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  • General Chemistry  (21)
  • Inorganic Chemistry  (4)
  • Occupational Health and Environmental Toxicology  (3)
  • 1
    ISSN: 0947-6539
    Keywords: ab initio calculations ; carboranes ; electron diffraction ; rearrangements ; structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: closo-1,2-(SiMe3)2-1,2-C2B4H4 undergoes thermal conversion to 1,6-(SiMe3)2-1,6-C2B4H4. The reaction pathway was monitored by 11B NMR spectroscopy. The structures of the 1,2- and 1,6-isomers were optimized at the HF/6-31 G* ab initio level. Gas-phase electron diffraction studies for both isomers are reported, as well as low-temperature X-ray crystal structure determinations. Comparison of calculated structural data with the data obtained experimentally shows good agreement between theory and experiment.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Diacylglycerolphosphates ; Glycophosphoinositol anchors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exploration of the molecular and structural basis for the sorting of GPI-anchored proteins is based on labeled partial structures of GPI′s which can be incorporated into the GPI anchor biosynthesis and cellular transport systems. To this end, from mannosyl donor 6 and the D-glucosaminyl-(1→6)-D-myo-inositol derivative 7 as acceptor, the pseudotrisaccharide 8 was prepared. Compound 8 was transformed into the GPI partial structures 5a,b which contain the pseudotrisaccharide ligated to two different phosphatidyl residues. Compounds 5a,b have Boc protection at the 2-amino group of the glucosamine residue (2b-position) and a free amino group at the 6b-position. The 6b-amino group was used for the ligation of the 3-(7-nitrobenzofurazan-4-yl)-aminopropanoyl group as a fluorescent label, the 5-azido-2-nitrobenzoyl and 4-azidophenylaminothiocarbonyl groups as photolabels, and the 4-azido-2-hydroxybenzoyl group as a radiolabel after the introduction of radioactive iodine by an electrophilic aromatic substitution. Thus, after acid-catalyzed removal of the protective groups, the unprotected target molecules 1-4 were obtained.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Sphingosines ; Ceramides ; Ceramide-1-phosphates ; Inositols ; Glycophosphosphingolipids, synthesis ; Glycophosphoinositol anchors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The readily available 2,3:4,5-di-O-cyclohexylidene-D-myo-inositol derivative 3 was converted into the 1-O-unprotected D-myo-inositol derivative 6. Reaction with the phosphite derivative 7 of 3-O-tert-butyldimethylsilyl-protected ceramide furnished the target molecule D-erythro-ceramide-1-phosphoinositol (1). Reaction of O-(3,4,6-tri-O-acetyl-2-azido-β-D-glucopyranosyl)trichloroacetimidate (20) with 3 gave exclusively α(1→6)-connected glycoside 21 which was converted into the 1α-O-unprotected derivative 24. Reaction with the D-erythro-azidophytosphingosine-derived ceramide-1-phosphite derivative 17 led, after oxidation and removal of the cyanoethyl group, to protected 2-azido-D-glucopyranosyl-α(1→6)-D-myo-inositol-1-phospho-ceramide (25) which could be fully deprotected in two steps to afford the target molecule, the ceramide derivative of 2-amino-2-deoxy-D-glucopyranosyl-α(1→6)-D-myo-inositol-1-phosphate (2).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1153-1165 
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Sphingosines ; Ceramides ; Ceramides-1-phosphates ; Glycosylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -For the design of a synthesis of target molecule 1 the retrosynthetic analysis yielded building blocks 2-5, of which ceramide 2-phosphite derivative 2 and aminoethyl phosphite derivative 5 are known. The generation of α-glucosaminyl (1→6)inositol building block 3 was based on pseudodisaccharide 6 which was selectively benzoylated at 6b-O and then selectively benzylated at 3b-O to give 3. The synthesis of tetramannosyl building block 4 started from known ortho ester derivative 8 which was transformed into versatile mannosyl donors 13 and 18 and into acceptor 22. Reaction of 13 with 22 gave α-disaccharide 23, deacetylation and then mannosylation with 18 gave trisaccharide 25; ensuing deacetylation and mannosylation with 13 gave tetrasaccharide 27; deallylation, acetylation, regioselective removal of the anomeric O-acetyl group and treatment with CCl3CN/DBU afforded 4. Glycosylation of 3 with donor 4 led to pseudohexasaccharide 31 in high yield. Replacement of the O-acyl groups by O-benzyl groups and then exchange of the menthyloxycarbonyl group by an O-acetyl group gave 36 which enabled regioselective attachment of 2 and 5. To this end, the 6e-O-silyl group was removed and then the aminoethyl phosphate residue was attached with reagent 5 to give 38 in high yield. 1a-O-Deacetylation and then reaction with 2 afforded 40 as fully protected 1 which was liberated in two steps; treatment with acid removed all acid labile protective groups and finally catalytic hydrogenation afforded the desired GPI anchor 1 which could be fully structurally assigned.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 360 (1968), S. 15-24 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions between K3[Cr(NCS)6] and sec. and tert. phosphines R2R′P (R, R′ = H, alkyl, cycloalkyl or/and aryl) are investigated. Depending on the rests at the P atom, different types of complexes are formed: (R2R′PH)3[Cr(NCS)6], (R2R′PH)2[Cr(NCS)5 (R2R′P)], and (R2R′PH)[Cr(NCS)4(R2R′P)2], respectively. With [(C6H5)4P]NO3 the corresponding tetraphenylphosphonium salts are prepared.
