Synthesis,X-ray structures,and magnetic properties of heterometal dinuclear Cr(III)–M(II) complexes

New 3,5-bis(2-pyridyl)pyrazolato (bpypz) bridged heterometal dinuclear complexes [(nta)Cr(μ-bpypz)M^II(picen)]⁺ (M = Mn(II), Ni(II)) and [(acac)₂Cr(μ-bpypz)Ni^II(picen)]²⁺ (nta = nitrilotriacetate, picen = N,N′-bis(2-pyridylmethyl)ethylenediamine, acac = acetylacetate) were synthesized and characterized by the X-ray analysis, ESI-MS and the magnetic measurements, and/or ²H NMR spectra. The molecular structures were compared from a viewpoint of the conformation of the picen depending on M^II ionic radii or different modes of hydrogen bonds. The picen in [(nta)Cr(μ-bpypz)Mn^II(picen)]BF₄ takes an abnormal conformation with intramolecular bifurcated three-center hydrogen bonds between two carboxylate oxygens of nta and an amine proton of the picen as found for the previously reported corresponding Fe(II) complex [K. Ni-iya, A. Fuyuhiro, T. Yagi, S. Nasu, K. Kuzushita, S. Morimoto, S. Kaizaki, Bull. Chem. Soc. Jpn. 74 (2001) 1891]. On the other hand, for both Ni(II)-nta and Ni(II)-acac complexes, the picen takes a normal conformation with only a two-center hydrogen bond between non-bridging ligands. The magneto-structural relation is discussed for the Cr(III)–Ni(II) complexes in connection with the orthogonality or orbital overlap arising from the difference in distortion around Cr(III) moiety.     

Synthesis and characterization of new dinuclear complexes of molybdenum(V) with β′-hydroxy-β-enaminones

New dinuclear molybdenum(V) complexes have been obtained by the reaction of [Mo₂O₃(acac)₄] (acac=acetilacetonate ion) with the polydentate ligands, β′-hydroxy-β-enaminones. All prepared complexes consist of Mo₂O₄ ²⁺ core coordinated by two ligands as in the β-diketonates only through two donor oxygen atoms. Such bonding gives the opportunity for the sixth coordination place around molybdenum to be completed by the monodentate solvent molecule D. All compounds have been characterized by means of elemental analyses, one- and two-dimensional NMR spectroscopy, IR spectroscopy as well as by thermal analyses. The molecular and crystal structures of the molybdenum(V) complexes 1a and 1b coordinated by two different isomeric ligands as well as of the isomer a itself have been determined by a single crystal X-ray diffraction method.     

Synthesis, electrochemistry and mixed-valence state of dinuclear tris(acetylacetonato)ruthenium(III) complexes bridged by sulfur atoms at the γ-position of acetylacetonate

Dinuclear tris(acetylacetonato)ruthenium(III) complexes bridged by one sulfur atom (1) or two sulfur atoms (2) at the γ-position of the acetylacetonate have been synthesized by the reactions of tris(acetylacetonato)ruthenium(III) with SCl₂ or S₂Cl₂. The molecular structure of 2 has been determined by single crystal X-ray diffraction study. The cyclic voltammograms of both the dinuclear complexes exhibit two one-electron reduction waves in acetonitrile (AN), dichloromethane (DM), benzonitrile (BN), and N,N-dimethylformamide (DMF). While the complex 1 exhibited two one-electron oxidation waves in AN, DM, and BN, complex 2 showed only irreversible waves in all the solvents. The comproportionation constants (K_c) for mixed-valence states of both Ru^II/Ru^III and Ru^III/Ru^IV were calculated from the redox potentials of dinuclear complexes. The values of log₁₀K_c (Ru^II/Ru^III) (for complexes 1 and 2) and log₁₀K_c (Ru^III/Ru^IV) (for complex 1) were between 1.35 and 3.55. These values are not so large and hence, the complexes may be classified as class II in the Robin and Day classification. Although no relationship could be found between K_c and the dielectric constant of the solvent, there exists a correlation between donor number (DN) of the solvent and log₁₀K_c values.     

