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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, Structure, and Antimalarial Activity of Some Enantiomerically Pure, cis-fused cyclopenteno-1,2,4-trioxanes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 647-662 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two pairs of enantiomerically pure cis-fused cyclopenteno-1,2,4-trioxanes (7, ent-7 and 8, ent-8) are prepared (Schemes 1-3). Their identities are established by dye-sensitized photo-oxygenation of ent-7 and 8, ent-8 to the allylichydroperxides, reduction to the corresponding alcohols, and conversion to the (1S)-camphanates (Scheme 4), the structures of which are determined by X-ray analysis. The dynamic properties of ent-7 are investigated by NMR spectroscopy and PM3 calculations. Evidence for an easily accessible twist-boat conformation is obtained. The in vitro and in vivo antimalarial activities of 7, ent-7,8, and ent-8 as well as those of the racemic mixtures are evaluated against Plasmodium falciparum, P. berghei, and P. yoelii. No correlation is observed between configuration and activity. Racemates and pure enantiomers have commensurate activities. The mode of action on the intraerythrocytic parasite is rationalized in terms of close docking by the twist-boat conformer of the trioxane on the surface of a molecule of heme, single-electron transfer to the O—O σ* orbital, and scission to the acetal radical which then irreversibly isomerizes to a C-centered radical, the ultimate lethal agent (Scheme 5).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780312
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  • 2
    Electronic Resource
    Electronic Resource
    The absolute configuration of the enantiomers of 6-chloro-9-(4′-diethylamino-1′-methylbutyl)-amino-2-methoxyacridine (quinacrine) (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 436-437 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; quinacrine ; enantiomers ; enantioselectivity ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute configurations have been assigned to the enantiomers of the antimalarial drug quinacrine dihydrochloride. Condensation of (-)-(R)-4-amino-1-diethylaminopentane (from L-glutamic acid) with 6,9-dichloro-2-methoxyacridine gave (-)-(R)-6-chloro-9-(4′-diethylamino-1′-methylbutyl) amino-2-methoxyacridine [(-)-(R)-quinacrine] while (+)-(S)-quinacrine was obtained from the enantiomeric diamine.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030510
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  • 3
    Electronic Resource
    Electronic Resource
    Chiroptical properties and absolute configuration of pyrroloisoquinoline antidepressants (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 169-172 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; chirality ; circular dichroism ; isoquinoline ; enantiomers ; alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism (CD) spectra were determined for the bioactive (+)-enantiomers of 1 · HCl, 3 · HCl, and 4 · HBr to characterize the chiroptical properties of these pyrroloisoquinoline antidepressants. The compounds showed a low-intensity negative CD band with much fine structure between 252 and 272 nm, a medium negative CD band with fine structure between 215 and 225 nm, and a high-intensity negative CD maximum between 198 and 203 nm. Except for amplitude variation, the three CD spectra were essentially superimposable in sign and position of the bands. The CD curves for the (-)-enantiomers of 1 · HCl and 4 · HBr were opposite in sign and comparable within 5% to the (+)-enantiomers. The results are consistent with the previously assigned (Maryanoff et al. J. Med. Chem. 30:1433-1454, 1987) absolute configurations of (6S, 10bR) for 1 and 3, and (6R, 10bR) for 4. Chirality 10:169-172, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.26
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  • 4
    Electronic Resource
    Electronic Resource
    NMR spectra of the porphyrins. 38For Part 37, see Ref. 1. - Conformational analysis of azacycloheptane and azacyclooctane using a novel cobalt(III) porphyrin shift reagent (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 343-347 
    Details
    ISSN: 0749-1581
    Keywords: Cobalt(III) porphyrins ; Conformations ; Azacyclooctane ; Azacycloheptane ; NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel NMR shift reagent, cobalt(III) meso-tetraphenylporphyrin (CoTPP) was used to determine the conformations of azacycloheptane and azacyclooctane ligands complexed to the metalloporphyrin. Using the observed ring current shifts and a previously calibrated ring current model, the best agreement between the observed and calculated ring current shifts for azacycloheptane was obtained for a chair conformation, in agreement with previous theoretical and experimental studies on the conformational stability of seven-membered rings. The ring current shifts for azacyclooctane are best interpreted in terms of a mixture of many conformations. These results suggest that CoTPP may be useful as a probe of other conformationally mobile ligands.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280412
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  • 5
    Electronic Resource
    Electronic Resource
    NMR spectra of the porphyrins. 34For Part 33, see Ref. 1. - Determination of the conformational equilibria of monosubstituted piperidines at room temperature using cobalt(III) porphyrin shift reagents (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 334-344 
    Details
    ISSN: 0749-1581
    Keywords: Cobalt(III) porphyrins ; Conformational equilibria ; Piperidines ; Shift reagents ; Substituent chemical shifts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H and 13C NMR spectra of piperidine and eight monosubstituted piperidines and their spectra with cobalt(III) mesotetraphenylporphyrin chloride (CoTPPCl) and cobalt(III) octaethylporphyrin chloride (CoOEPCl) were assigned using a range of NMR techniques. When complexed to the porphyrin shift reagent the axial and equatorial conformers were in slow exchange at room temperature, allowing the determination of conformational equilibria and substituent chemical shifts (SCS).Conformational free energy differences (-ΔG°, kcal mol-1) obtained for 4-substituted piperidines using CoOEPCl at 298 K were 0.5 (X = Br), 0.7 (X = OH), 0.8 (X = carbethoxy), 1.8 (X = Me) and 〉 1.6 (X = Ph). These were in good agreement with literature values. For CoTPPCl the corresponding values were -0.2 (axial conformation favoured), 0.3, 0.7, 1.4 and 〉 1.6, indicating that an axial orientation of the 4-substituent was more favoured than with CoOEPCl. This difference was rationalized in terms of steric and electrostatic interactions between the piperidine substituent and the phenyl rings of CoTPPCl. In both cases proton and 13C SCS values were in good agreement with those in the literature.With 1-, 2- and 3-methylpiperidines unusual results were obtained for both porphyrins. For 3-methylpiperidine -ΔG° was only 0.8 kcal mol-1 compared with a literature value of 1.6 kcal mol-1, whilst for 1- and 2- methylpiperidine reduction of the shift reagent to cobalt(II) occurred. With 1-methylpiperidine the reduction was complete and no complexation was observed, but only some of the shift reagent was reduced by 2-methylpiperidine and the remaining shift reagent complexed to the amine.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260412
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