Characterization of viscose fibers modified with 6-deoxy-6-amino cellulose sulfate

Cellulose viscose fibres were functionalized by novel amino cellulose sulfates (ACS), namely 6-deoxy-6-(ω-aminoethyl) amino cellulose-2,3(6)-O-sulfate (AECS), and 6-deoxy-6-(2-(bis-N′,N′-(2-aminoethyl)aminoethyl)) amino cellulose-2,3(6)-O-sulfate (BAECS). In this way an amphoteric characteristics were introduced onto cellulose viscose fibers which is extremely important by fiber applications. Whilst cellulose fibers possess only negligible carboxyl groups’ content, the coating of fibers by AECS and BAECS, respectively, introduces new functional groups to the fibers; as positively-charged amino groups and negatively-charged sulfate groups. The typical functional groups within the non-coated fibers, as well in the ACS-coated fibers, were characterized by means of X-ray photoelectron spectroscopy, conductometric-, potentiometric and polyelectrolyte titrations, as well as conventionally by the spectroscopic methylene-blue method. The electro-kinetic behavior was evaluated by measuring the zeta-potential of the fibers as a function of pH. The amounts of the positive-charges (introduced protonated amino groups) determined by potentiometric titration agreed with the amounts of the positive charges determined by conductometric titration. The total amounts of negatively-charged fiber groups (sulfate and carboxyl) determined by polyelectrolyte titration were 38.8 and 32.1 mMol kg^?1 for AECS-Vis and BAECS-Vis, respectively, and these results were in accordance with the conventional methylene-blue method.     

Synthesis and characterization of aminocellulose sulfates as novel ampholytic polymers

Amino cellulose sulfate (ACS); namely 6-deoxy-6-(ω-aminoethyl) amino cellulose-2,3(6)-O-sulfate (AECS) and 6-deoxy-6-(2-(bis-N′,N′-(2-aminoethyl)aminoethyl)) amino cellulose-2,3(6)-O-sulfate (BAECS) were prepared by a three step synthesis starting with the functionalization of microcrystalline cellulose with p-toluenesulfonyl (tosyl) groups (degree of substitution, DS_Tos between 0.55 and 1.37). Subsequently the introduction of the sulfate moieties was carried out (DS_Sulf between 1.09 and 1.27) and the tosyl groups at position 6 were replaced by a nucleophilic substitution reaction. As nucleophilic agents 1,2-diaminoethane and tris-(2-aminoethyl)amine were applied, yielding AECS (DS_AEA values between 0.41 and 0.86) and BAECS (DS_BAEA values between 0.32 and 0.74), respectively. The ACS samples were characterized by means of elemental analysis, ¹³C-NMR-, FT-IR-, and UV–Vis spectroscopy. Moreover, the solubility of the samples in water at different pH values and the molecular weights of the samples in aqueous solution were studied.     

Synthesis and H+, Cu2+, and Zn2+ coordination behavior of a bis(fluorophoric) bibrachial lariat aza-crown

The synthesis, protonation behavior, and Cu2+ and Zn2+ coordination chemistry of the novel bibrachial aza lariat ether (naphthalen-1-ylmethyl)[2-(20-[2-[(naphthalen-1-ylmethyl)amino]ethyl]-3,6,9,17,20,23,29,30-octaazatricyclo[23.3.1.1*11,15*]triaconta-1(29),11(30),12,14,25,27-hexaen-6-yl)ethyl]amine (L) are discussed. The macrocycle, which has two aminoethyl naphthyl moieties symmetrically appended to a 2:2 azapyridinophane structure, displays, in the pH range 2-11, six protonation steps that correspond to the protonation of the secondary amino groups. Steady-state fluorescence measurements show emissions due to the monomer and to the excimer formed between the two naphthalene fragments of the macrocycle. The time-resolved fluorescence data, obtained by the time-correlated single photon counting technique, show that a significant percentage of excimer is preformed as ground-state dimers. The ligand L forms with the metal ions Cu2+ and Zn2+ mono- and dinuclear complexes in aqueous solution. The influence of metal coordination in the fluorescence emission of L is analyzed. The acid-base, coordination capabilities, and emissive behavior of L are compared with those presented by its synthetic precursor L1, which has a tripodal tris(2-aminoethyl)amine structure functionalized at one of its terminal amino groups with a naphthyl moiety.     

