A decamer of a β-amino acid analogue of l-proline,(3R)-carboxy pyrrolidine (β-proline), was synthesized from a readily available (R)-glycidol. It was found to possess a rigid secondary structure, as evidenced by its CD spectrum. The β-proline decamer, however, failed to bind to profilin, whereas the corresponding α-l-proline decamer bound tightly to this protein.