Scheme 1. Synthesis of bis-diBrPD 1. Reagents and conditions: (i) TFA, CH₂Cl₂, 21 °C, 1 h; dibromomaleic anhydride, AcOH, reflux, 2 h; (ii) tert-butyl (3-(2-(2-(3-aminopropoxy)ethoxy)ethoxy)propyl)carbamate, CDI, DMF, 21 °C, 12 h; (iii) TFA/DCM, 21 °C, 30 min; (iv) HATU, DIPEA, DMF, acid-alkyne PD 6 21 °C, 16 h.