A warm solution of 55 (447 mg, 1.29 mmol) in CH3NO2 (50 mL) was cooled in an ice bath. As the starting material began to precipitate (internal temperature ca. 5° C.) c.HNO3 (0.16 mL, 2.6 mmol) was added dropwise, giving an orange-red mixture. The suspension was stirred at 0° C. for 40 min, then poured into cold H2O and extracted with CH2Cl2 (×3). The extracts were washed with aq. NaHCO3, dried (Na2SO4), and evaporated. The residue was recrystallized from MeOH to give methyl 3-(t-butyloxycarbonyl)-1-hydroxymethyl-5-nitro-1,2-dihydro-3H-pyrrolo[3,2-e]indole-7-carboxylate (29) as an orange powder (229 mg, 45%), mp 200° C. (dec.). The mother liquor was purified by chromatography (40% EtOAc-petroleum ether) to give more 29 (70 mg, 14%). 1NMR [(CD3)2SO] δ 11.22 (d, J=1.5 Hz, 1 H, NH), 8.72 (br, s, ca. 0.8 H, H-4 major rotamer), 8.42 (br s, ca. 0.2 H, H-4 minor rotamer), 7.47 (d, J=2.0 Hz, 1 H, H-8), 5.02 (t, J=5.2 Hz, 1 H, OH), 4.14 (t, J=10.5 Hz, 1 H), 3.95 (dd, J=11.2, 4.7 Hz, 1 H), 3.92 (s, 3 H, CO2Me), 3.89-3.80 (m, 1 H), 3.73 (t, J=5.2 Hz, 2 H), 1.54 (s, 9 H, t-Bu). Anal. Calculated for C18H21N3O7 : C, 55.2; H, 5.4; N, 10.7. Found: C, 55.4; H, 5.4; N, 10.7%.
