Selective chemical oxidation and depolymerization of switchgrass [corrected] (Panicum virgatum L.) xylan with [corrected] oligosaccharide product analysis by mass spectrometry

Xylan is a barrier to enzymatic hydrolysis of plant cell walls. It is well accepted that the xylan layer needs to be removed to efficiently hydrolyze cellulose; consequently, pretreatment conditions are (in part) optimized for maximal xylan depolymerization or displacement. Xylan consists of a long chain of β-1,4-linked xylose units substituted with arabinose (typically α-1,3-linked in grasses) and glucuronic acid (α-1,2-linked). Xylan has been proposed to have a structural function in plants and therefore may play a role in determining biomass reactivity to pretreatment. It has been proposed that substitutions along xylan chains are not random and, based upon studies of pericarp xylan, are organized in domains that have specific structural functions. Analysis of intact xylan is problematic because of its chain length (> degree of polymerization (d.p.) 100) and heterogeneous side groups. Traditionally, enzymatic end-point products have been characterized due to the limited products generated. Analysis of resultant arabino-xylo-oligosaccharides by mass spectrometry is complicated by the isobaric pentose sugars that primarily compose xylan. In this report, the variation in pentose ring structures was exploited for selective oxidation of the arabinofuranose primary alcohols followed by acid depolymerization to provide oligosaccharides with modified arabinose branches intact. Switchgrass samples were analyzed by hydrophilic interaction chromatography (HILIC)-liquid chromatography (LC)-mass spectrometry/mass spectrometry (MSMS) and off-line nanospray MS to demonstrate the utility of this chemistry for determination of primary hydroxyl groups on oligosaccharide structures, with potential applications for determining the sequence of arabino-xylo-oligosaccharides present in plant cell wall material.     

Formal intermolecular [2 + 2] cycloaddition reaction of allenamide [corrected] with alkenes via gold catalysis

An efficient method was developed to construct the densely functionalized cyclobutane[corrected] adducts through formal intermolecular cycloaddition of allenamides [corrected] with electron-rich olefins via gold catalysis, in which vinyl ethers/amides and electron-rich styrenes worked very well. In addition, a series of allenamide [corrected] dimerization products were prepared from the same allenamide [corrected] substrates.     

Naravelia zeylanica [corrected] occurrence of primary benzamides in flowering plants

Extract of Naravelia zeylanica (Ranunculaceae) yielded three simple benzamides, 3,4-methylenedioxybenzamide, 4-methoxybenzamide and 4-hydroxy-3-methoxybenzamide. These simple C6C1 metabolites have been encountered as natural products for the first time. The compounds were identified by direct comparison of their spectral (1H- and 13C-NMR) and chromatographic (GCMS) data with those of authentic samples. Authentic 4-hydroxy-3-methoxybenzamide was synthesized in one step by treatment of 4-hydroxy-3-methoxybenzonitrile with sodium perborate. Authentic 3,4-methylenedioxybenzamide was synthesized from the corresponding acid.     

Physicochemical characterization of n-butyl-3-methylpyridinium dicyanamide [corrected] ionic liquid

The room temperature ionic liquid n-butyl-3-methylpyridinium dicyanamide has been characterized. Physicochemical properties such as density, speed of sound, refractive index, surface tension, and kinematic viscosity of the studied liquid have been experimentally measured in a wide range of temperatures. From results, coefficients of thermal expansion, molar refractions, dynamic viscosities and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been derived. We have analyzed the achieved results for evaluating the effect of the anionic structure in these properties, getting interesting results which lead us to a better understanding of the behavior of the ions in the fluids. Moreover, thermal properties of several pyridinium-based ionic liquids have been investigated. Finally, from both dynamic viscosity values and glass transition temperature of the studied liquids, a detailed analysis of the behavior in fragility terms has been performed.     

Rhodium-catalyzed carbonylative [2+2+1] cycloaddition reactions: catalytic formation of bicyclic cyclohexenones [corrected

The rhodium-catalyzed carbonylative [3+2+1] cycloaddition of trienes into bicyclohexenones has been developed. The carbonylated cycloaddition products have a high regioselectivity. This catalytic system tolerates functionalities including ether, sulfonamide, and ester.     

Optimal dynamic discrimination of similar [corrected] quantum systems in the presence of decoherence

Optimal dynamic discrimination (ODD) of a mixture of similar quantum systems with time series signals enables the extraction of the associated concentrations with reasonable levels of laser-pulse noise, signal detection errors, and imperfect signal detector resolution [Li et al., J. Chem. Phys. 122, 154103 (2005)]. The ODD paradigm is reexpressed in the density-matrix formulation to allow for the consideration of environmental decoherence on the quality of the extracted concentrations, along with the above listed factors. Simulations show that although starting in a thermally mixed state along with decoherence can be detrimental to discrimination, these effects can be counteracted by seeking a suitable optimal control pulse. Additional sampling of the temporal data also aids in extracting more information to better implement ODD.     

