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  • 1
    Electronic Resource
    Electronic Resource
    Unexpected Configurational and Conformational Preference in Bicyclo [3.2.0]heptane Systems (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 703-720 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Einige 7endo-monosubstituierte Bicyclo[3.2.0]hept-2-en-6-one and Bicyclo-[3.2.0]heptan-6-one zeigen eine unerwartete thermodynamische Stabilität gegenüber den entsprechenden 7exo-Isomeren. Die basenkatalysierte Epimerisierung (NaOH oder N(CH2CH3)3) verschiedener 7-monosubstituierter Bicyclo[3.2.0]-hept-2-en-6-one (1-7) und Bicyclo[3.2.0]heptan-6-one (8-10) führt je nach Substituent (R) zu folgenden endo/exo-Gleichgewichtsgemischen: (a) Bicyclo[3.2.0]-hept-2-en-6-one: R = F: 89/11, R = C1: 87/13, R = CH3: 76/24, R = CH2CH3: 65/35, R = CH (CH3)2: 57/43, R= C (CH3)3: 10/90, R= C6H5: 66/34; (b) Bicyclo[3.2.0]-heptan-6-one: R = C1: 85/15, R = CH3: 45/55, R= C (CH3)3: 0,4/99,6. In jedem Fall wurde das gleiche Epimerengemisch erhalten, ausgehend sowohl vom endo- wie auch vom exo-Isomeren.Die bemerkenswerte endo-Stabilität wird einer Bevorzugung der Konformation 11 des Cyclobutanonringes zugeschrieben, verursacht durch geringere Pitzer-Spannung. So kann ein endo-Substituent an C(7) eine pseudoäquatoriale Lage am Cyclobutanonring einnehmen. Bei sehr sperrigen Substituenten mit zunehmender Raumerfüllung nimmt eine 1,2-abstossende Wechselwirkung langsam überhand, bis im Falle des t-Butylsubstituenten die exo-Konfiguration die stabilere wird.Die Dehalogenierung von 7-Halo-substituierten Bicyclo [3.2.0]hept-2-en-6-onen (15 bis 21) mit Zink und Eisessig und mit Tributylzinnhydrid führte zu den folgenden endo/exo-Epimerengemischen der entsprechenden 7-monosubstituierten Bicyclo [3.2.0]hept-2-en-6-one (2 bis 7): R = C1: 92/8, R = CH3: 93/7, R = CH2CH3: 93/7, R = CH(CH3)2: 92/8, R = C(CH3)3: 93/7, R = C6H5: 93/7. In allen Fällen, also unabhängig vom Substituenten R, war das endo-isomere stark bevorzugt. Es muss sich also um eine kinetische Kontrolle im isomerenbestimmenden Schritt handeln: Die Reduktion verläft über das Enolat, bzw. über eine Radikalspezies mit trigonal-planarer Anordnung am C(7), so dass die (irreversible) Wasserstoff-Anlagerung von der weniger behinderten Site, der exo-Seite her erfolgt.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650308
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  • 2
    Electronic Resource
    Electronic Resource
    Field desorption mass spectrometry of basic peptides. An approach to the sequencing of arginine-containing peptides (1980)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1980), S. 288-293 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three basic hexapeptides which have two adjacent arginyl residues were studied by field desorption mass spectrometry. At low emitter temperature singly and doubly charged pseudomolecular ions [M + 1]+ and [M + 2]2+ were observed. At higher temperature, these peptides gave a relatively complex fragmentation pattern which can be explained as resulting from preferential cleavages involving the Arg-Arg sequence. A mechanistic interpretation is proposed for this type of fragmentation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200070705
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  • 3
    Electronic Resource
    Electronic Resource
    Calmodulin intracelluar concentration and cAMP-dependent protein kinase activity in human sperm samples in relation to sperm motphlogy and motlity (1983)
    New York, NY : Wiley-Blackwell
    Gamete Research 8 (1983), S. 171-182 
    Details
    ISSN: 0148-7280
    Keywords: calmodulin ; cAMP-dependent protein kinases ; sperm structural anomalies ; cell motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Calmodulin concentration and cAMP-dependent protein kinase activity have been determined in human sperm samples. No significant differences have been noticed in the motility index of two groups of sperm samples differing in their intracellular concentration of calmodulin. It was however found that a low intracellular clamodulin concentration is frequently associated with particular anomalies of the head and tail region. In contrast, a positive correlation has been demonstrated between the motility index and the whole extractable cAMP-dependent protein activity of the different sperm samples. In suspension s, When the cAMP-dependent protein kinase activity was measured on intact sperm suspensions, a positive correlation between the activity and the motility index was also found.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120080206
