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  • 1975-1979  (29.601)
  • 1830-1839  (3.956)
  • Chemistry  (33.368)
  • Biochemistry
  • pharmacokinetics
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Erscheinungszeitraum
Jahr
  • 101
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 3077-3087 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present evidence for structures of two ordered forms of polyxanthylic acid based on ir spectroscopy, pH titrations, and thermal transitions. Over the pH range ∼6-9.5, the structure is a four-stranded helix with alkali metal ions specifically complexed in the central channel. These internal counterions stabilize the structure by complexing with carbonyl oxygens and by partial screening of electrostatic repulsion caused by ionization of the xanthine residues in this pH range. Below pH 5, the structure is quite different and much more stable. Our data are consistent with a six-stranded helix in which both carbonyl oxygens and both NH protons are hydrogen bonded.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 102
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 87-94 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 103
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 96-96 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 104
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 111-117 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 105
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 97-110 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dies ist Teil I einer zweiteiligen Aufsatzfolge. Teil II wird „Neuentwicklungen der Düngemittelforschung“ behandeln und im nächsten Heft erscheinen.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 106
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 127-128 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 107
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 126-126 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 108
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 147-156 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 109
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 163-163 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 110
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 176-183 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 111
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 198-198 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 112
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 113
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An ir-absorption and Raman-scattering study, in the solid state, has been carried out on monodispersed, N- and C-protected homooligopeptides (number of residues, n, from 2 to 7) of L-valine, L-isoleucine, and L-phenylalanine. The amide I, II, III, V, and vNH regions have been examined. Some deuterated (ND) samples have been examined to complete the assignments. L-Phenylalanine dipeptide displays spectral characteristics compatible with the parallel β-structure; L-isoleucine and L-valine dipeptides are probably in a distorted structure. A mixture of parallel and antiparallel extended chains cannot be excluded for the peptides with n = 3. In the amide I region the spectra of peptides with n ≥ 4 show the existence of the β-conformation. The problem of chain orientation within the pleated-sheet structure is discussed on the basis of a recent theoretical treatment of vibrational interactions of the amide I mode.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 114
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stepwise synthesis and conformational studies of the N-terminal helical partial sequence of the membrane-modifying polypeptide antibiotic alamethicin are described. The polyoxyethylen esters of the fragments N-t-Boc-L-Pro-Aib-Ala-Gln-Aib-Val-Aib-Gly-OH and N-Ac-Aib-L-Pro-Aib-Ala-Aib-Ala-Gln-Aib-Val-Aib-Gly-OH are synthesized using polyoxyethylene (molecular mass 10,000) as solubilizing support. CD spectra of each intermediate in ethanol show α-helix formation of the N-protected peptide polymers beginning with the nonapeptide and of the N-protonated sequences beginning with the decapeptide. Compared to the helix of alamethicin, temperature- and solvent-dependent CD measurements indicate analogous conformational behavior. The results suggest that in lipophilic media the alamethicin helix can extend the full length of the partial sequence between the two proline residues and that aqueous media favor an increase of random-coil conformation.For model studies of the particular lipid interaction of alamethicin, the stepwise synthesis of peptides with the alternating (Aib-L-Ala)n sequence (n = 1-7) was carried out on a polyoxyethylene support (molecular mass 6000). CD and ORD studies in ethanol showed a change from the random coil to a right-handed α-helix with increasing peptide length. This change is observed for the N-protected peptides at a chain length of 8 residues and for the N-protonated peptides at a length of 9 residues. The comparison of the CD data of free and polyoxyethylene-bound peptides revealed that the solubilizing polymeric support cannot induce conformational changes. The intensities of the CD bands of t-Boc-(Aib-L-Ala)n-OPOE (n ≥ 6) are higher than those of alamethicin, and these model peptides show similar temperature and solvent inducible changes of their helix contents.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 115
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 116
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 539-552 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The three-dimensional structure of putrescine diphosphate has been solved by x-ray diffraction analysis. The structure reveals the detailed interaction between the amino groups of putrescine and the phosphate residues in which hydrogen bonding and electrostatic forces play a predominant role. The structure serves as a useful model for understanding the interaction of amines with nucleic acids both in a sequence-specific and non-sequence-specific fashion. In particular, a model is proposed for the interaction of the E-amino group of lysine with regions of DNA containing adenine-thymine sequences.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 117
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 609-623 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general model for the large-scale, time-independent structure of duplex DNA is developed based on elastic considerations. The general conditions of elastic equilibrium are given. These equations are solved for the equilibrium shape of stressed duplex DNA, based on the assumption that the double helix behaves mechanically as a symmetric, linearly elastic rod. It is shown that, in general, two orders of superhelicity will arise at equilibrium. Several possible applications of this approach to the supercoiling of closed circular DNA are described.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 663-680 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Temperature-dependent conformational transitions of deoxyoligonucleotides have been monitored by measuring 31P chemical shifts, spin-lattice relaxation times (T1), and 31P-{H} nuclear Overhauser enhancements (NOEs). The measured NOE ranged from 30 to 80%, compared to the theoretical maximum of 124% for a dipolar relaxation mediated by rapid isotropic rotation. The observed 3′-5′ phosphate diester 31P T1 showed a similar temperature dependence over the range 2-75°C for both double- and single-stranded oligonucleotides, and for dinucleotides. The results show that dipole-dipole interactions dominate the internucleotide phosphate relaxation rate in oligonucleotides. The same is true of terminal phosphate groups at low temperature; but at higher temperature another process, possibly due to contamination by paramagnetic ions, becomes dominant. The rotational correlation time τR calculated from the dipole-dipole relaxation rate of the internucleotide phosphate in d(pA)2 at 16°C is τR = 5.0 × 10-10 sec, implying a Stokes radius for isotropic rotation of 7.6 Å. The T1 and NOE values for the double-helical octanucleotide d(pA)3pGpC(pT)3 are consistent with dominance of dipole-dipole relaxation and isotropic rotation of a sphere of radius 14 Å, a reasonable dimension for the double helix. Activation energies for the rotation of dinucleotides range from 4 to 6 kcal/mol, close to the value of 4 kcal/mol expected for isotropic rotation. In order to test the possible effect of internal motion of correlation time τG on the results, we considered a model in which the nucleotide chain rotates about the P-O bonds. Comparison of the calculation with our experimental results shows that internal motion with τG ≅ 10-9 sec, as found from other studies to be present for large nucleic acids, would not influence out T1 and NOE values enough to be distinguished from isotropic rotation. However, we can conclude that τG cannot be as fast as 10-10 sec, even for dinucleotides.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 119
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 739-742 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 120
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 757-763 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements have been made of the high-resolution nmr spectra of the polyamino acids poly[N5-(2-hydroxyethyl)-L-glutamine] and poly[N5-(4-hydroxybutyl)-L-glutamine] in mixed deuterium oxide and water solvent at varying pressures from 1.03 to 3163.7 kg/cm2. The results are compared with previously reported results for the polymer poly[N5-(3-hydroxypropyl)-L-glutamine] under similar conditions. The significance of the behaviour of the polymers is considered in terms of the effect of the presence of hydrophobic residues in their side chains.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 121
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 765-788 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Exact solutions are obtained for the time dependence of the extent of irreversible binding of ligands that cover more than one lattice site to a homogeneous one-dimensional lattice. The binding may be cooperative or noncooperative and the lattice either finite or infinite. Although the form of the solution is most convenient when the ligand concentration is buffered, exact numerical or approximate analytical solutions, including upper and lower bounds, can be derived for the case of variable ligand concentration as well. The physical reason behind the relative simplicity of the kinetics of irreversible as opposed to reversible binding in such systems is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 887-898 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preparation of lamellar single crystals of mannan[poly((1 → 4)-β-D-mannose)] is described. Electron diffractograms clearly identify the perpendicular orientation of the chain axis with respect to the lamellar surface. Since the degree of polymerization is 40 or less, no conclusion is made as to chain folding. The unit cell corresponds to the mannan I structure derived from x-ray fiber data on oriented algal mannan. The baseplane dimensions found were a = 7.22 Å and b = 8.92 Å, and the systematic absences observed confirm the proposed P212121 group. It was found that cellulose microfibrils from Valonia ventricosa and bacterial cellulose could serve as extended chain nuclei for inducing oriented crystallization of mannan on cellulose. This produces a shish-kebab type of morphology.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 123
