[CH3:1][CH:2]([CH3:17])[C:3]([NH:5][C:6]1[CH:16]=[CH:15][C:9]([C:10]([O:12][CH2:13][CH3:14])=[O:11])=[CH:8][CH:7]=1)=[O:4].[N+:18]([O-])([OH:20])=[O:19].C(OCC)(=O)C.CCCCCC>O>[CH3:17][CH:2]([CH3:1])[C:3]([NH:5][C:6]1[CH:16]=[CH:15][C:9]([C:10]([O:12][CH2:13][CH3:14])=[O:11])=[CH:8][C:7]=1[N+:18]([O-:20])=[O:19])=[O:4]Ethyl 4-(2-methylpropionylamino)benzoate (Chemical Abstract 114(11) 101280u; Vagaonescu; Marisa, N-Acyl Derivatives of Anesthesin. Stud Univ. Banes-Bolyai Chem. 1989, 34, 12-14) was added slowly over a 50-min period to fuming nitric acid at 10° C. The reaction was stirred for 30 min at room temperature. Thin-layer chromatographic analysis (SiO2, 1:1 ethyl acetate:hexane) showed disappearance of the starting material along with the formation of a new higher-running spot (Rf =0.9). The reaction was poured into water and then extracted with ethyl acetate (3×500 mL). Next, the organic layer was washed with 1% sodium bicarbonate (500 mL) solution and then water (500 mL). The ethyl acetate layer was concentrated and the residue chromatographed (SiO2, 1:5 ethyl acetate:hexane). The fractions containing product were concentrated to give 17 g (49%) of ethyl 4-(2-methylpropionylamino)-3-nitrobenzoate as a yellow solid, mp 74°-76° C. An analytical sample was prepared by recrystallization from hexane. This material was collected by filtration and dried in vacuo at acetone reflux.
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