Synthesis of the luteinizing hormone‐releasing hormone (LHRH) by the repetitive excess mixed anhydride (REMA) method

Abstract

AbstractUsing ethyl glycinate (I) as starting material, after Nα‐benzyloxycarbonyl‐nitroarginylproline [ZArg(NO2)‐Pro, II]* had been coupled to it with the aid of excess mixed anhydride, and after acidolysis, the tripeptide Arg(NO2)‐Pro‐Gly‐OEt was obtained. By means of the repetitive excess mixed anhydride (REMA) method the protected decapeptide sequence (X) of the luteinizing hormone‐releasing hormone (LHRH) was synthesized (Scheme). In the course of this process, at the heptapeptide stage, the C‐terminal ethyl ester (VIIa) was converted by ammonolysis into the amide (VIIb).Acidolysis of X, with liquid hydrogen fluoride, gave crude LHRH (XI). Purification afforded LHRH, which was chemically identical with the luteinizing hormone‐releasing hormone synthesized elsewhere by another method, and which was found to be highly active biologically.