Inhibition of the calcium-activated chloride current in cardiac ventricular myocytes by N-(p-amylcinnamoyl)anthranilic acid (ACA)

N-(p-amylcinnamoyl)anthranilic acid (ACA), a phospholipase A₂ (PLA₂) inhibitor, is structurally-related to non-steroidal anti-inflammatory drugs (NSAIDs) of the fenamate group and may also modulate various ion channels. We used the whole-cell, patch-clamp technique at room temperature to investigate the effects of ACA on the Ca²⁺-activated chloride current (I_Cl(Ca)) and other chloride currents in isolated pig cardiac ventricular myocytes. ACA reversibly inhibited I_Cl(Ca) in a concentration-dependent manner (IC₅₀ = 4.2 μM, n_Hill = 1.1), without affecting the L-type Ca²⁺ current. Unlike ACA, the non-selective PLA₂ inhibitor bromophenacyl bromide (BPB; 50 μM) had no effect on I_Cl(Ca). In addition, the analgesic NSAID structurally-related to ACA, diclofenac (50 μM) also had no effect on I_Cl(Ca), whereas the current in the same cells could be suppressed by chloride channel blockers flufenamic acid (FFA; 100 μM) or 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS;100 μM). Besides I_Cl(Ca), ACA (50 μM) also suppressed the cAMP-activated chloride current, but to a lesser extent. It is proposed that the inhibitory effects of ACA on I_Cl(Ca) are PLA₂-independent and that the drug may serve as a useful tool in understanding the nature and function of cardiac anion channels.     

Synthesis, spectroscopic and structural characterization of the reaction products of quaternary cationic 2,2′-bipyridylium ligand bromide salts with metal halides

The synthesis and spectroscopic characterization of quaternary salts containing 2,2,-bipyridine, 1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline and 3,4,7,8-tetramethyl-1,10-phenanthroline is reported. The coordinating behaviour of the bipyridylium salts toward palladium, copper and dimethyltin(IV)halides is investigated. The reaction of N-R,2,2′-bipyridylium (= L¹) bromide (R = 4-Cl-C₆H₄ · CO · CH₂) with palladium(II) chloride in acetonitrile solution yields a crystalline product, shown by a single crystal X-ray study to be L¹PdX₃, where X is a Cl/Br (1:1) composite.     

Unprecedented formation of binuclear copper(II) complex with a perylene derived ligand by the oxidative reaction

A new perylene-pendent tridentate ligand, N-(3-perylenylmethyl)-N,N-bis(2-pyridylmethyl)amine (perbpa) 1 and its Cu(II) complex, [Cu(perbpa)Cl₂] (2) were prepared and structurally characterized by the X-ray diffraction method. In the packing structure of ligand 1, perylene groups were aggregated to form a π-π stacked layer of dimerized pelylene moieties similar to the packing of pristine perylene. This result suggests both that the π-π interactions among the perylene moieties predominate for the arrangement of perbpa molecules in the crystal and that this ligand is a good candidate for constructing electron conducting path. A complex 2 was prepared from the ligand 1 and a copper(II) chloride dehydrate. Complex 2 had a mononuclear and 5-coordinate distorted square pyramidal structure with a perbpa and two coordinated chloride ions. The chemical oxidation of 2 by iodine resulted in the unprecedented binuclear Cu(II) species, [Cu₂(μ-Cl)₂(perbpa)₂](I₃)₂, 3·(I₃)₂. An X-ray crystal structure analysis of 3·(I₃)₂ revealed the binuclear structure bridged by the chloride ions. A temperature dependent magnetic susceptibility measurement of 3 showed a weak ferromagnetic exchange interaction with S = 1 ground state, g = 2.12 and J = +1.17 cm⁻¹, based on H = −2JS₁ · S₂. The UV-Vis absorption and the EPR spectra of 3 showed that the perylene groups are not oxidized. These results indicate a couple of Cu(II) constructed S = 1 ground state with intermolecular ferromagnetic interaction. The electrochemical study suggested that the crystallization of 3·(I₃)₂ was initiated by the oxidation of the N,N-bis-(2-pyridylmethyl)amino (bpa) groups of 2 by I₂.     

