A solution of tert-butyl 9-(6-(4-aminophenyl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl)-3-oxa-7,9-diazabicyclo[3.3.1]nonane-7-carboxylate (230 mg, 0.45 mmol) in dichloromethane (6 mL) was treated triethylamine (520 μL), followed by triphosgene (90 mg, 0.30 mmol) as a solution in dichloromethane (2 mL). After the passage of 5 minutes, the appropriate nucleophile—in the case, 2.0 M methylamine solution in tetrahydrofuran (4 mL)—was added to tert-butyl 9-(6-(4-isocyanatophenyl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl)-3-oxa-7,9-diazabicyclo[3.3.1]nonane-7-carboxylate (“isocyanate”) mixture. The reaction mixture was concentrated to dryness under reduced pressure. The residue was purified by reverse-phase high performance liquid chromatography using a Phenomenex Prodigy 21 mm×250 mm column, running a gradient elution of 10% acetonitrile/90% of 0.1% aqueous trifluoroacetic acid to 100% acetonitrile to provide tert-butyl 9-(6-(4-(3-methylureido)phenyl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl)-3-oxa-7,9-diazabicyclo[3.3.1]nonane-7-carboxylate. MS (ES+): 577.2 (M+H)+
