Synthesis,crystal structures,and antibacterial studies of silver(I) complexes with reduced Schiff base amino acid ligands

Three Ag(I) complexes of reduced Schiff base amino acid ligands, [Ag₂(Hshis)₂]·3H₂O (1), Ag(Hcgly) (2), and Ag(cala) (3) (H₂shis = N-(2-hydroxybenzyl)-l-histidine, H₂cgly = N-(2-hydroxy-5-chlorobenzyl)-glycine, Hcala = N-(4-chlorobenzyl)-d,l-alanine), have been synthesized and characterized by X-ray crystallography. Complex 1 shows a dimeric structure, while complex 2 shows one-dimensional zigzag chains, which are extended into a two-dimensional supramolecular sheet by hydrogen bonds. Complex 3 exhibits a 2D sheet structure with dangling arms. The antimicrobial activities of the complexes have been investigated.     

Synthesis and in vitro anticancer,antibacterial, and antioxidant studies of unsymmetrical Schiff base derivatives of 4-[(1<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(2-aminoethyl)ethanimidoyl]benzene-1,3-diol

Schiff bases such as 2-hydroxy-1-(4-hydroxyphenyl)ethanone (DHAP) and its derivatives have attracted attention because they are useful in design and development of novel organic compounds for potential pharmaceutical applications. In this work, a series of 4-[(1E)-N-(2-aminoethyl)ethanimidoyl]benzene-1,3-diol (4a–h) Schiff bases were synthesized by reaction of ethylenediamine, DHAP, and appropriate aldehyde moieties. The compositions of the prepared compounds were established using elemental analysis and Fourier-transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopies. The compounds were screened against three Gram-positive and three Gram-negative bacteria, and the results compared with standard drugs ciprofloxacin and amoxicillin. Compounds 4g, 4h were found to have higher activity against Staphylococcus aureus with minimum inhibitory concentration (MIC) value of 2.5 mg/mL, while compounds 4f and 4h inhibited Escherichia coli with MIC values of 2.5 and 5 mg/mL, respectively. The IC₅₀ values of compounds 4a–h for scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical ranged from 2.63 ± 0.79 to 3.85 ± 0.83 µM with good correlation coefficient of R ² = 0.957–0.994. In vitro anticancer screening of the compounds showed that compounds 4f, 4h, and parthenolide efficiently affected cell viability of cancer cell line MCF-7 with IC₅₀ values of 4.10 ± 1.32, 4.01 ± 2.26, and 0.44 ± 2.02 µM, respectively.     

Concise synthesis of two natural steroidal glycosides isolated from <Emphasis Type="Italic">Allium schoenoprasum</Emphasis>

Two natural steroidal glycosides, diosgenin 3-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (1) and laxogenin 3-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (2) with important cytotoxic activity against the HCT 116 and HT-29 human colon cancer cell lines have been efficiently synthesized via straightforward sequential glycosylation reaction with the combined use of N-phenyltrifluoroacetimidates and trichloroacetimidates donors at room temperature. All structures of the synthesized new compounds were identified by ¹H NMR, ¹³C NMR and HRMS spectra.     

Amberlyst-15 catalyzed synthesis of novel thiophene–pyrazoline derivatives: spectral and crystallographic characterization and anti-inflammatory and antimicrobial evaluation

Increasing instances of antimicrobial drug resistance and Inflammation-mediated disorders requires the design and synthesis of new small-molecules with higher affinity and specificity for their potential targets to serve as antibiotics or anti-inflammatory drugs, respectively. The current study presents the synthesis of a series of chalcones, 3(a–h) by the reaction of 3-methylthiophene-2-carbaldehyde, 1 and acetophenones, 2(a–h) by Claisen–Schmidt approach. The chalcones were efficiently transformed into thienyl-pyrazolines, 5(a–h) by their reaction with thiosemicarbazide hydrochloride, 4 in the presence of Amberlyst-15 as a catalyst in acetonitrile at room temperature. Alternatively, the compounds 5(a–h) were prepared by conventional method using acetic acid (40%) medium. Structures were characterized by spectral and single crystal X-ray diffraction studies. Preliminary assessment of the anti-inflammatory properties of the compounds showed that, amongst the series, compounds 5b and 5c have excellent anti-inflammatory activities. Further, compound 5c showed excellent activity against Escherichia coli (MIC, 15 µg/mL), Bacillus subtilis (MIC, 20 µg/mL), Aspergillus niger (MIC, 20 µg/mL), and Aspergillus flavus (MIC 15 µg/mL), respectively. Compounds 5a and 5b were also found to be active against the tested microorganisms.     