Synthesis of a novel cyclodextrin dimer linked by a macrocyclic polyamine

The first example of cyclodextrin dimer appending a macrocyclic polyamine spacer on the primary faces was synthesized via two approaches: 1,a direct reaction of l,7-bis(2'-aminoethyl)-4,10-dimethyl-l,4,7,10-tetraazacyclododecane (1) with an excess of 6-deoxy-6-O-tosyl-β-cyclodextrin; 2,a condensation of 1 with two equivalents of 6-deoxy-6-formyl-β-cyclodextrin,which was followed by a reduction with NaBH4.     

Histamine-modified cationic beta-cyclodextrins as chiral selectors for the enantiomeric separation of hydroxy acids and carboxylic acids by capillary electrophoresis.

The enantiomeric separation of alpha-hydroxy acids and carboxylic acids was successfully performed by using 6-deoxy-6-N-histamino-beta-cyclodextrin (CD-hm), a monosubstituted positively charged beta-cyclodextrin (beta-CD) bearing a histamine moiety linked to the C6 of a glucose unit in the upper CD rim via the amino group. Good results were obtained at a low selector concentration (1 mM). The number of positive charges on the upper rim may be modulated as a function of pH, because of the different pKa of the amino and the imidazolyl groups, and was found to affect both the enantioselectivity and resolution factors. With the analogous 6-deoxy-[4-(2-aminoethyl)imidazolyl]-beta-cyclodextrin (CD-mh) bearing the histamine moiety linked to the C6 via the imidazolyl group, very poor results were obtained, showing that the proximity of the positive charge to the cavity plays an important role in the enantiomeric recognition. The complexation mode was studied by electrospray ionization-mass spectrometry (ESI-MS) and two-dimensional nuclear magnetic resonance (2-D NMR) ROESY experiments: the recognition model is consistent with an inclusion complexation of the aromatic ring of the analyte within the CD cavity coupled to electrostatic interactions between the carboxylate and the protonated amino group of the cyclodextrin.     

Novel Biopolymer Structures Synthesized by Dendronization of 6‐Deoxy‐6‐aminopropargyl cellulose

Propargyl cellulose with regioselective functionalization pattern was synthesized by nucleophilic displacement reaction of 6‐O‐toluenesulfonyl ester of cellulose (degree of substitution, DS 0.58) with propargyl amine. The novel 6‐deoxy‐6‐aminopropargyl cellulose provides an excellent starting material for the selective dendronization of cellulose at position 6 via the copper‐catalyzed Huisgen reaction yielding 6‐deoxy‐6‐amino‐(4‐methyl‐[1,2,3‐triazolo]‐1‐propyl‐polyamido amine) cellulose derivatives of first‐ (DS 0.33) and second (DS 0.25) generation, which are soluble in polar aprotic solvents. The novel biopolymer derivatives were characterized by elemental analysis, FT‐IR spectroscopy, and one‐ and two dimensional NMR spectroscopy, showing no side reactions (cross‐linking) or impurities and no conversion at the secondary positions.

     

The photophysics of a luminescent ruthenium polypyridyl complex with pendant β-cylodextrin; pH modulation of lifetime and photoinduced electron transfer

At room temperature, [Ru(bpy)₂(phen-CD)][PF₆]₂, (phen-CD is 6 ^A -(5-amino-1, 10-phenanthroline)-6 ^A -deoxy- β-Cyclodextrin and bpy is 2,2'-bipyridine) exhibits an intense metal ligand charge transfer (MLCT) transition at 452 nm and a long lived luminescence, centred at 618 nm. We demonstrate, for the first time, that the luminescence quantum yield and lifetime of the Ru (II) polypyridyl centre depends markedly on the solution pH. The pH sensitive range extends from pH 3.9 to pH 13.2 and the luminescence quantum yield changes by more than 60% over this range. This pH sensitivity is attributed to protonation/deprotonation of the secondary amine group bridge between the phenanthroline unit and CD. The complex exhibits strong host-guest binding to anthraquinone and anthraquinone-2-carboxylic acid, with concomitant quenching of the [Ru(bpy)₂(phen-CD)]²⁺ excited state. This quenching arises from efficient intramolecular electron transfer. The sensitivity of this photoinduced process to the protonation state of the bridge is discussed.     