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 939-957 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general approach to the problem of molecular conformation is advanced. We describe a formalism that permits experimental and theoretical information to be incorporated into a set of upper and lower bounds on intramolecular distances. Structures (conformations) meeting these bounds can be readily generated and compared with each other. To illustrate the use of the method, we have employed a simple “firehose” model for protein folding to predict the long-range hydrophobic interactions in a small protein: pancreatic trypsin inhibitor. Models of this type lead to the proper hairpin turns and a reasonable set of long-range contacts for this protein. Application of the distance geometry method then yields backbone conformations with errors of 4-8 Å compared to the native structure. We discuss both the merits and shortcomings of the firehose model and the relation between distance geometry and energy minimization techniques.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 124
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1009-1019 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: CD spectra of calf thymus, C. perfringens, E. coli, and M. luteus DNA have been measured in the vacuum-uv region to about 168 nm for the A-, B-, and C-forms. The positive band at about 187 nm and the negative band at about 170 nm found for each type and form of DNA are sensitive to the source of the DNA and the base-base interactions of the double-stranded helix. The A-form spectra confirm that these bands are indeed sensitive to secondary structure. In the near-uv, the CD of B-form DNA is well analyzed as a linear combination of 27% A-form and 78% C-form. However, an analysis of the extended spectrum demonstrates that the near-uv analysis is not correct. The extended analysis shows that the base-base interactions are similar for B- and C-forms in solution, which implies that these two forms have nearly the same number of base pairs per turn. Various types of CD difference spectra are also discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 125
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H-nmr spectra of co-oligopeptides of tryptophan and glycine with structure H-Gly-Trp-(Gly)n-Trp-Gly-OH (n = 0-2) and those of several di- and tripeptides have been recorded at 360 MHz with CD3OD solutions containing 0.1N NaOD. The assignment of resonance signals was generally possible by comparing the spectra of structurally related peptides with each other. In order to solve the remaining ambiguities in the assignment, H-(αL,βS)(α,β-d2)Trp-OH, H-Trp-(αL,βS)(α,β-d2)Trp-OH, and H-Trp-(δ1,ε2,ζ2,ζ3,η2-d5)Trp-OH have been prepared and their spectra compared with those of the undeuterated compounds. The distribution of rotamers around the χ1 and (in two cases) χ2 torsion angles of the side chains has been obtained from the vicinal coupling constants 3JHαHβ and from the long-range coupling constants 4JHβHδ1. These data and an analysis of the chemical shifts of the Gly-Cα protons suggest that the orientation of the aromatic side chain is influenced by the following order of decreasing interaction with the functional groups at N- and C-side: -NH2 〉 -NHCO- 〉 -CONH-〉 -COO-. This rule does not hold for the second Trp residue of di- and tripeptides containing the -Trp-Trp- sequence, which has tentatively been attributed to steric effects.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 126
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1709-1725 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The number of constraint turns is defined as the number of bound unwinding ligands converted in turns necessary to relax the energy stored in a supercoiled DNA. It is equal to the sum of the twist and of the writhing and is interpreted geometrically. The twist is shown to be related to the derivative of the energy of superhelix formation with respect to the constraint turns. This leads to a semiempirical evaluation of the variation of the conformational energy with the writhing and of the writhing number. The bending contribution to the conformational energy is estimated independently using first-order elasticity. The variation of the twist and of the writhing with the constraint is, in this model, catastrophic. In particular, the writhing number jumps between intervals of allowed values.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 127
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements of translational diffusion coefficients by quasielastic laser light scattering, sedimentation coefficients, and intrinsic viscosities at zero shear of proteoglycan subunit fraction A1-D1-D1 isolated from bovine nasal septa are reported. Molecular weights and hydrodynamic dimensions are compared with those expected on the basis of structural models previously proposed. Comparison of the concentration dependence of the diffusion coefficient in the presence of NaCl and GdnHCl leads to the conclusion that significant self-association behaviour of subunit occurs in the absence of GdnHCl. In the absence of added salt, anomalous nonlinear concentration dependence of Dt estimated from wide-angle light-scattering experiments is observed. In addition, Dt apparently becomes angle dependent. These results are interpreted in terms of the perturbation of normal translational diffusion of the monomer by strong repulsive intermolecular interactions due to the combined effects of long-range electrostatic forces and macromolecular congestion at higher concentrations. By carrying out experiments at small scattering angles, it is possible to determine Dt0 for proteoglycan subunit in the absence of supporting electrolyte. Titration of a dilute solution of subunit with hyaluronic acid results in a sigmoidal behaviour of the Stokes radius, indicating the formation of complexes of higher molecular weight results from the noncovalent association of proteoglycan subunits with hyaluronate. Observation of Dt appears to provide a useful method for studying the proteoglycan subunit-hyaluronate interactions.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 128
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence is presented which shows that hemoglobin S in sickle cells has a tendency to aggregate even in the oxygenated state. The basis for that conclusion is derived from 13C-nmr rotating-frame spin-lattice relaxation studies in the presence of an off-resonance radiofrequency field in which the carbonyl resonances of hemoglobins in erythrocytes are examined. The experiments indicate that the rotational correlation time of hemoglobin S in oxygenated sickle cells at 38°C is 130 nsec compared to a value of 95 nsec for hemoglobin A in normal erythrocytes at the same temperature and the same mean cell hemoglobin content.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 129
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence, CD, absorption, and 1H-nmr studies are reported for complexes of 7-amino-actinomycin D with deoxydinucleotides, deoxytetranucleotides, and poly(dG-dC)· poly(dG-dC). The optical spectra for the 7-amino-actinomycin D complex with pdG-dC, pdG-dC-dG-dC and pdC-dG-dC-dG are similar in shape to the 7-amino-actinomycin D complex with either DNA or poly(dG-dC). The changes in the 1H chemical shifts of the 7-amino-actinomycin D and the pdG-dC resonances that accompany complex formation show that 7-amino-actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The magnitudes of the induced chemical shifts for the 7-amino-actinomycin D complex formation with pdG-dC are similar to, but slightly different from, the induced chemical shifts which are obtained when actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The pdN-dG dinucleotides (N = C, A, or T) form stacked complexes with 7-amino-actinomycin D. The presence of the 7-amino-group results in a larger dimerization constant (in aqueous solution) for 7-amino-actinomycin D [KD(6°C) = 4.4 × 103M-1], as compared to actinomycin D [KD(6°C) = 1.7 × 103M-1]; the chemical shifts which accompany dimer formation indicate that the chromophores stack in an inverted manner. Intercalation of 7-amino-actinomycin D into minature double helices, as well as into calf thymus DNA, poly(dG-dC)·poly(dG-dC), and poly(dA-dC)·poly(dG-dT), results in an enhancement of the relative fluorescence intensity and a shift in both the absorbance and corrected emission spectra.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 130
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Theoretical calculations of the heteronuclear vicinal coupling constant 3J(13C′NCαH) in peptides have been carried out using the Dirac vector model. The results showed an angular dependence for this coupling constant, which can be expressed in the form 3J(13C′NCαH) = A cos2 θ + B cos θ + C, where A, B, and C are constants and θ is related to the torsional angle φ of the peptide backbone. The results of the present calculations are in very good agreement with those obtained using finite perturbation theory at the INDO level of approximation.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 131
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of charged side chains on the ionization and fluorescence of the Tyr4 phenolic group in angiotensin (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe) was investigated. Several synthetic peptides related to angiotensin were titrated spectrophotometrically and quantum yields of tyrosine fluorescence were also determined. The electrostatic interactions were interpreted according to the Kirkwood-Tanford theory, and the results were related to a recently proposed model [J. L. De Coen and E. Ralston (1977) Biopolymers 16, 1929] for angiotensin conformation in solution. The titration and fluorescence results are in good agreement with the folded conformations of this model, with the exception that the data indicate a weaker interaction between the histidine side chain and the C-terminal carboxyl groups than that proposed in the model.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 132
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transient electric birefringence of poly(L-α,γ-diaminobutyric acid hydrochloride) in methanol/water mixtures has been measured over a wide range of field strengths and solvent compositions and at different polymer concentrations and temperatures. The molar ellipticity at 222 nm and the specific Kerr constant underwent an abrupt change between 75 and 80 vol % methanol at 25°C, accompanied by a solvent-induced helix-coil transition. Anomalous birefringence transients were observed between 78 and 80 vol% methanol above threshold field strengths. The double logarithmic plots of the steady-state specific birefringence versus the square of field strength for different solvent compositions and polymer concentrations could be superimposed by shifting them horizontally along the abscissa and vertically along the ordinate except for the range where anomalous transients were observed. The threshold field strength could be estimated from the point at which a downward deviation occurred. It increased with increasing polymer concentration and with increasing methanol content on the verge of the transition region. The results were interpreted as indicating that a conformational change from the charged helix to the charged coil is induced by high fields in this system, as in the case of poly(L-lysine hydrobromide) in methanol/water mixtures.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 133
