[N+:1]([C:4]1[CH:5]=[C:6]2[C:10](=[CH:11][CH:12]=1)[NH:9][CH:8]=[CH:7]2)([O-:3])=[O:2].[CH3:13][C:14]1([CH3:22])[O:21][C:19](=[O:20])[CH2:18][C:16](=[O:17])[O:15]1.[CH2:23]=O>C(#N)C.N1CCC[C@H]1C(O)=O>[N+:1]([C:4]1[CH:5]=[C:6]2[C:10](=[CH:11][CH:12]=1)[NH:9][CH:8]=[C:7]2[CH2:23][CH:18]1[C:19](=[O:20])[O:21][C:14]([CH3:22])([CH3:13])[O:15][C:16]1=[O:17])([O-:3])=[O:2]
An adaption of the procedure of Flaugh1 was used. Thus, a solution of 5-nitroindole (50.0 g, 0.32 mol), Meldrum's acid (46.0 g, 0.32 mol), 37% aqueous formaldehyde (26.0 mL, 0.32 mol) and proline (1.8 g, 0.016 mol) in 200 mL of acetonitrile was stirred at room temperature for 18 h. The resulting thick yellow slurry was filtered and the filtercake was washed with acetonitrile, then acetone and finally with ether. This material was dried/in vacuo to give the title compound (80.0 g, 81%) as a bright yellow solid, mp 182° C. (dec). The mother liquor was concentrated and then diluted with H2O, and the resulting solid was collected, washed and dried as before to give a second crop of the product (7.0 g) as a darker yellow solid. Total yield=87.0 g (89%): IR (KBr) 3330, 1767, 1732 cm-1 ; 1H NMR (DMSO-d6, 200 MHz) δ11.64 (s, 1H), 8.63 (d, J=2.2 Hz, 1H), 7.96 (dd, J=9.0, 2.2 Hz, 1H), 7.49 (d, J=9.0 Hz, 1H), 7.33 (d, J=2.2 Hz, 1H), 4.84 (t, J=4.6 Hz, 1H), 3.45 (d, J=4.5 Hz, 2H), 1.78 (s, 3H), 1.55 (s, 3H). Anal. Calcd for C15H14N2O6 : C, 56.60; H, 4.43; N, 8.80. Found: C, 56.62; H, 4.41; N, 8.91.
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