Novel Benzotriazole-ß-lactam Derivatives as Antimalarial Agents: Design, Synthesis, Biological Evaluation and Molecular Docking Studies.

Many people around the world suffer from malaria, especially in tropical or subtropical regions. While malaria medications have shown success in treating malaria, there is still a problem with resistance to these drugs. Herein, we designed and synthesized some structurally novel benzotriazole-ß-lactams using 2-(1H-benzo[d][1,2,3]triazol-1-yl)acetic acid as a key intermediate. To synthesize the target molecules, the ketene-imine cycloaddition reaction was employed. First, The reaction of 1H-benzo[d][1,2,3]triazole with 2-bromoacetic acid in aqueous sodium hydroxide yielded 2-(1H-benzo[d][1,2,3]triazol-1-yl)acetic acid. Then, the treatment of 2-(1H-benzo[d][1,2,3]triazol-1-yl)acetic acid with tosyl chloride, triethyl amine, and Schiff base provided new ß-lactams in good to moderate yields.The formation of all cycloadducts was confirmed by elemental analysis, FT-IR, NMR and mass spectral data. Moreover, X-ray crystallography was used to determine the relative stereochemistry of 4a compound. The in vitro antimalarial activity test was conducted for each compound against P. falciparum K1. The IC50 values ranged from 5.56 to 25.65 µM. A cytotoxicity profile of the compounds at 200 µM final concentration revealed suitable selectivity of the compounds for malaria treatment. Furthermore, the docking study was carried out for each compound into the P. falciparum dihydrofolate reductase enzyme (PfDHFR) binding site to analyze their possible binding orientation in the active site.

Investigations of antiproliferative and antioxidant activity of ß-lactam morpholino-1,3,5-triazine hybrids.

This article reports for the first time the synthesis of some novel ß-lactam morpholino-1,3,5-triazine hybrids by a [2+2]-cycloaddition reaction of imines 7a-c, 9a-c and 11 with ketenes derived from substituted acetic acids. The reaction was totally diastereoselective, leading exclusively to the formation of cis-ß-lactams 8a-l, 10a-f and 12a-c. The synthesized compounds were tested for activity towards SW1116, MCF-7 and HepG2 cancer cell lines and non-cancerous HEK-293 cell line by MTT assay. None of the compounds exert an observable effect on HepG2, MCF-7 and HEK-293 cells, but compounds 7b, 8f, 8g, 8l, 10c, and 10e exhibited excellent growth inhibitory activity (IC50 < 5 µM) against SW 1116 cells, comparable to that of doxorubicin (IC50 = 6.9 µM). An evaluation of the antioxidant potential of each of the compounds, performed by diphenylpicrylhydrazyl (DPPH) assay, indicated that 7b, 9a, 9b and 9c have strong free radical scavenging activity. UV absorption titration studies reveal that 7b, 8l, 8g and 8f interact strongly with calf-thymus DNA (CT-DNA) in the order of 8l > 7b > 8f > 8g. Collectively, the in vitro capabilities of some of these morpholino-triazine imines and ß-lactams suggest possible applications to development of new antioxidants and DNA binding therapeutics.

Synthesis, docking and evaluation of in vitro anti-inflammatory activity of novel morpholine capped ß-lactam derivatives.

This study reports the synthesis and biological investigation of three series of novel monocyclic ß-lactam derivatives bearing a morpholine ring substituent on the nitrogen. The resulting ß-lactam adducts were synthesized via Staudinger's [2 + 2]-ketene-imine cycloaddition reaction. New synthesized products were fully characterized by spectral data and elemental analyses, and then evaluated for anti-inflammatory activity toward human inducible nitric oxide synthase (iNOS) and cytotoxicity toward HepG2 cell line. The compounds 3e, 3h, 3k, 5c, 5f, 6c, 6d and 6f showed higher activity with anti-inflammatory ratio values of 38, 62, 51, 72, 51, 35, 55 and 99, respectively, in comparison to the reference compound dexamethasone having an anti-inflammatory ratio value of 32. Hence, these compounds can be considered as potent iNOS inhibitors. They also exhibited IC50 values of 0.48 ± 0.04 mM, 0.51 ± 0.01 mM, 0.22 ± 0.02 mM, 0.12 ± 0.00 mM, 0.25 ± 0.05 mM, 0.82 ± 0.07 mM, 0.44 ± 0.04 mM and 0.60 ± 0.04 mM, respectively, in comparison with doxorubicin (IC50 < 0.01 mM) against HepG2 cells, biocompatibility and nontoxic behavior. In silico prediction of drug-likeness characteristic indicated that the compounds are compliant with the Lipinski and Veber rules. Molecular docking experiments showed a good correlation between the experimental activity and the calculated binding affinity to human inducible nitric oxide synthase, the enzymatic target for the anti-inflammatory response.

