AbstractThe1H‐nmr spectra (270 MHz) of cyclic di‐ and tri‐L‐azatidine‐2‐carboxylic acid [cy‐clo(L‐Aze)2and cyclo(L‐Aze)3] were determined in CDCl3and D2O and computer simulated. The spectral results were compared with those obtained with cyclo (L‐Pro)2and cyclo (L,‐Pro)3. In CDCl3and D2O solution, the four membered ring of cyclo (L‐Aze)2is puckered with the α‐proton in a pseudo‐axial position, and the ϕ angle is smaller in absolute value than −60°, as found for cyclo (L‐Pro)2,. The puckering of the four‐membered ring of cyclo(L,‐Aze)3in CDCl3has the α‐proton in a pseudo–equatorial position and ϕ angle larger in absolute value than −60°, in agreement with cyclo(L‐Pro)3. In D2O, cyclo(L‐Aze)3was found to interconvert rapidly between different conformers. In the azetidine cyclic peptides studied, the range of values found for the ϕ angles was smaller than in the related proline cyclic peptides, i