Comparison of the applicability of 2-hydroxyethylsulfonylmethyl- and chloromethyl-polystyrenes in the solid-phase synthesis of protected peptides

In order to compare the applicability of resins in the preparation of protected peptides two solid-phase syntheses of a protected ACTH-(5–10)-hexapeptide have been performed, one using 2-hydroxyethylsulfonylmethyl-polystyrene and the other with Merrifield's chloromethylated polystyrene. To obtain a good comparison, equivalent methods were used as far as possible. Optimal conditions for deprotection of amino groups and for the liberation of the end-product were determined. Chromatographic examination of the crude fission products of the peptidyl resins presented important clues towards the nature of the underlying fission mechanism. Using an automated peptide synthesizer the pure end-product was obtained from both resins in approximately the same yield (ca. 70%). It appeared that the isolation of the product from the suffone resin is less laborious, since the critical alkali-treatment, necessary for the liberation of the product, proceeds faster and, if properly carried out, avoids transesterification.