Thiocarbonyl compounds from β-substituted vinylald- and -ketimmonium derivatives

Results on the synthesis of thiocarbonyl compounds based on the reactions of conjugated unsaturated immonium salts with S-nucleophiles are summarized, and the physical and chemical properties as well as the synthetic potential of forming α, β-unsaturated thioaldehydes and thioketones are considered.     

Organocatalytic synthesis of optically active aryllactic acid derivatives from β-ketosulfoxides

The organocatalytic synthesis of new α-acyloxy-3-arylpropionic thioesters has been accomplished providing some enantioenriched important aryllactic acid derivatives in good yield and enantioselectivities.     

Novel porous organosilica containing amino and β-cyclodextrin groups

The elaboration of new hybrid mesoporous silica materials containing β-cyclodextrin groups and amine functions is reported. The synthesis is based on a direct co-condensation between β-CDAPS, a hybrid precursor obtained by reaction between tosyl-β-cyclodextrin and aminopropyltrimethoxysilane previously described, and tetraethyl orthosilicate via a sol–gel pathway templated by three different surfactants: anionic (sodium dodecylsulfate), cationic (cetyltrimethylammonium bromide) or neutral (Triton X-45) ones. The chemical structure and morphology are characterized and analyzed for all the series. Finally, the templating based mechanisms are investigated by comparing these samples with series prepared without template or without cyclodextrin.     

Novel indanone derivatives as potential imaging probes for β-amyloid plaques in the brain

Molecular imaging probes to detect senile plaques (SPs) might help the early diagnosis of Alzheimer's disease (AD). In this study, a novel series of indanone derivatives were synthesized and characterized. In in vitro binding studies, compound 2e exhibited a K(i) value of 16 nM with a human AD brain homogenate. Although they displayed relatively low affinities for 2i and 2j--with K(i) values of 99 and 237 nM, respectively--the SPs in AD brain sections were positively stained by 2j. A method for in situ micro-autoradiography of AD brain was developed in this study and showed clear labeling of SPs by [(125)I]2i and [(125)I]2j. Both [(125)I]2i and [(125)I]2j had suitable lipophilicities and displayed high initial uptake and rapid clearance from the mouse brains. Furthermore, [(125)I]2i and [(125)I]2j were more stable in human brain homogenates than in mouse brain homogenates. These data suggest that such indanone derivatives might represent potential amyloid imaging agents for the detection of SPs in AD.     

Novel α-ketoesters from β-diketones via a vanadium-mediated tandem transformation under an oxygen atmosphere

Novel α-ketoesters were conveniently synthesized from acetylacetone and analogs via a vanadium-mediated one-pot tandem process. These advanced α-ketoesters could be selectively prepared under additive-free, mild conditions, viz., 1 atm O₂ pressure and 50–80 °C. DFT calculations were performed to provide insights into the detailed mechanism of the tandem transformation.     

Preparation of long-chain β-enaminones and β-diketones from long-chain 3,5-disubstituted isoxazole compounds

A series of long-chain compounds containing the β-enaminone functionality were prepared in yields ranging from 71 to 88% from their corresponding long-chain 3,5-disubstituted isoxazole precursors utilizing a Raney nickel-catalyzed reductive ring-opening procedure. These newly prepared multifunctional compounds were subsequently hydrolyzed under mild acidic conditions (pH 4–5) to give their corresponding long-chain β-diketones in yields ranging from 79 to 98%. Both the β-enaminone and β-diketone functionalized compounds were characterized by NMR, IR spectroscopy, GC-MS, and m.p. The mass spectra for these two classes of compounds, derived by utilizing electron impact ionization, gave distinctive McLafferty rearrangement fragmentation ions that clearly established the newly introduced functionality to reside at the C-2 and C-4 positions of the lipid’s alkyl chain. ¹H NMR spectra of the pure β-diketone compounds were complex owing to the keto enol tautomerism displayed by the β-diketone moiety. In solution the β-diketone compounds were shown to exist mainly in the enolic tautomeric form. Long-chain β-diketone compounds are known to be relatively common constituents of some plant waxes, and the overall procedure starting from soybean methyl esters provides a complementary approach to prepare these types of compounds.     

