New cup-shaped α-cyclodextrin derivatives and a study of their catalytic properties in oxidation reactions

A series of new α-cyclodextrin derivatives with a substituted propylene bridge attached to the 6-O's of the A,D-glucose units are reported. The compounds were prepared from the known 6^A,6^D-di-O-(prop-2-methylidene-1,3-dienyl)-hexadeca-O-benzyl-α-cyclodextrin, which was transformed into 6^A,6^D-di-O-(prop-2-methyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-aminomethyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-hydroxymethylidene-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-carboxy-1,3-dienyl)-α-cyclodextrin and 6^A,6^D-di-O-(prop-2-methoxycarbonyl-1,3-dienyl)-α-cyclodextrin. The new compounds were evaluated for their ability to affect amine and alcohol oxidations in the presence of hydrogen peroxide.     

Synthesis and Spectroscopic Characterization of New Lead(II) Thiosaccharinates. Molecular Structure of Bis(thiosaccharinato)tetrakis(pyridine)dilead(II) and Thiosaccharinato‐bis(1,10‐phenantroline)lead(II) Thiosaccharinate

Four new lead(II) thiosaccharinate complexes: [Pb(tsac)₂H₂O] (1) (tsac: thiosaccharinate anion), [Pb₂(tsac)₄(py)₄] (2) (py: pyridine), [Pb(tsac)(o‐phen)₂](tsac)·CH₃CN (3) (o‐phen: 1,10‐phenantroline), and [Pb(tsac)₂(bipy)] (4) (bipy: 2,2′‐bipyridine) were prepared. The infrared and electronic spectra as well as the thermal analysis of all the compounds were recorded and discussed. The thiosaccharinate anion acts in three different coordination forms, one of then reported for the first time. The crystal structures of complexes 2 and 3 have been determined by single crystal X‐ray diffractometry. In complex 2 , two monomeric moieties are joined together forming a symmetric bis‐μ‐sulphur bridged dimer by interaction of two lead(II) atoms through the exocyclic sulphur atoms of two thiosaccharinate ligands. The seven‐fold coordination sphere of each lead atom is completed by two pyridine nitrogen atoms and by another sulfur and two nitrogen atoms of the thiosaccharinate anions. In complex 3 , the lead(II) atom is coordinated by four nitrogen atoms of two 1,10‐phenantroline molecules and by the sulfur and nitrogen atoms of one thiosaccharinate ion. The second anion has an electrostatic interaction with the nucleus.     

A sensitive, rapid and specific determination of midazolam in human plasma and saliva by liquid chromatography/electrospray mass spectrometry

A rapid, sensitive and selective liquid chromatography/electrospray mass spectrometry (LC/ES-MS) method was developed for the quantitative determination of the anaesthetic benzodiazepine midazolam (MID) in human saliva and plasma from patients undergoing anesthesia procedures. Biological samples spiked with diazepam-d5, the internal standard, were extracted into diethyl ether. Compounds were separated on a Xterra RP18 column using a mobile phase of acetonitrile/formic acid 0.1% at a flow rate of 0.25 mL/min under a linear gradient. Column effluents were analyzed using MS with an ES source in the positive ionization mode. Calibration curves were linear in the concentration ranges of 1-250 and 0.2-25 ng/mL in plasma and saliva, respectively. The limits of detection were 0.5 ng/mL in plasma and 0.1 ng/mL in saliva, using a 0.5-mL sample volume. The recoveries of the spiked samples were above 65%. The method was applied to ten real samples from patients undergoing midazolam treatment.     

Solvent control on the selective, nonselective, and absent response of a partially substituted lower rim calix(4)arene derivative for soft metal cations (mercury(II) and silver(I)). Structural and thermodynamic studies

The solvent control on the ability of a partially substituted lower rim calix(4)arene derivative 5,11,17,23,tetra-tert-butyl[25,27-bis(hydroxy)-26,28-bis(ethylthioethoxy)]-calix(4)arene, 1 to host soft metal cations (Hg(II) and Ag(I)) is demonstrated through 1H NMR, electrochemical (conductance measurements), and thermodynamic characterization of the complexation process in a wide variety of solvents. Solvent-ligand interactions were assessed from 1H NMR measurements involving 1 and various solvents in CDCl3. Thus, the formation of a 1:1 1-CH3CN adduct is reported. As far as metal cations are concerned, depending on the medium their complexation with 1 was only observed for Hg(II) and Ag(I). Thus, in acetonitrile, 1 is more selective for Hg(II) relative to Ag(I) by a factor of 2.2 x 10(3). In methanol the selectivity is reversed to an extent that the affinity of 1 for Ag(I) is 1.4 x 10(3) higher than that for Hg(II). However, 1 is unable to recognize selectively these cations in N,N-dimethylformamide while in propylene carbonate the ability of 1 to interact with these cations is lost. An outstanding feature of thermodynamics emerges when an assessment is made of the ligand effect on the complexation of these cations and analogues calix(4)arene derivatives. Thus, in acetonitrile the thermodynamics of cation complexation by the hydrophilic cavity of a calix(4)arene containing mixed pendant groups is built up from thermodynamic data for the same process involving derivatives with common functionalities at the narrow rim. This is a unique example of the additive contribution of pendant arms in the field of thermodynamics of calixarene chemistry.     

