bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amphiphilic and Mesogenic Carbohydrates, 8. – Liquid Crystalline Alkyl 2‐Deoxy‐2‐fluoro‐1‐thioglycopyranosides
Authors: Miethchen Ralf , Kowalek Heike , Niemanna Angela , Diele Siegmar , Schick Christoph 
Published: July 2007

AbstractThe homologous series of the amphiphilic alkyl 2‐deoxy‐2‐fluoro‐1‐thio‐α‐D‐glucopyranosides 5a–e and alkyl 2‐deoxy‐2‐fluoro‐1‐thio‐α‐D‐mannopyranosides 9a–e were prepared from the 2‐deoxy‐2‐fluoro‐D‐glycosyl fluorides 1 and 6, respectively. Their liquid crystalline properties were investigated by polarising microscopy, DSC measurements, and X‐ray measurements. The fluorine‐containing thioglycosides 5a–e as well as 9a–e form enantiotropic mesophases of the type smectic A. The effects of F for OH and S for O substitution are discussed with reference to the homologous alkyl‐1‐thio‐α‐D‐glucopyranosides 10 and alkyl 2‐deoxy‐2‐fluoro‐α‐D‐glucopyranosides 11.
Glycosyl Imidates, 78. An Efficient Synthesis of Galactinol and Isogalacatinol
Authors: Mayer Thomas G. , Schmidt Richard R. 
Published: July 2007

Abstract2:3,4:5‐Di‐O‐cyclohexylidene‐D‐/L‐myo‐inositol (2) could be readily converted into 6‐O‐ and 1‐O‐unprotected L‐ and D‐myo‐inositol derivatives L‐ and D‐4 and L‐ and D‐6, respectively. Their reaction with trichloroacetimidate 7 as galactosyl donor in the presence of tin(II) trifluoromethanesulfonate as catalyst afforded the desired α(1–6)‐ and α(1–1)‐connected galactopyranosides 8, 11 and 12. Compound 11 could be readily deprotected to afford target molecule (galactinol) 1 in high overall yield; from 12, the diastereoisomer 13 was obtained.
Chiral Pyridinophanes as Hydrogen‐Bonding Supramolecular Building Blocks
Authors: de la Moya Cerero Santiago , Böhme Marc , Nieger Martin , Vögtle Fritz 
Published: July 2007

AbstractHydrogen‐donor and hydrogen‐acceptor substituted chiral cyclophanes with a [2](1,3)benzeno[2](3,5)pyridinophane framework have been synthesized, enantiomerically separated, and analysed by circular dichroism (CD). X‐ray structure determination and CD analyses show that these cyclophanes are able to act as hydrogen‐bonding donor/acceptor building blocks for the design of chiral supramolecular aggregates with suitable complementary partners. Starting from the pyridinophane N‐oxide 4, selective reactions lead to the new chiral pyridinophanes 5–7 in high yields. The X‐ray structure analysis of the pyridinophane‐2‐carbonitrile 5 reveals a multilayered herringbone structure as it forms dimeric aggregates. The CD analysis of the host 7 with the complementary guest molecules melamine and cyanuric acid elucidates the formation of supramolecular complexes in solution.
N‐Methyl Derivatives of Highly Substituted Porphyrins – the Combined Influence of Both Core and Peripheral Substitution on the Porphyrin Conformation
Authors: Senge Mathias O. , Kalisch Werner W. , Runge Steffen 
Published: July 2007

AbstractN‐Methylation of the peripherally highly substituted octaethyltetraphenylporphyrin (1) with either methyl iodide or methyl triflate gave the respective mono‐, di‐, tri‐ and tetra‐N‐methylated derivatives. Use of methyl triflate under carfully controlled conditions often gave the N‐methylporphyrins in quantitative yield. The N‐methylporphyrins possess both core and peripheral steric strain and are good candidates for the study of the combined conformational effect of such substituent patterns. Introduction of successively more N‐methyl groups leads to a stepwise increase in the bathochromic shift of the bands by about 10–15 nm for each substitution. Crystal structure determinations of 11 and 12 showed that these molecules are indeed severely distorted and they exhibit degrees of nonplanarity which significantly exceed those observed for nonmethylated, dodecasubstituted nonplanar porphyrins and for 22,24‐dihydroporphyrin dications. After methylation of meso‐tetraalkylporphyrins 4–7 with methyl triflate only the respective N‐methylated porphyrins 14–17 could be recovered. Use of the extremely ruffled porphyrin 8 led to formation of a 5,21,22,23,24‐pentamethylated porphyrin cation with phlorin structure. Additionally, structural analysis of a cis‐21,22‐dimethyloctaethylporphyrin showed the first example of a porphyrin cation 20 with almost complete localization of the conformational distortion in the porphyrin half bearing the two N‐methyl groups.
Fluoride‐ and Base‐Induced Chemiluminescence (CIEEL) of a Bifunctional Spiroacridane‐Substituted Dioxetane
Authors: Adam Waldemar , Reinhardt Dirk 
Published: July 2007

