[Studies on the total synthesis of cholecystokinin-pancreozymin. Synthesis of the suitably protected fragment corresponding to the sequence 24--33 (author's transl)].

The synthesis is described of a suitably protected decapeptide derivative corresponding to the C-terminal tyrosin-O-sulfate-containing sequence 24--33 of cholecystokinin-pancreozymin as key fragment for the total synthesis of this gastrointestinal hormone or its 39-variant. This peptide derivative has been prepared according to our newly developed procedure based on the direct use of N-acyltyrosine-O-sulfate barium salt. Additionally, removal of the protecting groups followed by purification via chromatographic methods produced the decapeptide amide in good yields and with a high degree of purity as a fully active cholecystokinin-pancreozymin related peptide.