Obtaining high stereoselectivity in glycosylation reactions is often challenging in the absence of neighboring group participation. In this study, we demonstrate that activation of glycosyl trichloroacetimidate donors with immobilized perchloric acid on silica (HClO(4)-SiO(2)) provides higher alpha-selectivity than trimethylsilyl triflate (TMSOTf) for reactions that do not involve neighboring group participation.

The GH3 family of acyl-acid-amido synthetases catalyze the ATP-dependent formation of amino acid conjugates to modulate levels of active plant hormones, including auxins and jasmonates. Initial biochemical studies of various GH3s show that these enzymes group into three families based on sequence relationships and acyl-acid substrate preference (I, jasmonate-conjugating; II, ...

We investigated the condensed-phase reactions of biogenic VOCs with C double bond C bonds (limonene, C(10)H(16), and terpineol, C(10)H(18)O) catalyzed by sulfuric acid by both bulk solution (BS) experiments and gas-particle (GP) experiments using a flow cell reactor. Product analysis by gas chromatography-mass spectrometry (GC-MS) showed that cationic polymerization led ...

CASES DESCRIPTION: This is a retrospective study, based on analysis of data from patients with previous adverse drug reactions admitted to the Allergy and Clinical Immunology Division of both the University of Messina and the University of Bari in the last 4 years. We observed five patients: four of them ...

A library of fused pyridine-4-carboxylic acids (including pyrazolo[3,4-b]pyridines, isoxazolo[5,4-b]pyridines, furo[2,3-b]pyridines, thieno[2,3-b]pyridines, and pyrido[2,3-d]pyrimidines) was generated by Combes-type reaction of acyl pyruvates and electron-rich amino heterocycles followed by hydrolysis of the ester. The library members were also demonstrated to undergo the standard combinatorial transformations including amide coupling and esterification, as well ...

N,N'-pyromelliticdiimido-di-L-alanine (1), N,N'-Pyromelliticdiimido-di-L-phenylalanine (2), and N,N'-Pyromelliticdiimido-di-L-leucine (3) were prepared from the reaction of Pyromellitic dianhydride with corresponding L-amino acids in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. A series of poly (amide-imide)s containing L-amino acids were prepared from the synthesized dicarboxylic acids with ...

The fragmentation reactions of N-monoalkyloxyphosphoryl amino acids (N-MAP-AAs) were studied by electrospray ionization tandem mass spectrometry (ESI-MS). The sodiated cyclic acylphosphoramidates (CAPAs) were formed through a characteristic pentacoordinate phosphate participated rearrangement reaction in the positive-ion ESI-MS/MS and HR-MS/MS of N-MAP-AAs, in which the fragmentation patterns were clearly different from those ...

The reaction of the amyloid beta peptide (Abeta) with hypochlorous acid and hydroxyl radicals was analysed by spectrophotometry and mass spectrometry. N-acetylmethionine, Abeta25-35 and Abeta1-42 reacted rapidly with hypochlorous acid. The relative reaction rates of N-acetylmethionine and Abeta with hypochlorous acid was in the order N-acetylmethionine > Abeta25-35 > Abeta1-42. ...

This study demonstrated a one-step process for direct liquefaction and conversion of wet algal biomass containing about 90% of water to biodiesel under supercritical methanol conditions. This one-step process enables simultaneous extraction and transesterification of wet algal biomass. The process conditions are milder than those required for pyrolysis and prevent ...

Gas-phase reactivity of a positively charged aromatic σ,σ-biradical (N-methyl-6,8-didehydroquinolinium) was examined toward six aliphatic amino acids and 15 dipeptides by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) and laser-induced acoustic desorption (LIAD). While previous studies have revealed that H-atom and NH(2) abstractions dominate the reactions of related monoradicals ...

In order to synthesize a sugar ester at high concentration, 1,2-O-isopropylidene-α-D-glucofuranose (IpGlc), which is one of the sugar acetals and is more hydrophobic than unmodified glucose, was esterified with palmitic acid at 40°C using immobilized lipase from Candida antarctica in some organic solvents or their mixtures. Acetone + t-butyl alcohol ...