Phenyl tributylstannyl selenide as a promising reagent for introduction [corrected] of the phenylseleno group

A new synthetic method of organoselenium compounds has been developed. When phenyl tributylstannyl selenide (PhSeSnBu(3)) was allowed to react with acyl or aroyl chlorides in the presence of a catalytic amount of a palladium complex such as Pd(PPh(3))(4), Se-phenyl selenol esters were obtained in moderate to good yields. Similarly, the palladium complex catalyzed the reaction of PhSeSnBu(3) with alpha-halo carbonyl compounds to afford the corresponding alpha-phenyseleno carbonyl compounds in moderate yields.     

Chromatographic and electrophoretic methods for the analysis of phenethylamine [corrected] alkaloids in Citrus aurantium

Citrus aurantium (bitter orange) is a plant belonging to the family Rutaceae, whose fruit extracts have been used recently for the treatment of obesity. The most important biologically active constituents of the C. aurantium fruits are phenethylamine alkaloids (i.e. octopamine, synephrine, tyramine, N-methyltyramine and hordenine). Synephrine is a primary synthesis compound with pharmacological activities such as vasoconstriction, elevation of blood pressure and relaxation of bronchial muscle. Synephrine is present in the peel and the edible part of Citrus fruit. Of the adrenergic amines of natural origin, synephrine has been found to be the main constituent of C. aurantium fruits and extracts; the other alkaloids are either absent or present in only low concentrations. It is known that synephrine and the other amines found in C. aurantium have adverse effects on the cardiovascular system, owing to adrenergic stimulation. In light of the great commercial proliferation of C. aurantium herbal medicines in recent years, this review provides an overview of various extraction, separation and detection techniques employed for the qualitative and quantitative determination of the alkaloids in C. aurantium and related species. The application of chromatographic and electrophoretic methods for the separation and determination of these active components in C. aurantium plant material and derivatives are described. Since synephrine is a chiral compound, enantioselective chromatographic and electrophoretic techniques for the analysis of synephrine enantiomers in natural products are presented. Furthermore, examples of identification of these active compounds in complex matrices by hyphenated methods, such as gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry, are described. The advantages and limitations of these separation and identification methods are assessed and discussed.     

Total synthesis of natural (+)- [corrected] and ent-(-)-4-desacetoxy-6,7-dihydrovindorosine [corrected] and natural and ent-minovine: oxadiazole tandem intramolecular Diels-Alder/1,3-dipolar cycloaddition reaction

Efficient and unusually concise total syntheses of both enantiomers of the Aspidosperma alkaloids 4-desacetoxy-6,7-dihydrovindorosine (12) and minovine (1) are detailed. A tandem intramolecular Diels-Alder/1,3-dipolar cycloaddition reaction of the 1,3,4-oxadiazole 8, in which three new rings, four new C-C bonds, and five stereocenters are formed, is a key step in the sequence. The availability of optically active material permitted an assessment of the enantiomeric integrity of minovine and the source of its reported unusual optical rotation. [Reaction: see text]     

Improved sensitivity for some [corrected] metal ions by use of sulfide in the Belousov-Zhabotinskii oscillating reaction

A highly sensitive method for the determination of trace amounts of transition metal ions by use of sulfide in the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B-Z reaction for transition metal ions, such as Ag⁺, Pb²⁺, Hg²⁺, Cd²⁺, Cu²⁺,and Bi³⁺. Results showed that the variational ratio of oscillating period (P_R) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10⁻¹² mol L⁻¹. Various influencing factors on the determination were also examined.     

Synthesis of vaniprevir (MK-7009): lactamization to prepare a 20-membered [corrected] macrocycle

Development of a practical synthesis of MK-7009, a 20-membered [corrected] macrocycle, is described. A variety of ring-closing strategies were evaluated, including ring-closing metathesis, intermolecular palladium-catalyzed cross-couplings, and macrolactamization. Ring closure via macrolactamization was found to give the highest yields under relatively high reaction concentrations. Optimization of the ring formation step and the synthesis of key intermediates en route to MK-7009 are reported.     

Total synthesis, structural revision, and absolute configuration of (-)-clavosolide [corrected] A

[reaction: see text] Enantioselective synthesis of 3, a revised structure for clavosolide A, was completed. Both (1)H and (13)C NMR spectra of the natural and synthetic compounds were identical, and optical rotation measurements identified the absolute configuration of the natural clavosolide A as [corrected] 3.     