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamic stereochemistry at sp2—sp3 bonds part 1 - the use of heterocyclic models for quantitative studies of steric effects of alkyl groups (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 120-124 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The barriers to rotation of the 3-substituent in six 3-RCH2-4-Me-δ4-thiazoline-2-thiones (R = Me, Et, Pr, Isobu, Isopr,t-Bu) and in two analogous methiodides have been measured by the 1H DNMR technique. The barriers are discussed in relation to the possible conformations of the transition states, and comparisons are made with barriers to rotation of the same substituents in other frameworks. It is concluded that the relative steric effects are strongly dependent on the framework and that, in general, a conformational analysis of the individual cases is necessary to understand the steric effects of alkyl groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140208
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic stereochemistry at sp2—sp3 bonds part IIFor Part I, see Ref. 2. - the importance of ground-state strain in the determination of apparent spatial requirements of substituents (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 166-170 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The barriers to rotation of RCH2 groups (R = Me, Et and Isopr) as 3-substituents in 4-Me-δ4-thiazoline-2-thiones, their 4-t-Bu analogues, and the methiodides of the latter compounds have been studied by 1H DNMR and by molecular mechanics calculations. The barriers in the 4-t-Bu compounds are rather insensitive to the size of R, which is shown to be caused by strain in the ground state. More generally, it is shown that when δG
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140304
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  • 6
    Electronic Resource
    Electronic Resource
    Detection and quantification of steroids produced by microbial fermentation of sterols by means of MIKE spectrometry and selected Metastable Ion Monitoring (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 527-533 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several steroids generated by microbial fermentation of cholesterol were identified by the mass analysed ion kinetic energy (MIKE) spectra of their molecular ions generated under electron impact, and quantified by selected metastable ion monitoring. These analyses were performed on a crude solvent extract without any purification or molecular separation procedures. The detection limit was below the nanogram range. Identification and quantification of the major constituents, namely androst-4-ene-3,17-dione and androsta-1,4-diene-3,17-dione were fast and easy. Pregnenolone and progesterone which were present at a much lower level were identified with more difficulty by their MIKE spectra alone, because of the existence of isobaric interfering ions. Nevertheless, their quantification by single or dual metastable monitoring was possible.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200091206
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanism of the chain process forming H2 in the photooxidation of formaldehyde (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1599-1608 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mechanism for the formation in a chain of H2, CO, and HCOOH in the photooxidation of formaldehyde is proposed. This mechanism is initiated by the addition of HO2 to formaldehyde. Hydrogen atoms are produced by the thermal dissociation of the HOCH2O radical: HOCH2O → H + HCOOH; ΔH = + 3.2 kcal/mol [5]. Photolysis of CH2O—O2—NO mixtures and product analysis were carried out in conjunction with kinetic simulation yielding an estimate for the activation energy of the dissociation reaction : E5 = 14.9 ± 1.0 kcal/mol. Previous observations of this chain process are considered in view of this mechanism.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550161213
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  • 8
    Electronic Resource
    Electronic Resource
    Le Spectromètre Raman comme Détecteur Séleitif de la Chromatographie en Phase Liquide (1980)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 9 (1980), S. 193-197 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The purpose of this work is to show that it is possible to use microcells in Raman spectroscopy to detect chemical species in various solvents at low concentrations in order to connect a liquid chromatograph with a Raman spectrometer. Several methods are described in static as well as in dynamic processes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250090313
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