AbstractThe intramolecular chemically initiated electron‐exchange luminescence (CIEEL) of the novel bifunctional dioxetane 2b was studied. By selective chemical triggering, two different functionalities, namely either a phenoxy (ArO−) or an amide (Ar2N−) ion electron donor, were released, dependent on the type of triggering agent used (either base or fluoride ions). From the CIEEL quantum yields (ΦCIEEL) for the triggered chemiluminescence and the fluorescence efficiencies (ΦFl) of the corresponding phenolate (7) and amide (5) emitters the singlet‐excitation yields (ΦS) were estimated. Due to the weak fluorescence emission and the low excitation propensity, the triggerable bifunctional dioxetane 2b constitutes an inefficient CIEEL system. For comparison, the activation parameters (EA, lg A, ΔH≠, ΔS≠) of the direct chemiluminescence in the thermal decomposition of the dioxetane 2a were determined by standard isothermal kinetic methods.
Galacturonic Acid Derivatives, IX. Regioselective Enzymatic Acetyl Ester Hydrolysis of D‐Galacturonic Acid Derivatives and Related Reactions
Authors: Vogel Christian , Kramer Sven , Ott Andrej‐Jakob 
Published: July 2007

AbstractA number of D‐galacturonic acid derivatives (1, 3, 7 and 9) have been selectively deacetylated in enzyme‐catalyzed reactions. The 2‐O‐acetyl groups were selectively hydrolyzed from 2,3,4‐tri‐O‐acetyl‐β‐D‐galactopyranurono‐6,1‐lactone (1), and methyl [methyl (3) and benzyl (7) 2,3,4‐tri‐O‐acetyl‐β‐D‐galactopyranosid]uronates, affording the specifically deacetylated products in good to excellent yields. The methyl 1,2,3,4‐tetra‐O‐acetyl‐α‐D‐galactopyranuronate (9) was hydrolyzed at the anomeric position in 48% yield using the acylase from Aspergillus melleus (E1), whereas the lipases from wheat germ (E5 and E7) catalyzed the selective cleavage of the acetyl groups in both the 1‐ and 2‐O‐positions, furnishing the methyl 3,4‐di‐O‐acetyl‐D‐galactopyranuronate (12) in 46% isolated yield. The latter compound was obtained in nearly quantitative yield by selective enzymatic deacetylation at the 2‐O‐position of 7, followed by hydrogenolytic cleavage of the anomeric O‐benzyl group. Isopropylidenation of 12 furnished the hitherto unknown methyl 3,4‐di‐O‐acetyl‐1,2‐O‐isopropylidene‐α‐D‐galactopyranuronate (13).
Synthesis and Self‐Association of First‐Generation 1,3,4‐Oxadiazole‐Containing Dendrimers
Authors: Kraft Arno 
Published: July 2007

AbstractTwo 1,3,4‐oxadiazole‐containing dendrimers, 14 and 15, have been prepared employing a palladium‐catalyzed carbonylation reaction as the key step of the synthesis. In order to shorten the reaction sequence, a new oxadiazole synthesis has been developed based on the coupling of aryl iodides with aryl tetrazoles in the presence of a Pd(0) catalyst and carbon monoxide, and has been applied to the preparation of dendrimer 14. Both new dendrimers are highly soluble in chlorinated solvents, but 14, with fewer solubilizing tert‐butyl groups at its periphery, self‐associates in solution by π‐π interactions and possibly due to solvophobic effects. Considerable upfield shifts of the 1H‐NMR signals of the protons in the centre of the molecule indicate the formation of π‐stacks in solution. Vapour‐pressure osmometry studies allow a degree of association of ⩾3 to be estimated.
Synthesis and Conformational Studies of Novel Calixarene‐Analogous Macrocyclic [3.1.1]Metacyclophanes
Authors: Yamato Takehiko , Doamekpor Louis Korbla , Tsuzuki Hirohisa 
Published: July 2007

