Incorporation of Ahc into Model Dipeptides as an Inducer of a β-Turn with a Distorted Amide Bond. Conformational Analysis

The proline residue of dipeptides Ser-Pro and Pro-Ser has been replaced by 7-azabicyclo[2.2.1]heptane-1-carboxylic acid (Ahc), a conformationally restricted analogue of proline that is capable of mimicking distorted amides. The conformational analysis of the new peptides in the solid state revealed that the Ahc-Ser sequence displays a type I β-turn, which includes a distorted amide bond. In contrast, the Ser-Ahc sequence exists in a nonfolded structure.