Sushil K. Gupta

Synthesis and evaluation of antimicrobial activity of 4H-pyrimido[2,1-b]benzothiazole, pyrazole and benzylidene derivatives of curcumin

A novel, one-pot, simple, efficient procedure for 4H-pyrimido[2,1-b]benzothiazole (4a-h), pyrazole (6a-d) and benzylidene (7a-d) derivatives of curcumin under solvent and solvent free conditions in microwave with good yield is have been synthesized. The synthesized compounds were evaluated for their antibacterial activity against gram-positive and gram-negative bacteria viz. Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, Bacillus cereus and Providencia rettgeri and antifungal activity against fungi viz Aspergillus niger, Aspergillus fumigates, Aspergillus flavus. Detailed mechanistic study shows reaction proceeds through Knoevenagel type intermediate 3a which has been suggested as key intermediate for reaction (Fig. 3).

Design, synthesis, synergistic antimicrobial activity and cytotoxicity of 4-aryl substituted 3,4-dihydropyrimidinones of curcumin.

3,4-Dihydropyrimidinones of curcumin were synthesized in excellent yield by multi-component one-pot condensation of curcumin, substituted aromatic aldehydes and urea/thiourea under solvent free conditions using SnCl(2)·2H(2)O catalyst. All the synthesized compounds have been characterized by IR, (1)H NMR, (13)C NMR, Mass spectra as well as elemental analyses. The synthesized compounds 4a-n were evaluated for their synergistic antimicrobial (antibacterial and antifungal) activity against bacteria and fungi. Zone of inhibition was measured by adopting disc diffusion method. In vitro minimum inhibitory concentrations were measured using broth microdilution and food poisoning method. In addition to this in vitro cytotoxicity of synthesized compounds against three human cancer lines Hep-G2, HCT-116 and QG-56 were also evaluated. Most of the compounds showed interesting antimicrobial and cytotoxic activity as compared to curcumin, that is, the compounds derived from 2-hydroxy benzaldehyde, 4-hydroxy benzaldehyde and 4-hydroxy-3-methoxy benzaldehyde showed the highest biological activity as compared to other compounds.

Biological activity, design, synthesis and structure activity relationship of some novel derivatives of curcumin containing sulfonamides.

Five series of curcumin derivatives with sulfonamides 3a-3e, 4a-4e, 5a-5e, 6a-6e and 7a-7e have been synthesized and evaluated for in vitro antibacterial activity against selected medically important gram-(+) and gram-(-) bacterial species viz. Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Pseudomonas aeruginosa and Escherichia coli, and antifungal activity against few pathogenic fungal species viz. Aspergillus niger, Aspergillus flavus, Trichoderma viride and Curvularia lunata. The cytotoxicity has been determined by measuring IC50 values against human cell lines HeLa, Hep G-2, QG-56 and HCT-116. Among the compounds screened, 3a-3e showed the most potent biological activity against tested bacteria and fungi. Compounds 3a-3e displayed higher cytotoxicity than curcumin. The curcumin derivatives were also evaluated for in vivo anti-inflammatory activity. In contrast, the compounds 6a-6e and 7a-7e showed dramatically decrease in biological activity.

The crystal structure of 4-methyl-2,6-dibenzoylphenol and its conversion into a mononuclear cobalt(III) complex by treatment with cobalt(II) chloride and propane-1,3-diamine

Abstract The mononuclear cobalt(III) complex [Co(L)2]Cl (1) (where HL is H2N(CH2)3NC(Ph)C6H2(Me)(OH)COPh) has been synthesized by condensation of 4-methyl-2,6-dibenzoylphenol (mdbp) I and propane-1,3-diamine in the presence of CoCl2·6H2O. Compound 1 has been characterized by mass, IR, electronic, 1H and 13C NMR spectroscopy, conductivity measurements, elemental analysis, TGA, cyclic voltammetry and an X-ray structure determination of the solid complex 1·2EtOH·H2NCH2CH2CH2NH2. The cobalt(III) coordination sphere in [Co(L)2]+ is cis-CoN4O2 with the NNO-ligands mer. The average CoN and CoO distances are, respectively, 1.950(5) and 1.882(5) A. The N⋯N bite distance is 2.76(5) A and the NCoN and OCoO bite angles are, respectively, 89.7(2)° and 92.6(2)° for the six-membered chelate ring. Electrochemical studies of complex 1 using cyclic voltammetry indicate an irreversible cathodic peak (Epc, ca. −0.67 V) corresponding to reduction of cobalt(III) to cobalt(II). The crystal structure of the precursor, (mdbp) I is also reported. The phenolic hydrogen forms hydrogen bonds of length 2.58 A with the carbonyl oxygen.

