A strategy for the synthesis of peptide mimics of the poly-L-proline type II secondary structure from 4-substituted prolines is presented. Dimeric and trimeric oligomers composed of 3-substituted prolines are shown by NMR to preferentially populate the poly-L-proline type II secondary structure in both CDCl3 and D2O. Oligomers composed of 4-substituted prolines thus imitate the desired backbone conformation and are able to incorporate non-prolyl side chains on the proline backbone.