CCN(CC)CC.[C:8]1([CH:14]=O)[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1.Cl.[CH2:17]([O:19][C:20]([C:22]1[N:23]=[C:24]2[CH2:29][NH:28][CH2:27][CH2:26][N:25]2[CH:30]=1)=[O:21])[CH3:18].[BH3-]C#N.[Na+]>CCO>[CH2:17]([O:19][C:20]([C:22]1[N:23]=[C:24]2[CH2:29][N:28]([CH2:14][C:8]3[CH:9]=[CH:10][CH:11]=[CH:12][CH:13]=3)[CH2:27][CH2:26][N:25]2[CH:30]=1)=[O:21])[CH3:18]Et3N (6.27 mL), PhCHO (4.92 mL) were added successively to the EtOH (81 mL) solution of 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylic acid ethyl ester, hydrochloride (9.47 g) at room temperature and stirred for 3 h under a nitrogen atmosphere. Then NaBH3CN (2.97 g) was added to the reaction mixture and stirred for 19 h. The mixture was filtered through a pad of Celite and diluted with CH2Cl2 and washed with 50% K2CO3 aq. The organic layer was dried (K2CO3) and filtered. The filtrate was concentrated under reduced pressure. The residue was applied to silica gel column chromatography, then the column was eluted with CHCl3-acetone (1/0˜9/1) and CHCl3-MeOH (19/1˜9/1). The titled compound was obtained as pale yellow crystals (4.16 g, 36%).
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