2,3,4,5-Tetrahydro-1,2,3,8-tetramethyl-1H-pyrido[4,3-b]indole (550 mg, 2 mmol) was dissolved in DMF. Copper (I) iodide L-proline (46 mg, 0.4 mmol) and potassium phosphate (848 mg, 4 mmol) were added and the reaction mixture was stirred for 10 min. at RT. 4-(1-bromo-3,3-dimethylbut-1-en-2-yl)pyridine (294 mg, 3.0 mmol) was added dropwise and the reaction mixture was purged with nitrogen. The reaction mixture was heated overnight at 85° C. (prolonged heating in some cases was required). DMF was evaporated under reduced pressure, the residue was diluted with water and the solid was filtered. The solid material was purified by silica gel chromatography (100-200 mesh). The product was further purified by HPLC. The free base was converted into oxalate salt by treatment of oxalic acid (1 equiv) in THF. Yield: 8 mg as the oxalate salt. 1H NMR (CD3OD, freebase) δ (ppm): 8.60 (d, 2H), 7.70 (d, 2H), 7.35 (s, 1H), 7.30 (s, 1H), 7.10 (m, 2H), 4.50 (m, 1H), 4.0 (m, 1H), 3.10 (m, 1H), 2.90 (s, 3H), 2.80 (m, 1H), 2.42 (s, 3H), 2.0 (s, 3H), 1.76 (d, 3H), 1.50 (d, 3H).
