N-(2-methylbenzyl)-4,5-dihydro-1H-imidazol-2-amine (7) (795 mg, 4.2 mmol) and 1-benzyl-3-methoxycarbonyl-piperidin-4-one hydrochloride (8) (568 mg, 2.0 mmol) were used as raw materials and reacted in a methanolic solution of sodium methanolate (0.5 M, 3.0 mL, 1.5 mmol). The reaction mixture was stirred under mild reflux conditions for 18 hours. Upon completion of the reaction, it was cooled to room temperature, diluted with dichloromethane (50 mL) and subsequently washed with brine (20 mL), dried over anhydrous sodium sulfate, filtered and concentrated in vacuum. Purification by silica gel column chromatography (eluent ratio 19:1 dichloromethane/methanol) afforded the target product 7-benzyl-4-(2-methylbenzyl)-1,2,6,7,8,9-hexahydroimidazo[1,2-a]pyrido[3,4-e]pyrimidin-5(4H)-one (2) (753 mg, 97% yield) as a light yellow solid. Melting point: 132-135°C (methanol). Thin layer chromatography Rf value: 0.25 (silica gel, 19:1 dichloromethane/methanol). IR spectrum (pure) vmax: 2750, 2358, 1646, 1616, 1487, 1296, 738 cm-1. 1H NMR (500 MHz, CDCl3) δ: 7.33 (m, 5H), 7.11 (m, 4H), 5.05 (s, 2H), 3.89 (m, 4H), 3.67 (s, 2H). 3.32 (s, 2H), 2.68 (m, 2H), 2.51 (m, 2H), 2.40 (s, 3H).13C NMR (150 MHz, CDCl3) δ: 161.6, 153.4, 145.8, 137.7, 135.7, 134.4, 130.4, 129.3, 128.6, 127.5, 127.0, 126.0, 125.4, 102.1, 62.5, 50.7, 49.7, 48.3, 47.1, 43.3, 27.0, 19.4. Calculated value by high-resolution mass spectrometry (ESI-TOF): C24H26N4OH + [M + H]+ 387.2179, measured value: 387.2166.