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  • Organic Chemistry  (6)
  • Alkynes  (1)
  • Sulfonamidosilanes  (1)
  • Wiley-Blackwell  (8)
  • 1995-1999  (8)
  • 1
    Electronic Resource
    Electronic Resource
    3′,4′-Diethynl-2′,3′,5′-trideoxy-5′-noruridine: A new self-polymerizable 2′-deoxyribonucleoside analogueDedicated to Prof. Dr. Richard Neidlein, Heidelberg, on the occasion of his 65th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1879-1886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In 10 steps, 3′,4′-diethynyl-2′,3′,5′-trideoxy-5′-noruridine (14) was synthesized in 5% overall yield from commercial uridine, using conventional methods of nucleoside chemistry. As two functional groups capable to react with each other are present in the same molecule, the synthetic compound is able to form polymers, similar to the polynucleotides, by an acetylene coupling reaction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780721
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  • 2
    Electronic Resource
    Electronic Resource
    New Synthesis and Chirality of (-)-4,4,4,4′,4′,4′-Hexafluorovaline (1998)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 182-186 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (-)-(R)-4,4,4,4′,4′,4′-Hexafluorovaline hydrochloride ((R)-5) of 98% ee is prepared from β,β-bis(trifluoromethyl)acrylic acid (= benzyl 4,4,4-trifluoro-3-(trifluoromethyl)but-2-enoate; 1) in 4 steps with an overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by anti-Michael addition of (+)-(R)-1-phenylethylamine (2) to 1 (→ (R,R)-3). In contrast to the published (S)-chirality, the X-ray structure analysis of (R,S)-6 reveals, that (R)-chirality has to be assigned to the levorotatory (-)-4,4,4,4′,4′,4′-hexafluorovaline hydrochloride.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19980810117
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  • 3
    Electronic Resource
    Electronic Resource
    Monoterpene Dimers from Lisianthius seemannii (1998)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 1393-1403 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new acylated dimeric secoiridoid glycoside, seemannoside A (2), has been isolated from the aerial parts of Lisianthius seemannii (GRISEB) O. KUNTZE (Gentianaceae). The structure was established by spectroscopic analysis (UV, MS, 1H- and 13C-NMR, and 2D-NMR experiments) and chemical reactions as (E-4′-O-p-coumaroyl)lisianthioside. The structure of the (Z)-isomer (seemannoside B, 3), also present in the plant, was confirmed by LC/UV/1H-NMR analysis. The active principle, 6, responsible for the antifungal activity of the apolar extract against Cladosporium cucumerinum, has been isolated. Its structure has been established by NMR spectroscopy and X-ray crystallographic analysis as a rare type of aglycone monoterpene dimer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19980810548
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  • 4
    Electronic Resource
    Electronic Resource
    Asymmetric Synthesis of (S)-5,5,5,5′,5′,5′,5′-Hexafluoroleucine (1998)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 174-181 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (S)-5,5,5,5′,5′,5′-Hexafluoroleucine ((S)-13) of 81 % ee is prepared from hexafluoroacetone (l) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α-keto ester 4 either by bakers' yeast (91 % ee) or by ‘catecholborane’ 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)-5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct (S,R)-9b of (2S)-N-[(R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine ethyl ester.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19980810116
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  • 5
    Electronic Resource
    Electronic Resource
