Chloro[[(1,1-dimethylethoxy)carbonyl]amino]-sulfane dioxide was prepared by adding chlorosulfonyl isocyanate (32 mg, 0.23 mmol, 1.0 eq.) to a cooled solution of tert-butyl alcohol (17 mg, 0.23 mmol, 1.0eq.) and dichloromethane (2 mL) in an ice-water bath. The resulting mixture was stirred at 0-5° C. for 2-3 hr. The solution was then treated with a solution of N-(3-((4-((3-aminopropyl)amino)-5-bromo-2-pyrimidinyl)amino)phenyl)-1-pyrrolidinecarboxamide (100 mg, 0.20 mmol, 1eq.) and dichloromethane (5 mL). DMAP (20 mg, 0.16 mmol) was then added followed by the dropwise addition of DIEA (0.1 mL, 0.57 mmol). The mixture was stirred at RT for overnight. The reaction mixture was concentrated in vacuo. The residue was dissolved in TFA (2 mL), and purified by HPLC using acetonitrile/water to afford the title compound (30 mg).
