Marin Marinov

The structure of spiro-(fluorene-9,4’-imidazolidine)-2’,5’-dithione was verified by 1D (¹H, ¹³C, DEPT 135) and 2D NMR (¹H-¹H COSY, HMQC and HMBC) spectroscopy. Additionally, the completely assigned NMR data was supported by Raman band assignments. HOSE predictions were incorporated by using the open-access NMRShiftDB database for verification of the assigned ¹³C NMR chemical shifts.

A number of 1D and 2D NMR techniques, such as ¹H, ¹³C, DEPT 135, ¹H-¹H COSY, HSQC, and HMBC, were utilized for the structure verification of 4-(8-propyl-2,4-dithioxo-1,3-diazaspiro[4.5]decan-3-yl)spiro[1,5-dihydro-1,5-benzodiazepine-2,3′-indoline]-2′-one). The NMR spectra provided evidence for the tautomeric conversion of the compound. The completely assigned NMR data was supported additionally by ATR.

A combination of 1D and 2D NMR techniques, including HMQC, HSQC, ¹H-¹H COSY and HMBC, was used to provide completely assigned ¹H and ¹³C NMR data for the structures of three 3-[substituted methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-ones—3-[(4-methoxyphenyl)methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-one, 3-[(4-fluorophenyl)methylidene]-1H,3H-naphtho-[1,8-cd]-pyran-1-one and 3-[(thiophen-3-yl)methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-one. The heteronuclear coupling constants ^1–4J_CF and ^3–4J_HF were correspondingly determined. Additionally, IR and Raman spectral data were provided in support of the assigned structures.

The structure verification of 5′-oxospiro-(fluorene-9,4′-imidazolidine)-2′-thione by NMR is reported. Toward this aim, 2D NMR techniques including ¹H-¹H COSY, HMQC, and HMBC experiments were used to assist with the assignment of the ¹H and ¹³C chemical shifts for the corresponding structure. The mutual interpretation of the 1D and 2D NMR spectra ensured a complete and accurate ¹H and ¹³C NMR data assignment for 5′-oxospiro-(fluorene-9,4′-imidazolidine)-2′-thione.

The structure verification of 5'-oxospiro-(fluorene-9,4'-imidazolidine)-2'-thione by NMR was reported. For the aim, 2D NMR techniques including 1H-1H COSY, HMQC and HMBC experiments were used to assist the assignment of the 1H and 13C chemical shifts for the corresponding structure. The mutual interpretation of the 1D and 2D NMR spectra ensured a complete and an accurate 1H and 13C NMR data assignment for 5'-oxospiro-(fluorene-9,4'-imidazolidine)-2'-thione.

This paper presents the synthesis of a series of Schiff bases derived from phenothiazine derivatives with fluorine benzaldehydes. The compounds were characterized physicochemically by NMR and IR spectroscopy, and their parameters were determined by appropriate methods. Their antimicrobial activity against various microorganisms were studied. One of the compounds showed weak activity against Bacillus subtilis and Salmonella abony. The rest were not active against the microorganisms used. The corrosion characteristics of the obtained compounds were studied using electrochemical techniques (cyclic voltammetry, polarization curves and impedance spectroscopy) in a three-electrode corrosion cell relative to (hydrogen reference electrode) RHE. The samples were applied to an experimental, ground graphite electrode using a spray technique with a thickness of about 50 µm. A detailed analysis of the internal resistance was carried out, including equivalent model schemes and experimental data.

The following article describes the synthesis of phenothiazine derivatives of 1,8-naphthalic anhydride. The target compounds were prepared by an interaction of 6-(10H-phenothiazin-10-yl)-1H,3H-naphtho[1,8-cd]pyran-1,3-dione and its derivatives with H₂O₂, H₂NNH₂, HNO₃/CH₃COOH and HCl, respectively. The compounds obtained were spectroscopically characterized by IR, ¹H NMR and ¹³C NMR including ¹³C DEPT 135. Their antimicrobial activity against Gram-positive and Gram-negative bacteria, yeasts and molds have also been studied. Graphical Abstract

Background: The 1,8-Naphthalimides constitute an important class of biologically active, DNAbinding compounds. There are no available data on the synthesis of 1,8-naphthalimide derivatives with nonprotein amino acids and their biological activity. The aim of this paper was to determine the synthesis, structural characterization and cytotoxic activity of new 1-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)cycloalkane-1- carboxylic acids with 5-, 6-, 7-, 8- and 12-membered rings as well as 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)- yl)adamantane-2-carboxylic acid and 1-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)-1,2,3,4-tetrahydronaphthalene- 1-carboxylic acid. Methods: The target compounds were obtained by an interaction of 1,8-naphthalic anhydride with a series of non-protein amino acids. The optimized geometry and harmonic vibrational frequencies have been calculated by DFT employing B3LYP functional using 6-31G(d,p) basis set. An ab initio (MP2 and Hartee-Fock) and DFT (different functionals) using several basis sets have been applied for NMR calculations. The cytotoxic effects of the synthesized compounds are assessed against two human tumor cell lines, namely K-562 (chronic myeloid leukemia) and HUT-78 (cutaneous T-cell lymphoma) after 72 h exposure, using the MTT-dye reduction assay. The apoptogenic effects and the ability to modulate the NFκB-signaling pathways were determined using commercially available ELISA kits. Results: All compounds inhibited the growth of malignant cells at micromolar concentrations whereby compound 4b (1-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)cyclohexane-1-carboxylic acid) demonstrated superior activity in both cell lines with IC50 values comparable to those of the reference anticancer drug melphalan. Conclusion: New 1,8-naphthalimide derivatives with non-protein amino acids were successfully synthesized. Quantum-chemical calculations were performed to elucidate the structure of the newly synthesized compounds. There is a proper alignment between theoretical and experimental results. The cytotoxicity of the synthesized products against two human tumor cell lines, namely K-562 and HUT-78 was evaluated. All compounds inhibited the growth of malignant cells at micromolar concentrations. The pharmacodynamics evaluation of compound 4b showed that its cytotoxicity is mediated by induction of apoptosis and inhibition of NFκB-signaling.