Multicyclic peptides manufactured via scaffold-assisted CLIPS/CuAAC technology

Cyclic peptides have emerged as a highly potent class of molecules for therapeutic applications. So far, reported synthetic methodologies for the production of cyclic peptides mostly focus on mono- and bicyclic constructs, as the synthesis of higher-order multicycles is often very difficult and not generally applicable. The research described in this thesis focusses on the development of a general scaffold-based cyclization technology for the manufacturing of tri-, tetra-, penta- and hexacyclic peptides.
Chapter 2 describes the one-pot synthesis of tricyclic peptides via CLIPS/CuAAC ligation-cyclization of linear peptides on T3 scaffolds. The concept was successfully applied in peptide library format, and tricycles with nanomolar affinity against uPA were identified.
The synthesis of novel T4 CLIPS/CuAAC scaffolds, which could be used for the production of isomerically pure tricycles, is described in chapter 3. No limitations with respect to the loop size and type of amino acids was observed. Subsequently, the identification of two novel tricyclic antimicrobials, active against Staphylococcus aureus and Escherichia coli, is described in chapter 4. Furthermore, the latter tricycle showed high specificity, as 0% haemolytic activity was observed.
In chapter 5, the combination of chemoenzymatic head-to-tail cyclization and the T4 CLIPS/CuAAC technology is depicted, along with the identification of dual tetracyclic inhibitors, active against both uPA and FXIIa in the low micromolar range.
Finally, chapter 6 describes the synthesis of novel T6 CLIPS/CuAAC scaffolds, which could be reacted with either linear- and head-to-tail cyclized peptides for the formation of penta- and hexacyclic peptide constructs, respectively.