New amino-functionalized 1,3-alternate calix[4]arene bis- and mono-(benzo-crown-6 ethers) for pH-switched cesium nitrate extraction

Four calix[4]arene benzo-crown-6 ethers functionalized with primary amine groups in various positions have been synthesized. The cesium extraction behavior under alkaline and acidic conditions has been measured for these compounds and compared with that of non-amine containing analogs. Extraction strength when the amine group is neutral is not affected by the amino substituent, but protonation causes a marked decrease in extraction strength, permitting pH-switched back-extraction.     

Dendritic chelating agents. 1. Cu(II) binding to ethylene diamine core poly(amidoamine) dendrimers in aqueous solutions

This paper describes an investigation of the uptake of Cu(II) by poly(amidoamine) (PAMAM) dendrimers with an ethylenediamine (EDA) core in aqueous solutions. We use bench scale measurements of proton and metal ion binding to assess the effects of (i) metal ion-dendrimer loading, (ii) dendrimer generation/terminal group chemistry, and (iii) solution pH on the extent of binding of Cu(II) in aqueous solutions of EDA core PAMAM dendrimers with primary amine, succinamic acid, glycidol, and acetamide terminal groups. We employ extended X-ray absorption fine structure (EXAFS) spectroscopy to probe the structures of Cu(II) complexes with Gx-NH2 EDA core PAMAM dendrimers in aqueous solutions at pH 7.0. The overall results of the proton and metal ion binding measurements suggest that the uptake of Cu(II) by EDA core PAMAM dendrimers involves both the dendrimer tertiary amine and terminal groups. However, the extents of protonation of these groups control the ability of the dendrimers to bind Cu(II). Analysis of the EXAFS spectra suggests that Cu(II) forms octahedral complexes involving the tertiary amine groups of Gx-NH2 EDA core PAMAM dendrimers at pH 7.0. The central Cu(II) metal ion of each of these complexes appears to be coordinated to 2-4 dendrimer tertiary amine groups located in the equatorial plane and 2 axial water molecules. Finally, we combine the results of our experiments with literature data to formulate and evaluate a phenomenological model of Cu(II) uptake by Gx-NH2 PAMAM dendrimers in aqueous solutions. At low metal ion-dendrimer loadings, the model provides a good fit of the measured extent of binding of Cu(II) in aqueous solutions of G4-NH2 and G5-NH2 PAMAM dendrimers at pH 7.0.     

O-Acetyl Protection of 6-Aminoaldopyranosides and 1-Aminoalditols

Abstract

Methyl 6-amino-6-deoxy-α-D-glycopyranosides having the D-gluco, D-manno and D-galacto configurations (1a–3a), 2-aminoethanol (4a), 1-amino-1-deoxy-D-glucitol (5a), and 1-amino-1-deoxy-4-O-β-D-glucopyranosyl-D-glucitol (6a) were transformed into the corresponding per-O-acetyl amine hydrochlorides 1d–6d in excellent yields by using the 2,2-(diethoxycarbonyl)vinyl group for temporary amine protection. Deprotection of the peracetylated enamines 1c–6c was effected with chlorine in chloroform and no O→N acetyl migration occurred when short reaction times were used. Treatment of 1d–6d with thiophosgene resulted in the formation of peracetyl isothiocyanates (1e–6e).     

Encapsulation of halides within the cavity of a pentafluorophenyl-substituted tripodal amine receptor

Pentafluorophenyl-substituted tripodal amine L, tris[[(2,3,4,5,6-pentafluorobenzyl)amino]ethyl]amine, is becoming a potential receptor for encapsulation of Cl- and Br- within the pseudo-C3-symmetric tris(2-aminoethyl)amine (L1) cavity upon protonation of the secondary amines. 1H NMR titration results indicate that [H3L]3+ binds with Cl- and Br- strongly compared to the [H3L2]3+ receptor, where L2 is N,N',N' '-tris[(2-benzylamino)ethyl]amine.     