Structure and luminescence of copper(I) cyanide-amine and -sulfide networks

Copper(I) cyanide reacts with various liquid amines and sulfides (L) under solvent-less conditions to form (CuCN)L_n, n = 0.5, 0.57, 0.75, 0.8, 1, 1.25, 1.5, 2. New X-ray structures are reported for L = Py (Py = pyridine, n = 0.57), 2-MePy (n = 1), 3-EtPy (n = 1.5), 2-ClPy (n = 1), 3-ClPy (n = 2), 3-MeOPy (n = 2), 4-^tBuPy (n = 1.5), piperidine (n = 1.25), N-methylmorpholine (n = 1), N,N-dimethylcyclohexylamine (n = 1), 1-methylimidazole (n = 3), Me₂S (n = 1), and tetrahydrothiophene (n = 1). The amine structures (except for the monomeric 1-methylimidazole complex) reveal 1D CuCN chains decorated with 0-2 L per metal atom. Chain structures observed include zigzag, helical and figure-8 helical. The CuCN-sulfide structures show sulfur-bridging of CuCN chains. In some cases (CuCN)L_?1.5 species are transformed to (CuCN)L under vacuum. Thermal analysis shows facile release of ligand, yielding CuCN. Most of the (CuCN)L_n products are photoluminescent, emitting in the visible region. In some cases, coordination of very similar amines results in remarkably different emission spectra.     

Synthesis and characterization of the 1:1 adducts of copper(I) halides with bidentate N,N′-bis(benzophenone)-1,2-diiminoethane Schiff base: Crystal structures of [Cu(bz2en)2][CuX2] (X = Br, I) complexes

1:1 adducts of N,N′-bis(benzophenone)-1,2-diiminoethane (bz₂en) with copper(I) chloride, bromide and iodide, [Cu(bz₂en)₂][CuX₂] (X = Cl, Br, and I), have been synthesized and the structures of the solid bromide and iodide adducts were determined by X-ray crystallography from single-crystal data. The solid-state structure reveals ionic complexes containing a cation of copper(I) ion coordinated to four nitrogen atoms of two bz₂en molecules (distorted tetrahedron) and a linear dibromocuprate(I) and a di-μ-iodo-diiododicuprate(I) anion for the bromo and iodo adducts, respectively. The bromo adduct structure contains CH?Br intermolecular hydrogen bonds. The complexes are very stable towards atmospheric oxygen in the solid state. The spectral properties of the above complexes are also discussed.     

Functional model for intradiol-cleaving catechol 1,2-dioxygenase: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted salicylaldimine ligands

A series of mononuclear iron(III) complexes with containing phenolate donor of substituted-salicylaldimine based ligands [Fe(L¹)(TCC)] · CH₃OH (1), [Fe(L²)(TCC)] · CH₃OH (2), [Fe(L³)(TCC)] (3), and [Fe(L⁴)(TCC)] (4) have been prepared and studied as functional models for catechol dioxygenases (H₂TCC = tetrachlorocatechol, or HL¹ = N′-(salicylaldimine)-N,N-diethyldiethylenetriamine, HL² = N′-(5-Br-salicylaldimine)-N,N-diethyldiethylenetriamine, HL³ = N′-(4,6-dimethoxy-salycyl-aldimine)-N,N-diethyl-diethylenetriamine, HL⁴ = N′-(4-methoxy-salicylaldimine)-N,N-diethyl-diethylenetriamine). They are structural models for inhibitors of enzyme-substrate adducts from the reactions of catechol 1,2-dioxygenases. Complexes 1-4 were characterized by spectroscopic methods and X-ray crystal structural analysis. The coordination sphere of Fe(III) atom of 1-4 is distorted octahedral with N₃O₃ donor set from the ligand and the substrate TCC occupying cis position, and Fe(III) is in high-spin (S = 5/2) electronic ground state. The in situ prepared iron(III) complexes without TCC, [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)Cl₂], and [Fe(L⁴)Cl₂] are reactive towards intradiol cleavage of the 3,5-di-tert-butylcatechol (H₂DBC) in the presence of O₂ or air. The reaction rate of catechol 1,2-dioxygenase depends on the redox potential and acidity of iron(III) ions in complexes as well as the substituent effect of the ligands. We have identified the reaction products and proposed the mechanism of the reactions of these iron(III) complexes with H₂DBC with O₂.     

