Scheme 2.

Synthesis of PG1-FM. Reagents and conditions are the following: (A) hexamethylenetetramine, TFA, 90 °C, 16 h; (B) H₂O, 95 °C, 1 h; (C) N-phenyl-bis(trifluoromethanesulfonimide), Cs₂CO₃, MeCN, room temperature (r.t.), 1 h; (D) NaBH(OAc)₃, AcOH, THF/MeOH, 1 h; (E) DAST, CH₂Cl₂, −20 °C to r.t., 1 h; and (F) Bis(pinacolato)diboron, Pd(dppf)Cl₂, KOAc, Dioxane, 80 °C, 3 h. PF2 is used throughout this study as a control compound which is responsive toward H₂O₂ but does not undergo biomolecule labeling.