Synthesis and properties of human β-endorphin-(1-9) and its analogs

Abstract

Four analogs of human .beta.-endorphin (.beta.h-EP) were synthesized by the solid-phase method: .beta.h-EP-(1-9) (I), [D-Ala2]-.beta.h-EP-(1-9) (II), [Gln8]-.beta.h-EP-(1-9) (III), and [D-Ala2, Gln8]-.beta.h-EP-(1-9) (IV). Measurement in a radioreceptor binding assay with use of tritiated .beta.h-EP as primary ligand gave relative potencies as follows: Met-enkephalin, 100; I, 76; II, 100; III, 200; IV, 200. Two new amino acid derivatives were prepared and used for synthesis of the analogs: N.alpha.-t-butyloxycarbonyl-O-(cyclopentyl)-tyrosine and N.alpha.-t-butyloxycarbonyl-.gamma.-(cyclopentyl)-glutamic acid.