Synthesis and characterization of a series of N3O-ligated mononuclear Mn(II) halide complexes

Treatment of a N₃O-donor chelate ligand (mpppa = N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine; bpppa = N-benzyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine) with equimolar amounts of Mn(ClO₄)₂ · 6H₂O and Me₄NX (X = Cl, Br, I) in methanol resulted in the production of a series of mononuclear Mn(II) halide complexes of the formula [(L)Mn-X(CH₃OH)]ClO₄ (L = mpppa or bpppa). X-ray crystallographic studies of [(mpppa)Mn-Cl(CH₃OH)]ClO₄ · CH₃OH (2 · CH₃OH), [(mpppa)Mn-Br(CH₃OH)]ClO₄ · CH₃OH (4 · CH₃OH), [(mpppa)Mn-I(CH₃OH)]ClO₄ · CH₃OH (6 · CH₃OH), and [(bpppa)Mn-I(CH₃OH)]ClO₄ · O₂(CH₂CH₃)₂ (7 · O(CH₂CH₃)₂) revealed for each a mononuclear Mn(II) center having tetradentate coordination of the chelate ligand, one coordinated halide anion, and one molecule of coordinated methanol. An increase in the Mn-X distance through the halide series (Cl, Br, I) correlates linearly with the increase in the radius of the anion. The magnetic moment of each halide complex, measured via Evans method in methanol, is consistent with the presence of a high-spin distorted octahedral Mn(II) center. The EPR features of the halide complexes in methanol do not change as a function of the nature of the halide coordinated to the Mn(II) center.     

Syntheses, structures, and properties of Co(III) complexes derived from polypyridine ligands containing one carboxamido nitrogen donor

Four cobalt(III) complexes containing the polypyridine pentadentate ligands N,N-bis(2-pyridylmethyl)amine-N′-ethyl-2-pyridine-2-carboxamide (PaPy₃H), N,N-bis(2-pyridylmethyl)amine-N′-[1-(2-pyridylethyl)acetamide (MePcPy₃H), and N,N-bis(2-pyridylmethyl)amine-N′-(2-pyridylmethyl)acetamide (PcPy₃H), have been synthesized. All three ligands bind the Co(III) center in the same fashion with the exception of loss of conjugation between the carboxamide moiety and the pyridine ring in the latter two. The structures of [(PaPy₃)Co(OH)][(PaPy₃)Co(H₂O)](ClO₄)₃ · 3H₂O (1), [(PaPy₃)Co(NO₂)](ClO₄) · 2MeCN (2), [(MePcPy₃)Co(MeCN)](ClO₄)₂ · 0.5MeCN (3), and [(PcPy₃)Co(Cl)](ClO₄) · 2MeCN (4) have been determined. These ligands with strong-field carboxamido N donor stabilize the +3 oxidation state of the Co center as demonstrated by the facile oxidation of the corresponding Co(II) complexes (prepared in situ) by H₂O₂, [Fe(Cp)₂](BF₄), or nitric oxide (NO). The Co-N_amido bond distances of 1-4 lie in the narrow range of 1.853-1.898 Å. ¹H NMR spectra of these complexes confirm the low-spin d⁶ ground states of the metal centers.     

Aqueous solution chemistry of dichloro[S-methylcysteine(N,S)]platinum(II) isomers and their hydrolysis products

Rate and equilibrium constants at 25 °C, pH ∼ 1, and ionic strength 0.10 for hydrolysis of the two non-equivalent chlorides of dichloro[S-methyl-l-cysteine(N,S)]platinum(II) isomers, denoted [PtCl₂(SmecysH)], and the resultant chloro-aqua species have been determined by NMR, potentiometric, and spectrophotometric methods. Though hydrolysis constants, K_h, for the two chlorides are similar (pK_h = 4-5), the rate of hydrolysis of the chloride trans to coordinated S, k_h = 3.4 × 10⁻³ s⁻¹, is 2-3 orders of magnitude faster than the k_h for the other chloride, 2.3 × 10⁻⁶ s⁻¹, and for the cancer drug cisplatin, cis-[PtCl₂(NH₃)₂], 5.2 × 10⁻⁵ s⁻¹. Relative rates of hydrolysis determined under three different experimental conditions (pH ∼ 1 in 0.10 M HNO₃, high pH in 0.10 M NaOH, and at low pH with Ag⁺ assistance) are consistent: the Cl trans to S is 100-1000 times more labile than the Cl cis to S. Potentiometric and NMR methods were also used to estimate pK_a values of all aqua species, which are comparable to values reported for corresponding aqua species derived from cisplatin.     

