Abstract Modified amino acids which can serve as precursors in the synthesis of tritium- labelled peptides were prepared and incorporated into biologically active peptides. Thus, p- iodophenylalanine was incorporated at position 4 of H-Met (O 2)-Glu-His-Phe-D-Lys-Phe- OH (Org 2766) and in des-Tyr 1-γ-endorphin. As a second labelling site, the precursor of L- leucine, L-methallylglycine, was incorporated in both des-Tyr 1-γ-endorphin and the ...