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2037-2050 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Many ligands, including basic polypeptides, histones, and other proteins bind nonspecifically to DNA in such a way as to render unavailable for further binding several contiguous sites (generally bases or base pairs). An accurate description of the kinetics of such large ligand binding requires a more complex theoretical analysis than does the study of the binding of small ligands to DNA. An exact analytical solution of the problem does not appear feasible. Instead, a Monte Carlo approach is developed which provides an essentially exact numerical solution by simulating the binding experiment using a model one-dimensional lattice to represent the DNA molecule. For the limiting cases of totally irreversible binding and of instantaneous redistribution of bound ligands along the lattice, relatively simple equations can be written and solved for the binding kinetics. These solutions and their realms of applicability are discussed in some detail.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 134
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The DNA helix-coil transition has been studied in the presence of high concentrations of manganese ions (about 10-3M), which corresponds to the conditions close to equal stability of the A+T and G+C pairs, at the ionic strengths of 10-1, 10-2, and 1.6 × 10-3M Na+. With the Mn2+ ion effect, the transition range is significantly reduced to not more than 0.2°C at 1.2 × 10-3M Mn2+ and 1.6 × 10-3M Na+. The melting curves display a sharp kink at the end of the helix-coil transition, which is interpreted as an indication of the second-order phase transition. It is shown that the melting curves obtained can be approximated by a simple analytical expression 1 - θ = exp[-a(tc - t)], where θ is the DNA helix fraction, tc is the phase transition temperature, and a is an empirical parameter characterizing the breadth of the melting range and responsible for the magnitude of a jump of the helicity derivative with respect to the temperature at the phase transition point.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 135
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2267-2277 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pinacyanol in the presence of an excess of poly(L-glutamic acid) [polymer/dye ratio (P/D) 〉 10] exhibits different absorption spectra in the visible region when bound to the slightly charged polypeptide in the α-helical conformation or to the nearly completely dissociated polypeptide in the coillike conformation. These spectra reveal aggregation of the dye bound to the macromolecular chain in both conformations, although in the coillike one different kinds of aggregates may be present. Dye binding is accompanied by the appearance of CD bands in the visible region which are also different for the α-helical and the coillike conformations. The aggregates formed in the presence of the latter change slowly in time and seem to induce some conformational changes in the polypeptide chain. Furthermore, they have been found to be, at least partially, stable with respect to a subsequent reversal to the α-helical conformation. All results could be qualitatively interpreted assuming that in the coillike conformation, ordered regions exist along the chain as proposed by Krimm and Tiffany.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 136
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2289-2301 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The CD of GDH-NADH complexes was measured in order to reexamine the binding of coenzyme to GDH. The existence of two distinct Cotton effects associated with two separate NADH binding sites/subunit was confirmed with native, polymerizing and crosslinked, unpolymerizing enzyme. CD titration of the high-affinity NADH sites revealed significant dependence of the optical activity of the bound coenzyme on the state of protein association. Molar ellipticity of bound NADH decreased with the increasing degree of polymerization of GDH. It is suggested that the high-affinity NADH sites are loacted at or near the association interface. Binding of NADH to the low-affinity sites, in the presence of GTP, leads to an inversion of the CD spectrum of GDH-NADH complexes. This inversion is not related to the polymerization of GDH. However, for proper analysis of the CD of NADH bound to the low-affinity sites, a correction for the effect of polymerization on the optical activity of NADH bound to the high-affinity sites is required.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 137
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2315-2322 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a theoretical model which describes a cooperative helix-coil liquid-crystal phase transition. We show that this model predicts a first-order phase transition where certain types of chainlike macromolecules in solution make a transition from a nearly coiled to a nearly rigid conformation accompanied by a simultaneous development of long-range nematic-type liquid crystalline orientational order. From this model, the phase boundaries between nematic and isotropic phases are obtained as functions of concentration of macromolecules and of other physical parameters.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 138
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2357-2358 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 139
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2359-2361 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 140
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2363-2367 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 141
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2659-2672 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metal ions such as Zn2+ and Cu2+ can mediate interactions between copolypeptides (Glux, Tyry)n and polynucleotides. CD data show that these ternary complexes are characterized by an unstacking of nucleic acid bases, while the polypeptide adopts an α-helical conformation as observed in the two binary complexes polynucleotide-cation and polypeptide-cation. Fluorescence studies demonstrate that tyrosyl side chains interact with nucleic acid bases in the ternary complexes, leading to a quenching of tyrosine fluorescence.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 142
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2673-2681 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Calorimetric measurements of ΔH, the enthalpy of mixing with NaCl solutions per mole of polymer charge equivalent, have been made for the sodium salts of hyaluronate, chondroitin 4-sulfate, and chondroitin over the range msf = 0-0.5 (where msf is final NaCl molality); corrections were made for the enthalpy of dilution of NaCl. Values of ΔH for the range msf = 0-0.1 agree reasonably well with a theoretical estimate from the infinite line charge theory of polyelectrolytes. In order to apply the latter, calculations of several average short-range atomic spacings in hyaluronate were made from a statistical model with use of energy parameters which provide a good fit to experimental values of unperturbed dimensions.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 143
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2721-2731 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of ribose(O2′)-methylation on the stability of (O2′)-methylated polyribonucleotide helices has been studied by conformational energy calculations. The preferred orientation of the methyl group is found to further stabilize the helical phosphodiester conformation (g-,g-) due to the enhanced short-range interactions arising between the methyl groups and the adjacent ribose moieties. The experimentally observed increase in melting temperature of (O2′)-alkylated polyribonucleotides is thus attributable to the enhanced stability of the helical backbone conformation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 144
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2745-2768 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The addition of methylene blue to certain samples of Na alginate produces a complex succession of spectrally distinguishable aggregated (metachromatic) dye species. Three of these species are active in CD; they are interpreted as aggregates of dye, but probably dimers, bound in orientations characteristic of the constituent copolymer blocks of alginate to which they are tentatively assigned. The aggregates compete with divalent metal ions and hydrogen ion for the binding sites of the polymer. Other samples of alginate give a modified succession of aggregated spectral species, which are almost devoid of CD activity. Mild treatment with acid, insufficient for hydrolysis, converts forms of alginate with CD activity into modified forms without it, the absorption spectra of which resemble those of samples originally devoid of activity. It is implied, subject to confirmation, that the chiral properties of the binding sites of the native polysaccharide are diminished or lost by acid treatment during commercial preparation.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 145
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2733-2744 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We consider the problem of making allowance for superhelicity in the statistical-mechanical calculations of fluctuational violations of the DNA double helix. A simple model is discussed, making it possible in the calculations to use an approach based on the theory of helix-coil transition in DNA. The proposed algorithms allow calculating the effect of superhelicity on the base-pair fluctuational opening for any given sequence of nucleotides. An algorithm is also proposed allowing for the hairpin and cruciform structures in the palindromic regions of a sequence, as well as the open and helical states. The theory is used to calculate the melting curve for superhelical DNA at temperatures well below the melting point of the linear or nicked forms. The maps of opening probability are calculated for SV40 and φX174 DNA using their recently published complete nucleotide sequences. The data explain well the experimental results of probing the secondary structure of these DNA by single strand-specific endonucleases.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 146
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 3067-3076 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sequential polypeptides with the repeating units L-glutamyl-L-DOPA, L-DOPA-L-glutamyl-L-DOPA, L-glutamyl-L-glutamyl-L-DOPA, L-DOPA-L-DOPA-L-glutamyl-L-DOPA, and L-glutamyl-L-glutamyl-L-glutamyl-L-DOPA have been synthesized by solution polymerization of the p-nitrophenyl esters of the corresponding di-, tri-, and tetrapeptides. The O, O′-dimethyl and γ-methyl groups were used to protect side chains of L-DOPA and L-glutamic acid. The monomers for the polytripeptides and polytetrapeptides were prepared by stepwise elongation, using the dicyclohexylcarbodiimide coupling method. Moderately high molecular weight sequential polypeptides were obtained. The protected groups of the side chain were removed simultaneously by use of boron tribromide in chloroform. Trimethylphosphate-soluble sequential polypeptides containing L-DOPA were obtained.
