Redox-responsive vesicles prepared from supramolecular cyclodextrin amphiphiles

Redox-responsive vesicles self-assembled by supramolecular cyclodextrin amphiphiles, consisting of the guest (N-1-decyl-ferrocenylmethylamine, 1) and the host (2-O-carboxymethyl-β-cyclodextrin, CM-β-CD), were prepared. The morphologies and sizes of these novel vesicles in an aqueous solution were observed by transmission electron microscopy (TEM) and were confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS) measurements. The effects of the host-guest ratio, the concentration and the solvent composition of water and methanol on vesicles were investigated in detail. The interactions between the host and the guest, the complex stoichiometry, the stability constant and conformations of 1·CM-β-CD in aqueous solution were investigated by cyclic voltammetry (CV), UV and nuclear magnetic resonance (NMR) measurements. According to the complex stoichiometry and ‘tadpole-like’ spatial conformations, the supramolecular cyclodextrin amphiphiles made from 1·CM-β-CD were proposed to form the membranes of the vesicles. This kind of vesicle system was responsive to an oxidizing agent, which could pave the way to combine supramolecular host-guest chemistry and membrane chemistry for potentially functional applications.     

Mononuclear diastereopure non-heme Fe(II) complexes of pentadentate ligands with pyrrolidinyl moieties: Structural studies, and alkene and sulfide oxidation

Mononuclear iron(II) complexes of enantiopure Py(ProOH)₂ (2) and Py(ProPh₂OH)₂ (3) ligands have been prepared with FeCl₂ and Fe(OTf)₂ · 2MeCN. Both ligands coordinate to the metal in a pentadentate fashion. Next to the meridional N,N′,N-coordination of the ligand, additional coordination of the oxygen atoms of both hydroxyl groups to the metal is found in complexes 4-7. Complex [FeCl(2)](Cl) (4) shows an octahedral geometry as determined by X-ray diffraction and is formed as a single diastereoisomer. The solution structures of complexes 4-7 were characterized by means of UV-Vis, IR, ESI-MS, conductivity and CD measurements. The catalytic potential of these complexes in the oxidation of alkenes and sulfides in the presence of H₂O₂ is presented.     

Reversible vesicles based on one and two head supramolecular cyclodextrin amphiphile induced by methanol

Reversible vesicles based on supramolecular inclusion of hydroxypropyl-β-CD (HPβCD) and N,N′-bis(ferrocenylmethylene)-diaminohexane (BFD) were prepared in water and methanol-water mixtures. The inclusion stoichiometry of HPβCD with BFD was in a molar ratio of 2:1, which could be named as ‘two head’ supramolecular amphiphile when the solvent was water. However, the inclusion stoichiometry of HPβCD with BFD would tend to be a molar ratio of 1:1 based on introduction of methanol to the solvent, especially when the volume ratio of methanol and water was more than 1:4, which could be named as ‘one head’ supramolecular amphiphile. The inclusion compounds could switch between ‘one head’ and ‘two head’ conformations by changing the methanol concentration of the solvents. The vesicles were also found to be responsive to the stimulus of external molecules. When the inclusion ability between HPβCD and an external guest was relatively stronger, the vesicles were easily destroyed. Furthermore, the vesicles disappeared after adding an oxidizing agent. NMR was used to confirm the conformation of the mixture of HPβCD and BFD in water. The structure and morphology of the vesicles were characterized by TEM and DLS. The vesicles may be used in smart materials, drug delivery and molecular recognition.     

Crystal structure and solid-state 13C NMR analysis of N-o-, N-m- and N-p-nitrophenyl-2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosylamines, and their N-acetyl derivatives

The X-ray diffraction analysis of N-o-nitrophenyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranosylamine (1), N-m-nitrophenyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranosylamines, N-p-nitrophenyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranosylamines, and their N-acetyl derivatives was performed. The sugar moieties always adopt ⁴C₁ conformations, however, due to crystal packing forces they are always slightly distorted. It was found that except N-acetyl, N-m-nitrophenyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranosylamine (5), none of the glucopyranosylamines studied in this paper form strong hydrogen bonds in the crystal lattice. Additionally, (5) crystallizes with a molecule of water, which occupies a special crystallographic position (on the twofold axis) and links two sugar molecules by hydrogen bonds. The CP MAS NMR spectra confirmed the presence of the intermolecular hydrogen bond involving the molecule of water in (5). Moreover, it was proved that in (1) an intramolecular hydrogen bond is formed between the glycosidic linkage and the nitro group.     

