[CH:1]([C:3]1[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([C:12]([O:14][CH3:15])=[O:13])[CH:10]=2)[NH:5][CH:4]=1)=O.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>CN(C=O)C.C(OCC)(=O)C>[CH3:1][C:3]1[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([C:12]([O:14][CH3:15])=[O:13])[CH:10]=2)[NH:5][CH:4]=1To a solution of the methyl 3-formyl-1H-indole-5-carboxylate (893 mg, 4.4 mmol) in DMF (20 mL) was added the p-toluenesulfonic acid monohydrate (125 mg, 0.7 mmol) and the p-toluenesulfonyl hydrazide (982 mg, 5.3 mmol). The solution has been heated for 20 min at 100° C. The resulting mixture was diluted with ethyl acetate, washed with brine, dried over MgSO4 and concentrated. The crude product is dissolved in THF (40 mL) and NaBH3 CN (1.1 g, 17.6 mmol) was added. The solution has been heated for 8 h at 75° C. The resulting mixture was diluted with ethyl acetate, washed with a solution of 0.5 N HCl, a saturated solution of NaHCO3 and brine, dried over MgSO4 and concentrated. The crude product was purified by flash chromatography (Hexane/AcOEt, from 0 to 30%) to yield a white powder (500 mg, 2.6 mmol, 60%). ESI-MS (m/z): 190 [M+H]+.
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