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.

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.

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.

Diastereoselective Synthesis of Potent Antimalarial Cis-ß-lactam Agents.

Fifteen novel ß-lactams bearing N-ethyl tert-butyl carbamate group 5a-o and fifteen N-(2- aminoethyl) ß-lactams 6a-o were synthesized by [2+2] ketene-imine cycloaddition reaction (Staudinger). The cycloaddition reaction was found to be totally diastereoselective leading exclusively to theformation of cis-ß-lactam derivatives. These newly synthesized ß-lactams were evaluated for their antimalarial activity against p. falciparum K14 resistant strain and showed good to excellent EC50 values. Of the thirty ß-lactams tested, 5 h, 6a and 6c showed IC50 < 20 µM while 5b, 5c, 5e, 5f, 5g, 5i, 5j, 6d, 6g and 6h exhibited IC50 <50 . Compounds 5c, 5h, and 5q-t were examined for their anticancer properties against K562 Leukemia cell line and 5s showed the best activity. Compounds 3a-j, 5a-o, 6a-o, were tested against S. aureus , E. coli, C. albicans and showed no activity below 125 µg/mL.

Three-component synthesis of chromeno ß-lactam hybrids for inflammation and cancer screening.

Highly diastereoselective synthesis of chromeno ß-lactam hybrids was achieved by an efficient one-pot three-component reaction. With this procedure, the desired ß-lactam products were obtained in good yields and with exclusive cis stereoselection, by combining a variety of benzaldehydes, malononitrile, and either 5,5-dimethylcyclohexane-1,3-dione or 4-hydroxycoumarin in the presence of 1,4-diazabicyclo [2.2.2]octane under reflux conditions. These adducts were structurally characterized on the basis of IR, 1D and 2D NMR spectra, X-ray analysis, H-H COSY and H-C HSQC two-dimensional NMR experiments, and elemental analysis. Each of the synthesized compounds was screened for anti-inflammatory and anticancer activities. ß-Lactams 5b and 8b showed a 53.4 and 19.8 anti-inflammatory ratio, respectively, and 5b appeared more active than the well-known dexamethasone corticosteroid used for the treatment of rheumatoid and skin inflammation. ß-Lactams 5a, 5b, 5e, 5f, 5g, 8c, 8j and 8p also showed good antitumor activity against the SW1116 (colon cancer) cell line without notable cytotoxicity towards the HepG2 control cell line.

Synthesis of New ß-Lactams Bearing the Biologically Important Morpholine Ring and POM Analyses of Their Antimicrobial and Antimalarial Activities.

Some new ß-lactams bearing biologically important morpholine ring have been synthesized by acylation of amino ß-lactams in the presence of morpholine-4-carbonyl chloride. These novel ß-lactams were prepared under mild reaction conditions without any solvent in short reaction times. Their biological activities have been examined against microbial agents such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and fungi such as Candida albicans (C. albicans) and Candida glabrata (C. glabrata). They have been also tested against Plasmodium falciparum K14 resistant strain and showed moderate to good IC50 values.

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.

Synthesis and biological evaluation of some novel diastereoselective benzothiazole ß-lactam conjugates.

Highly diastereoselective synthesis of some novel benzothiazole-substituted ß-lactam hybrids was achieved starting from (benzo[d]thiazol-2-yl)phenol as an available precursor. This is the first time (benzo[d]thiazol-2-yl)phenoxyacetic acid has been used as ketene source in synthesizing monocyclic 2-azetidinones. These compounds were evaluated for their antimicrobial activities against a large panel of Gram-positive and Gram-negative bacterial strains and moderate activities were encountered. Antimalarial data revealed that adding methoxyphenyl or ethoxyphenyl group on the ß-lactam ring makes compounds that are more potent. Moreover, hemolytic activity and mammalian cell toxicity survey of the compounds showed their potential as a medicine.

Crystal structure of 4-[(E)-(4-nitro-benzyl-idene)amino]-phenol.

The asymmetric unit of the title compound, C13H10N2O3, contains four independent mol-ecules (I, II, III and IV). Mol-ecule IV shows whole-mol-ecule disorder over two sets of adjacent sites in a 0.669 (10):0.331 (10) ratio. The dihedral angles between the aromatic rings are 32.30 (13)° in mol-ecule I, 2.24 (14)° in II, 41.61 (13)° in III, 5.0 (5)° in IV (major component) and 10.2 (3)° in IV (minor component). In the crystal, mol-ecules are linked into layers lying parallel to (024) by C-H⋯O and O-H⋯O inter-actions. The layers inter-act by C-H⋯π and weak aromatic π-π stacking inter-actions [centroid-centroid distances = 3.8476 (16), 3.725 (3) and 3.733 (5) Å].

