Design, synthesis, In-vitro, In-silico and DFT studies of novel functionalized isoxazoles as antibacterial and antioxidant agents.

A series of new isoxazolederivatives incorporating the sulfonate ester function has been synthesized from 2-benzylidenebenzofuran-3(2 H)-one, known as aurone. The synthesis of the target compounds was carried out following an efficient methodology that allows access to the desired products in a reproducible way and with good yield. The structures of the synthesized compounds were established using NMR (1H and 13C) spectroscopy and mass spectrometry. A theoretical study was performed to optimize the geometrical structures and to calculate the structural and electronic parameters of the synthesized compounds. The calculations were also carried out to understand the influence and the effect of substitutions on the chemical reactivity of the studied compounds. The synthesized isoxazoles were screened for their antioxidant and antibacterial activities. The findings demonstrate that the studied compounds exhibit good to moderate antibacterial activity against the tested bacteria (Staphylococcus aureus, Bacillus subtilis, and Escherichia coli). Moreover, a number of the tested isoxazole derivatives exhibit high effectiveness against DPPH free radicals. Besides that, molecular docking studies were carried out to predict binding affinity and identify the most likely binding interactions between the active molecules and the target microorganisms' proteins. A 100 ns molecular dynamics study was then conducted to examine the dynamic behavior and stability of the highly potent isoxazole 4e in complex with the target bacterial proteins. Finally, the ADMET analyses suggest that all the synthesized isoxazoles have good pharmacokinetic profiles and non-toxicity and non-carcinogenicity in biological systems.

Synthesis, Characterization, DFT Mechanistic Study, Antimicrobial Activity, Molecular Modeling, and ADMET Properties of Novel Pyrazole-isoxazoline Hybrids.

A series of new heterocycle hybrids incorporating pyrazole and isoxazoline rings was successfully synthesized, characterized, and evaluated for their antimicrobial responses. The synthesized compounds were obtained utilizing N-alkylation and 1,3-dipolar cycloaddition reactions, as well as their structures were established through spectroscopic methods and confirmed by mass spectrometry. To get more light on the regioselective synthesis of new hybrid compounds, mechanistic studies were performed using DFT calculations with B3LYP/6-31G(d,p) basis set. Additionally, the results of the preliminary screening indicate that some of the examined hybrids showed potent antimicrobial activity, compared to standard drugs. The results confirm that the antimicrobial activity is strongly dependent on the nature of the substituents linked pyrazole and isoxazoline rings. Furthermore, molecular docking studies were conducted to highlight the interaction modes between the investigated hybrid compounds and the Escherichia coli and Candida albicans receptors. Notably, the results demonstrate that the investigated compounds have strong protein binding affinities. The stability of the formed complexes by the binding between the hybrid compound 6c, and the target proteins was also confirmed using a 100 ns molecular dynamics simulation. Finally, the prediction of ADMET properties suggests that almost all hybrid compounds possess good pharmacokinetic profiles and no signs of observed toxicity, except for compounds 6e, 6f, and 6g.

Crystal structure of 3,4'-diphenyl-3'-p-tolyl-4'H-spiro-[indan-2,5'-[1,2]oxazol]-1-one.

In the title compound, C30H23NO2, the five-membered rings are both in envelope conformations with the same spiro C atom as the flap. The benzene ring and the two phenyl rings are inclined to the mean plane of the indene ring system by 83.98 (8), 81.46 (8) and 72.31 (7)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds into inversion dimers. The dimers are further connected by C-H⋯N inter-actions, forming layers parallel to (10-1).

Crystal structure of ethyl 2-amino-4-(4-chloro-phen-yl)-4H-1-benzothieno[3,2-b]pyran-3-carboxyl-ate.

The title compound, C20H16ClNO3S, is built up from three fused rings, one five- and two six-membered rings, linked to a 3-eth-oxy-carbonyl group and to a 4-chloro-phenyl ring. The hydropyran ring has a flattened envelope conformation, with the C atom substituted by the 4-chloro-phenyl ring as the flap (displaced by 0.077 (2) Šfrom the plane through the other atoms). The fused three-ring system is quasi-planar (r.m.s. deviation = 0.057 Å), with the largest deviation from the mean plane being 0.106 (1) Šfor the C atom substituted by the 4-chloro-phenyl ring. The 4-chloro-phenyl ring is approximately perpendicular to the mean plane of the fused ring system, as indicated by the dihedral angle of 77.32 (6)° between their mean planes. There is an intra-molecular N-H⋯O hydrogen bond forming an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(12) ring motif. There are also short inter-molecular Cl⋯O inter-actions present [3.1226 (12) Å] between neighbouring mol-ecules.

