Novel delta2-isoxazolines as group II phospholipase A2 inhibitors

Investigation of NPB Analogs That Target Phosphorylation of BAD-Ser99 in Human Mammary Carcinoma Cells

The design and development of a small molecule named NPB [3-{(4(2,3-dichlorophenyl)piperazin-1-yl}{2-hydroxyphenyl)methyl}-N-cyclopentylbenzamide], which specifically inhibited the phosphorylation of BAD at Ser99 in human carcinoma cells has been previously reported. Herein, the synthesis, characterization, and effect on cancer cell viability of NPB analogs, and the single-crystal X-ray crystallographic studies of an example compound (4r), which was grown via slow-solvent evaporation technique is reported. Screening for loss of viability in mammary carcinoma cells revealed that compounds such as 2[(4(2,3-dichlorophenyl)piperazin-1-yl][naphthalen-1-yl]methyl)phenol (4e), 5[(4(2,3-dichlorophenyl)piperazin-1-yl][2-hydroxyphenyl)methyl)uran-2-carbaldehyde (4f), 3[(2-hydroxyphenyl][4(p-tolyl)piperazin-1-yl)methyl)benzaldehyde (4i), and NPB inhibited the viability of MCF-7 cells with IC₅₀ values of 5.90, 3.11, 7.68, and 6.5 µM, respectively. The loss of cell viability was enhanced by the NPB analogs synthesized by adding newer rings such as naphthalene and furan-2-carbaldehyde in place of N-cyclopentyl-benzamide of NPB. Furthermore, these compounds decreased Ser99 phosphorylation of hBAD. Additional in silico density functional theory calculations suggested possibilities for other analogs of NPB that may be more suitable for further development.

Copper-Catalyzed Annulation Reaction of Alkenes and N-Alkyl(aryl)-1-(methylthio)-2-nitroethenamine: an Approach for the Synthesis of Isoxazole Derivatives

A copper-catalyzed annulation reaction to access a variety of isoxazoles from alkenes and oxazete in situ generated from N-alkyl(aryl)-1-(methylthio)-2-nitroethenamine was reported. A plausible mechanism underlying the formation of the product was proposed, which represented a new approach for the construction of isoxazolines. This reaction was capable of tolerating alkenes bearing various substituents, which showed a relatively broad substrate scope with good functional group compatibility.

Synthesis of Isoxazolines and Oxazines by Electrochemical Intermolecular [2 + 1 + n] Annulation: Diazo Compounds Act as Radical Acceptors

Reported herein is an unprecedented synthesis of isoxazolines and oxazines through electrochemical intermolecular annulation of alkenes with tert-butyl nitrite, in which diazo compounds serve as radical acceptors. Notably, [2 + 1 + 2] and [2 + 1 + 3] annulations occur when styrenes and allylbenzenes are used as substrates, respectively. The latter reaction undergoes group migration to form more stable radical, manifesting radical route instead of conventional 1,3-dipolar cycloaddition occurs. Moreover, scale-up experiments suggest the potential application value of these transformations in industry.

Evaluation of anti-inflammatory activity and molecular docking study of new aza-bicyclic isoxazoline acylhydrazone derivatives

The aim of this study was to investigate the anti-inflammatory effects of two new isoxazoline-acylhydrazone derivatives: N'-(4-methoxybenzylidene)-6-(4-nitro-benzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-123) and N'-(4-chlorobenzylidene)-6-(4-chlorobenzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-99). An air pouch induced by carrageenan was used for screening the best dose of R-99 and R-123. Using this mouse model, leukocyte migration and cytokine levels (TNF-α and IL-1β) were determined. Paw edema induced by several phlogistic agents and vascular permeability induced by acetic acid were employed to investigate the mechanism of action of the isoxazoline-acylhydrazone derivatives. A docking study was performed with the human histamine H1 receptor to investigate potential antihistaminic activity. Treatment with the compounds reduced leukocyte migration in the air pouch at all doses tested. TNF-α and IL-1β levels were similarly reduced by the two compounds. Vasoactive amines were inhibited in models of paw edema induced by several agents and vascular permeability induced by acetic acid. The docking study suggests that R-99 and R-123 may be inhibitors of the histamine H1 receptor. In conclusion, the results indicate that R-99 and R-123 exhibit promising anti-inflammatory activity related to their ability to inhibit TNF-α, IL-1β, and vasoactive amine production, as well as reduce leukocyte migration and inhibit mast cell degranulation.