Synthesis and antimicrobial activity of some new N-glycosides of 2-thioxo-4-thiazolidinone derivatives

5-Arylidene-2-thioxo-4-thiazolidinones 3a-f react with each of 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl and α-d-galactopyranosyl bromides 4a,b in acetone in the presence of aqueous potassium hydroxide at room temperature to afford N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl) or N-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl) 2-thioxo-4-thiazolidinone derivatives 5a-f. Similarly, the reaction of 5-cycloalkylidene-2-thioxo-4-thiazolidinones 7a,b with 4a gave the corresponding N-glucosides 8a,b. Also, 5-pyrazolidene rhodanines 10a-e react with 4a to afford the new N-glucosides 11a-e. Treatment of compounds 15 and 16 with 4a in the presence of few drops of triethylamine or in KOH solution accomplished the mono- and bis-nucleosides 17 and 18, respectively. Some selected products were tested for their antimicrobial activities.     

Synthesis, characterization of [{(N-methyl-N-benzyl)amino}methyl]ferrocenes and their cyclopalladated complexes: Crystal structure of σ-Pd[(η-C5H5)Fe(η-C5H3CH2N(CH3)CH2C6H4NO2-4)]Cl(PPh3)

Condensation of aminomethylferrocene (1) and substituted benzaldehydes resulted in aldimines 2a-c which followed by reduction with sodium borohydride to give 3a-c. N-methylation of 3a-c with HCHO/NaCNBH₃/HOAc led to 4a-c. Treatment of 4a-c with sodium palladium tetrachloride in the presence of sodium acetate afforded cleanly cyclopalladated 5a-c in which configurations consisted of the R_NR_C, S_NS_C. The preferable activation of C_Ferrocenyl-H bond over C_Phenyl-H bond was also observed. All compounds 2-5 were characterized by elemental analysis, IR and ¹H NMR. In addition, the molecular structure of 5c was confirmed by single crystal X-ray diffraction. The possible mechanism for the formation of 5 was also discussed.     

Chiral 2-pyridyl alcoholate copper complexes: crystal structures of [bis(2-pyridyl alcoholate)copper(II)] and the use of [(2-pyridyl alcoholate)copper(II)]and [(2-pyridyl alcoholate)copper(I)] in asymmetric cyclopropanation of styene and allylic oxidation of cyclohexene

Chiral N,O pyridine alcohols HL¹-HL⁶ were used to form complexes with copper(II) ions. Ligands HL¹ and HL² formed complexes with copper(II) ions when Cu(OAc)₂ and HL were refluxed in methanol/ethanol mixture. Ligand HL³ formed a complex with copper(II) when deprotonated with NaH and stirred in a Cu(II) acetate THF solution. Ligands HL⁴-HL⁶ did not form complexes with copper(II) under similar conditions. Two complexes, [Cu(L¹)₂] and [Cu(L²)₂], were isolated as single crystals and characterized by X-ray crystallography. These complexes showed low catalytic activities in asymmetric reactions. However, they became active when reacted with triflic acid. Copper complexes, [Cu(L)] or [Cu(L)]⁺, formed in situ by reacting ligands HL with copper(I) or (II) ions, respectively, were also found to be active copper catalysts for asymmetric cyclopropanation of styrene with ethyl diazoacetate and allylic oxidation of cyclohexene with t-butylperoxybenzoate. Enantioselectivities up to 56% and 38% were obtained in asymmetric cyclopropanation of styrene and asymmetric allylic oxidation of cyclohexene, respectively.     

2-(1-(Dimethylamino)ethyl)phenylpalladium(II) complexes 5-functionalized with fluorous silyl tails

New fluorous-organometallics based on the chiral ligand α-methyl-N,N-dimethylbenzylamine (TMBA) were prepared by treatment of fluorous silyl bromide reagents with in situ 4-lithiated TMBA to give fluorous N,N-dimethyl(α-methyl-4-trialkylsilylbenzyl)amine ligands 1a-1c that vary in the number of fluorous tails attached to the Si atom. Ligands 1a-1c were successfully cyclo-palladated by treatment with Pd(OAc)₂/LiCl in methanol to furnish the corresponding chloride-bridged dimeric arylpalladium(II) complexes 2a-2c in good yields. The latter derivatives could be converted into monomeric Lewis-base adducts by complexation with pyridine (3a-3c), or triphenylphosphine (4a-4c). The crystal structure of triphenylphosphine complex 4a has been elucidated. To probe their fluorophilicity, the partition coefficient of each of the derivatives in the fluorous biphasic solvent (FBS) system perfluoromethylcyclohexane/n-octane has been determined.     

