Boc is also N α-position protecting group for SPPS. Boc amino acid is attached to an insoluble support resin via a HF cleavable linker. Deprotection of Boc, is accomplished by treatment of the amino acid with TFA. The second Boc amino acid is coupled utilizing a pre-activated species or in situ activation. After the desired peptide is synthesized, the resin bound peptide is deprotected and detached from the solid support via HF cleavage. However, both N α-position protecting group and side chain protecting groups are acidic removable, and rounds of strong acid treatment would degrade the peptide, so this method is not very commonly used.
