Synthetic scheme for synthesis of bivalent ligands and control ligands. (A) The synthesis of N-terminal linker controls and bivalent ligands by microwave synthesis. (B) Synthesis of C-terminal linker controls using a semi-automated synthesizer. (a) 20 % piperidine in DMF (b) Fmoc-NH-AA-COOH or Fmoc-NH-PEDG20-COOH, HBTU, DIEA in DMF. Repeat (a) and (b) to achieve desired sequence. When Fmoc-NH-PEDG20-COOH was incorporated, reaction was allowed to proceed for an extra hour at room temperature. (c) 75% acetic anhydride/ 25% pyridine. (d) Cleavage with 91% TFA, 3% EDT, 3% TIS, 3% water for 1.5-3 hours.