Synthesis and characterization of tris(β-diketonato)technetium(III) and -(IV) complexes

The preparations and properties of tris(dipivaloylmethanato)technetium(III), tris(trifluoroacetylacetonato)technetium(III), and tris(hexafluoroacetonato)technetium(III) are described. The oxidation of the dipivaloyl derivative to tris(dipivaloyl)technetium(IV) hexafluorophosphate was shown to take place readily. Voltammetric studies and magnetic resonance results on the new complexes are reported. The large shifts observed for the complexes seem to be due to a contact interaction.     

Synthesis and characterization of β-diketiminate germanium(II) and tin(II) bromides

The equimolar reaction of a β-diketiminate lithium salt LLi(OEt₂) [L = HC(CMeNAr)₂; Ar = 2,6-iPr₂C₆H₃] with either GeBr₂ or SnBr₂ in diethyl ether affords the synthetically useful monomeric β-diketiminate-element halides LGeBr (1) and LSnBr (2), respectively. Both are soluble in hydrocarbon solvents, stable in inert atmosphere, and have been characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction analysis.     

Synthesis and characterization of alkynes β-diketonate copper(I) complexes

The reactions of 1,3,5-tris-(trimethylsilylethynyl)benzene (1) with Cu₂O and 1,1,1,5,5,5,-hexafluoroacetylacetone in alkyne to Cu ratios 1:0.5, 1:1 and 1:3 in CH₂Cl₂ at room temperature give copper complexes (η²-1,3,5-tris(trimethylsilylethynyl)benzene)(Cu(hfac)) (2), (η²:η²-1,3,5-tris(trimethylsilylethynyl)benzene)(Cu(hfac))₂ (3) and (η²:η²:η²-(1,3,5- tris(trimethylsilylethynyl)benzene))₂(Cu(hfac))₃(4), respectively. In the same conditions, 2,5-bis-(trimethylsilylethynyl)thiophene (5) reacts with 0.5 or 1 equiv. of Cu₂O to give (η²:η²-2,5-bis(trimethylsilylethynyl)thiophene)(Cu(hfac)) (6) and (η²:η²-2,5-bis(trimethylsilylethynyl)thiophene)(Cu(hfac))₂ (7), respectively, and 1,4-bis(trimethylsilyl)-1,3-butadiyne (8) with 0.5 equiv. of Cu₂O give (η²:η²-1,4-bis(trimethylsilyl)-1,3-butadiyne)(Cu(hfac))₂(9). All the new compounds have been characterized by analytical and spectroscopic methods and their thermal properties were examined by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Synthesis,characterization and biodistribution of tris(β-diketonato)technetium(III) complexes

New tris(β-diketonato) complexes of trivalent ⁹⁹Tc/^99mTc with the ligands hexane-2,4-dione, heptane-2,4-dione, heptane-3,5-dione, and octane-3,5-dione were synthesized by reduction of pertechnetate with dithionite in the presence of excess β-diketone. The complexes were purified by HPLC, identified by elemental analysis and FAB mass spectrometry, and characterized by vis./u.v./i.r. spectrophotometry. The hexane-2,4-dionato complex crystallizes in the monoclinic space group P2₁/c, isostructurally with pentane-2,4-dionatotechnetium(III). Biodistribution measurements in mice showed the neutral and lipophilic ^99mTc-diketonato complexes to penetrate the blood-brain barrier. However, increasing lipophilicity decreased the brain uptake except for the heptane-2,4-dionato complex, which displayed the highest uptake of 0.82% injected dose/g.     

Synthesis and assay of structural intermediates of crustacean pigment-dispersing hormones (α and β-PDH)

Summary

The two characterized crustacean pigment-dispersing hormones (α-PDH; β-PDH) are octadecapeptides which differ in primary structure at six positions. Assays for melanophore pigment-dispersing activity showed β-PDH to be 21-fold more potent than α-PDH. In an effort to explain the difference in potencies between the two PDHs, we synthesized and purified six analogs of α-PDH (Leu^4?, Leu^11?, Lys^13?, Asn^16?, Asp^17?, and Glu³, Leu^4? α-PDH) in which the amino acid residues of α-PDH were substituted with those of β-PDH. Four analogs (Leu^11?, Lys^13?, Asn^16?, and Asp^17? α-PDH) possessed melanophore-dispersing activity equivalent to α-PDH. Leu^4? α-PDH and Glu³, Leu^4? α-PDH were 2.4? and 4-fold more potent than α-PDH, respectively. Glu^3-α-PDH was 3.3-fold more potent than α-PDH (Jorenby et al., 1987). These results suggest that the 21-fold increase in activity of β-PDH over α-PDH is due to an interactive effect of two or more substitutions rather than from the product of the effects brought about by individual substitutions.     

