Maxwell-Wagner Effect Applied to Microwave-Induced Self-Ignition: A Novel Approach for Carbon-Based Materials.

A new method for analytical applications based on the Maxwell-Wagner effect is proposed. Considering the interaction of carbonaceous materials with an electromagnetic field in the microwave frequency range, a very fast heating is observed due to interfacial polarization that results in localized microplasma formation. Such effect was evaluated in this work using a monomode microwave system, and temperature was recorded using an infrared camera. For analytical applications, a closed reactor under oxygen pressure was evaluated. The combination of high temperature and oxidant atmosphere resulted in a very effective self-ignition reaction of sample, allowing its use as sample preparation procedure for further elemental analysis. After optimization, a high sample mass (up to 600 mg of coal and graphite) was efficiently digested using only 4 mol L-1 HNO3 as absorbing solution. Several elements (Ba, Ca, Fe, K, Li, Mg, Na, and Zn) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Accuracy was evaluated by using a certified reference material (NIST 1632b). Blanks were negligible, and only a diluted solution was required for analytes absorption preventing residue generation and making the proposed method in agreement with green chemistry recommendations. The feasibility of the proposed method for hard-to-digest materials, the minimization of reagent consumption, and the possibility of multi elemental analysis with lower blanks and better limits of detection can be considered as the main advantages of this method.

Lanostane-type triterpenes from the fungal endophyte Scleroderma UFSMSc1 (Persoon) Fries.

Two lanostane triterpenoids (sclerodols A and B) were isolated from the culture of the Eucalyptus grandis derived from the endophyte Scleroderma UFSM Sc1(Persoon) Fries together with three known compounds: one related triterpenoid lanosta-8,23-dien-3ß,25-diol, the disaccharide α,ß-trehalose, and the sugar alcohol mannitol. Their structures were elucidated on the basis of 2D NMR, HRME, and single-crystal X-ray diffraction data. The methanol crude extract and the isolated lanostane triterpenoids showed promising anticandidal activities.

Redetermination of cis-bis-(ethyl-ene-diamine-κ(2) N,N')bis-(nitrito-κN)cobalt(III) (ethyl-enediamine-κ(2) N,N')tetra-kis-(nitrito-κN)cobaltate(III) monohydrate.

The structure of the title compound, [Co(NO2)2(NH2CH2CH2NH2)2][Co(NO2)4(NH2CH2CH2NH2)]·H2O, was redetermined with a modern CCD-equipped diffractometer. In comparison with the original determination based on photographic data [Kushi et al. (1976 ▶). Inorg. Nucl. Chem. Lett. 12, 629-633], the current study allows the location of reliable postions for the H atoms and thus leads to better understanding of the inter-ionic and inter-molecular inter-actions. The crystal structure consists of an octa-hedrally coordinated cationic Co(III) complex ion, an octa-hedrally coordinated anionic Co(III) complex ion and a lattice water mol-ecule. The complex cation, complex anion and lattice water mol-ecule are connected by an intricate network of O-H⋯O and N-H⋯O hydrogen bonds, forming a three-dimensional structure.

(9H-Fluoren-9-yl)(phen-yl)phosphinic acid.

The crystal structure of the title compound, C19H15O2P, features pairs of mol-ecules joined by O-H⋯O hydrogen bonds across crystallographic inversion centers. In addition, π-π inter-actions, with a centroid-centroid distance of 3.6273 (9) Šbetween the fluorene ring systems, connect the dimers into chains along [01-1]. The three rings make dihedral angles of 1.34 (9), 1.52 (10) and 1.51 (7)° with each other.

Absolute configuration of franganine.

The absolute configuration of franganine (1), a cyclopeptide alkaloid isolated from the methanol root bark extract of Discaria americana, was established on the basis of detailed NMR spectroscopic data and X-ray diffraction analysis of its salt (2).

rac-Eth-yl(phen-yl)phosphinic acid.

The crystal structure of the title compound, C8H11O2P, features O-H⋯O hydrogen bonds, which link mol-ecules related by the b-glide plane into chains along [010].

