Application of nickel(II) complexes to the efficient synthesis of α- or β-amino acids

Nonproteinogenic α- or β-amino acids have attracted tremendous attention, as they are widely utilized for biological, biochemical, pharmaceutical, and asymmetric chemical investigations. Recently, we developed a series of new strategies for preparing achiral and chiral nickel(ii) complexes for the synthesis of amino acids. We applied these new methods utilizing chiral nickel(ii) complexes for the asymmetric Mannich reaction to synthesize enantiopure α,β-diamino acids, the enantioselective tandem conjugate addition-elimination reaction to prepare glutamic acid derivatives, the Suzuki coupling reaction to yield β(2)-amino acid derivatives, the asymmetric Mannich reaction to synthesize 3-aminoaspartate, the asymmetric Michael addition reaction to give β-substituted-α,γ-diaminobutyric acid derivatives, the asymmetric alkylation reaction to prepare linear ω-trifluoromethyl containing amino acids, and the asymmetric Michael addition reaction to synthesize syn-β-substituted tryptophans.     

Continuous production of structured lipid containing γ-linolenic and caprylic acids by immobilized Rhizopus delemar lipase

Production of a structured lipid containing γ-linolenic acid (GLA) achieved by the continuous acidolysis of borage oil with caprylic acid (CA) using 1,3-specific Rhizopus delemar lipase as a catalyst. The lipase immobilized on a ceramic carrier was activated by feeding the borage oil/CA (1:2, w/w) mixture saturated with water into a column packed with the enzyme. However, the generation of partial glycerides (20%) in the reaction mixture showed that hydrolysis occurred concomitantly with acidolysis. The concomitant hydrolysis was completely repressed by feeding the oil/CA substrate mixture without adding additional water. When the substrate mixture was fed at 30°C and a flow rate of 4.5 mL/h into a column packed with 8 g of the carrier with immobilized lipase, the content of CA incorporated in glycerides was 50 to 55 mol%. The acidolysis activity scarcely changed even though the substrate mixture was continuously fed for 60 d; then it gradually decreased. The CA content in glycerides was decreased to 73% of the initial value after 100 d, but returned to the initial level when the flow rate was reduced to 3.1 mL/h. Molecular distillation was employed to separate the transesterified oil from the reaction mixture. No glycerides were detected in the distillate, and the transesterified oil was recovered as the residue (acid value, 2.6). Regiospecific analysis of the transesterified oil showed that only fatty acids at the 1- and 3-positions of borage oil were exchanged for CA. It was additionally found by high-performance liquid chromatography analysis that all the triglycerides contained one or two CA, and that the triglyceride with two GLA and one CA was also present, because the lipase acted on GLA very weakly.     

Determination of dissociation constants of α-amino acids by ionophoretic technique

A new method involving the use of ionophoretic technique is described for the assessment of dissociation constants of some α-amino acids, viz. glycine, alanine phenylalanine, valine and leucine. The method is based on migration of a spot of the acids with variation of pH of background electrolyte containing 0.1 M perchloric acid. A graph of pH against mobility gives information about nature of dissociation and helps in calculating them. The calculated values are in fairly good agreement with literature values determined by other techniques.     

Seed oil fatty acids of loasaceae—A new source of γ-linolenic and stearidonic acids

The pharmaceutically interesting Δ6-FA 18∶3Δ6c, 9c, 12c (γ-linolenic acid) and 18∶4Δ6c,9c,12c,15c (stearidonic acid) appear to have evolved independently several times during plant phylogenetic evolution. They typically occur in “clusters” of a few closely related species or genera in about a dozen different plant families throughout the plant kingdom. A hither-unknown “cluster of occurrence” has now been discovered in the New World plant family Loasaceae. γ-Linolenic and stearidonic acids occur exclusively in representatives of the newly described genus Nasa at significance levels of between 3 and 10% each. Nasa had recently been separated from the older, more broadly circumscribed genus Loasa. The two Δ6-FA were not found in the closely related genus Loasa sensu stricto, nor in a number of other representatives of Loasaceae.     

Novel cell-penetrating peptides based on α-aminoxy acids

The remarkable ability of cell-penetrating peptides (CPPs) to deliver cell-impermeable compounds into living cells makes them attractive transporters for use in biology and medicine. Despite their highly efficient cellular uptake, CPPs consisting of natural amino acids always suffer from degradation and endosomal entrapment, thereby greatly limiting their application in vivo. Here, we describe the preparation of novel CPPs incorporating α-aminoxy acid residues and their cellular uptake behavior. We demonstrate that introducing α-aminoxy acids into the backbones of CPPs enhances their diffuse cytosolic distribution after direct membrane translocation. We also reveal a hybrid peptide, consisting of D-α-aminoxy acids and L-α-amino acids, that achieves efficient diffuse distribution in the cytosol, is stable toward serum, and possesses low cytotoxicity, thus making it a possible vector candidate for in vivo applications. Our results confirm that α-aminoxy acids are useful building blocks when designing novel CPPs possessing favorable properties.     

