ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
D,L-Alanine-NCA containing 1,5% 15N and D,L-Valine-NCA containing 2,4% 15N, were synthesized and polymerized under various conditions. 36,48 MHz 15N NMR spectra of the resulting poly(D,L-amino acid)s were measured in trifluoroacetic acid, and the peak for the isotactic triad in each polymer was assigned by comparison with other alanine- and valine containing polypeptides. In the case of D,L-alanine-NCA the formation of isotactic blocks was favored, when the “activated monomer mechanism” was operating. In the case of D,L-valine-NCA, however, syndiotactic blocks were predominantly formed under the same reaction conditions. The initiation with primary amines results in almost atactic sequences. A helical secondary structure of the growing peptide chain is found to be an unnecessary condition for the stereospecificity of a NCA polymerization. The synthesis of Boc-D,L-Ala-D,L-Ala-OMe from tert-butoxycarbonyl-D,L-alanine and D,L-alanine methyl ester was carried out under various conditions, and the stereospecifity was investigated by means of natural abundance 15N NMR spectra. The results are discussed with respect to the polymerization of D,L-alanine-NCA and D,L-valine-NCA.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1979.021800709
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