Unveiling the conformational landscape of achiral all- cis tert -butyl β-peptoids.

The synthesis and conformational study of N -substituted β-alanines with tert -butyl side chains is described. The oligomers prepared by submonomer synthesis and block coupling methods are up to 15 residues long and are characterised by amide bonds in the cis -conformation. A conformational study comprising experimental solution NMR spectroscopy, X-ray crystallography and molecular modeling shows that despite their intrinsic higher conformational flexibility compared to their α-peptoid counterparts, this family of achiral oligomers adopt preferred secondary structures including a helical conformation close to that described with (1-naphthyl)ethyl side chains but also a novel ribbon-like conformation.