Abstract: | Empirical force-field calculations and ir and 1H-nmr spectra indicate that five-membered (C5) and seven-membered (C ) hydrogen-bonded rings are the preferred conformations of acetyl-L -Phe p-acetyl and p-valeryl anilides in nonpolar media. The C5/C ratio was found to be dependent on the dryness of the solute and the solvent. This fact and the results from conformational-energy calculations suggest that a molecule of water participates in the stabilization of the C conformation. |