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.     

Synthesis of β-SiC powder from organic precursor and its sinterability

β-SiC powders were synthesized by the carbothermic reduction of SiC precursors which were derived from liquid silica and carbon sources. From the precursor materials in which the mixing condition of silica and carbon was improved, pure SiC powders were produced. The powders could be sintered by additions of carbon and small amounts of boron. No decarburization and no acid purification processes were required before sintering.     

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.     

Synthesis and characterization of aromatic polyamides derived from various derivatives of 4,4’-oxydianiline

Three aromatic diamines, 2,2′-diiodo-4,4′-oxydianiline (DI-ODA 2), 2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′-oxydianiline (BTFP-ODA 3) and 2,8-diaminodibenzofuran (DADBF 5) were synthesized by using 4,4-oxydianiline (4,4′-ODA) as the starting material. New aromatic polyamides 6, 7 and 8 were prepared from these three diamines and six commercially available aromatic diacids by direct polycondensation, respectively. Polyamides 6 and 7 contained bulky iodide and p-trifluoromethylphenyl substitutents that would hinder the chain packing and increase the free volume. They exhibited good optical transparency in visible light region and showed excellent solubility in organic solvents such as DMSO, DMAc, DMF and NMP. Polyamides 8 containing planar dibenzofuran moieties had the highest glass transition temperatures and decomposition temperatures among these polyamides. Polyamides 6 had the lowest decomposition temperatures due to the presence of weak carbon–iodine bond. All of these polyamides showed amorphous nature evidenced by wide angle X-ray diffraction. No endothermic peaks were observed from DSC thermograms up to their decomposition temperatures. High optical transparency and excellent solubility combined with good thermal stability make these polyamides attractive for potential soft electronics applications.     

Friction and wear characteristics of β-Sialon prepared from secondary aluminum dross

This study investigates the properties of β-Sialon synthesized from secondary aluminum dross. High-purity β-Sialon powders were synthesized through nitriding reduction, followed by spark plasma sintering to obtain dense sintered bodies. The phase composition, microstructure, microhardness, and friction and wear characteristics of the sintered bodies were analyzed using X-ray diffractometry, scanning electron microscopy, a microhardness tester, and a friction and wear tester, respectively. Fracture analysis revealed a combination of through-crystal and along-crystal fractures, with fracture occurrence correlated to crack expansion. The crystalline fractures exhibited a toughening effect. The friction and wear test of the sintered bodies demonstrated a decrease in the friction coefficient with increasing load and speed. The wear behavior of the sintered bodies encompassed abrasive wear, adhesive wear, and fatigue wear. Abrasive wear dominated at low speed and low load, while adhesive wear was prominent at high speed and high load. Increasing speed accentuated adhesive wear characteristics, while increasing load led to the formation of a material layer on the friction ball surface, delaying wear initiation.     

Purification and isolation of β-glucans from barley: Downstream process intensification

The purpose of this work was to study the purification and isolation (downstream process) of the β-glucan extracted from barley in an ultrasound assisted extraction (UAE) process. The co-extracted starch (average concentration 5.2 ± 0.1 g/L) was hydrolyzed by means of α-amylase. The optimization of the hydrolysis length, temperature and enzyme dose led to removal efficiencies higher than 90% (9 min hydrolysis length and enzyme doses of 100 μL/g at 55 °C), compared to the traditional hydrolysis processes (1 h at 95 °C). In a second step, a significant intensification of the process has been achieved by dosing the enzyme during the UAE step (7 min at 55 °C), resulting in a starch removal of 90%.Dextrins and other oligosaccharides were formed as a consequence of the enzymatic hydrolysis. In order to separate these low molecular weight molecules from the β-glucan (239 kDa), an ultrafiltration process (polysulfone membrane, nominal MWCO 100 kDa) was tried in a tangential flow cell: diafiltration successfully eliminated more than 45% of the oligosaccharides present in the liquid, providing a significant increase in the concentration of β-glucan and with the possibility of improving the percentage of elimination.The combination of these three technologies (UAE, enzymatic hydrolysis and diafiltration) allows getting high purity β-glucan concentrates (greater than 70%).     

