Amino acids and peptides. Part 45. Development of a new Nπ-protecting group of histidine, Nπ-(1-adamantyloxymethyl)histidine, and its evaluation for peptide synthesis

Abstract

N ^π -(1-Adamantyloxymethyl)histidine, His(N^π-1-Adom), is prepared and its properties are examined. The 1-Adom group can be easily removed by trifluoroacetic acid and it is stable to 20% piperidine–dimethylformamide and 1 mol dm^–3 NaOH. His(N^π-1-Adom) derivatives can suppress racemization during coupling reactions. His(N^π-1-Adom) can be used in solid-phase peptide synthesis in combination with fluoren-9-ylmethoxycarbonyl as an N^α-protecting group. Thyrotropin-releasing hormone is successfully synthesized by using His(N^π-1-Adom).