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  • Articles: DFG German National Licenses  (61)
  • Electronic Resource  (61)
  • 1995-1999  (51)
  • 1960-1964  (10)
  • 1910-1914
  • 1890-1899
  • Alkaloids
  • Polymerization
  • 1
    Electronic Resource
    Electronic Resource
    Effect of protein concentration on whey protein gels obtained by a two-stage heating process (1999)
    Springer
    European food research and technology 209 (1999), S. 389-392 
    Details
    ISSN: 1438-2385
    Keywords: Key words Gelation ; Polymerization ; Whey proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The influence of protein concentration on the properties of gels obtained by a two-stage heating process was determined. In the first stage, whey protein dispersion (3–10%) was heated at pH 8.0, and in the second stage it was diluted to 3% protein, adjusted to pH 7.0 and heated again. Increased protein concentration in the first stage of polymerization resulted in the gels obtained in the second stage having a lower phase angle, increased storage modulus and increased hardness. Increased protein concentration also resulted in gels with an increased optical density, which suggests thathigher protein concentration leads to more and larger aggregates. Gels obtained from dispersions preheated at a higher protein concentration had higher permeability coefficient (B gel) values. The increase in B gel suggests that the higher protein concentration increased the size of the aggregates, which in a second stage of heating formed a gel matrix with a larger pore size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002170050514
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  • 2
    Electronic Resource
    Electronic Resource
    Ab initio MO study of ethylene insertion into the Sm–C bond of H2SiCp2SmCH3 (1999)
    Springer
    Theoretical chemistry accounts 102 (1999), S. 285-292 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Ethylene insertion ; ab initio MO calculations ; Sm complexes ; Polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Ethylene insertion into the Sm–C bond of H2SiCp2SmCH3, a model reaction of an olefin polymerization propagation step, has been studied by ab initio molecular orbital methods. The small electronegativity of the Sm atom makes the Sm–C bond ionic, the methyl group being negatively charged by −0.75. The reaction passes through a loose ethylene complex with a binding energy of 15 kcal/mol and then a tight four-centered transition state with an agostic interaction between the Sm atom and one of the methyl CH bonds. A small activation energy of 14 kcal/mol is required to pass through this transition state, indicating that this is an easy reaction. Compared with the reactions with group 4 cationic silylene-bridged metallocenes the activation energy is higher and the reaction is less exothermic. The origin of these differences is discussed. The results of molecular mechanics calculations on regio- and stereoselectivities in the insertion reaction of propylene are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050500
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  • 3
    Electronic Resource
    Electronic Resource
    Improvement of dispersing property of sodium sulfite-formal-dehydeanthraquinone pulping effluent by treatment withCoriolus versicolor (1999)
    Springer
    Journal of wood science 45 (1999), S. 143-148 
    Details
    ISSN: 1611-4663
    Keywords: Coriolus versicolor ; Na2SO3-HCHO-AQ pulping effluent ; Polymerization ; Lignosulfonate ; Laccase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A strain of the fungusCoriolus versicolor was inoculated periodically into potato dextrose agar (PDA) slants containing the effluent to enhance the natural ability to grow in the effluent. The acclimated strain grown in the 50% effluent-containing PDA slant and the original strain were employed to treat the effluent. The acclimated strain could grow in a higher concentration of the effluent than the original unacclimated one. Both the original and acclimated strains improved the dispersing ability of the effluent, especially the acclimated strain because of its higher laccase secretion. The dispersing ability of the SFP effluent was improved to a level comparable to a commercial lignosulfonate product because it was strongly polymerized by the fungus. During the fungal treatment, more than 50% of the sugars were removed from the effluent, thereby increasing the purity of the SFP lignin product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01192331
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetic study of the formation reaction of colloidal silica spheres in microgravity using aircraft (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 474-478 
    Details
    ISSN: 1435-1536
    Keywords: Key words Reaction kinetics in microgravity ; Colloidal silica spheres ; Polymerization ; Transmitted-light intensity ; Dynamic light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Polymerization reactions of colloidal silica spheres via the hydrolysis and dehydration processes of tetraethyl orthosilicate with ammonia and a tiny amount of water in ethyl alcohol have been studied in microgravity by the parabolic flights of a MU-300 rear-jet aircraft. Induction periods and polymerization rates are determined by fast-scanning transmitted-light-intensity measurements and the fast-scanning dynamic light-scattering method. Direct observation of the reaction mixtures is also made with a charge-coupled device video camera. Reproducible and reliable data are obtained in microgravity compared with those in gravity. Increases in the induction times and decreases in the polymerization rates are observed in microgravity compared with those in gravity. One of the main reasons for these observations is the fact that the translational Brownian movement of the reactants and/or product spheres is free from downward translational movement in microgravity. Very weak convection of the reaction suspensions in microgravity is another important factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050411
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  • 5
    Electronic Resource
    Electronic Resource
    Further Alkaloids Common to Ants and Frogs: Decahydroquinolines and a Quinolizidine (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1179-1193 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020898229304
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  • 6
    Electronic Resource
    Electronic Resource
    Polymerization of aqueous liquid-crystalline allyldimethyldodecylammonium bromide (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 1215-1219 
    Details
    ISSN: 1435-1536
    Keywords: Key words Allyldimethyldodecylammonium bromide ; Liquid crystals ; Polymerization ; Polymerizable surfactant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Allyldimethyldodecylammonium bromide was polymerized by γ-ray irradiation in both hexagonal and cubic mesophases, and the conversion–time curves were obtained. The maximum conversion was about 35%, and the polymer remained in the liquid-crystalline structure formed by the nonpolymerized monomers. The influence of polymerization on the distribution of water in the different types related to the hydrophilic surfaces of microstructures was studied using Fourier transform infrared spectroscopy. The incomplete polymerization was explained by steric constraints in the liquid-crystalline structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050513
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  • 7
    Electronic Resource
    Electronic Resource
    Polymerization of vinyl acetate in homogeneous systems obtained in presence of acrylic acid (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 203-209 
    Details
    ISSN: 1435-1536
    Keywords: Key words Microemulsions ; Vinylacetate ; Acrylic acid structure ; Polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The composition ranges over which microemulsions are formed in systems containing vinyl acetate, acrylic acid, water with nonylphenol ethoxylated with 25 mol ethylene oxide monomaleate as surfactant were studied. Conductometric and refractometric investigations have shown the existence of some aqueous/organic, bicontinuous and organic/aqueous microemulsions. The types of precursor microemulsions influence the conversion of monomers. In the presence of a crosslinking agent, diethylene glycol bis maleate, hydrogels are formed whose water absorption depends on the composition of the initial microemulsions. The kinetics of water absorption suggests the modification of polymer network structures as a function of the crosslinked monomer content and the ratio of organic to aqueous phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013744
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  • 8