Several studies have demonstrated that millions of people globally are potentially exposed to volcanic gases. Hydrogen sulfide is a typical gas in volcanic and geothermal areas. The gas is toxic at high concentrations that predominantly affects the nervous, cardiovascular, and respiratory systems. The WHO air quality guideline for hydrogen sulfide ...

An efficient short protocol for the preparation of N-perfluoroacylated glycals of neuraminic acid, by simple short treatment of differently protected N-acetylneuraminic acid with perfluorinated anhydrides in acetonitrile at 135 degrees C, is reported, together with a rationalitazion of the reaction that allows the alternative formation of N-perfluoroacylated 1,7-lactones to be ...

In the presence of methyl acetate triglycerides such as vegetable oils are transformed simultaneously into the corresponding fatty acid methyl esters and triacetyl glycerol (triacetin). The reaction, catalyzed by lipases, was studied as a function of some critical parameters, such as type of catalyst, enzyme hydration and immobilization support. The ...

A simple colorimetric method for the differentiation of indoleacetic acid (IAA) and indolebutyric acid (IBA) in plant samples is described. The color change is based upon the reaction between the auxins and p-(dimethylamino)benzaldehyde (PDAB, Ehrlich reagent) following the electrophilic substitution reaction mechanism at the indole ring. Using their different response ...

A facile NHC-mediated reaction of aromatic aldehydes with carbon dioxide leading to carboxylic acids is described. The present protocol is mechanistically important, and it can serve as a tool for the sequestration of carbon dioxide.

Substantially enhanced monosaccharide fluorescent sensing in aqueous solutions using a simple phenylboronic acid receptor is achieved by coupling the classic strategy based on saccharide-boronic acid interaction with catalytic Suzuki homocoupling reaction.

The reactions of three isomers of phenyl-substituted propene, trans-beta-methylstyrene, alpha-methylstyrene, and allylbenzene, with atomic oxygen adsorbed on Au(111) have been investigated in order to probe the effect of molecular structure on the selectivity for competing oxidation pathways. Temperature programmed reaction experiments show that these three isomers share common features in ...

A facile and fast one-pot microwave irradiation method has been developed to prepare different shapes of gold nanoparticles capped with a mixture of oleylamine and oleic acid. The size, shape, and morphology of the nanocrystals could be tailored by varying the ratio of oleylamine to oleic acid, the microwave time, ...

Lipases from Rhizomucor miehei and Candida antarctica B were immobilized in hydroxypropylmethyl cellulose organogels based on surfactant-free microemulsions consisting of n-hexane, 1-propanol and water. Both lipases kept their catalytic activity, catalyzing the esterification reactions of various phenolic acids including cinnamic acid derivatives. High reaction rates and yields (up to 94%) ...

Microcrystalline cellulose (MCC) was pretreated with phosphoric acid at 323K for 10h. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) analyses revealed that the fiber surface morphology of pretreated MCC (P-MCC) were uneven and rough with the crystalline diffraction peaks of P-MCC decreased to a distinct range. The X-ray Photoelectron ...

Reductive N-alkylation with acetone and levulinic acid in the presence of sodium cyanoborohydride was applied to chitosan to prepare N-isopropyl and 5-methyl-pyrrolidinone chitosans, respectively. These chitosan derivatives were obtained quantitatively, and the highest degrees of substitution (DS) were achieved for chitosan solutions at the initial pH 4.5-5.0. When the molar ...

A total of eight CF(3)-substituted phenylacetic and mandelic acids are shown to undergo efficient photodecarboxylation (PDC; Phi = 0.37-0.74) in basic aqueous solution to give the corresponding trifluoromethyltoluenes or trifluoromethylbenzyl alcohols. The products are consistent with the almost exclusive formation of benzylic carbanions that subsequently react with water, with minor ...

Thiol-thioester exchange was found to readily generate libraries of cyclic thiodepsipeptides under thermodynamic control, which will enable their use in a variety of dynamic combinatorial chemistry assays. The kinetic determinants of macrocycle formation and the role of amino acid structure on the reaction dynamics are discussed.

Many of the traditional herbal formulations contain extracts of Piper longum and Glycyrrhiza glabra, piperine and glycyrrhetinic acid respectively, being active constituents of these two herbs. An attempt has been made to develop a simple, precise, rapid, and cost-effective high-performance thin-layer chromatographic (HPTLC) method for simultaneous estimation of these in ...