Synthesis of unprotected glyco-alkynones via molybdenum-catalyzed carbonylative Sonogashira cross-coupling reaction.

Herein we report a novel Mo-catalyzed carbonylative Sonogashira cross-coupling between 2-iodoglycals and terminal alkynes. The reaction displays major improvements compared to a related Pd-catalyzed procedure previously published by our group, such as utilizing unprotected sugar derivatives as starting materials and tolerance to substrates bearing chelating groups. In this work we also demonstrate the utility of the glyco-alkynone products as platform for further functionalization by synthesizing glyco-flavones via Au-catalyzed 6-endo-dig cyclization.

Alkaloids from the stem barks of Scutia buxifolia Reissek (Rhamnaceae): Structures and antimicrobial evaluation.

A reinvestigation of the chemical constituents of the stem barks of Scutia buxifolia, a member of the Rhamnaceae, resulted, along with the known alkaloids scutianine C and scutianene L, in the isolation of three undescribed diastereoisomeric alkaloids - scutianine N, 27-epi-scutianine N and 3, 4, 7-tri-epi-scutianine N -, one undescribed non macrocyclic alkaloid - scutianine Q - and a neutral compound -scutianene M. Their structures were determined using extensive NMR techniques and HRMS. The absolute configurations of the stereogenic centers of the three diastereoisomeric alkaloids have been assigned by gas chromatography employing modified cyclodextrins as chiral stationary phases. Scutianine Q had its structure and stereochemistry defined by single crystal X-ray crystallographic analysis. All tested compounds showed good to moderate antibacterial activity (MICs between 1.56 and 100 µg mL-1) when evaluated in vitro against a panel of Gram-positive and Gram-negative bacteria. Some stereochemistry-activity relationships have been identified for the antibacterial activity of diastereoisomeric alkaloids against the Gram-negative bacteria Enterobacter aerogenes. The alkaloid 27-epi-scutianine N was as active as the standard antibiotic chloramphenicol (MIC = 1.56 µg mL-1), while scutianine N and 3,4,27-tris-epi-Scutianine N were inactive (>100 µg mL-1).

New cyclopeptide alkaloid of Condalia buxifolia and the absolute stereochemistry of Condaline A.

During the course of a study of Condalia buxifolia (Rhamnaceae), one new cyclopeptide alkaloid condaline B (1), together with six known cyclopeptide alkaloids, condaline A (2), and the scutianines B (3), - D (4) and -E (5), frangulanine (6), and 3,4,28-tris-epi-scutianene N (7), were isolated from the rind bark of Condalia buxifolia. Their structures have been confirmed through spectroscopic analyses such as 1D and 2D NMR experiments. The absolute stereochemistry of condaline A (2), was elucidated by X-ray crystal structure determination of its HI salt. In addition, condaline B (1) was obtained synthetically through a structural transformation of condaline A. Meanwhile, the crude methanol extract, the basic ether fraction, and alkaloids 1-7 were tested against various strains of Gram-positive and Gram-negative bacteria and fungus, showing promising antimicrobial activity.

Benz-yl(phen-yl)phosphinic acid.

The title compound, C(13)H(13)O(2)P, crystallized as enanti-omerically pure crystals; for the crystal measured, the P atom has R stereochemistry. The crystal structure displays O-H⋯O hydrogen bonding, which links individual mol-ecules related by a 2(1) screw axis parallel to the crystallographic a-axis direction into continuous chains.

Meth-yl(phen-yl)phosphinic acid.

The crystal structure of the title compound, C(7)H(9)O(2)P, displays O-H⋯O hydrogen bonding , which links individual mol-ecules related via the c-glide plane and translational symmetry along the crystallographic b-axis direction into continuous chains.

Physicochemical characterization, released profile, and antinociceptive activity of diphenhydraminium ibuprofenate supported on mesoporous silica.