Preparation of Sesaminol from Sesaminol Triglucoside by β-Glucosidase and Cellulase Hydrolysis

Sesaminol triglucoside (i.e., 2,6‐O‐di(β‐d ‐glucopyranosyl)‐β‐d ‐glucopyranosyl sesaminol, STG) is a physiologically active substance obtained abundantly from defatted sesame cake. Since, the industrial preparation of sesaminol from STG has not been reported previously, the aim of this research was to prepare sesaminol by hydrolysis of STG using β‐glucosidase and cellulase. Under the optimal conditions of total enzyme dosage 100 μL (8,000.72 U), the ratio of β‐glucosidase and cellulase 20:80 (v/v) (0.72:8,000, U/U), reaction time 24 h, substrate concentration 6 mg/mL, reaction temperature 50 °C, and reaction system pH 4.8, the yield of sesaminol was 48.9 %. Further, sesaminol and other hydrolysis products (sesaminol diglucoside and sesaminol monoglucoside) were successfully determined by high performance liquid chromatography and electrospray ionization/mass spectrometry.     

Synthesis and characterization of polymers from β-propiolactone and poly(ethylene glycol)s

Uncatalysed polymerizations of β-propiolactone with low-molecular-weight poly(ethylene glycol)s were carried out in bulk, at temperatures in the range of 70 to 120°C. ¹H nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) measurements on the resulting products indicated a block copolymer structure. Gel permeation chromatography (g.p.c.) and d.s.c. analyses showed that in some cases the copolymerization is accompanied by homopolymerization of β-propiolactone, probably due to the presence of residual water in the poly(ethylene glycol). N.m.r. and infra-red (i.r.) spectra of copolymers revealed the presence of hydroxyl and carboxyl end groups. The copolymerization reaction may be visualized as a two-step process, in which the ring opening of β-propiolactone takes place on both the hydroxyl groups of poly(ethylene glycol), followed by repetitive monomer addition forming an ester-ether-ester triblock copolymer.     

Distribution and Molecular Characterization of β-Glucans from Hull-Less Barley Bran, Shorts and Flour

Six hull-less barley cultivars widely grown in China were roller-milled to produce bran, shorts and flour fractions. The distribution and molecular characteristics of β-glucans from the three roller-milled fractions were investigated. The β-glucan contents in the six hull-less barley cultivars varied from 4.96% to 7.62%. For all the six cultivars, the shorts fraction contained the highest concentration of β-glucan (8.12-13.01%), followed by bran (6.15-7.58%) and flour (2.48-2.95%). Crude β-glucans were prepared from the three roller-milled fractions using aqueous sodium carbonate (pH 10). These preparations contained 45.38-71.41% β-glucan, 10.81-17.26% arabinoxylan, 2.6-9.6% protein, 2.7-9.0% starch, and 5.23-9.68% ash. Purification using α-amylase and β-xylanase in combination with pH adjustment and dialysis produced high purity β-glucan preparations (91-95%). The molecular weight (Mw) of β-glucan preparations from roller-milled fractions ranged from 117,600 to 852,400 g/mol. β-Glucan from flour had higher Mw than those from shorts and bran within the same cultivar, and β-glucan preparations from bran had the lowest Mw.     

