A solution of sodium methoxide in methanol is added at room temperature, until a pink color persists, to 10.3 mg. (0.12 mmol) of o-methylhydroxylamine hydrochloride in dry MeOH containing a few crystals of phenolphthalein and 3 A molecular sieves. Methyl 2-(3-tritylamino-5-isoxazolyl)-2-ketoacetate (17.8 mg., 0.04 mmol) is then added and the reaction stirred at 65° C. for 5 hours. The sieves are removed by filtration and the filtrate concentrated to dryness under reduced pressure. After chromatography on silica gel (60-200 mesh) using 5:2 hexane:EtOAc as an eluent the title compound is isolated as a mixture of syn- and anti-methyloximes (13.7 mg., 72%).
