To a solution of 2-methyl-2-(5-pyridin-2-ylthiophene-2-sulfonylamino)-propionic acid (1.60 grams, 4.91 mmole) in methylene chloride (160 mL) was added triethylamine (2.3 mL, 16.5 mmole), (benzotriazol-1-yloxy)tris(dimethylamino)-phosphonium hexafluorophosphate (2.4 grams, 5.41 mmole) and O-(2-trimethylsilylethyl)hydroxylamine hydrochloride (0.92 grams, 5.41 mmole). The resulting mixture was stirred at room temperature for 16 hours. The solvent was evaporated and the residue was taken up in ethyl acetate. The solution was washed with water, aqueous saturated sodium bicarbonate solution, and brine. After drying over magnesium sulfate, the solvent was evaporated to afford a white foam from which the desired product, 2-methyl-2-(5-pyridin-2-ylthiophene-2-sulfonylamino)-N-(2-trimethylsilanylethoxy)-propionamide (220 mg, 10%), a white solid, was isolated by chromatography on silica gel eluting with 3:2 ethyl acetate/hexanes.