Synthesis and X-ray Crystal Studies of 6-(2-chlorophenyl)-3-methyl[1,2,4] triazolo[4,5-b][1,3,4]thiadiazole

The compound 6-(2-chlorophenyl)-3-methyl[1,2,4]triazolo[4,5-b][1,3,4]thiadiazole, was synthesised using different reagents and conditions, characterised by spectroscopic techniques and finally confirmed by X-ray crystal structure analysis. The title compound crystallises in monoclinic class under the space group P21/c with cell parameters, a=10.6710 (6)Å, b=7.3660 (4)Å, c=14.3900 (8)Å, β=110.403 (3)°, Z=2 and R1= 0.0396 for 2715 reflections [I>2ΣI]. The structure exhibits inter-molecular hydrogen bonding.

Green Organocatalytic Synthesis of Isoxazolines via a One-Pot Oxidation of Allyloximes

A green, sustainable, organocatalytic, and efficient synthesis of isoxazolines from allyloximes was developed. A 2,2,2-trifluoroacetophenone-catalyzed oxidation of allyloximes, utilizing H₂O₂ as the green oxidant, was taken advantage of in order to introduce a cheap and environmentally friendly protocol for the synthesis of substituted isoxazolines. A variety of substitution patterns, both aromatic and aliphatic moieties, are well tolerated, leading to isoxazolines in moderate to excellent yields.

Strong deshielding in aromatic isoxazolines

Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared from acridin-4-yl dipolarophiles and stable benzonitrile oxides (BNO). Three alkenes, (acridin-4-yl)-CH=CH-R (R = COOCH3, Ph, and CONH2), reacted with three BNO dipoles (2,4,6-trimethoxy, 2,4,6-trimethyl, 2,6-dichloro) to give pairs of target isoxazolines with acridine bound to C-4 or C-5 carbon of the isoxazoline (denoted as 4-Acr or 5-Acr). Regioselectivity was dependent on both the dipolarophile and dipole character. The ester and amide dipolarophile displayed variable regioselectivity in cycloadditions whereas the styrene one afforded prevailing 4-Acr regioisomers. 2,4,6-Trimethoxy-BNO was most prone to form 5-Acr isoxazolines while mesitonitrile oxide gave major 4-Acr isoxazolines. Basic hydrolysis of the amide cycloadduct led to an unexpected isoxazolone product. The structure of the target compounds was studied by NMR, MS, and X-ray crystallography.

Virtual analysis of structurally diverse synthetic analogs as inhibitors of snake venom secretory phospholipase A2

Due to the toxic pathophysiological role of snake venom phospholipase A2 (PLA2 ), its compelling limitations to anti-venom therapy in humans and the need for alternative therapy foster considerable pharmacological interest towards search of PLA2 specific inhibitors. In this study, an integrated approach involving homology modeling, molecular dynamics and molecular docking studies on VRV-PL-V (Vipera russellii venom phospholipase A2 fraction-V) belonging to Group II-B secretory PLA2 from Daboia russelli pulchella is carried out in order to study the structure-based inhibitor design. The accuracy of the model was validated using multiple computational approaches. The molecular docking study of this protein was undertaken using different classes of experimentally proven, structurally diverse synthetic inhibitors of secretory PLA2 whose selection is based on IC50 value that ranges from 25 μM to 100 μM. Estimation of protein-ligand contacts by docking analysis sheds light on the importance of His 47 and Asp 48 within the VRV-PL-V binding pocket as key residue for hydrogen bond interaction with ligands. Our virtual analysis revealed that compounds with different scaffold binds to the same active site region. ADME analysis was also further performed to filter and identify the best potential specific inhibitor against VRV-PL-V. Additionally, the e-pharmacophore was generated for the best potential specific inhibitor against VRV-PL-V and reported here. The present study should therefore play a guiding role in the experimental design of VRV-PL-V inhibitors that may provide better therapeutic molecular models for PLA2 recognition and anti-ophidian activity.

Synthesis and characterization of novel oxazines and demonstration that they specifically target cyclooxygenase 2

In the present study, we used solution combustion synthesis-bismuth oxide (Bi2O3) as catalyst for the simple and efficient synthesis of 1,2-oxazine based derivatives of 6-fluoro-3-(piperidin-4-yl)benzo[d]isoxazoles, 1-arylpiperazine and carbazoles. (4aR,8aR)-4-(4-Methoxyphenyl)-3-((4-(4-methoxyphenyl)piperazin-1-yl)methyl)-4a,5,6,7,8,8a-hexahydro-4H-benzo[e][1,2]oxazine was found to be the most potent compound with a high degree of selectivity in inhibition towards COX2 (1.7 μM) over COX1 (40.4 μM) demonstrating the significance of 1,2-oxazine derivatives in developing COX2 specific inhibitors. Molecular docking analyses demonstrated that an isoleucine residue in the active site of COX1 is responsible for lower affinity to COX1 and increased potency towards COX2. Overall, our study reveals that the new 1,2-oxazine-based small molecules qualify as lead structures in developing COX2-specific inhibitors for anti-inflammatory therapy.

