Trifluoromethyl group: an effective xenobiotic function for peptide backbone modification

Peptides modified with fluoroalkyl functions in key backbone positions have been scarcely studied so far. Thus, little is known about their synthesis, their structural and physico-chemical properties, and their biological features. Our interest in this field of research led to the development of stereocontrolled synthetic protocols, both in solution and in the solid phase, for many different fluoroalkyl peptidomimetics, which are reviewed in this paper: (a) bis-trifluoromethyl (Tfm) analogues of Pepstatin A, which are nanomolar and selective inhibitors of the protozoal aspartyl protease Plasmepsin II; (b) Tfm-malic peptidomimetics that are micromolar inhibitors of some matrix metalloproteinases; (c) partially modified retro (PMR) and retro-inverso (PMRI) psi[CH(CF3)NH] peptides with a strong proclivity to assume turn-like conformations; (d) psi[CH(CF3)NH] peptide mimics having a great potential as hybrids between natural peptides and hydrolytic transition state analogues; (e) the first PMR peptides incorporating a trifluoroalanine surrogate. These novel classes of fluorinated peptide mimics are likely to represent just the top of an iceberg formed by new peptidomimetic structures with unique biomedicinal and pharmaceutical properties.