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  • 1
    Electronic Resource
    Electronic Resource
    Conformational analysis of substituted dibenzo-14-crown-4 ethers in solution by 1D and 2D NMR (1993)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 16 (1993), S. 91-95 
    Details
    ISSN: 1573-1111
    Keywords: Dibenzo-14-crown-4 ; NMR ; conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preferred conformations in solution for substituents onsym-dibenzo-14-crown-4 ethers are shown by NMR to depend on the atom, carbon or oxygen, linking the substituent to the crown ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708765
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Conformational Studies of an Asymmetrical Dibenzo-16-crown-5 Carboxylic Acid (2000)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 36 (2000), S. 287-299 
    Details
    ISSN: 1573-1111
    Keywords: crown ether ; NMR ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Asymmetrical cis-5,6-dimethyl-6-oxyacetoxy-(2,3)(9,10)-dibenzo-16-crown-5 was synthesized by a multi-step sequence and its stereochemistry determined by NOE experiments. Introduction of the 6-methyl group markedly reduces the stability constant for complexation of Na+ and K+ by the ionized form of the lariat ether carboxylic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008078220916
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  • 3
    Electronic Resource
    Electronic Resource
    Orbital electronegativity and analytical representation of atom valence state energyDedicated to the memory of Prof. Alojzy Golebiewski (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 1016-1030 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An analytical representation of atom valence state energy (E(nj), j = 1,…4; E(nj) is a nonlinear function of orbital occupancy numbers nj) is proposed and explicitly derived for H—Ar; the values of electronegativity calculated based on E(nj) agree within truncation error with those of Hinze and Jaffe. However, in our representation, orbital electronegativity χ and hardness parameters η of a given orbital always include nonlinear contributions from other orbitals, hence accounting for their influence on χ and η. An atomic charge calculation procedure based on E(nj) is also described and shown to perform well.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540100806
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  • 4
    Electronic Resource
    Electronic Resource
    A ring-bracing approach to computer-assisted ligand design (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 233-240 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Rigid inhibitors suffer a smaller loss of conformational entropy when they bind to a macromolecular receptor than their acyclic counterparts. They can also be useful for elucidating pharmacophores due to their reduced conformational space and may be more amenable to synthesis. Computational approaches to rational drug design should therefore take these factors into consideration when suggesting possible compounds. We describe how an acyclic chain which links two parts of a receptor site can be ‘braced’ using ring templates. The acyclic chains may be produced from a number of sources, including lattices or the structures of known inhibitors. The resulting structures contain a rich variety of isolated and fused ring systems, which provide many useful molecular skeletons for subsequent inhibitor design. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150213
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of molecular topology and atomic hybridization states from heavy atom coordinates (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 891-898 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A method is presented for the derivation of hybridization states and connectivity within molecules from the atomic numbers and coordinates of heavy atoms. The algorithm utilizes bond length data from studies of the Cambridge Structural Database (Allen et al., J. Chem. Soc. Perkin Trans. II, S1, (1987)). The program, IDATM, is useful for processing input to hydrogen-adding routines and molecular mechanics programs, as it minimizes the amount of manual preprocessing required. IDATM has been tested on a range of crystallographically determined structures, including poorly determined structures, with a successful assignment of hybridization for over 99% of the atoms in the set.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120716
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  • 6
    Electronic Resource
    Electronic Resource
    Recent computational developments with the self-consistent electron pairs method and application to the stability of glycine conformers (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 2 (1981), S. 266-272 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Significant improvements in calculational efficiency and capability with the self-consistent electron pairs (SCEP) method has resulted from several new computational developments. A new procedure for constructing the important internal Coulomb and exchange operators has substantially reduced the preiteration time. A general scheme for utilizing molecular symmetry has been used to advantage in reducing the number of pair functions and external operators that must be found explicitly at each iteration. A projection operator tool has been implemented and found to be quite effective at minimizing the number of iterations required at some point on a potential energy surface when an SCEP wavefunction exists for some nearby point. These and other improvements in the program construction have yielded sizable reductions in time for some representative test cases, including water and a potential energy curve for formaldehyde. The new SCEP program also performs low-order perturbation theory treatments and coupled electron pair approximation (CEPA) calculations using the same operator approach. The usefulness of the approach is demonstrated by very large scale calculations on the stability of the two interstellar glycine conformers. These calculations involve the variational treatment of 82,205 symmetry-adapted singly and doubly substituted configurations involving 225 internal electron pairs.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540020308
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  • 7
    Electronic Resource
    Electronic Resource
    Polymer drying. VII. 1H-NMR studies of evaporation from liquid saturated poly(styrene-co-divinylbenzene) (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1155-1161 
    Details
    ISSN: 0887-624X
    Keywords: adsorption ; desorption ; association ; polystyrene ; NMR ; polymer transitions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composition-studies were carried out in which samples of films composed of poly(styrene-co-divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the 1H-NMR signals and residual weight of sorbed liquid were monitored. The correlations, of 1H-NMR line-widths with the corresponding log of the number, αt of residual sorbed molecules per monomer unit show that sharp changes occur as αt passes through αG the composition that exists when all the liquid not sorbed (i.e., not present within the liquid-saturated particles), has been eliminated, and again as αt passes through αg the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T1 relaxation times with log αt show that sharp changes occur when αt becomes equal first to α′s and then to α′g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300622
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  • 8
    Electronic Resource
    Electronic Resource
    Inclusion volume solid-phase synthesis (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 240-244 
    Details
    ISSN: 1075-2617
    Keywords: solid-phase synthesis ; peptide synthesis ; multiple synthesis ; inclusion volume synthesis ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-phase synthesis of peptides was carried out using only the volume of the solvent included in the swollen solid-phase resin beads [inclusion volume synthesis]. This approach enables (i) the use of higher concentrations of activated amino acids, resulting in increased coupling rates, (ii) drastically decreased consumption of solvents, and (iii) the construction of multiple peptide synthesizers having virtually no reaction vessels.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310020402
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  • 9
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR investigations of three fluorinated steroids (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 501-505 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; solid-state NMR ; 13C NMR ; magic angle spinning ; steroids ; fluorinated compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-resolution carbon-13 NMR spectra were obtained for three solid fluorinated steroids. Assignments were carried out using several approaches, including two-dimensional spectra of the compounds in solution. Solid-state and solution-state chemical shifts are compared. Signals from one of the fluorine-containing carbons in each compound show the effect of interplay between shielding, dipolar and indirect scalar (J) coupling tensors. One sample is found to be a mixture of two polymorphic forms.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330702
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  • 10
    Electronic Resource
    Electronic Resource
    1H and 13C NMR of substituted dibenzo-14-crown-4 ethers (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 375-378 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; Crown ethers ; Dibenzo-14-crown-4 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dibenzo-14-crown-4 and eight substituted dibenzo-14-crown-4-ethers were studied by 1D and 2D 1H and 13C NMR and their chemical shifts are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260320614
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