Synthesis of Thymosin beta(Xen)(4) and its comparison with the natural tritetraconpeptide

Thymosin beta(4)(Xen), a 43 residue peptide recently isolated from Xenopus laevis, was synthesized by automatic solid phase procedure and compared wit h the natural product, isolated from the ovaries of Xenopus laevis. For the synthesis N-methylpyrrolidone was chosen as solvent instead of the commonl y used dimethylformamide because this solvent seems to be superior for soli d phase peptide synthesis due to the favorable swelling properties of the p olystyrene resin in this solvent and its dissolving power against the resin -bound peptide which reduces intermolecular aggregation. With acetic anhydr ide/pyridine and hydroxysuccinimide acetate two different acetylation reage nts were tested for the final acetylation step, which gave both comparable results as shown by analytical HPLC investigations. The crude synthetic pro duct was purified by HPLC, confirmed by ASA and LD-MS and was identical com pared with the natural thymosin beta(4)(Xen).