The thermal, physical, and morphological properties of diphenhydraminium ibuprofenate ([DIP][IBU]) adsorbed onto mesoporous silica (SiO2-60 Šand SiO2-90 Å) from solution were determined. The thermal, physical, and morphological properties of [DIP][IBU] supported on silica were determined. The adsorption of [DIP][IBU] on the pores and surface of silica was proven by N2 adsorption/desorption isotherms. Additionally, release profiles were determined for all systems, and the antinociceptive activity of neat [DIP][IBU] and [DIP][IBU] supported on silica were determined. The interaction of [DIP][IBU] and silica was dependent on pore size, with the formation of a [DIP][IBU] monolayer on SiO2-60 and a multilayer on SiO2-90. The release profile was sustained and slow and dependent on the pore size of the silica, in which the smaller the pore size, the faster the release. The nociceptive evaluation showed that [DIP][IBU] presents a greater (99.21 ±â€¯0.85%) antinociceptive effect than the ibuprofen (46 ±â€¯4.3%). Additionally, [DIP][IBU] on SiO2-60 (90 ±â€¯5.8%) had a greater antinociceptive effect than on SiO2-90 (73 ±â€¯13.2%), which indicates that in vivo tests are in accordance with the in vitro experiments.

Quinolone alkaloids from Waltheria douradinha.

A phytochemical investigation of the stems of Waltheria douradinha resulted in isolation of two 4-quinolone alkaloids, waltherione B and vanessine, along with three known alkaloids, waltherione A, antidesmone and O-methyltembamide. Their structures were elucidated on the basis of their 2D NMR spectroscopic analyses, and from X-ray crystallographic analysis of waltherione A and the O-methyl derivative of waltherione B. Additionally, waltherione B and vanessine, and the O- and N-methyl derivatives of waltherione A and waltherione B, were evaluated for their antimicrobial activities; only vanessine displayed any (weak) antimicrobial activity.

Design and microwave-assisted synthesis of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles: novel agents with analgesic and anti-inflammatory properties.

In this work, we reported the synthesis and evaluation of the analgesic and anti-inflammatory properties of novel 3- or 4-substituted 5-trifluoromethyl-5-hydroxy-4,5-dihydro-1H-1-carboxyamidepyrazoles (where 3-/4-substituent=H/H, Me/H, Et/H, Pr/H, i-Pr/H, Bu/H, t-Bu/H, Ph/H, 4-Br-Ph/H and H/Me) designed in the exploration of the bioisosteric replacement of benzene present in salicylamide with a 5-trifluoromethyl-4,5-dihydro-1H-pyrazole scaffold. Target compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trifluoromethyl-3-alken-2-ones with semicarbazide hydrochloride through a rapid one-pot reaction via microwave irradiation. In addition to spectroscopic data, the structure of the compounds was supported by X-ray diffraction. Subcutaneous administration of the 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles decreased pain-related behavior during neurogenic and inflammatory phases of the formalin test in mice. Moreover, the more active analgesic compounds (3-/4-=Et/H and H/Me) significantly decreased carrageenan-induced paw edema in mice. The data obtained in this work suggest that the synthesized compounds could be promising candidates for the future development of novel analgesic and anti-inflammatory agents.

A centrosymmetric polymorph of chloridotris(triphenylphosphine-kappaP)copper(I) at 150 K.

This study characterizes a new polymorph of the title compound, [CuCl(C18H15P)3], and analyses the influence of the extensive network of weak hydrogen-bonding interactions in the generation of this different crystal structure. The compound crystallizes in the centrosymmetric space group C2/c with two crystallographically independent molecules per asymmetric unit, in contrast with the previously determined polymorph which crystallizes in the noncentrosymmetric space group P3 with three crystallographically independent molecules in the asymmetric unit, each with crystallographically imposed C3 symmetry [Gill, Mayerle, Welcker, Lewis, Ucko, Barton, Stowens & Lippard (1976). Inorg. Chem. 15, 1155-1168]. The geometries of the two molecules of the title compound are very similar, with each having an approximately tetrahedral coordination around the central Cu atom and approximate C(s) molecular symmetry. The molecules pack in chains parallel to the crystallographic b axis, connected by C-H...Cl and C-H...pi(phenyl) hydrogen bonds.

