New Application of the Mitsunobu Reaction for the Preparation of (Δ-2) Derivatives in Terpenic Series

Application of the Mitsunobu reaction to various 3β-(equatorial)-hydroxy-4,4-dimethyl terpenic compounds provides the 2-ene-derivatives in good yields. A discussion about the mechanisms involved, and full details on the modified experimental protocol are given.     

2D NMR analysis of highly restricted internal rotation in 2-methylthio-3H-4-p-bromophenyl)-7-[(ortho- and para-substituted)-phenylthio]-1, 5-benzodiazepines

The complete assignments of twelve 4-aryl-7-thioaryl-1,5-benzodiazepines 1H and 13C spectra, performed with the use of high resolution variable solvent and temperature 1D and 2D techniques (e.g. HOMOCOSY, NOESY, HMQC and HMBC), lead to the determination of conformational equilibria between two rotamers having the aromatic ring of the thioaryl oriented in a perpendicular or helical orientation toward the benzodiazepine ring. The restricted rotation was evaluated from the population of these conformers.     

Surface‐enhanced Raman spectra of dimethoate and omethoate

Surface‐enhanced Raman scattering (SERS) spectra are presented and analyzed for two important organophosphate pesticides, dimethoate (DMT) and omethoate (OMT). Very detailed SERS spectra were obtained by aggregated Ag hydrosols, both in aqueous suspension and dried on a glass substrate. The SERS and ordinary Raman spectra of DMT do not resemble each other, suggesting that a chemical reaction immediately occurs when DMT is adsorbed onto the metal surface. We propose that the reaction product is OMT, which is the oxygen analog of DMT, on the basis of the Raman and SERS spectra of OMT. Further support is derived from the calculated Raman spectra of DMT and OMT. Minor wavenumber and intensity differences that are observed between the SERS spectra of DMT reaction product and those of OMT could be related to different metal/adsorbate interaction modes. The results can be useful in the development of new analytical methods for the determination of pesticide residues in food. Copyright © 2010 John Wiley & Sons, Ltd.     

Inclusion complex of usnic acid with β-cyclodextrin: characterization and nanoencapsulation into liposomes

In this study β-cyclodextrin (β-CD) was used to improve usnic acid (UA) solubility and the inclusion complex (UA:β-CD) was incorporated into liposomes in order to produce a targeted drug delivery system for exploiting the antimycobacterial activity of UA. A phase-solubility assay of UA in β-CD at pH 7.4 was performed. An apparent stability constant of K_1:1 = 234.5 M^?1 and a complexation efficiency of 0.005 was calculated. In the presence of 16 mM of β-CD the solubility of UA (7.3 μg/mL) increased more than 5-fold. The UA:β-CD complex was prepared using the freeze-drying technique and characterized through infrared and ¹HNMR spectroscopy, X-ray diffraction and thermal analyses. The UA:β-CD inclusion complex presented IR spectral modifications when compared with UA and β-CD spectra. ¹HNMR spectrum of UA:β-CD inclusion complex showed significant chemical shifts in proton H5 located inside the cavity of β-CD (Δδ = 0.127 ppm), suggesting that phenyl ring moiety of UA would be expected to be included within the β-CD cavity, interacting with the H-5 proton. A change in UA from its crystalline to amorphous form was observed on X-ray, suggesting the formation of a drug inclusion complex. DSC analysis showed the disappearance of the UA fusion peak UA:βCD complex. No differences between the antimicrobial activity of free UA and UA:βCD were found, supporting the hypothesis that the complexation with cyclodextrin did not interfere with drug activity. Liposomes containing UA:βCD were prepared using hydration of a thin lipid film method with subsequent sonication. Formulations of liposomes containing UA:βCD exhibited a drug encapsulation efficiency of 99.5% and remained stable for four months in a suspension form. Interestingly, the encapsulation of UA:βCD into the liposomes resulted in a modulation of in vitro kinetics of release of UA. Indeed, liposomes containing UA:β-CD presented a more prolonged release profile of free usnic acid compared to usnic acid-loaded liposomes.     

