Polar Hinges as Functionalized Conformational Constraints in (Bi)cyclic Peptides

Two polar hinges for cyclization of peptides have been developed, leading to bicyclic peptides and cyclized peptides with improved solubility and biological activity. Increasingly, we note that a good aqueous solubility of peptides is an absolute prerequisite, not only to allow handling and purification of our target peptides but also being crucial for biological activity characteristics. Compared to earlier hinges, the 1,1',1"-(1,3,5-triazinane-1,3,5-triyl)tris(2-bromoethanone) (TATB) and 2,4,6-tris(bromomethyl)-s-triazine (TBMT), each containing three nitrogen atoms are structurally similar but chemically very different. Both were accessible in a one-step fashion from bromoacetonitrile. TATB and TBMT are very suitable for the preparation of more soluble bicyclic peptides. Azide-modified TATB and TBMT derivatives provide hinges for the preparation of cyclized peptides for incorporation on scaffolds to afford protein mimics.