Synthesis, characterization, and anticonvulsant activity of enaminones. Part 5: investigations on 3-carboalkoxy-2-methyl-2,3-dihydro-1H-phenothizin-4[10H]-one derivatives

Engineering Phenothiazine-Based Functional Mimics of Host Defense Peptides as New Agrochemical Candidates: Design, Synthesis, and Antibacterial Evaluation

In the protracted "arms race" between host and plant pathogenic bacteria, host organisms have evolved powerful weapons known as host defense peptides (HDPs). However, natural HDPs are not suitable for large-scale applications; therefore, researchers have chosen to develop bespoke small-molecule functional mimics. Phenothiazine derivatives were developed as functional HDPs mimics, owing to their broad biological activity and high lipophilicity. The phenothiazine analogues designed in this study exhibited excellent in vitro bioactivity against the three Gram-negative bacteria Xanthomonas oryzae pv oryzae, Xanthomonas axonopodis pv citri, and Pseudomonas syringae pv actinidiae, with optimal EC50 values of 0.80, 0.31, and 1.91 μg/mL, respectively. Preliminary evidence suggests that compound C2 may act on bacterial cell membranes and interact with bacterial Deoxyribonucleic acid in the groove binding mode. In vivo trials showed that compound C2 was highly effective against rice leaf blight (51.97-56.69%), with activity superior to those of bismerthiazol (40.7-43.4%) and thiodiazole copper (30.2-37.1%). Our study provides strong evidence to support the development of phenothiazine derivatives into pesticide candidates.

Studies with heteroaromatic amines. A new route to 2-azolylamino-2-thiazolin-4-ones

Heteroaromatic chloroacetamides 3a–c on treatment with potassium thiocyanate afforded the thiazolylamino-thiazolines 6a–c via intermediacy of 4a–c and 5a–c. Compounds 6a–c condensed with dimethylformamide dimethylacetal (DMFDMA) to yield the Z–enamines 7a–c. The enamines 7a and 7b could be converted into the enamines 8a–e and 9a,b on treatment with amines. However, reacting 10c with morpholine afforded 11b. Compounds 9a,b, as well as 9c, were also obtained on reacting 6a–c with triethyl orthoformate and piperidine in DMF. The structures of 6a and 11b were confirmed by X-ray crystal structure determination.

FT-IR, molecular structure, first order hyperpolarizability, NBO analysis, HOMO and LUMO and MEP analysis of 1-(10H-phenothiazin-2-yl)ethanone by HF and density functional methods

FT-IR spectrum of 1-(10H-phenothiazin-2-yl)ethanone was recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers were investigated with the help of HF and DFT methods. The normal modes are assigned with the help of potential energy distribution analysis. The observed vibrational wavenumbers were compared with the calculated results. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values. The first hyperpolarizability value is also reported. Natural bond orbital analysis confirms the presence of intra-molecular charge transfer and hydrogen bonding interaction. The HOMO-LUMO gap explains the charge transfer interaction taking place within the molecule. The N-H stretching frequency is red shifted in the IR spectrum with a strong intensity from the computed frequency, which indicates weakening of the N-H bond resulting in proton transfer to the neighboring units. From the MEP analysis it is evident that the negative charge covers the carbonyl and benzene and the positive region is over the NH group.

Vibrational spectroscopic (FT-IR, FT-Raman) and quantum chemical calculations of 1-(5,5-dioxido-10H-phenothiazin-10-yl)ethanone

FT-IR and FT-Raman spectra of 1-(5,5-dioxido-10H-phenothiazin-10-yl)ethanone were recorded and analyzed. The vibrational wavenumbers were computed using B3LYP/6-31G∗ and SDD basis. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using NBO analysis. Molecular electrostatic potential was performed by the DFT method and infrared intensities and Raman activities are also reported. MEP shows that the negative potential sites are on oxygen atoms and the positive potential sites are around the nitrogen atoms. The geometrical parameters of the title compound (SDD) are in agreement with XRD crystal structure data. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of nonlinear optics.

