Scheme 1. Optimizing the hydrophilic PEG fragment length for molecularly precise prodrugs. (a) Synthetic route to DCM-S-CPT, BP5-DCM-S-CPT and BP20-DCM-S-CPT. (b) 1H NMR and high resolution mass spectra (HRMS) of DCM-S-CPT, BP5-DCM-S-CPT and BP20-DCM-S-CPT. Note: the excellent reproducibility, structural homogeneity and fixed loading efficiency of BPn-DCM-S-CPT completely avoid the batch-to-batch variability of the physical encapsulation system and polymer–drug conjugates.
