C([O:3][C:4]([C:6]1[N:7]([CH2:14][CH2:15][CH:16]([CH3:18])[CH3:17])[CH:8]=[C:9]([N+:11]([O-:13])=[O:12])[CH:10]=1)=[O:5])C.[OH-].[Na+]>CO>[CH3:17][CH:16]([CH3:18])[CH2:15][CH2:14][N:7]1[CH:8]=[C:9]([N+:11]([O-:13])=[O:12])[CH:10]=[C:6]1[C:4]([OH:5])=[O:3]1-(3-Methyl-butyl)-4-nitro-1H-pyrrole-2-carboxylic acid ethyl ester (1.44 g,) was dissolved in 50 ml of methanol and 25 ml of 20% aqueous NaOH was added. The reaction mixture was stirred at 50° C. for 1.5 h until there was no starting material checked by TLC. The reaction mixture was concentrated to about 20 ml, 200 ml of water was added. The resulting solution was neutralized with 5 M hydrochloric acid to pH 2 and the precipitates formed were collected by filtration, washed with water and dried to give 1-(3-methyl-butyl)-4-nitro-1H-pyrrole-2-carboxylic acid (1.29 g, 99%). 1H NMR (DMSO-d6) δ13.12 (br. s, 1H), 8.27 (d, 1H), 7.26 (d, 1H), 4.36 (t, 2H), 1.59 (dd, 2H), 1.50 (dt, 1H), 0.88 (d, 6H).
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