Impact of aza-substitutions on the preference of helix handedness for β-peptide oligomers: a DFT study.

We studied the helix preference of the heterochiral pentamers of cis -2-aminocyclohexanecarboxylic acid ( c -ACHC) and cis -2-aminocyclopentanecarboxylic acid ( c -ACPC) with alternating backbone configurations by replacing C β -aza- or C α -aza-peptide residues using DFT methods in solution. The helix-handedness preferences of two pentamers were strongly affected by the replacement positions ( i.e. , chiralities) but not depending on the solvent polarity.