Solid-Phase Peptide Cyclization with Two Disulfide Bridges.

Solid-phase peptide synthesis (SPPS) is the method of choice that enables the access to a library of synthetic bioactive peptides. Cyclization due to the presence of disulfide bridges is of great importance for certain proteins and peptides since it increases their stability against proteolysis by constraining the conformations of these peptides and proteins. Here we describe the solid-phase peptide cyclization by on-resin strategy represented in the synthesis of peptides containing two disulfide bridges. The presence and/or the absence of free SH groups can be investigated by Ellman's test.