Synthesis, Characterization and Crystal Structure of a Nickel(II) Schiff Base Complex Derived from Acetylacetone and Ethylenediamine

The square-planar nickel (II) complex of composition [Ni(bae)]·½H2O (1) [where H2bae is bis(acetylacetone)ethylenediamine] has been synthesized by [2 + 1] template condensation of acetylacetone and ethylenediamine in the presence of NiCl2·6H2O and characterized. An X-ray structure determination of the complex has been completed. Average Ni-N and Ni-O distances are, respectively, 1.86(2) Å and 1.849(14) Å. N···N bite distance and bite angle are 2.627(6) Å and 87.2(2)°, respectively, for the five-membered chelate ring. The water molecule forms hydrogen bonds with O atoms of two complex molecules.

Role of calcinations and basicity of hydrotalcite as catalyst for environmental benign novel synthesis of 4H-pyrimido[2,1-b][1,3]benzothiazole derivatives of curcumin

A simple, efficient and step-economy synthesis to afford the library of 4H-pyrimido[2,1-b][1,3]benzothiazole derivatives of curcumin (4a–4h) from readily available substrates curcumin (potential biological molecule), 2-amino benzothiazole (biological active) and substituted aromatic aldehydes using novel heterogeneous calcined Mg-Al-CO3 hydrotalcite under solvent free conditions is described. The calcined hydrotalcite with an Mg/Al ratio of 3:1 derived from calcinations at 750 K was found to be a suitable catalyst that gives the highest basicity and the best catalytic activity for this reaction. The catalysts were characterized with XRD and SEM and Hammett titration method. This protocol has several advantages such as easy to work up, high activity of catalyst and reusability.

Mononuclear iron(III)macrocyclic complexes derived from 4-methyl-2,6-di(formyl/benzoyl)phenol and diamines: synthesis, spectral speciation and electrochemical behaviour

Abstract Two series of macrocyclic iron(III) complexes of stoichiometry [Fe(L)Cl2]Cl (1, 2) have been synthesised and characterised. Compounds belonging to series 1 are derived from 4-methyl-2,6-diformylphenol and diamines (H2L), and those of 2 from 4-methyl-2,6-dibenzoylphenol and diamines. All the brown complexes have been characterised by physicochemical techniques. The mass, infrared, electronic, ESR and Mossbauer spectroscopies, magnetic susceptibility data, molar conductance, X-ray diffraction and cyclic voltammetric studies provide unambiguous evidence that 1 and 2 are high-spin iron(III) complexes in which the metal has an octahedral geometry. The Mossbauer data are consistent with high-spin iron(III) and substantial covalency in the Fe(III)–ligand bonds. Cyclic voltammetric studies in DMSO of the mononuclear iron(III) complexes show that they undergo quasi-reversible reduction with E1/2 approximately −0.74 V versus SCE.

Syntheses of phenoxo-bridged Zn(II) and metallamacrocyclic Hg(II) complexes of organochalcogen (Se, Te) substituted Schiff-bases: structure and DNA-binding studies of Zn(II) complexes