Crystal structure of 2-[4-(4-chloro-phen-yl)-1-(4-meth-oxy-phen-yl)-2-oxoazetidin-3-yl]benzo[de]iso-quinoline-1,3-dione dimethyl sulfoxide monosolvate.

In the title solvated compound, C28H19N2O4·C2H6OS, the central ß-lactam ring is almost planar (r.m.s. deviation = 0.002 Å). It makes dihedral angles of 1.92 (11), 83.23 (12) and 74.90 (10)° with the meth-oxy- and chloro-phenyl rings and the ring plane of the 1H-benzo[de]iso-quinoline-1,3(2H)-dione group [maximum deviation = 0.089 (1)], respectively. An intra-molecular C-H⋯O hydrogen bond closes an S(6) ring and helps to establish the near coplanarity of the ß-lactam and meth-oxy-benzene rings. In the crystal, the components are linked by C-H⋯O hydrogen bonds, C-H⋯π inter-actions and aromatic π-π stacking inter-actions [centroid-to-centroid distances = 3.6166 (10) and 3.7159 (10) Å], resulting in a three-dimensional network, The dimethyl sulfoxide solvent mol-ecule is disordered over two sets of sites in a 0.847 (2):0.153 (2) ratio.

Crystal structure of 2-[(3S,4S)-4-(anthracen-9-yl)-1-(4-meth-oxy-phen-yl)-2-oxoazetidin-3-yl]-2-aza-2H-phenalene-1,3-dione unknown solvate.

The central ß-lactam ring of the title compound, C36H24N2O4, is almost planar (r.m.s. deviation = 0.003 Å) and makes dihedral angles of 17.17 (19), 89.76 (17) and 78.44 (17)° with the benzene ring, the anthracene ring (r.m.s. deviation = 0.003 Å) and the 1H-benzo[de]iso-quinoline-1,3(2H)-dione moiety, which is nearly planar [maximum deviation = 0.098 (2) Å], respectively. The mol-ecular structure is stabilized by an intra-molecular C-H⋯N hydrogen bond. In the crystal, mol-ecules are linked via C-H⋯π and π-π stacking inter-actions [centroid-centroid distances = 3.5270 (19) and 3.779 (2) Å], forming a three-dimensional structure. A region of disordered electron density, probably disordered solvent mol-ecules, was treated with the SQUEEZE procedure in PLATON [Spek (2015 ▶). Acta Cryst. C71, 9-18], which indicated a solvent cavity of 322 Å(3) containing approximately 91 electrons. Their formula mass and unit-cell characteristics were not taken into account during the refinement.

Crystal structure of 1-(4-meth-oxy-phen-yl)-4-(4-nitro-phen-yl)-3-phen-oxy-azetidin-2-one.

In the title compound, C22H18N2O5, the central ß-lactam ring (r.m.s. deviation = 0.002 Å) makes dihedral angles of 64.21 (14), 82.35 (12) and 20.66 (13)° with the phenyl ring and the nitro- and meth-oxy-benzene rings, respectively. The mol-ecular structure is stabilized by an intra-molecular C-H⋯O hydrogen bond. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming slabs lying parallel to (111). The slabs are linked via C-H⋯π inter-actions, forming a three-dimensional network.

Crystal structure of 3-(4-chloro-phen-oxy)-4-(2-nitro-phen-yl)azetidin-2-one with an unknown solvate.

In the title compound, C15H11ClN2O4, the central ß-lactam ring is approximately planar [maximum deviation = 0.044 (2) Šfor the N atom from the mean plane] and subtends dihedral angles of 61.17 (11) and 40.21 (12) °, respectively, with the nitro and chloro-benzene rings. Both substituents lie to the same side of the ß-lactam core. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules into C(4) chains propagating in [010]. The chains are cross-linked by C-H⋯O and weak C-H⋯π inter-actions, generating a three-dimensional network. The solvent mol-ecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155], which indicated a solvent cavity of volume 318 Å(3) containing approximately 114 electrons. These solvent mol-ecules are not considered in the given chemical formula and other crystal data.

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

The list of authors in the paper by Çelikesir et al. [Acta Cryst. (2014), E70, o935] is corrected.[This corrects the article DOI: 10.1107/S160053681401678X.].

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.

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).

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.

Diastereoselective synthesis of potent antimalarial cis-ß-lactam agents through a [2 + 2] cycloaddition of chiral imines with a chiral ketene.

The effect of double asymmetric induction for the synthesis of new cis-ß-lactams by [2 + 2] cycloaddition reactions of chiral imines with a chiral ketene was investigated. The cycloaddition reaction was found to be totally diastereoselective leading exclusively to the formation of the cis-ß-lactam derivatives. The newly synthesized cycloadducts were evaluated for their antimalarial activities against Plasmodium falciparum K14 resistant strain with moderate to excellent IC50 values varying from 8 to 50 µM. Of the fifteen ß-lactams tested, four showed IC50 ≤ 11 µM.

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.