Crystal structure as the basis for the lack of enantiotropic mesomorphism in 3-hydroxy-4-propionylphenyl-4′-<Emphasis Type="Italic">n</Emphasis>-alkyloxybenzoates

Features of the molecular structure and crystal packing of the mesogenic compounds 3-hydroxy-4-propionylphenyl esters of 4-n-amyloxy (1), 4-n-hexyloxy (2), 4-n-heptyloxy (3), and 4-n-octyloxybenzoic acid (4) have been analyzed on the basis of X-ray diffraction (XRD) data. Comparison of the results of XRD and DSC studies of these compounds has shown that the crystalline modification studied for each of the compounds is not a precursor to the mesophase. The possibility of mesophase formation from the melt is discussed.     

Syntheses,crystal structures and in vitro anticancer activities of oxovanadium(IV) complexes of amino acid Schiff base and 1,10-phenanthroline ligands

Four oxovanadium(IV) complexes, namely [VO(desa-met)(phen)]·MeOH·2H₂O (1) (desa-met = Schiff base derived from 4-(diethylamino)salicylaldehyde and dl-methionine, phen = 1,10-phenanthroline), [VO(o-van-met) (phen)]·MeOH·CH₂Cl₂·3H₂O (2) (o-van-met = Schiff base derived from o-vanillin and dl-methionine), [VO(dtbs-napa)(phen)]·2H₂O (3) (dtbs-napa = Schiff base derived from 3,5-di-tert-butyl salicylaldehyde and 3-(1-naphthyl)-l-alanine) and [VO(hyna-napa)(phen)]·1.5H₂O (4) (hyna-napa = Schiff base derived from 2-hydroxy-1-naphthaldehyde and 3-(1-naphthyl)-l-alanine), were synthesized and characterized by IR, HRMS, UV–vis spectra, molar conductance and single-crystal X-ray diffraction (XRD). X-ray structural analysis showed that the V(IV) atoms in all four complexes are six-coordinated in a distorted octahedral environment. In the crystals of complexes 1 and 2, π–π stacking interactions together with hydrogen bonds connect the molecular units into 2D networks. Meanwhile, CH–π stacking interactions are observed between the aromatic rings in the crystals of 1 and 4, while the π–π stacking interactions between aromatic rings in the crystals of 2 and 3 are arranged with a face-to-face mode. The in vitro anticancer activities of these complexes against A-549 and HeGp2 cells were tested by MTT assay.     

Synthesis,SAR and in vitro therapeutic potentials of thiazolidine-2,4-diones

Background

Thiazolidinedione is a pentacyclic moiety having five membered unsaturated ring system composed with carbon, oxygen, nitrogen and sulfur molecules at 1 and 3 position of the thiazole ring and widely found throughout nature in various form. They favourably alter concentration of the hormones secreted by adipocytes, particularly adiponectin. They also increase total body fat and have mixed effects on circulating lipids. Thiazolidinedione nucleus is present in numerous biological moieties and has different pharmacological activities likes, e.g. antimalarial, antimicrobial, antimycobacterial, anticonvulsant, antiviral, anticancer, anti-inflammatory, antioxidant, anti-HIV (human immunodeficiency virus) and antituberculosis.

