1053656-22-6

24424-99-5

77112-52-8

1053656-22-6

Method A - Step b: Preparation of 7-tert-butyl-2-ethyl-5,6-dihydroimidazo[1,2-a]pyrazine-2-dicarboxylate [0080] In 500 mL of ethanol, ethyl imidazo[1,2-a]pyrazine-2-carboxylate (1 g, 5.2 mmol), di-tert-butyl dicarbonate (Boc2O, 3.0 g, 18 mmol), and 200 mg of 10% Pd/C (50% wetted) were added. The reaction mixture was stirred at room temperature for 24 h under hydrogen atmosphere. Upon completion of the reaction, the mixture was filtered to remove the catalyst and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography with the eluent being a solvent mixture of dichloromethane and methanol (CH2Cl2:MeOH = 50:1). Ethyl 7-Boc-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate was finally obtained as a yellow oil (0.973 g, 63% yield). 1H NMR (400 MHz, CDCl3) δ 7.51 (s, 1H), 4.68 (s, 2H), 4.30 (q, J = 7.1 Hz, 2H), 4.00 (t, J = 5.2 Hz, 2H), 3.82 (t, J = 5.2 Hz, 2H), 1.43 (s, 9H), 1.21 (t, J = 7.1 Hz, 3H).