Step 2. Compound 8-C (4.5 g, 18.1 mmol) and iron powder (1.52 g, 27.2 mmol) were suspended in a solvent mixture of ethanol/water (50 mL/100 mL), followed by addition of ammonium chloride (3.9 g, 72.6 mmol). The reaction mixture was stirred at 50 °C for 3 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) (unfolding agent: petroleum ether/ethyl acetate = 1:1, Rf = 0.3) to confirm the completion of the reaction. After completion of the reaction, the mixture was filtered through diatomaceous earth and the filter cake was washed with ethanol. The filtrates were combined and concentrated to afford the crude product 8-D. The crude product was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=10:1 to 2:3 gradient elution) to afford the pure product 8-D (3.0 g, 76% yield) as a black oil.1H NMR (400 MHz, DMSO-d6) δ: 4.79 (s, 2H), 6.54-6.51 (d , J=8.8Hz, 2H), 6.71-6.73 (d, J=8.8Hz, 2H), 6.78-6.80 (d, J=8.4Hz, 2H), 7.60 (s, 1H).
