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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of Hetaryl Glycosides and Their Glycosyl Donor Properties (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1353-1360 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Substitution ; Carbohydrates ; Anomeric O-hetarylation ; Glycosylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Anomeric O-hetarylation of tetra-O-benzyl- and tetra-O-acetylglucose (1a, b) can be directly performed with electron-deficient heteroaromatic/heterocyclic systems 2-14, which contain imide halide moieties. The reactions were carried out in the presence of a base and led, through an exchange of the halide by the glucopyranosyloxy moiety, to the products 2a-14a, 7b-14b. Predominantly or exclusively β-products were obtained. Systems bearing more than one imide halide moiety, such as cyanuric fluoride (15) or 5-chloro-2,4,6-trifluoropyrimidine (16), can be employed for successive anomeric O-hetarylations. Investigation of the glycosyl donor properties of O-glucosyl heteroaromatic imidates with 6-O- and 4-O-unprotected glucose derivatives 18 and 19 as acceptors and comparison of the results obtained with data for the corresponding β-trichloroacetimidates 17aβ and 17bβ, reveals that 2,3,5,6-tetrafluoropyridin-4-yl glucopyranosides 14aβ and 14bβ exhibit similar properties. For specific tasks, for instance α-glucopyranoside formation, 14aβ may even be advantageous.
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  • 2
    Electronic Resource
    Electronic Resource
    Zur Struktur zweier Arsen- und Antimontricarboxylate (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 461-468 
    Details
    ISSN: 1434-4475
    Keywords: Coordination of As(III) and Sb(III) ; Structure ; Enantiomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary Arsen-tris(2,2-dimethylpropionate) (1) crystallizes monoclinic in the space group P21/n witha=926.2,b=2158.6,c=983.7 pm, β=94.92°, andZ=4. As has a coordination number of 3+3. Antimony tripropionate (2) crystallizes monoclinic in the space group P21/c witha=930.2,b=863.0,c=1575.2 pm, β=90.27, andZ=4. The molecules are bridged to chains; therefore, Sb reaches the coordination number 3+3 (+3).
    Notes: Zusammenfassung Arsen-tris(2,2-dimethylpropionat) (1) kristallisiert monoklin in der Raumgruppe P21/n mita=926.2,b=2158.6,c=983.7 pm, β=94.92° undZ=4. As hat gegenüber O die Koordinationszahl 3+3. Antimontripropionat (2) kristallisiert monoklin in der Raumgruppe P21/c mita=930.2,b=863.0,c=1575.2 pm, β=90.27 undZ=4. Die Moleküle sind intermolekular zu Ketten verknüpft, wodurch Sb die Koordinationszahl 3+3 (+3) erreicht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807070
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  • 3
    Electronic Resource
    Electronic Resource
    Kristall- und Molekülstruktur von Arsen-tris(trifluoracetat) (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 1215-1220 
    Details
    ISSN: 1434-4475
    Keywords: Coordination of As(III) ; Structure ; Stereoisomeres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary Arsenictris(trifluoroacetate) (1) crystallizes monoclinic in the space group Cc witha=1229.3,b=1697.9,c=1243.5 pm, β=110.01°, andZ=8. The trifluoroacetic acid ions acts as chelating ligands. Additionally they are bridging crystallographic independent molecules. As has a coordination number of 3+3(+2). The unit cell contains two sets of chirameres.
    Notes: Zusammenfassung Arsen-tris(trifluoracetat) (1) kristallisiert monoklin in der Raumgruppe Cc mita=1229.3,b=1697.9,c=1243.5 pm, β=110.01° undZ=8. Die Trifluoracetatanionen fungieren gegenüber As als zweizähnige Liganden und verknüpfen die beiden kristallographisch unabhängigen Moleküle zusätzlich intermolekular. As erreicht dadurch gegenüber O die Koordinationszahl 3+3(+2). Die Elementarzelle enthält zwei Sätze von chirameren Molekülen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807787
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  • 4
    Electronic Resource
    Electronic Resource
    Antimontribenzoat (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 1045-1050 
    Details
    ISSN: 1434-4475
    Keywords: Coordination of Sb(III) ; Structure ; Enantiomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The Δ isomer of (C6H5CO2)3Sb crystallizes rhombohedrally (hexagonal axes) in the space group R3 witha=1944.0 pm,c=422.3 pm, andZ=3. The molecules are stacked parallel to 001; Sb has a coordination number of 3+3 (Sb-O: 208 and 256 pm, resp.).
