Moreover, we could introduce the EBX core selectively on the N-terminus (3t) in presence of Boc-protected Lys during solid phase synthesis, and the acidic stability of the EBX core allowed us to cleave the resin and Lys protecting group using TFA. The protecting group on other side chains such as Glu, Thr and Asp can be also removed efficiently without influencing the overall yield (3u). By using a well-establish orthogonal protecting group on Lys, peptide-EBXs 3v and 3q were accessed in 34% over 10 steps and 11% over 22 steps, respectively.