Synthesis and antitumor activity of β-carboline 3-(substituted-carbohydrazide) derivatives

A series of β-carboline derivatives bearing a substituted-carbohydrazide moiety at C-3 were synthesized and evaluated for their antitumor activity against eight human cancer cell lines. The β-carboline N-(substituted-benzylidene)carbohydrazides showed, in general, a greater antitumor activity than their N-(alkylidene)carbohydrazide analogues. The N(9)-methylation of β-carboline N-(substituted-benzylidene) carbohydrazides resulted in a decrease of antitumor activity. Among compounds tested, the benzylidene-carbohydrazides 3, 4, 11, 13, 16, 21 and 22 were the most active, possessing IC(50) less than 10 μM for six of the eight tumor cell lines assayed. The derivative 4 displayed the most significant activity toward all tested cell lines, with a remarkable cytotoxicity against renal (786-0) cell lines (IC(50)=0.04 μM). Compound 4 was assayed for its in vivo antineoplastic activity in the Ehrlich solid carcinoma assay.     

Synthesis and characterization of quaternized β-chitin

Water-soluble 2′-O-hydroxypropyltrimethylammoniumchitin chloride (2′-O-HTACCt) was prepared directly from β-chitin and 3-chloro-2-hydroxypropyltrimethylammonium chloride (CTA) in basic medium. The effect of alkali concentration, reaction temperature, reaction time, and dosage of CTA on yield and degree of substitution (DS) of 2′-O-HTACCt were studied. These quaternized chitin derivatives were characterized by FTIR and ¹H NMR spectroscopy, conductometric titration, and elemental analysis methods. Research results indicate that β-chitin can react directly with CTA to produce a water-soluble 2′-O-HTACCt derivative with a high DS. The optimal preparation conditions were determined to be 35-40 wt % (aq NaOH), 40 °C (reaction temperature), 6 h (reaction time), and 4 (molar ratio of CTA to β-chitin unit).     

Synthesis, molecular modeling and biological evaluation of β-ketoacyl-acyl carrier protein synthase III (FabH) as novel antibacterial agents

A series of novel cinnamic acid secnidazole ester derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of FabH. These compounds were assayed for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Compounds with potent antibacterial activities were tested for their E. coli FabH inhibitory activity. Compound 3n showed the most potent antibacterial activity with MIC of 1.56-6.25 μg/mL against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with IC?? of 2.5 μM. Docking simulation was performed to position compound 3n into the E. coli FabH active site to determine the probable binding conformation.     

Anhydrous and hydrated lanthanide(III) β,δ-triketonates

Complexes of the β,δ-triketones benzoylacetone and diacetylacetone with lanthanide(III) ions are reported. The compounds with the first ligand (formulated Ln(Hbaa)₃) are anhydrous while those with the last one (formulated Ln(Hdaa)₃·H₂O) are hydrated. IR and TGA analyses were carried out to confirm the anhydrous or hydrated character of the complexes. The anhydrous character of the lanthanide complexes with benzoylacetone is discussed in terms of the larger steric requirements in the terminal groups of the ligand with respect to those in the compounds with diacetylacetone.     

Synthesis of methyl α- and β-maltotriosides and aryl β-maltotriosides

Reaction of β-maltotriose hendecaacetate with phosphorus pentachloride gave 2′,2″,3,3′,3″,4″,6,6′,6″,-nona-O-acetyl-(2)-O-trichloroacetyl-β-maltotriosyl chloride (2) which was isomerized into the corresponding α anomer (8). Selective ammonolysis of 2 and 8 afforded the 2-hydroxy derivatives 3 and 9, respectively; 3 was isomerized into the α anomer 9. Methanolysis of 2 and 3 in the presence of pyridine and silver nitrate and subsequent deacetylation gave methyl α-maltotrioside. Likewise, methanolysis and O-deacetylation of 9 gave methyl β-maltotrioside which was identical with the compound prepared by the Koenigs—Knorr reaction of 2,2′,2″,3,3′,3″,4″,6,6′,6″-deca-O-acetyl-α-maltotriosyl bromide (12) with methanol followed by O-deacetylation. Several substituted phenyl β-glycosides of maltotriose were also obtained by condensation of phenols with 12 in an alkaline medium. Alkaline degradation of the o-chlorophenyl β-glycoside decaacetate readily gave a high yield of 1,6-anhydro-β-maltotriose.     