AbstractHydroxy[3.1.1]metacyclophane 4c, which is regarded as an unsymmetric or uncomplete “homocalixarene” bearing a propane bridge, has been synthesized using Nafion‐H catalyzed cyclobenzylation. A novel “pendulum” type motion steered by intramolecular hydrogen bonding has been observed Demethylation of compound 4c with BBr3 in methylene dichloride was carried out at room temperature for 3 h to afford the dihydroxy[3.1.1]metacyclophane 4b in 74% yield along with the triol 4a in 25% yield. Triol 4a was tri‐O‐alkylated with methyl iodide in the presence of NaH to yield partial‐cone conformer 4d in quantitative yield. Similarly, a significant amount of partial‐cone conformer 5 results in the case of O‐alkylation of 4a with N,N‐diethylchloroacetamide. 1H‐NMR titration of partial‐cone amide 5 with NaSCN clearly demonstrates that a 1:1 complex is formed which is stable on the NMR time scale.
New Electron Donor‐Acceptor Compounds, 51. [3](N,N′)‐1,8;4,5‐Naphthalenetetracarboxdiimido‐ [3](2,7)Pyrenophane and Its [4,4]Cyclophane Homologue
Authors: Staab Heinz A. , Zhang De‐Quing , Krieger Claus 
Published: July 2007

AbstractElectron donor‐acceptor cyclophanes 1 and 2, consisting of pyrene as the donor component and 1,8;4,5‐naphthalenete‐tracarboxdiimide as the acceptor component fixed by methylene chains in parallel face‐to‐face orientations, have been synthesized. The structures, based on an X‐ray analysis of 1 and on spectroscopic properties, are discussed with reference to intramolecular charge‐transfer interactions and are compared to those of the related excimer models [3.3]‐ and [4.4]pyrenophanes 3 and 4.
Complexation Properties of Preorganized Receptor Molecules for Large, Neutral Guests
Authors: Higler Irene , Verboom Willem , van Veggel Frank C. J. M. , de Jong Feike , Reinhoudt David N. 
Published: July 2007

AbstractReceptor molecules with a preorganized cavity were synthesized by combining two resorcin[4]arene and one calix[4]‐arene building block. Based on predictions from a computational study which matches hosts and guests, several steroids, sugar derivatives, and alkaloids were selected for complexation studies. Experimentally the complexation of such guests by these receptor molecules was proven by 1H‐NMR spectroscopy (association constants of 1.0−6.0 × 102 M−1 in CDCl3). One of these receptors with four hydroxyl groups forms a dimeric capsule (Kdimer = 11 M−1 in CDCl3). Evidence for this dimerization comes from 1H‐NMR, FAB MS spectroscopy, and molecular mechanics and dynamics calculations.
Chemistry of the Ginkgolides, VIII – Synthesis and Crystal Structure of a Dimeric 14,15,16‐Trinorginkgolide Derivative
Authors: Weinges Klaus , Schick Hartmut , Irngartinger Hermann , Oeser Thomas 
Published: July 2007

AbstractTreatment of the enol acetate 3‐acetoxy‐10‐methoxy‐methoxy‐2,3‐didehydro‐14,15,16‐trinorginkgolide[2] (2) with potassium osmate/N‐methylmorpholine N‐oxide in acetone/acetic acid solution did not yield the expected 2‐hydroxy‐3‐oxo derivative 3, but the dimeric ginkgolide (2S,2′S,3R,3′R)‐bis(10‐methoxymethoxy‐14,15,16‐trinorginkgolido)[2,3‐c;2′,3′‐e]‐1″,4″‐dioxan‐3,3′‐diol (4a). By acid hydrolysis, 4a was converted to the MOM‐deprotected dimeric product 4b. The structure of 4a was elucidated by crystal structure analysis.
Ion Pair Amphiphiles from Sodium Dodecyl Sulfate and Ammonium Amphiphiles Carrying Functionalized Azobenzene Units
Authors: Nieuwkerk Armanda C. , Marcelis Antonius T. M. , Koudijs Arie , Sudhölter Ernst J. R. 
Published: July 2007

