Conformational properties of N-acetyl-L-alanine N',N'-dimethylamide.

Ab initio/DFT analysis of the conformational properties of free Ac-Ala-NMe2 (N-acetyl-L-alanine-N',N'-dimethylamide) in terms of the N-H···O, N-H···N, C-H···O hydrogen bonds and Cδ+ = Oδ- dipole attractions was performed. The Ala residue combined with the C-terminal tertiary amide prefers an extended conformation and that characteristic of the (i + 1)th position of the βVIb turn. These can be easily remodelled into a structure compatible with the (i + 1)th position of the βII/βVIa turn. The residue has also the potential to adopt the conformation accommodated at both central positions of the βIII/βIII' turn or the (i + 1)th position of the βI/β'I turn.