Solidified floating organic drop microextraction (SFODME) for the simultaneous analysis of three non-steroidal anti-inflammatory drugs in aqueous samples by HPLC.

In this work, a liquid-liquid microextraction methodology using solidified floating organic drop (SFODME) was combined with liquid chromatography and UV/Vis detection to determine non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (NPX), diclofenac (DCF), and mefenamic acid (MFN) in tap water, surface water, and seawater samples. Parameters that can influence the efficiency of the process were evaluated, such as the type and volume of the extractor and dispersive solvents, effect of pH, agitation type, and ionic strength. The optimized method showed low detection limits (0.09 to 0.25 µg L-1), satisfactory recovery rates (90 to 116%), and enrichment factors in the range between 149 and 199. SFODME showed simplicity, low cost, speed, and high concentration capacity of the analytes under study. Its use in real samples did not demonstrate a matrix effect that would compromise the effectiveness of the method, being possible to apply it successfully in water samples with different characteristics.

Synthesis of novel bis-1,5-disubstituted-1H-tetrazoles by an efficient catalyst-free Ugi-azide repetitive process.

A series of five novel bis-1,5-disubstituted-1H-tetrazoles (bis-1,5-DS-1H-T) were quickly prepared by a catalyst-free Ugi-azide repetitive process from easily accessible starting materials in excellent yields, either at room temperature (88%-95%) or using mild MW-heating conditions (80%-91%). These molecules may have a wide range of applications, such as chelating agents, organocatalysts and luminescent materials, and mainly as bioactive compounds.

Concise and straightforward asymmetric synthesis of a cyclic natural hydroxy-amino acid.

An enantioselective total synthesis of the natural amino acid (2S,4R,5R)-4,5-di-hydroxy-pipecolic acid starting from D-glucoheptono-1, 4-lactone is presented. The best sequence employed as a key step the intramolecular nucleophilic displacement by an amino function of a 6-O-p-toluene-sulphonyl derivative of a methyl D-arabino-hexonate and involved only 12 steps with an overall yield of 19%. The structures of the compounds synthesized were elucidated on the basis of comprehensive spectroscopic (NMR and MS) and computational analysis.

A facile and convenient sequential homobimetallic catalytic approach towards ß-methylstyrenes. A one-pot Stille cross-coupling/isomerization strategy.

An efficient one-pot synthetic approach towards ß-methylstyrenes is reported. The transformation, based on sequential homobimetallic catalysis, involves a Stille cross-coupling reaction between aryl halides and allyltributylstannane, followed by an in situ palladium-catalyzed conjugative isomerization. The reaction was optimized, and the best results were obtained with 10 mol% Pd(PPh3)2Cl2, 8.0 equiv. LiCl, and 0.5 equiv. PPh3 in diglyme at 130 °C for 12 h. It was demonstrated that the reaction tolerates a wide variety of functional groups.

Classification of edible oils and modeling of their physico-chemical properties by chemometric methods using mid-IR spectroscopy.

This research work describes two studies for the classification and characterization of edible oils and its quality parameters through Fourier transform mid infrared spectroscopy (FT-mid-IR) together with chemometric methods. The discrimination of canola, sunflower, corn and soybean oils was investigated using SVM-DA, SIMCA and PLS-DA. Using FT-mid-IR, DPLS was able to classify 100% of the samples from the validation set, but SIMCA and SVM-DA were not. The quality parameters: refraction index and relative density of edible oils were obtained from reference methods. Prediction models for FT-mid-IR spectra were calculated for these quality parameters using partial least squares (PLS) and support vector machines (SVM). Several preprocessing alternatives (first derivative, multiplicative scatter correction, mean centering, and standard normal variate) were investigated. The best result for the refraction index was achieved with SVM as well as for the relative density except when the preprocessing combination of mean centering and first derivative was used. For both of quality parameters, the best results obtained for the figures of merit expressed by the root mean square error of cross validation (RMSECV) and prediction (RMSEP) were equal to 0.0001.

Rapid characterization of transgenic and non-transgenic soybean oils by chemometric methods using NIR spectroscopy.

Near infrared (NIR) spectroscopy and multivariate classification were applied to discriminate soybean oil samples into non-transgenic and transgenic. Principal Component Analysis (PCA) was applied to extract relevant features from the spectral data and to remove the anomalous samples. The best results were obtained when with Support Vectors Machine-Discriminant Analysis (SVM-DA) and Partial Least Squares-Discriminant Analysis (PLS-DA) after mean centering plus multiplicative scatter correction. For SVM-DA the percentage of successful classification was 100% for the training group and 100% and 90% in validation group for non transgenic and transgenic soybean oil samples respectively. For PLS-DA the percentage of successful classification was 95% and 100% in training group for non transgenic and transgenic soybean oil samples respectively and 100% and 80% in validation group for non transgenic and transgenic respectively. The results demonstrate that NIR spectroscopy can provide a rapid, nondestructive and reliable method to distinguish non-transgenic and transgenic soybean oils.