The coordination of organochalcogen (especially Se and Te) substituted Schiff-bases L1H, L2H, L3H, and L4H toward Zn(II) and Hg(II) has been studied. Reactions of these ligands with ZnCl2 in 1 : 1 molar ratio gave binuclear complexes [{2-[PhX(CH2) n N = C(Ph)]-6-[PhCO]-4-MeC6H2O}2Zn2Cl2] (where X = Se, n = 2 (1); X = Se, n = 3 (2); X = Te, n = 2 (3); and X = Te, n = 3 (4)) with partial hydrolytic cleavage of proligands. In these complexes, two partially hydrolyzed ligand fragments coordinate tridentate (NOO) with two Zns. Reaction of HgBr2 with L1H and L2H in 1 : 1 molar ratio gave monometallic complexes [C6H2(4-Me)(OH)[2,6-{C(Ph) = N(CH2) n Se(Ph)}2HgBr2]] (n = 2 (5) or 3 (6)) and under similar conditions with L3H and L4H gave bimetallic complexes [C6H2(4-Me)(OH)[2,6-{C(Ph) = N(CH2) n Te(Ph)}2Hg2Br4]] (n = 2 (7) or 3 (8)) in which the ligands coordinate with metal through selenium or tellurium, leaving the imino nitrogen and phenolic oxygen uncoordinated. The proligands L1H, L2H give 14- or 16-membered metallamacrocycles through Se–Hg–Se linkages and L3H, L4H give 16- or 18-membered metallamacrocycles through Te–Hg–Br–Hg–Te linkages. All the complexes were characterized by elemental analyses, ESIMS, FTIR, multinuclear NMR, UV-Vis, and conductance measurements. The redox properties of the complexes were investigated by cyclic voltammetry (CV). Complexes 1–4 exhibited ligand-centered irreversible oxidation processes. Complexes 5 and 6 showed metal-centered quasi-reversible single electron transfer, whereas dinuclear complexes 7 and 8 displayed two quasi-reversible, one-electron transfer steps. A single-crystal X-ray structure determination of 1 showed that the coordination unit is centrosymmetric with Zn(II) in square-pyramidal coordination geometry and the two square pyramids sharing an edge. The Zn ··· Zn separation is 3.232 Å. The DNA-binding properties of 1 and 3 with calf thymus DNA were explored by a spectrophotometric method and CV.

Synthesis and structure of mononuclear copper(II) complexes with acyclic Schiff-base ligands containing organotellurium substituents: a comparative study with selenium analogs

Tellurium-bearing acyclic Schiff bases, 2,6-bis({N-[2-(phenyltellurato)ethyl]}benzimidoyl)-4-methylphenol (HL3 ) and 2,6-bis({N-[3-(phenyltellurato)propyl]}benzimidoyl)-4-methylphenol (HL4 ) of the Te2N2O type have been prepared by condensation of 4-methyl-2,6-dibenzoylphenol (mdbpH) with the appropriate phenyltellurato(alkyl)amine. HL3 and HL4 have been characterized by mass spectrometry, IR, electronic and 1H-NMR spectroscopies and cyclic voltammetry. Their reactions with Cu(II) acetate monohydrate in a 2 : 1 molar ratio in methanol yield [(C6H2(O)(Me){(C6H5)C=N(CH2)nTe(C6H5)}{(C6H5)C=O})2Cu] (3 (n = 2), 4 (n = 3)) as suggested by analytical and spectroscopic data and single crystal X-ray crystallography of 3. In both complexes, one arm of the ligand undergoes hydrolysis at the C=N position and two molecules of the partially hydrolyzed ligand coordinate to Cu(II) through imido nitrogen and the phenolic oxygen. The telluriums do not form part of the copper(II) distorted square planar coordination sphere which has a trans-CuN2O2 core. Electrochemical studies of 3 and 4 indicate quasi-reversible reductions (E°′ = −1.113 V (3) and −1.149 V (4)) corresponding to the reduction of copper(II) to copper(I). The interactions of 3 and 4 with calf thymus DNA, investigated by spectrophotometry and cyclic voltammetry, indicate that 3 and 4 bind to DNA via intercalation, and the binding affinity of 3 is lower than that of its selenium analog.

Synthesis and spectroscopic characterization of tris{(diphenylphosphino) dimethylsilyl}methane complexes of cr(0) and w(0)

Treatment of M(CO)6 (M = Cr, W) with (Ph2PMe2Si)3CH in toluene at elevated temperatures resulted in the isolation of pale green [Cr(CO)3{(Ph2PMe2Si)3CH}] and pale brown [W(CO)3{(Ph2PMe2Si)3CH}] in high yield. These complexes have been characterized by elemental analysis, conductivity measurements, TGA, mass spectrometry, and IR, electronic, 1H and 31P{1H} NMR spectroscopy. The complexes have pseudo octahedral geometry around the metal atom with tridentate coordination of the multidentate ligand. The six-membered MPSiCSiP metallacycles are shown to have high fluxionality at room temperature on the NMR time scale.