Cyanato bridged binuclear nickel(II) and copper(II) complexes with pyridylpyrazole ligand: Synthesis, structure and magnetic properties

Binuclear cyanate bridged nickel(II) complex [Ni(L)(NCO)]₂(PF₆)₂ (1) and copper(II) complex [Cu(L)(NCO)]₂(PF₆)₂ (2), where L is N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine, a tetradentate N₄-coordinated ligand have been synthesized and characterized by physicochemical method. The structures of complexes 1 and 2 have been studied by single crystal X-ray diffraction analysis. The structure analysis reveals that both nickel(II) and copper(II) center are coordinated in distorted octahedral fashion and coordination mode of cyanate ligand is end-to-end (μ-1,3) for complex 1 but it is double end-on (μ-1,1) mode for complex 2. The variable temperature magnetic susceptibility data, measured from 2 to 300 K, show weak antiferromagnetic interaction with J value −6.2(1) cm⁻¹ for complex 1, whereas complex 2 has very weak ferromagnetic interaction with J value +0.5(1) cm⁻¹.     

Discovery of novel ureas and thioureas of 3-decladinosyl-3-hydroxy 15-membered azalides active against efflux-mediated resistant Streptococcus pneumoniae

A series of novel ureas and thioureas of 3-decladinosyl-3-hydroxy 15-membered azalides, were discovered, structurally characterized and biologically evaluated. They have shown good antibacterial activity against selected Gram-positive and Gram-negative bacterial strains. These include N″ substituted 9a-(N′-carbamoyl-γ-aminopropyl)- (6a,c), 9a-(N′-thiocarbamoyl-γ-aminopropyl)- (7a,e), 9a-[N′-(β-cyanoethyl)-N′-(carbamoyl-γ-aminopropyl)]- (9a-c, 9g) 9a-[N′-(β-cyanoethyl)-N′-(thiocarbamoyl-γ-aminopropyl)]-derivatives (10d-f) of 5-O-desosaminyl-9-deoxo-9-dihydro-9a-aza-9a-homoerythronolide A (3).Among the synthesized compounds thiourea 7a and urea 9b have shown substantially improved activity comparable to azithromycin (1) and significantly better activity than the 3-decladinosyl-azithromycin (2) and the parent 3-cladinosyl analogues against efflux-mediated resistant S. pneumoniae.     

Manganese(II) complexes of a set of 2-aminomethylpyridine-derived ligands bearing a methoxyalkyl arm: syntheses, structures and magnetism

Four new ligands, N-(2-methoxyethyl)-N-(pyridin-2-ylmethyl)amine (mepma), N-(3-methoxypropyl)-N,N-bis(pyridin-2-ylmethyl)amine (mpbpa), N-(2-methoxyethyl)-N,N-bis(pyridin-2-ylmethyl)amine (mebpa) and 2-{[(2-methoxyethyl)(pyridin-2-ylmethyl)amino]methyl} phenol (Hmepap), and four of their complexes with manganese(II) halides, [MnCl₂(mepma)₂] (1), [MnCl(μ-Cl)(mpbpa)]₂ (2), [MnBr₂(mebpa)] (3) and [MnBr₂(MeOH)(Hmepap)] (4) have been synthesized and characterized. Single-crystal Xray studies revealed that in all four complexes, the Mn(II) coordination spheres are distorted octahedral. In 1 and 2, the ether oxygen atom does not coordinate to the Mn(II) centre, but in 3 and 4 it does. The mononuclear molecules of 1 are linked by double hydrogen bonds to form linear chains. Temperature dependent magnetic susceptibility measurements revealed that the Mn(II) ions in 1 interact antiferromagnetically, with J=−1.06 cm⁻¹. Compound 2 crystallizes as a double chloride-bridged dimer in which there is a weak ferromagnetic interaction (J=0.55 cm⁻¹) between the Mn(II) pair. The solution EPR spectrum of 2 suggests that in methanol compound 2 decomposes to a great extent to mononuclear species. In compound 3, mebpa acts as a tetradentate ligand with all of its nitrogen and oxygen atoms coordinated to the Mn(II) ion. Unexpectedly, in complex 4, the phenolic oxygen of Hmepap remains protonated and does not coordinate to the metal ion. Instead the oxygen from a methanol molecule coordinates the manganese centre. Hydrogen bonds between one of the two bromide ions, and the methanol and phenol hydroxyl groups, respectively, connect the mononuclear molecules of 4 into chains. No magnetic interactions were observed between the Mn(II) ions in 3 or 4.     