    Electronic Resource
    Electronic Resource
    A Unified Synthetic Strategy for the Indolopyridine Alkaloid Group (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Syntheses of Batzelline A, Batzeline B, Isobatzelline A, and Isobatzelline B (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1173-1183 
    Details
    ISSN: 1434-193X
    Keywords: Marine alkaloids ; Pyrroloquinoline ; Total synthesis ; Heterocycles ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Batzellines A and B (1a, b) and isobatzellines A and B (2a, b) are 1,3,4,5-tetrahydropyrrolo[4,3,2-de]quinoline-containing marine alkaloids characterized by the presence of a methylthio substituent at C-2 of the tricyclic system. We describe here the total synthesis of these natural compounds following the synthetic strategy that we have used previously for the synthesis of damirones A and B, batzelline C, isobatzelline C, discorhabdin C, and makaluvamines A, B, C, and D. The introduction of the methylthio group by electrophilic substitution of a pyrrolo[4,3,2-de]quinoline, appropriately substituted and in a suitable oxidation state, is the key step in the success of these syntheses.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Iodocyclisation of 1,4-Dihydropyridines; Synthesis and Reactivity of 1-Iodoindolo[2,3-a]quinolizidines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2997-3003 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cyclizations ; Iodine ; Nitrogen heterocycles ; Oxidations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of iodine (or related species) to β-acyl-N-alkyl-1,4-dihydropyridines 1, which possess an N-substituent with an appropriate nucleophile moiety, leads to the corresponding 3-iododihydropyridinium ions, which undergo an internal nucleophilic attack to give, regio- and stereoselectively, the iodobi(poly)heterocyclic ring systems 2a-f in good yields. Reactivity studies on the iodoindoloquinolizidines 2e,f lead to the pentacyclic cyclopropane systems 4a,b, azides 5 and 6, norderivative 9 and, by a base-induced elimination, dihydropyridine 10, a precursor of the zwitterionic alkaloids flavopereirine and 6,7-dihydroflavopereirine.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Lewis Acid Assisted Vinylogous Mannich and Mukaiyama Aldol Reactions: A Route to Densely Hydroxylated Indolizidine Alkaloid Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1395-1400 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Vinylogous Mannich reaction ; Vinylogous Mukaiyama aldol reaction ; Glycosylation inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The hydroxymethyl-substituted indolizidines 6 and 7, representative members of a ring-B-expanded alexine-australine subclass, are readily accessible by starting with furan-based silyloxydiene 12 and hydroxymethyl hemiaminal 11, through a synthesis sequence involving a scantily exploited vinylogous version of the Mannich reaction. The key iminium electrophilic acceptor 11 is, in turn, available through a vinylogous intermolecular Mukaiyama aldolization process between pyrrole-based silyloxydiene 8 and (S)-glyceraldehyde 9.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    A General Approach to Indolizidine Alkaloids From 1-Benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols: Synthesis of (+)-Monomorine I (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3277-3280 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Asymmetric synthesis ; Palladium ; Amino alcohols ; Natural products ; Monomorine I ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile method for the preparation of indolizidine alkaloids from 1-benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols as stereodefined key intermediates has been developed. The utility of this approach was demonstrated by the synthesis of (+)-monomorine I.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    An Efficient Synthesis of 5-(or 6-)Arylbenzoindolizidine and -quinolizidine Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2345-2352 
    Details
    ISSN: 1434-193X
    Keywords: Horner reaction ; Enamides ; Reductions ; Cyclizations ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new methodology for the synthesis of (hetero)arylated benzoindolizidine and benzoquinolizidine derivatives through sequential reduction of pyrrolidine- and piperidine-based aromatic enamides, and ultimate cyclization, is reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Plakinamines C and D and Three Other New Steroidal Alkaloids from the Sponge Corticium sp. (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 697-701 
    Details
    ISSN: 1434-193X
    Keywords: Corticium sp. ; Steroids ; Alkaloids ; Secondary metabolites ; Cytotoxic activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Five new steroidal alkaloids, plakinamines C (1) and D (2), and the related compounds 3-5 have been isolated from the Vanuatu sponge Corticium sp. Their structures have been elucidated by a detailed spectroscopic analysis, including 2D-HMBC and ROESY correlation experiments. The new compounds show significant in vitro cytotoxicity against human bronchopulmonary non-small-cell lung carcinoma cells (NSCLC-N6) with IC50 values of 〈 3.3-5.7 μg/mL. When tested against T leukemia virus type one (HTLV-I), compounds 1, 4 and 5 were found to exhibit slight anti-HIV activity.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Synthesis Mediated by Ring-Closing Metathesis - Applications in the Synthesis of Azasugars and Alkaloids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 959-968 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Alkaloids ; Castanospermine ; Metathesis ; Azasugars ; Manzamine A ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The application of the ring-closing metathesis (RCM) reaction to the construction of a wide variety of nitrogen-containing ring systems is described. The examples include pyrrolizidine, indolizidine, and quinolizidine derivatives related to azasugars. A formal total synthesis of castanospermine (5) is presented. The utilisation of two RCM steps in the synthetic sequence leading to the multicyclic ABCDE nucleus 7 of the complex alkaloid manzamine A (6) is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    A Stereoselective Synthesis of Nonracemic (+)-Desoxoprosophylline by a Tandem Wittig [2+3]-Cycloaddition Reaction (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1407-1414 
    Details
    ISSN: 1434-193X
    Keywords: L-Ascorbic acid ; (+)-Desoxoprosophylline ; Lactones ; Alkaloids ; Domino reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -L-Ascorbic acid serves as chiral starting material for the synthesis of (+)-desoxoprosophylline. The synthetic pathway includes the formation of an O-protected 5-azido-2,3-dideoxysugar which is subjected to a tandem Wittig [2+3]-cycloaddition reaction, leading to the heterocyclic core unit of (+)-prosophylline. Stereoselective hydrogenation and chain elongation yields the desired alkaloid.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    New Piperidine Alkaloids from Two Ladybird Beetles of the Genus Calvia (Coccinellidae) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1749-1755 
    Details
    ISSN: 1434-193X
    Keywords: Natural products ; Piperidines ; Alkaloids ; Coccinellidae ; Calvia14-guttata ; Calviaguttata ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkaloids of two coccinellid beetles, Calvia14-guttata and C.10-guttata have been studied. The major alkaloid of these two species is the new piperidinic cis-lactone 1a, for which the name calvine has been coined. The corresponding trans-lactone 1b (2-epicalvine) is also present as a minor constituent (±10%) in both species. We report here the structure determination and the total synthesis of these compounds. Kept in methanolic solution, these lactones undergo epimerisation as well as opening of the lactone ring leading to a complex mixture of nine main components.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Synthesis of poly(2,3-dimethyl-1,3-butadiene) and its hydrogenation using a metallocene/n-butyllithium catalyst system (1998)
    Springer
    Journal of polymer research 5 (1998), S. 227-232 
    Details
    ISSN: 1572-8935
    Keywords: Anionic ; Polymerization ; Hydrogenation ; Head-to-head ; 2,3-Dimethyl-1,3-butadiene ; Polypropylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Poly(2,3-Dimethyl-1,3-butadiene) (PDMB) with varying contents of 1,4-and 1,2-structures has been anionically synthesized using either n-butyllithium or sec-butyllithium as an initiator. The addition of tetrahydrofuran could enhance the rate of synthesis and effect the microstructure. The Tm was higher for PDMB with a lower content of 1,2-structure, and the Tg was lower. This PDMB was then hydrogenated with a nickelocene/n-butyllithium catalyst system leading to the formation of HPDMB. The trans 1,4-structure unit was more difficult to hydrogenate due to its steric hindrance. Repetitive hydrogenation was necessary in order to achieve a high degree of hydrogenation. The hydrogenated PDMB is an amorphous elastomeric material. The Tg’s were found to decrease with an increase in the degree of hydrogenation, concurrent with a gradual disappearance of the Tm’s. Since a HPDMS with a low content of 1,2-structure resembles a head-to-head polypropylene, our data suggest that the Tg of an atactic head-to-head polypropylene lie between −30 and −35 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0061-8