    Notes: Zusammenfassung Das Δ-Isomer des Antimontribenzoats kristallisiert rhomboedrisch (hexagonale Aufstellung) in der Raumgruppe R3 mita=1944.0 pm,c=422.3 pm undZ=3. Die Moleküle sind parallel zu 001 gestapelt. Sb hat gegenüber O die Koordinationszahl 3+3 (Sb-O: 208 bzw. 256 pm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811375
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis, Structure and Hydrolysis Studies of Dimethyltris(Trimethylsilyl)Methylmetallanes of Aluminium and GalliumDedicated to Professor Manfred Weidenbruch on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1783-1792 
    Details
    ISSN: 0947-6539
    Keywords: aluminium ; gallium ; hydrolyses ; Si ligands ; structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of [(Me3Si)3CLi2thf] with Me2MCl (M = Al, Ga) afford the mixed trialkylmetallanes [(Me3Si)3-CAlMe2·thf] (1) and [(Me3Si)3 CGaMe2·thf] (2) in high yields. The coordinated THF molecule of compound 2 can be removed by sublimation in vacuo to yield the solvent-free product [(Me3Si)3-CGaMe2] (3). Hydrolysis of compound 2 with one equivalent of water at 0°C gives the trimeric hydroxide [{(Me3Si)3CGaMe(μ-OH)}3] (4), while the reaction with two equivalents of water at room temperature yields the unusually stable gallium hydroxide-water complex [{(Me3Si)3CGaMe(OH)(μ-OH)MeGaC(SiMe3)3) H2O·2thf] (6). On heating, compound 6 is converted to the hydroxide [{(Me3Si)3C}4Ga4(μ-O)2(μ -OH)4] (5), which has a heteroadamantane-like core. The hydrolysis of compound 1 with one equivalent of water at - 25°C gives the dimeric hydroxide [{(Me3Si)3CAlMe(μ-OH)}2·2thf] (7), while the reaction with two equivalents of water results in the formation of the novel hydroxide [{(Me3Si)3C}4Al4(μ-O)2 (μ-OH)4] (8), which is isostructural to the gallium compound 6 with the adamantane-like structure. The molecular structures of compounds 1, 2, 4, 5·3THF, 6, 7 and 8·0.5 THF have been determined by X-ray structure analysis. Compound 7 is the first structurally characterised aluminium hydroxide containing methyl groups, and 8 is the smallest structurally characterised galloxane hydroxide described in literature.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031109
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  • 6
    Electronic Resource
    Electronic Resource
    Chiral Amide Rotaxanes with Glucose Stoppers - Synthesis, Chiroptical Properties and Wheel-Axle Interactions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2003-2007 
    Details
    ISSN: 1434-193X
    Keywords: Supramolecular chemistry ; Rotaxanes ; Mechanical bond ; Molecular recognition ; Chirality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we report on amide rotaxanes with tetrabenzoylglucose stoppers. When acetyl groups are used instead of benzoyl groups, merely a pseudo-rotaxane 5 is obtained. The circular dichroism measurements of the rotaxanes 6a and 6b differ significantly from that one of the free axle 7. Similarly, the Cotton effects of the mixtures of achiral wheels 2a and 2b and chiral axle indicate intermolecular host-guest interactions, likewise. After an addition of a solution of NaOMe the wheel is slipping off immediately and quantitatively by hydrolysis, as the benzoylglucose stoppers decrease in size by hydrolysis.
