The current article reports on the synthesis of a new type of cyclic peptidosteroid, in which a bile-acid-based scaffold was used for the conformational restriction of a loop-like peptide. Convergent coupling of two tetrapeptides to the non-peptidic steroidal entity was carried out once in the classical C-to-N and once in the non-classical N-to-C direction. Peptide backbone cyclisation was then carried out, giving rise to a ring size equivalent to approximately 12 amino acids. This type of construct will be used in the development of a peptide vaccine against measles.

The current article reports the design, synthesis and biochemical evaluation of a cyclic bile acid-peptide conjugate as a mimic of the loop-like structure of the measles virus haemagglutinin noose epitope (HNE). This macrocyclic structure was assembled by solid phase synthesis. Scaffold-peptide ring closure was achieved via the introduction of a succinate linker. After disulfide bridge formation with iodine, the desired 14 amino acid cyclic conjugate was obtained with overall yields between 15 and 35%. NMR analysis supports the presence of a helical conformation in the Q384-G388 pentapeptide portion, in agreement with the organisation of this chain in the native protein. The compound was found to have increased biostability compared to stabilised linear peptides, displayed good binding towards monoclonal antibodies known to bind to HNE and thus has potential in an alternative peptide-based measles vaccine.