Regioselectivity in the glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol

The glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol (1) and its 3-benzylsulfanyl and 3-methylsulfanyl derivatives with different glycosyl halides 2-4 has been studied in presence of base. The S-glycosides 5-7 were obtained in the presence of triethylamine, whereas the respective S,N⁴-bis(glycosyl) derivatives 8-10 were synthesized in the presence of potassium carbonate; the S,N²-bis(glycosyl) isomer 11 could also be isolated in the case of the galactosyl analog. Similarly, after protecting 1 as 3-benzyl(methyl)sulfanyl derivatives 12 or 13, the N⁴-glycosyl analogs 14-19 as well as minor amounts of S,N²-bis(galactosyl) isomers 20 and 21 were formed. The theoretical calculations using AM1 semiempirical methods agreed with the experimental results. Microwave irradiation (MWI) led to higher yields in much less time than the conventional methods, and no change in regioselectivity has been noticed.     

Diverse reactivity of stereoisomers containing quadruply bonded dimolybdenum with oxygen: formation of [{Mo(η-N,N′-diisopropylbenzamidinato)oxo}2(μ-acetato)2(μ-oxo)]

The reaction of quadruply bonded dimolybdenum complex, [Mo₂(μ-OAc)₄] (1), with lithiated amidinato, Li[(NⁱPr)₂CR] (R = ^tBu; 2a, Me; 2b, Ph; 2c), was investigated. The reaction of 1 with 2a afforded the dark-red solid, whereas the product was so highly unstable that the product was not able to be characterized. In the case of acetamidinato 2b, lantern-type mixed-ligand quadruply bonded dimolybdenum complex, [Mo₂(μ-OAc){μ-(NⁱPr)₂CMe}₃] (3), was obtained as a yellow solid. In the reaction with benzamidinato 2c, symmetrical lantern-type dimolybdenum complex, [Mo₂(μ-OAc)₂ {μ-(NⁱPr)₂CPh}₂] (4), was isolated as a yellow solid. In the latter reaction, intermediary red compound (5), which is considered to be stereoisomer of 4 possessing non-lantern-type skeleton, was formed. However, isolation of 5 as a single component was not successful due to isomerization to 4. Complex 5 readily reacted with dry oxygen to give dimolybdenum(V) complex, [{Mo(η-(NⁱPr)₂CPh)oxo}₂ (μ-OAc)₂(μ-oxo)] (6), as a red solid. These complexes were characterized spectroscopically as well as, in some cases, by X-ray analyses.     

Synthesis of iminoalditol and N-alkyl iminoalditol derivatives of ribopyranosides

Iminoalditol analogs of ribopyranosides were prepared by reduction of a vinylogous urethane intermediate formed from methyl 2-C-(5-O-methanesulfonyl-β-d-ribofuranosyl)acetate (1) by treatment with sodium azide in DMF at reflux. The N-alkylated analogs were synthesized either by N-alkylation of the corresponding parent iminoaldithol or, more efficiently, from the product of the reaction of 1 with various alkylamines. The latter process involves an S_N2 substitution at C-5 by the amine followed by an intramolecular hetero-Michael reaction under basic conditions. The ‘aglycon’ of the iminoalditol was also modified through amidation and esterification.     

Salicylamide and salicylglycine oxidovanadium complexes with insulin-mimetic properties

Reaction of N-(2-hydroxybenzyl)-N-(2-picolyl) glycine (H₂papy) with VOSO₄ in water gives the oxidovanadium(V) oxido-bridged dimer [{(papy)(VO)}₂ μ-O)] (1). Similarly, reaction of N-(2-hydroxybenzyl) glycine (H₂glysal) with VOSO₄ gives [(glysal)VO(H₂O)] (2) and reaction of salicylamide (Hsalam) with VOSO₄ in methanol gives [(salam)₂VO] (3). The crystal structure of the oxido-bridged complex 1 is reported. The insulin-mimetic activity of all three complexes was evaluated with respect to their ability to phosphorylate protein kinase B (PKB). The speciations of complexes 1 and 2 were studied over the pH range 2-10. Complex 1 shows greater stability over the whole pH range but only 2 and 3 exhibit an insulin-mimetic effect.     

