Two SPPS strategies are now considered standard procedures, the Boc/Bzl and the Fmoc/tBu protection scheme. Fmoc/tBu- and Boc/Bzl-SPPS differ in the choice of the temporary Nα (Boc or Fmoc) and permanent (side-chain: tBu-related or Bzl-related) protecting groups. The type of Nα-blocking group determines the options for side-chain protection and the conditions of final cleavage (removal of the permanent protective groups and splitting from the carrier). Fmoc-SPPS is considered the milder method.