Synthesis and opiate activity of human beta-endorphin analogs with various chain lengths

The synthesis of beta h-endorphin -(1--15), -(1--21), -(1--26), -(1--28) and -(1--29) have been accomplished by the solid-phase method. The opiate activities of the peptides were measured in the guinea pig ileum assay. Their relative potencies were beta h-endorphin (beta h-EP), 1.00; Met-enkephalin, 0.25: beta h-EP-(1--15), 0.17; beta H-EP-(1--21), 0.46; beta H-EP-(1-26), 0.48; beta h-EP-(1--28), 0.89; beta h-EP-(1--29), 1.04.