Scheme 6. General synthesis of (±)-maackiain. Reagents and conditions: (a) acrylonitrile, triton B, NaOH, 100 °C, 10 h; (b) H2SO4, CH3COOH, H2O, 100 °C, 8 h; (c) benzyl chloride, NaI, K2CO3, acetone, 60 °C, 18 h; (d) NaBH4, ethanol, rt, 3 h; (e) p-toluenesulfonic acid, toluene, 110 °C, 2 h; (f) PCl2(PhCN)2, KoAc, DMF, 40 °C, 4 days; (f) H2–Pd/C, 3 h.
