"2 + 1" Dithiocarbamate (DTC)-isocyanide (ISO) system was studied to label amino acids and model peptides with 99mTc(CO)3+ fragment. Two ways were used: (i) conjugation via free carboxy group of bifunctional DTC [S2CNMe2- (L3), S₂CNHCH₂COO^2- (L1) and S ₂C(C₄H₇N)COO^2- (L2)] using pre-labeling procedure and (ii) conjugation via isocyanide ligand [tert-BuNC (L4), EtOC(O)CH₂NHC(O)CH₂NC (L5), and gly-gly-gly-CH ₂NHC(O)CH₂NC (L6)]. Complexes M(CO)₃L2L4 ^- (1a, 1b), M(CO)₃L3L4^- (2a, 2b) and bioconjugates M(CO)₃L1L5 (5a, 5b), and M(CO)₃L1L6 (6b) (a, M = Re; b, ^99mTc) 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 ¹H and ¹³C NMR, IR, and MS spectroscopy and complexes with ^99mTc, by HPLC using rhenium analogs as references.