Selektiv S‐geschützte Cysteinpeptide, III. Synthese eines [Ala¹²]‐Schafinsulin‐A‐Kettenoktapeptides A6–13 mit 6–11‐Disulfidring

Abstract

Selectively S‐Protected Cysteine Peptides. III. Synthesis of a [Ala12]‐Sheep Insulin A‐Chain Octapeptides with 6–11‐Disulfide Ring Studying the problems of the selective sulphur protection in cysteine peptides, a octapeptide A6–13 with 6–11‐disulphide ring from the [Ala12]‐sheep insulin A‐chain was prepared by conventional synthesis using the S‐Acm and S‐Dpm group. The synthesis of the octapeptide Boc‐Cys(Acm)‐Cys(Dpm)‐Ala‐Gly‐Val‐Cys(Acm)‐Ala‐Leu‐OH 1 was carried out with the fragments Boc‐Cys(Acm)‐Cys(Dpm)‐Ala‐Gly‐OH 4 and HCl · H‐Val‐Cys(Acm)‐Ala‐Leu‐OH 8 by means of DCCI/HOOBt coupling method. Fragments 4 and 8 were synthetisized step by step without carboxyl protecting group from the carboxyterminal end using the Boc‐amino protecting group. Treatment of 1 with iodine in methanol gives formation of the octapeptide 2 with 6–11 – disulphide ring. The Dpm‐thiol protecting group is completely stable during this step. Mass spectra of S‐Dpm and S‐Acm protected compounds are discussed.