AbstractTo exemplify the usefulness of theS‐tert‐butylthio group for a reversible blocking of the cysteine thiol function in peptide synthesis, fully protected dihydrosomatostatin was prepared by the fragment‐condensation procedure. The experimental results confirm the excellent stability of the asymmetric disulfide under the normal conditions of peptide synthesis and prove that the selective, acid‐catalyzed nucleophil removal—as well as by mercaptans—of the 2‐nitrophenylsulfenyl group proceeds smoothly in the presence of this thiol protection. Thus, the strategy of overall acid‐labile side‐chain protection in combination with theNα‐2‐nitrophenylsulfenyl group for the chain‐elongation steps can be successfully applied to the synthesis of cysteine‐containing peptides using theirS‐tert‐butylthio derivatives. Removal of the acid‐labile groups, followed by reductive cleavage of the asymmetric disulfides and successive air oxidation, allowed a clean conversion of protected dihydrosomatostatin into somatostatin at a high deg