(A) Synthetic scheme of DUPA. Reagents and conditions: (a) triphosgene, TEA/DCM, −78 °C; (b) H-L-Glu(OBn)-OtBu·HCl; (c) H2; Pd-C/DCM. (B) Synthetic scheme of cholesterol-PLGVRK-PEG2000. Reagents and conditions: (d) DCM, 0–5°C; (e) TFA (95%) water (2.5%), Tips (2.5%); (f) DIPEA (0.2 mmol) in anhydrous DCM. (C) Synthetic scheme of cholesterol-PLGVRK-PEG3000 Block-2: (g) EDC, DCM, (h) 95% TFA in DCM for 2 h at room temperature. (D) 1H NMR spectrum of cholesterol-PLGVRK-PEG2000. (E) 1H NMR spectra of cholesterol-PEG3000-DUPA.