Acid cleavage/deprotection in Fmoc/tBu solid-phase peptide synthesis.

In general, a solid-phase peptide synthesis (SPPS) consists of the assembly of a protected peptide chain on a polymeric support (=synthetic step) and the subsequent cleavage/deprotection to release the crude, deprotected peptide from the solid support (=cleavage step). Usually, these two steps are followed by chromatographic purification of the crude peptide (see Chapters 1,2,4, and 5, PAP). The techniques to synthesize protected peptides or peptide fragments are discussed in Chapter 14. This chapter describes exclusively the cleavage step in the FmocltBu-SPPS with TFA as cleavage reagent leading to fully deprotected peptides (see Note 1) (I). All of the cleavage procedures that are exemplified in Section 3. of this chapter hold for peptides synthesized under the following conditions: