An improved solid-phase method for peptide synthesis--the syntheses of oxytocin and vasopressin

Peptide hormones are now widely used for both medicinal and veterinary purposes. It is, therefore, imminent to improve the process of peptide synthesis to meet the needs of production. This paper describes an improved method for the solid-phase synthesis of peptides. By reacting the potassium salt, instead of the triethyl ammonium salt, of the N-protected amino acid with the chloromethylated polystyrene-divinyl benzene (2%) support, esterification was found to attain higher levels, thus obviating or minimizing the formation of a quaternary anion exchanger which might cause side reactions during the subsequent steps of synthesis. The method has been applied to the syntheses of oxytocin and vasopressin and found to be quite satisfactory. A new method was introduced for the determination of free alpha-amino groups of the peptide polymer support through the formation of a Schiff's base with salicylaldehyde.