3-Phenyl-6-(3-phenylpropyloxy)-1-oxo-1H-indene-2-carboxylate ethyl ester (2 g, 4.85 mmol) and hydroxyamine.hydrochloric acid (1.01 g, 14.6 mmol) were dissolved in pyridine (1.57 ml, 19.4 mmol). The reaction mixture was stirred for 1 hour at 70° C., and washed with saturated ammonium chloride. The organic layer obtained by extracting the reaction mixture with ethyl acetate was dried over anhydrous magnesium sulfate, concentrated, and the residue was purified by silica gel column chromatography (ethyl acetate:hexane=1:2) to obtain 1-hydroxyimino-3-phenyl-6-(3-phenylpropyloxy)-1H-indene-2-carboxylate ethyl ester (yield 9.5%) as a yellow solid.
