Syntheses of Peptides Related to the N-Terminal Structure of Corticotropin. III. The Synthesis of l-Histidyl-l-phenylalanyl-l-arginyl-l-tryptophan, the Smallest Peptide Exhibiting the Melanocyte-stimulating and the Lipolytic Activities

Abstract 1) A tetrapeptide, l-histidyl-l-phenylalanyl-l-arginyl-l-tryptophan, corresponding to the amino-acid sequence of positions 6 to 9 in the corticotropin and α-MSH molecules has been synthesized. 2) This synthetic tetrapeptide has been found to exhibit an MSH potency of 3.6×104 units per gram in the in vitro frog skin assay, and it is also active on lipolysis in rabbit perirenal adipose tissue. These results may confirm that the glycine at position 10 in the molecules of corticotropin and α-MSH is not essential for these biological activities. 3) It has been shown that the azide-couling procedure can be employed successfully for the synthesis of arginyl peptides provided it is used in combination with the NG-tosyl-arginine. 4) The preparation of NG-tosyl-l-arginine and some of the relevant compounds has been described.