Theoretical study and X-ray determination of bianthronyl [corrected] : long C-C bond length and preferred gauche conformation

Five X-ray crystallographic structures of bianthronyl (1, 2b-5b) revealed the presence of long central C(sp3)-C(sp3) bonds (> or =1.60 A) and mostly gauche conformation. DFT calculations were carried out to study the structural features of bianthronyl and related model molecules [corrected]. Our B3LYP/6-31G gas-phase calculation results suggest that steric effect plays a role in causing the long C-C sigma bond length (>1.60 A), nonplanarity of the anthracenone moiety (>20 degrees ), and preferred gauche conformation. However, when the gauche preference is weak, environmental effects such as solvation and packing forces can reverse it. As the degree of nonplanarity of the anthracenone moiety is consistently larger in the anti conformation than in the gauche and the ease of achieving nonplanarity is determined by flexibility of the central six-membered rings directly connected to the C(sp3)-C(sp3) bond, one way to control the structure and anti-gauche energy difference of closely related compounds is by changing the clamping group (Z) in the central six-membered ring.     

Solvent-resistant photocurable liquid fluoropolymers for microfluidic device fabrication [corrected

We report the first fabrication of a solvent-compatible microfluidic device based on photocurable "Liquid Teflon" materials. The materials are highly fluorinated functionalized perfluoropolyethers (PFPEs) that have liquidlike viscosities that can be cured into tough, highly durable elastomers that exhibit the remarkable chemical resistance of fluoropolymers such as Teflon. Poly(dimethylsiloxane) (PDMS) elastomers have rapidly become the material of choice for many recent microfluidic device applications. Despite the advantages of PDMS in relation to microfluidics technology, the material suffers from a serious drawback in that it swells in most organic solvents. The swelling of PDMS-based devices in organic solvents greatly disrupts the micrometer-sized features and makes it impossible for fluids to flow inside the channels. Our approach to this problem has been to replace PDMS with photocurable perfluoropolyethers. Device fabrication and valve actuation were accomplished using established procedures for PDMS devices. The additional advantage of photocuring allows fabrication time to be decreased from several hours to a matter of minutes. The PFPE-based device exhibited mechanical properties similar to those of Sylgard 184 before and after curing as well as remarkable resistance to organic solvents. This work has the potential to expand the field of microfluidics to many novel applications.     

The synthesis of [1]benzothieno[2,3-c]quinolines, [1]benzothieno[2,3-c][1,2,4]triazolo[4,3-a]quinoline,and [1]benzothieno[2,3-c]tetrazolo[1,5-a]quinoline

Photocyclization of 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamide 10 afforded [1]benzothieno[2,3-c]-quinolin-6(5H)-one 11 which was chlorinated to 6-chloro[1]benzothieno[2,3-c]quinoline 12 followed by dechlorination to give [1]benzothieno[2,3-c]quinoline 5 . A series of 6-substituted alkoxy and thioalkoxy[1]benzothieno[2,3-c]quinoline derivatives were prepared along with the N-methyl quaternary salt 13 of 5 . 6-Chloro[1]-benzothieno[2,3-c]quinoline 12 was converted into 6-hydrazino[1]benzothieno[2,3-c]quinoline 23 which upon treatment with formic acid yielded [1]benzothieno[2,3-c][1,2,4]triazolo[4,3-a]quinoline 6 . Treatment of 23 with nitrous acid resulted in [1]benzothieno[2,3-c]tetrazolo[1,5-a]quinoline 7 . Compounds 6 and 7 are novel heterocyclic ring systems.     

New [g]-fused [1,2,4]triazolo[1,5-c]pyrimidines: Synthesis of pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidine,pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine and [1,2,4]triazolo[1,5-c]pteridine derivatives

A number of 2-aryl-substituted pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidines and [1,2,4]triazolo[1,5-c]pteridines 11,12a,b,e , their corresponding 5-carbonyl derivatives 7,8a,b,e and some pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidin-5-ones 7,8c,d have been synthesized, according to different pathways. The new tricyclic heterocycles were prepared with the aim of studying their possible benzodiazepine receptors affinity.     

Synthesis and characterization of [1,2,5]chalcogenazolo[3,4-f]benzo[1,2,3]triazole and [1,2,3]triazolo[3,4-g]quinoxaline derivatives

The synthesis and characterization is reported of low bandgap [1,2,5]chalcogenazolo[3,4-f]benzo[1,2,3]triazole and [1,2,3]triazolo[3,4-g]quinoxaline derivatives that display higher solubility and stability then their thiadiazole counterparts, [1,2,5]chalcogenazolo[3,4-f]benzo[2,1,3]thiadiazole and [1,2,5]thiadiazolo[3,4-g]quinoxaline, respectively.     

[1.1.1.1.1]paracyclophane and [1.1.1.1.1.1]paracyclophane

The first syntheses of [1.1.1.1.1]paracyclophane ($\text{1}$) and [1.1.1.1.1.1]paracyclophane ($\text{2}$) are described, featuring a trifluoroacetic acid promoted Friedel-Crafts cycloalkylation as the final step.