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  • 19
    Electronic Resource
    Electronic Resource
    A sponge/dinoflagellate association in the haplosclerid sponge Haliclona sp.: cellular origin of cytotoxic alkaloids by Percoll density gradient fractionation (1998)
    Springer
    Cell & tissue research 293 (1998), S. 365-373 
    Details
    ISSN: 1432-0878
    Keywords: Key words Sponges ; Alkaloids ; Nematocysts ; Percoll density gradient fractionation ; Secondary metabolites ; Dinoflagellates ; Symbiodinium microadriaticum ; Sponge ; Haliclona sp. (Porifera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Light-microscopic and electron-microscopic studies of the tropical marine sponge Haliclona sp. (Order: Haplosclerida; Family: Haliclonidae) from Heron Island, Great Barrier Reef, have revealed that this sponge is characterized by the presence of dinoflagellates and by nematocysts. The dinoflagellates are 7–10 μm in size, intracellular, and contain a pyrenoid with a single stalk, whereas the single chloroplast is branched, curved, and lacks grana. Mitochondria are present, and the nucleus is oval and has distinct chromosomal structure. The dinoflagellates are morphologically similar to Symbiodinium microadriaticum, the common intracellular symbiont of corals, although more detailed biochemical and molecular studies are required to provide a precise taxonomic assignment. The major sponge cell types found in Haliclona sp. are spongocytes, choanocytes, and archaeocytes; groups of dinoflagellates are enclosed within large vacuoles in the archaeocytes. The occurrence of dinoflagellates in marine sponges has previously been thought to be restricted to a small group of sponges including the excavating hadromerid sponges; the dinoflagellates in these sponges are usually referred to as symbionts. The role of the dinoflagellates present in Haliclona sp. as a genuine symbiotic partner requires experimental investigation. The sponge grows on coral substrates, from which it may acquire the nematocysts, and shows features, such as mucus production, which are typical of some excavating sponges. The cytotoxic alkaloids, haliclonacyclamines A and B, associated with Haliclona sp. are shown by Percoll density gradient fractionation to be localized within the sponge cells rather than the dinoflagellates. The ability to synthesize bioactive compounds such as the haliclonacyclamines may help Haliclona sp. to preserve its remarkable ecological niche.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051128
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  • 20
    Electronic Resource
    Electronic Resource
    Modes of Action of Allelochemical Alkaloids: Interaction with Neuroreceptors, DNA, and Other Molecular Targets (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 1881-1937 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; molecular targets ; neuroreceptors ; DNA intercalation ; DNA polymerase ; reverse transcriptase ; protein biosynthesis ; membrane stability ; nicotine receptor ; muscarinic receptor ; serotonin receptor ; adrenergic receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several alkaloids are toxic to insects and vertebrates and, in addition, can inhibit the growth of bacteria and plant seedlings. In vitro assays were established to elucidate their modes of action and to understand their allelochemical properties. Basic molecular targets studied, present in all cells, included DNA intercalation, protein biosynthesis, and membrane stability. The degree of DNA intercalation was positively correlated with inhibition of DNA polymerase I, reverse transcriptase, and translation at the molecular level and with toxicity against insects and vertebrates at an organismic level. Inhibition of protein biosynthesis was positively correlated with animal toxicity. Molecular targets studied, present only in animals, included neuroreceptors (alpha1, alpha2, serotonin, muscarinic, and nicotinic acetylcholine receptors) and enzymes related to acetylcholine (acetylcholine esterase and choline acetyltransferase). The degree of binding of alkaloids to adrenergic, serotonin, and muscarinic acetylcholine receptors was positively correlated in G-protein-coupled receptors. Receptor binding and toxicity was correlated in insects. The biochemical properties of alkaloids are discussed. It is postulated that their structures were shaped in a process termed “evolutionary molecular modeling” to interact with a single and, more often, with several molecular targets at the same time. Many alkaloids are compounds with a broad activity spectrum that apparently have evolved as “multipurpose” defense compounds. The evolution of allelochemicals affecting more than one target could be a strategy to counteract adaptations by specialists and to help fight off different groups of enemies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022315802264
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  • 21
    Electronic Resource
    Electronic Resource
    Synthesis of molecular imprinted polymer networks (1998)
    Springer
    Chromatographia 47 (1998), S. 470-474 
    Details
    ISSN: 1612-1112
    Keywords: Affinity chromatography ; Polymerization ; Imprinted polymer networks ; Colloid ; Silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The article covers the methods that are currently available for the preparation of molecularly imprinted polymers. The disadvantages of the conventional grinding of bulk polymerized blocks of imprinted polymer are first identified. The newer methods are divided into four sections: suspension polymerization; modified surfaces; polymer colloids and finally miscellaneous techniques such as the use of linear polymers. Each alternative method is compared with the grinding method and the relative advantages and disadvantages identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466483
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  • 22
    Electronic Resource
    Electronic Resource
    Cyclization of 3-Aminoacrylates - Total Synthesis of Pumiliotoxin C and Related Stereoisomeric Compounds (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2641-2646 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Total synthesis/Pumiliotoxin ; PTX-C ; PTX isomers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the synthesis of pumiliotoxin C (1a) and related stereoisomeric compounds 1c-1f. Starting from (+)- or (-)-3-methylcyclohexanone (6a,b), the oxo esters 7a and 7b were prepared. Condensation with (+)- or (-)-3-aminohexanol (8a,b) gave the stereoisomeric 3-aminoacrylates 9a, 9b and 9c. The hydroxy group of the amino-acrylates was transformed into bromide using the tosylate method. Cyclization of the bromides led to unsaturated quinoline ring systems. Finally, decarboxylation and catalytic hydrogenation gave the different cis- and trans-fused stereoisomeric alkaloids of the pumiliotoxin C type. The structures were verified by X-ray analysis.
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    2-(Het)aryl-Substituted 7-Azabicyclo[2.2.1]heptane Systems (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1997-2001 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Acetylcholine receptor ; Palladium ; C-C coupling ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epibatidine (1) is a recently discovered trace alkaloid found in the skin of a Latin-American poisonous frog. Its remarkably high analgetic activity is accompanied by high toxicity. Therefore, in order to tune its biological activity, a convergent and efficient synthetic pathway was sought to synthesize epibatidine derivatives with different (het)aryl substituents. The hydro(het)arylation of the key intermediate 7-azabicycloheptene (10) represents such an approach. The synthesis of 10 by a Diels-Alder reaction of an N-activated pyrrole (7) with ethynyl p-tolyl sulfone (6) and subsequent steps has been optimized. The crucial last step, the reductive cleavage of the vinyl sulfone 9, has been replaced by a high-yield fluoride-induced degradation of the β-silylated sulfone 12 to give 10. A number of structurally different racemic epibatidine analogs (16b-e) can be prepared by palladium-catalyzed hydro(het)arylation of 10 with iodo(het)arenes 15b-e in good yields.
