Synthetic route for resin-bound polyglutamates. Reagents and conditions: (a) i: 20% piperidine in DMF, rt, 60 min, ii: Fmoc-Glu-OtBu, HATU, HOBt, DIPEA, DMF, (b) HATU, HOBt, DIPEA, DMF, 7a (for 10a), 7b (for 10b), or 7c (for 10c), (c) i: 4-iodobenzyl chloride, CH3CN, ii: TFA/CH2Cl2, (d) 20% piperidine in DMF, rt, 60 min, ii: Fmoc-Glu(OtBu)-OH, HATU, HOBt, DIPEA, DMF.