published: December 2004

Abstractγ‐Irradiation of tris (methylidene)‐cyclopropane (‘[3]radialene’) 1 in a rigid electron scavenging matrix (butylchoride/i‐pentane, 1:1) at 77 K leads to formation of its molecular cation 1+. Slight softening of the matrix by a temperature increase of 3–5 K results in formation of a newly absorbing species, tentatively assigned arising from structrral relaxation of 1+ by π‐bond rotation: magnified image
2‐Stannyl‐1, 3‐dithiane Herstellung, Sn/Li‐Transmetallierung und Verwendung für Cyclisierungen
Authors: Seebach Dieter , Willert Ingrid , Beck Albert K. , Gröbel Bengt‐Thomas 
Published: December 2004

2‐Stannyl‐1,3‐dithianes. Preparation, Sn/Li‐Transmetallation, and Use for CyclizationsIn order to test the possibility of generating nucleophilic 2‐lithio‐1, 3‐dithiane centers in the presence of electrophilic groups in the same molecule, the stannylated dithianes 1‐3 were prepared or generated. Solutions of the lithio derivatives 2a and 2b could either be obtained by metallation of 1 with lithiumdiisopropylamide (LDA) or by transmetallation of 3 with alkyllithium reagents. Alkylations of 2 led to the alkyl‐stannyl‐dithianes 4‐7. Additions of the trimethylstannylated lithiodithiane 2a to aldehydes and ketones at low temperature led ‐ after hydrolysis ‐ to the adduct alcohols 8; warming up to room temperature before hydrolysis furnished keten thioacetals 9 only with acetone (→ 9b) and cyclohexanone (→ 9c) as carbonyl component, while still the simple adducts 8a and 8d were isolated with benzaldehyde and cyclohexenone, respectively. Methyl benzoate and benzoic acid anhydride reacted with 2a to produce the tin‐free derivatives 12 and 14, respectively.It is shown that the Sn/Li‐exchange at the 2‐position of dithianes 4‐7, 15 and 16 takes place within minutes at −78°, whereas H/Li‐metallation does not occur at all at this temperature. In situ preparation of the cyclization products 17‐19 from halo‐epoxides is described. The overall yields of Sn/Li‐exchange (3 → 2), epoxyalkylation (2 → 15 and 16, repectively), Sn/Li‐exchange in 15and 16, cyclization (→ 17–19) are twice as high (up to 80%) with the tributylin than with the trimethyltin derivatives. The intramolecular 1, 3 nucleophilic reaction 20a → 17 is complete within 5 min at −78°. The total yields of cyclization products by the tin route (3b → 16 → 20b → 18 + 19) and by direct metallation (1, 3‐dithiane →21b → 20b → 18 + 19) are 63 and 30%, respectively.
An Efficient Synthesis of Methyl (±)‐Jasmonate and (Z)‐Jasmone
Authors: Näf Ferdinand , Decorzant René 
Published: December 2004

AbstractAn efficient synthesis of methyl (±)‐jasmonate and (Z)‐jasmone is described. The Key step is a phase‐transfer reaction between cyclopentane (9) and 1, 4‐dibromo‐2‐pentene (6a/b) to give the spiro [2.4]hepten‐4‐ones 4a and 4b.
Claisen‐Umlagerung von 2‐Propinyl‐(3‐pyridyl)‐und Allyl‐(3‐pyridyl)äthern
Authors: Bruhn Jens , Zsindely Janos , Schmid Hans , Fráter György 
Published: December 2004

Claisen Rearrangement of 2‐Propinyl (3‐Pyridyl) and Allyl (3‐Pyridyl) EthersVerbindungen vom Typ 1 werden mit Ausnahme von 17 und 25 als Äther benannt. Der systematische Name von 1 ist: 3‐(2‐Propinyl)oxy‐pyridin.
2‐Propinyl (3‐pyridyl) ether (1), synthesized from the corresponding 3‐pyridinol, was heated in DMF or decane at 208° in a sealed tube. In this way the furopyridines 2 and 3 were formed, and furthermore the pyranopyridine 4 if decane was used as solvent (Scheme 1). The same reactions took place with (2‐methyl‐3‐pyridyl) 2‐propinyl ether (14). In DMF only 15, and in decane 16 as well as 15 were formed (Scheme 3). The rearrangement of the pyridine derivative 17, which is substituted in both O‐positions to the ether moiety, gave in both DMF and decane the diastereoisomeric tetracyclic compounds 18 and 19. The same kind of reaction took place with 25 (Scheme 4).In the thermolysis of the allyl 3‐pyridyl ether (27) cyclization was observed, too. The isolated product has the structure of the dihydrofuropyridine 28 (Scheme 6). The substituted allyl 3‐pyridyl ether 30 reacted in the same way to the dihydrofuropyridine 31 (Scheme 6).
Cob(I)alamin als Katalysator. 1. Mitteilung. Reduktion von gesättigten Nitrilen in wässeriger Lösung
Authors: Fischli Albert 
Published: December 2004

Co(I)alamin as Catalyst. 1. Communication. Reduction of Saturated Nitriles in Aqueous SolutionUsing cob(I)alamin as homogeneous catalyst in the presence of aqueous acetic acid saturated nitriles 5a–m are reduced to the corresponding aldehydes 6a–m in good yields. A possible reaction mechanism for this reduction is discussed.
Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1‐ (3′‐O‐Phosphoryl‐2′‐deoxy‐β ‐D‐ribofuranosyl)‐2(1H)‐pyridone‐(3′‐5′)‐1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐2 (1H)‐pyridone
Authors: Cerletti Nico , Séquin Urs , Tamm Christoph , Zürcher Werner 
Published: December 2004

AbstractThe dinucleoside phosphate ΠdpΠd (4) was synthesized from the monomers 1‐(5′‐O‐monomethoxytrityl ‐ 2′ ‐ deoxy ‐ β ‐ D ‐ ribofuranosyl) ‐ 2 (1 H) ‐ pyridone ((MeOTr) Πd, 2) and 1‐(5′‐O‐phosphoryl‐3′‐O‐acetyl‐2′‐deoxy‐β‐D‐ribofuranosyl)‐(1H)‐pyridone (pΠd(Ac), 3). Its 6.4% hyperchromicity and an analysis of the 1H‐NMR. spectra indicate that the conformation and the base‐base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.