Thermokinetic Study on the Reversible Competitive Inhibition of Bovine Liver Arginase

Introduction Arginase (EC 3.5.3.1) is a widespread and very im-portant enzyme in mammals, which specifically cata-lyzes the hydrolysis of L-arginine to urea and the non-protein amino acid L-ornithine, a key step in the urea cycle.1 Urea is the principal metabolite for disposal of nitrogen as a neutral and nontoxic waste product formed during amino acid metabolism in mammals. L-ornithine serves as a biosynthetic precursor to L-proline and the polyamines such as putrescine, sper-mine (in eucar…     

Total Synthesis of (±)-Butyl Ester of Rosmarinic Acid

Rosmarinic acid, a well-known natural product firstly isolated from rosemary by Scarpati and Oriente in 19581, possesses various kinds of biological activities such as antioxidant2 and antibacterial3. Recently, the synthesis and biological activities of related compounds of rosmarinic acid have received much attention, such as 4, 4?′-O-di-β-D- glucopyranosyl rosmarinic acid4, methyl ester of rosmarinic acid5-6 and rabdosiin7. Butyl ester of rosmarinic acid 1 (Scheme 1) was isolated from Is…     

Microwave-assisted Polycondensation of L-2-Hydroxy-3-phenylpropanoic Acid

The attempts to prepare novel biodegradable polymer carriers for drug controlled release systems have been tried in our group1,2. Poly (L-2-hydroxy-3-phenylpropanoic acid) (PLHPPA) can be considered as derivative of poly (lactic acid) (PLA) which has been applied as biomaterials in drug delivery systems, surgical repair and tissue engineering materials3 for its excellent biodegradability and biocompatibility. PLHPPA contains phenyl groups in its structure. It is designed as a hydrophobic…     

Novel preparation of monolithic imprinted columns for electrochromatographic separation by photopolymerization

A monolithic molecularly imprinted polymer with specific recognition ability for 4-hydroxybenzoic acid (4-HBA) was prepared by in situ photopolymerization, using methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linking agent, toluene and isooctane as porogenic solvents and Irgacure 1800 as an initiator. Baseline separation of isomers of hydroxybenzoic acid was achieved in less than 8 min on this monolithic column using 4-HBA as template, but not on the blank polymer. Furthermore, some neutral compounds could also be baseline-separated on the imprinted polymer column in the mode of pressure-driven capillary electrochromatography.     

Capillary Electrochromatography of Molecularly Imprinted Monolithic Column Using p-Hydroxybenzoic Acid as Templates

Molecularly imprinted polymers using p-hydroxybenzoic acid as templates was synthesized by an in situ polymerization reaction and rendered capillary monolithic column was used in capillary electrochromatographic mode. Good molecular recognition was achieved for phydroxybenzoic acid and good resolution of isomers can be realized.     

Vapor—phase Nitration of Benzene to Nitrobenzene over Supported Sulfuric Acid Catalyst

Nitrobenzene is an important chemical intermediate for producing dyestuffs. It is also used as a solvent. The industrial synthesis of nitrobenzene has been carried out in liquid phase with a mixture of nitric acid and concentrated sulfuric acid. This conventional nitration process still has some unsolved problems such as treatment of waste sulfuric acid and disposal of wastewater. The vapor-phase nitration of benzene to prepare nitrobenzene over the solid acidic catalysts in diluted nitric…     

Synthesis of a Pair of Derivatives of N-Methylpyrrole Polyamide

A pair of derivatives of tetrameric N-methylpyrrole polyamide were synthesized in order to develop a new method for the study of interaction of the polyamide derivatives with DNA. Indole acetic acid and nicotinic acid were introduced to the polyamide in the synthesized compound, which showed an expected red shift in the UV spectrum. These compounds may function as a potential tool in the detection of the polyamide binding to DNA.     

Study on the Synthesis of Phenylacetic Acid by Carbonylation of Benzyl Chloride under Normal Pressure

The influences of some factors on the yield of phenylacetic acid in the carbonylation of benzyl chloride were studied in this paper. These factors included the variety and content of catalyst, and that of solvent, way of material feeding, reaction temperature, sodium hydrate concentration, triphenylphosphine content, presence of surfactant, the ratio of organic phase volume to aqueous phase volume etc. The optimum reaction conditions were found to be: with a one-time pour of 0.15g Pd(PPh3)2Cl2, 0.24g PPh3, 75ml NaOH of 3.5mol/L, 20ml benzyl chloride and 55ml n-butyl alcohol, and the reaction was carried out at 50℃ for about 3 hours. The as-obtained yield of phenylacetic acid was as high as 97.6%. In addition, the influences of the presence of phenylacetic acid and air in the reaction system were also studied. The results showed that the presence of air in the system and the entrainment of phenylacetic acid in the circulating organic phase had great influence on the reaction rate, the stability and performance of catalyst and the yield of phenylacetic acid.     