Recent advances in ß-lactam synthesis.

During the past century, ß-lactams have been identified as the core of penicillin and since then several strategies have been developed for their synthesis. Traditional methods for ß-lactam synthesis usually involved amide bond formation and the Staudinger reaction. In recent years, by the advancement of photo- and transition metal-catalysis, several new methods have been reported for ß-lactam synthesis. For instance: ligand assisted metal catalyzed C-H activation/intermolecular oxidative amidation draws attention for ß-lactam synthesis. In this review we introduce methods for ß-lactam synthesis and present newly developed reactions. We approach the synthesis of ß-lactams according to different retro synthesis strategies.

Crystal structure of (E)-N-(3,4-di-meth-oxy-benzyl-idene)morpholin-4-amine.

In the title compound, C13H18N2O3, the benzene ring makes a dihedral angle of 17.19 (11)° with the least-squares plane formed by the four C atoms of the morpholine ring, which adopts a chair conformation. In the crystal, C-H⋯N hydrogen bonds link the mol-ecules into supramolecular chains running along a 21 screw axis parallel to the b-axis direction. Weak C-H⋯π inter-actions are also observed.

1-[3-(Morpholin-4-yl)prop-yl]-3-[(naph-tha-len-2-yl)oxy]-4-(3-nitro-phen-yl)azeti-din-2-one.

In the title compound, C26H27N3O5, the ß-lactam (azetidin-2-one) ring is nearly planar [maximum deviation = 0.011 (3) Å]. The mean plane formed by the four C atoms of the morpholine ring, which adopts a chair conformation, the benzene ring and the naphthalene ring system form dihedral angles of 72.85 (17), 87.46 (15) and 65.96 (11)°, respectively, with the ß-lactam ring. In the crystal, molecules are linked via C-H⋯O hydrogen bonds, forming inversion dimers with R 2 (2)(8).

3-(2,4-Di-chloro-phen-oxy)-1-(4-meth-oxy-benz-yl)-4-(4-nitro-phen-yl)azetidin-2-one.

The ß-lactam ring of the title compound, C23H18Cl2N2O5, is nearly planar [maximum deviation = 0.019 (2) Šfor the N atom] and its mean plane makes dihedral angles of 56.86 (15), 68.83 (15) and 83.75 (15)° with the di-chloro-, nitro- and meth-oxy-substituted benzene rings, respectively. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, forming inversion dimers with R 2 (2)(10) loops. The dimers are linked by further C-H⋯O hydrogen bonds, forming sheets lying parallel to (001). The mol-ecular packing is further stabilized by C-H⋯π inter-actions.

Crystal structure of (E)-1(anthracen-9-ylmethylidene)[2-(morpholin-4-yl)eth-yl]amine.

The title compound, C21H22N2O, crystallizes with two independent mol-ecules in the asymmetric unit. In both mol-ecules, the anthracene ring systems are almost planar, with maximum deviations of 0.071 (8) and 0.028 (7) Å, and make dihedral angles of 73.4 (2) and 73.3 (2)° with the least-squares planes formed by the four C atoms of the morpholine rings, which adopt a chair conformation. An intra-molecular C-H⋯π inter-action occurs. In the crystal, the packing is stabilized by weak C-H⋯O hydrogen bonds, which connect pairs of molecules into parallel to the c axis, and C-H⋯π inter-actions.

(E)-Benz-yl(4-{[1-(prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]meth-oxy}benzyl-idene)amine.

