The 2-(p-biphenylyl)-2-propyloxycarbonyl (Bpoc) group was examined as an Nα-protecting group in the stepwise assembly of the MAP Kinase ERK2 [178–188; Thr (P) 183, Tyr (P) 185] peptide. The mild acid deprotection of the Bpoc group permitted (i) incorporation of a fully protected phosphothreonyl derivative and (ii) a TFA-based final cleavage step. The first five C-terminal residues (184–188) were incorporated in the Fmoc mode of peptide synthesis, ...