Improved Performance of W／HZSM-5 Catalysts for Dehydroaromatization of Methane

The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li^ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure.Catalyst activity and stability were found to be influenced by the catalyst acidity related to BrSnsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H^ ions by Li^ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further.The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.     

Fatty Acid Composition of Tobacco Seed Oil and Synthesis of Alkyd Resin

The fatty acid composition of tobacco seed oil revealed that the oil is rich in unsaturated fatty acids, having linoleic acid （71.63%）, oleic acid （13.46%） and palmitic acid （8.72%） as the most abundant unsaturated and saturated fatty acids respectively. So the tobacco oil was characterized as semi-drying type on the basis of fatty acid composition. The synthesis of alkyd resin was carried out by alcoholysis or monoglyceride process using an alkali refined tobacco seed oil, pentaerythritol, cis-1,2,3,6-tetrahydrophthalic anhydride along with lithium hydroxide as catalyst. The alkyd resin so prepared was found to be bright and of low color with high gloss. The drying and hardness properties and adhesion of the tobacco seed oil derived alkyd resin were also found a bit superior to those of other alkyd resins of the same oil length. In addition, the water and acid resistance of the said alkyd was also found comparable to the other alkyds.     

Effect of Concentration of Structurally-Different Carboxylic Acids on Growth and Aggregation of Calcium Oxalate in Gel Systems

The effect of concentration of structurally-different carboxylic acids such as ethylene diamine tetraacetic acid （H4edta）, citric acid （H3cit）, tartaric acid （H2tart）, and acetic acid （HOAc） on growth and aggregation of calcium oxalate （CaOxa） in gel systems was comparatively investigated. H2tart and H3cit could change the morphology of cal- cium oxalate monohydrate （COM） and induce the formation of calcium oxalate dihydrate （COD）. H4edta could induce the formation of COD at a lower concentration of 0.33 mmol/L and have the strongest ability to inhibit aggregation of COM. HOAc inhibited COM aggregation only at a higher concentration than 500 mmol/L. With increasing the number of carboxylic groups in an acid or increasing the concentration of carboxylic acid, the capacity of this acid to induce COD formation and to inhibit growth and aggregation of COM crystals increased. That is, this capacity followed the order： H4edta〉H3cit〉H2tart〉 〉HOAc. The result in this work suggested that the presence of H3cit and H2tart in urine played a role in the natural defense against stone formation.     

Synthesis and biological evaluation of a new series of histone deacetylases inhibitors

Histone deacetylases （HDACs） play an important role in tumorigenesis. Inhibition of HDACs is considered as a potent strategy for cancer therapy. Two lead compounds （ja and jb） were found to have activities against HDACs with IC50 at about 15 μmol/L. Then a new series of hydroximic acid derivatives were designed and synthesized based on them. The HDACs activity assay in vitro found that compounds J04 and ,109 are nearly as potent as the positive control drug Zolinza.     

Effect of Mn（Ⅱ） and Ce（Ⅳ） Ions on the Oxidation of Lactic Acid by Chromic Acid

The kinetics and mechanism of lactic acid oxidation in the presence of Mn（Ⅱ） and Ce（Ⅳ） ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr（Ⅵ） was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn（Ⅱ）.2Cr（Ⅵ）＋2CH3CHOHCOOH→2CH3COCOOH＋Cr（Ⅴ）＋C（Ⅲ） Cr（V）＋CH3CHOHCOOH→Cr（Ⅲ）＋CH3COCOOHThe observed kinetics was explained due to the catalytic and inhibitory effects of Mn（Ⅱ） and Ce（Ⅳ） on the lactic acid oxidation by Cr（Ⅵ）. The reactivity of lactic acid depends upon the experimental conditions. It acts as a two- or three- equivalent reducing agent in the absence or presence of Mn（Ⅱ）. It was examined that Cr（Ⅲ） products resulting from the direct reduction of Cr（Ⅵ） by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters Eo, △H^#, and AS^# were calculated and discussed.     

Synthesis of Asymmetric Propanetriol Analogues

Form natural tartaric acid,(R)-2-benzyloxy-3-(2-tertrahydropyranyloxy) propanol 3 was designed and synthesized, and (R)-2-benzyloxy-3-(4-methoxybenzyloxy)propanol 7 was prepared in a new method. They can be used as chiral synthons of lysophosphatidic acid and other compounds with asymmetric propanetriol backbone.     