    The Synthesis and Characterization of New Optically Active ‘dimeric’ ‘pineno’-[4,5]-fused 2,2′-bipyridines linked without spacer or by small spacer groups (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1192-1202 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linked chiral bipyridines 2-4 are prepared by combining two optically active ‘pineno’-[4,5]-fused 2,2′-bipyridines in a stereoselective reaction (Scheme 1). These potential ligands are new members of the ‘chiragen’ family, and are characterized by NMR spectroscopy and, in the case of 2 and 3 by single-crystal X-ray analysis. A new synthesis of ‘dipineno’-[4,5;4′,5′]-fused 2,2′ -bipyridine 8 is described, which, when coupled, gives additional four chiral centres to the analogous ‘chiragen’ series ( → 9). Analysis of the CD spectra allowed conformational information about the solution species to be determined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790425
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  • 6
    Electronic Resource
    Electronic Resource
    Topospecific Reactions of a [5.5.5.5]Fenestradiene with [Fe2(CO)9] (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 1169-1175 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N, N-Dimethylformamide dimethyl acetal transforms an allylic OH group, which is part of a tetracyclic hydrocarbon in a unique elimination reaction into a [5.5.5.5]fenestradiene (2b → 4). In topologically selective reactions of this diene 4 with [Fe2(CO)9,], the [Fe(CO)4(η2-diene)] and the [Fe(CO)3(η4-diene)] complexes 8 and 9, respectively, are formed by complexation on one side of the diene moiety, whereas complexation on the other side leads to a [Fe(CO)2(Cp)] complex 10.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800414
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  • 7
    Electronic Resource
    Electronic Resource
    Some Silatetraazaspiroalkanes with [4 + 4] Octacoordinated Silicon (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1967-1973 
    Details
    ISSN: 1434-1948
    Keywords: Sulfonamidosilanes ; [4 + 4] Octacoordinated silicon ; Capped tetrahedron ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spirocyclic compounds containing an Si(N)4 core have been prepared from 1,2-ethane- and 1,3 propanediamines bearing the electron-withdrawing p-toluenesulfonyl groups at the four N atoms. According to the X-ray structure analysis of the compounds 8a and 13, the spirocyclic rings are almost perpendicular to each other. In both cases a distorted dodecahedral arrangement of a [4 + 4] octacoordinate Si atom is found in which one O atom of each of the four sulfonyl groups caps one of the planes defined by the Si(N)4 tetrahedron. The O···Si distances are 2.85-3.02 Å and the two O···Si···O angles are 145-159°. According to the X-ray structure analysis of the monocyclic compound 16, one O atom of the p-toluenesulfonyl group caps the plane defined by O1-N2-C13 of the distorted S(N2)(O)C tetrahedron.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Tri- and Tetranuclear Mixed-Metal Clusters Containing Alkyne Ligands: Synthesis and Structure of [Ru3Ir(CO)11(RCCR′)]-, [Ru2Ir(CO)9(RCCR′)]-, and [HRu2Ir(CO)9(RCCR′)] (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 853-862 
    Details
    ISSN: 1434-1948
    Keywords: Cluster compounds ; Ruthenium ; Iridium ; Alkynes ; Butterfly structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrahedral cluster anion [Ru3Ir(CO)13]- (1) reacts with internal alkynes RC≡CR′ to afford the alkyne derivatives [Ru3Ir(CO)11(RCCR′)]-(2: R = R′ = Ph; 3: R = R′ = Et; 4: R = Ph; R′ = Me; 5: R = R′ = Me) which have a butterfly arrangement of the Ru3Ir skeleton in which the alkyne is coordinated in a μ4-η2 fashion. Under CO pressure they undergo fragmentation to give the trinuclear cluster anions [Ru2Ir(CO)9(RCCR′)]- (6: R = R′ = Ph; 7: R = R′ = Et; 8: R = Ph; R′ = Me; 9: R = R′ = Me), in which the alkyne ligand is coordinated in a μ3-η2 parallel fashion. Protonation of these trinuclear anions leads to the formation of the corresponding neutral hydrido clusters [HRu2Ir(CO)9(RC≡CR′)] (10: R = R′ = Ph; 11: R = R′ = Et; 12: R = Ph; R′ = Me; 13: R = R′ = Me). The protonation of the butterfly anions 2 and 3, however, gives rise to the formation of the neutral tetrahedral clusters [HRu3Ir(CO)11(RCCR′)] (14: R = R′ = Ph and 15: R = R′ = Et), respectively. The analogous clusters [HRu3Ir(CO)11(PhCCCH3)] (16) and [HRu3Ir(CO)11(CH3CCCH3)] (17) are only accessible from the reaction of the neutral cluster [HRu3Ir(CO)13] with the corresponding alkynes. The complexes 2, 4, 5, 6, 10, 12 and 15 are characterised by X-ray structure analysis.
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