Results and discussion

The synthesized compounds were screened for their in vitro antimicrobial potential against Gram (positive and negative) bacterial and fungal strains by tube dilution technique. In this series, compound 10 exhibited significant antimicrobial activity against B. subtilis and S. aureus with MIC?=?4.2?×?10^?2 µM/ml, compound 15 showed significant activity against K. pneumonia with MIC?=?2.60?×?10^?2 µM/ml and compound 4 displayed potent antibacterial activity against E. coli with MIC?=?4.5?×?10^?2 µM/ml. Compound 10 had most potent antifungal activity against C. albicans and A. niger with MIC?=?4.2?×?10^?2 µM/ml. Compounds 12 and 15 were found as most active antidiabetic agents having IC₅₀?=?27.63 μg/ml and 22.35 μg/ml, respectively, using DPPH assay. Antioxidant activity results indicated that compounds 3 and 9 displayed good antioxidant agent with IC₅₀?=?29.04 μg/ml and 27.66 μg/ml respectively, using α amylase assay.

Conclusion

All the synthesized derivatives exhibited good antimicrobial, antidiabetic and antioxidant activities using specific methods then compared with mentioned standard drugs. Especially, compounds 3, 4, 9, 10, 12 and 15 displayed highest activity. Structure activity relationship demonstrated that presence of electron withdrawing group (o-NO₂, p-Cl, p-Br) enhanced the antibacterial activity against E. coli as well as increased the antioxidant activity while the presence of electron releasing group (o/p-OCH₃, 3,4,5-trimethoxy) enhanced the antibacterial activity against S. aureus, B. subtilis, S. typhi, K. pneumonia, C. albicans and A. niger as well as the antidiabetic activity.

     

Synthesis,characterization, biological evaluation and molecular docking studies of 2-(1H-benzo[d]imidazol-2-ylthio)-<Emphasis Type="Italic">N</Emphasis>-(substituted 4-oxothiazolidin-3-yl) acetamides

Background

A series of 2-(1H-benzo[d]imidazol-2-ylthio)-N-(substituted 4-oxothiazolidin-3-yl) acetamides was synthesized and characterized by physicochemical and spectral means. The synthesized compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Candida albicans and Aspergillus niger by tube dilution method. The in vitro cytotoxicity study of the compounds was carried out against human colorectal (HCT116) cell line. The most promising anticancer derivatives (5l, 5k, 5i and 5p) were further docked to study their binding efficacy to the active site of the cyclin-dependent kinase-8.

Results

All the compounds possessed significant antimicrobial activity with MIC in the range of 0.007 and 0.061 µM/ml. The cytotoxicity study revealed that almost all the derivatives were potent in inhibiting the growth of HCT116 cell line in comparison to the standard drug 5-fluorouracil. Compounds 5l and 5k (IC₅₀ = 0.00005 and 0.00012 µM/ml, respectively) were highly cytotoxic towards HCT116 cell line in comparison to 5-fluorouracil (IC₅₀ = 0.00615 µM/ml) taken as standard drug.

Conclusion

The molecular docking studies of potent anticancer compounds 5l, 5k, 5i and 5p showed their putative binding mode and significant interactions with cyclin-dependent kinase-8 as prospective agents for treating colon cancer.

     

μ<Subscript>2</Subscript>-Oxobis[(aroxo)tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)antimony]: Synthesis and Structure

µ₂-Oxobis[(2,4,6-tribromophenoxo)tris(para-tolyl)antimony] (I), µ₂-oxobis[(2,3,4,5,6-pentachlorophenoxo) tris(para-tolyl)antimony] (II), and µ₂-oxobis(2,4-dinitrophenoxo)tris(para-tolyl)antimony] (III) have been synthesized with high yields by the reaction of tris(para-tolyl)antimony with 2,4,6-tribromo-, 2,3,4,5,6-pentachloro-, and 2,4-dinitrophenol, respectively, in ether in the presence of tert-butylhydroperoxide. The Sb atoms in complexes I, II, and III have a distorted trigonal bipyramidal coordination with the aroxyl ligands and the bridging oxygen atom in axial positions. The central Sb–O–Sb moiety in molecules of complexes I–III has an angular structure.     

Design,synthesis and anti-mycobacterial evaluation of some new <Emphasis Type="Italic">N</Emphasis>-phenylpyrazine-2-carboxamides

N-Phenylpyrazine-2-carboxamides (anilides of pyrazinoic acids with simple substituents in various positions) were previously shown to possess significant biological activities in vitro, markedly anti-mycobacterial and photosynthesis-inhibiting activity. Based on structure-activity relationships (SAR) extracted from previously published series, 25 new anilides of non-substituted pyrazinoic acid (POA), 5-CH₃-POA, 6-Cl-POA, 5-tert-butyl-POA and 5-tert-butyl-6-Cl-POA were designed and synthesised. The phenyl part was substituted with simple hydrophobic substituents chosen from methyl and halogens. 5-tert-Butyl-N-(5-fluoro-2-methylphenyl)pyrazine-2-carboxamide (9), N-(3-chloro-4-methylphenyl)-5-methylpyrazine-2-carboxamide (12), 6-chloro-N-(3-chloro-4-methylphenyl)pyrazine-2-carboxamide (13) and 6-chloro-N-(5-iodo-2-methylphenyl)pyrazine-2-carboxamide (18) possessed whole cell anti-mycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) of around 10 μM. Importantly, no cytotoxicity in the HepG2 model was detected in vitro at the concentrations tested and the estimated IC50 values were in hundreds of μM, indicating promising selectivity. N-(3-Chloro-4-methylphenyl)pyrazine-2-carboxamide (11) and N-(4-chloro-2-iodophenyl)pyrazine-2-carboxamide (21) exerted significant activity against Mycobacterium kansasii with MIC 12.6 μM and 8.7 μM, respectively. No activity was detected against Mycobacterium avium. SAR were in accordance with those observed for the derivatives previously published.     

Recovery of host crystals from inclusion crystals of <Emphasis Type="Italic">p-tert-</Emphasis>butylcalix[4]arene and <Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[4]arene by the treatment with a solvent and/or supercritical CO<Subscript>2</Subscript>

Upon stirring inclusion crystals of p-tert-butylthiacalix[4]arene (2) in solvents with heating, guest compounds were efficiently desorbed to yield guest-free crystals. More specifically, upon treatment with methanol, the exchange of guest compounds with methanol in the crystals, followed by the desorption of the methanol afforded metastable host crystals 2β, whereas, upon treatment with heptane, the dissolution of the inclusion crystals and simultaneous crystallization of compound 2 afforded stable host crystals 2α. Further, a host crystal of p-tert-butylcalix[4]arene (1) was recovered by the treatment of 2:1 (host/guest) inclusion crystals of compound 1 with supercritical carbon dioxide (scCO₂), and through the combination of the guest exchange of 1:1 inclusion crystals of compound 1 with hexane and scCO₂ treatment of the resulting 2:1 inclusion crystals 1₂·hexane. Although the recovered host crystal of compound 1 contained a small amount of CO₂, it could be reused for the inclusion of organic compounds.     

Hyperconjugative interactions are the main responsible for the anomeric effect: a direct relationship between the hyperconjugative anomeric effect,global hardness and zero-point energy

The correlations between the global hardness (η), hyperconjugative anomeric effect, Pauli exchange-type repulsions, electrostatic model associated with dipole–dipole interaction and structural parameters in 2-fluorotetrahydropyran, -thiopyran, -selenopyran (1–3) and their chloro- (4–6) and bromo-analogs (7–9) were investigated by means of the conventional and range-corrected functionals and natural bond orbital (NBO) interpretation. By deletion of the HC-exo-AE and HC-endo-AE, the equatorial conformations of compounds 1–9 become more stable than their corresponding axial forms, revealing that anomeric relationships in compounds 1–9 have the hyperconjugative anomeric effect origins while the electrostatic model associated with dipole–dipole interaction does not play a determining role on the variations of the anomeric relationships in these compounds. The anomeric relationships in compounds 1–3 have no Pauli exchange-type repulsions origin, but it has a significant impact on the conformational preferences in compounds 4–6 and 7–9. A canonical molecular orbital interpretation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the global hardness (η) values. There is a direct relationship between the hyperconjugative anomeric effect, global hardness (η) and zero-point energies in compounds 1–3, 4–6 and 7–9. The harder axial conformations with the greater hyperconjugative anomeric effect and zero-point energy values are more stable than their corresponding equatorial forms.     

Phosphorus–nitrogen compounds part 33: in vitro cytotoxic and antimicrobial activities,DNA interactions,syntheses, and structural investigations of new mono(4-nitrobenzyl)spirocyclotriphosphazenes

The condensation reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆, with N-alkyl-N′-mono(4-nitrobenzyl)diamines (1–3), NO₂PhCH₂NH(CH₂) _n NHR₁ (R₁ = CH₃ or C₂H₅), led to the formation of the mono(4-nitrobenzyl)spirocyclotriphosphazenes (4–6). The tetra-pyrrolidino (4a–6a), piperidino (4b–6b), and 1,4-dioxa-8-azaspiro[4,5]decaphosphazenes (4c–6c) were prepared from(for) the reactions of partly substituted compounds (4, 5, and 6) with excess pyrrolidine, piperidine, and 1,4-dioxa-8-azaspiro[4,5]decane (DASD), respectively. The partly substituted geminal (4d and 5d) and cis-morpholino (6d) phosphazenes were isolated from the reactions of excess morpholine in boiling THF and o-xylene, but the expected fully substituted compounds were not obtained. The structures of all the phosphazene derivatives were determined by elemental analyses, MS, FTIR, ¹H, ¹³C{¹H}, ³¹P{¹H} NMR, HSQC, and HMBC techniques. The crystal structures of 4, 6, 4a, and 5a were verified by X-ray diffraction analysis. In addition, in vitro cytotoxic activities of fully substituted phosphazenes (4a–6c) against HeLa cervical cancer cell lines (ATCC CCL-2) and the compounds 4a and 4c against breast cancer cell lines (MDA-MB-231) and L929 fibroblast cells were evaluated, respectively. Apoptosis effect was determined by MDA-MB-231 cancer cell lines and fibroblast cells. The MIC values of the compounds were in the ranges of 9.8–19.5 µM. The compounds 6, 5a, 6a, 5b, and 6d have greater MIC activity against bacterial and yeast strain. The investigation of DNA binding with the phosphazenes was studied using plasmid DNA. The phosphazene derivatives inhibit the restriction endonuclease cleavage of plasmid DNA by BamHI and HindIII enzymes. BamHI and HindIII digestion results demonstrate that the compounds bind with G/G and A/A nucleotides.     

Aggregation in isomeric imides: analysis of the weak interactions in six <Emphasis Type="Italic">N</Emphasis>-(benzoyl)-<Emphasis Type="Italic">N</Emphasis>-(2-pyridyl)benzamides

Crystal structures of 4-chloro-N-(4-chlorobenzoyl)-N-(2-pyridyl)benzamide (I) Clpod, 3-chloro-N-(3-chlorobenzoyl)-N-(2-pyridyl)benzamide (II) Clmod and 2-chloro-N-(2-chlorobenzoyl)-N-(2-pyridyl)benzamide (III) Clood together with three methylated analogues, Mpod, Mmod and Mood, are presented herein. The Clxod acyclic imides are produced from reacting the 4-/3-/2-chlorobenzoyl chlorides (Clx) with 2-aminopyridine (o), respectively, together with their benzamide analogues Clxo; the Mxod/Mxo triad are produced similarly and in good yield. The five Clxod, Mpod and Mmod structures adopt the open transoid conformations as expected, but Mood crystallises with cisoid oriented benzoyl groups, and this conformation was unexpected, though not unknown. Halogen bonding contacts and weak hydrogen bonding C-H···N/O/π contacts are noted in the structures lacking strong hydrogen bonding donor atoms/groups but possessing a variety of strong and weaker acceptor atoms/groups. For Clxod, contact studies show that both hydrogen and carbon account for a high percentage of elements (70–75%) on the molecular surface and being the most abundant have C···H forming 26–30% of the contacts. Contact enrichment ratios are an indicator of the likelihood of chemical species to form intermolecular interactions with themselves and other species. The C-H···N and C-H···O are the most enriched (with E_HN?>?2.15), indicating that these weak hydrogen bonds are the driving force in the Clxod crystal packing formation. For Mxod, the C···H contact type at 40–52% is the most abundant contact type and C-H···O and C-H···N weak hydrogen bonds dominate with enrichment values in the 1.48–1.78 range. In Mxod, N/O···N/O contacts are effectively absent, except for Mpod (0.2%, N···N contacts) and both H···H and C···C non-polar contacts are moderately impoverished while the C···H interactions are slightly enriched (E?=?1.1–1.21).     

