Proline is often found as a turn inducer in peptide or protein domains. Exploitation of its restricted conformational freedom led to the development of the d-Pro-l-Pro (corresponding to (R)-Pro–(S)-Pro) segment as a “templating” unit, frequently used in the design of β-hairpin peptidomimetics, in which conformational stability is, however, inherently linked to the cis–trans isomerization of the prolyl amide bonds. In this context, the stereoelectronic properties of the CF 3 group can aid in conformational control. Herein, the impact of α-trifluoromethylated proline analogues is examined for the design of enhanced β-turn inducers. A theoretical conformational study permitted the dipeptide (R)-Pro–(R)-TfmOxa (TfmOxa: 2-trifluoromethyloxazolidine-2-carboxylic acid) to be selected as a template with an increased trans–cis rotational energy barrier. NMR spectroscopic analysis of the Ac-(R)-Pro–(R)-TfmOxa–(S)-Val-OtBu β-turn model, obtained through an original synthetic pathway, validated the prevalence of a major trans–trans conformer and indicated the presence of an internal hydrogen bond. Altogether, it was shown that the (R)-Pro–(R)-TfmOxa template fulfilled all crucial β-turn-inducer criteria.

Original languageEnglish
Pages (from-to)2513-2518
Issue number19
Publication statusPublished - 15 Jul 2019

    Research areas

  • backbone constraints, beta-turn inducers, isomerization, NMR spectroscopy, peptidomimetics

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