Synthesis, Reactions and Antitumour Screening of new Enaminones

A new series of enaminones derived from 3-acetyl-1-aryl-4-benzoyl-5-phenyl-1 H-pyrazoles has been obtained and their reactions with hydrazine hydrate, guanidine hydrochloride, 3-amino-1,2,4-triazole, 2-aminobenzimidazole and active methylenenitriles are described. The mechanisms and regioselectivity of the studied reactions are discussed. The results of screening of the antitumor activity of the enaminones against the human breast cancer cell line MCF-7 revealed that the compounds showed less activity than that of the reference drug doxorubicin. Their activity was found to depend on the nature of the substituent group on the 1-aryl moiety. The order of activity of the series is: H > 4–Cl > 4-MeO > 4-Me > 4-NO2.

Enaminones 8: CoMFA and CoMSIA studies on some anticonvulsant enaminones

3D-QSAR studies comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were carried out on 26 structurally diverse subcutaneous pentylenetetrazol (scPTZ) active enaminone analogues, previously synthesized in our laboratory. CoMFA and CoMSIA were employed to generate models to define the specific structural and electrostatic features essential for enhanced binding to the putative GABA receptor. The 3D-QSAR models demonstrated a reliable ability to predict the CLogP of the active anticonvulsant enaminones, resulting in a q(2) of 0.558 for CoMFA, and a q(2) of 0.698 for CoMSIA. The outcomes of the contour maps for both models provide detailed insight for the structural design of novel enaminone derivatives as potential anticonvulsant agents.

Enaminones: Exploring Additional Therapeutic Activities

Enaminones, enamines of beta-dicarbonyl compounds, have been known for many years. Their early use has been relegated to serving as synthetic intermediates in organic synthesis and of late, in pharmaceutical development. Recently, the therapeutic potential of these entities has been realized. This review provides the background and current research in this area with emphasis of these agents as potential anticonvulsants, their proposed mechanisms of action, and as potential modulators of multidrug resistance (MDR).

Synthesis and anticonvulsant activity of enaminones. 4. Investigations on isoxazole derivatives

Due to the exceptional anticonvulsant activity displayed by substituted aniline enaminones, related pyridine derivatives and phenothiazines synthesised in our laboratories, the further investigation of various aromatic heterocycles was undertaken. Condensation of cyclic 1,3-diketo esters with 3-, and 5-aminoisoxazole derivatives led to a series of potent anti-maximal electroshock (MES) analogues, three of which occurred in the 3-amino series: ethyl ester (10), orally (po) active in rats [ED(50) 68.9 mg kg(-1), TD(50) > 500 mg kg(-1), protective index (PI = TD(50)/ED(50)) > 49.6]; methyl ester (9), ED(50) 68.9 mg kg(-1) intraperitoneally (ip) in mice, TD(50) > 500 mg kg(-1), PI > 7.3, and tert-butyl ester (8), ED(50) 28.1 mg kg(-1) po in rats, TD(50) > 500 mg kg(-1), PI > 17.8. Sodium channel binding studies, as well as evaluations against pentylenetetrazol, bicuculline, and picrotoxin on isoxazole 10 were all negative, leading to an unknown mechanism of action. X-ray diffraction patterns of a representative of the 3-amino series (isoxazoles 6-11) unequivocally display the existence of intramolecular hydrogen bonding of the nitrogen to the vinylic proton in the cyclohexene ring, providing a pseudo three ring structure which was also shown previously with the vinylic benzamides. Physicochemical-permeability across the BBB suggested an efflux mechanism for the previously synthesised aniline enaminones, but not with isoxazole 10.

Synthesis, characterization and anticonvulsant activity of enaminones. Part 6: Synthesis of substituted vinylic benzamides as potential anticonvulsants

A comparison of enaminones from various unsubstituted and p-substituted benzamides to the analogous benzylamines has been undertaken with the aim of elucidating the essential structural parameters necessary for anticonvulsant activity. Initial studies on methyl 4-N-(benzylamino)-6-methyl-2-oxocyclohex-3-en-1-oate, 3a, 3-N-(benzylamino)cyclohex-2-en-1-one, 3p, and 5,5-dimethyl-3-N-(benzylamino)-cyclohex-2-en-1-one, 3r indicated that benzylamines possessed significant anti-maximal electroshock seizure (MES) activity. Evaluation of the analogous benzamides revealed significant differences in anticonvulsant activity, these differences were most probably related to the differences in their three-dimensional structures.