Influence of achiral units with gem-dimethyl substituents on the helical character of aliphatic oligourea foldamers.

The structures of various urea oligomers incorporating one or two central achiral 1,2-diamino-1,1-dimethylethane (DADME) units have been investigated in solution and in the crystalline state. These diamine monomers are analogous to the achiral helicogenic amino acid Aib (alpha-aminoisobutyric acid). Oligomers were found to fold into helical conformations with DADME units inducing local deviations from the canonical helix geometry of urea foldamers.