Rational incorporation of emergent fluorinated groups into amino acids and target peptidesGregorc, Jure (Avtor) Iskra, Jernej (Mentor) Brigaud, Thierry (Komentor) amino acidspeptide chemistrytrifluoromethylthiolationlate-stage functionalizationendomorphin-1SPPShydrophobicityoxidation of sulfides$^{19}$F NMR spectroscopyThe introduction of fluorine or fluorinated functional groups has become a key strategy in agrochemical and pharmaceutical development. In peptide chemistry, fluorination has been shown to enhance metabolic stability, stabilize desired secondary structure and provide insight into biological interactions via $^{19}$F NMR spectroscopy. Despite their promising properties, chalcogen-associated fluorinated groups remain underexplored in the peptide arena. Among these, the trifluoromethylthio (CF$_3$S) group has emerged as a privileged substituent due to its lipophilicity profile and strong electron-withdrawing properties. In this study, we developed an efficient method for direct C(sp$^2$)–H trifluoromethylthiolation of aromatic amino acids (tryptophan, tyrosine, DOPA), as well as their biologically relevant monoamine analogs, such as serotonin, dopamine and tyramine. The developed method enabled the late-stage incorporation of the CF$_3$S moiety into tryptophan-containing peptides and facilitated the gram-scale synthesis of enantiopure Fmoc-protected building blocks (77–93 % yield). The latter were utilized in SPPS of model peptides and endomorphin-1 analogs. Furthermore, the local hydrophobic effect of the CF$_3$S group when incorporated into the peptide was investigated. A substantial increase in hydrophobic interactions was revealed, showing the potential of site-selective trifluoromethylthiolation for improving the drug-like properties of peptides. As part of this work, a library of fluorinated endomorphin-1 (EM1) analogs was synthesized, featuring various CF$_3$(S)-based modifications. A total of 10 ligands were evaluated in vitro for μ- and δ-opioid receptor binding affinity and functional activity, exhibiting comparable binding affinities (up to 1.38 nM K$_i$) to the parent EM1. In the final part of the dissertation, the selective oxidation of CF$_3$S-amino acids to obtain corresponding trifluoromethyl sulfoxide and sulfone derivatives was investigated. The oxidized building blocks were successfully incorporated into peptides via SPPS, and their physico-chemical properties were analyzed. Additionally, we have developed a high-yielding synthetic route to protected perfluoro-tert-butyl serine analogs via Mitsunobu reaction. The results presented in this doctoral dissertation advance the methodology for the incorporation of the CF$_3$S group and its higher oxidation congeners into amino acids and target peptides via SPPS or late-stage functionalization. The conducted physicochemical and biological activity studies enhance our understanding of the impact of sulfur-associated fluorinated motifs on peptide properties and pave the way for further application of emergent fluorinated functional groups in the design of peptide-based therapeutics or biomaterials.20252025-07-02 15:15:35Doktorsko delo/naloga170204VisID: 23024COBISS_ID: 243814403sl