反应详情

Trifluoroacetic acid (20 mL) was added at 0° C. to a solution of 2-amino-9,10-dimethoxy-1,6,7,11b-tetrahydro-4H-pyrido[2,1-a]isoquinoline-3-carboxylic acid ethyl ester (Example 1a; 2.00 g, 6.02 mmol) in tetrahydrofuran (20 mL), then after 30 min the homogeneous solution was treated with sodium borohydride (474 mg, 12.0 mmol) and stirred for another 40 min. The reaction mixture was concentrated in vacuo and the residue partitioned between 2 M aq. sodium hydroxide solution and dichloromethane. The organic layer was washed with brine, dried (MgSO4) and evaporated. The residue was dissolved in methanol (37 mL) and acetic acid (9 mL) and treated with benzaldehyde (723 mg, 6.81 mmol), then sodium cyanoborohydride (526 mg, 7.95 mmol) was added portionwise at r.t. over 1 h. The reaction mixture was stirred another 15 min, then partitioned between sat. aq. sodium hydrogencarbonate solution and dichoromethane. The organic layer was washed with brine, dried (MgSO4), and evaporated. Chromatrography of the residue (SiO2, CH2Cl2/EtOAc 4:1, after elution of dibenzylated side-product, CH2Cl2/MeOH/NH4OH 95:5:0.25) afforded the title compound (1.31 g, 51%). Red oil, MS (ISP) 425.2 (M+H)+.

1. concentrationThe reaction mixture was concentrated in vacuo
2. customthe residue partitioned between 2 M aq. sodium hydroxide solution and dichloromethane
3. washThe organic layer was washed with brine
4. dry with materialdried (MgSO4)
5. customevaporated
6. dissolutionThe residue was dissolved in methanol (37 mL)
7. stirringThe reaction mixture was stirred another 15 min
8. custompartitioned between sat. aq. sodium hydrogencarbonate solution and dichoromethane
9. washThe organic layer was washed with brine
10. dry with materialdried (MgSO4)
11. customevaporated
12. washChromatrography of the residue (SiO2, CH2Cl2/EtOAc 4:1, after elution of dibenzylated side-product, CH2Cl2/MeOH/NH4OH 95:5:0.25)