The triazole ring of the title compound, C20H20N4O, is normal to the central benzene ring, making a dihedral angle of 90.0 (3)°, and forms a dihedral angle of 69.2 (3)° with the terminal phenyl ring. The dihedral angle between the phenyl and benzene rings is 88.2 (3)°. The atoms of the terminal propenyl group are disordered over two sets of sites, with a site-occupancy ratio of 0.663 (13):0.337 (13). In the crystal, C-H⋯N contacts lead to the formation of a layer structure extending parallel to (011). Two weak C-H⋯π inter-actions are also observed.

(E)-N-(4-{[1-(Prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]meth-oxy}benzyl-idene)morpholin-4-amine.

The asymmetric unit of the title compound, C17H21N5O2, contains two crystallographically independent mol-ecules, which are linked by a C-H⋯N hydrogen bond. The morpholine rings of both mol-ecules adopt distorted chair conformations. The dihedral angles between the triazole and benzene rings are 12.8 (3)° in the first independent molecule in which the -N=C- group between the morpholine and benzene rings is disordered [site-occupancy ratio = 0.576 (7):0.424 (7)] and 88.1 (2)° in the second independent mol-ecule. In the crystal, mol-ecules are linked by C-H⋯N hydrogen bonds along the [100] direction. In addition, one weak C-H⋯π inter-action and two weak π-π stacking inter-actions [centroid-centroid distances = 3.840 (3) and 3.823 (2) Å] between the triazole rings of adjacent mol-ecules are observed. The atoms of the terminal propenyl groups in both mol-ecules are disordered over two sets of sites [site-occupancy ratios = 0.691 (10):0.309 (10) and 0.705 (15):0.295 (15)].

1-[3-(Morpholin-4-yl)prop-yl]-4-(3-nitro-phen-yl)spiro-[azetidine-3,9'-xanthen]-2-one.

The ß-lactam (azetidin-2-one) ring of the title compound, C28H27N3O5, is nearly planar [maximum deviation = 0.010 (1) Å] and makes dihedral angles of 75.77 (5), 52.78 (9) and 88.72 (5)°, respectively, with the benzene ring, the least-squares plane formed by the four C atoms of the morpholine ring, which adopts a chair conformation, and the xanthene ring system. In the crystal, C-H⋯O hydrogen-bond contacts connect neighbouring mol-ecules into infinite zigzag chains running parallel to the b axis.

1-(Morpholin-4-yl)-4-(2-nitro-phen-yl)spiro-[azetidine-3,9'-xanthen]-2-one.

In the title compound, C22H21N3O5, the ß-lactam (azetidin-2-one) ring is nearly planar [maximum deviation = 0.010 (1) Å] and makes dihedral angles of 69.22 (5), 55.32 (5) and 89.42 (4)° with the least-squares planes formed by the four C atoms of the morpholine ring, which adopts a chair conformation, the benzene ring and the xanthene ring system, respectively. In the crystal, C-H⋯O hydrogen-bond contacts connect neighbouring mol-ecules into infinite zigzag chains running parallel to the b axis.

(E)-4-{[(Morpholin-4-yl)imino]-meth-yl}benzo-nitrile.

In the title compound, C12H13N3O, the morpholine ring adopts a chair conformation and its mean plane is inclined to that of the benzene ring by 16.78 (12)°. The N-N=C-C bridge, which has an E conformation, has a torsion angle of 173.80 (19)°. In the crystal, mol-ecules stack along the a axis but there are no significant inter-molecular inter-actions present.

Crystal structure of {(E)-4-[(1-allyl-1H-1,2,3-triazol-4-yl)meth-oxy]benzyl-idene}[2-(morpholin-4-yl)eth-yl]amine.

In the title compound, C19H25N5O2, the morpholine ring has a chair conformation. The plane of the central benzene ring makes dihedral angles of 88.75 (12) and 60.02 (7)°, respectively, with the mean plane formed by the four planar C atoms of the morpholine ring and with the plane of the triazole ring. In the crystal, mol-ecules are linked via C-H⋯π inter-actions, forming slabs lying parallel to (10-1). The C atoms of the bridging ethyl-ene group, between the morpholine and benzene rings, and the terminal ethene group of the prop-1-ene substituent attached to the triazole ring, are disordered over two sets of sites, with an occupancy ratio of 0.634 (13):0.366 (13).

