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  • 1
    Electronic Resource
    Electronic Resource
    C-Substituierte 1,2,3,5-Dithiadiazoliumsalze und 1,2,3,5-Dithiadiazolyle (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 266-268 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon Substituted 1,2,3,5-Dithiadiazolium Salts and 1,2,3,5-Dithiadiazolyles
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360315
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  • 2
    Electronic Resource
    Electronic Resource
    Design and development of chiral reagents for the chromatographic e.e. determination of chiral alcohols (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 397-401 
    Details
    ISSN: 0899-0042
    Keywords: chiral derivatization ; capillary GC ; capillary SFC ; diastereoisomeric esters ; optical resolution ; (S)-Trolox methyl ether ; primary alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (S)-Trolox methyl ether is known as a powerful chiral reagent for the e.e. determination of chiral alcohols by separation of the corresponding diastereoisomeric esters on achiral GC and SFC columns. In order to further improve his methodology, five possible candidates resultings from variation of structural elements of parent reagent have been tested for derivatization with selected alcohols and subsequent analysis of the diastereoisomeric pairs of esters. The results of this optimization procedure showing the ways to new potent reagents are discussed. © 1996 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 41-50 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720106
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  • 4
    Electronic Resource
    Electronic Resource
    8-Substituted Xanthines as Phosphodiesterase Inhibitors: Conformation-Dependent Lipophilicity and Structure-Activity RelationshipsPresented in preliminary from at the 7th European Symposium on Quantitative Structure-Activity Relationships, Interlaken, September, 1998. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 507-517 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 8-substituted xanthines 1-21 (including compound S 9795), caffeine (22), and the three isomeric dimethyl-xanthines 23-25 (see Table 1), were examined for their lipophilic behaviour using a reversed-phase HPLC technique. A number of flexible compounds showed a smaller-than-expected lipophilicity which based on conformational and tautomeric calculations were ascribed to the predominance of folded forms. A QSAR analysis of the phosphodiesterase-inhibitory potency of several compounds showed favourable factors to be a low lipophilicity and the absence of a substituent on the N7 position.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720314
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  • 5
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 9. A new useful approach to the epimers at C-7 and C-7,8 of N-acetylneuraminic acid (1988)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1988 (1988), S. 187-189 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to 5-acetamido-3,5-dideoxy-L-glycero-L-altro-2-nonulopyranosonic acid (6; 7,8-bis-epi-Neu5Ac) and 5-acetamido-3,5-dideoxy-D-glycero-L-altro-2-nonulopyranosonic acid (9; 7-epi-Neu5Ac) is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198819880215
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  • 6
    Electronic Resource
    Electronic Resource
    Racemattrennung von Propafenon und Diprafenon, Konfiguration der Propafenon-Enantiomeren (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 561-563 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical Resolution of Propafenone and Diprafenone, Configuration of Propafenone EnantiomersThe chiral antiarrhythmic drugs propafenone (rac-1) and diprafenone (rac-3) were resolved by fractional crystallization of the diastereoisomeric salts with optically active di-O, O′-p-toluoyltartaric acid and tartaric acid, respectively. Derivatization with (+)-1-phenylethyl isocyanate and analytical separation of the diastereoisomers 2 and 4 by HPLC confirmed the optical purity of the enantiomers. CD spectra of (+)- and (-)-propafenone as copper complexes established the absolute configuration: (-)-1 is R-, (+)-1 S-configurated.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870379
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  • 7
    Electronic Resource
    Electronic Resource
    Chemo-enzymatische Synthese von Kohlenhydraten: Die Herstellung von L-Xylose und 2-Desoxy-L-xylo-hexose (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 95-97 
    Details
    ISSN: 0170-2041
    Keywords: L-Xylose ; 2-Deoxy-L-xylo-hexose ; Enzymatic syntheses ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemo-Enzymatic Synthesis of Carbohydrates: The Preparation of L-Xylose and 2-Deoxy-L-xylo-hexoseA synthetic approach to L-xylose (6) and 2-deoxy-L-xylo-hexose (8) has been developed. The strategy utilizes achiral starting materials and employs two enzymatic reactions to introduce the desired chiral centers. Rabbit muscle aldolase (RAMA)-catalyzed condensation of (3-phenylthio)propanal (1) with dihydroxyacetone phosphate (DHAP) affords the C-6 skeleton 2 with D-threo configuration between C-3 and C-4. Diastereoselective reduction of 2 with sorbitol dehydrogenase (SDH) introduces the final stereocenter of the tetrahydroxy derivative 3. After oxidation of sulfide 3 to the corresponding diastereotopic sulfoxides 4, L-xylose (6) is obtained by thermal elimination of phenylsulfenic acid followed by ozonolysis. 2-Deoxy-L-xylo-hexose (8) is yielded from 4 by a Pummerer rearrangement and subsequent reductive deprotection (DI-BAL-H) of the rearrangement product 7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199219920119
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  • 8
    Electronic Resource
    Electronic Resource
    Thermisch instabile Allene, XI. Trichlorallencarbonitril und Trichlorallencarboxamid (1979)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1979 (1979), S. 1969-1976 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermally Unstable Allenes, XI.  -  Trichloroallenecarbonitrile and TrichloroallenecarboxamideThe synthesis of the thermally unstable title compounds 3 and 8 starting from the 2-hydroxy nitriles 1a, b via the nitriles 2a, b and the amide 5a is described. Dimerization of the allenes 3 and 8 occurs rapidly at room temperature giving 6 and 9, respectively. The amide 5a is available from the corresponding acid chloride, only when an excess of ammonia is meticulously avoided. Otherwise the allene 8 is formed, which rapidly adds ammonia. The resulting primary enamine 10 is very stable. Hydrolysis with hydrochloric acid leads to the β-oxocarboxamide 13. The ketoenol equilibrium 13 ⇌ 14 was characterized by 1H-NMR spectroscopy.
