Solid-phase synthesis of porcine cholecystokinin-33 in a new resin via FMOC-strategy.

Porcine cholecystokinin-33 has been synthesized on solid phase and characterized both chemically and biologically. In order to develop a successful synthetic strategy, a new anchor molecule (4-succinylamido-2,2',4'-trimethoxybenzhydrylamine) was designed and coupled to aminomethyl-polystyrene. The resulting 4-succinylamido-2,2',4'-trimethoxybenzhydrylamine resin was successfully used for the synthesis of cholecystokinin-33 using N-fluorenylmethoxycarbonyl amino acid symmetric anhydrides. Tyrosine-O-sulfate has been synthesized by direct sulfation of tyrosine with chlorosulfonic acid and incorporated into the peptide sequence by coupling as N-fluorenylmethoxy-O-sulfatotyrosine-pentafluorophenyl ester. Side chains of the trifunctional amino acids were protected mostly by t-butyl-type protecting groups. The guanidino function of arginine was protected by the 2,2,5,7,8-pentamethylchromane-6-sulfonyl group. After completion of the synthesis, the peptide was cleaved off the support with 50% trifluoroacetic acid (15 min); this treatment cleaved the side-chain protecting groups simultaneously. Preparative high-performance liquid chromatography resulted in pure cholecystokinin-33 of full biological activity. The structure of the peptide was proved by amino acid analysis, IR and UR spectroscopy, fast atomic bombardment mass spectroscopy and comparative high-performance liquid chromatography of the synthetic and native cholecystokinin-33.