Studies on Peptides. CXXXII. Evaluation of Two /1-Carboxyl Protecting Groups of Aspartic Acid, Cycloheptyl and Cyclooctyl, for Peptide Synthesis

Abstract

The properties of two aspartic acid β-esters (Asp(OR), R = cycloheptyl (Chp) and cyclooctyl (Coc)) were examined. These two protecting groups were found to be stable to trifluoroacetic acid (0°C, 2h), but were cleaved by HF or 1 M Trifluoromethanesulfonic acid-thioanisole in trifluoro-acetic acid (0°C, 60 min). Using a model peptide, Z(OMe)-Ala-Asp(OR)-Gly-OBzl, the behavior of the Asp(OR) residue with base or acid was examined. These esters were less susceptible to succinimide formation than the Bzl group in Et3N treatment. In acid deprotection, succinimide formation from these peptides was less than 7% in both cases. © 1986, The Pharmaceutical Society of Japan. All rights reserved.