The 2-adamantyloxycarbonyl group was employed for the protection of the ε-amino group of Lys and the hydroxyl group of Tyr, and the 2-adamantyl ester was employed for the protection of the β-carboxyl group of Asp in order to construct eight peptide segments as building blocks for the preparation of peptide fragments related to the sequence of Sulfolobus solifataricus Ribonuclease. The usefulness of the above protecting groups developed in our laboratory was confirmed.