Crystal structure of (E)-4-ethyl-2-(4-meth-oxy-benzyl-idene)-3,4-di-hydro-naphthalen-1(2H)-one.

In the title compound, C20H20O2, the exocyclic C=C double bond has an E conformation. The ethyl substituent on the cyclo-hexa-none ring is in an axial orientation. The cyclo-hexa-none ring adopts a screw-boat conformation, with the methyl-ene C atom and the C atom bearing the 4-meth-oxy-benzyl-idene group displaced from the other atoms by 0.812 (1) and 0.334 (1) Å, respectively. The dihedral angle between the planes of the benzene rings is 42.20 (8)°. In the crystal, no directional inter-actions beyond van der Waals contacts are observed.

Crystal structure of ethyl 2-amino-4-(4-meth-oxy-phen-yl)-4H-1-benzothieno[3,2-b]pyran-3-carboxyl-ate.

The mol-ecule of the title compound, C21H19NO4S, features a fused ring system whereby a five-membered ring is flanked by two six-membered rings. This is linked to an ethyl 3-carboxyl-ate group and to a meth-oxy-benzene group. The fused-ring system is quasi-planar, with the greatest deviation from the mean plane being 0.131 (1) Šfor the methine C atom. The plane through the meth-oxy-benzene ring is nearly perpendicular to that through the fused-ring system, as indicated by the dihedral angle of 85.72 (6)°. An intra-molecular N-H⋯O hydrogen bond is noted. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming layers that stack along the a axis.

Crystal structure of 2-amino-3-cyano-4-(4-meth-oxy-phen-yl)-4H-1-benzo-thieno[3,2-b]pyran.

The three fused five- and six-membered rings in the title compound, C19H14N2O2S, are virtually coplanar, with the maximum deviation from the mean plane being 0.060 (1) Å. This benzothieno[3,2-b]pyran ring system is nearly perpendic-ular to the plane of the 4-meth-oxy-phenyl ring, forming a dihedral angle of 83.65 (5)°. In the crystal, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds into inversion dimers. The dimeric units are further connected by an N-H⋯O hydrogen bond into a tape running along the b axis. The tapes are linked together by C-H⋯N and π-π inter-actions [centroid-centroid distance = 3.7743 (8) Å], forming a three-dimensional network.

Crystal structure of 4-(4-meth-oxy-phen-yl)-4',4'-dimethyl-3-p-tolyl-3',4'-di-hydro-1'H,3H-spiro-[isoxazole-5,2'-naphthalen]-1'-one.

In the title compound, C28H27NO3, the cyclo-hexa-none and isoxazole rings have envelope conformations, with the methyl-ene and spiro C atoms as the flaps, respectively. The mean plane of the isoxazole ring is inclined slightly to the p-tolyl ring, making a dihedral angle of 14.20 (9)°, and is nearly perpendicular to the mean plane through the tetra-lone moiety and to the meth-oxy-phenyl ring [dihedral angles = 83.41 (8) and 72.12 (9)°, respectively]. The crystal packing is stabilized mainly by van der Waals forces.

Ethyl 2-amino-4-(3-nitro-phen-yl)-4H-1-benzothieno[3,2-b]pyran-3-carboxyl-ate.

The mol-ecule of the title compound, C20H16N2O5S, is built up by one fused five-membered and two fused six-membered rings linked to eth-oxy-carbonyl and 3-nitro-phenyl groups. The benzothieno-pyran ring system is nearly planar (r.m.s deviation = 0.0392 Å) and forms a dihedral angle of 86.90 (6)° with the aromatic ring of the nitro-benzene group. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds and by π-π inter-actions between the phenyl ring and the six-membered heterocyle [inter-centroid distance = 3.5819 (8) Å], forming a three-dimensional network.

(2RS,4'RS)-3'-(3-Chloro-4-meth-oxy-phen-yl)-4'-phenyl-4'H-spiro-[indene-2,5'-isoxazol]-1(3H)-one ethanol monosolvate.

The title compound, C(23)H(17)ClN(2)O(3)·C(2)H(6)O, is the stoichiometric 1:1 ethanol solvate of a racemic reaction product, which forms a conglomerate. The refined Flack parameter of 0.36 (3) indicates racemic twinning. In the structure, mol-ecules are linked into zigzag chains by a series of inter-molecular N-H⋯O and O-H⋯O hydrogen bonds.

