| Abstract: | The 2-(p-diphenyl)-isopropyloxycarbonyl (Dpoc) residue has been chosen for the selective protection of α-amino groups in the synthesis of peptides containing additional acid-labile protecting residues. It is easily introduced into amino-acids by reacting either the mixed carbonate I or the azide III with esters or salts of amino-acids. It is split by dilute acetic acid and other weakly acidic reagents at rates which permit a selective cleavage in the presence of other acid-labile protecting groups, especially those derived from t-butanol A number of peptide syntheses have been carried out with the new group either in the conventional manner or by the solid-phase method. No effects due to steric hindrance, as observed previously with the N-trityl residue, are encountered. The application of the Nα-Dpoc group to solid-phase peptide synthesis permits the use of a new combination of protecting groups in which the side chains of trifunctional amino-acids are blocked by acid-labile residues that can be easily split in the final step of the synthesis. |
