## 2 Materials and Methods  
### Synthesis  
Reagents and solvents were purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. The reaction course and purity of the synthesized compounds were monitored by TLC using aluminum plates precoated with silica gel with F254 nm (Merck KGaA, Darmstadt, Germany). NMR spectra were recorded on a Brucker Avance III (400, 101 MHz) spectrometer (Bruker BioSpin AG, Fallanden, Switzerland). Chemical shifts were reported in (8) ppm relative to tetramethylsilane (TMS), with the residual solvent as an internal reference (DMSO-d\({}_{6}\), \(\delta\) = 2.50 ppm for \({}^{1}\)H and \(\delta\) = 39.52 ppm for \({}^{13}\)C). Data are reported as follows: chemical shift, multiplicity, coupling constant [Hz], integration, and assignment. Melting points were determined with a B-540 melting point analyzer (Buchi Corporation, New Castle, DE, USA) and were uncorrected. Elemental analyses (C, H, and N) were conducted using the Elemental Analyzer CE-440 (Exeter Analytical, Inc., North Chelmsford, MA, USA), and their results were found to be in good agreement (\(\pm\)0.3%) with the calculated values. IR spectra (\(\
u\), cm\({}^{-1}\)) were recorded on a Perkin-Elmer Spectrum BX FT-IR spectrometer (Perkin-Elmer Inc., Waltham, MA, USA) using KBr pellets. 5-Oxo-1-(3,4,5-trimethoxyphenyl)pyrrolidine-3-carboxylic acid (**2**)  
A mixture of 3,4,5-trimethoxysaniline (**1**) (20 g, 109 mmol), itaconic acid (21.3 g, 164 mmol), and water (200 mL) was heated at reflux for 7 h. After completion of the reaction, the mixture was cooled, the formed crystalline solid was filtered off and washed with water, then diethyl ether. The crude product was purified by dissolving it in 5% sodium hydroxide solution, filtering, and acidifying the filtrate with hydrochloric acid to pH 1 (the procedure was performed twice). Grayish powder, yield 24.6 g (76.3%), m. p. 140-142 \({}^{\circ}\)C.  
\({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\): 2.64-2.82 (m, 2H, CH\({}_{2}\)CO), 3.27-3.39 (m, 1H, CH), 3.63, 3.76 (2s, 9H, 3 OCH\({}_{3}\)), 3.92-4.10 (m, 2H, NCH\({}_{2}\)), 6.97 (s, 2H, H\({}_{\rm Ar}\)), 12.82 (br s, 1H, OH) ppm. \({}^{13}\)C NMR (101 MHz, DMSO-\(d_{6}\)) \(\delta\): 34.08, 35.36, 50.43, 55.94, 60.15, 97.91, 134.27, 135.24, 152.71, 171.76, 174.27 ppm. IR (KBr): \(\
u_{\rm max}\): 3497 (OH), 1736, 1667 (2C=O), 1273, 1235 (3 OCH\({}_{3}\)) cm\({}^{-1}\). Anal. Calcd. for C\({}_{14}\)H\({}_{17}\)NO\({}_{6}\), %: C 56.95; H 5.80; N 4.74. Found: C 56.83; H 5.71; N 4.65. Methyl 5-oxo-1-(3,4,5-trimethoxyphenyl)pyrrolidine-3-carboxylate (**3**)  
To a solution of carboxylic acid **2** (22.13 g, 75 mmol) in methanol (200 mL), conc. sulfuric acid (3 mL) was added dropwise, and the mixture was heated at reflux for 8 h. Afterwards, the solvent was evaporated under reduced pressure, and then the residue was neutralized with 10% sodium carbonate solution to pH 6. The obtained solid was filtered off, washed with plenty of water, and recrystallized from methanol. Dark grayish solid, yield 19.48 g (84%), m. p. 94-95 \({}^{\circ}\)C.  
\({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\): 2.67-2.84 (m, 2H, CH\({}_{2}\)CO), 3.40-3.59 (m, 1H, CH), 3.63 (s, 3H, OCH\({}_{3}\)), 3.69 (s, 3H, COOCH\({}_{3}\)), 3.76 (s, 6H, 2 OCH\({}_{3}\)), 3.93-4.13 (m, 2H, NCH\({}_{2}\)), 6.96 (s, 2H, H\({}_{Ar}\)) ppm. \({}^{13}\)C NMR (101 MHz, DMSO-\(d_{6}\)) \(\delta\): 34.83, 35.13, 51.17, 52.18, 55.91, 60.10, 97.95, 134.30, 135.09, 152.67, 171.41, 173.11 ppm. IR (KBr): \(\gamma_{\rm max}\): 1745, 1695 (2C=O), 1257, 1236 (3 OCH\({}_{3}\)) cm\({}^{-1}\). Anal. Calcd. for C\({}_{15}\)H\({}_{19}\)NO\({}_{6}\), %: C 58.25; H 6.19; N 4.53.