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The compound from 31b above (5.0 g, 15.8 mmol) and tin chloride (25 g, 111 mmol) were suspended in concentrated HCl and ethanol (150 mL), and the mixture was heated at reflux for 1 hour. The mixture was cooled to 0° C., then filtered. The filtrate was neutralized with sodium bicarbonate (180 g) and extracted with ethyl acetate. The organic extracts were washed with brine, dried (MgSO4) and concentrated. The residue was chromatographed (silica gel; chloroform/methanol/NH4OH, 95:5:0.5-90:10:1) to afford the title compound (3.3 g, 34% yield): MS (CI/NH3) m/z 189, 191 (M+H)+ ; 1H NMR (DMSO-d6, 300 MHz) δ 7.57 (d, J=2.6 Hz, 1H), 7.43 (d, J=2.6 Hz, 1H).

1. temperatureat reflux for 1 hour
2. filtrationfiltered
3. extractionextracted with ethyl acetate
4. washThe organic extracts were washed with brine
5. dry with materialdried (MgSO4)
6. concentrationconcentrated
7. customThe residue was chromatographed (silica gel; chloroform/methanol/NH4OH, 95:5:0.5-90:10:1)