One-step aromatic acids assisted synthesis of γ-Fe2O3 nanoparticles with large surface area by thermal decomposition of ferric nitrate

Maghemite (γ-Fe₂O₃) has attracted much attention due to its variety of applications in many areas. However, the current preparation methods of γ-Fe₂O₃ still involve complicated processes and a high cost, thereby needing improvement. In this study, a novel and facile one-step solid-state method for the preparation of γ-Fe₂O₃ nanoparticles (NPs) is performed through the thermal decomposition of ferric nitrate (Fe(NO₃)₃?9H₂O) and the addition of aromatic acids. Three aromatic acids that have different numbers of carboxyl groups (i.e., benzoic acid, phthalic acid, and trimesic acid) are used as additives and their effects on the formation of γ-Fe₂O₃ NPs are investigated. Furthermore, the influence of the aromatic acid/Fe(NO₃)₃?9H₂O mass ratio and calcination temperature on the structural properties of the products are investigated. The structural properties, morphology, and magnetic properties of the products are analyzed through X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption/desorption measurements, and magnetic measurements. The results show that the addition of aromatic acids to Fe(NO₃)₃?9H₂O leads to the formation of γ-Fe₂O₃ NPs, and has a significant influence on the morphology of γ-Fe₂O₃ NPs. When the aromatic acid/Fe(NO₃)₃?9H₂O mass ratio is greater than 0.5, the addition of the three aromatic acids leads to the formation of pure γ-Fe₂O₃. The γ-Fe₂O₃ NPs obtained from benzoic acid/Fe(NO₃)₃?9H₂O and phthalic acid/Fe(NO₃)₃?9H₂O systems do not show a well-defined morphology. In contrast, the γ-Fe₂O₃ NPs obtained from the trimesic acid/Fe(NO₃)₃?9H₂O system are composed of a porous three-dimensional hierarchical structure and have the largest Brunauer?Emmett?Teller surface area (100.0 m² g^?1).     

Template-free synthesis of mesoporous γ-alumina with tunable structural properties

Mesoporous γ-Al₂O₃ (MA) with agglomerated nanoparticles was successfully synthesized by using aluminum sulfate as inorganic Al resource, and hexamethylene tetramine (HMTA) as precipitant without using any surfactants, via a hydrothermal method. All the experimental processes experienced the hydrolysis, precipitation and calcination steps. The structural and morphological properties of uncalcined and calcined samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry differential thermal gravity (TG-DTG) and N₂ adsorption–desorption. The bulk density of the sample is 0.682 cm³  g⁻¹, and the specific surface area is 273.302 m² g⁻¹. The pore diameters (7.1 nm and 9.7 nm) indicate that a typical bimodal mesoporous structure was formed within MA. In order to tune the structural properties of MA, various kinds of inorganic aluminum sources and precipitating agents were employed to carry out contrast experiments, which leaded to regular variations in the specific surface area (200.898–273.302 m² g⁻¹), pore volume (0.121–1.327 cm³ g⁻¹) and pore size (3.7–35.9 nm). At the same time, the experimental results also demonstrated that the various kinds of Al resources and precipitants had no effects on the crystal structure of MA. However, the morphologies of samples, such as nanoparticles, short fibers, flower-like and block-shaped, can be controlled effectively. The present study provides a simple and effective approach for preparing MA, and the structural properties of MA can be controlled precisely by carefully choosing aluminum sources and precipitants. The approach of this work not only allows us to investigate the growth mechanism of the final product, but also reduces cost and the environmental pollution effectively than other template methods.     

The catalysis of the Ruff oxidative degradation of aldonic acids by titanium‐containing zeolites

Ti‐BEA and Ti‐FAU, obtained by post‐synthesis treatment, and TS‐1, obtained by direct hydrothermal synthesis, have been tested as catalysts for the Ruff oxidative degradation of calcium d‐gluconate to d‐arabinose using diluted hydrogen peroxide as oxidant. Only large‐pore zeolites Ti‐BEA and Ti‐FAU were found to be active. It was shown, in particular, that a very rapid leaching of titanium occurred and that the titanium species present in the solution were responsible for the catalytic activity observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

CAN catalyzed synthesis of β-amino carbonyl compounds via Mannich reaction in PEG

Ceric ammonium nitrate (CAN) in PEG was used as an efficient and recyclable solvent system for one pot, three component Mannich reaction of acetophenone with aromatic aldehydes and aromatic amines. This protocol has advantages of high yield, mild reaction conditions, no environmental pollution and simple work up procedure.     

