ISSN:
0006-3525
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
We have examined intramolecular hydrogen bonding in four homologous compounds, N-acetyl-, N-propionyl-, N-i-butyryl-, and N-pivaloyl-proline-methylamide, in methylene chloride, by means of 1H-nmr and ir measurements. At room temperature, the major trans conformer of MeCO-Pro-NHMe appears to be approximately 68% intramolecularly hydrogen bonded, the trans conformers of EtCO-Pro-NHMe and i-PrCO-Pro-NHMe are approximately 75% intramolecularly hydrogen bonded, and t-BuCO-Pro-NHMe is approximately 50% intramolecularly hydrogen bonded. Thus, the internally hydrogen-bonded state (C7 or γ-turn) is significantly less populated for the N-pivaloyl compound than for the other three molecules in this series. Variable temperature measurements indicate that for each proline derivative there is very little enthalpic difference between the intramolecularly hydrogen-bonded and nonhydrogen bonded states of the trans rotamer. Changing the N-terminal acyl group also affects intramolecular hydrogen bonding (including β-turn formation) in end-blocked Pro-Gly dipeptides.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/bip.360320309
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