Scheme 1. Synthesis of PBR316 and its tosyl precursor 5. a) Br₂, AlCl₃, ethyl acetate. b) 2-Amino-5-chloropyridine, NaHCO₃, EtOH. c) COCl₂, DIPEA, CH₂Cl₂, NH(Me₃)₂, pyridine. d) K₂CO₃, MeOH. e) TsCl, TMHDA, or TsCl, K₂CO₃, dry grind method. f) PFBSF, NEt₃·3HF, DIPEA, CH₃CN.