A protectedpeptide containing phosphoserine was successfully synthesized by the solid-phase method using the oximeresin. The protected phosphopeptide was utilized to further elongation to a longer peptide and conjugation to a template molecule.
Boc-phosphoamino acid derivatives with O-[di(4-nitrobenzyl)- or dicyclohexylphosphono]-protection were prepared for application to the Boc-mode solid-phase synthesis of phosphopeptides. These protecting groups are both stable to TFA, but removable with a combination of trifluoromethanesulfonic acid and methylthiobenzene in TFA. Of these derivatives, Nα-Boc-O-(dicyclohexylphosphono)serine and Nα-Boc-O-(dicyclohexylphosphono)threonine were obtained as crystalline compounds to be favorably utilized as starting materials for solid-phase synthesis using an automated peptide synthesizer. On the other hand, Nα-Boc-O-(dicyclohexylphosphono)tyrosine and all of the O-[di(4-nitrobenzyl)]phosphono derivatives were prepared as crystalline cyclohexylammonium or dicyclohexylammonium salts.