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  • 1
    Electronic Resource
    Electronic Resource
    Cation Transport across Bulk Liquid Organic Membranes with Oligomers of (R)-3-Hydroxybutanoic Acid (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 2570-2580 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several oligomeric derivatives 1-5 of (R)-3-hydroxybutanoic acid and a cyclic trimer of (R)-3-hydroxypentanoic acid (6) were used as ionophores to transport potassium picrate across a bulk liquid CH2Cl2 membrane. Using the cyclic trimer 1 and an oligomer mixture of (R)-3-hydroxybutanoic acid, 5 (ca. 28-mer), for the transport experiments, the alkali-metal ions from Li+ to Cs+ and the alkaline-earth-metal ions from Mg2+ to Ba2+ were also shown to be transported through the organic phase. Although a pronounced enhancement of the transport rates was observed in the presence of 3-hydroxyalkanoate oligomers, no special selectivity for one ion was detected. The ionophore properties of the investigated oligomers and oligolides derived from 3-hydroxybutanoic acid are compatible with the alleged role of oligo(3-hydroxybutanoate) (c-PHB; ca. 120-mer) as component of ion channels through cell membranes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760717
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  • 2
    Electronic Resource
    Electronic Resource
    Complexes of the Triolide from (R)-3-Hydroxybutanoic Acid with Sodium, Potassium, and Barium Salts: Crystal Structures, Ester Chelates and Ester Crowns, Crystal Packing, Bonding, and Electron-Localization Functions (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 2581-2601 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The triolide of (R)-3-hydroxybutanoic acid ((R,R,R,))-3,7,11-trimethyl-2,6,10-trioxadodecane-1,5,9-trione; (1), readily available from the corresponding biopolymer P(3-HB) in one step, forms crystalline complexes with alkali and alkaline earth salts. The X-ray crystal structures of three such complexes, (3 NaSCN)·4 1 (2), (2 KSCN)·2 1 · H2O (3), and (2) Ba(SCN)2 · 2 1 · 2 H2O · THF (4), have been determined and are compared. The triolide is found in these structures (i) as a free molecule, making no contacts with a cation (clathrate-type inclusion), (ii) as a monodentate ligand coordinated to a single ion with one carbonyl O-atom only, (iii) as a chelator, forming an eight-membered ring, with two carbonyl O-atoms attached to the same ion, (iv) as a linker, using two carbonyl O-atoms to bind to the two metals of an ion-X-ion unit (ten-membered ring), and (v), in a crown-ester complex, in which an ion is sitting on the three unidirectional C=O groups of a triolide molecule (Figs. 1-3). The crystal packing is such that there are columns along certain axes in the centers of which the cations are surrounded by counterions and triolide molecules, with the non-polar parts of 1 on the outside (Fig. 4). In the complexes 2-4, the triolide assumes conformations which are slightly distorted, with the carbonyl O-atoms moved closer together, as compared to the ‘free’ triolide 1 (Fig. 5). These observed features are compatible with the view that oligo (3-HB) may be involved in the formation of Ca polyphosphate ion channels through cell membranes. A comparison is also made between the triolide structure in 1-4 and in enterobactin, a super Fe chelator (Fig. 5). To better understand the binding between the Na ion and the triolide carbonyl O-atoms in the crown-ester complex, we have applied electron-localization function (ELF) calculations with the data set of structure 2, and we have produced ELF representations of ethane, ethene, and methyl acetate (Figs. 6-9). It turns out that this theoretical method leads to electron-localization patterns which are in astounding agreement with qualitative bonding models of organic chemists, such as the ‘double bond character of the CO—OR single bond’ or the ‘hyperconjugative n → σ* interactions between lone pairs on the O-atoms and neighbouring σ-bonds’ in ester groups (Fig. 8). The noncovalent, dipole/pole-type character of bonding between Na+ and the triolide carbonyl O-atoms in the crown-ester complex (the Na—O=C plane is roughly perpendicular to the O—C=O plane) is confirmed by the ELF calculation; other bonding features such as the C≡N bond in the NaSCN complex 2 are also included in the discussion (Fig. 9).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760718
