2 + 1 Dithiocarbamate (DTC)-isocyanide (ISO) system was studied to label amino acids and model peptides with Tc-99m(CO)(3)(+) fragment. Two ways were used: (i) conjugation via free carboxy group of bifunctional DTC [S2CNMe2- (L3), S2CNHCH2COO2- (L1) and S2C(C4H7N)COO2- (L2)] using pre-labeling procedure and (ii) conjugation via isocyanide ligand [tert-BuNC (L4), EtOC(O)CH2NHC(O)CH2NC (L5), and gly-gly-gly-CH2NHC(O)CH2NC (L6)]. Complexes M(CO)(3)L2L4(-) (1a, 1b), M(CO)(3)L3L4- (2a, 2b) and bioconjugates M(CO)(3)L1L5 (5a, 5b), and M(CO)(3)L1L6 (6b) (a, M = Re; b, Tc-99m) were synthesized. Bioconjugates 4a and 4b were prepared by reaction of histidine methyl ester with 2a and 2b, respectively. All rhenium complexes were characterized by H-1 and C-13 NMR, IR, and MS spectroscopy and complexes with 99mTc, by HPLC using rhenium analogs as references. (C) 2004 Elsevier B.V. All rights reserved.