2-(3,5-Dioxo-4-aza-tri-cyclo-[5.2.1.0(2,6)]dec-8-en-4-yl)acetic acid.

The asymmetric unit of the title compound, C11H11NO4, contains two mol-ecules, A and B, with different conformations: in mol-ecule A, the norborne and carb-oxy-lic acid groups lie to the same side of the heterocycle, whereas in a mol-ecule B, they lie on opposite sides. In the crystal, the A mol-ecules form R 2 (2)(8) carb-oxy-lic acid inversion dimers, linked by pairs of O-H⋯O hydrogen bonds. The B mol-ecules link to one of the ketone O atoms of the A mol-ecule by an O-H⋯O inter-action, resulting in tetra-mers (two A and two B mol-ecules). The tetra-mers are linked by weak C-H⋯O inter-actions, generating a three-dimensional network.

4-(1-Methyl-eth-yl)-N-((E)-4-{[1-(prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]meth-oxy}benzyl-idene)aniline.

In the title compound, C(22)H(24)N(4)O, the terminal and central benzene rings make dihedral angles of 52.7 (3) and 43.8 (2)°, respectively, with the triazole ring. The dihedral angle between the benzene rings is 8.9 (2)°. The crystal structure features C-H⋯π inter-actions. The atoms of the terminal propenyl group are disordered over two sets of sites, with a refined occupancy ratio of 0.714 (14):0.286 (14).

2-[(E)-(Morpholin-4-yl-imino)-meth-yl]-6-(morpholin-4-ylmeth-yl)phenol.

The title compound, C16H23N3O3, contains two morpholine rings, each of which adopts a chair conformation. The mol-ecular conformation is stabilized by an intra-molecular O-H⋯N hydrogen bond, leading to a S(6) ring. In the crystal, mol-ecules are linked into zigzag chains along the c-axis direction by C-H⋯O and C-H⋯π inter-actions.

(E)-N-(1,3-Benzodioxol-5-yl)-1-(4-{[1-(prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]meth-oxy}phen-yl)methanimine.

In the title compound, C20H18N4O3, the dihedral angles between the central benzene ring and the 1H-1,2,3-triazole ring and the fused benzene ring are 65.34 (19) and 3.64 (18)°, respectively. The dioxole ring adopts a shallow envelope conformation, with the methyl-ene C atom displaced by 0.156 (5) Šfrom the other four atoms (r.m.s. deviation = 0.007Å). In the crystal, the mol-ecules are linked by C-H⋯O and C-H⋯N hydrogen bonds, generating a three-dimensional network.

3,4-Dimeth-oxy-N-((E)-4-{[1-(prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]meth-oxy}benzyl-idene)aniline.

In the title compound, C(21)H(22)N(4)O(3), the triazole ring is planar [maximum deviaton = 0.004 (1) Å] and makes dihedral angles of 26.21 (8) and 38.66 (8)° with the two benzene rings. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming zigzag chains along [1-11]. In addition, a weak C-H⋯π intreraction is also observed.

1-(4-Meth-oxy-phen-yl)-4-(3-nitro-phen-yl)-3-phen-oxy-azetidin-2-one.

In the title compound, C(22)H(18)N(2)O(5), the four-membered ß-lactam ring is nearly planar, with a maximum deviation of 0.023 (2) Šfor the N atom, and has long C-C distances of 1.525 (5) and 1.571 (5) Å. The mean plane of this group makes dihedral angles of 11.61 (19), 74.5 (2) and 72.3 (2)° with three aromatic rings. An intra-molecular C-H⋯O hydrogen bond occurs. The packing of the mol-ecules in the crystal structure is governed mainly by inter-molecular C-H⋯O hydrogen-bonding and C-H⋯π stacking inter-actions. Furthermore, a π-π inter-action [centroid-centroid distance = 3.6129 (19) Å] helps to stabilize the crystal structure.