ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The solution conformations of several N-urethanyl-L-amino acids in 0.2-0.002M chloroform and 0.2M dimethylsulfoxide have been investigated by using vibrational circular dichroism (VCD), ir absorption, and 13C-nmr spectroscopies. Both the N-carbobenzoxy (N-CBZ) and N-t-butoxycarbonyl derivatives of L-alanine, L-proline, L-valine, and L-phenylalanine, and N-CBZ-serine were studied. The 13C-nmr results indicate that the molecules occur predominantly as the cis isomer about the C—N peptide bond at room temperature. The interpretation of the strong VCD couplet in the carbonyl-stretching region using the degenerate coupled oscillator model is consistent with the conformational range of φ = -60° to -90° and ψ = 30° to 90° for molecules forming acid dimers. Conformations with an intramolecularly hydrogen-bonded C7 ring are also present, which give rise to biased VCD features in the NH-, CH-, and C=O-stretching regions that can arise due to vibrationally generated ring currents.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360261105
Permalink