    Type of Medium: Electronic Resource
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  • 24
    Electronic Resource
    Electronic Resource
    An Expeditious Synthesis of the Dendrobatid Indolizidine Alkaloid 167B (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 865-870 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Enaminones ; Indolizidines ; Sulfide contraction ; Total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the racemic title alkaloid 1 has been accomplished in eight steps and 7.2% overall yield from pyrrolidine-2-thione (5) and ethyl hex-2-enoate (6). Key steps include a ring closure that takes advantage of the nucleophilicity of a vinylogous urethane 8, and stereoselective reduction of the C=C double bond of a bicyclic vinylogous amide 12.
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  • 25
    Electronic Resource
    Electronic Resource
    Synthesis of 5-epi-Isofagomine via Asymmetric Chelate-Enolate Claisen Rearrangement (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1155-1159 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Alkaloids ; Chelates ; Rearrangements ; Glycosidases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyhydroxylated piperidines are an interesting class of glycosidase inhibitors. Chelate enolate Claisen rearrangement of N-protected chiral amino acid esters gives rise to γ,δ-unsaturated amino acids, which can be converted to this type of alkaloids. The potential glycosidase inhibitor 5-epi-isofagomine (5) was synthesized by this approach in a highly stereoselective fashion.
    Type of Medium: Electronic Resource
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  • 26
    Electronic Resource
    Electronic Resource
    Stereoselective Total Synthesis of Enantiomerically Pure 1-Trifluoromethyl Tetrahydroisoquinoline Alkaloids (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 435-440 
    Details
    ISSN: 1434-193X
    Keywords: β-Iminosulfoxides ; Quaternary stereocentre ; Pictet-Spengler reaction ; Alkaloids ; Fluorine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure 1-trifluoromethyl-tetrahydroisoquinoline alkaloid analogues, in which C-1 is a quaternary stereogenic centre, have been synthesized by stereoselective intramolecular Pictet-Spengler reaction of the N-arylethyl γ-trifluoro-β-iminosulfoxide (R)-3, and subsequent elaborations of the sulfinyl auxiliary. The absolute stereochemistry of the stereogenic centre was determined by X-ray diffraction on the α-phenylpropionic ester (1R,2′S)-10.
    Type of Medium: Electronic Resource
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  • 27
    Electronic Resource
    Electronic Resource
    Effect of acetylsalicylic acid on secondary metabolism ofCatharanthus roseus tumor suspension cultures (1997)
    Springer
    Plant cell reports 16 (1997), S. 287-290 
    Details
    ISSN: 1432-203X
    Keywords: Catharanthus roseus ; Acetylsalicylic acid ; Aspirin ; Alkaloids ; suspension cultures ; tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Addition of various concentrations (0.5–20 mM) of acetylsalicylic acid (ASA) to tumor lines ofCatharanthus roseus cultivatedin vitro and requiring corn starch as carbon source, produced remarkable effects on secondary metabolite production. An increase of 505% total alkaloids per culture (cells plus liquid medium), 1587% total phenolics (liquid medium), 612% total furanocoumarins (liquid medium) and 1476% total anthocyanins (liquid medium) was detected. 1 mM ASA in combination with other elicitors, such as homogenates ofAspergillus fumigatus or trans-cinnamic acid, did not further increase the metabolite content substantially. The results suggest that ASA could act as a new biotic elicitor of metabolite production inC. roseus cell suspension culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088282
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  • 28
    Electronic Resource
    Electronic Resource
    Purification and characterization of tubulin from ginkgo pollen (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 136-141 
    Details
    ISSN: 1432-2145
    Keywords: Key words Ginkgo biloba L. ; Tubulin ; Purification ; Polymerization ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Tubulin was purified by a combination of acetone powder preparation, DEAE Sephadex A-50 chromatography, Sephacryl S-300 gel filtration, and Mono Q anion exchange chromatography from the pollen of ginkgo (Ginkgo biloba L.), a typical gymnosperm. The average yield of tubulin is 2 mg per 100 g of pollen grain. The purified tubulin is electrophoretically homogeneous. It seems to be composed of two subunits on SDS-PAGE and is resolved as two major spots on two-dimensional electrophoresis, preliminarily indicating that there are no obvious tubulin isotypes in ginkgo pollen. The apparent molecular weights of the two subunits are about 54 kDa and 52 kDa respectively, estimated from the SDS-PAGE. It was also demonstrated that tubulin from ginkgo pollen is immunochemically related to animal brain tubulin, and the purified tubulin was polymerized to microtubular aggregates in the presence of taxol and GTP in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050080
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  • 29
    Electronic Resource
    Electronic Resource
    Anomalous pH dependence of the coexistence pressure of the polymerizable two-chain N-lipid methyl-bis(pentacosadiinoyl-oxyethyl)-amine (1997)
    Springer
    European biophysics journal 26 (1997), S. 271-275 
    Details
    ISSN: 1432-1017
    Keywords: Key words Diacetylenic lipids ; Polymerization ; Microfluorescence ; Filmbalance ; AFM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular films from polymeric materials play an important role in basic research as well as in technology. We have synthesized the double chain diacetylenic ammonium lipid N-bis-(10, 12-pentacosadiinoyl)-oxy-ethyl)-N-methyl-amine (ONCO). We have characterized monomolecular films at the air/water interface by means of microfluorescence filmbalance techniques and by atomic force microscopy (AFM). ONCO forms stable monomolecular films that exhibit a fluid-solid phase transition with a transition enthalpy of 90 kJ/mol at 10 °C and neutral pH. The coexistence pressure was found to decrease with decreasing protonation, which is in contrast to the commonly found Coulomb mechanism. A change in the chain packing due to a different nitrogen bond angle is discussed as a possible mechanism. This model is cor-roborated by the finding that crystals at high and at low pH differ in their polymerization properties as measured by microfluorescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050080
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  • 30
    Electronic Resource
    Electronic Resource
    Metallacyclodisiladiazanes of Titanium and zirconium; Synthesis, Structure and Polymerization Studies (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 399-404 
    Details
    ISSN: 0009-2940
    Keywords: Disilylamides ; Group 4 Complexes ; Polymerization ; Metallacycles ; Titanium ; Zirconium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of metallacyclodisiladiazanes has been prepared. Lithiated (SiMe2NHtBu)2 (1) reacts with TiCl4 · 2 THF to give (SiMe2NtBu)2TiCl (4). Methylation or fluorination of 4 leads to (SiMe2NtBu)2TiMe2 (8) and (SiMe2MtBu)2TiF2 (9), respectively. The reaction of ZrCl4 · 2 THF with lithiated 1 or [SiMe2NH(4-FC6J4)]2 (2) yields (SiMe2NtBu)2ZrCl2 (5) and [SiMe2N(4-FC6H4)]ZrCl2 · THF (7), respectively. The lithiated ligand [SiMe2NH(2,6-iPr2C6H3)]2 (3) reacts with noncoordinated ZrCl4 to give [SiMe2N(2,6-iPr2C6H3)]2ZrCl2 (6). X-ray structural analysis of 9 showed it to be a fluorine-bridged dimer in the solid state. Compounds 4, 6, 8 and 9 were found to be catalysts for the polymerization of ethylene.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300314
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  • 31
    Electronic Resource
    Electronic Resource
    Silver Chloroacetate: Crystal Structure and Thermal Polymerization Mechanism (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 291-294 
    Details
    ISSN: 0009-2940
    Keywords: Halogenoacetates ; Silver salts ; Solid-state reactions ; Polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of silver chloroacetate was determined by single-crystal X-ray structure analysis. This represents the first salt of a monohalogenoacetic acid with a monovalent metal whose structure was determined with high precision. The salt undergoes a thermally induced solid-state polymerization to polyglycolide under elimination of silver chloride. A probable mechanism for a structure-determined reaction in the solid state is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300224
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  • 32