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  • 7
    Electronic Resource
    Electronic Resource
    η5-Pentamethylcyclopentadienyliridium(III) and -rhodium(III) Labeling of Amino Acids with Aromatic Side Chains - The Importance of Relativistic Effects for the Stability of Cp*Irııı Sandwich Complexes (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1991-1998 
    Details
    ISSN: 1434-1948
    Keywords: Iridium ; Rhodium ; Amino acids ; Sandwich complexes ; Bioorganometallic chemistry ; Relativistic effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: η5-Pentamethylcyclopentadienyliridium(III) and -rhodium(III) sandwich complexes of the type [(η5-Cp*)M(η6-aa)](CF3SO3)2 (M = Ir, Rh; 3-14) containing L-tyrosine, L-tryptophan and L-phenylalanine derivatives (aa) can be prepared by treatment of [(η5-Cp*)ML3] (CF3SO3)2 [L = thf, (CH3)2CO, CH3CN] with the appropriate bioligand in thf for N-protected compounds and in CF3COOH for α-amino acids with unprotected amino groups. Coordination to the Cp*MIII fragments stabilizes the ketonic form of the tyrosine aromatic side chains, leading to a marked enhancement in the acidity of the p-hydroxy function. The crystal structure of [Cp*Ir(ActyrOMe)] (CF3SO3)2 (3b, ActyrOMe = N-acetyltyrosine methyl ester) confirms a marked distortion towards an η5-oxohexadienyl coordination mode as may be gauged from the tilting of the p-OH plane C13/C14/C15 by no less than θ = 12.9° from that of the remaining ring atoms. Facial isomers are present in an effective 1:1 ratio for all tryptophan derivatives. Whereas the Cp*IrIII sandwich complexes of aromatic α-amino acids are stable in polar solvents, rapid decay is observed for analogous Cp*RhIII complexes of N-unprotected derivatives in polar solvents. Comparative nonrelativistic and relativistic all-electron density functional calculations on the cationic sandwich complexes [Cp*M(η6-C6H5Me)]n+ (n = 2, M = Ir, Rh; n = 1, M = Ru) confirm that all three metals bind more tightly to Cp* than to toluene as gauged by the respective force constants (k1 〉 k2). A much larger relativistic enhancement of k2 for M = Ir (279 vs 207 Nm-1) could be responsible for the greater stability of Cp*IrIII complexes in solution.
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of the Se Atom Distribution in the Layered Compound Nb3(Se1-xIx)I7 by Scanning Tunneling Microscopy (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 785-787 
    Details
    ISSN: 1434-1948
    Keywords: Atom distribution ; Mixed crystals ; Scanning tunneling microscopy ; Layered compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The layered compound Nb3(Se1-xIx)I7 is obtained when the I atoms at the face-capping sites of the layered compound Nb3I8 are replaced by Se atoms. The amount and distribution of the Se atoms in Nb3(Se1-xIx)I7 were examined by scanning tunneling microscopy. The analysis shows that the distribution of the Se atoms is completely random.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Asymmetric Synthesis of β-Methylated Aliphatic Ketones via Lithiated 3-[(S)-2-(Methoxymethyl)pyrrolidino]hex-3-ene⋆ (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1371-1377 
    Details
    ISSN: 1434-193X
    Keywords: Homoenolate equivalents, chiral ; Alkylation ; 1-Aminoallyl anions, chiral ; β-Methyl ketones, chiral ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Substituted aliphatic ketones 10 have been obtained in excellent optical yields by alkylation of the aminoallyllithium compound endo-8, a homoenolate equivalent of hexane-3-one, using prolinol ether (SMP) as the chiral auxiliary. The intermediate endo-8 was generated by tin-lithium exchange of the 3-stannylated enamine 7a with butyllithium. An improved hydrolysis procedure for the resulting enamines is described. Some mechanistic implications with respect to the formation as well as the alkylation of endo-8 are discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    A Novel and Efficient Route towards α-GalNAc-Ser and α-GalNAc-Thr Building Blocks for Glycopeptide Synthesis (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1167-1171 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Glycals, nitro ; Michael additions ; Glycosylations ; Glycosides, galactosamine ; Reduction, nitro group ; Glycopeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Michael addition of serine and threonine derivatives 4a-4c to 3,4,6-tri-O-benzyl-2-nitro-D-galactal (1) afforded the corresponding 2-deoxy-2-nitro-α-D-galactopyranosides 5a-5c in good yield and stereoselectivity. 2-deoxy-2-nitroglycosides 5a and 5b were reduced to the 2-acetamido compounds by platinized Raney nickel T4. Manipulation of the protecting groups afforded known N-Fmoc-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-serine (8a) and -threonine (8b), valuable building blocks for O-glycopeptide synthesis.
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