8-Chloro-2,3,4,5-tetrahydro-2-methyl-1H-pyrido[4,3-b]indole (220 mg, 1 mmol) was dissolved in DMF (3 mL). Potassium phosphate (424 mg, 2 mmol), copper (I) iodide (19 mg, 0.1 mmol) and L-proline (23 mg, 0.2 mmol) were added. A solution of 4-(1-bromo-3,3-dimethylbut-1-en-2-yl)pyridine (294 mg, 1.5 mmol) in DMF (2 mL) was added dropwise, the reaction mixture was purged with nitrogen, and heated at 85° C. overnight. The DMF was evaporated under reduced pressure and the reaction mixture was diluted with water. The resultant precipitate was filtered and purified by silica gel chromatography (100-200 mesh) using 0-8% MeOH:DCM as eluant. The compound was further purified by HPLC. Yield: 77.03 mg. 1H NMR (CD3OD, TFA salt) δ (ppm): 8.30 (d, 2H), 7.30 (m, 4H), 7.18 (d, 1H), 6.90 (s, 1H), 4.50 (m, 1H), 4.20 (m, 1H), 3.80 (m, 1H), 3.50 (m, 1H), 3.15 (m, 2H), 3.05 (s, 3H), 1.35 (s, 9H).