Event-based criteria in GT-STAF information indices: theory, exploratory diversity analysis and QSPR applications.

Versatile event-based approaches for the definition of novel information theory-based indices (IFIs) are presented. An event in this context is the criterion followed in the "discovery" of molecular substructures, which in turn serve as basis for the construction of the generalized incidence and relations frequency matrices, Q and F, respectively. From the resultant F, Shannon's, mutual, conditional and joint entropy-based IFIs are computed. In previous reports, an event named connected subgraphs was presented. The present study is an extension of this notion, in which we introduce other events, namely: terminal paths, vertex path incidence, quantum subgraphs, walks of length k, Sach's subgraphs, MACCs, E-state and substructure fingerprints and, finally, Ghose and Crippen atom-types for hydrophobicity and refractivity. Moreover, we define magnitude-based IFIs, introducing the use of the magnitude criterion in the definition of mutual, conditional and joint entropy-based IFIs. We also discuss the use of information-theoretic parameters as a measure of the dissimilarity of codified structural information of molecules. Finally, a comparison of the statistics for QSPR models obtained with the proposed IFIs and DRAGON's molecular descriptors for two physicochemical properties log P and log K of 34 derivatives of 2-furylethylenes demonstrates similar to better predictive ability than the latter.

Application of a Raney-cobalt-mediated tandem reductive cyclization protocol to total syntheses of the Aspidosperma alkaloids (±)-limaspermidine and (±)-1-acetylaspidoalbidine.

The racemic modification of the Aspidosperma alkaloid limaspermidine (1) has been prepared in ten steps including one involving a Raney-cobalt-mediated tandem reductive cyclization of nitrile 8 to give the tetracyclic system 9b. Compound (±)-1 has been converted over two steps into (±)-1-acetylaspidoalbidine [(±)-13].

Microwave-assisted synthesis of new N1,N4-substituted thiosemicarbazones.

We present an efficient procedure for the synthesis of thirty-six N1,N4-substituted thiosemicarbazones, including twenty-five ones that are reported for the first time, using a microwave-assisted methodology for the reaction of thiosemicarbazide intermediates with aldehydes in the presence of glacial acetic acid in ethanol and under solvent free conditions. Overall reaction times (20-40 min when ethanol as solvent, and 3 min under solvent free conditions) were much shorter than with the traditional procedure (480 min); satisfactory yields and high-purity compounds were obtained. The thiosemicarbazide intermediates were obtained from alkyl or aryl isothiocyanates and hydrazine hydrate or phenyl hydrazine by stirring at room temperature for 60 min or by microwave irradiation for 30 min, with lower yields for the latter. The preliminary in vitro antifungal activity of thiosemicarbazones was evaluated against Aspergillus parasiticus and Candida albicans.

Synthesis of porphyrin-dendrimers with a pyrene in the periphery and their cubic nonlinear optical properties.

Dendrons of pyrene derivatives were attached to a porphyrin core. A marked effect in solution for the dendrimers was observed in the absorption spectra. All the compounds obtained were characterized by (1)H-, (13)C-NMR, FTIR, UV-vis, MALDI-TOF or FAB+ mass spectrometry and elemental analysis. The cubic nonlinear optical behavior of some the synthesized compounds was tested via Z-Scan measurements in spin-coated film samples.

Synthesis of new pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) cyanosilylated derivatives using sulphated zirconia and hydrotalcite as catalysts in microwave-assisted reactions under solvent free conditions.

A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered.

Synthesis and characterization of poly-O-methyl-[n]-polyurethane from a d-glucamine-based monomer.

Aminoalditol 1-amino-1-deoxy-D-sorbitol (1) was readily converted into 2,3,4,5-tetra-O-methyl derivative 5, a key precursor of a sugar-based [n]-polyurethane. For the polymerization, the free amino or primary hydroxyl groups of 5 were selectively activated and employed as starting monomers in two alternative procedures. Thus, the amino function of 5 was converted into the isocyanate derivative by treatment with di-tert-butyltricarbonate, and polymerized in situ in the presence of Zr(IV) acetylacetonate. The resulting poly(1-amino-1-deoxy-2,3,4,5-tetra-O-methyl-D-sorbitol)urethane (8) had a moderate molecular weight and showed the presence of urea units. The alternative synthesis of 8 involved the activation of the free hydroxyl group of 5 as the corresponding phenylcarbonate. The polymerization of this α-amino-ω-phenylcarbonate alditol monomer does not require a metal catalyst. The resulting material exhibited an improved molecular weight and higher purity than that obtained via the isocyanate. [n]-polyurethane 8 was highly soluble in water as well as in common organic solvents (chloroform, acetone, ethyl acetate, etc) and was obtained as an amorphous material which was characterized thermally and spectroscopically.

A facile microwave-assisted Diels-Alder reaction of vinylboronates.