Heterocyclization reactions of pyruvic acids, aromatic aldehydes and 5-amino-N-aryl-1H-pyrazole-4-carboxamides yielding four different types of final compounds are described. The reactions involving arylidenpyruvic acids lead with high degree of selectivity to either 4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids or 5-[(2-oxo-2,5-dihydrofuran-3-yl)amino]-1H-pyrazoles, depending on the catalyst type or temperature regime. The interactions based on arylpyruvic acids can ...

Many serine hydrolases catalyze perhydrolysis, the reversible formation of peracids from carboxylic acids and hydrogen peroxide. Recently, we showed that a single amino acid substitution in the alcohol binding pocket, L29P, in Pseudomonas fluorescens (SIK WI) aryl esterase (PFE) increased the specificity constant of PFE for peracetic acid formation >100-fold ...

The early time dynamics of vibrationally excited glyoxylic acid and of its monohydrate 2,2-dihydroxyacetic acid are investigated by theoretical and spectroscopic methods. A combination of "on-the-fly" dynamical simulations and cavity ring-down spectroscopy on the excited O-H stretching vibrational levels of these molecules observed that conformers that possess the correct structure ...

Nucleation is a fundamental step in atmospheric new-particle formation. However, laboratory experiments on nucleation have systematically failed to demonstrate sulfuric acid particle formation rates as high as those necessary to account for ambient atmospheric concentrations, and the role of sulfuric acid in atmospheric nucleation has remained a mystery. Here, we ...

Amine-transaminases (ATAs, omega-transaminases, omega-TA) are PLP-dependent enzymes that catalyze amino group transfer reactions. In contrast to the widespread and well-known amino acid-transaminases, ATAs are able to convert substrates lacking an alpha-carboxylic functional group. They have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, ...

It was found that oxalic acid is one of the main products in the Briggs-Rauscher oscillating reaction. In nonoscillating solutions, oxidation of iodomalonic acid and/or diiodomalonic acid by Fenton-type reactions also produced oxalic acid as well as I(2). Mesoxalic acid yielded oxalic acid under similar conditions. Tartronic acid was nearly ...

Cellulose is a renewable and widely available feedstock. It is a biopolymer that is typically found in wood, straw, grass, municipal solid waste, and crop residues. Its use as raw material for biofuel production opens up the possibility of sustainable biorefinery schemes that do not compete with food supply. Tapping ...

We introduce a novel approach to compute dissociation free energy and entropy values in simulations that employ a density functional theory description of the acidic moiety and of the solvent. The approach consists of utilizing an alchemical transformation of a weak acid A-COOH into the strong acid B-COOH, which makes ...

The gold/silver-cocatalyzed conversion of aldoximes into primary amides is reported. The reaction, which proceeds under neat and acid-free conditions, allows for the conversion of a range of aldoximes, and is a rare example of cooperative catalysis involving well-defined gold species.

New reactions of azomethine ylides with nontraditional dipolarophiles are reported. Azomethine ylides, formed in situ via decarboxylative condensations of alpha-amino acids with aldehydes, undergo reactions with naphthols, indoles, alkynes, and nitroalkanes.

Mild and efficient Fischer esterification reactions of lactic acid with a variety of straight chain aliphatic alcohols, cyclohexanol and benzyl alcohol were successfully performed using two novel Brønsted acidic ionic liquids that bear an aromatic sulfonic acid group on the imidazolium or pyridinium cation under ultrasound irradiation. These reactions carried ...

An increasing number of reactions of sulfenic acid anions are being demonstrated in the literature. As such, mild, general and reliable means for the generation of sulfenates are due. In the current paper, an addition/elimination of 2-sulfinyl acrylates using various nucleophiles is demonstrated and evaluated as a protocol for alkane- ...

Bifunctional acid-base ionic liquid organocatalysts with different distances between the two sites have been synthesised, and their activity for the Knoevenagel condensation has been tested. As has been found to be the case with enzymes, the distance between the acidic and basic sites determines the activity of the bifunctional organocatalyst, ...

