Chemical Studies on Amino Acids and Peptides. II. Syntheses of Choline Esters of Peptides related to Tetragastrin

Abstract

Choline esters of peptides related to tetragastrin, Z-Asp (OBu^t)-Phe-OCh⁺ Br^-(XII), Z-Met-Asp (OBu^t)-Phe-OCh⁺ Br^-(XIII), Z-Trp-Met-Asp(OBu^t)-Phe-OCh⁺ Br^-(XIV), and BOC-Trp-Met-Asp (OBu^t)-Phe-OCh⁺ Br^- (XV) were synthesized by the condensation of N-protected peptides, (VI), (VII), (VIII), and (IX), with β-dimethylaminoethyl bromide followed by methylation with methyl bromide. Selective removal of the protective groups from the above peptide choline esters was achieved by conventional acid treatment under mild conditions.