A suspension of 430 mg of 4-[5-(2-fluoro-phenoxy)-oxazolo[5,4-d]pyrimidin-2-yl]-2,6-dimethyl-phenol, 0.2 ml of tert-butyl bromoacetate and 423 of mg potassium carbonate in 5 ml of dimethylformamide was stirred at 60° C. for 2 h. After cooling, the solids were removed by filtration and the solvent were distilled off in vacuo. 1.3 ml of trifluoroacetic acid were added to the residue, and the solution was stirred at room temperature for 1 h. Then 10 ml of toluene were added and the solvents were removed in vacuo. The title compound was isolated by silica gel chromatography (heptane/ethyl acetate gradient) as a white solid (135 mg).