Enamines I. Vinyl Amine,a Theoretical Study of its Structure,electrostatic potential,and proton affinity

The structure of vinyl amine and its reactivity towards a proton is studied by the PRDDO SCF MO method. The equilibrium structure is found to be non-planar and barriers to inversion- and rotation-dominated processes are calculated. Proton addition to vinyl amine, as a model of enamine protonation, is examined by means of electrostatic molecular potentials and C- versus N-proton affinities.     

Synthesis of polyamino nitriles, en route to acylpolyamine neurotoxins, via the regioselective michael cyanoethylation of unprotected polyamines. Unusual behaviour of 1-(2-aminoethyl)piperazine

The Michael cyanoethylation of 1-(2-aminoethyl)piperazine, 4,4′-methylenebis(cyclohexylamine) and bis(3-aminopropylamine)amine, leading to acrylonitrile free (<100 ppm) polyamino nitriles, as a key step in the synthesis of higher polyamines useful in the synthesis of acylpolyamine neurotoxins, was carried out regioselectively on a multigram scale by careful tuning of reaction conditions, without a necessity to protect nitrogen atoms. The higher reactivity of primary amino groups in aliphatic diamines and triamines [as in bis(3-aminopropylamine)amine] was also observed in the cyclic amine, 4,4′-methylenebis(cyclohexylamine), but reversed in 1-(2-aminoethyl)piperazine. The compounds with a dicyanoethylated nitrogen atom were thermally less stable than the monocyanoethylated ones.     

Synthesis of Substituted 3H-Indole-modified b-Cyclodextrin

The hydrophobic cavities of cyclodextrins and the inclusion with various organic molecules in the aqueous solution make them useful in chemical and biological activities1, one of which is the modified cyclodextrins acting as indicators of molecular recognition. Cyclodextrins, which are spectroscopically inert, can be converted into spectroscopically active compounds by modifing one or two of the hydroxy groups with appropriate chromophores, and used as molecular sensor due to the capability of…     

Spectrophotometric and theoretical studies on complexation of a newly synthesized vic-dioxime derivative with nickel(II) in dimethylformamide

The complexation of a recently synthesized vic-dioxime derivative, 1-({2-[(2-aminoethyl) amino]ethyl}amino)-6-methyl-9H-xanthen-9-one with Ni(II) in N,N-dimethylformamide, was investigated by spectrophotometric and conductometric methods. The possible molecular geometries, binding, and spectroscopic properties for the formed complexes were theoretically studied in detail by the Hyperchem program. The stoichiometry of the complex species was determined from spectrophotometric molar ratio methods at 25°C. The spectral data were further treated by KINFIT to calculate the formation constants of the 1?:?1 and 1?:?2 complexes and their molar absorptivities. Program DATAN was used to calculate the spectral behavior of the complexes in the wavelength range ～380–～550?nm for different mole ratio solutions.     

Reactive interaction of aromatic amines with dialdehyde cellulose gel

A new chromatographic method was developed for separation of amines based on their interaction with aldehyde groups in stationary phase. Expecting specific interaction with aldehyde groups through imine formation (Schiff base), we introduced dialdehyde groups to a commercial cellulose packing by periodate oxidation and examined eluting behavior of various aromatic amines. Primary amines with acid dissociation constants (pKa) greater than 6 showed no delay at pHs of 4.0–5.5, indicating the lack of interaction because of complete protonation. Primary amines with pKa less than 6 showed remarkable delays according to the amount of aldehyde groups on cellulose. The delay was dependent on the pH of eluent. The amines with pKa of 4–5.3 eluted faster at lower pH, apparently because of the change in proportion of free and protonated species. Amines with pKa less than 3.4 also showed delays but they eluted slower at lower pH. The latter behavior can be ascribed to the change in the ratio of free/protonated species of imines formed. Certain degree of steric effect was also noted, that is, compounds with a primary amino group adjacent to bulky substituents (ortho compounds) showed weaker interaction with aldehyde groups than meta- and para-isomers.     