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Linear Oligomers of (R)-3-Hydroxybutyrate and Solid-State Structural Investigations by electron microscopy and X-ray scatteringDedicated to Prof. Dr. H. Ringsdorf on the occasion of his 65th birthday (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1099-1123 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Repetitive treatment of the biopolymer P(3-HB) (molecular weight 〉 105 Dalton, storage or s-P(3-HB)), with lithium hexamethyl disilazanid (LHMDS) at -70° in THF leads to a mixture of oligomers with increasingly sharp distribution around a 15-, 30-, and 45mer. Discrete fragments are also isolated when P(3-HB) is heated under reflux (89°) in neat Et3N. Linear oligo(3-HB) derivatives (3-7) containing up to 96 3-HB units are synthesized using an exponential segment-coupling strategy. These oligomers are used to calibrate size-exclusion chromatography columns for the analysis of oligo(3-HB) samples from the different sources. The linear oligo-(3-HB) derivatives also served as a model with respect to the physical properties of high molecular weight P(3-HB) and were investigated as such by transmission electron microscopy (TEM) and by small- and wide-angle X-ray scattering (SAXS and WAXS). The thicknesses of the lamellar crystallites (long periods) formed by the 8mer, 16mer, and 32mer, are ca. 26, 52, and 53 Å, respectively, indicating that the 32mer molecules are folded once, very tightly, into a ‘hair-pin’-type conformation. High-molecular-weight P(3-HB), which was crystallized in a similar way, also has a lamellar crystallite thickness of ca. 50-65 Å. Thus, the treatment of P(3-HB) with LHMDS at low temperature causes etching of the amorphous regions, an effect well known in polymer science for studying the regularity of chain folding. The ca. 50-Å packing within the tight folds of P(3-HB) is discussed in view of its possible function in ion transport through cell membranes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770423
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  • 4
    Electronic Resource
    Electronic Resource
    Stereoselektive Umsetzungen von rac-, (R), oder (S)-5-Alkyliden-2-t-butyl-3-methyl-4-oxo-1-imidazolidincarbonsäure-t-butylestern (chirale 2,3-Dehydroaminosäure-Derivate) und Herstellung einiger nichtproteinogener Aminosäuren (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 669-684 
    Details
    ISSN: 0170-2041
    Keywords: Amino acids, dehydro-, chiral ; Amino acids, nonproteinogenic ; Michael additions of cuprates ; a5-Reactivity of doubly unsaturated carbonyl compounds ; Kinetic d2-versus thermodynamic d4-reactivity of Li dienolates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Conversions of t-Butyl rac-, (R)-, or (S)-5-Alkylidene-2-t-butyl-3-methyl-4-oxo-1-imidazolidinecarboxylates (Chiral 2,3-Dehydroamino Acid Derivatives) and Preparation of Some Nonproteinogenic Amino AcidsThe reacivity of the alkylidene derivatives 1-11 specified in the title and prepared in two operational steps from commercially available Boc-BMI and aldehydes is investigated. - According to high-field 1H-NMR analysis of the crude products, additions of H—H and D—D (catalytic hydrogenation, products 12-20, of R—H (BF3-activated R2CuLi/LiI and protonation, products 21-29), and of Cl2C (CHCl3/NaOH, products 33, 34) occur with complete selectivity from the face opposite to the t-butyl group. The doubly unsaturated carbonyl derivative 11 reacts with dibutyl cuprate in the δ position, again with formation of a single diastereomer 32, while trifluoroethylidene-Boc-BMI 3a is reduced to the difluoro analogue 30 by this cuprate. - Li dienolates are generated by deprotonation with LDA of the ethylidene (2a) and butylidene compound 4a; subsequent alkylations (with primary and secondary halides, products 35-41) and hydroxyalkylations (with aldehydes, products 42-44) lead to single products of electrophilic attack in the a carbonyl position (C-5 of the imidazolidinone ring) under kinetic control. On the other hand, reaction of the 2a-derived dienolate with benzaldehyde under equilibrating conditions furnishes the four possible (E/R, E/S, Z/R, and Z/S) γ adducts 45-48. - A combination of methods - 1H- and 13C-NMR spectroscopy, NOE measurements, spectroscopic analogies, chemical correlation (with authentic samples or by spectroscopic or optical comparison), and X-ray analysis (Table 1, Figure 1, Schemes 1 and 2) - is used to assign the product configurations and thus the stereochemical course of the reactions. Some unusual amino acids (50-52, 54, 55) are prepared by hydrolysis of the corresponding imidazolidinones.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101119