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    Electronic Resource
    Oligomerization and Polymerization in Sodium Salts of Chlorocarboxylic Acids (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 81-85 
    Details
    ISSN: 0947-3440
    Keywords: Halogenocarboxylates ; Solid-state reactions ; Polyesters ; Thermal analysis ; Polymerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heating of the sodium salts of chlorocarboxylic acids leads to exothermic elimination of sodium chloride and oligomerization of the organic backbone of the molecule. Thermochemical data of sodium 2-chloropropionate (1), sodium 3-chloropropionate (2) and sodium 2-chlorobutyrate (3) were derived. The reaction products were characterized by IR and NMR spectroscopy, and the degree of polymerization was determined by gel permeation chromatography (GPC).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970113
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  • 33
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    Electronic Resource
    Synthese und Konformation von Hexahydro-isochino[1,2-b][3]benzazepinen (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 447-457 
    Details
    ISSN: 0947-3440
    Keywords: Isoquino[1,2-b][3]benzazepines ; Iso-C-homoberbines ; Conformation analysis ; Bischler-Napieralski reaction ; Methyl ∊-hydroxycarboxylates ; Heterocycles ; Alkaloids ; Drug research ; Medicinal chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of Hexahydro-isoquino[1.2.-b][3]benzazepinesThe synthesis of the six hexahydro-isoquino[1,2-b][3]benzazepines 13a-f is described; their conformation is investigated by NMR spectroscopic methods, X-ray analysis and dehydrogenation with mercury(II) acetate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970225
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  • 34
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    Electronic Resource
    Enantiospecific Synthesis of 2,5-Disubstituted Piperidine Derivatives: Synthesis of (+)-Pseudoconhydrine (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1267-1272 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enantiospecific synthesis ; Chiral building blocks ; 2,5-Disubstituted piperidines ; (+)-Pseudoconhydrine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel methodology for the synthesis of any one of the four stereoisomers of a 2,5-disubstituted piperidine in optically pure form is described, starting from readily available chiral building blocks 10 and 11 (or their antipodes). The utility of this approach is demonstrated in the total synthesis of (+)-pseudoconhydrine hydrochloride, the structure of which was confirmed by X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970633
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  • 35
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    Electronic Resource
    Dihydrocolchicine 8,12-Endoperoxide: A Novel Starting Material for Convenient Syntheses of the Allocolchicinoids N-Acetylcolchinol O-Methyl Ether and Androbiphenyline (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2275-2279 
    Details
    ISSN: 0947-3440
    Keywords: Semisynthetic colchicine analogues ; Endoperoxide transformations ; Colchicine-allocolchicine rearrangement ; Axial chirality ; Biaryls ; Alkaloids ; Colchicum autumnale ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure dihydrocolchicine-8,12-endoperoxide 2 is used as the starting material for the synthesis of some bioactive allocolchicinoids. Depending on the reaction conditions and reagents employed, different modifications of the C ring of colchicine (1) are achieved. Triphenylphosphane deoxygenation of 2 leads to the well known N-acetylcolchinol O-methyl ether (NCME, 6, 40% yield from 1). Treatment of the endoperoxide 2 with CH3OH/CH2Cl2/silica gel provides the plant alkaloid androbiphenyline (11) in a yield of 60% from 1. Triethylamine-catalysed transformation of 2 yields (-)-colchicine-8,12-dione (12) (17% yield), together with a mixture of interconverting tetracyclic hemiketals 8a and 8b. For the formation of the allo colchicinoids 6 and 11 plausible reaction pathways are suggested. In contrast to what is found in the literature, the assignment of the absolute configuration of natural (-)-colchicine (1), and the allo-congeners 6 and 11, should be (M,7S) or (aR,7S) instead of (aS,7S).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971115
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  • 36
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    Electronic Resource
    Biotransformation of Ergot Alkaloids by Haloperoxidase from Streptomyces aureofaciens: Stereoselective Acetoxylation and Propionoxylation (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2379-2383 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enzyme catalysis ; Oxidases ; Peroxides ; Acylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Agroclavine (1) was oxidized, by haloperoxidase from Streptomyces aureofaciens, to 2,3-dihydro-6,8-dimethyl-3β-acetoxy-8-ergolen-2-one (2) in the presence of sodium acetate and bromine ions. Acetate was incorporated into the above product during oxidation. In a propionate buffer, incorporation of propionate into the product was observed, yielding 2,3-dihydro-6,8-dimethyl-3β-propionoxy-8-ergolen-2-one (4). The biotransformation proceeded faster in the propionate buffer, affording also the higher oxidation product (4aS),(10bS)-7-amino-3,4,4a,5,6,10b-hexahydro-2,4-dimethyl-6-oxobenzo[f]quinoline (3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971129
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    Electronic Resource
    Chemistry of Opium Alkaloids, XLIIIPart XLII. M. de Grauw, E. F. Muller, R. H. Woudenberg, L. Maat, Recl. Trav. Chim. Pays-Bas 1996, 115, 58. - A PM3 Computational Approach to the Selectivity in the Diels-Alder Reactions of Thebaine and Analogues with Methyl Propenoate (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 13-19 
    Details
    ISSN: 0947-3440
    Keywords: 6-Demethoxythebaine ; Ethenoisomorphinans ; Ethenomorphinans ; Calculations, semiempirical ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geometrically fully-optimized transition structures are calculated for the Diels-Alder adducts of methyl propenoate and the 3-demethoxy derivatives of the dienes thebaine, 6-demethoxythebaine, 5β-methylthebaine, and 5β-methyl-6-demethoxythebaine using the semiempirical PM3 method. The number of calculated forms is limited according to a search of the conformational space of methyl propenoate and of the dienes. The lengths of the incipient bonds in the transition structures vary from 2.0 to 2.4 Å, but the average value of the lengths of these two bonds in the same structure is much more constant: 2.18 ± 0.02 Å. The effects of the methoxycarbonyl group and of the 6-methoxy group on the lengths of the incipient bonds are in agreement with the relative magnitudes of the frontier orbital coefficients. Comparison of the energetic data with experimental results shows that the prediction of the stereo- and regioselectivities from the Gibbs energy of activation differences is good as far as it concerns the main products. The absence of minor products and the formation of the remarkably large amount of 8β-ethoxycarbonyl-6β,14β-ethenomorphinan from 5β-methyl-6-demethoxythebaine does not follow from the calculations.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970105
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  • 38
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    Electronic Resource
    Solanum Alkaloids, 139 - Photolysis of N-Chlorospirosolanes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1589-1592 
    Details
    ISSN: 0947-3440
    Keywords: Photolysis ; N-Chlorospirosolanes, photolysis of ; 23-Chloro- and 23,23-dichlorospirosolanes ; Steroids ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV irradiation of N-chlorosoladulcidine (2) in trifluoroacetic acid, followed by separation and hydrolysis of the obtained 3-O-trifluoroacetates affords (23R)-23-chlorosoladulcidine (5) and 23,23-dichlorosoladulcidine (7). Similar treatment of N-chlorotomatidine (9) affords 23,23-dichloro-22-isotomatidine (12).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970741
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  • 39
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    Synthesis of rac-Midpacamide and the spiro-Cyclization of Its Precursor (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1525-1528 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Biomimetic synthesis ; spiro-Cyclization ; Marine sponges ; Natural products ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkylidene hydantoin 8 was synthesized as an analogue of the marine natural product oroidin (1) by employing a Horner-Wadsworth-Emmons reaction. Treatment of 8 with bromine in acetic acid induced a biomimetic spiro-cyclization forming the ACD ring system of dibromophakellin (2) in one step. rac-Midpacamide (10) was obtained from the same precursor through a chemoselective, ruthenium-catalyzed hydrogenation leaving the brominated pyrrole moiety intact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970731
