Synthesis of human [15-norleucine]little-gastrin-II and des-1-tryptophan-[12-norleucine]minigastrin-II

Abstract

By the use of a newly developed procedure for the synthesis of tyrosine-O-sulfate peptides based on the direct incorporation of the suitably N alpha-protected tyrosine-O-sulfate residue along the synthetic route, the synthesis of two human gastrin-II analogues was successfully accomplished. Thereby acid labile side chain protection was applied in combination with the N alpha-benzyloxycarbonyl group in the intermediate chain elongation steps. Despite the pronounced acid-lability of the sulfate ester moiety, its hydrolysis during the final acidolytic deprotection step was significantly reduced under optimized conditions. Subsequent chromatographic purification led to the two gastrin analogues in satisfactory yields as highly pure compounds as judged by various indicative analytical assays.