Pseudoprolines as Removable Turn Inducers: Tools for the Cyclization of Small Peptides

The cyclization of small peptides which do not incorporate turn inducers is often difficult. We have
developed a method involving the use of removable turn inducers, in the form of pseudoprolines,
for the cyclization of difficult peptide sequences. The pseudoprolines induce a cisoid amide bond in
the peptide backbone which facilitates cyclization. They are then readily removed to yield a cyclic
peptide that does not contain any turn inducers.