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrolyse und CLEMMENSEN-Reduktion des Cyclopentanon-(2)-oxalylsäure-(1)-äthylestersHerrn Professor Dr. L. Wolf zum 65. Geburtstage gewidmet (1961)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 14 (1961), S. 261-268 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Der Cyclopentanon-oxalylsäureester I kann entweder nahezu quantitativ zur freien Ketosäure III oder unter Ringspaltung in 60proz. Ausbeute zur α-Oxo-pimelinsäure (IV) hydrolysiert werden.Bei der CLEMMENSEN-Reduktion von III entsteht in etwa 50proz. Ausbeute Cyclopentanonyl-essigsäure (V), die erst unter energischen Bedingungen in Cyclopentylessigsäure (VI) übergeht. Danach werden hochenolisierte α-Ketoester nicht - wie bisher angenommen - zu α-Hydroxysäuren, sondern zu den zugrunde liegenden Carbonsäuren reduziert. Erhärtet wird dieser Befund durch die glatte Überführung des Dioxalylsäureesters VIII in das Di-essigsäurederivat IX.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19610140410
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  • 6
    Electronic Resource
    Electronic Resource
    1,1,3,3-Tetrachlordisilazan169. Mitteilung zur Chemie der Silicium - Stickstoff-Verbindungen. 168. Mitt.: H. P. Baldus, W. Schnick, U. Wannagat, G. Bogedain. SiPN3 Chem. Mater. 5 (1993) 845 (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 239-248 
    Details
    ISSN: 0044-2313
    Keywords: 1,1,3,3-tetrachlorodisilazane ; silicon coordination compounds ; IR-spectra ; Raman spectra ; NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,1,3,3-TetrachlorodisilazaneThe new compound 1 can be prepared by the reaction of calciumoctamminedichloride, CaCl2(NH3)8, with trichlorosilane, HSiCl3. IR, Raman, 1H and 29Si NMR spectra show a planar Si2NH framework, probably C2-symmetry of the whole molecule and a symmetrical distribution of the four chlorine atoms.In 1 we have got a compound with Bronsted and Lewis acidity, which reacts with three equivalents of pyridine to HSiCl2(py)2—NH(py)—HSiCl2. This addition compound exhibits a fourfold and a sixfold coordinated silicon atom as is shown by a 29Si-solid-NMR spectrum. By thermal decomposition of 1 the new compound 1,3,5-trichloro-2,4,6-tris(dichlorosilyl)-cyclo-1,3,5-trisil-2,4,6-triazane, Si6Cl9H6N3, 4, is formed. With piperidine, 1 reacts by substitution of all four chlorine atoms to compound 5, whereas with diazomethane the NH-functionality is converted to a NCH3 group in 6. Attempts of lithiation lead mainly to a substitution of the chlorine atoms by alkyl groups
    Notes: Durch Umsetzung von Calciumoktammindichlorid, CaCl2(NH3)8, mit Trichlorsilan, HSiCl3, kann die bisher unbekannte Verbindung 1,1,3,3-Tetrachlordisilazan, 1, Si2Cl4H3N, erhalten werden. IR-, Raman-, 1H- und 29Si-NMR-Spektren lassen auf ein planares Si2NH-Gerüst, wahrscheinlich C2-Molekülsymmetrie und symmetrische Verteilung der vier Chloratome schließen.1 zeigt sowohl Brönsted- als auch Lewis-Acidität und reagiert mit drei Äquivalenten Pyridin zu HSiCl2(py)2—NH(py)—HSiCl2, mit laut 29Si-Festkörper-NMR-Spektrum einem sechsfach und einem vierfach koordinierten Si-Atom.Die thermische Zersetzung von 1 führt u. a. zum bisher unbekannten 1,3,5-Trichlor-2,4,6-tris(dichlorsilyl)-cyclo-1,3,5-trisil-2,4,6-triazan, Si6Cl9H6N3, 4. Mit Piperidin reagiert 1 unter Substitution der vier Cl-Atome zu Verbindung 5, mit Diazomethan unter Überführung der NH in eine NCH3-Gruppe zu 6. Lithiierungsversuche von 1 führen bevorzugt zur Cl-Substitution durch Alkylgruppen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210213
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  • 7
    Electronic Resource
    Electronic Resource
    Si/C/F/H materials from laser-explosive decomposition of fluoromethylsilanes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 7 (1993), S. 381-389 
    Details
    ISSN: 0268-2605
    Keywords: Si/C/H/F materials ; laser deposition ; laser spallation ; structure ; reactivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid Si/C/H/F materials laser-deposited from gaseous fluoro-methylsilanes are examined by XPS, SEM, IR and Raman spectroscopy and revealed to be a blend of silicon-carbon-based frameworks, possessing some Si-H and C-H bonds, and carbon whose modification is dependent on the structure of the parent fluoromethylsilane. Their properties are affected by contact with the atmosphere: although incorporation of oxygen into silicon-carbon frameworks is a very fast process, the dramatically improved adhesion to aluminium requires long exposure periods.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590070605
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