High quality resins for solid phase peptide synthesis.
Further resin and linker selection can improve a synthesis, particularly in the case of a challenging peptide synthesis. Sterically bulky linkers like the Cl-TCP(Cl) or 2-chlorotrityl linker show suppression of side reactions like diketopiperazine and piperidinyl alanine formation.1 The completed peptide and side chain protecting groups can be cleaved from the resin using concentrated trifluoroacetic acid (TFA) for most peptide linkers. Hyperacid sensitive linkers, such as Cl-TCP(Cl) or 2-chlorotrityl can be cleaved with dilute TFA (<1%) to furnish a free, solution phase peptide with side chain protection, intact for convenient post-synthetic modifications. The Cl-TCP(Cl) linker improves upon the standard 2-chlorotrityl with improved stability at elevated temperature without sacrificing hyper acid sensitivity.