The Trifluoroacetate Method of Peptide Synthesis. II. An Improved Synthesis of Bradykinin

When p-nitrophenyl trifluoroacetate (I), 2, 4, 5-trichlorophenyl trifluoroacetate (II) and N-hydroxysuccinimide trifluoroacetate (III) were subjected to Anderson’s racemization test, only reagent III showed resistance against racemization. However, reagents I and II were also found to be useful for fragment-condensation with acylpeptides possessing glycine or proline at the C-terminus. Bradykinin was prepared using these reagents. During the synthesis, a combination of the t-amyloxycarbonyl N-protecting group and the benzyl ester was mainly used, and the alkaline hydrolysis procedure of the ester group was eliminated. Thus, colorless bradykinin with full activity was obtained in a satisfactory yield without any purification procedure.