Advances towards Aromatic Oligoamide Foldamers: Synthesis and X-ray Structures of Dimeric Arylopeptoids with Conformation-Directing Side Chains

We have efficiently synthesized 36 arylopeptoid dimers with ortho-, meta-, and para-substituted aromatic backbones and tert-butyl or phenyl side chains. The dimers were synthesized by using a submonomer method on solid phase, by applying a simplified common set of reaction conditions. X-ray crystallographic analysis of two of these dimers disclosed that the tert-butyl side chain invokes a cis amide conformation with a comparatively more closely packed structure of the surrounding aromatic backbone while the phenyl side chain results in a trans amide conformation with a more open, extended structure of the surrounding aromatic backbone.