dioxide, to give N-t-BOC-2-Amino-[7-14C]benzoic acid (3). Product 3 was then deprotected with trifluoroacetic acid to give 2-Amino-[7-14C]benzoic acid as its TFA salt (4). The latter was diazotized and treated with Na2S2, generated in situ, to give 2,2′-dithiobis[7-14C]benzoic acid (5). The acidchloridefrom 5, obtained by treatment with thionylchloride, was subsequently coupled with L-isoleucine tert-butyl