The choice of Nα- and side-chain protection depends on the sequence of the peptide and the synthetic strategy, which is far more complex than in SPPS. In most cases, Z or Boc are chosen as Nα-protecting groups. Z cannot be cleaved by catalytic hydrogenolysis (the standard method for removing this protecting group) in the presence of sulfur-containing amino acids. Blocking the side-chains of Cys and Lys is mandatory. Choice and extent of additional lateral protection depend on the synthetic strategy.