Structure of methyl-7-methoxy-7-phenyl-6-<Emphasis Type="Italic">endo</Emphasis>-halobicyclo[3.1.1]heptane-6-<Emphasis Type="Italic">exo</Emphasis>-carboxylate diastereomers in single crystals

The structure of diastereomeric methyl-7-anti-methoxy-7-syn-phenyl-and methyl-7-syn-methoxy-7-anti-phenyl-6-endo-bromobicyclo[3.1.1]heptane-6-exo-carboxylates 2a and 3a and their chlorine-and iodine-substituted analogs 2b and 3c was studied by XRD. The diastereomers differ in the geometrical parameters of the carbon framework of the molecules. The C(1)-C(2)-C(3)-C(4)-C(5)-C(6) six-membered ring is in the intermediate conformation between envelope and chair in structures 2 and envelope in structures 3. In compound 2a, the cyclobutane fragment has a higher degree of folding than in 3a; one of the possible reasons for that is the donor-acceptor interaction between the 6-methoxycarboxylic and 7-methoxy groups in molecule 2a.     

Synthesis and antibacterial and antifungal activities of <Emphasis Type="Italic">N</Emphasis>-(tetra-<Emphasis Type="Italic">O</Emphasis>-acetyl-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones

Background

Sydnone is a heterocycle that exhibits remarkable pharmacological activities, including antimicrobial, anti-inflammatory, analgesic, antipyretic and antioxidant activities. Thiosemicarbazones are of compounds that contain the –NHCSNHN=C< linkage group and are considerable interest because they exhibit important chemical properties and potentially beneficial biological activities. Similarly, thiosemicarbazones having carbohydrate moieties also exhibit various significant biological activities.

Results

The compounds of 3-formyl-4-phenylsydnones were obtained by Vilsmeyer-Haack’s formylation reaction and were transformed into thiosemicarbazones by condensation reaction with N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazide. Reaction were performed in the presence glacial acetic acid as catalyst using microwave-assisted heating method. Reaction yields were 43?85 %. The antimicrobial activities of these thiosemicarbazones were screened in vitro by using agar well diffusion and MIC methods. Among these thiosemicarbazones, compounds 4k, 4l, 4m and 4n were more active against all tested bacterial strains, especially against S. epidermidis, B. subtilis and E. coli. The MIC values in these cases are 0.156, 0.156 and 0.313 μg/mL, respectively. All compounds showed weak to moderate antifungal activity against C. albicans and A. niger than nystatin (MIC = 0.156?0.625 μg/mL vs. MIC = 0.078 μg/mL of nystatin), and thiosemicarbazones 4l, 4m and 4n exhibited significant activity with MIC = 0.156 μg/mL. These compounds also had good antifungal activity against F. oxysporum similarly to nystatin (MIC = 0.156 μg/mL). Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against three strains of fungal organisms.

Conclusions

In summary, we have developed a clean and efficient methodology for the synthesis of novel thiosemicarbazone derivatives bearing sydnone ring and d-glucose moiety; the heterocyclic and monosaccharide system being connected via ?NH?C(=S)NH?N=C< linker using molecular modification approach. The methodology could be further extended and used for the synthesis of other thiosemicarbazones of biological importance. 4-Formyl-3-arylsydnone N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones have been synthesized under microwave-assisted heating conditions. Almost all obtained compounds showed remarkable activities against the tested microorganisms. Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against all tested strains of bacterial and fungal organisms.

