A Rapid, Efficient Synthesis of Oxytocin and 8-Arginine-vasopressin. Comparison of Benzyl, p-Methoxybenzyl, and p-Methylbenzyl as Protecting Groups for Cysteine

Oxytocin and 8-arginine-vasopressin have been synthesized in high yields in a short time using 1.5-fold molar excesses of protected amino acids by means of solid-phase synthesis on a benzhydrylamine resin. Coupling of each residue to the peptide resin was measured by automated picrate monitoring. High-pressure liquid partition chromatography was found to be extremely useful in characterizing products and by-products. Benzyl, p-methoxybenzyl, and p-methylbenzyl were compared as cysteine protecting groups in the syntheses, with the last two being preferred.