New polyacetylene-based chemosensory materials for the “turn-on” sensing of α-amino acids

For the first time, a new disubstituted polyacetylene (P1) was utilized to sense α-amino acids based on a “turn-on” model, through an indirect approach. Thus, first, the strong blue fluorescence of P1 was quenched by trace copper ions efficiently, then the addition of α-amino acids to the P1/Cu²⁺ complex could recover the strong fluorescence of P1 to report the presence of α-amino acids. Interestingly, the P1/Cu²⁺ complex demonstrated much higher sensitivity towards histidine, with the detection limit of ∼2 ppm (∼1.3 × 10⁻⁵ mol/L). With the aid of a normal UV lamp, histidine could be differed from other α-amino acids visually by the observation of its strong blue fluorescence, at the concentration as low as 4.0 × 10⁻⁵ mol/L. Due to the convenient synthesis of P1, and the so far reported many other conjugated fluorescent polymers, the work reported here might open up a new avenue to develop new biosensors.     

The rate of ring opening of γ-and δ-lactones derived from meadowfoam fatty acids

δ-Lactones derived from meadowfoam (Limnanthes) fatty acids were reacted with amine and alcohol nucleophiles in a second-order reaction to provide the acyclic 5-hydroxy eicosanoic acid esters and amides. The rate of reaction for the ring opening of δ-lactones was compared to the rate of ring opening of γ-lactones and the rate of derivatization of meadowfoam fatty acids. δ-Lactones showed a much larger rate for the formation of derivatives than the corresponding γ-lactones or fatty acids. γ-Lactone had a rate constant >7700 times larger for the formation of butyl ester than meadowfoam fatty acids. The formation of amides from δ-lactones is even faster than the esterification reaction and requires no catalyst or solvent when conducted at the melting point of the lactone.     

Catanionic-surfactant templated synthesis of organized mesoporous γ-alumina by double hydrolysis method

Organized mesoporous γ-alumina samples were prepared by cationic-anionic double hydrolysis (CADH) method using the mixture of cationic and anionic surfactants as template. The intermediate aluminum oxyhydroxides were characterized by XRD, SEM, TEM, FT-IR and TG. Boehmite could easily form under the given synthetic conditions, where an increase in the crystallization temperature favored the formation of well-crystallized boehmite. After the calcination, organized mesoporous γ-Al₂O₃ was obtained by dehydroxylation between AlOOH octahedron structures. After being characterized by N₂ adsorption–desorption, the obtained γ-Al₂O₃ was of excellent textural properties, i.e., large pore volume (0.79 cm³ g⁻¹), and large pore size (12.1 nm) with narrow pore size distribution which can be used as good candidates for catalyst support in the processing of heavy petroleum. In this modified CADH method, the mixture of cationic and anionic surfactants plays a key role in the formation of relatively large mesopore.     

The synthesis and photophysical properties of novel triphenylamine derivatives containing α, β-diarylacrylonitrile

α, β-Diarylacrylonitrile halides were prepared by condensation of appropriate arylaldehydes and arylacetonitrile halides using a catalytic amount of NaOCH₃ at room temperature. The diarylamines were reacted with various α, β-diarylacrylonitrile halides to afford several triphenylamine compounds, which displayed efficient hole transportation in the presence of Pd(OAc)₂/P(o-tolyl)₃ catalyst, thereby constituting organic light emitting device materials. The novel triphenylamine derivatives were characterized using FTIR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The UV–vis absorption and photoluminescence spectra of the compounds were investigated. The lowest absorption band of α, β-diarylacrylonitrile-containing, triphenylamine derivatives, which occurred at ～400 nm, was assigned to charge-transfer transitions with an emission at 500–574 nm in different solutions and in the solid state.     

High-purity γ-linolenic acid from borage oil fatty acids

High-purity γ-linolenic acid (GLA) was obtained by employing a modified low-temperature solvent crystallization process, followed by a lipase-catalyzed esterification, to borage oil fatty acid. By applying a two-stage solvent crystallization process to the borage oil fatty acid, GLA content was increased from 23.4 to 92.1% with a yield of 89.3%. After the esterification of GLA-rich fatty acid with butanol catalyzed by Lipozyme IM-60, GLA content in the fatty acid was further raised from 92.1 to 99.1%. The overall yield of the combined process was 72.8%. The effects of operation parameters on the Lipozyme IM-60 catalyzed esterification between fatty acid and alcohol were systematically investigated.     