    Notes: Die Umsetzung von K3[Cr(NCS)6] mit verschieden-subst. sek. und tert. Phosphinen R2R′P (R, R′ = H. Alkyl, Cycloalkyl oder/und Aryl) wird untersucht. In Abhängigkeit von den Organoresten am P-Atom entstehen Verbindungen des Typs (R2R′PH)3[Cr(NCS)6], (R2R′PH)2[Cr(NCS)5(R2R′P)] bzw. [(R2R′P)] bzw. (R2R′PH)[Cr(NCS)4(R2R′P)2]. Mit [(C6H5)4P]NO3 sind daraus die entsprechenden Tetraphenylphosphoniumsalze erhältlich.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 330 (1964), S. 295-308 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: pK′ values of carbethoxyalkylphosphines, carbamidoalkylphosphines and carboxy-alkylphosphines of the general formula R2P—R′—COR″ (R″ = —OC2H5, —NH2, and —OH, respectively) are determined potentiometrically using water - ethanol or water as the solvent.The basicity of the P atom in these compounds depends on the kind of R (alkyl, cycloalkyl or aryl group) and R′ (linear or branched alkylene group) and is influenced by the position of the COOC2H5, CONH2 and COOH group, respectively.IR and NMR spectra of the carboxyalkylphosphines indicate no dipolar structure of these P-analogous amino acids.
    Notes: In Fortsetzung einer früheren Arbeit(2) werden durch potentiometrische Titration in Äthanol-Wasser bzw. Wasser die pK′-Werte der Carbäthoxyalkylphosphine R2P—R′—COOC2H5, der Carbamidoalklphosphine R2P—[CH2]n—CONH2 und der Carboxyalkylphosphine R2P—R′—COOH bestimmt.Die Basizität des P-Atoms dieser Verbindungen der allgemeinen Formel R2P—R′—COR″ wird durch die Art der Gruppen R und R′ beeinflußt (R = Alkyl-, Cycloalkyl- oder Arylgruppe; R′ = lineare oder verzweigte Alkylengruppe) und hängt von der Stellung der COR″-Gruppe ab.Aus IR- und NMR-Spektren folgt, daß die den Aminosäuren im Formeltyp entsprechenden Carboxyalkylphosphine weder in fester Form noch in THF-Lösung eine dipolare Struktur besitzen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 362 (1968), S. 191-204 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Both the diffuse-reflectance spectra of the complexes [Cr(NCS)4 (R2R′P)2]- - R, R′ = H, alkyl, cycloalkyl. aryl - and the solution spectra in methanol and acetone were recorded. The observed ligand field bands are interpreted by the usual theoretical procedures and a spectrochemical series for these compounds is given. The dependence of Dq on the P-substituents is discussed. From the visible spectrum of [Cr(NCS)4{C2H5(C6H11)2P}2]- the transconfiguration follows.
    Notes: Die sichtbare und UV-Spektren der Tetra-isothiocyanato-diphosphino-chromate(III) [Cr((NCS)4)(R2R′P)2]- - R, R′ = H, Alkyl, Cycloalkyl, Aryl - werden in Lösung (Methanol, Aceton) und Reflexion angegeben, die Banden zugeordnet, aus den beobachteten d--d-Übergängen die Parameter Dq bzw. B der halbempirischen Theorie berechnet sowie eine spektrochemische Serie dieser Verbindungen aufgestellt. Die Abhängigkeit der Ligandenfeldstärke von den Phosphor-Substituenten wird diskutiert. Für [Cr(NCS)4{C2H5(C6H11)2P}2]- folgt aus dem sichtbaren Spektrum die trans-Konfiguration.
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0947-6539
    Keywords: electronic structure ; frontier orbitals ; metalloporphyrins ; radical cations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of magnesium and zinc tetraarylporphyrins and their porphyrinoxidized derivatives were studied by UV/Vis, ESR, and resonance Raman spectroscopy at various temperatures. The series included tetra(meta-dichlorophenyl)porphyrinatozinc (5), tetra(ortho-dichlorophenyl)porphyrinatozinc (6), tetra(ortho-difluorophenyl)porphyrinatozinc and -magnesium (9 and 10), and tetra(pentafluorophenyl)porphyrinatozinc and -magnesium (7 and 8). The radical cations (3a-10a) were isolated by chemical one-electron oxidation of their neutral precursors (3-10). Despite the structural similarity of all these radicals, their electronic ground state varied within the series. The position of the chloro groups was found to play a key role. While the radical cation of the meta-dichloro-substituted derivative 5a exhibited A2u spectroscopic features, the ortho-dichlorophenyl derivative (6a) showed A1u spectral features. Radicals of the fluoro-substituted porphyrins, especially that of 10, were found to have state-admixed (A1u/A2u) electronic structures, and the relative contributions of the two states was found to vary with temperature and to depend on the axial ligand. The results indicate that the fluoro-substituted porphyrins are primarily A2u at low temperature, even though their room temperature spectroscopic features resemble those of A1u cations. The elucidation of factors that affect the electronic structures of the radicals in the present series is helpful in providing a greater understanding of the spin-spin interactions in the intermediates of heme-dependant enzymatic reactions and their synthetic analogues.
    Additional Material: 5 Ill.
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  • 9
  • 10
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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