Most of the peptides for both research and production are synthesized in the solid phase mode using a two-dimensional protection scheme. A third kind of protecting group is incorporated for synthesizing some peptides, such as cyclic peptides, which are usually orthogonal to the first two.

Herein, we introduce a fourth category of protecting groups that are stable under the conditions used to remove the first three, and, after a manipulation, they are removed at the end of the synthetic process. This step can be performed when the peptide is still anchored to the resin, or once the peptide is in solution. This new concept of protecting group based on the Safety-Catch concept facilitates the synthesis and manipulation of complex peptides.