AbstractNew ammonium amphiphiles having a N,N‐dimethyl‐N‐hydroxyethylammonium headgroup and various azobenzene mesogenic units connected by a decyl or dodecyl spacer have been synthesized. The azobenzene unit is functionalized at the 4‐position with a cyano, methoxy or fluoro substituent. For the cyano‐substituted amphotropes and the fluoro compound with a dodecyl spacer a smectic phase is formed as was observed by differential scanning calorimetry and polarization microscopy. Complexation with sodium dodecyl sulfate, SDS, in a 1:1 molar ratio induces the formation of a smectic phase for the compounds with a decyl spacer. The compounds with a dodecyl spacer showed rather complex behavior attributed to different crystal morphologies. The ammonium amphotropes form aggregates in water when heated above their Krafft temperature. However, these aggregates are not stable and crystallize upon cooling. The ion pair amphiphiles with SDS as second component form vesicles in water as observed by optical and electron microscopy. The observed blue shift in the UV absorption maximum of the amphotropes upon addition of SDS indicates π–π stacking between mesogenic units resulting from aggregation.
An Enantiodivergent Synthesis of Both Enantiomers of the Macrocyclic Lactone Curvularin
Authors: Bracher Franz , Schulte Brigitte 
Published: July 2007

AbstractThe macrocyclic lactone (S)‐curvularin (10) and its enantiomer ent‐10 were prepared in an enantiodivergent manner from (S)‐methyl 7‐hydroxyoctanoate (4), which was easily obtained on two different ways. Esterification of 4 under either retention or inversion of the chiral centre gave the enantiomeric diesters 7 and ent‐7. Chemoselective cleavage of the methyl ester groups of these diesters followed by intramolecular acylation and O‐debenzylation gave the two enantiomers of curvularin.
Synthesis and Stereochemistry of Some 1,3‐Dioxane Diacetals of o‐Phthaldialdehyde
Authors: Grosu Ion , Mager Sorin , Plé Gerard , Plé Nelly , Toscano Alfredo , Mesaros Eugen , Martinez Roberto 
Published: July 2007

AbstractThe stereochemistry of some diacetals of o‐phthaldialdehyde with 2‐substituted‐1,3‐propanediols was studied using NMR spectroscopy and the solid‐state molecular structure of one compound established by single‐crystal X‐ray diffractometry. The cis and trans isomers of some diacids and diesters, produced as derivatives bearing the desired substituents in the 5 and 5′ positions of the heterocycles, have been separated by preparative TLC and identified by their NMR spectra.
O‐Glycoside Synthesis with Glycosyl Iodides under Neutral Conditions in 1 M LiClO4 in CH2Cl2
Authors: Schmid Uschi , Waldmann Herbert 
Published: July 2007

AbstractGlycosyl phosphates, imidates, trifluoroacetates, chlorides, and bromides are converted into the respective glycosyl iodides by treatment with LiI or NaI in 1 M solutions of LiClO4 in CH2Cl2. Under these neutral conditions the reactive glycosyl iodides are activated, and react with different glycosyl acceptors to give O‐glycosides in moderate yields, with the α‐anomers predominating. The glycosylation reactions most probably proceed by the initial formation of β‐configured glycosyl iodides from the α‐configured precursors, and subsequent attack of the glycosyl acceptor on the equatorial iodide from the axial direction.
Biscalix[4]arene Ligands for Dinuclear Lanthanide Ion Complexation
Authors: Wolbers Manon P. , van Veggel Frank C. J. M. , Heeringa Remco H. M. , Hofstraat Johannes W. , Geurts A. J. , van Hummel Gerrit J. , Harkema Sybolt , Reinhoudt David N. 
Published: July 2007