Liquid chromatography and tandem mass spectrometry: a powerful approach for the sensitive and rapid multiclass determination of pesticides and transformation products in water

In this paper we will show the results of our research on the direct simultaneous determination of multi-class pesticides and transformation products with different polarities and acid-base properties by applying an on-line trace enrichment coupled to the chromatographic system supplied with electrospray interface (SPE-LC-MS/MS method). The specific chromatographic separation allows the correct determination of almost fifty compounds (37 pesticides and 10 transformation products) using very low sample volume and very little sample handling. Recoveries between 70-120% were obtained for all compounds in drinking and groundwater, meanwhile in surface water 44 compounds were correctly quantified. Relative standard deviations lower than 15% were obtained for all compounds. Even at the lowest concentration level tested (25 ng L(-1)) 40 compounds presented satisfactory recoveries and repeatability. The use of methanol as organic modifier and the increase of injection volume are also studied. The applicability of the developed method to a monitoring programme is demonstrated by applying it to the analysis of hundreds of samples.     

Deuterium spin probes of side-chain dynamics in proteins. 2. Spectral density mapping and identification of nanosecond time-scale side-chain motions

In the previous paper in this issue we have demonstrated that it is possible to measure the five different relaxation rates of a deuteron in (13)CH(2)D methyl groups of (13)C-labeled, fractionally deuterated proteins. The extensive set of data acquired in these experiments provides an opportunity to investigate side-chain dynamics in proteins at a level of detail that heretofore was not possible. The data, acquired on the B1 domain of peptostreptococcal protein L, include 16 (9) relaxation measurements at 4 (2) different magnetic field strengths, 25 degrees C (5 degrees C). These data are shown to be self-consistent and are analyzed using a spectral density mapping procedure which allows extraction of values of the spectral density function at a number of frequencies with no assumptions about the underlying dynamics. Dynamics data from 31 of 35 methyls in the protein for which data could be obtained were well-fitted using the two-parameter Lipari-Szabo model (Lipari, G.; Szabo, A. J. Am. Chem. Soc. 1982, 104, 4546). The data from the remaining 4 methyls can be fitted using a three-parameter version of the Lipari-Szabo model that takes into account, in a simple manner, additional nanosecond time-scale local dynamics. This interpretation is supported by analysis of a molecular dynamics trajectory where spectral density profiles calculated for side-chain methyl sites reflect the influence of slower (nanosecond) time-scale motions involving jumps between rotameric wells. A discussion of the minimum number of relaxation measurements that are necessary to extract the full complement of dynamics information is presented along with an interpretation of the extracted dynamics parameters.     

Poly[(μ3‐1,1‐dioxo‐1,2‐benzoisothiazole‐3‐thiolato‐κ3N:S3:S3)silver(I)]

The centrosymmetric title compound, [Ag(C₇H₄NO₂S₂)]_n, consists of dinuclear units in which two thiosaccharinate anions each bridge two Ag atoms via an endocyclic N atom and an exocyclic S atom across a crystallographic centre of inversion midway between the Ag atoms. The dimeric units are connected via Ag—S_exo interactions to create two‐dimensional networks. The thiosaccharinate anions bridge in a μ₃‐S:S:N manner. The Ag...Ag distance can be considered a strong argentophilic interaction.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

Salt Stress Proteins Identified by a Functional Approach in Yeast

We have performed functional genomics of salt stress by overexpression of gene libraries in yeast and selection for salt tolerance. Thirty halotolerance genes were isolated from yeast, Arabidopsis, and sugar beet. The results indicate that Na⁺ transport (uptake, efflux, and compartmentation), sulfate activation, RNA processing, and protein synthesis are crucial for salt tolerance.     

A pyrazine bis‐adduct of a binuclear rhodium(II) carboxylate containing 3,4,5‐triethoxybenzoate as the ­equatorial ligand

The title compound, tetrakis(μ‐3,4,5‐triethoxy­benzoato‐κ²O:O′)­bis­[(pyrazine‐κN)­rhodium(II)](Rh—Rh), [Rh₂(C₁₃H₁₇O₅)₄(C₄H₄N₂)₂], crystallizes on an inversion centre in the triclinic space group . The equatorial carboxyl­ate ligands bridge the two Rh^II atoms, giving a binuclear lantern‐like structure. The pyrazine mol­ecules occupy the two axial coordination sites. The phenyl rings are tilted by ca 10° with respect to the attached carboxyl­ate groups. The pyrazine planes have a torsion angle of ca 19° around the Rh—N bond with respect to the plane of the nearer carboxyl­ate group and are not coplanar with the Rh—Rh bond.