Highly efficient catalyst system for the synthesis of 2‐arylpropionic acids by carbonylation

Carbonylation of 1‐(4‐isobutylphenyl)ethanol has been studied using a homogeneous catalyst system consisting of PdCl₂(PPh₃)₂/ TsOH/ LiCl. Higher reaction rates with TOF up to 1200 h⁻¹ and ibuprofen selectivity >95% have been achieved at 388 K under a CO partial pressure of 5.4 MPa. The reaction proceeds through the formation of 4‐isobutylstyrene and 1‐(4‐isobutylphenyl)ethyl chloride as intermediates. The same catalyst system is shown to be effective for carbonylation of various α-arylethanols, vinyl aromatics and corresponding chloro derivatives. This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel synthesis and characterization of nanosized γ-Al2O3 from kaolin

This paper reports the synthesis of nanosized γ-Al₂O₃ from acid-leachates of calcined kaolin. Al (hydr)oxide was precipitated with ammonia from the leachate in the presence of polyethylene glycol. A white powder of nanosized γ-Al₂O₃ particles was obtained after calcination. X-ray diffraction (XRD), different scanning calorimetries and thermogravimetry (DSC-TG), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and magic angle spinning nuclear magnetic resonance (MAS NMR) were used to characterize the samples. Typical nanosized γ-Al₂O₃ particles showed rod-like morphology with width of about 7 nm and length of approximately 20 nm. A possible mechanism from kaolin to nanosized γ-Al₂O₃ is proposed.     

Sonochemical intercalation synthesis of nano γ-nickel oxyhydroxide: Structure and electrochemical properties

Nano γ-nickel oxyhydroxide (nano γ-NiOOH), intended as a new positive electrode material for alkaline Zn/Ni batteries, was synthesized by a sonochemical intercalation method. Using NaClO as oxidant, 5 M NiCl₂ solution was added dropwise to a concentrated alkaline solution of NaClO + NaOH, which allows all four elementary reactions (precipitation, oxidation, cation exchange, and water molecule intercalation) to proceed simultaneously under low-frequency ultrasonic irradiation. XRD, SAXS, TEM, SEM, AAS, IR, TG, CT (complexometric titration), cyclic voltammetry (CV), and a charge-discharge test of imitative cell have been used to characterize the microstructural characteristics, composition and electrochemical properties of the synthesized material. The results showed that the lattice parameters of nano γ-NiOOH are a = 2.8256 Å and c = 20.7938 Å. The average oxidation state of Ni in the sample is 3.65 as measured by an indirect iodine method. The alkali metallic Na⁺ ions and water molecules have been inserted into sites between NiO₂ layers. The cyclic voltammogram of nano γ-NiOOH exhibited two cathodic peaks and two anodic peaks, which is in accord with the redox reaction between the various phases of Ni(OH)₂ and NiOOH. The charge-discharge test of imitative cells revealed that nano γ-NiOOH exhibited a higher discharge capacity than spherical β-NiOOH.     

The reactivity of titanium–vanadium containing groups in the synthesis of two-component monolayers on silica surfaces

The coating of silica surfaces with two-component VOCl₃ and TiCl₄ monolayers was studied with respect to the composition of the products and the kinetics of interaction. The titanium and vanadium-containing groups were found to be able to replace each other equivalently. Surface sites were found to determine reactivity, as were lateral interactions in the monolayer. The results found the presence of two kinds of active center; with the estimated ratio of such groups correlating with data from chemical analyses of the concentrations of groups covalently linked to the surface by different numbers of bonds.     

In vitro degradation assessment of optically active poly(urethane-imide)s based on α-amino acids

The aim of this work is to obtain optically and biologically active poly(urethane-imide)s (PUIs) using N,N’-(pyromellitoyl)-bis-l-tyrosine dimethyl ester (5) as a chiral and biologically active diphenolic monomer. Step-growth polymerization of diol 5 with various aliphatic and aromatic diisocyanates was carried out by gradual heating technique. The resulting PUIs were characterized with FT-IR, and two of them by ¹H-NMR spectroscopy and elemental analysis. Thermogravimetric analysis and differential scanning calorimetry were used to determine the thermal properties of the two representative PUIs. The morphology of polymer was studied by X-ray diffraction analysis. Furthermore, in vitro toxicity and biodegradability behaviors of the obtained PUIs were studied in culture media and soil burial degradation which reveals that the synthesized polymers are biologically active and biodegradable in natural environment.