Tripodal amine catechol ligands: a fascinating class of chelators for aluminium(III)

Complexation constants based on potentiometric titrations and spectrophotometric measurements in an aqueous medium of 0.1 M KCl at 25 ± 1 °C for the complexes of Al(III) with multidentate tripodal polycatechol-amine ligands, cis,cis-1,3,5-tris[(2,3-dihydroxybenzylamino)aminomethyl]cyclohexane (TMACHCAT, L¹) and N¹,N³,N⁵-tris(2-(2,3-dihydroxybenzylamino)ethyl)cyclohexane-1,3,5-tricarboxamide (CYCOENCAT, L²) have been summarized in this paper. Both the ligands released six protons to form various monomeric complexes of the types AlLH₃, AlLH₂, AlLH and AlL (L = L¹ and L²). The first species AlLH₃ depicted at low pH for which a monocapped type geometry was suggested, where the ligands were coordinated through three catecholic oxygens at ortho. Other species are formed subsequently from the species AlLH₃ in steps upon deprotonation and coordination of the catecholic oxygens at meta to give encapsulated tris(catechol) type complexes. The probable structures of the metal complexes formed in solution were proposed through molecular modeling calculations. The pAl values calculated for AlL¹ and AlL² are appreciably higher than transferrin. The ligand L² showed higher affinity towards Al(III) than L¹ and desferrioxamine (DFO), the only approved drug for the treatment of aluminium intoxication.     

Homogeneous green catalysts for olefin oxidation by mono oxovanadium(V) complexes of hydrazone Schiff base ligands

Three mono oxovanadium(V) complexes of tridentate Schiff base ligands [VO(OMe)L¹] (1), [VO(OMe)L²] (2) and [VO(OMe)L³] (3) obtained by monocondensation of 3-hydroxy-2-naphthohydrazide and aromatic o-hydroxyaldehydes have been synthesized (H₂L¹ = (E)-3-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide, H₂L² = (E)-3-hydroxy-N′-(2-hydroxybenzylidene)-2-naphthohydrazide and H₂L³ = (E)-N′-(5-bromo-2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide). The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV-Vis, ¹H NMR). Single crystal X-ray analyses were performed with 1 and 2. The catalytic potential of these complexes has been tested for the oxidation of cyclooctene using H₂O₂ as the terminal oxidant. The effects of various parameters including the molar ratio of oxidant to substrate, the temperature, and the solvent have been studied. The catalyst 2 showed the most powerful catalytic activity in oxidation of various terminal, cyclic and phenyl substituted olefins. Excellent conversions have been obtained for the oxidation of cyclic and bicyclic olefins.     

Spectrophotometric determination of formation constants for the Cu-ethylenediamine-halogen (chloride and bromide) system and their catalytic effect on the oxidative coupling of 2,6-di-tert-butyl-phenol

In order to explain the mechanism of the dimerization of 2,6-di-tert-butyl-phenol when catalyzed by the copper-ethylenediamine complexes, a spectrophotometric study of the speciation of copper(II) complexes in methanol of Cu(II), ethylendiamine and Cl⁻ or Br⁻ was carried out at 303 K. The formation constants obtained for the copper chloride system are: log β₁₀₁ = 2.90 ± 0.03, log β₁₀₂ = 6.39 ± 0.03 and log β₁₀₃ = 8.62 ± 0.04, for the copper bromide system are log β₁₀₁ = 3.01 ± 0.10, log β₁₀₂ = 5.50 ± 0.08, for the copper-ethylendiamine complexes are log β₁₁₀ = 6.13 ± 0.05 and log β₁₂₀ = 10.54 ± 0.08, and for the ternary copper-ethylenediamine chloride or bromide systems are log β₁₁₁ = 10.21 ± 0.03 and log β₁₁₁ = 10.07 ± 0.03, respectively. Knowing the speciation of the copper-ethylenediamine-halide systems, the kinetic studies can be correlated with the species in solution. Comparative studies of the oxidation reaction of 2,6-di-tert-butyl-phenol using different copper(II) complexes with chloride or bromide and ethylenediamine as catalyst are reported. Their catalytic activity in the oxidation of 2,6-di-tert-butyl-phenol was monitored in methanol solution, following the corresponding quinone formation, at 418 nm (ε = 3.95 × 10⁴ mol⁻¹ L cm⁻¹ at 303 K). The results indicate that the most active species are [Cu(en)X]⁺, where X is bromide or chloride, Both complexes have similar activity.     