Synthesis of protected （2S,4R）-2-amino-4-methyldecanoic acid,a proposed component of culicinins

The protected （2S,4R）-2-amino-4-methyldecanoic acid, a proposed component of culicinins has been synthesized over 10 steps and in total 28% yields using Wittig reaction and Schollkopf amino acid synthesis as key steps.     

A Rapid and Convenient Synthesis of Acylals from Aldehydes and Acetic Anhydrides Catalyzed by SnCl_4/SiO_2

Acylals (1, 1-diacetates) are efficient protecting groups for aldehydes as they are stable in neutral and basic media1. Usually, the acylals are prepared from aldehydes and acetic anhydride in the presence of strong protonic acids such as sulfuric acid2, phosphoric acid2, or methanesulfonic acid2, and Lewis acids such as anhydrous zinc chloride3, phosphorus(III) chloride4, and anhydrous ferric(III) chloride5. Recently the use of montmorillonite clay7, TMCS-NaI8, Sc (OTf)39, Cu (OTf)210 …     

Sensitive analysis of amino acids in injection liquor by reversed-phase HPLC

A convenient derivatization method of amino acids with l-fluoro-2,4-dimtrobenzene as reaction reagent and a separation system were described. The derivative amino acids were separated on a specific chemically bonded phase column with a simple linear gradient elution consisting of aqueous buffer and methanol. The eluate was detected by common ultraviolet absorption detector at 360 nm. The detection limits of amino acids were as low as 10 picomole. This method has been successfully applied to assay amino acid injection liquor used in hospital. It has good repro-ducibility and precision. The procedures avoid the requirements of particular derivative equipment and analyzer employed in conventional amino acid analysis.     

The Condensation of Aromatic Aldehydes with Acidic Methylene Compounds in Water

The condensation of aromatic aldehydes with acidic methylene compounds such as malononitrile, methyl cyanoacetate, cyanoacetamide, 5,5-dimethyl-1,3-cyclohexanedione,bartbituric acid and 2-thiobarbituric acid proceeded very efficiently in water in the presence of triethylbenzylammonium chloride (TEBA) and the products were isolated simply by filtration.     

Selective Oxidation of Propane by Lattice Oxygen of Vanadium-Phosphorous Oxide in a Pulse Reactor

Selective oxidation of propane by lattice oxygen of vanadium-phosphorus oxide (VPO) catalysts was investigated with a pulse reactor in which the oxidation of propane and the re-oxidation of catalyst were implemented alternately in the presence of water vapor. The principal products are acrylic acid (AA),acetic acid (HAc), and carbon oxides. In addition, small amounts of C1 and C2 hydrocarbons were also found, molar ratio of AA to HAc is 1.4-2.2. The active oxygen species are those adsorbed on catalyst surface firmly and/or bound to catalyst lattice, i.e. lattice oxygen; the selective oxidation of propane on VPO catalysts can be carried out in a circulating fluidized bed (CFB) riser reactor. For propane oxidation over VPO catalysts, the effects of reaction temperature in a pulse reactor were found almost the same as in a steady-state flow reactor. That is, as the reaction temperature increases, propane conversion and the amount of C1 C2 hydrocarbons in the product increase steadily, while selectivity to acrylic acid and to acetic acid increase prior to 350℃ then begin to drop at temperatures higher than 350℃, and yields of acrylic acid and of acetic acid attained maximum at about 400℃. The maximum yields of acrylic acid and of acetic acid for a single-pass are 7.50% and 4.59% respectively, with 38.2% propane conversion. When theamount of propane pulsed decreases or the amount of catalyst loaded increases, the conversion increases but the selectivity decreases. Increasing the flow rate of carrier gases causes the conversion pass through a minimum but selectivity and yields pass through a maximum. In a fixed bed reactor, it is hard to obtainhigh selectivity at a high reaction conversion due to the further degradation of acrylic acid and acetic acid even though propane was oxidized by the lattice oxygen. The catalytic performance can be improved inthe presence of excess propane. Propylene can be oxidized by lattice oxygen of VPO catalyst at 250℃, nevertheless, selectivity to AA and to HAc are even lower, much more acetic acid was produced (molar ratio of AA to HAc is 0.19:1-0.83:1) though the oxidation products are the same as from propane.     

Soluble Polymer-Supported Synthesis of α-Amino Acid Derivatives

Due to the central role played by α-amino acid in chemistry and biology, the development of versatile and new methodology for the synthesis of natural and unnatural α-amino acid has emerged as an important and challenging synthetic endeavour for organic chemists.[1] Among the various methodologies reported for α-amino acid synthesis, [2,3] the solid-phase organic synthesis (SPOS) has served as an important approach. [4] However, inherent prob lems on solid supports are reactive site accessibility, site-site interaction and monitoring of the reaction.