GAP Peptide Synthesis through the Design of a GAP Protecting Group: An Fmoc/tBu Synthesis of Thymopentin Free from Polymers, Chromatography and Recrystallization

Abstract A novel method for Fmoc/ t Bu solution‐phase peptide synthesis and the development of a new benzyl‐type group‐assisted purification (GAP) protecting group is reported. This GAP protecting group is utilized in place of a polymer support, facilitating C→N Fmoc peptide synthesis without chromatography or recrystallization. The GAP group can be added and removed in high yield, and was used to synthesize over 1 gram of the immunostimulant, thymopentin, in high overall yield (83 %) and purity (99 %).