Step 3: To a solution of hydroxylamine hydrochloride (3.06 g, 44.1 mmol) in ethanol (20 mL) was sequentially added a mixed water-ethanol (1:1, 40 mL) solution of potassium hydroxide (1.26 g, 22.5 mmol) and a solution of compound 63 (2.3 g, 9 mmol). The reaction mixture was heated to reflux overnight. Upon completion of the reaction, the solvent was removed by concentration under reduced pressure. The resulting residue was purified by silica gel column chromatography (eluent: ethyl acetate/petroleum ether=1:5) to afford compound 64 (1.45 g, 75% yield) as a white solid. lC-MS (Method D): tR=0.58 min, [M+H]+=175.99, 178.01. 1H-NMR (300 MHz, DMSO-d6): δ 3.44 (d, J=93.5 Hz, 3H), 4.77 (s, 2H), 5.53 (s, 1H).
