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  • 11
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1911-1921 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Isobutyl-L-aspartate oligomers, Z-(α-i-Bu-Asp)2n-OEt (n = 1-5), where Z = benzyloxycarbonyl and OEt = ethyl ester, were prepared stepwise, and their conformation in solution was investigated by optical rotation, circular dichroism (CD), and NMR spectroscopy. The oligomers up to hexamer existed only in a disordered form. An ordered structure began to appear at octamer and decamer in chloroform and 2,2,2-trifluoroethanol. The ordered structure was more favorable for N-unprotected oligomers, H-(α-i-Bu-Asp)2n-OEt, in comparison with the corresponding Z-(α-i-Bu-Asp)2n-OEt. The effects of oligomer concentration and temperature on the structure were slightly observed. The most likely ordered structure was a β form caused by intramolecular association.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3867-3878 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic and optically active 3-pyrrolidinecarboxylic acids (β-proline) were synthesized, and their polymers, poly[(RS)-β-proline] and poly[(R)-β-proline], were prepared by the polycondensation reaction of the p-nitrophenyl esters. Model compounds, N-cyclopentylcarboxylic acid pyrrolidide and N-cyclopentylcarbonyl-(R)-3-pyrrolidinecarboxylic acid pyrrolidide, were synthesized to elucidate the conformation of the polymer. The solution properties of poly[(R)-β-proline] and the model compounds were investigated by means of circular dichroism (CD) and NMR spectroscopy. The spectral patterns of the polymer and model compounds were similar in various solvents. Poly[(R)-β-proline] and poly[(RS)-β-proline] showed identical NMR spectra. These results suggest that poly[(R)-β-proline] may exist in a random conformation consisting of mixtures of cis and trans amide bonds. The conformational study of cyclopentanecarboxylic acid pyrrolidide by NMR spectroscopy with a shift reagent, Eu(fod)3, in CDCl3 implied that the plane containing the amide group bisects the cyclopentane ring. This suggests that each amide plane in the polymer in chloroform may also bisect the pyrrolidine ring.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 1247-1260 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The equimolar reactions of 1,1-diphenyl-n-butyllithium-3,4-d5 (RLi) with isoprene (I) and isoprene-1,4-d4 (Id) were carried out in benzene-d6 quantitatively to give isoprenyllithiums, RILi and RIdLi, respectively. From the NMR spectrum of the RILi it was proposed that the isoprene unit had cis-1,4, cis-4,1 and some unknown structures in benzene-d6. When RILi was prepared in the presence of about one equivalent of THF to RILi, the anion was considered to include an isoprene unit in cis-1,4, trans-1,4, cis-4,1, and probably 3,4 structures. The same anion was obtained even if an equimolar THF was added afterward to the RILi prepared in benzene-d6 The RLi was reproduced by the reverse reaction from RILi, when a large excess of THF was added or the temperature of the solution was elevated. The results obtained were correlated with those of anionic polymerizations of isoprene by lithium initiators.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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