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  • 40
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    Electronic Resource
    Capillary electrophoresis of natural products (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 2438-2452 
    Details
    ISSN: 0173-0835
    Keywords: Natural products ; Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; Chinese herbal preparations ; Alkaloids ; Toxins ; Illicit drugs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrophoresis (CE) and micellar electrokinetic chromatography were used for the separation of widely different compounds from natural materials including antibiotics, humic substances, flavonoids, isoflavonoids, illicit drugs, coumarins, alkaloids, steroids, Chinese herbal preparations, nicotine, caffeine, amphetamines, toxins such as aflatoxins B1, B2, G1, G2, mycotoxins, heptapeptide aflatoxins and others, ephedrine compounds, mineral elements, and natural compounds in biological samples. A discussion of sample extraction and clean-up and the advantages of using CE is also presented.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150181234
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  • 41
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    The Thermally Induced Solid-State Polymerization Reaction in HalogenoacetatesDedicated to Prof. Günther Klar on the occasion of his 60th birthday. (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1123-1129 
    Details
    ISSN: 0009-2940
    Keywords: Halogenoacetates ; Solid-state reactions ; Polyglycolide ; Thermal analysis ; Polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine salts of halogenoacetic acids MOOC-CH2—X were prepared and characterized by their thermochemical reactivity. It was found that in seven cases elimination of MX led to polymerization of the organic part of the molecule. The resulting polyester, polyglycolide, could be isolated easily by washing the reaction product with water. It has a distinct porous morphology. The reaction takes place at moderate temperatures (100—200°C).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290923
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  • 42
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    The Configuration of (+)-8-Ethylnorlobelol-I; a Correction of the Literature (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 2083-2086 
    Details
    ISSN: 0947-3440
    Keywords: Cycloaddition, 1,3-dipolar ; Piperidine ; Alkaloids ; Lobelia ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The piperidine alkaloid (+)-8-ethylnorlobelo-I is assigned the revised 2S,8,S absolute configuration as depicted in 7. LiAl(O-tBu)3H reduction of the ketone rac-5 proceeded with a high stereoselectivity to give, after hydrolysis of the carbamate function, the syn amino alcohol rac-6. Inversion of the C-8 configuration of ent-6 yielded (-)-8-ethylnorlobelol-I ent-7. A short nitrone-alkene-based synthesis of rac-7 has been developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961220
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    Synthesis of New Nepenthone DerivativesMorphine alkaloids, 135. For part 134 see: J. Marton, Z. Szabó, I. Csorvássy, Cs. Simon, S. Hosztafi, S. Makleit, Tetrahedron 1996, 52, 2449-2464. (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1653-1656 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Morphinans ; Dihydronepenthone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of nepenthone (3a) leads to a mixture of dihydronepenthone (3c) and the secondary alcohol (20S)-4b. The enantiomeric secondary alcohol (20S)-4b is prepared from the 7α-formyl-6,14-ethenomorphinan derivative 3b by reaction with phenylmagnesium bromide to afford a mixture of the diastereoisomeric alcohols 4a. Hydrogenation of 4a leads to (20S)-4b and (20R)-4b, which are separated by fractional crystallization. The conformations of (20S)-4b and (20R)-4b are determined by NOE difference experiments.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961025
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  • 44
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    Synthesis of SBS thermoplastic block copolymers in cyclohexane in the presence of diethylether used as a structure modifier (1995)
    Springer
    Journal of polymer research 2 (1995), S. 91-98 
    Details
    ISSN: 1572-8935
    Keywords: Microstructure modifier ; Isomers ; SBS ; Block copolymer ; Polymerization ; Kinetics ; Diethylether
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Diethylether (DEE) was used as a structure modifier during the synthesis of linear styrene-butadiene block copolymers of poly A-block-polyB-block-polyA type (SBS). The microstructures of synthesized polymers were analyzed, and the effect of DEE on polymerization kinetics was studied. Addition of DEE at 2 wt% concentration results in the highest styrene polymerization rate, while addition at 6 wt% concentration gives the highest butadiene polymerization rate. The vinyl content of the polybutadiene portion increases from 14 to 47% with an increase in the DEE concentration from 500 ppm to 10 wt% while thetrans- l,4 andcis-1,4 isomers decrease. For SBS polymer synthesized via a sequential method, the addition of DEE as a structure modifier minimizes the crossover deficiency which would otherwise result in a skewed molecular weight distribution with a higher polydispersity. For SBS polymers made via a coupling method, the coupling efficiency appears to be constant in a range of DEE concentration from 500 ppm to 1 wt% before declining with a further increase in DEE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01493208
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  • 45
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    Subcritical asymptotic behavior in the thermodynamic limit of reversible random polymerization processes (1995)
    Springer
    Journal of statistical physics 80 (1995), S. 389-404 
    Details
    ISSN: 1572-9613
    Keywords: Polymerization ; Markov process ; limit behavior ; stationary distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a reversible Markov process as a chemical polymerization model and study the asymptotic behavior (in the thermodynamic limit asN→+∞) of a particular probability distribution on the set ofN-dimensional vectors, thekth component of which is the number ofk-mers. The study establishes the existence of three stages (subcritical, near-critical, and supercritical stages) of polymerization, depending on the value of the strength of the fragmentation reaction. The present paper concentrates on the analysis of the subcritical stage. In the subcritical stages we show that the size of the largest length of polymers of sizeN is of the order logN asN→+∞.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02178365
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  • 46
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    Natural products and enzymes from plant cell cultures (1995)
    Springer
    Plant cell, tissue and organ culture 43 (1995), S. 97-109 
    Details
    ISSN: 1573-5044
    Keywords: Alkaloids ; enzymes ; natural products ; plant cell cultures ; Rauwolfia serpentina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants represent an unlimited source of natural products. Many of the recently detected phytochemicals exhibit remarkable bioactivities, ranging from anticancer activity, phosphodiesterase inhibition to cytotoxicity against HIV-infected cells. Cultivated plant cells produce at their unorganized, dedifferentiated stage secondary metabolites, but in very different amounts in so far as new compounds are concerned. In fact, more than 140 novel natural products are presently known from plant cell cultures, which also include new metabolites formed by biotransformation. The biotransformation capacity of suspended cells is described and recent high yielding transformations, like the formation of arbutin by hydroquinone-transformation withRauwolfia cells are discussed. As an example of alkaloid production by cell suspensions, the pattern of monoterpenoid indole alkaloids of the Indian medicinal plantRauwolfia serpentina Benth. is described and the so far 30 identified compounds are divided into eight groups which are biosynthetically closely related. Some of the key biosynthetic reactions leading to theRauwolfia alkaloids are discussed and an overview of the enzymes involved in the formation of the alkaloid ajmaline and proteins catalyzing side reactions of the ajmaline pathway are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052163