AbstractThree types of lower‐lower rim linked biscalix[4]arenes that contain carboxylic ester (1) and/or amide functions (2 and 3) at their remaining phenolic oxygen atoms were synthesized. The homo‐ and heterodinuclear lanthanide ion complexes based on these ligands were used to study the energy transfer between different lanthanide ions. Photophysical studies comparing the luminescence properties of the homodinuclear Eu3+ complex and the heterodinuclear Eu3+‐Nd3+ complex of 2 indicated that energy transfer is likely to occur from Eu3+ to Nd3+ with an efficiency of > 50%. The luminescence properties turned out to be strongly solvent dependent, which is attributed to structural changes leading to different positions of the lanthanide ions in the cavities provided by the biscalix[4]arene.
Differentiation of spinal cord arteries and veins by time‐resolved MR angiography
Authors: Jaspers Karolien , Nijenhuis Robbert J. , Backes Walter H. 
Published: July 2007

AbstractPurposeTo dynamically resolve the inlet arteries and outlet veins of the spinal cord, particularly the Adamkiewicz artery (AKA) and great anterior radiculomedullary vein (GARV), using MR angiography (MRA).Materials and MethodsFirst, conventional two‐phase angiography (acquisition time = 38–55 seconds) utilizing elliptic centric k‐space ordering was applied to aortic‐aneurysm patients. Changes of vessel intensity were compared between two subsequent dynamic phases. Computer modeling of bolus enhancement and k‐space sampling was performed to demonstrate the relation between vessel enhancement, acquisition time, and vessel diameter. Second, time‐resolved (TR, or “keyhole”) angiography using a reduced number of phase‐encoding steps was explored in healthy volunteers and aortic‐aneurysm patients using acquisition times (range = 6–8.5 seconds) shorter than the spinal cord circulation time.ResultsUsing two‐phase angiography the AKA and GARV were covisualized in the early phase, and contrast decreased for the AKA and increased for the GARV in most (70%) but not all cases. Computer modeling showed that the arteriovenous contrast strongly depended on vessel diameter, and complete separation was only obtained with short acquisition times. Using TR MR angiography (TR‐MRA), complete temporal separation of the AKA and GARV was realized in all cases (100%).ConclusionThe AKA and GARV can be completely separated by TR‐MRA. J. Magn. Reson. Imaging 2007;26:31–40. © 2007 Wiley‐Liss, Inc.
FAIR true‐FISP perfusion imaging of the thyroid gland
Authors: Schraml Christina , Boss Andreas , Martirosian Petros , Schwenzer Nina F. , Claussen Claus D. , Schick Fritz 
Published: July 2007

AbstractPurposeTo evaluate the feasibility of quantitative perfusion MRI of the thyroid gland using an arterial spin labeling (ASL) method.Materials and MethodsAn ASL technique with flow‐sensitive alternating inversion‐recovery (FAIR) spin preparation and a true fast imaging in the steady state (TrueFISP) signal readout strategy was implemented on a 1.5T whole‐body unit. Anatomical and perfusion imaging of the thyroid gland was performed in eight healthy volunteers and one patient with functioning adenoma. Quantitative perfusion maps were calculated using the extended Bloch equations.ResultsIn all subjects the perfusion images showed diagnostic image quality. The mean examination time was 24 minutes for multiplanar perfusion imaging of the entire thyroid gland. Individual perfusion values ranged between 341 ± 91 and 640 ± 90 mL/100 g/minute, with a mean perfusion of 461 ± 90 mL/100 g/minute. The functioning adenoma showed markedly reduced perfusion compared to normal thyroidal parenchyma. No perfusion was noticeable inside four detected thyroid cysts.ConclusionQuantitative ASL perfusion imaging of the thyroid gland using a FAIR‐TrueFISP sequence leads to perfusion maps that may provide important information for assessing thyroid gland pathologies and monitoring therapeutic treatment. J. Magn. Reson. Imaging 2007;26:66–71. © 2007 Wiley‐Liss, Inc.
Malignant or borderline mucinous cystic neoplasms have a larger number of loculi than mucinous cystadenoma: A retrospective study with MR
Authors: Okamoto Yoshikazu , Tanaka Yumiko O. , Tsunoda Hajime , Yoshikawa Hiroyuki , Minami Manabu 
Published: July 2007