Antifungal property of quaternized chitosan and its derivatives

Five water-soluble chitosan derivatives were carried out by quaternizing either iodomethane or N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (Quat188) as a quaternizing agent under basic condition. The degree of quaternization (DQ) ranged between 28 ± 2% and 90 ± 2%. The antifungal activity was evaluated by using disc diffusion method, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) methods against Trichophyton rubrum (T. rubrum), Trichophyton mentagrophyte (T. mentagrophyte), and Microsporum gypseum (M. gypseum) at pH 7.2. All quaternized chitosans and its derivatives showed more effective against T. rubrum than M. gypseum and T. mentagrophyte. The MIC and MFC values were found to range between 125-1000 μg/mL and 500-4000 μg/mL, respectively against all fungi. Our results indicated that the quaternized N-(4-N,N-dimethylaminocinnamyl) chitosan chloride showed highest antifungal activity against T. rubrum and M. gypseum compared to other quaternized chitosan derivatives. The antifungal activity tended to increase with an increase in molecular weight, degree of quaternization and hydrophobic moiety against T. rubrum. However, the antifungal activity was depended on type of fungal as well as chemical structure of the quaternized chitosan derivatives.     

A rhodium(I) complex containing a mixed donor `P2N' tridentate ligand

The reaction of 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCHP) with 0.5 equivalents of [{RhCl(1,5-cyclooctadiene)}₂] affords the extremely, air-sensitive compound, [RhCl(PNCHP-κ³P,N,P)]. This reacts with carbon monoxide to afford [RhCl(CO)(PNCHP-κ³P,N,P)] which rearranges in dichloromethane solution to [Rh(CO)(PNCHP-κ³P,N,P)]Cl · HCl. The single crystal structure of [Rh(CO)(PNCHP-κ³P,N,P)]Cl · HCl shows the Rh to be in a square planar environment with the HCl molecule held via hydrogen bonding in the lattice. NMR experiments show the coordinated chloride in [RhCl(PNCHP-κ³P,N,P)] can be substituted with tetrahydrofuran, acetonitrile or triphenylphosphine and the complex undergoes oxidative addition with dichloromethane to yield [Rh(CH₂Cl)Cl₂(PNCHP-κ³P,N,P)].     

Synthesis and structural characterization of copper(II) bishexafluoroacetylacetonate complexes with N-donor ligands

The reactions of Cu(hfac)₂ with different N-donor ligands such as 2-ethynylpyridine and imidazole give copper complexes Cu(hfac)₂(ethynylpyridine) (1) and Cu(hfac)₂(ImH)₂ (2), respectively. The reaction of Cu(hfac)₂ · (ethynylpyridine) (1) and ethynylpyridine with oxygen in tmeda (tmeda = N,N,N′,N′-tetramethylethylenediamine) in the presence of copper(I) chloride gives Cu(hfac)₂(tmeda) (3). Finally, [Cu(hfac)₂(H₂O)]₂(μ-TCNE) (4) was prepared by reaction of Cu₂O on the free acid β-diketone in the presence of TCNE (TCNE = tetracyanoethylene) (ratio 1.5:1:1), under an atmosphere of oxygen-free Ar. The previously synthesized Cu(hfac)TCNE proceeded further reaction by disproportionation, yielding [Cu(hfac)₂(H₂O)]₂(μ-TCNE). All new compounds have been structurally characterized and their thermal properties were examined by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Synthesis and coordination behaviors of 14-membered tetraaza macrocyclic copper(II) complexes bearing two N-propionic acid or N-propionic methyl ester groups

A di-N-functionalized 14-membered tetraaza macrocycle, [H₄L³](ClO₄)₂ (L³ = 1,8-bis(2-carboxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane), has been synthesized by acid hydrolysis of 1,8-bis(2-cyanoethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L²). The copper(II) complexes [CuL²](ClO₄)₂ and [Cu(H₂L³)](ClO₄)₂ were prepared and characterized. The complex [Cu(H₂L³)]²⁺ readily reacts with methanol to yield [CuL⁴]²⁺ (L⁴ = 1,8-bis(2-carbomethoxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane). The N-CH₂CH₂COOH groups of [Cu(H₂L³)](ClO₄)₂ are not coordinated to the metal ion in the solid state but are involved in coordination in various non-aqueous solvents or in aqueous solutions of pH ? 1.0. Interestingly, [CuL⁴](ClO₄)₂ exists as two stable structural isomers, 1 (the pendant ester groups are not involved in coordination) and 2 (one of the two ester groups is coordinated to the metal ion), in the solid state; the two isomers can be prepared selectively by controlling ionic strength of a methanol solution of the complex. Crystal structures and coordination behaviors of the two isomers are described. The di-N-cyanoethylated macrocyclic complex [CuL²](ClO₄)₂ is rapidly decomposed in 0.1 M NaOH solution even at room temperature. On the other hand, [Cu(H₂L³)](ClO₄)₂ and [CuL⁴](ClO₄)₂ are quite inert against decomposition under similar basic conditions. In acidic or basic aqueous solutions, [CuL⁴]²⁺ is hydrolyzed to [Cu(H₂L³)]²⁺ or [CuL³].     

