Amino acids and peptides. XXV. Application of newly developed beta-1- and beta-2-adamantylaspartates to peptide...

Newly developed beta-1- and beta-2-adamantylaspartates [H-Asp(O-1-Ada)-OH and H-Asp(O-2-Ada)-OH] were applied to the synthesis of a C-terminal octapeptide of the beta-subunit of human chorionic gonadotropin (hCG) by a conventional solution method and a hexacosapeptide of the alpha-subunit of insulin receptor (30-55) by a solid-phase method with the objective of suppressing aspartimide formation during the synthesis of aspartylpeptides. The 1-Ada and 2-Ada groups were confirmed to be useful protecting groups for the beta-carboxyl function of the Asp residue.