Synthesis and Antimicrobial Activity of Some Condensed [4-(2,4,6-Trimethylphenyl)-1(2H)-oxo-phthalazin-2-yl]acetic Acid Hydrazide

2-Methyl-6-(4-aminophenyl)-4,5-dihydro-3(2H)-pyridazinone Synthon for Some New Annelated 1,2,3-Selena/Thiadiazoles and 2H-Diazaphospholes with Anticipated Biological Activity and Quantum Chemical Calculations

A convenient and efficient synthetic protocol for the new selenadiazole. Thiadiazole and diazaphosphole derivatives incorporating a pyridazine moiety originating from 4-(4-aminophenyl)-4-oxobutanoic acid (1) were described. All newly synthesized compounds were evaluated for their antimicrobial activity using the disk diffusion method, and their cytotoxicity was evaluated against brine shrimp lethality bioassay. Using density functional theory (DFT), the frontier molecular orbital (FMO) and molecular electrostatic potential (MEPS) were studied to estimate the chemical reactivity and kinetic stability of each structure. Therefore, global descriptor parameters like electronegativity (χ), chemical hardness (η), and global softness (σ) were calculated. Consequently, the attained results were compared with the experimental data of the biological activity of the studied structures.

Synthesis of Some Mono- and Disaccharide-Grafting Phthalazine Derivatives and Some New Se-Nucleoside Analogues: Antibacterial Properties, Quantum Chemical Calculations, and Cytotoxicity

A highly efficient and versatile synthetic approach for the synthesis of 4-(pyren-1-ylmethyl)-1-(d-glycosyloxy) phthalazine nucleosides 11a,b, 13, β-S-nucleosides 16, 18, 20, and acyclo C-nucleosides 23a,b, 24, 25 and 27a-f was described and fully characterized. Furthermore, a series of desired new nucleoside analogues containing Se of 4-(pyren-1-ylmethyl) phthalazine-1(2H)-selenone 28-33 were synthesized. The structures of all reported compounds were confirmed by IR, ¹H-NMR, ¹³C-NMR, MS and elemental analysis. All compounds have been screened for their antibacterial and antifungal activities. Maximum activity was shown by 20 and 33a comparable to the standard drugs with lower toxicity. The cytotoxicity of the selected compound was measured and evaluated. The energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital was calculated using theoretical computations to reflect the chemical reactivity and kinetic stability of the synthesized compounds. Using density functional theory (DFT), electronic parameters such as the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) and the molecular electrostatic potential (MEPS) were calculated. On the basis of different studied structures, these properties were computed in order to elucidate the chemical reactivity and the kinetic stability. Obviously, the band gap energy (Eg) of structures studied reveals that the lowest band gap obtained for the structure 16-a indicates that it has the highest chemical reactivity and lowest kinetic stability.

Improvement of antibacterial activity of some sulfa drugs through linkage to certain phthalazin-1(2H)-one scaffolds

RAB1 5 is a lead antibacterial agent in which trimethoprim is linked to phthalazine moiety. Similarly, our strategy in this research depends on the interconnection between some sulfa drugs and certain phthalazin-1(2H)-one scaffolds in an attempt to enhance their antibacterial activity. This approach was achieved through the combination of 4-substituted phthalazin-1(2H)-ones 9a, b or 14a, b with sulfanilamide 1a, sulfathiazole 1b or sulfadiazine 1c through amide linkers 6a, b to produce the target compounds 10a-d and 15a-e, respectively. The antibacterial activity of the newly synthesized compounds showed that all tested compounds have antibacterial activity higher than that of their reference sulfa drugs 1a-c. Compound 10c represented the highest antibacterial activity against Gram-positive bacteria Streptococcus pneumonia and Staphylococcus aureus with MIC = 0.39 μmol/mL. Moreover, compound 10d displayed excellent antibacterial activity against Gram-negative bacteria Escherichia coli and Salmonella typhimurium with MIC = 0.39 and 0.78 μmol/mL, respectively.

Synthesis of 2-aryl-1,2-dihydrophthalazines via reaction of 2-(bromomethyl)benzaldehydes with arylhydrazines

The reaction of 2-(bromomethyl)benzaldehydes with arylhydrazines employing K(2)CO(3) as a base and FeCl(3) as a catalyst in CH(3)CN at 100 °C delivers 2-aryl-1,2-dihydrophthalazines with yields ranging from 60 to 91%. The transformation is considered to proceed as an intermolecular condensation/intramolecular nucleophilic substitution.