    Zusätzliches Material: 1 Tab.
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  • 147
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. A20 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 148
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979) 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 149
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 82-86 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 150
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. A30 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 151
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 118-125 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 152
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 129-141 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Teil I dieser zweiteiligen Folge handelte von „Neueren Erkenntnissen der Pflanzenernährung“ [diese Zeitschr. 13, 97 (1979)].
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 153
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 13 (1979), S. 195-196 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 154
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 2012-2021 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Bicyclo[2.1.1]hexanes from Tricyclo[3.1.0.02,6]hexanesThe novel tricyclo[3.1.0.02,6]hexane derivatives 3 and 4, being fused with a fife- and a sixmembered ring respectively, are prepared from benzvalene in several steps. They and their lower homologues 1 and 2, having a three- and fourmembered ring respectively, add thiophenol under conditions of a radical reaction to form smoothly one cyclobutylphenyl thioether (16-19) in each case. Therefrom the parent hydrocarbons (5-8) which contain the bicyclo[2.1.1]hexane skeleton, are obtained by means of reduction with lithium in ethylamine.
    Notizen: Ausgehend von Benzvalen werden in mehreren Stufen die neuen Tricyclo[3.1.0.02,6]hexan-Derivate 3 und 4 mit anelliertem Fünf- bzw. Sechsring dargestellt. Sie und ihre niedrigeren Homologen 1 und 2 mit Drei- bzw. Vierring nehmen unter Bedingungen einer Radikalreaktion Thiophenol auf, wobei glatt jeweils ein Cyclobutylphenylthioether (16-19) gebildet wird. Mit Lithium in Ethylamin sind aus 16-19 die tricyclischen Stammkohlenwasserstoffe mit dem Bicyclo[2.1.1 ]hexan-Gerüst (5-8) erhältlich.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 155
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 2022-2027 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: The Influence of Fused Rings on the 13C Shieldings of Tricyclo[3.1.0.02,6]hexane and Bicyclo[2.1.1]hexane DerivativesThe 13C shieldings of the tricyclo[3.1.0.02,6]hexane derivatives 2-5 and of the bicyclo[2.1.1]-hexane derivatives 7-10 and 12-15 show a strong dependence on the size of the fused rings. Especially the γ-anti-effects, which cause downfield shifts, and the γ-syn-effects of these rings, which result in upfield shifts, are subject to unexpected variations.
    Notizen: Die 13C-chemischen Verschiebungen der Tricyclo[3.1.0.02,6]hexan-Derivate 2-5 und der Bicyclo[2.1.1]hexan-Derivate 7-10 und 12-15 zeigen eine starke Abhängigkeit von der Größe der anellierten Ringe. Insbesondere die nach tieferem Feld gerichteten γ-anti-Effekte und die nach höherem Feld gerichteten γ-syn-Effekte dieser Ringe unterliegen unerwarteten Variationen.
    Materialart: Digitale Medien
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  • 156
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1902-1912 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactions with Indole Derivatives, XXXIX. A Stereoselective Synthesis of Eburnamonine, Eburnamine, and EburnamenineStudies on the five-membered lactams 1 and 2 disclose a stereoselective access to eburnamonin-19-one (22). This substance is easily transformed into eburnamonine (25), eburnamine (30), and eburnamenine.
    Notizen: Das Studium der 5-Ring-Lactame 1 und 2 eröffnet einen stereoselektiven Zugang zum Eburnamonin-19-on (22). Diese Substanz läßt sich auf einfache Weise in die drei Alkaloide Eburnamonin (25), Eburnamin (30) und Ehurnamenin überführen.
    Materialart: Digitale Medien
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  • 157
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1916-1918 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ene Reactions with CyanothioformanilidesCyanothioformanilides 3 react with methylenecyclohexane (1) and β-pinene (2) in boiling toluene to yield the adducts 4 and 5, resp., according to the mechanistic scheme of an ene reaction.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 158
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979) 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 159
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1919-1922 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthese von neuen chiralen KohlenwasserstoffenUnsymmetrisches Anheften einer aliphatischen (CH2)n-Brücke an ein an sich achirales aromatisches System führt zu starren chiralen Kohlenwasserstoffen des Typs 2; die Enantiomeren 2 a konnten mit Hilfe von TAPA angereichert werden. Die Racemisierungskinetik wurde polarimetrisch bestimmt: ΔG≠20 = 93.6 kJ · mol-1.
    Materialart: Digitale Medien
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  • 160
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1923-1925 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pheromones, XXIV. Synthesis of the Sex Attractants (Z)-7-Dodecenyl Acetate and (Z)-7-Tetradecenyl Acetate(Z)-7-Dodecenyl acetate, the female sex pheromone of the Noctuid moth Trichoplusia ni, and (Z)-7-tetradecenyl acetate, the sex attractant of Amathes c-nigrum (Lepidoptera), are prepared by stereoselective Wittig olefination using the „silazide“ -technique.
    Materialart: Digitale Medien
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  • 161
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1927-1933 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Dynamic NMR Studies of (Di-tert-butylamino)arsanes and -stibanesThe reaction of LiN[C(CH3)3]2 with AsX3 (X = F → Br). (CH3)3CAsCl2 and SbCl3 yields the di-tert-butylamino)arsanes 1a-c, 2 and dichloro(di-tert-butylamino)stibane (1d). LiN(CR3)-(SiR3), R=CH3and 1a-c form 3. The El — N torsional barriers of these compounds (measured by temperature dependent 1H-NMR spectroscopy) are compared with those of the (diisopropylamino)arsanes 4. and other related compounds. The influence of the N and El ligands with respect to the El — N torsional barrier is discussed. Thermolysis of 3c affords the di-tert-butylaminyl radical.
    Notizen: Durch Umsetzung von LiN[C(CH3)3]2 mit AsX3 (X = F → Br), (CH3)3CAsCl2 und SbCl3 erhält man die (Di-tert-butylamino)arsane 1a-c und 2 sowie Dichlor(di-tert-butylamino)stiban reagieren mit LiN(CR3)(SiR3), R=CH3 zu 3 weiter. Die durch temperaturabhängige 1 H-NMR-Messungen ermittelten El- N-Rotationsbarrieren dieser Verbindungen werden hinsichtlich des Ligandeneinflusses am N- El - Atom mit den (Diisopropylamino)arsanen 4. und verwandten Molekülen verglichen. 3c. ergibt bei der Thermolyse das Di-tert-butylaminyl-Radikal.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 162
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1934-1940 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Isocyanide Complexes, I. Isocyanophosphanes and -arsanes as Ligands of ComplexesThe reaction of K[CpMn(CO)2CN] (Cp = η-C5H5) with PR2Cl (R=C2H5, OC2H5, C6H5) and As(C6H5)2Cl yields the complexes CpMn(CO)2CNPR2 (3a - c) and CpMn(CO)2CNAsPh2 (3d) with C-coordinated isocyanophosphanes and -arsanes. In the reaction of CpMn(CO)2CNPPh2 with CpMn(CO)2 THF or of K[CpMn(CO)2CN] with CpMn(CO)2PPh2Cl a complex with an isocyanophosphane bridge, {CpMn(CO)2}2(CNPPh2) (4), is obtained. The IR, NMR, and mass spectra of the compounds 3a-d and 4 are discussed.