Preparation and characterization of manganese(III) halide derivatives of N,N′-bis(aminobenzylidene)-1,2-ethanediamine

The preparation and characterization of manganese(III) complexes containing the quadridenate ligand, N,N′-bis(aminobenzylidene)-1,2-ethanediamine (H₂amben), and its previously unreported analogue, N,N′-bis(2-amino-5-nitro-benzylidene)-1,2-ethanediamine (H₂nitroamben), are described. The new manganese(III) halide/pseudohalide complexes, Mn(amben)X · nH₂O and Mn(nitroamben)X · nH₂O (X = Cl, Br, I, NCS; n =  0.5 or 1), were isolated as red-brown, microcrystalline solids, which were characterized fully.     

A valence electron rule for the regular octahedrons of M6 clusters

A valence electron rule is proposed for the stability of the regular octahedrons of the M₆ clusters of high-row representative elements in the singlet states. The 6N + 14 (N = 0-2) valence electrons stabilize the O_h geometry. The 6N + 14 valence electron rule is confirmed by the unrestricted density functional theory calculations at the UB3LYP/6-31+G(d) levels.     

An efficient catalytic dehydration of fructose and sucrose to 5-hydroxymethylfurfural with protic ionic liquids

The renewable furan-based platform chemical, 5-hydroxymethylfurfural (HMF), has been efficiently synthesized from d-fructose and sucrose in the presence of a catalytic amount of protic ionic liquids. The 1-methylimidazolium-based and N-methylmorpholinium-based ionic liquids are employed. As a result, 74.8% and 47.5% yields of HMF are obtained from d-fructose and sucrose, respectively, at 90 °C for 2 h under nitrogen atmosphere when N-methylmorpholinium methyl sulfonate ([NMM]⁺[CH₃SO₃]⁻) is used as the catalyst in an N,N-dimethylformamide-lithium bromide (DMF-LiBr) system. The acidities of ionic liquids are determined by the Hammett method, and the correlation between acidity and catalytic activity is discussed. Moreover, the effects of reaction temperature and time are investigated, and a plausible reaction mechanism for the dehydration of d-fructose is proposed.     

Synthesis, characterization and cytotoxic properties of platinum(II) complexes containing the nucleosides adenosine and cytidine

Cytidine (cyt) and adenosine (ado) react with cis-[L₂Pt(μ-OH)]₂(NO₃)₂ (L = PMe₃, PPh₃) in various solvents to give the nucleoside complexes cis-[L₂Pt{cyt(− H),N³N⁴}]₃(NO₃)₃ (L = PMe₃, 1),cis-[L₂Pt{cyt(− H),N⁴}(cyt,N³)]NO₃ (L = PPh₃, 2), cis-[L₂Pt{ado(− H),N¹N⁶}]₂(NO₃)₂ (L = PMe₃, 3) and cis-[L₂Pt{ado(− H),N⁶N⁷}]NO₃ (L = PPh₃, 4). When the condensation reaction is carried out in solution of nitriles (RCN, R = Me, Ph) the amidine derivatives cis-[(PPh₃)₂PtNH=C(R){cyt(− 2H)}]NO₃ (R = Me, 5a; R = Ph, 5b) and cis-[(PPh₃)₂PtNH=C(R){ado(− 2H)}]NO₃ (R = Me, 6a: R = Ph, 6b) are quantitatively formed. The coordination mode of these nucleosides, characterized in solution by multinuclear NMR spectroscopy and mass spectrometry, is similar to that previously observed for the nucleobases 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd). The cytotoxic properties of the new complexes, and those of the nucleobase analogs, cis-[(PPh₃)₂PtNH=C(R){1-MeCy(− 2H)}]NO₃ (R = Me, 7a: R = Ph, 7b), cis-[(PPh₃)₂PtNH=C(R){9-MeAd(− 2H)}]NO₃ (R = Me, 8a: R = Ph, 8b) have been investigated in a wide panel of human cancer cells. Interestingly, whereas the Pt(II) nucleoside complexes (1-4) did not show appreciable cytotoxicity, the corresponding amidine derivatives (7a, 7b, 8a, 8b, 5b, and 6b) exhibited a significant in vitro antitumor activity.