Ionic liquid crystals from β-diketonyl containing pyridinium cations and tetrachlorozincate anions

In this work, an approach towards ionic liquid crystals is strategically designed. A pyridine group has been attached to an 1,3-diketone containing an alkyloxyphenyl R substituent (R = C₆H₄OC_nH_2n+1; n = 10–18) and protonated with hydrochloric acid towards the formation of the chloride salts of 2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium cations [OO^R(n)py]Cl (I), which have been proved to be non-mesomorphic. Reaction of these organic–inorganic compounds (I) with ZnCl₂ yields to the ionic liquid crystals of the type bis{2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium}tetrachlorozincate [OO^R(n)py]₂[ZnCl₄] (II).The crystalline structure of compounds [OO^R(12)py]Cl and [OO^R(10)py]₂[ZnCl₄] as representative examples of both kinds of salts have been solved and discussed. Both compounds exhibit layered structures containing cationic and anionic sublayers. In addition for the tetrachlorozincate salt [OO^R(16)py]₂[ZnCl₄] structural relationships between the mesophases and the crystalline phase are proposed on the basis of the variable-temperature small-angle X-ray diffraction studies.     

Inhibition of β-Glucosidase and Esterase by Tannins from Betula, Salix, and Pinus Species

The reaction of tannin fractions isolated from the bark of Betula, Salix, and Pinus species with two enzymes, -glucosidase and esterase, was investigated. The influence of precipitation to the hydrolytic capacity of -glucosidase also was studied. All tannins studied precipitated -glucosidase and esterase, and moderate differences in the precipitating capacities of the tannins were observed. Interestingly, complex formation between -glucosidase and tannin did not markedly affect the activity of the enzyme. Therefore, complex formation during the insect/herbivore feeding does not necessarily change the defense activity of phenolic glycosides or decrease activity of digestive enzymes.     

Nifedipine Protects INS-1 β-Cell from High Glucose-Induced ER Stress and Apoptosis

Sustained high concentration of glucose has been verified toxic to β-cells. Glucose augments Ca(2+)-stimulated insulin release in pancreatic β-cells, but chronic high concentration of glucose could induce a sustained level of Ca(2+) in β-cells, which leads to cell apoptosis. However, the mechanism of high glucose-induced β-cell apoptosis remains unclear. In this study, we use a calcium channel blocker, nifedipine, to investigate whether the inhibition of intracellular Ca(2+) concentration could protect β-cells from chronic high glucose-induced apoptosis. It was found that in a concentration of 33.3 mM, chronic stimulation of glucose could induce INS-1 β-cells apoptosis at least through the endoplasmic reticulum stress pathway and 10 μM nifedipine inhibited Ca(2+) release to protect β-cells from high glucose-induced endoplasmic reticulum stress and apoptosis. These results indicated that inhibition of Ca(2+) over-accumulation might provide benefit to attenuate islet β-cell decompensation in a high glucose environment.     

High Regio- and Stereoselective Multi-enzymatic Synthesis of All Phenylpropanolamine Stereoisomers from β-Methylstyrene

We present a one-pot cascade for the synthesis of phenylpropanolamines (PPAs) in high optical purities (er and dr up to >99.5 %) and analytical yields (up to 95 %) by using 1-phenylpropane-1,2-diols as key intermediates. This bioamination entails the combination of an alcohol dehydrogenase (ADH), an ω-transaminase (ωTA) and an alanine dehydrogenase to create a redox-neutral network, which harnesses the exquisite and complementary regio- and stereo-selectivities of the selected ADHs and ωTAs. The requisite 1-phenylpropane-1,2-diol intermediates were obtained from trans- or cis-β-methylstyrene by combining a styrene monooxygenase with epoxide hydrolases. Furthermore, in selected cases, the envisioned cascade enabled to obtain the structural isomer (1S,2R)-1-amino-1-phenylpropan-2-ol in high optical purity (er and dr >99.5 %). This is the first report on an enzymatic method that enables to obtain all of the four possible PPA stereoisomers in great enantio- and diastereo-selectivity.