Spin Crossover in a Family of Iron(II) Complexes with Hexadentate ligands: Ligand Strain as a Factor Determining the Transition Temperature

This paper reports the synthesis of a family of mononuclear complexes [Fe(L)]X₂ (X=BF₄, PF₆, ClO₄) with hexadentate ligands L=Hpy-DAPP ({bis[N-(2-pyridylmethyl)-3-aminopropyl](2-pyridylmethyl)amine}), Hpy-EPPA ({[N-(2-pyridylmethyl)-3-aminopropyl][N-(2-pyridylmethyl)-2-aminoethyl](2-pyridylmethyl)amine}) and Hpy-DEPA ({bis[N-(2-pyridylmethyl)-2-aminoethyl](2-pyridylmethyl)amine}). The systematic change of the length of amino-aliphatic chains in these ligands results in chelate rings of different size: two six-membered rings for Hpy-DAPP, one five- and one six-membered rings for Hpy-EPPA, and two five-membered rings for Hpy-DEPA. The X-ray analysis of three low-spin complexes [Fe(L)](BF₄)₂ revealed similarities in their molecular and crystal structures. The magnetic measurements have shown that all synthesized complexes display spin-crossover behavior. The spin-transition temperature increases upon the change from six-membered to five-membered chelate rings, clearly demonstrating the role of the ligand strain. This effect does not depend on the nature of the counter ion. We discuss the structural features accountable for the strain effect on the spin-transition temperature.     

Bioconjugation of Ln3+-doped LaF3 nanoparticles to avidin

The binding of Eu3+-doped LaF3 nanoparticles with biotin moieties at the surface of the stabilizing ligand layer to avidin, immobilized on cross-linked aragose beads, is described. The biotin moieties were attached to the nanoparticles by reaction of an activated ester with the amino groups on the surface of the nanoparticles resulting from the 2-aminoethyl phosphate ligands that were coordinated to the surface through the phosphate end. This strategy of employing the reactions of amines with activated esters provides a general platform to modify the surface of the 2-aminophosphate stabilized Ln3+-doped LaF3 nanoparticles with biologically relevant groups. Significant suppression of nonspecific binding to the avidin modified aragose beads has been realized by the incorporation of poly(ethylene glycol) units via the same reaction of a primary amine with an activated ester. The particle size distribution of the functionalized nanoparticles was within 10-50 nm, with a quantum yield of 19% in H2O for the LaF3 nanoparticles codoped with Ce3+ and Tb3+. A discreet, 4 unit poly(ethylene glycol) spaced heterobifunctional cross-linker, functionalized with biotin and N-hydroxysuccinimide at opposite termini, was covalently linked to the 2-aminoethyl phosphate ligand via the N-hydroxysuccinimide activated ester, making an amide bond, imparting biological activity to the particle. Modification of the remaining unreacted amino groups of the stabilizing ligands was done with Me(OCH2CH2)3CH2CH2(C=O)-NHS (NHS = N-hydroxysuccinimide).     

Synthesis and Structural Characterisation of Two Novel Diastereoisomeric Naproxen Appended β-Cyclodextrin Derivatives

The condensation reaction of 6-deoxy-6-amino(2-aminoethyl)-cyclomaltoheptaose (β-CyDen) and racemic [(R, S)-2-(6-methoxy-2-naphthyl) propanoic acid] (R,S-naproxen) affords two new diastereoisomeric naproxen-appended β-cyclodextrin derivatives. The structural analysis of these two β-CyD derivatives, undertaken by combined use of circular dichroism (CD) and 1D or 2D NMR techniques, shows that the naphthalene ring of the naproxen is included in the CyD cavity in both derivatives. The CD spectra are consistent with an axial complexation model, moreover, the self-inclusion mode is further corroborated by ¹H NMR ROESY spectra which also suggest the orientation of the naphthyl moiety in the cavity of both the diastereoisomers.     

Enantioselective Protonation of Enolates and Enols

Enantioselective protonation, until recently a largely overlooked reaction, has, in the last five years, developed into a field of intense research activity. The progress achieved parallels or complements that obtained in the understanding of enolate structures and reactivities. The conceptual simplicity and attractiveness of enantioselective protonation results from the fact that after reaction, the chiral proton donor is regenerated in its original protonated form by an extractive workup. Enantioselective protonation has been applied to the synthesis of amino acids, antiinflammatory agents (2-arylpropanoic acids), and fragrance compounds such as (S)-α-damascone, for which its industrial feasibility has been demonstrated.