Coordination chemistry of anticrowns: Synthesis and X-ray crystal structure determination of the polydecker sandwich complexes of cyclic trimeric perfluoro-o-phenylenemercury with azulene and 6-(N,N-dimethylamino)pentafulvene

The interaction of cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) with azulene results in the formation of a complex, {[(o-C₆F₄Hg)₃](azulene)} (2), containing one molecule of azulene per one macrocycle molecule. The complex represents a polydecker sandwich wherein the azulene units alternate with the molecules of the mercury anticrown. The reaction of 1 with 6-(N,N-dimethylamino)pentafulvene (DMAPF) also gives a 1:1 complex, {[(o-C₆F₄Hg)₃](DMAPF)} (3), having a polydecker sandwich structure in the crystal. In complex 2, both the C₅ and C₇ rings of the azulene ligand are involved in the bonding to the Hg sites of 1. In complex 3, the C₅ ring of the fulvene ligand together with its exocyclic carbon atom take part in the coordination to the mercury centres. In both adducts, the negatively charged five-membered ring of the azulene and, correspondingly, the fulvene moieties is arranged in the space between the central Hg₃C₆ rings of the adjacent macrocycles while the remaining portion of these moieties is disposed outside this space. The molecules of azulene and DMAPF in 2 and 3 are bonded to 1 through donation of their π-electrons on vacant orbitals of the Hg atoms. The synthesized 2 and 3 are the first examples of structurally characterized complexes of azulene and DMAPF with a non-transition metal compound.     

Synthesis, crystal structure and magnetic properties of a one-dimensional Mn(III) Schiff-base complex bridged by derivative of tetracyano-p-quinodimethane

A new one-dimensional manganese(III) Schiff-base complex [Mn(III)(salophen) (MeOTCNQ)] · CH₃CN 1 (salophen = N,N′-bis(salicylidene)phenylenediamine) bridged by 7-methoxy-7,7,8,8-tetra-cyano-p-quinodimethane (MeOTCNQ), has been synthesized and characterized by X-ray crystallography and magnetic studies. Crystal structure study reveals that complex 1 has a 1D manganese(III) chain bridged by MeOTCNQ ligand which was obtained unexpectedly from tetracyano-p-quinodimethane (TCNQ) reacting with methanol. Noticeably, MeOTCNQ molecules in complex 1 adopt an unusual cis-syn coordination mode. The analysis of magnetic data indicates that a weak intrachain antiferromagnetic interaction exists in complex 1.     

Phenolic compounds and rare polyhydroxylated triterpenoid saponins from Eryngium yuccifolium

Phytochemical investigation on the whole plant of Eryngium yuccifolium resulted in the isolation and identification of three phenolic compounds (1-3) and 12 polyhydroxylated triterpenoid saponins, named eryngiosides A-L (4-15), together with four known compounds kaempferol-3-O-(2,6-di-O-trans-p-coumaroyl)-β-d-glucopyranoside (16), caffeic acid (17), 21β-angeloyloxy-3β-[β-d-glucopyranosyl-(1→2)]-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosyloxyolean-12-ene-15α,16α,22α,28-tetrol (18), and saniculasaponin III (19). This study reports the isolation of these compounds and their structural elucidation by extensive spectroscopic analyses and chemical degradation.     

Synthesis, structure, sorption and magnetic properties of Ni(II) and Cu(II) complexes with thiosemicarbazone of 2-hydroxybenzaldehyde, bridged by 4,4′-bipyridine

(ML)₂(bipy) complexes (LH₂ = thiosemicarbazone of 2-hydroxybenzaldehyde, bipy = 4,4′-bipyridine, M = Ni(II), 1, or Cu(II), 2) were synthesized and characterized by X-ray crystallography. Compound 1 possessed porous structure due to peculiarities of crystal packing, whereas 2 formed infinite zig-zag chains with dense non-porous packing. It was shown that 1 absorbed 0.013 cm³/g of methanol vapor in two steps. Complex 1 was diamagnetic; for 2, the dependency of χ versus T could be interpreted by Bleaney-Bowers expression in 20-300 K temperature range (J = −6.8 cm⁻¹, g = 2.07).     

Synthesis and characterization of gallium complexes bearing N-arylmethylenethiobenzahydrazone ligands; crystal structure of diethyl[N-(4-N,N-dimethylamino)benzylidene thiobenzahydrazonato]gallium

Five diethylgallium complexes of type Et₂GaL [(L = N-(4-methoxy) benzylidenethiobenzahydrazonato (1), N-(3,4-dimethoxy)benzylidenethio benzahydrazonato (2), N-(4-N,N-dimethylamino)benzylidenethiobenza hydrazonato (3), N-(2-naphthyl)methylenethiobenzahydrazonato (4), N-(9-anthryl)methylenethiobenzahydrazonato (5)] have been synthesized by the reaction of triethylgallium with appropriate N-arylmethylene thiobenzahydrazones. The compounds obtained have been characterized by elemental analysis, ¹H NMR, IR and mass spectroscopies, respectively. The solid structure of 3 has been determined by X-ray single crystal analysis, in which Ga atom is four coordinate. The photoluminescent property of complex 1 was studied. The maximum emission wavelength is 475 nm upon radiation by UV light.