[N+:1]([C:4]1[CH:12]=[CH:11][C:10]2[N:9]3[CH2:13][CH2:14][CH2:15][C:8]3=[CH:7][C:6]=2[C:5]=1[C:16]([O:18][CH3:19])=[O:17])([O-:3])=[O:2].C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>C(O)(C(F)(F)F)=O.C1(C)C=CC=CC=1>[N+:1]([C:4]1[CH:12]=[CH:11][C:10]2[N:9]3[CH2:13][CH2:14][CH2:15][CH:8]3[CH2:7][C:6]=2[C:5]=1[C:16]([O:18][CH3:19])=[O:17])([O-:3])=[O:2]Methyl 7-nitro-2,3-dihydro-1H-pyrrolo[1,2-a]indole-8-carboxylate (Intermediate 19, 1.00 g) was dissolved in TFA (100 ml) and sodium triacetoxyborohydride (8.11 g) was added. The reaction mixture was stirred at room temperature, then diluted with toluene and concentrated in vacuo. The residue was dissolved in aqueous potassium carbonate solution and extracted with ethyl acetate, dried (MgSO4) and filtered. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of methanol and DCM, with a gradient of 0-2% to give methyl 7-nitro-2,3,9,9a-tetrahydro-1H-pyrrolo[1,2-a]indole-8-carboxylate (1.66 g) as a yellow gum.
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