Solid-phase synthesis of thymosin alpha 1 using tert-butyloxycarbonylaminoacyl-4-(oxymethyl)phenylacetamidomethyl-resin.

Thymosin alpha 1 and its desacetyl analogue were synthesized by the solid-phase method. Use of aminoacyl-4-(oxymethyl)phenylacetamidomethyl-resin resulted in an improved yield and allowed the synthetic products to be purified by simple ion-exchange and gel filtration chromatography. Success of the synthesis was largely due to enhanced stability of the peptide-resin linkage to trifluoroacetic acid and to the elimination of hydroxy functions on the resin. This improved quality of the solid support helps eliminate chain loss and chain termination during the synthesis. The purified synthetic peptides were found to be homogeneous by paper electrophoresis, isoelectric focusing in polyacrylamide gel, and thin-layer chromatography. They also had biological activity in the azathioprine-sensitive rosette assay. Use of the new 9-(2-sulfo)fluorenylmethyloxycarbonyl chloride reagent for purification of protected peptides was also demonstrated and discussed.