Open image in new window

Graphical abstract:Synthesis and antibacterial and antifungal activities of N-(tetra-O-acetyl-β-D-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones

     

Structural studies of nickel(II) complexes with 1-<Emphasis Type="Italic">tert</Emphasis>-butylimidazole-2-thione and 3-phenyl-5-methyl-pyrazole ligands

The nickel(II) complexes dichlorobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂Cl₂] (1), dinitratobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂(NO₃)₂] (2), dichloro-bis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)Cl₂] (3) and dinitratobis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)(NO₃)₂] (4) have been synthesized and studied. The single crystal X-ray diffraction analysis was carried out for 1 and 4 {Bruker Kappa Apex-II CCD diffractometer, MoK _α radiation}. Crystal data for 1: monoclinic C2/c, a = 16.949(2) Å, b = 8.6647(10) Å, c = 15.461(3) Å, β = 117.662(4)°, V = 2011.1(5) ų, Z = 4, D _calc = 1.460 g/cm³. Crystal data for 4: triclinic P-1, a = 9.9775(7) Å, b = 11.2254(8) Å, c = 14.8068(10) Å, α = 75.401(4)°, β = 87.422(4)°, γ = 74.874(4)°, V = 1548.86(19) ų, Z = 2, D _calc = 1.405 g/cm³. Coordination core of complex 1 adopts distorted tetrahedral geometry whereas core 4 has distorted octahedral geometry. The bonded nitrates are of two types coordinating as monodentate and bidentate ligands.     

Synthesis and antimicrobial activity of novel fused [1,2,4]triazino[5,6-<Emphasis Type="Italic">b</Emphasis>]indole derivatives

Synthesis of new fused systems of triazino[5,6-b]indole starting with preparation of 3-amino[1,2,4]-triazino[5,6-b]indole 1 by reaction of isatin with 2-aminoguanidinium carbonate in boiling acetic acid is presented [1]. Intermediate compound 1 reacted with aldehyde, ethyl chloroformate, triethyl orthoformate, and ninhydrine and gave new heterotetracyclic nitrogen systems, such as 3-(N ²-guanidinylimino)indole-2(1H)-one 2, 3-(N-ethoxycarbonylamino)-4H-[1,2,4]triazino[5,6-b]indole 3, 3-(N-ethoxymethyleneamino)-4H-[1,2,4]-triazino[5,6-b]indole 4, 3-(hydrazinothiocarbonylamino)-4H-[1,2,4]triazino[5,6-b]indole 5, respectively. N-(1,3-dioxoindene-2-ylidene)-4H-[1,2,4]triazino[5,6-b]indol-3-amine 6 was synthesized by reaction of compound 1 with aldehyde, ethyl chloroformate, triethyl orthoformate, and ninhydrine. New fused indole systems, pyrimido[2′,1′:3,4][1,2,4]triazino[5,6-b]indol-3(4H)-one 8, 9, 11, 12 and 1H-imidazo[2′,1′:3,4][1,2,4]triazino-[5,6-b]indol-2(3H)-one 10, were synthesized in the reaction of the intermediate 1 with bifunctional compounds. Structures of the products were elucidated from their elemental analysis and spectral data (IR, ¹H and ¹³C NMR and mass spectra). Antimicrobial activity of some synthesized compounds was tested.     

Catalytic <Emphasis Type="Italic">N</Emphasis>-formylation for synthesis of 6-substituted-2-benzothiazolylimino-5-piperazinyl-4-thiazolidinone antimicrobial agents

A new class of piperazine-based 2-benzothiazolylimino-4-thiazolidinones has been efficiently prepared via highly accelerated N-formylation of N-isopropylpiperazine by the use of a mild heterogeneous catalyst, sulfated tungstate. Heterocyclization of N-(benzo[d]thiazol-2-yl)-2-chloroacetamides (3a–j) by use of NH₄SCN in ethanol under reflux efficiently furnished the intermediates 2-benzothiazolyliminothiazolidin-4-ones (4a–j). These were treated with 4-isopropylpiperazine-1-carbaldehyde (2) to prepare the final products 5a–j. The structures of the new derivatives were confirmed by elemental analysis and use of spectroscopic data (FTIR and ¹H NMR). Their pharmacological potential as promising antimicrobial agents was determined in vitro against bacteria and a fungus; the lowest minimum inhibitory concentrations (MIC) observed were in the range 4–8 µg/mL.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.