Solution conformations of some azetidine cyclic peptides

✍ Scribed by J.-P. Meraldi; E. R. Blout; R. Boni; A. S. Verdini

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 603 KB
• Volume: 17
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1978.360171009

✦ Synopsis

The 'H-nmr spectra (270 MHz) of cyclic di-and tri-~-azetidine-2-carboxylic acid [cyclo(L-Aze)z and cyclo(~-Aze)a] were determined in CDCls and DzO and computer simulated. The spectral results were compared with those obtained with cyclo(L-Pro)z and cyclo(L-Pro)3. In CDC13 and D20 solutions, the four-membered ring of cyclo(L-Aze)z is puckered with the wproton in a pseudo-axial position, and the $I angle is smaller in absolute value than -60", as found for cyclo(L-Pro)*. The puckering of the four-membered ring of cyclo(L-Aze)a in CDC13 has the a-proton in a pseudo-equatorial position and a rp angle larger in absolute value than -60°, in agreement with cyclo(L-Pro)s. In D20, cyclo(L-Aze)a was found to interconvert rapidly between different conformers. In the azetidine cyclic peptides studied, the range of values found for the $I angles was smaller than in the related proline cyclic peptides, indicating greater rigidity in the four-membered ring.

* This is paper XXI of the series "Cyclic Peptides." Paper XX of this series (Boni et al.)