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  • 47
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    New alkaloids from ants: Identification and synthesis of (3R,5S,9R)-3-butyl-5-(1-oxopropyl)indolizidine and (3R,5R,9R)-3-butyl-5-(1-oxopropyl)indolizidine, constituents of the poison gland secretion in Myrmicaria eumenoides (hymenoptera, formicidae)Dedicated to Professor Dr. K. Mori on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 965-977 
    Details
    ISSN: 0947-3440
    Keywords: Ants ; Alkaloids ; Myrmicaria eumenoides ; 3-Butyl-5-(1-oxopropyl)indolizidine, (3R,5S,9R)-,(3R,5R,9R)- ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (3R,5S,9R) and (3R,5R,9R) stereoisomers of 3-butyl-5-(1-oxopropyl)indolizidine (9) were identified as major constituents of the poison gland secretion of the African ant, Myrmicaria eumenoides. Racemates of the four diastereomers of 9 were synthesized via the corresponding ethyl 5-(5-butylpyrrolidin-2-yl)pentanoates (6). Enantiomerically pure samples of the (3R)-stereoisomers of 9 were obtained by starting from (2R)-2,3-O-isopropylideneglyceric aldehyde (21) and 6-methylpyridine-2-carboxaldehyde (20). In addition, the enantiomeric separation by chiral gas chromatography and unambiguous structure assignment of the target compounds are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199506138
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  • 48
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    Synthesis of vinca alkaloids and related compounds, 73.Part 72: L. Szabó, Gy. Kalaus, Cs. Szántay, ACH-Models in Gem. 1994, 131, 541. Synthesis and ring transformations of deethylaspidospermane derivatives. Synthesis of (±)-20-deethyl-3-oxotabersonine (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1245-1251 
    Details
    ISSN: 0947-3440
    Keywords: Deethylvincadifformine ; Deethyltabersonine ; Deethyl-3-oxotabersonine ; Deethylapovincamine ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the key compound 14 with methyl 4-formyl-butanoate (9) or with 5-benzoyloxypentanal (13) gave the D-seco-aspidospermane derivatives 17 and 18, respectively. Compound 17 was indirectly and 18 was directly converted to (±)-20-deethylvincadifformine (7) and (±)-20-deethyl-20-epivincadifformine (8). Epimerization occurred in both cases. The thioxo compound 23 was used for the synthesis of (±)-20-deethyltabersonine (28) and (±)-20-deethyl-3-oxotabersonine (27). Oxidative ring transformation of the (±)-20-deethylvincadifformine (7) gave (±)-16-deethylapovincamine (29).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199507165
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  • 49
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    A new synthetic route to the azocino[4,3-b]indole core structure (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1561-1562 
    Details
    ISSN: 0947-3440
    Keywords: Carbazoles ; Azocino[4,3-b]indole ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2 with 2-methoxyethylamine in the presence of ZnCl2 afforded imine 3, which was reduced with NaBH4 to amine 4 without isolation. After deprotection of the carbonyl function by treatment with benzeneseleninic anhydride, ketone 5 was converted to compound 6 with 2-oxobutyric acid and dicyclohexylcarbodiimide. The isodasycarpidone derivative 7, formed by aldol reaction of 6, represents a tetracyclic substructure of strychnos-type alkaloids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199508214
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  • 50
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    Synthesis and stereostructure of some spiro[morphinan-6,2′(3′H)-[1,3,4]oxa(thia)diazolines] (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1393-1395 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Morphinans ; Oxadiazolines ; Thiadiazolines ; (Thio)Semicarbazones, acetylation of ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of dihydrocodeinone (thio)semicarbazones 1a-d with Ac2O/ZnCl2 afforded (6S)-spiro[morphinan-6,2′(3′H)-[1,3,4]oxadiazolines] (2a, b) and (6R)-spiro[morphinan-6,2′-(3′H)-[1,3,4]thiadiazolines] (3a, b), respectively. The structure of the products including the configuration of the spiro carbons was determined by 1H- and 13C-NMR measurements.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199507188
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    Stereospecific Olefin Polymerization with Chiral Metallocene CatalystsDedicated to all those excellent graduate students who are the true heroes of this story (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 1143-1170 
    Details
    ISSN: 0570-0833
    Keywords: alkenes ; catalysis ; metallocenes ; polymerizations ; Catalysis ; Metallocenes ; Polymerization ; Polyolefins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Current studies on novel, metallocenebased catalysts for the polymerization of α-olefins have far-reaching implications for the development of new materials as well as for the understanding of basic reaction mechanisms responsible for the growth of a polymer chain at a catalyst center and the control of its stereoregularity. In contrast to heterogeneous Ziegler-Natta catalysts, polymerization by a homogeneous, metallocene-based catalyst occurs principally at a single type of metal center with a defined coordination environment. This makes it possible to correlate metallocene structures with polymer properties such as molecular weight, stereochemical microstructure, crystallization behavior, and mechanical properties. Homogeneous catalyst systems now afford efficient control of regio- and stereoregularities, molecular weights and molecular weight distributions, and comonomer incorporation. By providing a means for the homo- and copolymerization of cyclic olefins, the cyclopolymerization of dienes, and access even to functionalized polyolefins, these catalysts greatly expand the range and versatility of technically feasible types of polyolefin materials.For corrigendum see DOI:10.1002/anie.199513681
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199511431
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    Oxidative Condensation of Quaternary Phenolic BasesBased on lectures delivered at the International Symposium on Organic Chemistry held by the Societé Chimique de Belgique in Brussels, June 15th, 1962, the XIXth IUPAC Congress in London, July 11th, 1963, a Gordon Research Conference in New Hampton, August 2nd, 1963, and at several American universities and research institutes.Dedicated to Prof Dr. H. Brockmann on the occasion of his 60th birthday (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 192-200 
    Details
    ISSN: 0570-0833
    Keywords: Phenolic bases ; Alkaloids ; Condensation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Provided they contain quaternary nitrogen, simple phenolic bases can undergo oxidative condensation under conditions similar to those of biogenesis to form alkaloids of the isoquinoline series with good yields. By means of such oxidative condensations, more than sixty alkaloids of various structural types have become more easily obtainable. Of the numerous possible condensations of the intermediate mesomeric radicals only those which lead to naturally occurring alkaloids give good yields and few by-products. The results suggest that oxidative condensations of quaternary bases are also involved in the biosynthesis of alkaloids in the plant cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196401921
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    Stereospecific Homopolymerization of CyclopenteneLecture given by Dall' Asta at the Gordon Research Conference on Polymers, Santa Barbara, Calif. (U.S.A.) in January, 1964, and to the Macromolecular Colloquium in Freiburg/Breisgau (Germany), in March, 1964. (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 723-729 
    Details
    ISSN: 0570-0833
    Keywords: Stereospecific polymerization ; Polymerization ; Polycyclopentene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of cyclo-olefins, like that of olefins with an internal double bond, is sterically hindered. Within recent years it has become possible to prepare copolymers of these compounds with ethylene, with the aid of anionic coordination Ziegler catalysts. This copolymerization always results in cis-opening of the double bond. Despite the steric hindrance, cyclobutene and cyclopropene have also been homopolymerized, with opening of the double bond. - Rather surprisingly, the best catalysts for homopolymerization of cyclopentene are those which exhibit low activity in the polymerization of ethylene. Ring cleavage occurs with MoCl5/Al(C2H5)3 to give the cis-polypentenamer, whereas WCl6/Al(C2H5)3 gives the trans-polypentenamer. Both polypentenamers exhibit elastomeric properties. - Evidence from infrared spectra and oxidative degradation indicates that the monomer units in the trans-polypentenamer are linked head-to-tail. It is presumably the single bond adjacent to the double bond that is broken. Using X-ray methods at -50 °C, it was possible to determine the crystal structure of the crystalline trans-polypentenamer at about 400% elongation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196407231
