3-Amino-5-tert-butyl-2-(p-tolyl)-2H-pyrazole hydrochloride (59 mg, 0.22 mmol, 1 equiv.) was dissolved in 12 mL methylene chloride and 12 mL saturated aqueous NaHCO3 was added. The biphasic mixture was stirred until all solids had completely dissolved and cooled to 0° C. The organic layer was then treated with phosgene in one portion via syringe while not stirring (0.40 mL of a 20% solution toluene, 0.78 mmol, 3.5 equiv.). The resulting mixture was stirred vigorously at 0° C. for 0.5 h. The organic layer was separated, dried (Na2SO4) and filtered. The methylene chloride was removed in vacuo and the resulting isocyanate in toluene was treated with a solution of the above tetrahydrofuranylmethylaminopyrimidine ether intermediate (75 mg, 0.22 mmol, 1.0 equiv.) in 4 mL anhydrous THF. The mixture was stirred at room temperature for 36 h, then the solvent was removed in vacuo. The product urea was purified by column chromatography on silica gel using 0–10% MeOH in methylene chloride eluent mixtures, affording 112 mg of the title compound [(S)-enantiomer] as a light pink foam. Further purification by preparatory reverse-phase HPLC afforded 44 mg of the title compound as a pure, yellow foam.