    Notizen: Bei der Umsetzung von K[CpMn(CO)2CN] (Cp = η-C5H5) mit PR2Cl (R=C2H5, OC2H5, C6H5) und As(C6H5)2Cl entstehen die Komplexe CpMn(CO)2CNPR2 (3 a - c) und CpMn(CO)2CNAsPh2 (3d) mit C-gebundenen Isocyanphosphanen und -arsanen. Durch Reaktion von CpMn(CO)2CNPPh2 (3c) mit CpMn(CO)2 THF bzw. von K[CpMn(CO)2]CN mit CpMn(CO)2PPh2Cl erhält man den Komplex {CpMn(CO)2}2(CNPPh2) (4) mit einer Isocyanphosphan-Brücke. Die IR-, NMR- und Massenspektren der Verbindungen 3a-d und 4 werden diskutiert.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 163
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1941-1947 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Barriers to Hindered Rotation Around the N-Glycosidic Bond, IV. 1-(βD-Ribofuranosyl) isocyanuric AcidsThe β-ribofuranosyl nucleosides 5a-c and 6b, c are synthesized. The temperature dependency of the 1H- and 13C-NMR spectra can only be interpreted as hindered rotation around the N-glycosidic bond2). The Gibbs activation energies (43-46 kJmol-1) are independent of acetylation of the OH groups of the furanose ring or restriction of its flexibility through formation of a 2′,3′-isopropylidene derivative, and are considerably lower than the corresponding data (about 69 kJmol-1) of the glucopyranosyl nucleosides 7b, c. The activation entropies are small. The results are interpreted.
    Notizen: Es werden Synthesen der β-Ribofuranosylnucleoside 5a-c und 6b, c beschrieben. Die Temperaturabhängigkeiten der 1H-und 13C-NMR-Spektren lassen sich nur als Folge behinderter Rotation um die N-glycosidische Bindung deuten2) Die Gibbsschen Aktivierungsenergien (43-46 kJmol-1) sind unabhängig von einer Acetylierung der OH-Gruppen des Furanoseringes oder einer Einschränkung von dessen Flexibilität durch Bildung eines 2′,3′-Isopropylidenderivates und liegen erheblich tiefer als die entsprechenden Werte (um 69 kJmol-1) der Glucopyranosylnucleoside 7b, c. Die Aktivierungsentropien sind gering. Die Befunde werden gedeutet.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 164
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1948-1955 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Syntheses of α-BromoisothiocyanatesSecondary isothiocyanates (1j-q) and primary isothiocyanates R—CH2 - NCS with an activating group R (1f, g) react with N-bromosuccinimide (NBS) to form α-bromoisothiocyanates 2 in high yields. The not activated primary isothiocyanate 1c slowly forms the stable α,α-dibromoisothiocyanate 10. In the presence of β-hydrogens some of the α-bromoisothiocyanates 2 eliminate HBr spontaneously, and secondary products may be formed. The α-bromination of isothiocyanates is a radical reaction following a Goldfinger mechanism.
    Notizen: Sekundäre Isothiocyanate (1j-q) und primäre Isothiocyanate R-CH2 - NCS mit einer aktivierenden Gruppe R (1f, g) lassen sich mit N-Bromsuccinimid (NBS) in hohen Ausbeuten zu den α-Bromisothiocyanaten 2 bromieren. Das nicht aktivierte Isothiocyanat 1c reagiert langsam zum stabilen α,α-Dibromisothiocyanat 10. Bei Anwesenheit von β-Wasserstoffatomen spalten die α-Bromisothiocyanate 2 zum Teil spontan HBr ab, und es entstehen Folgeprodukte. Die α-Bromierung der Isothiocyanate erfolgt radikalisch nach einem Goldfinger-Mechanismus.
    Materialart: Digitale Medien
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  • 165
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1956-1972 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactions of α-Bromoisothiocyanatesα-Bromoisothiocyanates 11.2) with a hydrogen in β-position eliminate HBr to form vinyl isothiocyanates (products 2, 3, 5). Water hydrolyzes 1 to carbonyl compounds (7a). Hard nucleophiles attack 1 at the α-C-atom with substitution of bromine (products 8-12), but soft nucleophiles add to the C-atom of the isothiocyanato group (products 14, 19). Compounds 1 react with bifunctional nucleophiles to heterocycles (e. g. products 16, 21). The chemical properties of the classes of compounds, part of which are new, e. g. the geminal diisothiocyanates 12, are examined. The alkylidene thiourea 14f shows hindered rotation around the amide-CS—N bond (ΔG≠394 = 82.8 kJmol-1) and around the C=N double bond (ΔG≠244 = 52.9 kJmol-1).
    Notizen: α-Bromisothiocyanate 1 mit einem β-Wasserstoff spalten HBr zu Vinylisothiocyanaten ab (Produkte 2, 3, 5). Wasser hydrolysiert 1 zu Carbonylverbindungen (7a). Harte Nucleophile greifen 1 am α-C-Atom unter Substitution des Broms an (Produkte 8-12), weiche Nucleophile lagern sich dagegen an das C-Atom der Isothiocyanatgruppe an (Produkte 14, 19). Verbindungen 1 reagieren mit bifunktionellen Nucleophilen zu Heterocyclen (z. B. Produkte 16, 21). Die chemischen Eigenschaften der z. T. neuen Verbindungsklassen, z. B. der geminalen Diisothiocyanate 12, werden untersucht. Der Alkylidenthioharnstoff 14f zeigt behinderte Rotation um die Amid Cs—N-Bindung (ΔG≠394 = 82.8 kJmol-1) und um die C=N-Doppelbindung (ΔG≠244 = 52.9 kJmol-1).
    Materialart: Digitale Medien
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  • 166
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1973-1980 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: The Crystal Structure and the Fluxional Behaviour in Solution of (η3-Allyl)dicarbonyl(triphenyl-phosphane)cobalt[Co(η3-C3H5)(CO)2PPh3] (1) crystallizes in the triclinic space group P1 with two molecules per unit cell. The crystal structure was solved and refined with X-ray diffraction data (R = 0.031, 2046 observed reflections). The cobalt atom has a distorted square pyramidal coordination with the formally bidentate η3-allyl ligand, the phosphane, and one carbonyl in the basal positions. According to the NMR spectra at temperatures down to 135 K, in solution there exists a fluxional equilibrium with the η3-allyl ligand oscillating between two enantiomeric positions.
    Notizen: [Co(η3-C3H5)(CO)2PPh3] (1) kristallisiert triklin in der Raumgruppe P1 mit zwei Molekülen pro Elementarzelle. Die Kristallstruktur wurde mit Röntgenbeugungsdaten ermittelt und verfeinert (R = 0.031, 2046 beobachtete Reflexe). Das Cobaltatom ist verzerrt quadratisch-pyramidal koordiniert, mit dem formal zweizähnigen η3-Allylliganden, dem Phosphan und einem Carbonylliganden in der Pyramidenbasis. Nach den NMR-Spektren bei Temperaturen hinab bis 135 K liegt in Lösung ein dynamisches Gleichgewicht vor, bei dem die η3-Allylgruppe zwischen zwei enantiomeren Positionen fluktuiert.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 167
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1981-1990 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Hydrazidines, III. Synthesis of 1,2,4,5-Tetrazino[3,2-a]isoindolesReaction of acetohydrazide hydrazone hydrochloride (1) with phthalaldehydic acid (5) yields 3-methyl-1,10b-dihydro-1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-one (8), which affords 1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-one (9a) by mild oxidation. 9a is also obtained by the reaction of 1 with the phthalic acid derivatives 6a, 7a, and 7b. Starting with 9a, the 1,2,4,5-tetrazino[3,2-a]isoindoles 12-15 are synthesized. Interaction of 1 and 3-nitrophthalic anhydride (6b) yields two isomeric nitro-1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-ones (9b,c). Oxidation of 9a or b with KMnO4 in methanol affords the 1,2,4,5-tetrazino 17a, b. Mild Oxidation of 9a with KMnO4 in water/trichloromethane yields a dimer (20), which dissociates in nitromethane into the radical 19.