Radial basis network analysis of color parameters to estimate lycopene content on tomato fruits

With the purpose of estimating the lycopene concentration in tomato food samples, in an non-destructive way, several types of linear models of color parameters have been tested using individual values of L*, a* and b* values, (a*/b*), (a * ²/b * ²) and chroma parameters from tomato juice and fresh tomato fruits obtained with two different apparatus (Minolta CR-200b triestimulus colorimeter and HunterLab LabScan XE). Lycopene concentrations of fresh tomato and tomato juice (used as an input) were analyzed by UV-Vis spectroscopy. For all linear methods applied, the best one to estimate the lycopene concentration in tomato was the L*, a* and b* values of tomato juice measured with Hunter colorimeters (adjusted correlation coefficient, and mean prediction error, MPE < 6.59%). Four different RBEF models were designed firstly using three color parameters (L*, a* and b*) designated as “Lab case”, and secondly individually by the (a*/b*), (a * ²/b * ²) and chroma parameters. The lycopene concentration estimations were carried out with the lowest MPE and highest values possible. In order to test the reliability of the non-linear models, external validation process was also performed. From the testing of the all non-linear models applied, the RBEF Lab case model was the best to estimate lycopene content from color parameters (L*, a* and b*) using Minolta or Hunter equipments (MPE lower than 0.009 and higher than 0.997). This was a simple non-destructive method for predicting lycopene concentration in tomato fruits and tomato juice, which was reproducible and accurate enough to substitute chemical extraction determinations, and may be a useful tool for tomato industry.     

Evidence for oxidative stress in the developing cerebellum of the rat after chronic mild carbon monoxide exposure (0.0025% in air)

Background  

The present study was designed to test the hypothesis that chronic very mild prenatal carbon monoxide (CO) exposure (25 parts per million) subverts the normal development of the rat cerebellar cortex. Studies at this chronic low CO exposure over the earliest periods of mammalian development have not been performed to date. Pregnant rats were exposed chronically to CO from gestational day E5 to E20. In the postnatal period, rat pups were grouped as follows: Group A: prenatal exposure to CO only; group B: prenatal exposure to CO then exposed to CO from postnatal day 5 (P5) to P20; group C: postnatal exposure only, from P5 to P20, and group D, controls (air without CO). At P20, immunocytochemical analyses of oxidative stress markers, and structural and functional proteins were assessed in the cerebellar cortex of the four groups. Quantitative real time PCR assays were performed for inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) nitric oxide synthases.     

Rational matrix approximation with a priori error bounds for non-symmetric matrix Riccati equations with analytic coefficients

In this paper the exact solution of the non-symmetric matrixRiccati equation with analytic coefficients is approximatedby a rational matrix function with a prefixed accuracy. Thisrational matrix function is locally defined as the exact solutionof a Riccati problem with matrix polynomial coefficients obtainedby truncation of the Taylor expansions of the matrix coefficientsof the original problem.     

Actions of Inverse Semigroups on Algebras

In this article we prove that if S is a faithfully projective R-algebra and H is a finite inverse semigroup acting on S as R-linear maps such that the fixed subring S ^H  = R, then any partial isomorphism between ideals of S which are generated by central idempotents can be obtained as restriction of an R-automorphism of S and there exists a finite subgroup of automorphisms G of S with S ^G  = R.     

High pressure phases of different tetraboranes

High pressure phases of boron hydrides B₄H₁₀, B₄H₈ and B₄H₆ and their stability against dissociation into H and smaller B–H units are reported. Structure predictions based on particle swarm optimization reveal that all the boron hydrides studied show a tendency to separate into smaller structural units at low pressure. Under high pressure, the three-dimensional network in all the stoichiometries selected seems to be the most favourable arrangement. A study of the dissociation of B₄H₁₀ reflects an affinity to dissociate into B₄H₈ and H₂ in all the studied pressure range. Nevertheless, B₄H₈ does not seem to segregate in the studied pressure range and B₄H₆ may dissociate at 150 GPa.     

A three-dimensional transient two-phase flow analysis with a density pertubation finite volume method

In this paper, we present the analysis of a full three dimensional transient two-phase flow with strong disequilibria. This analysis uses a finite volume scheme with a recently developed density perturbation method. The application test case is a three dimensional extension of a one-dimensional experiment on blowdown pipe. The results are stable with mesh refinements and show realistic three-dimensional effects.