Conformational Preferences of N-acetyl-L-leucine-N-methylamide. Gas-Phase and Solution Calculations on the Model Dipeptide

M.F.MASMAN, S. LOVAS, R M. MURPHY, R.D.ENRIZ, A.M.RODRIGUEZ

JOURNAL OF PHYSICAL CHEMISTRY A

Am. Chem Sosc.

Año: 2007 vol. 111 p. 10682 - 10691

1089-5639

A DFT study of N-acetyl-L-leucine-N¢-methylamide conformers in the gas phase and in solution was carried out. The theoretical computational analysis revealed 43 different conformations at the B3LYP/6-31G(d) level of theory in the gas phase. In addition, the effects of three solvents (water, acetonitrile, and chloroform) were included in the calculations using the isodensity polarizable continuum model (IPCM) and the Poisson-N-acetyl-L-leucine-N¢-methylamide conformers in the gas phase and in solution was carried out. The theoretical computational analysis revealed 43 different conformations at the B3LYP/6-31G(d) level of theory in the gas phase. In addition, the effects of three solvents (water, acetonitrile, and chloroform) were included in the calculations using the isodensity polarizable continuum model (IPCM) and the Poisson-- Boltzmann self-consistent reaction field (PB-SCRF) method. The stability order of the different conformers in solution has been analyzed. The theoretical results were compared with some experimental data (X-ray, IR, and NMR).