Scheme 1. Synthesis of the FITC-PEG20-Fc-III reactive conjugate: (a) HATU, DIEA, DMF, and then Fc-III peptide; (b) 20% piperidine, DMF; (c) compound 4, Et3N in ACN at 40 °C; (d) compound 6, DMAP in DCM at 25 °C; (e) TFA/DCM (1/3); (f) FITC, DIEA in ACN/DMF 1/1 at 25 °C; (g) HATU, DIEA, DMF, and NH2-PEG20-Fc-III peptide.