    Notizen: Durch Reaktion von Acetohydrazid-hydrazon-hydrochlorid (1) mit Phthaladehydsäure (5) wird 3-Methyl-1, 10b-dihydro-1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-on (8) erhalten das durch milde Oxidation in 3-Methyl-1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-on (9a) übergeführt wird. 9a entsteht auch aus 1 und den Phthalsäurederivaten 6a, 7a und 7b. Ausgehend von 9a werden die 1,2,4,5-Tetrazino[3,2-a]isoindole 12-15 synthetisiert. Aus 1 und 3-Nitrophthalsäureanhydrid (6b) werden zwei isomere Nitro-1,2,4,5-tetrazino[3,2-a]isoindol-6(4H)-one (9b, c) erhalten. Oxidation von 9a oder b mit KMnO 4 in Methanol ergibt die 1,2,4,5-Tetrazine 17a, b. Vorsichtige Oxidation von 9a mit KmnO4 in Wasser/Chloroform ergibt ein Dimeres (20), das in Nitromethan in das Radikal 19 dissoziiert.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 168
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1991-1998 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Stereochemistry of the Metal-Metal Bond. Structural Comparison of the Complexes Cr2(CO)8(AsMe2)2, CrFe(CO)7(AsMe2)2, and Fe2(CO)6(AsMe2)2The molecular structures of the new complexes CFer2(CO)8(AsMe2)2 (1) and CrFe(CO)7(AsMe2)2 (2) were determined crystallographically, that of Fe2(CO)6(AsMe2)2 (3) was redetermined. In all three compounds the metal-metal bond lengths are determined by the goemetrical requirements of the ligands. The fact that the M2As2 framework is planar in 1 and strongly folded in 2 and 3 can also be explained by the steric demands of the ligands. Aspects of the fluxionality of these complexes are discussed.
    Notizen: Die Molekülstrukturen der neuen Komplexe Cr2(CO)8(AsMe2)2 (1) und CrFe(CO)7(AsMe2)2 (2) wurden kristallographisch ermittelt, die von Fe2(CO)6(AsMe2)2 (3) wurde neu bestimmt. In allen drei Verbindungen sind die Metall-Metall-Bindungslängen durch die geometrischen Ansprüche der Liganden festgelegt. Auch die Tatsache, daß das M2As2-Gerüst in 1 eben und in 2 und 3 jeweils stark gefaltet ist, läßt sich auf den Raumbedarf der Liganden zurückführen. Aspekte der Fluktuation dieser Komplexe werden diskutiert.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 169
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1999-2011 
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Investigations on Metabolites of Microorganisms, XX. The Structures of the Flexirubin-type Pigments from Cytophaga johnsonae CyjlCytophaga johnsonae Cy jl produces more than 25 different flexirubin-type pigments (2 a-h, 3 a-h, 4 a-h, 5) besides lower concentrations of carotenoids. These pigments could be separated using HPLC. Their structures have been elucidated. 5 is the first known member in this class of bacterial pigments containing two chlorine atoms.
    Notizen: Das Gleitende Bakterium Cytophaga johnsonae Cy jl produziert neben wenig Carotinoiden mehr als 25 verschiedene Pigmente vom Flexirubin-Typ (2a-h, 3a-h, 4a-h, 5), deren Trennung u.a. durch Hochdruckflüssigchromatographie gelang. Über die Konstitutionen dieser Pigmente wird berichtet. Mit 5 wurde erstmals in dieser Verbindungsklasse ein dichlorhaltiges Pigment aufgefunden.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
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  • 170
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title compound, an analogue of [Leu5]-enkephalin with L-o-carboranylalanine replacing L-phenylalanine in position 4, was prepared by fragment condensation. The analogue has a 3-fold higher affinity for rat brain opiate receptors in the [3H]naloxone competition assay than natural [Leu5]-enkephalin. Like [Leu5]-enkephalin and Na-acetyl-[Leu5]-enkephalin, the N-terminal tripeptide fragment, H · Tyr-Gly-Gly · OH, had no melanotropic activity in the Rana pipiens frog skin assay.A convenient, direct synthesis of methyl t-butoxycarbonyl-L-propargylglycinate is described, and the 13C-NMR. spectra of L-o-carboranylalanine recorded. The procedure was extended to the preparation of BOC · Car-Leu · OMe from BOC · Pra-Leu · OMe. A number of new propargylglycine derivatives are reported.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 171
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conversion of primary, secondary and vinylic halides to the two C-atoms homologated phenylselenomethyl ketones 8 is described. The method involves addition of the readily available phenylselenoacetaldehyde 5 to the Grignard reagents 9 and oxidation of the resulting β-hydroxy-selenides 10 (Scheme 3).
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 172
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preparation of Stilbenyl Derivatives of 1,2,4-OxadiazolesSchiffs bases derived from 3- and 5-(p-formylphenyl)-phenyl-1,2,4-oxadiazoles and chloroanilines are reacted with various p-tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). The reactivity of 5-[4-(chlorophenylimino-methyl)phenyl]-3-phenyl-1,2,4-oxadiazoles is very low and side reactions will predominate.
    Zusätzliches Material: 1 Ill.
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  • 173
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (Perhalomethylthio)heterocycles. XIX. Mitt.: s. [1]. . Acid-catalyzed substitutions on (perchlorofluoromethylthio)pyrroles and their agro-biological activitiesIn the presence of C4F9SO3H the (perhalomethylthio)pyrroles 1a-c react with Cl3-nFnCSCl (n = 1-3) to give mixtures of the 2,5- and 2,4-disubstituted pyrroles 2a-f and 3a-h. 2a and 3a react with CF3SCl (catalyst CF3SO3H) yielding 2,3,5-tris (trifloromethylthio)pyrrole (4a), which under similar conditions reacts further to give 2,3,4,5-tetrakis (trifluoromethylthio)pyrrole (5). As a by-product during the conversion of 3a to 4a 2,3,4-tris (trifluoromethylthio)pyrrole (4b) is formed. The pyrroles 2a, 4a and 5 form the mercury salts 6a-c; compound 5 yields also a silver salt 7. The 1H- and 19F-NMR. spectra are discussed and the agro-biological properties of the compounds investigated.
    Zusätzliches Material: 4 Tab.
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  • 174
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1451-1457 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new way to vinylic ethers from acetalsAcetals react at low temperatures in presence of a Lewis acid (aluminium chloride or magnesium bromide) with tertiary amine to give in good yields the vinylic ethers corresponding to the elimination of one molecule of alcohol.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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  • 175
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Addition Reaction of 3-Dimethylamino-2,2-dimethyl-2H-azirine with Phenylisocyanate and Diphenylketene3-Dimethylamino-2,2-dimethyl-2H-azirine (1a) reacts with carbon disulfide and isothiocyanates with splitting of the azirine N(1), C(3)-double bond to give dipolar, fivemembered heterocyclic 1:1 adducts. In some cases, these products can undergo secondary reactions to yield 1:2 and 1:3 adducts. In this paper it is shown that the reaction of 1a with phenylisocyanate also takes place by cleavage of the N(1), C(3)-bond, whereas with diphenylketene N(1), C(2)-splitting is observed.The reaction of 1a and phenylisocyanate in hexane at room temperature yields the 1:3 adduct 2 in addition to the trimeric isocyanate 3 (Scheme 1). A mechanism for the formation of 2 is given in Scheme 5. Hydrolysis experiments with the 1:3 adduct 2, yielding the hydantoins 4-6 and the ureas 7 and 8 (Schemes 3 and 5), show that the formation of this adduct via the intermediates d, e and f is a reversible reaction.The aminoazirines 1a and 1b undergo an addition reaction with diphenylketene to give the 3-oxazolines 14 (Scheme 8), the structure of which has been established by spectral data and oxidative degradation of 14a to the 3-oxazolin-2-one 15 (R1 — R2 — CH3, Scheme 9).
