Simultaneous determination of propranolol and pindolol by synchronous spectrofluorimetry

A completely automated method to determine the most common parameters in cured meat products is proposed. The approach to full automation is based on the coupling of a robotic station for development of preliminary operations (namely weighing of the sample, grinding, leaching, filtration and transport to the aspiration zone) and a continuous unsegmented manifold for derivatisation and spectrophotometric monitoring of the reaction coloured products. This assembly works in an unattended fashion thus eliminating the bottleneck produced by the determination of these parameters in routine laboratories. The good agreement between results obtained by the proposed method and those from conventional methods for target analytes confirms its excellent performance and usefulness.     

Spectroscopic Study of the Inclusion Complexes of Phenylbutazone and Oxyphenbutazone with Cyclodextrins in Polar Reaction Media

The formation of inclusion complexes of -, -, hydroxypropyl-- (HP--) and -cyclodextrins with phenylbutazone and oxyphenbutazone has been studied in aqueous buffer solution (pH 7.5 and 0.1 mol dm^-3 NaCl), dimethylsulfoxide, and 25, 50 and 75% dimethylsulfoxide/water mixtures. These complexation reactions have been followed by UV electronic absorption spectroscopy. In addition, 1D and 2D ¹H NMR spectra were recorded to obtain structural information about the inclusion complexes formed in solution; 136 binding constant values were determined at five different temperatures (288, 293, 298, 303 and 310 K) from the electronic absorption data and, from these H_binding and S_binding values were obtained. At the studied cyclodextrin and guest concentration ranges, 1 : 1 inclusion complexes were detected. Only in three cases were 1 : 2 complexes detected, those of phenylbutazone and oxyphenbutazone with -cyclodextrin in aqueous, and oxyphenbutazone with hydroxypropyl--cyclodextrin in 75% dimethylsulfoxide/water solutions.     

A highly diastereoselective synthesis of 4-octulose and 2-deoxy-4-octulose from a -fructose derivative

Bishydroxylation of methyl

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1 with osmium tetraoxide proceeded with extremed high diastereoselectivity to give only methyl

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2. Configurations of the new stereogenic centers (C-2,3) in 2 were determined by degradation of the C-5,6,7,8 fragment to the well-known methyl

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7. Transformation of 2 into the required

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10, was achieved by a methodology that implied, protection to 8, reduction of the ester group in 8 to a hydroxymethyl group in 9, and finally deprotection to the free

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10. On the other hand, epoxidation reaction on

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11 afforded only the corresponding 2,3-anhydro derivative 12 with configuration, as could be demonstrated by degradation to (S)-1,2,4-trimetoxybutane 16, which synthesis is reported herein.     

Space and time-resolved laser-induced breakdown spectroscopy using charge-coupled device detection

Space and time-resolved studies of laser induced plasmas in air at atmospheric pressure are presented. Photovoltaic solar cells have been used as samples. The second harmonic (532 nm) of a Nd : YAG laser at an irradiance of 18 x 10(12) W/cm(2) has been used. The precise focus of the beam allows a microanalysis at a 0.02 mm(2) surface area working in single-shot mode. The use of an intensified charge-coupled device (CCD) detector has allowed time-resolved studies in both imaging or spectroscopy modes. The two-dimensional capability of the CCD has enabled the study of atomic and ionic species distribution along the plume. Most data have been recorded using single-laser shot experiments. Spectral lines have been assigned to transitions in atomic components of the material under investigation in the neutral or ionic states of the corresponding atoms. Effects of delay in improving spectral resolution and some examples of spectral characterization of species as a function of its decay are shown.     

Synthesis of Enantiopure Primary Amines by Stereoselective Ring Opening of Chiral Octahydro-1,3-benzoxazines by Grignard and Organoaluminum Reagents

Chiral 1,3-perhydrobenzoxazines 1, 2, and 9-14, prepared by condensation of 8-(benzylamino)menthol with different aldehydes, react with alkylmagnesium bromides and trimethylaluminum leading to the open amino alcohols 3a-d, 4a-d, and 15-20 in excellent chemical yields and good to excellent diastereomeric excess. The sequential elimination of the menthol appendage by heating with P(2)O(5) and the benzyl group by hydrogenolysis lead to primary amines 7a-d, 8a-d, and 27-30 in excellent chemical yields and ee. The addition of the alkyl group from the Grignard derivatives and the methyl group from the trimethylaluminum occurs from opposite sides of the heterocycle, yielding the final primary amines with the same stereochemistry.     

Novel Cleavage of Propargylamines by Reaction with Organolithium Compounds

Treatment of secondary aliphatic 2-bromoallylamines with an excess of an organolithium compound led to saturated amines in which the organic group of the organolithium compound is incorporated at the alpha carbon. On the other hand, the successive reaction of the former amines with BuLi and t-BuLi between -80 degrees C and rt gave 1,3-diamines or hexahydropyrimidines depending on the reaction time. The formation of these unexpected products involves initial generation of lithium propargylamides, which subsequently undergo cleavage of the C propargylic-C acetylenic bond induced by the organolithium present in each case in the reaction medium. A mechanism which takes into account all the different reaction products has been proposed and additionally supported by successful trapping of dilithium acetylide.     

An Efficient and Simple Entry to N-Substituted beta-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines

Reaction of azaenolates of 2-alkyl-oxa(thia)zolines 6 with imidoyl chlorides 7 as electrophiles to furnish masked N-substituted beta-enamino acid derivatives 1-2 in 70-90% yield is described. Alternative routes are discussed. Compounds 1-2 generally appear in one tautomeric form, imino or enamino, depending on the nature of the imidoyl chloride. The configuration of the enamino moiety (Z) and the conformation (s-cis) of compounds 1-2 obtained were established by an NMR study and unequivocally set by nuclear Overhauser effect difference experiments. An X-ray structure of compound 1e is also reported, showing a strong intramolecular NH.N hydrogen bond. Ab initio calculations (HF/3-21G and HF/3-21+G) have been carried out on several representative examples (1e, 1p, and 1l) in an attempt to support and provide the correct geometry of these derivatives. Structural considerations among the possible isomers of compounds 1 are discussed. From these studies it was concluded that the theoretical calculations agree with the experimental results. In addition, a very simple one-pot procedure for the preparation of masked N-substituted alpha-alkylated beta-enamino acid derivatives 2 from 6, 7, and different alkyl halides (R(3)Y) is described.