1-(2,3-Dihydroxypropyl)-7-methoxyquinoxalin-2(1H)-one (3.06 g, 12.22 mmol) was dissolved in dichloromethane (75 ml). To the solution, tert-butyldimethylsilyl chloride (2.03 g, 13.44 mmol), triethylamine (2.21 ml, 15.89 mmol) and 4-dimethylamino pyridine (299 mg, 2.44 mmol) were added under cooling on ice, and the reaction mixture was stirred for 12 hours while the temperature was rising to room temperature. The reaction solution was diluted with dichloromethane, washed with water and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography (chloroform/methanol) to yield 5.29 g (quantitative) of the title compound in the form of a dark orange oily product.