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  • 176
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H-NMR. Spectroscopic Analysis of Prochiral Allenic Esters Using Optically Active Europium Shift ReagentsThe prochiral allenic methyl esters 1-4 (cf. Scheme) show in the presence of 1 mol-equiv. tris[3-(heptafluorobutyryl)-(+)-camphorato]europium (III) (Eu (hfc)3) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) induced unlike 1H-NMR. shift differences (ΔΔδ) for the enantiotopic protons and methyl groups on C(4), respectively (cf. Fig. 2 and 3). This effect allows to determine directly the 2JH,H coupling constants of the geminal protons on C(4) of the allenic esters 1 (15.5 Hz) and 2 (14.5 Hz) (cf. Table 2).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 177
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1466-1474 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Heterocyclic anellated derivatives of strychnine: Imidazo-, oxazolo- and (1,3-dioxolo)strychnineThe synthesis of imidazo-, oxazolo- and dioxolo-strychnine derivatives, anellated at the 2,3-position of the aromatic nucleus is described. The spectroscopic properties of these compounds and of some intermediates are given.
    Zusätzliches Material: 3 Tab.
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  • 178
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1475-1484 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: UV.-irradiation of pivalic and isobutyric acid and their methyl esters as well as of α-hydroxy isobutyric and malonic acid in solution lead to chemically induced dynamic nuclear polarization (CIDNP.) of parent compounds and of various reaction products. CIDNP.-effects and product distributions confirm α-cleavage of the C(α), CO bond to be the major mode of photodecomposition. Scavenger experiments indicate that decomposition of the molecules from a triplet excited state is roughly equally or more probable than from a singlet excited state. Quantum yields of educt disappearance are also given for the methyl esters of pivalic and isobutyric acid.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 179
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sodiumthiophenoxide and sodiumphenylselenide react with N-benzyl- and N-hexyl-di-p-toluenesulfonamides (1 and 2) via displacement at the C-atom to afford the corresponding organosulfides and selenides in yields of 68-96%. In contrast, sodium cyanide converts disulfonamides to monosulfonamides by attack on the S-atom. The different selectivities of phenylsulfide and selenide as compared to cyanide anions with respect to attack on the C- and S-atoms are rationalized on the grounds of the HSAB (hard and soft acids and bases) principle of Pearson.
    Zusätzliches Material: 3 Tab.
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  • 180
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1497-1500 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The recently proposed structure of the carotenoid pigment prolycopene as the 7,9,7′,9′-tetra-cis isomer of lycopene has been unambiguously confirmed by a series of homonuclear Overhauser 1H-NMR. experiments at 270 MHz. Comparative measurements are reported for lycopene.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 181
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The racemic sesquiterpene isocomene (1) has been synthesized starting from 1,7-octadien-3-one (2) in a stereoselective manner (Scheme 2). In the key step 4 → 5 the C(7), C(8)-bond was formed by an intramolecular thermal ene reaction. Further elaboration of 5 involved the ring contraction 6 → 7, the elimination 8 → 9 and the final olefin isomerization 9 → 1.
    Materialart: Digitale Medien
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  • 182
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metabolites of Microorganisms. The Aspochalasins A, B, C, and DThe structures of the antibiotic aspochalasin B (asposterol) and its inactive co-metabolites aspochalasin A, C, and D from Aspergillus microcysticus (Tü 502) were elucidated by extended spectroscopic studies and chemical degradation. The structures are: aspochalasin A = 10-isopropyl-14-methyl[11]cytochalasa-6, 13-dien-1, 17, 18, 21-tetrone (32), aspochalasin B = 17-hydroxy-10-isopropyl-14-methyl-[11]cytochalasa-6, 13, 19-trien-1, 18, 21-trione (11), and aspochalasin C = 17, 18-dihydroxy-10-isopropyl-14-methyl[11]cytochalasa-6, 13, 19-trien-1, 21-dione (29). Aspochalasin D (1) is a diastereomer of aspochalasin C (different configuration at C (17) or C (18)).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 183
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metabolites of Microorganisms. Synthesis of 3-Isobutyl-4,5-dimethylisoindolin-1-one, a Degradation Product of Aspochalasin D3-Isobutyl-4,5-dimethylisoindolin-1-one (1) and 3-isobutyl-6, 7-dimethyl-isoindolin-1-one (6) were synthesized in a non-regioselective way. The structures could be assigned unequivocally by spectroscopic means. Compound 1 was identical with a degradation product of Aspochalasin D.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 184
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1531-1542 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Complexation in anhydrous methanol of Cu (II) and Zn (II) with diaza-polyoxamacrocyclic ligandsProtonation of five diaza-polyoxamacrocyclic ligands, (L = [2.1], [2.2], [2.1.1.], [2.2.1], [2.2.2]), and their complexing properties towards Cu2+ and Zn2+ cations have been studied in anhydrous methanolic solutions.Potentiometric measurements have been carried out at 25°, using 5 · 10-2MEt4N+ClO4- as support-electrolyte, in order to determine the nature of the species formed upon complexation and their stability constants. The results were confirmed by spectrophotometry, for the cupric complexes of [2.1] and [2.2.2], and the electronic spectra of the different complexes were calculated.Comparison between complexation in aqueous and methanolic solutions have been made: as in water, ML2+ species and sometimes protonated MHL3+ species, with higher stability constants, are present in methanol; but the main difference is the formation of dinuclear complexes M2L4+, between Cu2+ and all ligands except [2.1]. In these complexes the Cu2+ cations cannot be both ‘encaged’ in the ligand cavity because of its small size. The different possible structures are discussed in terms of the stability constants values. The protonation constants values and the existence of the binuclear complexes may indicate a possible conformational change in the complexing ligand on changing the solvent from water to methanol.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 185
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1549-1558 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: rac-1,2,10-Trimethoxy-aporphine (14) and rac-2-ethoxy-10,11-dimethoxyaporphine (27) have been synthesized from the 3-phenylphenethylamines 9 and 22 by a new route. The 8-phenyl-3,4-dihydroisoquinolines 11 and 24, the oxo-aporphines 12 and 25 and the rac-nor-aporphines 13 and 26 were obtained as intermediates.
    Materialart: Digitale Medien
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  • 186
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (6aR)-1,2-(Methylenedioxy)aporphine-10, 11-diol (8) and (6aR)-aporphine-1, 1, 10, 11-tetrol (16) have been prepared from natural (S)-bulbocapnine (4). For both compounds, the partial synthesis included racemic intermediates which have been resolved into their enantiomers. Both compounds 8 and 16 showed dopaminergic activity in rats, although to a lower extent than (R)-apomorphine (1) itself.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1559-1565 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The self-ordered supramolecular structures formed by 5′-guanosine monophosphate (disodium salt) in aqueous solution at pH 7.8 show pronounced interaction with ammonium ions. Rather than competing with potassium ions for the central cavity in hydrogen-bonded guanine tetramers, ammonium ions bring about - in synergism with potassium ions - further aggregation. Glycine appears to destroy the aggregates, by competing with potassium ions for the core positions within the tetramers. Conversely, alanine does not interact significantly with the system. These conclusions follow from analysis, at various concentrations, of the microdynamics and of the mole fractions of sodium ions bound to self-assembled 5′-GMP--, obtained from relaxation rate measurements for the 23Na nucleus, as the 5′-GMP-- counter-ion.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 188
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1586-1602 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthetic application of epoxynitrones. II. Syntheses of steroidal α-methylidene-γ-lactonesThis communication describes the application of the epoxynitrone/CF3SO3SiR3 → 1,2-oxazine annelation-reaction [1] to the syntheses of steroidal α-methylidene-γ-lactones from olefines, e.g. 12 → 14a/b → 16a/b → 18a/b → 20 → 22 (Scheme 2).