MOLPRINT 2D-based identification and synthesis of novel chromene based small molecules that target PLA2: validation through chemo- and bioinformatics approaches

A chemoinformatics approach identified 2-Amino-4-(2′-methyl-[1,1′-biphenyl]-4-yl)-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile as a snake venom PLA2 inhibitor, this was confirmed with an IC₅₀ = 12.5 μM.

Novel apigenin based small molecule that targets snake venom metalloproteases

The classical antivenom therapy has appreciably reduced snakebite mortality rate and thus is the only savior drug available. Unfortunately, it considerably fails to shield the viper bite complications like hemorrhage, local tissue degradation and necrosis responsible for severe morbidity. Moreover, the therapy is also tagged with limitations including anaphylaxis, serum sickness and poor availability. Over the last decade, snake venom metalloproteases (SVMPs) are reported to be the primary component responsible for hemorrhage and tissue degradation at bitten site. Thus, antivenom inability to offset viper venom-induced local toxicity has been a basis for an insistent search for SVMP inhibitors. Here we report the inhibitory effect of compound 5d, an apigenin based molecule against SVMPs both in silico and in vivo. Several apigenin analogues are synthesized using multicomponent Ugi reactions. Among them, compound 5d effectively abrogated Echis carinatus (EC) venom-induced local hemorrhage, tissue necrosis and myotoxicity in a dose dependant fashion. The histopathological study further conferred effective inhibition of basement membrane degradation, and accumulation of inflammatory leucocytes at the site of EC venom inoculation. The compound also protected EC venom-induced fibrin and fibrinogen degradation. The molecular docking of compound 5d and bothropasin demonstrated the direct interaction of hydroxyl group of compound with Glu146 present in hydrophobic pocket of active site and does not chelate Zn²⁺. Hence, it is concluded that compound 5d could be a potent agent in viper bite management.

Synthesis and characterization of novel 1,2-oxazine-based small molecules that targets acetylcholinesterase

Thirteen 2-oxazine-based small molecules were synthesized targeting 5-lipoxygenase (LOX), and acetylcholinesterase (AChE). The test revealed that the newly synthesized compounds had potent inhibition towards both 5-LOX and AChE in lower micro molar concentration. Among the tested compounds, the most active compound, 2-[(2-acetyl-6,6-dimethyl-4-phenyl-5,6-dihydro-2H-1,2-oxazin-3-yl)methyl]-1H-isoindole-1,3(2H)-dione (2a) showed inhibitory activity towards 5-LOX and AChE with an IC50 values of 1.88, and 2.5 μM, respectively. Further, the in silico molecular docking studies revealed that the compound 2a bound to the catalytic domain of AChE strongly with a highest CDOCKER score of -1.18 kcal/mol when compared to other compounds of the same series. Additionally, 2a showed a good lipophilicity (logP=2.66), suggesting a potential ability to penetrate the blood-brain-barrier. These initial pharmacological data revealed that the compound 2a could serve as a drug-seed in developing anti-Alzheimer's agents.

Synthesis of pharmaceutically important condensed heterocyclic 4,6-disubstituted-1,2,4-triazolo-1,3,4-thiadiazole derivatives as antimicrobials

The two series of 4,6-disubstituted 1,2,4-triazolo-1,3,4-thiadiazole derivatives 2(a-e) and 3(a-e) were synthesized and characterized using IR, (1)H-NMR, CHNS analysis and by single crystal X-ray crystallographic studies. The compound 6-(2-chloro-phenyl)-3-ethyl-[1,2,4]triazole[3,4-b]thiadiazole 2b has been characterized by single crystal X-ray diffraction method. The compound crystallizes in monoclinic space group P2(1)/c with a cell parameters a = 11.879(1) Angstroms, b = 15.112(2) Angstroms, c = 13.95(2) Angstroms, Z = 8 and the final R factor is R1= 0.0524. The structure exhibits both intra and intermolecular hydrogen bonds. The title compounds were checked for their efficacy as antimicrobials in vitro. Compounds 2b, 2c, 2d, 3b, 3c and 3d showed significant inhibition against all the strains tested, when compared to standard drugs.

Synthesis and microbial inhibition study of novel 5-imidazolyl substituted isoxazolidines

Cycloaddition of C-imidazolyl-N-phenylnitrones with monosubstituted alkenes afforded 5-imidazolyl substituted isoxazolidines with high regioselectivity. Novel isoxazolidines were screened for their antibacterial activities against S. aureus, E. coli and B. subtilis by using streptomycin as a positive control. They were also tested for their antifungal activities against F. moniliforme, A. niger and C. acremonium by using nystatin as a positive control. Isoxazolidines, 4a and 4f exhibited more potent inhibition towards antifungal activity than the other isoxazolidines prepared.