## 3 Results and Discussion  
### Chemistry  
In our previous studies, we have reported the synthesis and _in vitro_ anticancer and antimicrobial activity of 5-oxo-1-arylpyrrolidine-3-carbohydrazide derivatives [35; 36]. The results were promising for further exploration of this scaffold to enhance the anticancer activity and establish the structure-activity-dependent (SAR) properties of 5-oxo-1-arylpyrrolidine-3-carbohydrazide derivatives. In this study, we used commercially available 3,4,5-trimethoxyphenylamine (**1**) that was used for further transformations to obtain various derivatives. We decided to maintain the pyrrolidone scaffold in the molecular design due to its versatile role in medicinal chemistry, particularly due to its conformational rigidity and ability to participate in hydrogen bonding interactions. These properties could potentially enhance the binding affinity and specificity of small molecules. The additional moieties in the designed compounds were selected to complement the physicochemical properties imparted by the pyrrolidone core. Specifically, the 3,4,5-trimethoxyphenyl group was incorporated for its electron-donating characteristics, which enhance the compound's overall stability and bioactivity by modulating electronic effects in the molecule. The key intermediate, 5-oxo-1-(3,4,5-trimethoxyphenyl)pyrrolidine-3-carbohydrazide (**4**), was achieved by a synthetic route illustrated in Scheme 1. Firstly, 3,4,5-trimethoxyphenylamine **1** was reacted with itaconic acid to obtain carboxylic acid **2**, which was then subjected to acid-catalyzed esterification. In the next step, the obtained methyl ester **3** was converted to the target hydrazide **4** in the reaction with hydrazine monohydrate in propan-2-ol. Compound **1** was used as a commercially available starting reagent for further chemical transformations. The diversity of the biological properties of hydrazones [37] and theirsuitability for the development of new drugs led to the incorporation of the synthesis of this type of compound, hoping that their combination with the trimethoxyphenyl moiety in the molecules will affect their biological properties. To incorporate 2-oxoinoldin-3-ylidene fragment, hydrazide **4** was involved in the reaction with the corresponding isatin. The interaction in propan-2-ol at reflux continued for **7** (**5**) or 6.5 (**6**) h, and products were isolated in 68 or 63% yield. The \({}^{1}\)H NMR spectrum of compound **6** in DMSO showed a proton signal of the C(O)-NH group at 12.55 and 13.02 ppm, while the N-H signal of the isatin moiety was visible at 11.12 and 11.25 ppm [38]. In the \({}^{13}\)C NMR spectrum, the isatin C=O carbon spectral line was observed at 174.27 ppm, and the amide and 5-oxopyrrolidine C=O carbon resonances were observed at 171.32 and 171.41 ppm, respectively (Supplementary Files, Figures S9 and S10). A synthetic route to hydrazones having heterocyclic **7**, **8**, and aromatic **9-18** rings in the structures shown in Scheme 1 consists of the reactions of hydrazide **4** with a slight excess of the corresponding aldehyde in propan-2-ol at reflux for 3-11 h. The \({}^{1}\)H NMR spectra of compounds 7 and **8** showed singlets in the ranges of 7.98 and 8.48 and between 11.98 and 12.02 ppm, which belong to the protons of the CH=N and CONH, respectively. Multiplets integrated for one proton in the intervals of 7.21-7.61 and 7.74-8.14 ppm were attributed to the protons of the 2 CH groups of the 5-nitrothien-2-yl fragment (Supplementary Files, Figures S11 and S13). Regarding compounds **9-18**, for example, we can examine the NMR spectra of compound **13**, which has identical spectra to the remaining hydrazones. The \({}^{1}\)H NMR spectrum of **13** showed two singlets of protons of the CH=N fragment at 7.98 and 8.16 ppm, and two singlets at 11.46 and 11.51 ppm for CONH [33]. The remaining signals of the methoxy groups, 5-oxopyrrolidine fragment, and aromatic rings were observed in the region as it was expected.