Synthesis of glycal amides from amino acid esters by carbonylative coupling reaction

Glycal amides were prepared for the first time by reacting 2-iodo-D-glycals with L-amino acid esters via a Pd-catalyzed carbonylative cross-coupling reaction, by using Mo(CO)6 as the carbon monoxide source. Glycal amides were synthesized in moderate to good yields under our optimized conditions. In addition, the acetyl groups of the glucal amides could be readily removed to obtain the corresponding trihydroxy derivatives in good yields.

Synthesis of unprotected glyco-alkynones via molybdenum-catalyzed carbonylative Sonogashira cross-coupling reaction

Herein we report a novel Mo-catalyzed carbonylative Sonogashira cross-coupling between 2-iodoglycals and terminal alkynes. The reaction displays major improvements compared to a related Pd-catalyzed procedure previously published by our group, such as utilizing unprotected sugar derivatives as starting materials and tolerance to substrates bearing chelating groups. In this work we also demonstrate the utility of the glyco-alkynone products as platform for further functionalization by synthesizing glyco-flavones via Au-catalyzed 6-endo-dig cyclization.

Identification of 1,3-dialkylimidazolium salt supramolecular aggregates in solution.

The nature of the interactions between 1,3-dialkylimidazolium cations and noncoordinating anions such as tetrafluoroborate, hexafluorophosphate, and tetraphenylborate has been studied in the solid state by X-ray diffraction analysis and in solution by (1)H NMR spectroscopy, conductivity, and microcalorimetry. In the solid state, these compounds show an extended network of hydrogen-bonded cations and anions in which one cation is surrounded by at least three anions and one anion is surrounded by at least three imidazolium cations. In the pure form, imidazolium salts are better described as polymeric supramolecules of the type {[(DAI)(3)(X)](2+)[(DAI)(X)(3)](2-)}(n) (where DAI is the dialkylimidazolium cation and X is the anion) formed through hydrogen bonds of the imidazolium cation with the anion. In solution, this supramolecular structural organization is maintained to a great extent, at least in solvents of low dielectric constant, indicating that mixtures of imidazolium ionic liquids with other molecules can be considered as nanostructured materials. This model is very useful for the rationalization of the majority of the unusual behavior of the ionic liquids.

Crystal structure of 4-formyl-pyridine semicarbazone hemihydrate.

The mol-ecule of the title compound C7H8N4O·0.5H2O, alternatively called (E)-1-(pyridin-4-yl-methyl-ene)semi-carb-azide hemihydrate, is in the E conformation and is almost planar; the r.m.s. deviation of the positions of the atoms of the pyridine ring from the best-fit plane is 0.0039 Å. The C, N and O atoms of the rest of the mol-ecule sits close on this plane with a largest deviation of 0.115 (4) Šfor the O atom of the semicarbazone moiety. There is an intra-molecular N-H⋯N hydrogen bond. In the crystal, mol-ecules are linked into an infinite three-dimensional network by classical N-H⋯Os (s = semicarbazone) and Ow-H⋯N (w = water) hydrogen bonds.

A new sesquiterpene lactone and other constituents of Moquiniastrum polymorphum subsp. floccosum (Asteraceae).

A new guaianolide, 1S, 3S, 5R, 6S, 7S, 11R-l-hydroxy-11α,13-dihydrozaluzanin C (1), was isolated from Moquiniastrum polymorphum subsp. floccosum trunk bark, together with fifteen known compounds, which were identified as 11α,13-dihydroglucozaluzanin C (2), 8α-hydroxy-11α,13-dihydrozaluzanin C (3), zaluzanin C (4), gochnatiolide B (5), ethyl caffeate (6), methyl chlorogenate (7), ethyl chlorogenate (8), methyl 3,5-dicaffeoyl quinate (9), ethyl 3,5-dicaffeoyl quinate (10), methyl 4,5-dicaffeoyl quinate (11), ethyl 4,5-dicaffeoyl quinate (12), ethyl 3,4-dicaffeoyl quinate (13), 3,5-dicaffeoyl quinic acid (14), 4,5-dicaffeoyl quinic acid (15), and 3,4-dicaffeoyl quinic acid (16). With the exception of 5, all known compounds are being reported for the first time in M. polymorphum.