Ethyl 2-amino-4-phenyl-4H-1-benzo-thieno[3,2-b]pyran-3-carboxyl-ate.

The title heterocyclic compound, C(20)H(17)NO(3)S, was synthesized by condensation of ethyl cyano-acetate with (Z)-2-benzyl-idenebenzo[b]thio-phen-3(2H)-one in the presence of a basic catalyst in ethanol. The phenyl and ester groups make dihedral angles of 77.67 (6) and 8.52 (6)°, respectively, with the benzothienopyran ring system [maximum r.m.s. deviation = 0.1177 (13) Å]. In the crystal, centrosymmetric dimers are formed through pairs of N-H⋯O hydrogen bonds between the amine and ester groups. Inter-molecular C-H⋯N hydrogen bonds and C-H⋯π inter-actions involving the thio-phene ring are also observed.

3'-(4-Meth-oxy-phen-yl)-4'-phenyl-3H,4'H-spiro-[1-benzothio-phene-2,5'-isoxazol]-3-one.

In the title compound, C(23)H(17)NO(3)S, the thio-phene and isoxazole rings each have an envelope conformation with the spiro C atom linking them forming the flap of the envelope in each case. The dihedral angle between the mean planes of the benzothio-phene ring and isoxazole rings is 81.35 (7)°. In the crystal, an inter-molecular C-H⋯O hydrogen bond links the mol-ecules into a chain running parallel to the a axis.

Structure-activity relationship analysis of novel derivatives of narciclasine (an Amaryllidaceae isocarbostyril derivative) as potential anticancer agents.

Narciclasine (1) is a plant growth regulator that has been previously demonstrated to be proapoptotic to cancer cells at high concentrations (> or = 1 microM). Data generated in the present study show that narciclasine displays potent antitumor effects in apoptosis-resistant as well as in apoptosis-sensitive cancer cells by impairing the organization of the actin cytoskeleton in cancer cells at concentrations that are not cytotoxic (IC(50) values of 30-90 nM). The current study further revealed that any chemical modification to the narciclasine backbone generally led to compounds of variable stability, weaker activity, or even the complete loss of antiproliferative effects in vitro. However, one hemisynthetic derivative of narciclasine, compound 7k, demonstrated by both the intravenous and oral routes higher in vivo antitumor activity in human orthotopic glioma models in mice when compared to narciclasine at nontoxic doses. Narciclasine and compound 7k may therefore be of potential use to combat brain tumors.

2,2,2-Trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin- 5-yl}carbamoyl)acetamide (UNBS3157), a novel nonhematotoxic naphthalimide derivative with potent antitumor activity.

Amonafide (1), a naphthalimide which binds to DNA by intercalation and poisons topoisomerase IIalpha, has demonstrated activity in phase II breast cancer trials, but has failed thus far to enter clinical phase III because of dose-limiting bone marrow toxicity. Compound 17 (one of 41 new compounds synthesized) is a novel anticancer naphthalimide with a distinct mechanism of action, notably inducing autophagy and senescence in cancer cells. Compound 17 (2,2,2-trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-5-yl}carbamoyl)acetamide (UNBS3157)) was found to have a 3-4-fold higher maximum tolerated dose compared to amonafide and not to provoke hematotoxicity in mice at doses that display significant antitumor effects. Furthermore, 17 has shown itself to be superior to amonafide in vivo in models of (i) L1210 murine leukemia, (ii) MXT-HI murine mammary adenocarcinoma, and (iii) orthotopic models of human A549 NSCLC and BxPC3 pancreatic cancer. Compound 17, therefore, merits further investigation as a potential anticancer agent.

Identification of a novel cardenolide (2''-oxovoruscharin) from Calotropis procera and the hemisynthesis of novel derivatives displaying potent in vitro antitumor activities and high in vivo tolerance: structure-activity relationship analyses.

Analysis of the methanolic extract of Calotropis procera root barks enabled the identification of a novel cardenolide (2''-oxovoruscharin) to be made. Of the 27 compounds that we hemisynthesized, one (23) exhibited a very interesting profile with respect to its hemisynthetic chemical yield, its in vitro antitumor activity, its in vitro inhibitory influence on the Na+/K+-ATPase activity, and its in vivo tolerance. Compound 23 displayed in vitro antitumor activity on a panel of 57 human cancer cell lines similar to taxol, and higher than SN-38 (the active metabolite of irinotecan), two of the most potent drugs used in hospitals to combat cancer.