The heterogeneous acid-catalyzed activation step of alkanes leading to the reaction intermediates (carbocationic or alkoxy species) was up to now the matter of a longstanding controversy. Gas chromatography and online mass spectroscopy measurements show that H(2) and methane are formed over H-zeolites, whereas HD and CH(3)D are formed over D-zeolites ...

γ-glutamyltranspeptidase from Pseudomonas nitroreducens IFO12694 (PnGGT) exhibited higher hydrolytic activity than transfer activity, as compared with other γ-glutamyltranspeptidases (GGTs). PnGGT showed little activity towards most of L-amino acids and towards glycyl-glycine, which is often used as a standard γ-glutamyl accepter in GGT transfer reactions. The preferred substrates for PnGGT as ...

The mechanism of all elementary steps involved in the catalytic cycle of benzoylformate decarboxylase (BFD, E.C. 4.1.1.7) to generate the acyloin linkage is investigated by extensive molecular dynamics simulations. Models involving different charge states of amino acids and/or mutants of critical residues were constructed to understand the involvement of the ...

Fatty thiohydroxamic acids (FTAs) have been successfully synthesized from palm olein and thiohydroxamic acid by a one-step lipase catalyzed reaction. The use of immobilized lipase (Lipozyme RMIM) as the catalyst for the preparation reaction provides an easy isolation of the enzyme from the products and other components in the reaction ...

Peroxynitrite (ONOO(-)) and hypochlorous acid (HOCl) are two highly reactive oxygen species generated in biological systems. The overproduction of peroxynitrite or hypochlorous acid is implicated in a broad array of human pathologies including vascular, immunological, and neurodegenerative diseases. However, unambiguous detection of these reactive oxygen species has been relatively difficult ...

Enzymatic synthesis of phospholipids (PLs) containing polyunsaturated fatty acids (PUFAs) was studied. The main purpose was to establish an efficient production method for PLs containing docosahexaenoic acid or eicosapentaenoic acid using only food-compatible reagents. Phospholipase A(2) (PLA(2))-mediated ester synthesis was employed to introduce the PUFAs into the sn-2 position of ...

It was found that the inhibitory effect of resorcinol is less pronounced if it is added in a later stage of the Briggs-Rauscher reaction, which indicates that an accumulating intermediate--most probably iodomalonic acid--can suppress the inhibition. In fact, when iodomalonic acid was added to the reaction mixture, the inhibitory period ...

A set of experiments was carried out to investigate the chemical stability of 5-o-caffeoylquinic acid (5-CQA) in the presence of superheated steam. A batch cylindrical reactor made of glass and isothermally operated between 398 and 499 K was used in the experiments. A high-performance liquid chromatograph equipped with a diode ...

The tetrathionate-hypochlorous acid reaction has been investigated in nearly neutral medium at I = 0.5 M ionic strength and T = 25.0 +/- 0.1 degrees C in dihydrogen-phosphate-hydrogen-phosphate buffer by UV-vis spectrophotometry. In excess of hypochlorous acid, the stoichiometry was found to be S(4)O(6)(2-) + 7HOCl + 3H(2)O --> 4SO(4)(2-) ...

A recycling method using sub-critical water hydrolysis to convert hog hair from slaughterhouses into amino acids was developed. The influence of the reaction parameters such as temperature, time of reaction and initial substrate concentration were investigated in a batch reactor. The quality and quantity of amino acids in hydrolysates were ...

The exchange of the monocarboxylate ligand of the zirconium methacrylate oxocluster Zr(6)O(4)(OH)(4)(OMc)(12) (OMc = CH(2)=CH(CH(3))COO) with dicarboxylic acids (trans,trans muconic acid and terephthalic acid) leads to porous zirconium dicarboxylates exhibiting the UiO-66 architecture; the mild reaction conditions allow the control of their particle size.

The OOH radical reactions with allicin and its Cope elimination products (2-propenesulfenic acid and thioacrolein) in aqueous solution have been studied. The CBS-QB3 quantum chemistry method has been used, with geometries and frequencies at BHandHLYP/6-311++G(d,p) level and conventional transition state theory. 2-Propenesulfenic acid is predicted to be over 1000 times ...