    Notes: Die Synthese der im Titel genannten thermisch instabilen Allene 3 und 8 aus den 2-Hydroxynitrilen 1a, b über die Nitrile 2a, b und das Amid 5a wird beschrieben. 3 und 8 dimerisieren bei Raumtemperatur rasch zu 6 bzw. 9. Das Amid 5a ist aus dem zugehörigen Säurechlorid nur zugänglich, wenn ein Ammoniaküberschuß peinlich vermieden wird. Andernfalls entsteht das Allen 8, das sehr rasch Ammoniak addiert. Das so erhaltene primäre Enamin 10 ist sehr stabil. Seine Hydrolyse mit Salzsäure liefert das β-Oxocarbonsäureamid 13. Das Keto-Enol-Gleichgewicht 13 ⇌ 14 wurde 1H-NMR-spektroskopisch charakterisiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197919791207
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  • 9
    Electronic Resource
    Electronic Resource
    Aminosäuren, 6. Untersuchungen zur Synthese von L-Saccharopin (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1030-1043 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amino Acids, 6. - Investigations on the Synthesis of L-SaccharopineN-Alkyl-5-oxoproline esters 4 or 6 are obtained by alkyl desilylation of N-trimethylsilyl-5-oxoproline esters 2 with 6- or 2-halohexanoates 3, 5 in the presence of KF and [18]crown-6. The higher reactivity of the 2-halo compounds 5 is established from competitive reactions of 2a with 3, 5 or the 2,6-dihalohexanoates 7, 8. Alkylation of 2a with methyl 6-bromo-2-phthalimidohexanoate (11), followed by removal of the phthaloyl group and hydrolysis, yields a mixture of the diastereomers pyrosaccharopine (13) and allosaccharopine (14a). - The optically pure hydroxyglutarates (2R)-15b and (2S)-15b are transformed into the respective triflates 18. These are treated with the Nα-protected lysine ester (S)-16b to give the esters 14b and 17b, which upon acid hydrolysis afford enantiomerically pure D-allosaccharopine (2R,5′S)-14a and L-saccharopine (2S,5′S)-14a.
    Notes: Alkyldesilylierung von N-Trimethylsilyl-5-oxoprolinestern 2 mit 6- bzw. 2-Halogenhexansäureestern 3 bzw. 5 führt in Gegenwart von KF und [18]Krone-6 zu den entsprechenden N-Alkyl-5-oxoprolinestern 4 bzw. 6. Kompetitive Umsetzungen von 2a mit 3 bzw. 5 sowie mit den 2,6-Dihalogenhexansäureestern 7, 8 zeigen eindeutig die höhere Reaktivität der 2-gegenüber den 6-Halogenverbindungen. Alkylierung von 2a mit 6-Brom-2-phthalimidohexansäure-methylester (11) ergibt nach Abspaltung der Phthaloylschutzgruppe und saurer Hydrolyse ein Diastereomerengemisch aus Pyrosaccharopin (13) und Allosaccharopin (14a). - Ausgehend von den enantiomerenreinen 2-Hydroxyglutarsäureestern (2R)-15b und (2S)-15b können über die Triflate 18 durch Umsetzung mit dem Nα-geschützten Lysinester (S)-16b die Ester 14b bzw. 17b hergestellt werden, die nach saurer Hydrolyse enantiomerenreines D-Allosaccharopin [(2R,5′S)-14a] bzw. L-Saccharopin [2S,5′S)-14a] ergeben.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860608
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  • 10
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 18. Synthesis of the side chain stereo and deoxy analogs of 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nononic acid (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1185-1195 
    Details
    ISSN: 0170-2041
    Keywords: Sialic acids ; Hemagglutinin inhibitors ; N-Acetylneuraminic acid, deoxygenation and epimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 5-acetamido-2,6-anhydro-3,5-dideoxy-D- erythro-L-manno-nonic acid (3b, 7,8-epi2-2-d-2-HeqNeu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5-dideoxy-L-threo-L-manno-nonate (6b, 8-epi-2-d-2-Heq-Neu5Ac) could be realized by transformation of 5-acetamido-3,5-dideoxy-L-glycero-L-altro-2-nonulopyranosonic acid (2a, 7,8-bis-epi-Neu5Ac) and 5-acetamido-3,5-dideoxy-3-L-glycero-D-galacto-2-nonulosonic acid (5a, 8-epi-Neu5Ac) into the corresponding peracetylated 2-chloro derivatives and subsequent catalytic hydrogenation. As this procedure could not be applied to the synthesis of the 7-epi, 7-deoxy and 8-deoxy derivatives a new strategy, which started with the methyl 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nonoate (1e), was designed. For this purpose, a gram-scale preparation of 1e was developed. Transformation of protecting groups and radical reduction of selectively introduced tolylthiocarbonate groups led to the corresponding 5-acetamido-2,6-anhydro-3,5,7-trideoxy-D-glycero-L-manno-nonoic acid (12b, 2,7-d2-2Heq-Neu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5,8-trideoxy-D-glycero-L-manno-nonate (11b, 2,8-d2-2Heq-Neu5Ac). An oxidation  -  reduction sequence yielded 5-acetamido-2,6-anhydro-3,5-dideoxy-D-threo-L-manno-nonoic acid (9c, 2d-2Heq-7-epi-Neu5Ac). Also the sialic acid analog 6b could be prepared according to this newly designed strategy.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001216
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