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 189
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1603-1604 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence is presented which demonstrates that 13C-NMR. spectroscopy can be used with confidence in evaluating the configuration of R1R2CHOH centers at C(6) and C(8) of iridoid glucosides.
    Zusätzliches Material: 1 Tab.
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  • 190
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1566-1569 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: XPS. and 1H-NMR. spectra of 1,3-diaryltriazenes complexes of Hg(II)The core binding energies C 1s, N 1s, Hg 4f7/2, Hg 4f5/2 in 7 symmetrical p-substituted 1,3-diphenyltriazenes complexes of Hg(II) have been measured by XPS. Within the limits of experimental error (± 0.2 eV) only one N 1s signal could be detected. This indicates the equivalence of the 3 N-atoms. Invariance of C 1s, N 1s, Hg 4f7/2, Hg 4d5/2 signals with the para substituents on the phenyl ring is explained on the basis of ionic character in the Hg, N bond. These results are corroborated by the 1H-NMR. spectra.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 191
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and reactivity of 3-aryl-1-(3,4-dimethyl-5-isoxazolyl)-triazenes and 4-arylazo-3,4-dimethylisoxazol-5-onesAccording to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5-amino-3,4-dimethylisoxazole (3) leading to either 3-aryl-1 (3,4-dimethyl-5-isoxazolyl)-triazenes (1A) or 4-arylazo-3,4-dimethylisoxazol-5-ones (4). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 192
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2282-2284 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The neurotoxin α-kainic acid (7) was synthesized from 1 via the thermal key step 5 → 6 in 41% overall yield.
    Materialart: Digitale Medien
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  • 193
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2276-2281 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Stereospecific synthesis of 6β,7β-methylene-20-spirox-4-ene-3,21-dioneA stereospecific synthesis of the highly active 6β,7β-methylene-20-spirolactone 4 (Prorenone) is described.
    Materialart: Digitale Medien
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  • 194
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2285-2302 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chiral 2,2′-polyoxaalkano-9,9′-spirobifluorenesFrom 2,2′-diacetyl-9,9′-spirobifluorene (2), twelve chiral polyethers have been prepared as potential ion- and enantiomer-selective ionophores. The absolute configuration of the polyethers 15-17, 19-22, and 25 has been determined by chemical correlation with vespirenes [11] [29], by circular dichroism, and by X-ray analysis. The circular dichroism of 15-17, 19 and 21 depends on the size of the macrocycle and indicates that the fluorene chromophores of 19 and 21 with 13- and 16-membered rings respectively deviate considerably from orthogonality.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 195
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2325-2328 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Favorskii-rearrangement in the presence of 3,4-dimethoxyfuran: preparation of 3,4-dimethoxy 11endo-oxo-tricyclo [4.3.1.12,5]undec-3-en-10-one and any derivativesOn treatment with sodiumhydride of 2-chloro-cyclohexanone in the presence of 3,4-dimethoxyfuran, a possible intermediate of the Favorskii-rearrangement has been trapped as 3,4-dimethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undec-3-en-10-one (3). This new compound contains a highly nucleophilic double bond. It can be cleaved in high yield by ozonolysis to 2exo, 4exo-bis (methoxycarbonyl)-3-oxabicyclo [3.3.1]nonan-9-one (4). Addition of chlorine to 3 occurs in stereoselective exo-cis-manner to the crystalline 3exo, 4exo-dichloro-3endo,4endo-dimethoxy 11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (5). Silver ion assisted hydrolysis of 5, followed by thermal treatment of the intermediate hydrates, leads to the red 11endo-oxa-tricyclo [4.3.1.12,5]undecan-3,4, 10-trione (6), and methanolysis to 3,3,4,4-tetramethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (8). By photolytic decarbonylation, 8 is converted into 3,3,4,4-tetramethoxy-10-oxa-tricyclo-[4.3.12,5.0]decan (9).
    Materialart: Digitale Medien
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  • 196
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2350-2360 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Activated quinones: O- versus C-addition of phenols. New regiospecific syntheses of xanthones, thioxanthones and N-methyl-9-acridonesThe acid catalyzed reaction of phenols with activated quinones, e.g. 2-methoxycarbonyl-1, 4-benzoquinone or 2-acetyl-1, 4-benzoquinone, leads to substituted biphenylderivatives (C, C-addition) as has been previously described [1]. O, C-Addition of phenols has now been achieved by using 2-methoxypyridin or 4-dimethyl-aminopyridin [4] as basic catalysts. The resulting substituted diphenylethers can serve as convenient starting materials for regiospecific syntheses of substituted xanthones, especially for 1, 4-dimethoxyxanthones.Arylthiols and N-methyl-N-arylamines also react readily with activated quinones to give substituted di-aryl-thioethers and N-methyl-N, N-diarylamines respectively; both types of compounds are convenient materials for regiospecific syntheses of substituted thioxanthones and N-methyl-9-acridones.
    Materialart: Digitale Medien
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  • 197
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2361-2373 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cob(I)alamin as Catalyst. 5. Communication [1]. Enantioselective Reduction of α,β-Unsaturated Carbonyl DerivativesThe cob(I)alamin-catalyzed reduction of an α,β-unsaturated ethyl ester in aqueous acetic acid produced the (S)-configurated saturated derivative 2 with an enantiomeric excess of 21%. The starting material 1 is not reduced at pH = 7.0 in the presence of catalytic amounts of cob(I)alamin (see Scheme 2). It is shown that the attack of cob(I)alamin and not of cob(II)alamin, also present in Zn/CH3COOH/H2O, accounts for the enantioselective reduction observed. All the (Z)-configurated starting materials 1, 3, 5, 7, 9 and 11 have been transformed to the corresponding (S)-configurated saturated derivatives 2, 4, 6, 8, 10 and 12, respectively. The highest enantiomeric excess revealed to be present in the saturated product 12 (32,7%, S) derived from the (Z)-configurated methyl ketone 11 (see Scheme 3 and Table 1). The reduction of the (E)-configurated starting materials led mainly to racemic products. A saturated product having the (R)-configuration with a rather weak enantiomeric excess (5.9%) has been obtained starting from the (E)-configurated methyl ketone 23 (see Scheme 5 and Table 2). The allylic alcohols 16 and 24 have been reduced to the saturated racemic derivative 17.
    Zusätzliches Material: 3 Tab.
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  • 198
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Total Synthesis of Natural α-TocopherolTwo independent syntheses of (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl-methanol (8b), (Scheme 6 resp. 9) as optically active chroman moiety for the preparation of natural vitamin E via (S)-6-acetoxy-2,5,7,8-tetramethylchroman-2-carboaldehyde (2a) (Scheme 1) and a corresponding side chain are described. Both reaction sequences use trimethyl-hydroquinone as starting material; one approach employs an optically active C4 unit (10a) (Schemes 5 and 6) to introduce the required configuration at C(2), the other uses an optically active C5-synthon (11a) (Schemes 8 and 9) to build the optically active chroman unit. The correct configuration and optical purity of the chroman synthesized is established by correlation with optically pure material of known configuration from which natural vitamin E had already been derived [2].
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  • 199
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of the antibiotic hedamycin (1) has been solved by direct method and refined by least squares techniques to R = 0.091 for 2289 of 2643 independent reflexions. Crystals of C41H50N2O11 are orthorhombic, space group P212121 with lattice parameters a = 24.239 (12), b = 21.440 (10), c = 7.369 (4) Å, Z = 4. The structural features of hedamycin derived earlier by chemical and spectroscopical means are confirmed. Optical rotation and circular dichroism indicate that hedamycin (1) has the absolute configuration of the related antibiotic kidamycin (3). The conformation of ring F is a chair form with the aryl substituent almost axial. The bioxirane part of the antibiotic is in a synclinal conformation.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 200
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-caroteneWittig-condensation of optically active azafrinal (1) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol (2) and (+)-(R)-α-ionol (5) leads to the crystalline and optically active carotenoid diols 4 and 7, respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9, respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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