The Diels-Alder reaction of vinylboronates can be easily performed using microwave irradiation giving excellent yields of the cycloadducts. Pinacol vinylboronate was the reagent of choice due to its stability towards hydrolysis, operational simplicity and yields of Diels-Alder products. To the best of our knowledge, this is the first example of microwave-assisted Diels-Alder reaction of boron-substituted dienophiles. Subsequent in situ oxidation of the cycloadducts with alkaline hydrogen peroxide afforded the alcohols efficiently.

Efficient alkene synthesis on solid support using the Julia-Kocienski coupling.

An efficient application of the Julia-Kocienski coupling for the olefination of aldehydes with resin-bound benzothiazol-2-yl and 1-phenyl-1H-tetrazol-5-yl sulfones is described. Olefins is generally obtained in high overall yield for the six-reaction steps.

A suitable preparation of N-sulfonyl-1,2,3,4-tetrahydroisoquinolines and their ring homologs with a reusable Preyssler heteropolyacid as catalyst.

The preparation of N-sulfonyl-1,2,3,4-tetrahydroisoquinolines, N-sulfonyl-2,3,4,5-tetrahydro-1H-2-benzazepines and N-sulfonyl-1,2,3,4,5,6-hexahydrobenzazocine was catalyzed by a Preyssler heteropolyacid, H(14)[NaP(5)W(30)O(110)], (PA), supported on silica (PASiO(2)40) with excellent yields by means of the Pictet-Spengler reaction of N-aralkylsulfonamides with s-trioxane. The reactions proceed with 0.5 mol% of silica-supported catalyst in toluene at 70°C. The catalyst can be recycled without appreciable loss of the catalytic activity.

Protecting groups transfer: unusual method of removal of tr and tbdms groups by transetherification.

The triphenylmethyl (Tr) group undergoes a transfer (transetherification or disproportionation) between the molecules of 5'-O-Tr-2'-deoxynucleosides in a process mediated by anhydrous sulfates of Cu(+2), Fe(+2), or Ni(+2) to yield mixtures of 3',5'-bis-O-Tr and 3'-O-Tr products. If phenylmethanol is present in a reaction medium, detritylation results with concomitant formation of phenylmethyl triphenylmethyl ether. The behavior of t-butyldimethylsilyl (TBDMS) group in 5'-O-TBDMS-2'-deoxynucleosides is exactly the same. Such type of transetherifications was not observed before for the O-Tr and O-TBDMS groups.

Intrinsic gas-phase reactivity of ionized 6-(oxomethylene)cyclohexa-2,4-dienone: evidence pointing to its neutral alpha-oxoketene counterpart as a proper precursor of various benzopyran-4-ones and analogues.

Despite its unique structure and potential use as an important building block in organic synthesis, the title alpha-oxoketene 1 has been formed mostly under very special conditions as a short-lived species. The reactivity of 1 is, therefore, nearly unexplored. In great contrast, it seemed that its ionized gaseous form 1*+ is stable and easily accessible. In this study, we used multiple-stage pentaquadrupole mass spectrometry to probe the formation of gaseous 1*+ and explore its stability and intrinsic reactivity. With water and methanol, gaseous 1*+ was found to react similarly to solvated 1, which indicates that there is a close parallel between their reactivities. Gaseous 1*+ was also found to react promptly via polar [3 + 2] cycloadditons with various dienophiles including alkenes, alkynes, isocyanates, ketones and esters, thus forming a series of benzopyran-4-ones (flavones, 4-chromanones, 4-chromenones, benzo[1,3]dioxin-4-ones, and analogues) that are common structural units in many natural products. The present availability of 1 at room temperature and the gas-phase findings reported herein for gaseous 1*+ indicate that solvated 1 should undergo many [4 + 2] cycloadditions and functions as a versatile precursor of a variety of biologically active molecules.

Algorithm for exhaustive and nonredundant organic stereoisomer generation.

Generation of organic stereoisomers with R/S, Z/E, and/or M/P configurations that may contain heteroatoms, multiple bonds, and any kind of cycle (isolated, spiro, condensed, and nested) is described. Inputs for processing are molecular structures in a N_tuple format resident on an automatic (canonical) or manual (non canonical) generated file which are processed by doing internal molecular graph construction, a weighted bipartite tree construction for all atoms and bonds to detect stereocenters, and symmetrical atom groups (SAG) with some specific SAG parameters that constitute a novel way for redundancy elimination of meso structures. Finally, determination of ligand CIP priorities allows for writing the output N_tuples with stereoisomer description. Several examples showing application of this methology to a wide number of structures are also presented.

Regiospecific synthesis of 4-alkoxy and 4-amino substituted 2-trifluoromethyl pyrroles.

A simple and regiospecific synthesis of 4-alkoxy(amino)-2-trifluoromethyl pyrroles from 5-azido-4-alkoxy(amino)-1,1,1-trifluoro-pent-3-en-2-ones by an aza-Wittig cyclization of aminophosphoranes is described. The structures of the pyrroles and their synthetic intermediates were supported by NMR and HRMS analysis.