Purification and characterisation of an inducible β-galactosidase from Corynebacterium murisepticum

The -galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The K _m values of the enzyme for the substrates lactose and o-nitrophenyl--d-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction.     

Synthesis of β-Tubanol

Synthesis of β-tubanol (VIa) was achieved by the bromination of dihydro-β-tubanol acetate (VIIb) followed by dehydrobromination and the subsequent hydrolysis. 2,2-Dimethyl-5-hydroxy-chromanone as well as its derivatives (IV) and the corresponding chromanols (V) and chromans (VII) were also prepared.     

Synthesis of (±)-Homosarkomycin and (±)-Rosaprostol

(±)-Homosarkomycin (2) and (±)-rosaprostol (3) were synthesized from (±)-methyl 2-oxo-bicyclo[3.1.0]hexane-1-carboxylate (1) by using the nucleophilic ring opening reaction on the double-activated cyclopropane ring as the key step.     

Synthesis of (±)-Lamprolobine and (±)-Epilamprolobine

(±)-Lamprolobine, the (+)-enatiomer of which was isolated from the leaves of Lamprolobium fruticosum, and (±)-epilamprolobine were synthesized from δ-valerolactam.     

Synthesis and β-glucuronidase inhibitory activity of 2-arylquinazolin-4(3H)-ones

2-Arylquinazolin-4(3H)-ones 1–25 were synthesized by reacting anthranilamide with various benzaldehydes using CuCl₂·2H₂O as a catalyst in ethanol under reflux. Synthetic 2-arylquinazolin-4(3H)-ones 1–25 were evaluated for their β-glucuronidase inhibitory potential. A trend of inhibition IC₅₀ against the enzyme in the range of 0.6–198.2 μM, was observed and compared with the standard d-saccharic acid 1,4-lactone (IC₅₀ = 45.75 ± 2.16 μM). Compounds 13, 19, 4, 12, 14, 22, 23, 25, 15, 8, 17, 11, 21, 1, 3, 18, 9, 2, and 24 with the IC₅₀ values within the range of 0.6–44.0 μM, indicated that the compounds have superior activity than the standard. The compounds showed no cytotoxic effects against PC-3 cells. A structure–activity relationship is established.     

Synthesis and spectral properties of Zr(IV) and Hf(IV) phthalocyanines with β-diketonates as axial ligands

The series of new zirconium(IV) and hafnium(IV) phthalocyanines with various β-dicarbonyl ligands were prepared via direct interaction between di(chloro)zirconium(IV) or hafnium(IV) phthalocyanines and free β-diketones and also with 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one. The structure of the obtained bis(β-dicarbonilato) zirconium(IV) and hafnium(IV) phthalocyanines was studied by two dimension ¹H NMR spectroscopy (COSY, NOESY, ROESY). Absorption and fluorescence spectroscopic studies have been investigated in various solvents. Analyzed compounds of concentration range below 10^?5 mol/dm³ do not aggregate in the organic solvents. Fluorescence quantum yields (Φ_F) and natural life times (τ) of zirconium phthalocyanine complexes have been calculated in toluene, DMSO and THF.     

Synthesis of mixed sphere β-diketonate nickel(II) complexes

Complexes of the type [Ni(β-diketonate)(L L)_1,2] (LL = diphosphine, (2), en or dipy, (3)) have been synthesized from [Ni(β-diketonate)₂] (1) and the free ligand under stoichiometric conditions in ethanol. Complexes 2 are square-planar species, while compounds 3 are hexacoordinate complexes, all being quite stable toward ligand disproportionation. The ligand-set {P₂O₂^-} appears to be particularly stable in the nickel(II) coordination sphere and turns out to exert a fairly strong average ligand field.