AbstractPurposeTo determine whether there is any correlation between the number of loculi and the pathological grade of malignancy in mucinous cystic tumors of the ovary.Materials and MethodsWe retrospectively studied MR images of 67 pathologically proven mucinous cystic tumors of the ovaries. Of these 67 cases, 38 were cystadenomas and 29 were malignant lesions (18 borderline malignancy and 11 adenocarcinomas). We counted the number of loculi and measured the maximum diameter of masses on MRI. We compared the number, the maximum diameter, and the ratio of the number of loculi to the maximum diameter in each adenoma and malignancy using Student's t‐test.ResultsThe mean number of loculi was 18.2 in cystadenoma and 80.9 in malignant lesions. The mean maximum diameter of tumors was 13.0 cm in cystadenoma and 18.7 cm in malignant lesions. The mean ratio of the number of loculi to the maximum diameter was 1.3 in adenoma and 5.4 in malignant lesions. The differences between the benign and malignant lesions were statistically significant in number (P = 0.001), maximum diameter (P = 0.011), and ratio (P = 0.002).ConclusionOvarian mucinous neoplasm of borderline malignancy and mucinous adenocarcinomas had a larger number of loculi than adenomas. J. Magn. Reson. Imaging 2007;26:94–99. © 2007 Wiley‐Liss, Inc.
UV Laser Deposition of SiS/Poly(thiacarbosilane) Composites and their Conversion to SiO/Poly(thiacarbosiloxane) Composites
Authors: Tomovska Radmila , Urbanová Markéta , Šubrt Jan , Boháček Jaroslav , Pola Josef 
Published: July 2007

AbstractArF laser irradiation of gaseous mixtures of carbon disulfide and silane allows efficient deposition of SiS bond‐containing poly(thiacarbosilanes) incorporating SiS bodies. These SiS/poly(thiacarbosilane) composites are the first example of silicon sulfide/polymer composites. Composite formation is analyzed by GC/MS analysis of volatile products and the structure of the composite as determined by electron microscopy and FT‐IR spectra. The composites undergo reaction with air moisture and methanol vapor, evolve H2S and evolve to nano‐sized poly(thiacarbosiloxane)s and poly(methoxythiacarbosiloxane)s.magnified image
Synthesis and Conformation of Three‐Dimensionally Ordered Macroporous Syndiotactic Polystyrene and Poly(p‐methyl styrene)
Authors: Li Haiqing , Abraham Sinoj , Yan Weidong , Ha Chang‐Sik , Kim Il 
Published: July 2007

AbstractThree‐dimensionally ordered macroporous (3DOM) syndiotactic polystyrene (sPS) and poly(p‐methyl styrene) (sPPMS) are synthesized using silica colloidal crystal templates with varied diameters in the range of 548–214 nm, and the effect of polymerization space on the conformation of the resulting 3DOM polymers is investigated by spectroscopy and thermal analysis. In‐situ polymerizations of styrene and p‐methyl styrene within the silica templates induce the resulting 3DOM polymers with different conformations and packing of chains, which are different from those of bulk polymers prepared in the absence of templates. Polymerizations in restricted silica templates result in un‐helixication of 3DOM sPS chains and helixication of 3DOM sPPMS chains.magnified image
Meta‐analysis of heart valve abnormalities in Parkinson's disease patients treated with dopamine agonists
Authors: Simonis Gregor , Fuhrmann Joerg T. , Strasser Ruth H. 
Published: July 2007

AbstractValvular heart disease in patients being treated with ergot‐derivative dopamine agonists (Ergot‐DA) for Parkinson's disease has been reported to occur as a consequence of serotonine receptor stimulation. Goal of this analysis was to estimate the incidence of those changes from recently published studies and to determine its clinical relevance. Medline searches were performed to identify cross‐sectional, echocardiographic studies comparing patients treated with dopamine agonists or controls, in terms of valvular changes. Observational studies of valve changes in Parkinsonian patients were used to estimate the incidence of severe valvulopathy. The results from 7 cross‐sectional studies including 477 patients treated with Ergot‐DA, 127 patients with non‐Ergot‐DA, and 364 control patients were analyzed. Moderate‐to‐severe valvular changes were detected in 26% of patients treated with Ergot‐DA, 10% of patients treated with non‐Ergot DA, and 10% of control patients. Severe valvulopathy was less than 1% both in cross‐sectional and observational studies. The high rate of moderate valvular changes in patients treated with Ergot‐DA suggests that close surveillance of the patients is required. Severe valvulopathy was less than 1% in the studies analyzed. © 2007 Movement Disorder Society