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    The Biosynthesis of Alkaloids IIPart I of this review appeared in Angew. Chem. Internet. Edit. 2, 341 (1963). (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 441-458 
    Details
    ISSN: 0570-0833
    Keywords: Biosynthesis ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196304411
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    Low-Temperature Polymerization of EthylenePublished on the occasion of the 100th anniversary of the founding of Farbwerke Hoechst on January 11th, 1963 (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 32-41 
    Details
    ISSN: 0570-0833
    Keywords: Polymerization ; Polyethylene ; Titanium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A two-component organometallic catalyst of composition CH3TiCl3·CH3AlCl2 effects high-speed polymerization of ethylene in the presence of chlorinated hydrocarbons at low temperatures. The catalyst does not undergo any alteration in the process. In contrast to the Ziegler catalysts, the titanium remains quadrivalent. Olefins of low-molecular-weight and with branched structures are produced. It proved possible to isolate the primary products of the polymerization at -50 to -100°C and to elucidate the mode of their formation from a knowledge of their structures. The findings are incompatible with either a cationic or anionic reaction mechanism. A novel type of mechanism is proposed, whereby the catalyst is supposed to have an ionic structure and molecular growth proceeds via π-complex formation of the olefin with the titanium cation. The formation of ethylene/olefin copolymers is also discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196300321
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    The Biogenesis of Ergot AlkaloidsDedicated to Professor Hans von Euler on the occasion of his 90th birthday (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 243-247 
    Details
    ISSN: 0570-0833
    Keywords: Ergot alkaloids ; Alkaloids ; Biosynthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article the biogenesis of the ergoline ring in lysergic acid derivatives and the clavines is discussed. T·yptophan and mevalonic acid are the precursors. The N-methyl group is supplied by formate or methionine. Concepts and results dealing with the manner in which the compounds are formed are discussed. Finally, the known biogenetic relationships among the ergot alkaloids are discussed in connection with their biogenesis.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196302431
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    Emulsion Polymerization of Vinyl Monomers under the Influence of Ionizing Radiation (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 295-308 
    Details
    ISSN: 0570-0833
    Keywords: Emulsion polymerization ; Polymerization ; Polymerization ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ionizing radiation induces the polymerization of some vinyl monomers in aqueous emulsion with high radiation yields. With identical emulsion compositions, the kinetics of this reaction and the kinetics of emulsion polymerization induced by water-soluble initiators are very similar. The rate of reaction in emulsion polymerization is about one hundred times greater than in bulk polymerization. The initiation of emulsion polymerization by means of ionizing radiation permits uniform “illumination” of the reacting volume, as well as almost any desired variation in the frequency of initiation during the reaction. The sharp decrease in the overall rate of reaction when initiation is interrupted during emulsion polymerization of styrene induced by γ-rays contradicts the earlier concept of sharply separated reaction zones.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196302951
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    The Biosynthesis of Alkaloids IPart II of this review will appear in a subsequent issue of this journal.Dedicated to Professor Dr. Adolf Butenandt on the occasion of his 60th birthday (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 341-357 
    Details
    ISSN: 0570-0833
    Keywords: Biosynthesis ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196303411
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    Reactions of Olefins with the Titanium-Carbon BondDedicated to Prof. Dr. Karl Ziegler on the occasion of his 65th birthday (1963)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 704-714 
    Details
    ISSN: 0570-0833
    Keywords: Titanium ; Alkenes ; Polymerization ; Titanium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: At low temperatures, ethylene and α-olefins (Δ1-olefins or 1-alkenes) are rapidly converted into oligomrs by the two-component organometallic catalyst CH3TiCl3·CH3AlCl2. To achieve smooth oligomerizations, aromatic or chlorinated hydrocarbons must be used as solvents. Although the activity of the titanium-carbon bond is enhanced by the aluminum component of the catalyst, the aluminum and its methyl group do not participate in the reaction proper; the latter proceeds exclusively at the titanium-carbon bond. The reaction will olefins can be used as an analytical method for the quantitative determination of the titanium-carbon bond in admixture with the organoaluminum component. It is thus possible to follow the reaction leading to formation of the catalyst from titanium tertrachloride, as well as the processes occurring at the titanium-carbon bond during the oligomerization of olefins. All the observations indicate that the catalyst possesses an ionic structure which is determined by the solvent. It is shown that the initial reaction step probably involves formation of a complex between the olefin and the alkyltitanium cation. The reaction scheme proposed is based on organometallic reactions which are characterized by carbanion and hydride transfers within the olefin-cation complex. This mechanism, which is unusual for Ziegler catalysts, is due to the predominance of hydride transfers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196307041
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    Pyrrolidone, Capryllactam and Laurolactam as new Monomers for Polyamide FibersFrom a lecture delivered at the meeting of the Plastics and Rubber Section of the Gesellschaft Deutscher Chemiker on April 9th, 1962, in Bad Nauheim (Germany). (1962)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 1 (1962), S. 430-435 
    Details
    ISSN: 0570-0833
    Keywords: Pyrrolidone ; Polyamides ; Fibers ; Lactams ; Polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The industrial production of capryllactam (1-azacyclononan-2-one) and of laurolactam (1-azacyclotridecan-2-one) starts with cyclization of acetylene or butadeine to give cyclooctatetraene or cyclooctadiene, or cyclization of butadiene to give cyclododecatriene. Further steps are: oxidation of the cyclic hydrocarbon to the ketone, formation of the oxime, and rearrangement of the latter with sulfuric acid. Pyrrolidone can be prepared from acetylene and formaldehyde by way of butyrolactone. The behavior of the lactams during polycondensation is described and the properties of the resulting fibers are compared with those of the known polyamide fibers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196204301
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    β-Lactams, Their Polymerization and Use as Raw Materials for FibersFrom a lecture delivered on April 9th, 1962 at a meeting of the GDCh-Fachgruppe “Kunstsoffe and Kautschuk” Plastics and Rubber Division of the German Chemical Society in Bad Nauheim. (1962)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 1 (1962), S. 481-488 
    Details
    ISSN: 0570-0833
    Keywords: Lactams ; Polymerization ; Fibers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Lactams can be prepared by cyclization of β-aimno acid esters. Recently they have become available also from olefins by addition of N-carbonysulfamyl chloride (isocyanatosulfonyl chloride) and from aldehydes by reaction with N-carbonylsulfamyl chloride and ketene. Condensative or anionic polymerization results in polyamides the chains of which contain many more amide groups than the chains of polyamides of the nylon-6 type. Hence the new polymers resemble silk moreclosely. Fibers and films can be prepared from solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196204811
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